Changes of protein oxidation, lipid oxidation and lipolysis in Chinese dry sausage with different sodium chloride curing salt content

Comprehensive insights into the mechanism of flavor formation driven via inoculation with mixed starter cultures in dry-fermented tilapia sausages: Integration of macrogenomics, volatilomics, and lipidomics

To investigate the mechanisms of flavor formation in dry-fermented tilapia sausages, the volatiles, bacterial community, and lipid composition during fermentation were analyzed using gas chromatography-ion mobility spectrometry, 16S high throughput sequencing, and ultra-performance liquid chromatography-mass spectrometer. Pediococcus pentosaceus, Staphylococcus xylosus, and Staphylococcus carnosus became dominant bacteria during the fermentation. A total of 66 volatiles and 293 lipids (48 differential lipids) were identified. PC and PE content decreased. Aldehyde and 1-octen-3-ol content decreased. Most esters and ketones content increased during fermentation. Six metabolic pathways associated with differential lipids were identified by enrichment analysis. Glycerophospholipid metabolism was the main metabolic pathway. Correlation analysis revealed that PC and PE were precursors for volatiles, including PC 16:0/18:2 and PE 18:0/22:6. The dominant bacteria facilitate the hydrolysis of PC and PE, leading to the formation of esters and ketones. This study provides a theoretical basis for the targeted regulation of fermented sausage flavors.

Effect of non-enzymatic browning on oysters during hot air drying process: Color and chemical changes and insights into mechanisms

Hot air drying (HAD) is an extensive method used on oysters and it causes the most intuitive change, a color change. However, the mechanism of color change remains unclear. This study showed that oysters underwent browning during the HAD process. The colorimetric parameter L* decreased while a* and b* increased, all of which were well described by the first-order color kinetic model. Mechanistically, the HDA process induced the oxidative browning of phenols and the generation of Maillard reaction products (5-hydroxymethylfurfural and hydrophilic pyrrole). Meanwhile, the HAD process caused lipid oxidation, leading to the reduction of phosphatidylethanolamine and the generation of reactive carbonyl compounds (aldehydes and α-dicarbonyl compounds). Moreover, the accumulation of hydrophobic pyrroles, a lipid-induced Maillard-like reaction product, was observed. These results suggest that, in addition to phenolic oxidation, sugar- and amino acid-mediated non-enzymatic browning reactions, lipid-mediated Maillard-like reactions play important roles in oyster darkening during the HAD process.

The impacts of cold plasma on the taste and odor formation of dried silver carp products

This study investigated non-thermal pretreatment (cold plasma, CP) on the flavor (taste and odor) profiles of dried fish products. CP treatment of 5 min contributed to accumulation of umami nucleotides adenosine 5'-monophosphate (AMP) from 30.96 to 40.82 μg/g and inosine 5'-monophosphate (IMP) from 2009.29 to 2132.23 μg/g, and significant reduction of bitter hypoxanthine ribonucleoside (HxR) and hypoxanthine (Hx), respectively (P < 0.05) in the dried fish products. A noticeable enhancement in sweet glycine (from 429.41 to 490.03 mg/100 g) and umami glutamic acid (from 55.68 to 67.76 mg/100 g) accompanied with the CP treatment (P < 0.05) based on taste activity value (TAV > 1). And the characteristic odor volatiles (nonanal, hexanal and 1-octen-3-ol) were strengthened 2.13-, 2.16- and 2.17- folds, respectively (P < 0.05). The results of equivalent umami concentration and Gibbs free energy calculation, combining with the correlation analysis, indicate that nucleotides and free amino acids synergically enhanced the taste improvement of dried fish products. Moderate lipids oxidation favored the formation of characteristic volatiles. The CP pretreatment offered new strategies for enhancing flavor of dried fish products.

Effects of basic amino acids on heterocyclic amines and quality characteristics of fried beef patties at low NaCl level

The impact of basic amino acids (Lysine, Arginine, Histidine) on the formation of total heterocyclic amines (HAs) was investigated in fried beef patties at 1% NaCl level. Different levels of basic amino acids (0.1%, 0.5%, 1%) significantly inhibited the formation of the total and individual HAs at 1% NaCl, and the inhibitory effect was more effective than 3% NaCl (6.19 ng/g, 26.93% inhibition) (P < 0.05). Lys at 1% reduced total HAs the most (2.46 ng/g, 70.88% inhibition), followed by 1% His (2.79 ng/g, 67.03% inhibition) and 1% Arg (3.43 ng/g, 59.51% inhibition). Compared to the 3% NaCl, the quality characteristics (moisture content, frying loss, texture profile, and color) of the fried beef patties were significantly improved when basic amino acids were added at 1% NaCl (P < 0.05). The lipid oxidation of fried beef patties was significantly inhibited by 1% Arg and 1% Lys at 1% NaCl level (P < 0.05). The results indicated that basic amino acids could inhibit the formation of total HAs while maintaining the quality of meat products at low NaCl condition.

Identification and validation of core microbes for the formation of the characteristic flavor of fermented oysters (Crassostrea gigas)

Self-fermented oyster homogenates were prepared to investigate core microbes and their correlations with flavor formation mechanisms. Five bacterial and four fungal genera were identified. Correlation analysis showed that Saccharomyces cerevisiae, Kazachstania, and L. pentosus were core species for the flavor of fermented products. Four core microbes were selected for inoculation into homogenates. Twelve key aroma compounds with odor activity values >1 were identified by gas chromatography-mass spectrometry. L. plantarum and S. cerevisiae were beneficial for producing key aroma compounds such as 1-octen-3-ol, (E,Z)-2,6-nonadienal, and heptanal. Fermentation with four microbes resulted in significant increases in contents of Asp, Glu, Lys, inosine monophosphate, and guanosine monophosphate, which provided freshness and sweetness. Fermentation with four microbes resulted in high digestibility, antioxidant abilities, and zinc contents. This study has elucidated the mechanism of flavor formation by microbial action and provides a reference for targeted flavor control in fermented oyster products.

Lipid Hydrolysis, Oxidation, and Fatty Acid Formation Pathway Mapping of Synergistically Fermented Sausage and Characterization of Lipid Mediating Genes

Starter cultures play a significant role in lipid hydrolysis, prevention of lipid oxidation, and synthesis of fatty acid in fermented sausage, enhancing product quality. In this study, five synergistic bacterial strains were used, including Pediococcus pentosaceus (B-3), Latilactobacillus sakei DLS-24 (D-24), Latilactobacillus acidophilus DLS-29 (D-29), Lactiplantibacillus pentosus (B-1), and Lactiplantibacillus plantarum (B-2). Sausage B1B3D24 gave the highest free fatty acid with 39.45 g/100 g at 45-Day. Based on 2-thiobarbituric acid reactive substance, B2B3 contains 112.68 MDA/kg. Lipoxygenase activity displays the lowest in B1B3D24 with 0.095 μmol/min·mg followed by B2B3 with 0.145 μmol/min·mg. B1B3D24 contains 11.35 g/kg of monounsaturated fatty acid with the highest content in eicosenoic acid (C20:1) and palmitoleic acid (C16:1). The fatty acid synthesis pathway in B1B3D24 contains an active positive interaction with PUFA to increase the isotopomers of ω-3 and ω-6 fatty acids. In addition, lipid mediating genes in B1B3D24 show the highest counts in fatty-acid synthase, carbonyl reductase 4, 3-oxoacyl-[acyl-carrier-protein] synthase III, hydroxysteroid 17-beta dehydrogenase 8, and acetyl-CoA carboxylase.

Effect of glycine and Pediococcus pentosaceus R1 combined application on the physicochemical properties, oxidative stability, and taste profile of Harbin dry sausages

This study investigated the effects of the application of glycine (Gly) and Pediococcus pentosaceus R1(Pp), alone or in combination, on the physicochemical properties, oxidative stability, and taste quality of Harbin dry sausages. The results demonstrated that after nine days of fermentation, the Gly + Pp group exhibited significantly (P < 0.05) lower moisture content (19.04%), water activity (0.686), and pH (4.78) values, alongside notably (P < 0.05) higher lactic acid bacteria count (8.11 log CFU/g sausage) and redness value (17.2), compared to the other three groups (P < 0.05). In addition, the dry sausages in the Gly + Pp group exhibited the lowest peroxide value (0.34 meq/kg sausage), thiobarbituric acid reactive substances (0.46 MAD/kg sausage), and protein carbonyl content (1.26 nmol/kg protein) during fermentation, followed by the Gly group, Pp group, and control group. Electronic tongue (e-tongue) and sensory evaluations revealed that the combined treatment with P. pentosaceus R1 and Gly resulted in superior taste characteristics. Besides, partial least squares regression (PLSR) analysis illustrated that the taste qualities characterized using the e-tongue were accordant with the sensory evaluation consequences, and total free amino acids (FAAs) and organic acids contributed to the dry sausages' taste properties. In conclusion, the combined application of Gly and P. pentosaceus R1 enhanced the physicochemical properties, oxidative stability, and taste profile of Harbin dry sausages.

Correlations of dynamic changes in lipid and protein of salted large yellow croaker during storage

Protein and lipid are two major components that undergo significant changes during processing of aquatic products. This study focused on the protein oxidation, protein conformational states, lipid oxidation and lipid molecule profiling of salted large yellow croaker during storage, and their correlations were investigated. The degree of oxidation of protein and lipid was time-dependent, leading to an increase in carbonyl content and surface hydrophobicity, a decrease in sulfhydryl groups, and an increase in conjugated diene, peroxide value and thiobarbituric acid reactive substances value. Oxidation caused protein structure denaturation and aggregation during storage. Lipid composition and content changed dynamically, with polyunsaturated phosphatidylcholine (PC) was preferentially oxidized compared to polyunsaturated triacylglycerol. Correlation analysis showed that the degradation of polyunsaturated key differential lipids (PC 18:2_20:5, PC 16:0_22:6, PC 16:0_20:5, etc.) was closely related to the oxidation of protein and lipid. The changes in protein conformation and the peroxidation of polyunsaturated lipids mutually promote each other's oxidation process.

Effect of Lactobacillus helveticus IMAUJBH1 on fat and volatile flavor substances in fermented mutton sausages

The decomposition and oxidation of fat is essential for the formation and quality of the unique flavor of sausage. To explore the effect of lactic acid bacteria on fat decomposition and oxidation in fermented sausage, free fatty acids and volatile flavor compounds were determined by gas chromatography (GC) and headspace solid-phase microextraction (HS-SPME)-GC-MS, respectively. The results showed that the addition of Lactobacillus helveticus IMAUJBH1 inhibited fat peroxidation and relatively increased the proportion of monounsaturated fatty acids. A total of 47 volatile flavor compounds were detected, including aldehydes, esters, alcohols, and ketones. The content of substances such as hexanal, heptanal, nonanal and 1-octene-3-ol related to lipid oxidation was significantly reduced. The results obtained in this study show that the strain can further affect the flavor of the product by inhibiting the formation of lipid oxidation or peroxide flavor substances to a certain extent.

Mechanism of salt effect on flavor formation in lightly-salted large yellow croaker by integrated multiple intelligent sensory and untargeted lipidomics analyses

Salt has a great influence on food flavor formation. In this study, electronic tongue and nose, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and lipid oxidation levels were used to investigate the influence of different NaCl concentrations on the flavor formation of lightly salted large yellow croaker. The results showed that salt improves the sensory characteristics of the product. Hexanal, 2,5-octanedione, octanal, 1-octen-3-ol, nonanal, and heptanal were key flavor compounds. Phospholipids containing 18-carbon fatty acids are major flavor precursor substances. The TBARS values in samples increase with the increase of salt levels significantly (p < 0.05). Products marinated in 6% NaCl showed the highest lipase activity. Thus, NaCl promotes the hydrolysis and oxidation of phospholipids by increasing lipase activity to produce key flavor substances. This study provides valuable insights into the effects of NaCl on flavor formation, which may help to regulate the flavor of salt-reduced food.

Effects of high hydrostatic pressure on peelability and quality of crayfish(Procambarus clarkii)

BACKGROUND

Peeling of crayfish is a very important process in production. Crayfish peeling by machine can increase production efficiency and enhance safety in the production process. The tight muscle-shell attachment causes difficulty in peeling freshly caught crayfish. However, few studies have explored the changes in crayfish quality under favorable shell-loosening treatments.

RESULTS

In this study, the shell-loosening properties of crayfish and changes in crayfish quality, microstructure and protein fluorescent features were investigated after high hydrostatic pressure (HHP) treatment. New methods were established to measure the peeling performance of crayfish, which are peelability and meat yield rate (MYR). The normalization of peelability and MYR were verified by different weights of crayfish tails and different treatments. The peeling effect of HHP-treated crayfish was evaluated by a new quantitative measurement method, and MYR was calculated. The results showed that all the HHP treatments reduced crayfish peeling work and increased MYR. The HHP treatment provided better crayfish quality in terms of texture and color and enlarged the shell-loosening gap. Among all HHP treatments, 200 MPa treatment exhibited lower peeling work, higher MYR and an expansion of the shell-loosening gap, reaching up to 573.8 μm. At the same time, 200 MPa treatment could maintain crayfish quality.

CONCLUSION

The findings outlined above suggest that high pressure is a promising method for loosening crayfish shells. 200 MPa is an optimal HHP treatment condition for crayfish peeling, exhibiting a promising application in industrial processing. © 2023 Society of Chemical Industry.

Novel NaCl reduction technologies for dry-cured meat products and their mechanisms: A comprehensive review

Sodium chloride (NaCl) confers a unique flavor and quality in meat products, however, due to growing concerns about the adverse effects of excessive NaCl consumption, how to reduce NaCl content while ensuring quality and safety has become a research hotspot in this field. This review mainly discusses the role of NaCl in dry-cured meat, as well as novel salt-reducing substances that can substitute for the effects of NaCl to achieve sodium reduction objectives. New technologies, such as vacuum curing, ultrahigh pressure curing, ultrasonic curing, pulsed electric field curing, and gamma irradiation, to facilitate the development of low-sodium products are also introduced. The majority of current salt reduction technologies function to enhance salt diffusion and decrease curing time, resulting in a decrease in NaCl content. Notably, future studies should focus on implementing multiple strategies to compensate for the deficiencies in flavor and safety caused by NaCl reduction.

Antibacterial efficacy of phenyllactic acid against Pseudomonas lundensis and Brochothrix thermosphacta and its synergistic application on modified atmosphere/air-packaged fresh pork loins

Microbial contamination is a crucial problem that is difficult to solve for the meat industry. Therefore, this study explored the antibacterial efficacy of phenyllactic acid (PLA) against Pseudomonas lundensis (PL) and Brochothrix thermosphacta (BT) solely and in combination (PL + BT). It also provided insights into its synergistic preservation effect during inoculation in chilled (4 °C) fresh pork loins under air (AP) and modified atmosphere packaging (MAP). The minimum inhibitory concentration (MIC) of PLA was 10 mg/mL. Growth kinetics, scanning electron microscopy (SEM), zeta potential, and cell viability investigations showed that PLA treatment exhibited reduced bacterial growth, aided morphological alterations, and leakage in cell membrane integrity in vitro. Nonetheless, PLA and MAP (70 %N2/30 %CO2) showed an excellent synergistic antibacterial ability against spoilage indicators(total glucose, pH, TVB-N, and TBARS), bacterial counts than AP, without impairing organoleptic acceptability. These results demonstrate the broad antibacterial efficacy of PLA as a biopreservative for the meat industry.

Evaluation of the effects of compound curing agents on the lipid profiles and volatile flavors in Nuodeng ham based on lipidomics and GC-IMS analysis

Eighteen raw legs were evenly divided into two groups and salted with 100% NaCl and compound curing agent (60% NaCl + 40% KCl + 90 mg/kg NaNO2) to investigate the effect of compound curing agent on lipid metabolites and volatile flavor compounds in Nuodeng ham. The results of UHPLC-QE-MS and GC-IMS combined with multivariate statistical analysis showed that 27 lipid metabolites and 30 characteristic volatile flavor compounds were identified as characteristic markers in different treatment groups. The compound curing agent promoted the release of TG, SQDG, Hex1Cer, and LPC in Nuodeng ham, and accelerated the formation of volatile compounds such as 2-propanone, nonanal-d, gamma-butyrolactone, ethhyl acetate and benzeneacetaldehyde et al. Through correlation analysis, ketones were positively correlated with some PUFAs and negatively correlated with most MUFAs. Processing Nuodeng ham with compound curing agents has a positive effect on improving its quality. These findings provide a scientific theoretical basis for the development and utilization of compound curing agent.

Development of Chinese-Style Sausage Enriched with Djulis (Chenopodium formosanum Koidz) Using Taguchi Method: Applying Modern Optimization to Indigenous People's Traditional Food

Djulis (Taiwanese quinoa) has gained popularity among researchers due to its biological characteristics and rich nutritional value. Incorporating Djulis is expected to enhance the sausage's texture, flavor, and storage stability due to the presence of antioxidants and nutritional components. However, limited studies focus on product development based on this emerging health-promoting ingredient in the food industry. This study aims to develop Chinese-style sausage enriched with Djulis using the Taguchi L9(34) orthogonal matrix methodology and evaluate the influence of four factors, including un-hulled to hulled Djulis ratios of 0, 50, 100% (A), backfat-to-lean meat ratios of 0/100, 30/70, 50/50% (B), cooking temperature of 55, 75, 95 °C (C), and nitrite content of 0.03, 0.05, 0.07 g/kg (D) on products' sensory and physicochemical properties. The optimal Taguchi formulation was then verified and compared with conventionally formulated sausage (original sausage) in terms of hardness, springiness, gumminess, CIE color values, and peroxide value (POV). The optimal formulation was A3B2C2D3, which consisted of 16.8% hulled Djulis, 30/70 backfat-to-lean meat ratio, 75 °C cooking temperature, and 0.03 g/kg nitrite content. The most influential independent parameters were identified as B > A > C > D, placing Djulis incorporation as the first runner-up, just after the backfat-to-lean meat ratio. Optimized condition verification identified the Signal-to-Noise ratio (S/N) of 16.63. Comparing the optimized Djulis-enriched sample and the original sausage indicated similar CIE L*, a*, b*, hardness, and springiness but different gumminess according to Texture Profile Analysis (TPA). The Djulis-enriched sausage at the optimized formulation had a significantly lower POV compared to the control sample (4.65 vs. 9.64 meq/kg), which was found to be correlated with Djulis antioxidant effects with 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical antioxidant activity of 62.37%. This suggests that Djulis effectively mitigates sausage organoleptic deterioration. Djulis sausage, with natural antioxidants and reduced fat content, could cater to consumer preferences and enhance the market for the food industry and indigenous farmers.

Integrative deep learning framework predicts lipidomics-based investigation of preservatives on meat nutritional biomarkers and metabolic pathways

Preservatives are added as antimicrobial agents to extend the shelf life of meat. Adding preservatives to meat products can affect their flavor and nutrition. This review clarifies the effects of preservatives on metabolic pathways and network molecular transformations in meat products based on lipidomics, metabolomics and proteomics analyses. Preservatives change the nutrient content of meat products via altering ionic strength and pH to influence enzyme activity. Ionic strength in salt triggers muscle triglyceride hydrolysis by causing phosphorylation and lipid droplet splitting in adipose tissue hormone-sensitive lipase and triglyceride lipase. DisoLipPred exploiting deep recurrent networks and transfer learning can predict the lipid binding trend of each amino acid in the disordered region of input protein sequences, which could provide omics analyses of biomarkers metabolic pathways in meat products. While conventional meat quality assessment tools are unable to elucidate the intrinsic mechanisms and pathways of variables in the influences of preservatives on the quality of meat products, the promising application of omics techniques in food analysis and discovery through multimodal learning prediction algorithms of neural networks (e.g., deep neural network, convolutional neural network, artificial neural network) will drive the meat industry to develop new strategies for food spoilage prevention and control.

Lipidomics reveals the relationship between lipid oxidation and flavor formation of basic amnio acids participated Low-Sodium cured large yellow croaker

The effects of basic amino acids on lipid oxidation and the formation of volatile compound in low-sodium cured large yellow croaker were investigated. Basic amino acids contribute a lot in inhibiting the degradation of phospholipids, especially l-lysine. Lipid oxidation was also inhibited by basic amino acids, and the total oxidation of groups could be sorted as low-sodium (LS) > control (C) > l-Histidine participated LS group (LS-His) > l-Arginine participated LS group (LS-Arg) > l-lysine participated LS group (LS-Lys). PC 18:1/20:5, PC 16:0/18:1, triacylglycerol (TG) 16:1/20:5/22:6, etc., were found to be key differential lipid metabolites, and 1-propanol, 2-methyl, gamma-hexalactone, etc. were recognized as key differential volatile compounds. The results of correlation analysis showed that alcohols and esters were positively correlated with TG molecules composed of saturated fatty acids and monounsaturated fatty acids. These findings provided new insights into the relationship between flavor formation and the degradation and oxidation of lipids.

Multiomics reveals the formation pathway of volatile compounds in preserved egg yolk (PEY) induced by NaCl: Based on the model of PEY and salted egg yolk (SEY) treated with/without NaCl

The models of preserved egg yolk (PEY) and salted egg yolk both treated with or without NaCl were performed to explore the effect of NaCl on the characteristic volatile compounds (VOCs) in PEY. 1-hexanol, 2-heptanone, isoamyl acetate, etc., compounds were confirmed as the characteristic VOCs in PEY mainly induced by NaCl and the formation of 1-octanol, 2-pentylfuran, ammonia, etc., characteristic VOCs induced by NaCl may depend on the combined effect of Cu2+ and OH-. Among them, 1-hexanol and 2-heptanone were formed from linoleic acid in PS(18:0_18:2) and oleic acid in PG(22:6_18:1), respectively, through multi-omics and correlation analysis. Meanwhile, 1-octanol may originated from β-oxidation of oleic acid in PS(18:1); 2-pentylfuran and ammonia maybe derived from the derivative of aspartate and the degradation of l-methionine, respectively. Moreover, this study provides a new insight to parse the influence of NaCl with/without other exogenous factors on the formation of VOCs in food products.

Occurrence, Concentration and Toxicity of 54 Polycyclic Aromatic Hydrocarbons in Butter during Storage

Polycyclic aromatic hydrocarbons (PAHs) are a class of highly carcinogenic compounds with a lipophilic nature. This study investigated the characterization of PAH24 contamination in twenty-one types of butter and five types of margarines using the QuEChERS pretreatment coupled with GC-QqQ-MS. Additionally, low-temperature storage experiments were conducted to explore the variations in oxidation index as well as the PAH levels. The results revealed that PAH24 concentrations in butter and margarine were 50.75-310.64 μg/kg and 47.66-118.62 μg/kg, respectively. The PAH4 level in one type of butter reached 11.24 μg/kg beyond the EU standards. Over 160 days of storage at 4 °C, acid value (AV), peroxide value (POV), and acidity significantly increased, while malondialdehyde (MDA) content and carbonyl value (CGV) fluctuated. Concentrations of PAH24 and oxidized PAHs (OPAHs) experienced a notable reduction of 29.09% and 63.85%, respectively. The slow reduction in naphthalene (NaP) indicated the dynamic nature of PAHs during storage. However, the toxic equivalency quotients (TEQs) decreased slightly from a range of 0.65-1.90 to 0.39-1.77, with no significant difference. This study contributes to the understanding of variations in PAHs during storage, which is of great significance for food safety.

Effects of Mustard Seed Extract on Physicochemical and Storage Characteristics of Dry-aged Pork Loin Ham

This study investigated the effects of mustard seed extracts on physicochemical and storage characteristics of dry-aged pork loin ham during the aging period. In experiment 1, antioxidant activity was assessed for mustard seed extracted with varying ethanol concentrations and the results showed high antioxidant activity at 25%, 50%, and 75% ethanol concentrations. In experiment 2, pork loin was treated with mustard seed extracts obtained using different ethanol concentrations: not treated (control), 25% (MS25), 50% (MS50), and 75% (MS75). Physicochemical and storage characteristics of pork loin ham were measured in wk 0, 2, 4, and 6. The pH, aw, CIE b*, thiobarbituric acid reactive substances and volatile basic nitrogen values were lower in treated samples compared to the control (p<0.05). In conclusion, applying mustard seed extracts, particularly MS75, in the dry-aged pork loin ham production process could enhance storage stability and improve color attributes without having negative impacts on product quality.

Flavor Formation in Dry-Cured Fish: Regulation by Microbial Communities and Endogenous Enzymes

Dried salted fish is a traditional dry-cured fish that is sprinkled with salt before the curing process. With a unique flavor as well as diverse varieties, dry-cured fish is popular among consumers worldwide. The presence of various microbial communities during the curing process leads to numerous metabolic reactions, especially lipid oxidation and protein degradation, which influence the formation of flavor substances. However, during industrial curing, the quality of dry-cured fish is difficult to control, leading to the formation of products with diverse flavors. This review describes the curing process of dried salted fish, the key microorganisms involved in the curing process of typical dried salted fish products at home and abroad, and the correlation between biological metabolism and flavor formation and the underlying mechanism. This review also investigates the prospects of dried salted fish products, proposing methods for the analysis of improved curing processes and the mechanisms of dried salted fish. Through a comprehensive understanding of this review, modern production challenges can be addressed to achieve greater control of microbial growth in the system and improved product safety. In addition to advancing our understanding of the processes by which volatile flavor compounds are formed in conventional dry-cured fish products, we expect that this work will also offer a theoretical framework for enhancing their flavor in food processing.

Computer-Aided Lipase Engineering for Improving Their Stability and Activity in the Food Industry: State of the Art

As some of the most widely used biocatalysts, lipases have exhibited extreme advantages in many processes, such as esterification, amidation, and transesterification reactions, which causes them to be widely used in food industrial production. However, natural lipases have drawbacks in terms of organic solvent resistance, thermostability, selectivity, etc., which limits some of their applications in the field of foods. In this systematic review, the application of lipases in various food processes was summarized. Moreover, the general structure of lipases is discussed in-depth, and the engineering strategies that can be used in lipase engineering are also summarized. The protocols of some classical methods are compared and discussed, which can provide some information about how to choose methods of lipase engineering. Thermostability engineering and solvent tolerance engineering are highlighted in this review, and the basic principles for improving thermostability and solvent tolerance are summarized. In the future, comput er-aided technology should be more emphasized in the investigation of the mechanisms of reactions catalyzed by lipases and guide the engineering of lipases. The engineering of lipase tunnels to improve the diffusion of substrates is also a promising prospect for further enhanced lipase activity and selectivity.

Combined Effects of Cold and Hot Air Drying on Physicochemical Properties of Semi-Dried Takifugu obscurus Fillets

The physicochemical properties of semi-dried Takifugu obscurus fillets in cold air drying (CAD), hot air drying (HAD), and cold and hot air combined drying (CHACD) were analyzed based on pH, water state, lipid oxidation, protein degradation, and microstructure, using a texture analyzer, low-field nuclear magnetic resonance, thiobarbituric acid, frozen sections, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and differential scanning calorimetry. Water binding to the samples was enhanced by all three drying methods, and the immobilized water content of CHACD was between that of HAD and CAD. The pH of the semi-dried fillets was improved by CHACD. When compared to HAD and CAD, CHACD improved the springiness and chewiness of the fillets, especially cold air drying for 90 min (CAD-90), with values of 0.97 and 59.79 g, respectively. The muscle fibers were arranged compactly and clearly in CAD-90, having higher muscle toughness. CHACD reduced the drying time and degree of lipid oxidation compared to HAD and CAD. CAD better preserved protein composition, whereas HAD and CHACD promoted actin production; CHACD had a higher protein denaturation temperature (74.08-74.57 °C). CHACD results in better physicochemical properties than HAD or CAD, including shortened drying time, reduced lipid oxidation, enhanced protein stability, and denser tissue structure. These results provide a theoretical basis for selecting the appropriate drying method for T. obscurus in industrial applications.

Recent Advances in the Incorporation of Polysaccharides with Antioxidant and Antibacterial Functions to Preserve the Quality and Shelf Life of Meat Products

Meat and meat products are susceptible to various types of natural processes such as oxidative degradation due to their high content of protein and essential amino acids. However, finding solutions to maintain the nutritional and sensory quality of meat and meat products is unavoidable. Hence, there is a pressing need to investigate alternatives to synthetic preservatives, focusing on active biomolecules of natural provenance. Polysaccharides are natural polymers of various sources that exhibit antibacterial and antioxidant properties via a variety of mechanisms, owing to their diversity and structural variation. For this reason, these biomolecules are widely studied in order to improve texture, inhibit the growth of pathogens, and improve the oxidative stability and sensory characteristics of meat products. However, the literature has not addressed their biological activity in meat and meat products. This review summarizes the various sources of polysaccharides, their antioxidant and antibacterial activities (mainly against pathogenic food strains), and their use as natural preservatives to replace synthetic additives in meat and meat products. Special attention is given to the use of polysaccharides to improve the nutritional value of meat, resulting in more nutrient-rich meat products with higher polysaccharide content and less salt, nitrites/nitrates, and cholesterol.

Biopreservative Effect of the Tunisian Halophyte Lobularia maritima Flavonoid Fraction, Used Alone and in Combination with Linalool in Stored Minced Beef Meat

In the present study, Lobularia maritima (Lm) flavonoid extract (LmFV) was characterized by HPLC analyses and five compounds were detected. Further, to describe the chemical content of the matrix, GC-MS analyses after silylation were performed; the obtained results showed the presence of a large number of components belonging to several chemical classes, mostly sugar alcohols, sugars, fatty acids, and terpenes. Firstly, the antibacterial activities of this fraction and linalool (Lin) were evaluated against eight foodborne pathogenic strains with MIC values between 2.3 and 5.8 mg/mL and 0.23 and 0.7 mg/mL, respectively. Then, the antioxidant activity of both was evaluated by the DPPH antiradical test and the phosphomolybdenum test. Furthermore, the biopreservative effect of LmFV alone and in combination with Lin on minced beef stored at 4 °C for 14 days was evaluated using microbiological and physiochemical tests. LmFV at 4.6% alone significantly reduced microbial spoilage in ground meat (p < 0.05). The combination of LmFV (4.6%) and Lin (0.46%) was more effective than LmFV alone in inhibiting bacterial contamination, reducing TBARS values and the risk of bacterial contamination, and reducing the accumulation of Met myoglobin (MetMb). This combination, therefore, extends the shelf life of the product by about 10 days. Based on these microbiological results and physicochemical parameters, it can be stated that the addition of Lin potentiates the flavonoid fraction of L. maritima more strongly against the deterioration of meat quality by significantly improving its biopreservative effect as a natural conservative.

Changes in the lipid profiles of hairtail (Trichiurus lepturus) muscle during air-drying via liquid chromatography-mass spectrometry analysis

Chemical and liquid chromatography-mass spectrometry (LC/MS)-based lipidomics analyses were performed to explore the alterations in lipid profiles in the hairtail muscle during air-drying. The peroxide value (POV) and carbonyl group value (CGV) in the air-dried hairtail (ADH) significantly increased with air-drying time. Lipidomics results revealed 1,326 lipids, which were grouped into 33 lipid categories, including 422 triglycerides (TGs), 170 phosphatidylcholines (PCs), 110 phosphatidylethanolamines (PEs), among others. In addition, ADH contained 131 and 201 differentially abundant lipids (DALs) at high and low levels, respectively. Among them, DALs, TGs, PCs, LPCs, and LPEs could be used to distinguish between ADH and FH samples. The apparent alterations in ADH and FH samples were attributed to lipid decomposition, side-chain modifications during oxidation, or oxygen- and salt-promoted lipid oxidation. Thus, this study provides a more comprehensive understanding of hairtail lipid profiles before and after air-drying which can be used as a guide for hairtail products.

Identification of Optimal Fermentation Temperature for Dry-Fermented Sausage Using Strains Isolated from Korean Fermented Foods

This study aims at identifying the optimal fermentation temperature for dry-fermented sausage using strains isolated from Kimchi (GK1, Pediococcus pentosaceus-GK1; NK3, P. pentosaceus-NK3), Doenjang (D1, Debaryomyces hansenii-D1), and commercial fermented sausage (S6, spontaneously generated Penicillium nalgiovense-S6). The microbial population, pH, moisture content, color, thiobarbituric acid reactive substance (TBARS), volatile basic nitrogen (VBN), and electronic nose (E-nose) were analyzed to identify the optimal fermentation temperature. The dry-fermented sausages were inoculated with three types of starter cultures [CS (commercial starter culture), GD (GK1 + D1 + S6), and ND (NK3 + D1 + S6)]. The fermentation was performed for 3 days at 20 °C and 25 °C, and dried for 28 days. The Lactobacillus spp. plate count and TBARS showed significantly higher values in the 25 °C group than in the 20 °C group (p < 0.05). The Staphylococcus spp. plate count of GD and ND were significantly higher than CS group at all temperatures. On day 31, the moisture content and VBN values of all groups were less than 35 % and 20 mg%, respectively. According to E-nose, the highest amount of acetoin was detected at the GD group fermented at 25 °C. Thus, the optimal fermentation temperature is expected at 25 °C after using GD in the manufacturing of dry-fermented sausages.

Flavor formation based on lipid in meat and meat products: A review

Meat product is popular throughout the world due to its unique taste. Flavor is one of the most important quality characteristics of meat products and also is a key influencing factor in the overall acceptability of meat products. The flavor of meat products is formed by precursors undergoing a series of complex reactions. During meat product processing, lipids are hydrolyzed by lipase to produce flavor precursors such as free fatty acid, then further oxidized to form volatile flavor compounds. This review summarizes lipolysis, lipid oxidation, and interaction of lipid with Maillard reaction and amino acid during meat products processing and storage as well as influencing factors on lipid degradation including raw meat (source of meat, feeding pattern, and castration), processing methods (thermal processing, nonthermal processing, salting, and fermentation) and additives. Meanwhile, the volatile compounds produced by lipids in meat products including aldehydes, alcohols, ketones, and hydrocarbons are summed up. Analytical methods of volatile compounds and the application of lipidomics analysis in mechanisms of flavor formation of meat products are also reviewed. PRACTICAL APPLICATIONS: Flavor is one of the most important quality characteristics of meat products, which influences the acceptability of meat products for consumption. Lipids play an important role in the flavor formation of meat products. Understanding the relationship between flavor compounds and changes in lipid compositions during the processing and storage of meat products will be helpful to control the quality of meat products.

Active edible films based on green tea extract and gelatin for coating of fresh sausage

The objective of this work was to develop, characterize and evaluate the application of active edible films based on gelatin and green tea extract in coating of fresh sausages. The green tea extract showed IC50 of 0.088 mg/mL and minimum inhibitory concentrations of 0.05 mg/mL for Listeria monocytogenes, 0.025 mg/mL for Staphylococcus aureus, 0.04 mg/mL for Escherichia coli, and >1.0 mg/mL for Salmonella enterica serovar Choleraesuis. The formulation with 15% (w/v) of gelatin and 30% (w/w) of glycerol showed better adhesion and appearance in the coating of the product. When using 1.0% of green tea extract, the lowest IC50, was obtained and the antioxidant activity was maintained for 35 days. There was a more accentuated decrease in pH and an increase in acidity and peroxide index in fresh sausages without film compared to those coated with the active film (1.0% of green tea extract) during storage. In addition, it was found that the use of active gelatin film (1.0% of green tea extract) kept the TBARS indexes of fresh sausage samples lower than the standard (without coating) and of films containing only gelatin, after 48 days of storage.

Novel Active Food Packaging Films Based on Gelatin-Sodium Alginate Containing Beetroot Peel Extract

Currently, the exploration of natural colorants from vegetal waste has gained particular attention. Furthermore, incorporation of these natural sources into biopolymers is an encouraging environmentally friendly approach to establishing active films with biological activities for food packaging. The present study developed bioactive antioxidant films based on gelatin-sodium alginate (NaAlg) incorporated with aqueous beetroot peel extract (BPE). Firstly, the effects of combining gelatin-NaAlg and BPE at 0.25, 0.5, and 1% on the mechanical, physical, antioxidant, and antibacterial properties of the films were analyzed. With increasing BPE, mechanico-physical properties and antioxidant and anti-foodborne pathogen capacities were enhanced. Likewise, when added to gelatin-NaAlg films, BPE remarkably increased the instrumental color properties. Moreover, during 14 days of storage at 4 °C, the impact of gelatin-NaAlg coating impregnated with BPE on microbial and chemical oxidation and on the sensory characteristics of beef meat samples was periodically assessed. Interestingly, by the end of the storage, BPE at 1% limited the microbial deterioration, enhanced the instrumental color, delayed chemical oxidation, and improved sensory traits. By practicing chemometrics tools (principal component analysis and heat maps), all data provided valuable information for categorizing all samples regarding microbiological and oxidative properties, sensory features, and instrumental color. Our findings revealed the ability of gelatin-NaAlg with BPE as an antioxidant to be employed as food packaging for meat preservation.

Investigation of effect of cold plasma on microbial load and physicochemical properties of ready-to-eat sliced chicken sausage

Sausage may be contaminated with spoilage microorganisms during the processing after cooking and during the chilling process. Non-thermal decontamination such as cold plasma (CP) can be used to prevent the growth of spoilage microorganisms in sausage after packaging. The objective of this study was to investigate the effects of CP on sliced chicken sausage during 60 days of storage. The sausages were divided into three groups: negative control, ultraviolet (UV)-radiated (positive control for 200 and 400 s), plasma (power of 30 and 70 w for 200 and 400 s). The microbial load, pH, color, peroxide value (PV), and textural parameters of the sausages were compared with those of the negative and positive controls. According to the results, total count decreased significantly (p < 0.05) about 1.87 log CFU/g after 400 s of the CP treatment and at the end of storage at 70 w. CP reduced the lightness (L*) and increased redness (a*) more than the UV rays. The PV more increased by UV rather than by plasma. There were no significant changes in pH value and textural parameters after the CP and UV treatments. Although CP more affected some of the physicochemical properties, compared with UV, CP was shown to efficiently inhibit the rapid growth of microorganisms, resulting in a longer shelf-life.

A Comprehensive Review on the Processing of Dried Fish and the Associated Chemical and Nutritional Changes

Fish is a good source of nutrients, although it is easily spoiled. As such, drying is a common method of preserving fish to compensate for its perishability. Dried fish exists in different cultures with varying types of fish used and drying methods. These delicacies are not only consumed for their convenience and for their health benefits, as discussed in this review. Most commonly, salt and spices are added to dried fish to enhance the flavours and to decrease the water activity (aw) of the fish, which further aids the drying process. For fish to be dried effectively, the temperature, drying environment, and time need to be considered along with the butchering method used on the raw fish prior to drying. Considering the various contributing factors, several physicochemical and biochemical changes will certainly occur in the fish. In this review, the pH, water activity (aw), lipid oxidation, and colour changes in fish drying are discussed as well as the proximate composition of dried fish. With these characteristic changes in dried fish, the sensory, microbial and safety aspects of dried fish are also affected, revolving around the preferences of consumers and their health concerns, especially based on how drying is efficient in eliminating/reducing harmful microbes from the fish. Interestingly, several studies have focused on upscaling the efficiency of dried fish production to generate a safer line of dried fish products with less effort and time. An exploratory approach of the published literature was conducted to achieve the purpose of this review. This evaluation gathers important information from all available library databases from 1990 to 2022. In general, this review will benefit the fishery and food industry by enabling them to enhance the efficiency and safety of fish drying, hence minimising food waste without compromising the quality and nutritional values of dried fish.

Encapsulation of Zanthoxylum bungeanum essential oil to enhance flavor stability and inhibit lipid oxidation of Chinese-style sausage

BACKGROUND

Zanthoxylum bungeanum essential oil (ZBEO) is a popular seasoning, commonly used in the food industry. It contains many easily degraded and highly volatile bioactive substances. Control of the stability of the bioactive substances in ZBEO is therefore very important in the food industry.

RESULTS

In this study, microencapsulation was applied to improve ZBEO stability. The key parameters for microcapsule preparation were optimized by the Box-Behnken design method, and the optimum conditions were as follows: ratio of core to wall, 1:8; ratio of hydroxypropyl-α-cyclodextrin (HPCD) to soy protein isolate (SPI), 4; total solids content, 12%; and homogenization speed, 12 000 rpm. Antioxidant experiments have indicated that tea polyphenols (TPPs) effectively inhibited hydroxy-α-sanshool degradation in ZBEO microcapsules. Application of ZBEO microcapsules in Chinese-style sausage effectively inhibited lipid oxidation in sausages and protected hydroxy-α-sanshool and typical volatiles from volatilization and degradation during sausage storage.

CONCLUSION

The results suggested that ZBEO microencapsulation is an effective strategy for improving the stability of its bioactive components and flavor ingredients during food processing. © 2022 Society of Chemical Industry.

UHPLC-Q-Exactive Orbitrap MS/MS-based untargeted lipidomics reveals molecular mechanisms and metabolic pathways of lipid changes during golden pomfret (Trachinotus ovatus) fermentation

Fermented golden pomfret (a popular marine fish product) is prepared via spontaneous fermentation. However, no comprehensive analysis has been reported on its lipid composition and metabolism. Herein, UHPLC-MS/MS-based untargeted lipidomic analysis identified 998 lipids (six classes; 29 subclasses) in fermented golden pomfret, including glycerolipids (47.70%) and glycerophospholipids (32.06%). As fermentation proceeded, triglyceride and diglyceride contents increased and subsequently decreased, while that of poly-unsaturated fatty acid-containing lipids increased (including those with docosahexaenoic acid, eicosapentaenoic acid, and docosapentaenoic acid). Pathway enrichment analysis identified seven lipid-related metabolic pathways, with the glycerophospholipid pathway found to be the most pertinent. Moreover, the decreased abundance of phosphatidylethanolamines and phosphatidylcholines during fermentation results from their high unsaturated fatty acid (FA) content. Indeed, essential FA contents increase following fermentation, due to their occurrence as glycerolipid side chains. Collectively, the results of this study provide a theoretical reference for optimizing the quality of fermented fish products.

Paradoxical effects of lipolysis on the lipid oxidation in meat and meat products

Lipolysis in meat and meat products is a phenomenon involving hydrolysis of lipids, notably via enzymatic catalysis that takes place even postmortem. During refrigerated and frozen storage of meat, in particular fish, endogenous lipolytic enzymes actively degrade triacylglycerols and phospholipids resulting in accumulation of free fatty acids and other hydrolytic products. A classical conjecture suggests that lipolysis enhances lipid oxidation which is involved in quality deterioration of fresh meat and, to some degrees, flavor development of certain meat products. Recent studies (<5 years) have shown that under some circumstances, lipolysis of certain lipolytic enzymes can inhibit lipid oxidation in muscle models, which provides more insight in lipid oxidation mechanisms in muscle matrices as well as implies potential strategies for improving meat quality. This review will discuss such paradoxical effects and potential mechanisms of lipolysis on lipid oxidation in meat and meat products.

Effect of Salt (Sodium Chloride) Replacement With Potassium Chloride, High Pressure Processing, and Cold Storage at 4°C on Beef Sausage Volatile Compounds

This study aimed to investigate the partial substitution of 0, 25 and 50% sodium chloride (NaCl) by potassium chloride (KCl) coupled with high-pressure processing (HPP) effects on volatile compounds and lipid oxidation of beef sausage at five (0, 3, 7, 14, and 21) different cold storage days (4°C). The odor activity values (OAV) of the various compounds were visualized by heat map analysis. Thiobarbituric acid reactive substances (TBARS) of the samples treated with 100% NaCl and HPP increased by an average of 0.52 ± 0.01 mg MDA/kg compared with the control (100% NaCl-no HPP) across the 21 storage days. In addition, 50% NaCl substitution with KCl in combinations with HPP treatments increased TBARS across the 21 storage days by an average of 0.40 ± 0.02 mg MDA/kg compared with no HPP treatment. However, on day 3, there was a sharp decrease in TBARS by an average of 0.10 ± 0.01 mg MDA/kg compared with days 0, 7, 14, and 21 in all treatments. At the end of 21 days of storage, a total of 227 volatile compounds were identified and quantified in the beef sausage, including 43 aldehydes, 46 phenols, 8 ketones, 30 alcohols, 14 acids, 12 esters, 27 terpenes, and 47 alkanes. However, no ketone compounds were detected on days 7, 14 and 21; esters on day 14 and acids on days 14 and 21 in the samples treated with or without HPP across the salts levels. However, high OAVs (OAV > 1) were obtained after partial substitution of NaCl with KCl at 25 and 50% with HPP treatment compared to the samples not treated with HPP. The aroma perceived in the beef sausage was due to compounds with the highest OAVs such as; pentadecanal, benzyl carbazate, anethole, myristicin, o-cresol, phenylacetaldehyde and (E)-methyl isoeugenol, pentadecanal, hexanoic acid, octanoic acid, eugenol, trans-2-nonenal, trans-2-octenal, trans-2-decenal, 2-butyl-1-octanol, 2,3-butanedione, ethyl hexanoate, ethyl octanoate, (-)-4-terpineol which had an OAV > 1 as compared to the other compounds with an OAV < 1. In conclusion, 25 and 50% NaCl partial replacement with KCl coupled with HPP technique can be considered in producing low-NaCl beef sausage in order to improve the flavor and decrease lipid oxidation during cold storage.

Development of Healthier and Functional Dry Fermented Sausages: Present and Future

In recent years, consumer perception about the healthiness of meat products has changed. In this scenario, the meat industry and the scientific and technological areas have put their efforts into improving meat products and achieving healthier and functional formulations that meet the demands of today’s market and consumers. This article aims to review the current functional fermented meat products, especially on sausage development. Firstly, an emphasis is given to reducing and replacing traditional ingredients associated with increased risk to consumer’s health (sodium, fat, and nitrites), adding functional components (prebiotics, probiotics, symbiotics, and polyphenols), and inducing health benefits. Secondly, a look at future fermented sausages is provided by mentioning emerging strategies to produce innovative healthier and functional meat products. Additional recommendations were also included to assist researchers in further development of healthier and functional sausages.

Promotion effect of salt on intramuscular neutral lipid hydrolysis during dry-salting process of porcine (biceps femoris) muscles by inducing phosphorylation of ATGL, HSL and their regulatory proteins of Perilipin1, ABHD5 and G0S2

Towards a better understanding of the formation mechanism of salt on intramuscular triglyceride (TG) hydrolysis occurring in biceps femoris (BF) muscles during dry-salting process, the changes of TG hydrolysis, TG hydrolysis activity and phosphorylation of adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL) as well as their regulatory proteins (Perilipin1, ABHD5, G0S2) with different salt content (0%, 1%, 3%, 5%) and salting time (the first and third day) were analyzed. The results showed that dry-salting significantly increased the TG hydrolase activity and hydrolysis extent with salting process proceed (P < 0.05), especially upon the treatment with 3% amount of salt. The SDS-PAGE and Western-blot results further demonstrated that the promotion of salt on TG hydrolysis in intramuscular adipocytes was mainly attributed to the activation of protein kinase activity and protein phosphorylation process. Accordingly, the ATGL and HSL were activated, and meanwhile, the TG hydrolysis pivotal switch perilipin1 was also turned on by phosphorylation modification.

Quantitative proteomics insights into gel properties changes of myofibrillar protein from Procambarus clarkii under cold stress

The impacts of cold stress (4 ℃ for 0 h, 12 h, 24 h, 36 h and 48 h, respectively) on the components, structural and physical properties of myofibrillar protein (MP) gel from Procambarus clarkii were investigated. The physicochemical analysis indicated the secondary and tertiary structure of MP were unfolding to different degrees after cold stress when compared to the control. The MP gel hardness reached a maximum when the cold stress reached 24 h. Furthermore, the quantitative proteomics results indicated that 20 up-regulated differentially abundant proteins (DAPs) were detected in 24 h when compared to control, specifically include myosin light chain 1 (MLC1) and skeletal muscle actin 6. Additionally, the combined analysis confirmed that MLC1 and skeletal muscle actin 6 might play key roles in hardening shrimp meat under cold stress. The results could provide a theoretical reference for the changes in crayfish muscle quality during cold chain transportation.

Impact of salt content and hydrogen peroxide-induced oxidative stress on protein oxidation, conformational/morphological changes, and micro-rheological properties of porcine myofibrillar proteins

Salting and rehydration of myofibrils can be interfered with free radical diffusion process. This study investigated the effects of salt content (0, 1, 3 and 5%) and H₂O₂/ascorbate-based hydroxyl radical (OH)-generating system (1, 10, 20 mM H₂O₂) on the oxidation, conformation, aggregation, and thermal stability of porcine myofibrillar proteins (MPs). Results showed that 5% of salt inhibited carbonylation of MPs with intensive sulfhydryl loss and tryptophan quenching. Fourier transform infrared (FTIR), laser light scattering, and scanning electron microscopy (SEM) suggested that 20 mM H₂O₂ transformed more α-helix into β-sheet of MPs, favoring larger aggregates being selectively exposed towards solvent during salt-induced fiber swelling. Oxidized MPs brined with ≤1% salt underwent partial unfolding with higher flexibility, while up to 5% of salt greatly hampered their hydration potential and weakened inter-fibrillar hydrogen bond with an improved protein solubility. Micro-rheology revealed that 1% of salt and 10 mM H₂O₂ rendered a denser structure of heat-set MPs gels.

Application of Aqueous Saline Process to Extract Silkworm Pupae Oil (Bombyx mori): Process Optimization and Composition Analysis

Silkworm pupae, a waste product from the silk production industry, can be an alternative source of edible oil, thus reducing the industry’s waste. In the present work, frozen silkworm pupae were used as raw material to extract oil via an aqueous saline process. The Box–Behnken design (BBD) and response surface methodology (RSM) were used to optimize the extraction process. The extraction conditions with the highest oil yield and a low peroxide value were obtained when using a saline solution concentration of 1.7% w/v, a ratio of aqueous liquid to silkworm pupae of 3.3 mL/g, and a 119 min stirring time at the stirring speed of 100 rpm. Under these conditions, silkworm oil with a yield of 3.32%, peroxide values of approximately 1.55 mM, and an acid value of 0.67 mg KOH/g oil was obtained. The extracted oil contained omega-3 acids (α-linolenic acid), which constituted around 25% of the total fatty acids, with approximate cholesterol levels of 109 mg/100 g oil. The amounts of β-carotene and α-tocopherol were approximately 785 and 9434 μg/100 g oil, respectively. Overall, the results demonstrated that oil extracted from silkworm pupae has good quality parameters and thus can be used as a new valuable source of edible lipids.

Protein Oxidation in Muscle Foods: A Comprehensive Review

Muscle foods and their products are a fundamental part of the human diet. The high protein content found in muscle foods, as well as the high content of essential amino acids, provides an appropriate composition to complete the nutritional requirements of humans. However, due to their special composition, they are susceptible to oxidative degradation. In this sense, proteins are highly susceptible to oxidative reactions. However, in contrast to lipid oxidation, which has been studied in depth for decades, protein oxidation of muscle foods has been investigated much less. Moreover, these reactions have an important influence on the quality of muscle foods, from physico-chemical, techno-functional, and nutritional perspectives. In this regard, the loss of essential nutrients, the impairment of texture, water-holding capacity, color and flavor, and the formation of toxic substances are some of the direct consequences of protein oxidation. The loss of quality for muscle foods results in consumer rejection and substantial levels of economic losses, and thus the control of oxidative processes is of vital importance for the food industry. Nonetheless, the complexity of the reactions involved in protein oxidation and the many different factors that influence these reactions make the mechanisms of protein oxidation difficult to fully understand. Therefore, the present manuscript reviews the fundamental mechanisms of protein oxidation, the most important oxidative reactions, the main factors that influence protein oxidation, and the currently available analytical methods to quantify compounds derived from protein oxidation reactions. Finally, the main effects of protein oxidation on the quality of muscle foods, both from physico-chemical and nutritional points of view, are also discussed.