Effects of different curing concentrations and drying times on the microbial community structure and metabolites of dried Spanish mackerel

Cured Spanish mackerel has a promising market owing to its nutritious nature as well as ease of transportation and preservation. However, the nutritional and flavor formation mechanism of Spanish mackerel after curing and drying is unclear. To overcome this problem, the effects of different processing conditions on the free amino acid, microbial community, and flavor of Spanish mackerel were explored. Staphylococcus and Cobetia are the main microorganisms in cured mackerel and are closely associated with the formation of their quality. Compared with fresh mackerel, cured mackerel contains increased levels of protein, fat, and chloride, contributing to its distinctive flavor. The contents of free amino acids in the BA64 group were substantially higher than those in other groups, particularly the contents of threonine, glycine, and tyrosine. These findings will contribute to the development of high-quality cured Spanish mackerel products and cured aquatic products.

Insights into the potential mechanism of liquid nitrogen spray freezing's influence on volatile compounds in surimi gels with different cross-linking degrees: Focus on oxidation, protein structure, intermolecular force and free amino acid alterations

This study revealed the variations in odor characteristics and underlying mechanisms of different cross-linked surimi gels under liquid nitrogen (LN) spray freezing. The results demonstrated that LN spray freezing had an essential effect on the gels' odor. The odor changes in the -80 °C LN spray freezing group were closer to the control group, while -35 °C LN spray freezing treatment had the greatest impact on the aroma quality of gels. Freezing reduced gels' texture properties, intensified lipid and protein oxidation, altered protein conformation, increased surface hydrophobicity and hydrophobic interactions. These changes affected the gels' odor characteristics, leading to a reduction in fish aroma and an increase in fishy and oil odors after freezing. These tendencies were more pronounced at -35 °C LN spray freezing with lower cross-linking degrees, and reducing the freezing temperature to -80 °C and increasing the cross-linking degree to 62.99% mitigated the extent of deterioration in gel flavor quality.

Distinct changes of taste quality and metabolite profile in different tomato varieties revealed by LC-MS metabolomics

Breeding of tomato varieties based on phenotypic traits can potentially lead to a decline in taste and nutritional values, thereby impacting consumer acceptance. However, taste is an intrinsic characteristic of tomatoes. Its decoding requires the identification of crucial compounds and the associated metabolic pathways implicated in taste development and formation. In this study, the taste parameter differences of four tomato varieties were distinguished using an electronic tongue. The content of organic acids and free amino acids, which were closely associated with taste variations, was quantitatively analyzed. Several important taste metabolites and metabolic pathways were identified based on LC-MS metabolomics and enrichment analysis. Through correlation analysis, it was determined that there existed significant associations between the taste, compounds, and metabolites of tomato varieties with different phenotypes. This study could provide references and theoretical basis for tomato breeding, as well as the control and evaluation of taste and quality of tomato varieties.

The role of multiple vitellogenins in early development of fishes

Functions of vitellogenins have been in the limelight of fish reproductive physiology research for decades. The Vtg system of acanthomorph teleosts consists of two complete forms of Vtgs (VtgAa and VtgAb) and an incomplete form, VtgC. Insufficient uptake and processing of Vtgs and their yolk proteins lead to inadequate oocyte hydration ensuing failure in acquisition of egg buoyancy and early developmental deficiencies. This review presents a summary of our studies on utilization of multiple Vtgs in species with different egg buoyancy characteristics, as examples. Studies of moronids revealed limited degradation of all three forms of lipovitellin heavy chain derived from their three respective forms of Vtg, by which they contribute to the free amino acid pool driving oocyte hydration during oocyte maturation. In later studies, CRISPR/Cas9 was employed to invalidate zebrafish type I, type II and type III Vtgs, which are orthologs of acanthamorph VtgAa, VtgAb and VtgC, respectively. Results revealed type I Vtg to have essential developmental and nutritional functions in both late embryos and larvae. Genomic disturbance of type II Vtg led to high mortalities during the first 24 h of embryonic development. Despite being a minor form of Vtg in zebrafish and most other species, type III Vtg was also found to contribute essentially to the developmental potential of zebrafish zygotes and early embryos. Apart from severe effects on progeny survival, these studies also disclosed previously unreported regulatory effects of Vtgs on fecundity and fertility, and on embryo hatching. We recently utilized parallel reactions monitoring based liquid chromatography tandem mass spectrometry to assess the processing and utilization of lipovitellins derived from different forms of Vtg in Atlantic halibut and European plaice. Results showed the Lv heavy chain of VtgAa (LvHAa) to be consumed during oocyte maturation and the Lv light chain of VtgAb (LvLAb) to be utilized specifically during late larval stages, while all remaining YPs (LvLAa, LvHAb, LvHC, and LvLC) were utilized during or after hatching up until first feeding in halibut. In plaice, all YPs except LvHAa, which similarly to halibut supports oocyte maturation, are utilized from late embryo to late larval development up until first feeding. The collective findings from these studies affirm substantial disparity in modes of utilization of different types of Vtgs among fish species with various egg buoyancy characteristics, and they reveal previously unknown regulatory functions of Vtgs in maintenance of reproductive assets such as maternal fecundity and fertility, and in embryonic hatching. Despite the progress that has been made over the past two decades by examining multiple Vtgs and their functions, a higher complexity of these systems with much greater diversity between species in modes of Vtg utilization is now evident. Further research is needed to reveal novel ways each species has evolved to utilize these complex multiple Vtg systems and to discover unifying principles for this evolution in fishes of diverse lineages, habitats and life history characteristics.

"Exotic" seeds from Southern Africa as potential Novel Foods? - Chemical composition of manketti nuts (Schinziophyton rautanenii) and ushivi beans (Guibourtia coleosperma)

Various species of Southern African plants and their edible seeds have gained huge importance due to positive health aspects, and there is increasing interest to introduce such seeds as Novel Food on the international market. Especially the seeds of Schinziophyton rautanenii (manketti) and Guibourtia coleosperma (ushivi) could have great potential as a food and food ingredient. Hence, extensive analyses on the chemical composition of manketti nuts and ushivi beans including the analysis of total solids, protein and fat content, soluble carbohydrates, ash, total and free amino acids, biogenic amines and polyamines, fatty acid profile as well as the content of certain B-vitamins and tocopherols were performed. Results obtained showed a valuable nutritional composition, e.g., a true protein content of 22.6% with a ratio of essential amino acids to total amino acid composition of 48% in manketti nuts, while ushivi beans had a true protein content of 8.2% with a similar ratio of essential to total amino acids (45%). Lipid content was 54.1% in manketti nuts, ushivi beans had a value of 7.7%. In both, linoleic acid was the most abundant. Furthermore, ushivi beans had high amounts of vitamin B1 and B2.

Inoculation of Yarrowia lipolytica promotes the growth of lactic acid bacteria, Debaryomyces udenii and the formation of ethyl esters in sour meat

Yarrowia lipolytica N12 and A13 with high lipase activity obtained by mutagenesis were inoculated into sour meat, and their effects on physicochemical properties, microbial community succession, free amino acids, and volatile compounds of sour meat were investigated. Inoculation fermentation increased the contents of free amino acids observably, rapidly reduced pH, promoted the accumulation of total acids, decreased 2-thiobarbituric acid reactive substances (TBARS) values. In addition, the addition of Y. lipolytica might contribute to the growth of lactic acid bacteria, Candida spp., and Debaryomyces udenii, which play an important role in production of volatile compounds. It was shown that inoculation promoted the production of esters, aldehydes, and alcohols, especially ethyl esters, giving sour meat a better meat flavor. Besides, it was found that Y. lipolytica A13 had better fermenting property. Sample of A13 group had higher contents of ethyl esters, free amino acids and dominant microorganisms. The results may help to provide new strains for sour meat fermentation.

Comparison of microbial diversity and metabolites on household and commercial doenjang

In this study, the microbial diversity, free amino acid (FAA), and biological activities of household doenjang (HDJ) from four different regions and commercial doenjang (CDJ) four manufacturers were analyzed. And volatile flavor compound (VFC) and isoflavone profiles were analyzed using gas chromatograph-mass spectrometer (GC-MS) and high performance liquid chromatography (HPLC), respectively. The major bacterial genus in 1HDJ and 2HDJ was Bacillus (97.5%), while in 3HDJ and 4HDJ, it was Enterobacter (47.5%) and Pseudomonas (80%), respectively. Tetragenococcus was the main bacterial genus of CDJ. The Zygosaccharomyces genus among yeast was comparatively high in all samples. In all samples, glutamic acid predominated among the FAAs, and the 3-methyl butanal, benzeneacetaldehyde, and diallyl disulphide were major VFCs. CDJ contained higher levels of isoflavone-glycoside and total phenolics. Except for 3HDJ and 4CDJ, the isoflavone-aglycone and total flavonoid contents were higher in HDJ. The correlation between bacterial genus and metabolited of doenjang showed that Tetragenococcus was closely related to glutamic acid, Bacillus was related to aglycones and ammonia, and Pseudomonas was highly related to isovaleric acid. While, correlation between yeast genus and metabolited of doenjang confirmed that Candida, Hanseniaspora, and Saccharomyces were related with furfural, benzeneacetaldehyde, and 3-methyl butanal, respectively. The results of this study can be utilized as basic data for the industrialization and development of doenjang.

Comparison of amino acid release between enzymatic hydrolysis and acid autolysis of rainbow trout viscera

Fish protein hydrolysates were obtained from cultured rainbow trout (Oncorhynchus mykiss) viscera using commercial and endogenous enzymes. Two methods were employed for hydrolysis: acid autolysis (also known as silage) at room temperature for 10 days in acidic conditions, until total solubilisation, and enzymatic hydrolysis using Alcalase 2.4 LFG, Protana Prime, and the endogenous enzymes in the viscera. The effectiveness of both methods in releasing free amino acids (FAA) was assessed. After evaluating the results, the most effective enzymatic hydrolysis was optimized. The findings indicated that enzymatic hydrolysis with Alcalase, Protana Prime and endogenous enzymes combined for 7 h at a dose of 1% of protein, and a 7-day acid autolysis yielded the highest degree of hydrolysis (83.8% and 75.8%), a yield of FAA from viscera of 5.9% and 3.2%, and a yield of FAA from total protein of 71.3% and 52.5%, respectively. In conclusion, the use of commercial enzymes was more efficient in releasing amino acids, but endogenous enzymes showed a strong proteolytic capacity during acid autolysis, suggesting it also as a promising method to produce FAA-rich hydrolysates.

TMT-labeled quantitative proteomic reveals the mechanism of proteolysis and taste improvement of dry-cured bacon with Staphylococcus co-inoculation

To understand the mechanism of co-inoculation of Staphylococcus xylosus and Staphylococcus vitulinus (SX & SV) on structural protein degradation and taste enhancement of dry-cured bacon, protease activities, protein degradation, surface morphology of proteins and taste parameters of dry-cured bacon with Staphylococcus inoculation were investigated. The dry-cured bacon with co-inoculation of Staphylococcus xylosus and Staphylococcus vitulinus showed the best taste attributes. High residual activities in cathepsin B + L (more than 1.6-fold) and alanyl aminopeptidase (more than 1.4-fold) accelerated structural protein degradation in SX & SV. 32 down-regulated proteins were identified in SX & SV by TMT-labeled quantitative proteomic compared with control group; myosin and actin showed the most intense response to the accumulation of sweet and umami amino acids, and atomic force microscopy confirmed structural proteins breakdown by morphological changes. The accumulation of glutamic acid, alanine and lysine was mainly responsible for taste improvement of dry-cured bacon with Staphylococcus co-inoculation.

Can lettuce plants grow in saline soils supplemented with biochar?

Salt stress is presently a major environmental concern, given the huge number of soils affected by the presence of dissolved salts. Therefore, it is necessary to find solutions, preferably nature-based ones, to deal with this problem. In this study, biochar, a product made from plant biomass residues through the process of pyrolysis, was tested to alleviate salt stress on lettuce (Lactuca sativa L.) plants. Six different concentrations of NaCl were tested: 0, 50, 100, 200, 300 and 400 mM with and without the addition of 5% (w/w) biochar. Biochar ability to mitigate salinity damage was assessed by means of both biometric (fresh weight), physiological (chlorophyll content), and biochemical (i.e., electrolyte leakage, total antioxidant power, total soluble proteins, free amino acids, and mineral content) parameters. The experiment lasted four weeks. The results showed that NaCl has a negative effect from the concentration of 100-200 mM and that biochar was to some extent effective in mitigating the negative effects of salt on plant physiology; nevertheless, biochar failed to counteract Na accumulation. Similarly, biochar did not influence the content of free amino acids in lettuce leaves, but enhanced the expression of several parameters, such as total antioxidant power, fresh weight, chlorophyll content, total soluble protein, K content, although only clearly evident in some cases. Overall, the present study showed that biochar is a viable solution to counteract the damage caused by high salt concentrations on plant growth.

The influence of substituting dietary peptide-bound with free amino acids on nitrogen metabolism and acid-base balance of broiler chickens depends on asparagine and glutamine supply

Reducing dietary crude protein (CP) concentration while maintaining adequate amino acid (AA) supply by free AA inclusion can contribute to attenuate the negative environmental effects of animal farming. This study investigated upper limits of dietary free AA inclusions without undesirable effects including the dependence on asparagine (Asn) and glutamine (Gln) supply. Ten broilers were allocated to sixty-three metabolism units each and offered nine experimental diets from day (d) 7-21 (n 7). One diet (167 g CP/kg) contained 80 g soya protein isolate (SPI)/kg. In the other diets, 25, 50, 75 and 100 % of the digestible AA from SPI were substituted with free AA. Digestible Asn+aspartic acid (Asp) and Gln+glutamic acid (Glu) were substituted with Asp/Glu or 50/50 mixes of Asp/Asn and Glu/Gln, respectively. Total excreta were collected from d 11-14 and from d 18-21. Growth and nitrogen accretion were unaffected by 25 and 50 % substitution without and with free Asn/Gln, respectively, but decreased at higher substitution (P ≤ 0·024). Circulating concentrations of Asp, Glu and Gln were unaffected by treatment, while Asn decreased at substitution higher than 50 % when Asn/Gln were not provided (P ≤ 0·005). Blood gas analysis on d 21 indicated a compensated metabolic acidosis at substitution higher than 50 and 75 % without and with free Asn/Gln, respectively (P ≤ 0·017). Results suggest that adding Asn/Gln increased an upper limit for proportion of dietary free AA from 10 to 19 % of dietary CP and enabled higher free AA inclusion without affecting the acid-base balance.

Comparison of freezing and heating treatment sequence on biochemical properties and flavor of swimming crabs (Portunus Trituberculatus) meat during freeze-thaw cycles

The objective of this study was to compare the effect of freezing and heating treatment sequences on the biochemical properties and flavor of crab (Portunus trituberculatus) meat during freeze-thaw cycles. The results showed that pH, color, K and microstructure changes in the H-F group were not significant with increasing number of freeze-thaw cycles, but TVB-N values increased and WHC values decreased. However, with the increase in the number of freeze-thaw cycles, pH and WHC significantly decreased and TVB-N, L* and K values significantly increased in the C and F-H groups. Proteins were degraded in all groups, but the lower degree of degradation occurred in the H-F group. Although the total free amino acid content decreased with increasing number of freeze-thaw cycles in each group, the high content of AMP and IMP in the H-F group suggested that it still had a better flavor.

Enantioselective Fluorescence Recognition of Free α-Amino Acids by Ion-Type Ammonium Salt-Based Sensors

Optically pure amino acids have extensive applications in pharmaceuticals, pesticides, food, materials, and other fields. Enantiomers recognition of chiral amino acids using optical methods with synthetic chiral sensors has attracted extensive attention. Most reported sensors typically identify guests by covalent or hydrogen bonding or hydrophobic interaction with amino acids and their derivatives. In this paper, a series of ion-type quaternary ammonium salt-based enantioselective fluorescent sensors were synthesized for chiral recognition of free α-amino acids via electrostatic interaction. The fluorescence intensity ratios ID/IL (ID, IL, fluorescence intensity of sensor when treated with D- or L-amino acid) were up to 2.1 and enantioselective fluorescence enhancement ratios ef (ef=[IL-I0]/[ID-I0] or [ID-I0]/[IL-I0]. (I0, fluorescence intensity of the sensor)) were up to 5.0. Among them, sensor 3 showed best enantioselective recognition performance toward tryptophan (Trp), and L-Trp significantly quenched the fluorescence of sensor 3, but D-Trp greatly enhanced the fluorescence of sensor 3, its ID/IL was 2.11 and ef was 1.8. The mechanistic investigation by NMR spectrum revealed that a tight three-point interaction, including electrostatic interaction, hydrogen bond, and π-π stacking, between sensor 3 and D-Trp was formed.

Recent innovations in fertilization with treated digestate from food waste to recover nutrients for arid agricultural fields

This study aims to explore the development of sustainable fertilizers from waste materials of a biogas plant and a brewery. These wastes, rich in organic carbon and nitrogen, were processed with sulfuric(VI) and phosphoric(V) acid mixture, facilitating the production of free amino acids and achieving waste sanitization. This treatment produced by-products, which extended the range of possible applications. The highest concentration of free amino acids (360 mg/l) was achieved through hydrolyzing with a 40% concentration medium over 24 h. In this case, the maximum levels were recorded for beta-alanine (69.3 mg/l), glycine (46.8 mg/l), isoleucine (43.5 mg/l), proline (36.2 mg/l), and valine (31.5 mg/l). The study presents two fertilizer technologies, with and without micronutrients, that satisfy European Parliament Regulation 2019/1009 (Ntot > 2%, Norg > 0.5%, Corg > 3%). Bioavailability of nutrients in the formulations ranged from 60 to 100%. The efficacies of these fertilizers were evaluated in 30-day pot trials with various plant species, with both single application and fertigation tested. Multielement analysis confirmed high nutrient transfer in the soil-plant system, and the inclusion of micronutrients led to biofortification of plant biomass in Cu (48.3 ± 7.2 mg/kg), Mn (249 ± 37 mg/kg), Zn (164 ± 25 mg/kg), and Fe (211 ± 32 mg/kg). These sustainable fertilizers present an alternative to traditional, non-renewable fertilizers and offer promising solutions for precision agriculture and environmentally conscious production.

Microbial community succession and its correlation with the dynamics of flavor compound profiles in naturally fermented stinky sufu

Wuhan stinky sufu is a traditional fermented soybean product with a short ripening period and unique flavor. The aim of this study was to explore the characteristic flavor compounds and core functional microbiota of naturally fermented Wuhan stinky sufu. The results indicated that 11 volatile compounds including guaiacol, 2-pentylfuran, dimethyl trisulfide, dimethyl disulfide, acetoin, 1-octen-3-ol, (2E)-2-nonenal, indole, propyl 2-methylbutyrate, ethyl 4-methylvalerate, nonanal were characteristic aroma compounds, and 6 free amino acids (Ser, Lys, Arg, Glu, Met and Pro) were identified as taste-contributing compounds. 4 fungal genera (Kodamaea, unclassified_Dipodascaceae, Geotrichum, Trichosporon), and 9 bacterial genera (Lysinibacillus, Enterococcus, Acidipropionibacterium, Bifidobacterium, Corynebacterium, Lactococcus, Pseudomonas, Enterobacter, and Acinetobacter) were identified as the core functional microbiota with positive effects on the production of flavor compounds. These findings would enhance the understanding of core flavor-producing microorganisms in naturally fermented soybean products and potentially provide guidance for enhancing the quality of sufu.

Autophagy contributes to increase the content of intracellular free amino acids in hard clam (Mercenaria mercenaria) during prolonged exposure to hypersaline environments

Marine bivalves in intertidal zones and land-based seawater ponds are constantly subjected to a wide range of salinity fluctuations due to heavy rainfall, intense drought, and human activities. As osmoconformers, bivalves rely primarily on rapid release or accumulation of free amino acids (FAAs) for osmoregulation. Euryhaline bivalves are capable of withstanding hyposaline and hypersaline environments through regulation of physiology, metabolism, and gene expression. However, current understanding of the molecular mechanisms underlying osmoregulation and salinity adaptation in euryhaline bivalves remains largely limited. In this study, RNA-seq, WGCNA and flow cytometric analysis were performed to investigate the physiological responses of hard clams (Mercenaria mercenaria) to acute short-term hyposalinity (AL) and hypersalinity (AH), and chronic long-term hyposalinity (CL) and hypersalinity (CH) stress. We found that amino acids biosynthesis was significantly inhibited and aminoacyl-tRNA biosynthesis was augmented to decrease intracellular osmolarity during hyposaline exposure. Under CH, numerous autophagy-related genes (ATGs) were highly expressed, and the autophagy activity of gill cells were significantly up-regulated. A significant decrease in total FAAs content was observed in gills after NH4Cl treatment, indicating that autophagy was crucial for osmoregulation in hard clams during prolonged exposure to hypersaline environments. To prevent premature or unnecessary apoptosis, the expression of cathepsin L was inhibited under AL and AH, and inhibitors of apoptosis was augmented under CL and CH. Additionally, neuroendocrine regulation was involved in salinity adaption in hard clams. This study provides novel insights into the physiological responses of euryhaline marine bivalves to hyposaline and hypersaline environments.

Effects of electromagnetic roller-hot-air-steam triple-coupled fixation on reducing the bitterness and astringency and improving the flavor quality of green tea

Despite the importance of fixation in determining green tea quality, its role in reducing the bitter and astringent taste of this beverage remains largely unknown. Herein, an electromagnetic roller-hot-air-steam triple-coupled fixation (ERHSF) device was developed, and its operating parameters were optimized (steam volume: 20 kg/h; hot-air temperature: 90 °C; hot-air blower speed: 1200 r/min). Compared with conventional fixation treated samples, the ratio of tea polyphenols to free amino acids and ester-catechins to simple-catechins in ERHSF-treated samples was reduced by 11.0% and 3.2%, reducing bitterness and astringency of green tea; amino acids, soluble sugars, and chlorophyll contents were significantly increased, enhancing the freshness, sweetness, and greenness; the color indexes, such as L/L* value of brightness and -a/-a* value of greenness, were also improved, and ERHSF-treated samples had the highest sensory scores. These results provided theoretical support and technical guidance for precise quality improvement of summer-autumn green tea.

Free amino acids in response to salinity changes in fishes: relationships to osmoregulation

Free amino acids (FAAs) are believed to play important roles in osmoregulation and buffer capacity in some aquatic animals, such as fishes. However, the potential roles of FAAs have not been systematically summarized and characterized until now. In the present study, the meta-analysis was conducted to investigate the relationships between FAAs and environmental salinities. Twenty published documents were included, accounting for 106 study cases. The effect sizes of total free amino acids (TFAAs), total essential amino acids (TEAAs), and total non-essential amino acids (TNEAAs) to salinity increase were calculated and determined by the restricted maximum likelihood (REML) method. It clearly showed that the elevated salinities significantly induced the contents of TFAAs, TEAAs, and TNEAAs at the ratio of 36%, 27%, and 29%, respectively. Faced to the salinity changes, the contents of FAAs in fishes under freshwater and seawater varied significantly, while the individuals under brackish water displayed relatively constant contents of FAAs. When salinity elevated, the contents of 17 amino acids in muscles significantly increased, suggesting the important roles of FAA metabolism in osmoregulation in fishes. The results also indicated that the effect sizes of TFAAs were positively related to the rates of salinity increases, and exhibited a significant quadratic linear relationship with temperatures. Additionally, the contents of FAAs also showed positive correlation with osmotic pressure, concentrations of plasma Na+, Cl-, and urea, implying their potential roles of FAAs in osmoregulation in fishes. These findings suggested that elevated salinities greatly induced the contents of FAAs in fishes, making a great contribution to maintaining the homeostasis of fishes in response to environmental salinity changes.

High-speed cold centrifugation of milk modifies the microbiota, the ripening process and the sensory characteristics of raw-milk hard cheeses

The microbial population of raw milk plays a crucial role in the development of distinctive traits of raw-milk cheeses particularly appreciated by consumers. It was previously demonstrated that the microbial population of raw milk is modified by a high-speed centrifugation (also called bactofugation) conducted at 39 °C. The aim of the present study was to evaluate the effects of this process, performed once or twice, on the microbial, compositional, biochemical, and sensory characteristics of the derived hard cheeses. Experimental and control cheesemaking were conducted in parallel at a cheese factory during a 13-month period. Cheeses were analysed after 9, 15 and 20 months of ripening for microbial count, composition, proteolysis extent, volatile compounds, and sensory profile. Results evidenced that experimental cheeses were characterized by lower numbers of viable lactobacilli respect to control. Experimental cheeses also showed differences in the progress of primary and secondary proteolysis which, in turn, caused different patterns of free amino acids at all ripening times. Experimental cheeses had significantly lower content of esters and were differentiated from control for some traits by assessors. In conclusion, use of high-speed centrifugation of milk shall be discouraged if characteristic traits of raw-milk cheeses, particularly PDO cheeses, want to be retained.

Properties investigations of rape stalks fermented by different salt concentration: Effect of volatile compounds and physicochemical indexes

In order to find out the effect of salt concentration on fermented rape stalks, the physicochemical quality and volatile components was investigated using high performance liquid chromatography (HPLC) and headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that there were abundant kinds of free amino acids (FAAs) in all samples, mainly presenting sweet, umami and bitter taste. Through taste activity value (TAV), His, Glu, and Ala contributed significantly to the taste of the sample. 51 volatile components were identified, of which the relative contents of ketones and alcohols were high. By the relative odor activity value (ROAV) analysis, the main components that had a great impact on the flavor were phenylacetaldehyde, β-Ionone, ethyl palmitate and furanone. Adjusting the appropriate salt concentration for fermentation could improve the comprehensive quality of fermented rape stalks and promote the development and utilization of rape products.

A comparative study on the taste quality of Mytilus coruscus under different shucking treatments

Shucking is an indispensable step in the preparation of cooked mussel products, as it facilitates the detachment of meat from the shell. In this study, we comprehensively investigated the effects of boiling, steaming, and microwaving on taste constituents in half-cooked mussel meat. Two-dimensional correlation spectroscopy revealed the key differential taste components of the different shucking groups. Structural equation modeling (SEM) indicated the positive effects of saltiness and bitterness on umami taste, while sweetness and sourness had negative effects on umami taste in half-cooked mussel meat. Furthermore, Glu, Asp, Ala, Arg, betaine, malic acid, succinic acid, glycogen, Cl^-, Na⁺, K⁺, and PO3- 4 were quantitatively determined as the main taste compounds. The steaming shelling group had the most enriched taste components, with the highest equivalent umami concentration compared to the other shelling groups. Hence, steaming shucking may be favored due to abundant tastes and nutrients.

Establishing the relations of characteristic aroma precursors and volatile compounds for authenticating Tibetan pork

Tibetan pork has been favored for its unique aromas, which originate from chemical reactions between characteristic precursors in cooking. The precursors (e.g., fatty acids, free amino acids, reducing sugars, and thiamine) of Tibetan pork ((semi-) free range) from different regions in China, comprising Tibet, Sichuan, Qinghai, and Yunnan, and commercial pork (indoor reared) were compared in this study. Tibetan pork was characterized by higher ω-3 polyunsaturated fatty acids (i.e., C18:3n3), higher essential (i.e., valine, leucine, and isoleucine), aromatic (i.e., phenylalanine), and sulfur-containing (i.e., methionine and cysteine) free amino acids, higher thiamine, and lower reducing sugars. Boiled Tibetan pork exhibited higher heptanal, 4-heptenal, and 4-pentylbenzaldehyde compared with commercial pork. The results from multivariate statistical analysis revealed that precursors combined with volatiles exhibited discriminating capability for characterizing Tibetan pork. The precursors in Tibetan pork exerted a certain effect on characteristic aroma generation, probably arising from promoting chemical reactions in cooking.

Indirect regeneration in Ficus lyrata Warb. and metabolite profiles influenced by nitric oxide and Plant growth regulators

BACKGROUND

To establish an indirect regeneration protocol in Ficus lyrata, a three-phase experiment (callus induction, morphogenic callus induction, and plant regeneration) based on auxin, cytokinin, and nitric oxide interactions was designed and implemented using leaf explants. The metabolite profiles (amino acid profile, total phenolic content, total soluble sugars, and total antioxidant activity) alteration patterns were also investigated to determine the metabolites contributing to the progress of each phase.

RESULTS

Results demonstrated that 11 out of 48 implemented treatments resulted in morphogenic callus induction (morphogenic treatments), and nitric oxide played a key role in increasing efficiency from 13 to 100%. More importantly, nitric oxide cross-talk with cytokinins was necessary for shoot regeneration from morphogenic calli. Only 4 out of all 48 implemented treatments were capable of shoot regeneration (regenerative treatments), and among them, PR42 treatment led to the highest shoot regeneration rate (86%) and maximum mean number of shoot/explant (10.46). Metabolite analyses revealed that the morphogenic and regenerative treatments followed similar metabolite alterations, which were associated with increased biosynthesis of arginine, lysine, methionine, asparagine, glutamine, histidine, threonine, leucine, glycine, serine amino acids, total soluble sugars content, and total antioxidant activity. On the contrary, non-morphogenic and non-regenerative treatments caused the accumulation of a significantly greater total phenolic content and malondialdehyde in the explant cells, which reflexed the stressful condition of the explants.

CONCLUSIONS

It could be concluded that the proper interactions of auxin, cytokinins, and nitric oxide could result in metabolite biosynthesis alterations, leading to triggering cell proliferation, morphogenic center formation, and shoot regeneration.

A combined proteomics and metabolomics analysis reveals the invisible regulation of plant root responses to oxybenzone (benzophenone-3) stress

Oxybenzone, an environmental pollutant affecting both agriculture and aquatic ecological integrity, has been demonstrated to act as a physiological and metabolic inhibitor on plants, animals, and microorganisms. Research on oxybenzone in higher plants has focused on the above-ground anatomy (leaves), while research on the under-ground parts (roots) has been neglected. In this study, the changes in plant root protein expression and metabolic pathways under oxybenzone treatment were explored through a combined proteomics and metabolomics analysis. A total of 506 differential proteins and 96 differential metabolites were identified, which were mainly distributed in critical pathways such as those for carbon (C) and nitrogen (N) metabolism, lipid metabolism, and antioxidation. Bioinformatics analysis shows that oxybenzone toxicity is predominantly reflected in alterations to root respiratory homeostasis and the manifestation of damaging reactive oxygen species (ROS) and membrane lipid peroxidation, changes to disease resistance-associated proteins, changes to normal C-flow distribution, and the inhibition of cell absorption and utilization of N sources. Plants respond to oxybenzone stress mainly by reconfiguring the mitochondrial electron-transport-chain to bypass oxidative-damage components; improving the efficiency of the antioxidant system to remove excessively accumulated ROS; promoting the detoxification of harmful membrane lipid peroxides; increasing osmotic adjustment substance (such as proline and raffinose) accumulation; adjusting C flow distribution to produce more nicotinamide adenine dinucleotide phosphate (NADPH) for the glutathione cycle; and accumulating free amino acids to increase plant stress tolerant. Our results are the first to map the changes in the physiological and metabolic regulatory network of higher plant roots under oxybenzone stress.

Unraveling the role of germination days on the aroma variations of roasted barley malts via gas chromatography-mass spectrometry based untargeted and targeted flavoromics

Roasting imparts malts with an increased amount of hedonic aromas. However, the relationship between the production of roasted malts and the generation of characteristic malt aromas remains unclear. In this study, roasted barley malts (RM) were prepared from three consecutive germination days (3, 4, 5D), and the aroma profiles among RM and base malt were holistically compared via HS-SPME-GC-MS/O-based flavoromics. Furthermore, the wort color, free amino acids, reducing sugars, and fatty acids compositions were determined before-and-after roasting. Results showed that roasting could flatten variations of precursors regardless of germination days. Additionally, based on quantitation of 53 aromas, a PLS-DA model was applied to differentiate all malts by 17 aromas with VIP ≥ 1. As for aroma harmony, RM with 4D-germination outstood due to a pleasant nutty note with the highest sweet-to-nutty index of 0.8. This work answers how germination days would impact the aroma of RM for the first time.

Valorisation of fresh waste grape through fermentation with different exogenous probiotic inoculants

The disposal of fresh waste grape berries restraining the sustainable development of vineyards. The aims of this study were to evaluate the effects of different exogenous probiotic inoculants on the fermentation of fresh waste grape berries. In the fermentation process, the variations of pH and EC value, chemical characteristics of the fermentation products, as well as the microbial communities' composition were simultaneously observed. In addition, the feasibility of using the fermentation products as chemical fertilizer substitute in agricultural production also has been verified in this study. The results indicated that the different probiotic inoculants has shown clear impacts on the variation trends of pH and EC value in the grape waste fermentation. Lactobacillus casei and Zygosaccharomyces rouxii are ideal probiotics for the fermentation of waste grape, which enhanced the contents of free Aa and other nutrients in fermentation products. Compared with Fn treatment (without exogenous inoculants), the total free Aa contents in Fs (inoculation with Z. rouxii) and Fm (inoculation with L. casei and Z. rouxii mixture) treatments have improved by 199.1% and 325.5%, respectively. The microbial communities' composition during the fermentation process also been greatly influenced by the different inoculants. At the genus level, Lactobacillus and Pseudomonas were the dominant bacteria, while Saccharomyces and Candida were the dominant fungi in the fermentation. Using the fermentation products as chemical fertilizer substitute has enhanced the quality of Kyoho grape. Compared with traditional chemical fertilization treatment (T1), application with fermented grape waste (T2) has significantly improved VC and soluble solid contents in grape berries by 16.89% and 20.12%, respectively. In conclusion, fermentation with suitable probiotics was an efficient approach for the disposal and recycling of fresh waste grape in vineyards.

Novel insight into flavor and quality formation in naturally fermented low-salt fish sauce based on microbial metabolism

Low-salt fermentation is an effective way to shorten the fermentation time of fish sauce. In this study, the changes of microbial community, flavor, and quality during the natural fermentation of low-salt fish sauce were studied, followed by the elucidation of flavor and quality formation mechanisms based on microbial metabolism. The 16S rRNA gene high-throughput sequencing showed that both richness and evenness of microbial community were reduced during fermentation. The microbial genera, including Pseudomonas, Achromobacter, Stenotrophomonas, Rhodococcus, Brucella, and Tetragenococcus were more suitable for the fermentation environment, and obviously increased along with the fermentation. There were a total of 125 volatile substances identified by HS-SPME-GC-MS, of which 30 substances were selected as the characteristic volatile flavor substances, mainly including aldehydes, esters, and alcohols. Large amounts of free amino acids were produced in the low-salt fish sauce, especially umami and sweet amino acids, as well as high concentrations of biogenic amines. Correlation network constructed by the Pearson's correlation coefficient showed that most characteristic volatile flavor substances were significantly positively correlated with Stenotrophomonas, Achromobacter, Rhodococcus, Tetragenococcus, and Brucella. Stenotrophomonas and Tetragenococcus were significantly positively correlated with most free amino acids, especially umami and sweet amino acids. Pseudomonas and Stenotrophomonas were positively correlated with most biogenic amines, especially histamine, tyramine, putrescine, and cadaverine. Metabolism pathways suggested that the high concentrations of precursor amino acids contributed to the production of biogenic amines. This study indicates that the spoilage microorganisms and biogenic amines in the low-salt fish sauce need to be further controlled, and the strains belonging to Tetragenococcus can be isolated as potential microbial starters for the production of low-salt fish sauce.

Development of novel fermented stinky sea bass and analysis of its taste active compounds, flavor compounds, and quality

This paper developed novel fermented stinky sea bass (FSSB) products and reports the first analysis of its taste active compounds, flavor compounds, and quality. The FSSB with Xian Hen stinky tofu (F-XH) had the best sensory quality. After fermentation, the texture of FSSB improved, and the umami amino and sweet amino acid contents significantly increased, whereas that of the bitter amino acids decreased. Moreover, the IMP content and EUC in FSSB increased significantly. Of the six key volatile flavor compounds distinguished, the key volatile flavor compounds of F-XH are Ethyl Acetate, Propan-2-ol, alpha-pinene, 2-methylbutanal, acetol, 4-Methylpentan-2-one. Ethyl Acetate and 2-propanol were thought to give F-XH its unique wine flavor after cooking. The quality evaluation results demonstrated that the six FSSB complied with the Chinese Standard (GB10136-2015) (2015) animal aquatic products. Six types of FSSB products with unique flavors were developed, and a reference was provided for their industrial application.

Intracerebroventricular injection taurine changes free amino acid concentrations in the brain and plasma in chicks

Brain amino acid metabolism has been reported to regulate body temperature, feeding behavior and stress response. Central injection of taurine induced hypothermic and anorexigenic effects in chicks. However, it is still unknown how the amino acid metabolism is influenced by the central injection of taurine. Therefore, the objective of this study was to investigate the changes in brain and plasma free amino acids following central injection of taurine. Five-day-old male Julia layer chicks (n = 10) were subjected to intracerebroventricular (ICV) injection with saline or taurine (5 µmol/10 µL). Central taurine increased tryptophan concentrations in the diencephalon, and decreased tyrosine in the diencephalon, brainstem, cerebellum, telencephalon and plasma at 30 min post-injection. Taurine was increased in all the brain parts after ICV taurine. Although histidine and cystathionine concentrations were increased in the diencephalon and brainstem, several amino acids such as isoleucine, arginine, methionine, phenylalanine, glutamic acid, asparagine, proline, and alanine were reduced following central injection of taurine. All amino acid concentrations were decreased in the plasma after ICV taurine. In conclusion, central taurine quickly changes free amino acid concentrations in the brain and plasma, which may have a role in thermoregulation, food intake and stress response in chicks.

Impact of Monascus purpureus fermentation on antioxidant activity, free amino acid profiles and flavor properties of kelp (Saccharina japonica)

This study evaluated the efficacy of Monascus purpureus fermentation on Saccharina japonica (SJ). Healthy substances and antioxidant activity of fermented SJ (FSJ) were determined. Results showed that fermentation caused the release of phenolic compounds and flavonoids, which resulted in the enhancement of antioxidant activity. Essential amino acids and γ-aminobutyric acid also greatly accumulated in FSJ. Sensory evaluation and gas chromatography-ion mobility spectrometry (GC-IMS) were used to evaluate flavor properties of FSJ. A lexicon consisted of 24 descriptors was established for SJ and FSJ, of which 14 descriptors were regarded as odor attributes. A total of 46 volatile compounds were identified by GC-IMS and showed positive correlation with odor attributes. Fifteen volatile compounds were screened as key compounds, tricarboxylic acid cycle, embden-meyerhof-parnas and amino acid catabolism were main formation metabolisms of them. Advanced properties of FSJ indicated that fermentation is a promising approach for the production of SJ food.

Feeding pigs amino acids as protein-bound or in free form influences postprandial concentrations of amino acids, metabolites, and insulin

Dietary proteins need to be digested first while free amino acids (AAs) and small peptides are readily available for absorption and rapidly appear in the blood. The rapid postprandial appearance of dietary AA in the systemic circulation may result in inefficient AA utilisation for protein synthesis of peripheral tissues if other nutrients implicated in AA and protein metabolism are not available at the same time. The objective of this experiment was to compare the postprandial concentrations of plasma AA and other metabolites after the ingestion of a diet that provided AA either as proteins or as free AA and small peptides. Twenty-four male growing pigs (38.8 ± 2.67 kg) fitted with a jugular catheter were assigned to one of three diets that provided AA either in protein form (INT), free AA and small peptides (HYD), or as free AA (FAA). After an overnight fast and initial blood sampling, a small meal was given to each pig followed by serial blood collection for 360 min. Postprandial concentrations of plasma AA, glucose, insulin, and urea were then measured from the collected blood. Non-linear regression was used to summarise the postprandial plasma AA kinetics. Fasting concentrations of urea and some AA were higher (P < 0.05) while postprandial plasma insulin and glucose were lower (P < 0.01) for INT than for HYD and FAA. The area under the curve of plasma concentration after meal distribution was lower for INT for most AAs (P < 0.05), resulting in a flatter curve compared to HYD and FAA. This was the result of the slower appearance of dietary AA in the plasma when proteins are fed instead of free AA and small peptides. The flatter curve may also result from more AAs being metabolised by the intestine and liver when INT was fed. The metabolism of AA of the intestine and liver was higher for HYD than FAA. Providing AA as proteins or as free AA and small peptides affected the postprandial plasma kinetics of AA, urea, insulin, and glucose. Whether the flat kinetics when feeding proteins has a positive or negative effect on AA metabolism still needs to be explored.

Trace determination of fifteen free amino acids in drinking source water via solid-phase extraction coupled with liquid chromatography tandem mass spectrometry

Amino acids (AAs) are important nitrogen-containing organics in water, and a large number of reports have proven that they were the precursors of many nitrogen-containing disinfection by-products, some of which have cytotoxicity and carcinogenicity. However, little has been done on their occurrence in drinking source water. Therefore, a trace determination method via solid-phase extraction coupled with ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for 15 free AAs (FAAs) was developed, which was successfully applied for drinking source water samples. For sample preparation, strong cation-exchange stationary solid-phase extraction (SPE) cartridge showed better extraction performance to that of reverse phase stationary oasis HLB SPE cartridge. The optimal water pH was determined to be 2.8 before extraction. Strong matrix effects for most FAAs were observed in this work; thus, sample extraction with SPE was recommended to eliminate the matrix effects. The developed method showed excellent linearity (R² > 0.991), low limits of detection (LODs, 0.01-0.27 nmol/L), and good recoveries of 69.8-117.9% in drinking source water with low relative standard deviations (RSDs, 0.3-13.2%). The developed method was finally applied to eight drinking source water samples, and the top five FAAs were found to be serine, glycine, leucine, alanine, and isoleucine.

Transcriptomic and metabolomic analyses reveal the main metabolites in Dendrobium officinale leaves during the harvesting period

Dendrobium officinale, which is a medicine food homology plant, contains many metabolites, especially polysaccharides and flavonoids. Unlike flowers and stems, which are the most frequently harvested organs for a variety of uses, leaves tend to be discarded. This study assessed main metabolites in leaves to identify the most appropriate timing of collection during harvest, which was divided into three stages (S1-S3: 8, 10, and 11 months after sprouting, respectively). Metabolomic and transcriptomic analyses of S1-S3 were performed. Water-soluble polysaccharides (WSPs), flavonoids and free amino acids (FAAs) were detected in leaves. WSPs decreased from S1 to S3 but flavonoids and some FAAs (e.g., phophoserine) increased from S1 to S2, then decreased from S2 to S3. In all three stages, mannose was the dominant monosaccharide among WSPs, followed by glucose. In S2, 35 flavonoids were identified, the most abundant being rutin, schaftoside and vitexin, while 34 FAAs were identified in all three stages, the most abundant being tyrosine, phosphoserine and alanine. A total of 2584, 3414 and 2032 differentially expressed genes (DEGs) were discovered in S1 vs S2, S1 vs S3 and S1 vs S3, respectively. Correlation analysis revealed that five DEGs (DoSUS, DoXYLA, DoFRK, DoGMP, and DoCSLA), two DEGs (DoDFR, and DoANS) and a single DEG (DoPGAM) were involved in the metabolism of WSPs, flavonoids and phosphoserine, respectively. The findings of this study lay a foundation for the commercial exploitation of metabolites in the harvested leaves of D. officinale, and the use of detected DEGs in applied genetic studies.

Comparison of the ionisation mode in the determination of free amino acids in beers by Liquid Chromatography tandem mass spectrometry

A comparison of positive and negative ionization modes in LC-ESI-MS/MS was carried out for the analysis of derivatized amino acids in 15 different beer samples. 22 free amino acids were derivatized using Diethyl ethoxymethylenemalonate (DEEMM) and their content was determined. When using the DEEMM as derivatization reagent the negative ionization mode provided analytical performance equal to or in some cases even superior to the positive ionization mode. For 6 amino acids (Thr, β-Ala, α-Ala, Met, Val and Orn) the negative mode led to lower LoQ values, while the positive mode offered lower LoQ values for 5 amino acids (Arg, Asp, Glu, GABA, and Pro). The remaining 11 amino acids showed similar LoQ values in both modes. Because of this, negative ionization mode allowed to detect and quantify amino acids such as: β-Alanine, threonine, and ornithine whose concentrations were low in most of the analysed samples. The relative standard deviation (RSD) for the results in both modes were similar. The method's linearity was determined to be in the range of 1 to 130 ppb with r² > 0.99. Recoveries ranged from 93 to 112%. Negative mode was less affected by matrix effects the main effect was signal enhancement. In contrast, the positive ionization mode suffered from signal enhancement as well as signal suppression.

Physiological changes and rate of resistance of Acrosiphonia arcta (Dillwyn) Gain upon exposure to diesel fuel

The changes in the morpho-physiological state of green alga Acrosiphonia arcta upon exposure to diesel fuel (DF) at concentrations of 20; 100; 1,000; 2,000; 3,000 of maximum permissible concentrations (MPC) were studied. The main physiological stress markers, such as enzymes of the antioxidant system (AOS), non-enzymatic antioxidants (carotenoids) and free amino acids (as components of plant metabolome) were measured. In general, all concentrations of the petroleum product used changed the activity of the antioxidant system, changed the intensity of physiological processes (photosynthesis, free amino acid synthesis) and also affected the structure of microbiomes inhabiting the surface of algae.

It was shown that the concentration of DF within 1 mg/l (20 MPC) was not lethal as plants were able to maintain physiological activity and the observed changes were reversible.

Although DF exposure caused decreases in superoxide dismutase (SOD) activity, proline concentration and photosynthetic rate, increases in catalase activity and pigment concentration were observed. After the effects of stress disappeared, most physiological parameters were restored, except for carotenoid content.

Higher DF concentrations (100 MPC and higher) caused injury to cell structures and damage to the pigment apparatus. The restoration of functions after the termination of exposure to stress was not achieved. Epiphytic bacterial communities actively responded both to the introduction of a toxicant and to the changing physiological parameters of algae by the change in the numbers of cultured heterotrophic bacteria. The results of this study showed that the concentration of petroleum products in the water decreased to values not exceeding MPC in the presence of algae in the environment.

Effects of polysaccharides from Yingshan Yunwu tea on free amino acids, flavor nucleotides and antioxidant abilities in chickens

Tea polysaccharides possess a variety of physiological activities including anti-oxidant, anti-cancer, anti-diabetic, immunomodulatory, hypolipidemic, and cation chelating ability, which have been proved a promising feed additive. Our study aimed to investigate the effects of polysaccharides from Yingshan Yunwu tea (GTPS) on free amino acids, flavor nucleotides and antioxidant ability in chickens. A total of 200 chickens were randomly divided into to 4 groups. Chickens were fed chicken basal diet with GTPS (200, 400 and 800 mg/kg). The results showed that GTPS increased body weight, average daily gain, and average daily feed intake in chickens. Moreover, GTPS increased the total amount of free amino acids of meat, and increased the content of histidine, leucine, serine, glutamic acid and alanine. GTPS also increased contents of inosine monophosphate and guanylic monophosphate, which improved the meat flavor of chickens. In addition, GTPS significantly increased (P < 0.05) contents of GSH-Px, SOD and T-AOC, and reduced content of MDA. It also increased Nrf2, NQO-1 and HO-1 mRNA expressions, and decreased Keap1expression. GTPS increased Nrf2 and HO-1 protein levels, and decreased Keap1 level. The above findings indicated that GTPS could be a promising natural feed additive in poultry industry.

A versatile technique based on surface-enhanced Raman spectroscopy for label-free detection of amino acids and peptide formation in body fluids

As an effective analytical method, surface-enhanced Raman spectroscopy (SERS) is widely used in the detection of nucleic acids, amino acids, and other biomolecules. However, obtaining the SERS signal of nonaromatic amino acids is still a challenge. In this work, excess sodium borohydride was used as a reducing agent to prevent the surface of silver nanoparticles from being coated with AgO to enable amino acid molecules to reach the surface of silver nano-substrates. Calcium ions were used as aggregators for silver nano-substrates to successfully achieve the label-free and accurate fingerprint determination of various nonaromatic amino acids. Different types of amino acids were distinguished based on the changes in their peak intensity that were obtained using colorless and transparent organic dichloromethane (DCM) as the internal standard. A Raman signal for low-concentration amino acids in body fluids was detected, and the detection limit for tyrosine was 5 ng/mL. Moreover, the physical and chemical properties of peptides and the formation of peptide chains were further analyzed. The proposed method can potentially be applied to protein sequencing.

Dynamic sensations of fresh and roasted salmon (Salmo salar) during chewing

The sensory perception of food is a dynamic procedure, which is closely related to the released flavor stimuli. Thus, we evaluated the dynamic sensations of fresh and roasted salmon during the chewing process and investigated the tastants released in saliva. For fresh salmon, the fishy, umami, salty, and sweet attributes were perceived successively. Meanwhile, the smoky and fried flavors were the most dominant attributes of roasted salmon at the beginning, then various attributes were perceived. During the chewing process, free amino acids and 5'-nucleotides released in saliva were quantified. Compared to the sensory data, the results demonstrated that glutamic acid and inosine 5'-monophosphate released in saliva might induce the umami perception. The sweet-tasting amino acids alanine and glycine may contribute to sweetness. Therefore, we suggested that the time dimension of tastants dissolved in saliva would affect the dynamic sensation of food, even for complex food materials.

Comparison of gut microbial communities, free amino acids or fatty acids contents in the muscle of wild Aristichthys nobilis from Xinlicheng reservoir and Chagan lake

BACKGROUND

Fish is favored by consumers, while amino acids and fatty acids are the main nutrients of muscle. At present, it has been found that the gut microbial community may be involved in the regulation of host material anabolism. Juvenile and adult bighead carp (A. nobilis) from Chagan lake and Xinlicheng reservoir were selected, and divided into four groups to compare the differences of gut microbial communities, free amino acid and fatty acids in muscle.

RESULTS

The results showed that fish in different lakes or ages contained specific microbiota, the gut microbial structure was similar, but the microbial content was significantly different. Gut microbial abundance of juvenile fish in Chagan lake was significantly higher than that of other groups. Phylum level analysis Proteobacteria was the dominant gut bacteria of fish in both adult and juvenile fish from two separate lakes. Actinobacteria was another dominant bacterial phylum in juvenile fish in both lakes. Contents of free amino acids and fatty acids in muscle were detected, and the relationships between them and gut microbial communities were analyzed. Bighead carp grew from juvenile to adult, Actinobacteria abundance decreased (P < 0.05) and Proteobacteria increased (P < 0.05). Proteobacteria was positively correlated with the contents of Thr, Lys, Pro, Asp, Gly and Glu, Actinobacteria was negatively correlated with Met and His. Meanwhile, EPA and DHA were positively correlated with Proteobacteria, EPA and DHA were not significantly associated with Actinobacteria.

CONCLUSION

It was speculated that the contents of free amino acids and fatty acids in muscle might be affected by the difference of gut microbiota, thus affecting the taste and nutritional quality.

Free threonine in human breast milk is related to infant intestinal microbiota composition

BACKGROUND

Accumulating evidence indicates that free amino acids (FAA) might be bioactive compounds with potential immunomodulatory capabilities. However, the FAA composition in human milk is still poorly characterized with respect to its correlation to maternal serum levels and its physiological significance for the infant. Studies addressing the relation of human milk FAA to the infants' intestinal microbiota are still missing.

METHODS

As part of a pilot study, maternal serum and breast milk FAA concentrations as well as infant intestinal microbiota (16S rRNA) were determined 2 months after birth. The study cohort consisted of 41 healthy mothers and their term delivered, healthy infants with normal birthweight. The relationship between maternal serum and milk FAA was determined by correlation analyses. Associations between (highly correlated) milk FAA and infant intestinal beta diversity were tested using PERMANOVA, LefSe and multivariate regression models adjusted for common confounders.

RESULTS

Seven breast milk FAA correlated significantly with serum concentrations. One of these, threonine showed a negative association with abundance of members of the class Gammaproteobacteria (R²adj = 17.1%, p = 0.006; β= - 0.441). In addition, on the level of families and genera, threonine explained 23.2% of variation of the relative abundance of Enterobacteriaceae (R²adj; p = 0.001; β = - 0.504) and 11.1% of variability in the abundance of Escherichia/Shigella (R²adj, p = 0.025; β  = - 0.368), when adjusted for confounders.

CONCLUSION

Our study is the first to suggest potential interactions between breast milk FAA and infant gut microbiota composition during early lactation. The results might be indicative of a potential protective role of threonine against members of the Enterobacteriaceae family in breast-fed infants. Still, results are based on correlation analyses and larger cohorts are needed to support the findings and elucidate possible underlying mechanisms to assess the complex interplay between breast milk FAA and infant intestinal microbiota in detail.

Microbial community changes induced by Pediococcus pentosaceus improve the physicochemical properties and safety in fermented tilapia sausage

Amine-negative lactic acid bacteria can prevent excess biogenic amines from accumulating in sausage. In this study, the amine-negative Pediococcus pentosaceus 30-7 and 30-15 with good fermentation properties and biogenic amine removal ability were isolated for tilapia sausage production. P. pentosaceus 30-7 improved the physical characteristics such as gel strength and hardness in tilapia sausage, while P. pentosaceus 30-15 significantly enhanced the contents of umami and sweet free amino acids. The microbial metabolic network revealed that the dominant microbial community in the fermentation process including Pediococcus and Lactococcus contributed to the physicochemical formation of sausage. The significant decrease of biogenic amine contents after addition of P. pentosaceus strains mainly resulted from their ability to remove biogenic amines and to inhibit the growth of amine-producing Enterobacter, Citrobacter, and Streptococcus. This study provides an effective method for directionally improving the physicochemical properties and safety in fermented tilapia sausage.

Formation mechanism of chloropicrin from amines and free amino acids during chlorination: A combined computational and experimental study

Chloropicrin as one of the most frequently detected N-DBPs has drawn great attention due to its high toxicity. However, our understanding of its formation mechanism is still very limited. A combined computational and experimental approach was used in this study to reveal chloropicrin formation mechanism during chlorination. Ethylamine, n-propylamine, alanine and tryptophan along with the above two amines and their four derivatives substituted by -OH or/and -NO₂ groups were chosen as computational and experimental model precursors, respectively. The results indicate that primary amines and free amino acids are more likely to share the same chloropicrin formation pathway including N-chlorination, imidization, β-C-alcoholization, N-nitration, α-C-chlorination and dealdehydation processes. Moreover, elimination of hydrochloric acid from N,N-dichloro-amine and electrophilic addition of N-chloroalkylimide with hypochlorous acid were found to be the rate-limiting steps among all the elementary reactions. By skipping over both of the above rate-limiting steps, RCH(OH)CH₂NO₂ and RCH(OH)CH₂NH(OH) compounds were proposed to be potent chloropicrin precursors, and experiments confirmed that 2-nitroethanol and N-methylhydroxylamine have the highest chloropicrin yields in the chlorination among all the precursors reported to date. The findings of this work are helpful for expanding the knowledge of chloropicrin formation mechanisms and predicting the potential chloropicrin precursors.

Thermal hydrolyzed food waste liquor as liquid organic fertilizer

Thermal hydrolysis (TH) is an efficient technology for food waste (FW) management. This study investigated the nutrients released from FW under various TH temperature (140, 160, 180, 200 and 220 °C) and evaluated the feasibility of the hydrolyzed liquor (HL) as liquid organic fertilizer. The phytotoxicity and biotoxicity of HL was analyzed using wheat seed and Pseudomonas putida. Results revealed that TH could effectively solubilize FW and release nutrients (N, P and K) and organic substances. The highest content of total nitrogen (TN, 1685 mgN/L) and phosphorus (TP, 235 mgP/L) in the HL was obtained under 180 °C. The K⁺ was 278-293 mg/L regardless of treatment temperature. Secondary nutrients (Ca and Mg) and micro metals (Fe, Cu, Zn, Al, Co and Mn) were all detected at relatively high level, while heavy metals (As and Cd) were generally lower than 0.5 mg/L. Twenty types of free amino acid were identified and the maximum total concentration was 4965.13 mg/L. 2% HL displayed higher germination index (>80%) and enhanced root and shoot lengths. No biotoxicity was observed as confirmed by the bioassay. This study proposes a feasible method to solubilize food waste and produce liquid organic fertilizer.

Effects of different sulfur-containing substances on the structural and flavor properties of defatted sesame seed meal derived Maillard reaction products

Lately, plant derived proteins have been used extensively to produce Maillard reaction products (MRPs) for the preparation of various functional food products. We evaluated the effects of cysteine (Cys), methionine (Met), and thiamine (Thi) on the color and flavor development of MRPs derived from sesame seed meal. Compared with the MRPs of sesame seed hydrolysate (SSH), Cys-MRPs had the strongest antioxidant activity and fluorescence intensity, showing the stronger taste and overall acceptability. These MRPs contained the highest sulfur compounds which resulted into stronger meat flavor. Moreover, the content of free amino acids in Met-MRPs was the highest. Compared with MRPs of SSH alone, MRPs with different sulfur content had better flavor characteristics and physicochemical properties, which entail their usage in different food ingredients.

Free amino acid contents of selected Ethiopian plant and fungi species: a search for alternative natural free amino acid sources for cosmeceutical applications

Free amino acids (FAAs), the major constituents of the natural moisturizing factor (NMF), are very important for maintaining the moisture balance of human skin and their deficiency results in dry skin conditions. There is a great interest in the identification and use of nature-based sources of these molecules for such cosmeceutical applications. The objective of the present study was, therefore, to investigate the FAA contents of selected Ethiopian plant and fungi species; and select the best sources so as to use them for the stated purpose. About 59 different plant species and oyster mushroom were included in the study and the concentrations of 27 FAAs were analyzed. Each sample was collected, lyophilized, extracted using aqueous solvent, derivatized with Fluorenylmethoxycarbonyl chloride (Fmoc-Cl) prior to solid-phase extraction and quantified using Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC-ESI-MS/MS) system. All the 27 FAAs were detected in most of the samples. The dominant FAAs that are part of the NMF were found at sufficiently high concentration in the mushroom and some of the plants. This indicates that FAAs that could be included in the preparations for the management of dry skin condition can be obtained from a single natural resource and the use of these resources for the specified purpose have both economic and therapeutic advantage in addition to fulfilling customer needs.

Flash dietary methionine supply over growth requirements in pigs: Multi-facetted effects on skeletal muscle metabolism

Dietary methionine affects protein metabolism, lean gain and growth performance and acts in the control of oxidative stress. When supplied in large excess relative to growth requirements in diets for pigs, positive effects on pork quality traits have been recently reported. This study aimed to decipher the molecular and biochemical mechanisms affected by a dietary methionine supply above growth requirements in the loin muscle of finishing pigs. During the last 14 days before slaughter, crossbred female pigs (n = 15 pigs/diet) were fed a diet supplemented with hydroxy-methionine (Met5; 1.1% of methionine) or not (CONT, 0.22% of methionine). Blood was sampled at slaughter to assess key metabolites. At the same time, free amino acid concentrations and expression or activity levels of genes involved in protein or energy metabolism were measured in the longissimus lumborum muscle (LM). The Met5 pigs exhibited a greater activity of creatine kinase in plasma when compared with CONT pigs. The concentrations of free methionine, alpha-aminobutyric acid, anserine, 3-methyl-histidine, lysine, and proline were greater in the LM of Met5 pigs than in CONT pigs. Expression levels of genes involved in protein synthesis, protein breakdown or autophagy were only scarcely affected by the diet. Among ubiquitin ligases, MURF1, a gene known to target creatine kinase and muscle contractile proteins, and OTUD1 coding for a deubiquitinase protease, were up-regulated in the LM of Met5 pigs. A lower activity of citrate synthase, a reduced expression level of ME1 acting in lipogenesis but a higher expression of PPARD regulating energy metabolism, were also observed in the LM of Met5 pigs compared with CONT pigs. Principal component analysis revealed that expression levels of many studied genes involved in protein and energy metabolism were correlated with meat quality traits across dietary treatments, suggesting that subtle modifications in expression of those genes had cumulative effects on the regulation of processes leading to the muscle transformation into meat. In conclusion, dietary methionine supplementation beyond nutritional requirements in pigs during the last days before slaughter modified the free amino acid profile in muscle and its redox capacities, and slightly affected molecular pathways related to protein breakdown and energy metabolism. These modifications were associated with benefits on pork quality traits.

Free amino acid composition of saliva in patients with healthy periodontium and periodontitis

OBJECTIVES

To identify and compare the free amino acids in the saliva of periodontitis patients and healthy individuals and to assess their levels in different periodontal disease types.

MATERIALS AND METHODS

There were three groups: healthy individuals (control (C); n = 20), Stage III Grade B generalized periodontitis (GP-B; n = 20), and Stage III Grade C generalized periodontitis (GP-C; n = 20). Clinical periodontal parameters were measured. Amino acid analysis of the saliva was accomplished by liquid chromatography-mass spectrometry (LC MS/MS), taking the mean concentration.

RESULTS

Citrulline and carnosine concentrations were significantly higher in patients with periodontitis than in the control group (p < 0.017). Methionine, glutamic acid, and arginine showed significantly higher concentrations in GP-C, whereas proline and tryptophan showed higher concentrations in the GP-B group (p < 0.017). There was a significant correlation between methionine, citrulline, arginine, and carnosine and clinical periodontal parameters.

CONCLUSIONS

Our results demonstrate that periodontal status and disease type can result in variations in salivary amino acid (AA) content in correlation with clinical inflammatory signs. The significant correlation of methionine, citrulline, carnosine, and arginine with clinical parameters, regardless of systemic status, suggests that the levels of different salivary free AAs play roles in periodontitis.

CLINICAL RELEVANCE

Salivary free AAs may be suggested as a potential diagnostic compound in patients with periodontitis.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT04642716.

Interaction among species, time-of-day, and soil water potential on biochemical and physiological characteristics of cladodes of Opuntia

The physiology and biochemistry of young Opuntia spp. cladodes relate with their Crassulacean acid metabolism, which extends over the day-night cycle in four phases, is species-dependent and is affected by water availability. This study aimed to assess the interaction among species, time-of-day, and the soil water potential (Ψ_W) on biochemical and physiological characteristics of cladodes of Opuntia species. Three-week-old cladodes were harvested at 7:00 a.m. and 3:00 p.m. from plants with or without irrigation for 30 d (-0.17 and -5.72 MPa soil Ψ_W), from O. albicarpa, O. ficus-indica, O. hyptiacantha, O. megacantha, and O. streptacantha. The experimental design was a factorial 5 x 2 x 2 (species, sampling time and soil Ψ_W). The experimental unit was one cladode per plant, and six repetitions were evaluated. Total acids, glucose, fructose, sucrose, starch, total phenolics, free amino acids, and soluble proteins concentrations were evaluated, as well as acid invertase and neutral invertase activities. The interaction among species x soil Ψ_W and species x time of the day was significant (P ≤ 0.05) in all variables evaluated. An exception was the species x soil Ψ_W on starch concentration (P = 0.1827). The biochemical and physiological characteristics of Opuntia cladodes were modified by the time of the day and soil Ψ_W interaction, but most of the characteristics were positively or inversely affected depending on the species, frequently displaying a descending trend following O. streptacantha, O. hyptiacantha, O. megacantha, O. albicarpa and O. ficus-indica. The total acids, glucose, fructose, starch, soluble proteins, and free amino acids concentrations revealed that domestication significantly modifies C and N metabolism in Opuntia.

Effects of emersion on acid-base regulation, osmoregulation, and nitrogen physiology in the semi-terrestrial mangrove crab, Helice formosensis

Emersion limits water availability and impairs the gill function of water-breathing animals resulting in a reduced capacity to regulate respiratory gas exchange, acid-base balance, and nitrogenous waste excretion. Semi-terrestrial crustaceans such as Helice formosensis mitigate these physiological consequences by modifying and recycling urine and branchial water shifting some branchial workload to the antennal glands. To investigate how this process occurs, Helice formosensis were emersed for up to 160 h and their hemolymph and urinary acid-base, nitrogenous waste, free amino acids, and osmoregulatory parameters were investigated. Upon emersion, crabs experienced a respiratory acidosis that is restored by bicarbonate accumulation and ammonia reduction within the hemolymph and urine after 24 h. Prolonged emersion caused an overcompensatory metabolic alkalosis potentially limiting the crab's ability to remain emersed. During the alkalosis, hemolymph ammonia was maintained at control levels while urinary ammonia remained reduced by 60% of control values. During emersion, ammonia may be temporarily converted to alanine as part of the Cahill cycle until re-immersion where crabs can revert alanine to ammonia for excretion coinciding with the crabs' observed delayed ammonia excretion response. The presence of high hemolymph alanine concentrations even when immersed may indicate this cycle's use outside of emersion or in preparation for emersion. Furthermore, H. formosensis appears to be uniquely capable of actively suppressing its rate of desiccation in absence of behavioral changes, in part by creating hyperosmotic urine that mitigates evaporative water loss.

Metabolic variations in the pulp of four litchi cultivars during pulp breakdown

Fruit of four litchi cultivars were stored at 25 ± 1 °C. The shelf life changed from long to short respectively was "Feizixiao (FXZ), "Jingganghongnuo (JGHN)", "Huaizhi (HZ)" and "Nuomici (NMC)". During pulp breakdown, marketable fruit and total soluble solids (TSS) decreased significantly, while respiratory rate increased significantly. After metabolomics analysis, a total of 179 metabolites were detected in litchi pulp, including 56 primary metabolites, 79 volatile compounds, 28 free amino acids and 16 hydrolyzed amino acids. Compared with other litchi cultivars, FZX pulp was rich in volatile alcohols and amino acids, NMC pulp was rich in soluble sugars and sesquiterpenes, and JGHN and HZ pulp were rich in sesquiterpenes. During the postharvest storage, most of volatiles and amino acids were induced in NMC pulp, while most of volatiles were reduced in JGHN and HZ pulp. The specific metabolites accumulated in a litchi pulp might be related to its shelf life and fruit quality. The increased metabolites during pulp breakdown might be also related to the resistance of litchi pulp.