Changes in volatile and non-volatile compounds of model kimchi through fermentation by lactic acid bacteria

Analysis of flavor substances changes during fermentation of Chinese spicy cabbage based on GC-IMS and PCA

This study employed a combination of principal component analysis (PCA) and gas chromatography-ion mobility spectrometry (GC-IMS) to examine the distinctive taste mixtures produced by Chinese spicy cabbage (CSC) fermented at varying temperatures. As the fermentation progressed, the pH gradually decreased and stabilized after the 11 days of fermentation, and the total content of organic acids and short-chain fatty acids increased. A total of 49 volatile mixtures were detected during CSC fermentation and storage for 21 days. These included 7 aldehydes, 6 alcohols, 7 esters, 6 ketones, 5 pyrazines, 4 sulfides, 4 phenols, 2 ethers, 2 olefins, and 1 acid. With time, the content of most volatile flavor substances decreased. PCA of the signal intensities of the volatile chemicals in the samples showed significant differences in the flavor of CSC fermented at different temperatures; consequently, the samples fermented at different temperatures were effectively separated in relatively independent regions of CSC. Therefore, low-temperature fermentation and storage at 4 °C were more suitable for CSC. Based on the identified volatile chemicals, HS-GC-IMS and PCA could effectively construct the flavour fingerprints of CSC samples. This study provided a theoretical basis for improving the fermentation quality of CSC.

Dynamics of nutrients, sensory quality and microbial communities and their interactions during co-fermentation of pineapple by-products and whey protein

In this study, a new fermented food was developed using pineapple by-products and whey protein (2.6%) as raw materials through the co-fermentation of autochthonous lactic acid bacteria and yeast. To better understand the fermentation mechanism and the impact of microorganisms on the entire fermentation system, we tracked the changes in carbohydrate and amino acid profiles, organoleptic quality and microbial community during the fermentation process. Compared with unfermented samples, dietary fiber and free amino acids increased significantly as fermentation proceeded. The fermented samples were significantly lower in astringency and bitterness and significantly higher in sourness, umami and richness. The fermented products were richer in volatile compounds with floral, cheesy, fruity and other flavors. Relevant analyses showed that the core microbial community was highly correlated with the quality attributes of the fermented products. Microorganisms such as Lactococcus, Weissella, Hanseniaspora, Saccharomyces and Lachancea contributed significantly to the fermented products.

Effects of the Lactiplantibacillus plantarum YB-106 and Leuconostoc mesenteroides YB-23 strains on the quality and microbial diversity of spicy cabbage

Spicy cabbage is a popular fermented vegetable food. The study aimed to determine the physicochemical properties, volatile flavor components, sensory evaluation, and microbial diversity of spicy cabbage prepared using different methods. Three methods were used: single-bacteria fermentation with Lactiplantibacillus plantarum YB-106 and Leuconostoc mesenteroides YB-23, mixed fermentation (LMP) using both strains, and natural fermentation as the blank control (CON). The LMP group has the best quality of spicy cabbage and the highest sensory score. Esters and alkenes were the main volatile flavor components of the spicy cabbage by GC-MS. The fermentation time of LMP group was shorter, and the nitrite degradation rate was >60 %, which was significantly higher than that of other groups (p < 0.05). From the perspective of microbial diversity, the dominant bacteria genera in each group were Lactobacillus, Pantoea, Enterococcus and Pseudomonas. However, mixed fermentation decreased the abundance of pathogenic bacteria, of which the abundance of Serratia was <0.1 %. In conclusion, mixed fermentation can significantly improve the quality of spicy cabbage and shorten the fermentation time. These findings laid the theoretical foundation for the industrial production of high-quality spicy cabbage.

Rheological properties, biochemical changes, and potential health benefits of dehulled and defatted industrial hempseeds after fermentation

Dehulled hempseed (DHS), fermented dehulled hempseed (FDHS), hempseed cake (HSC), and fermented HSC (FHSC) were examined for their phytochemical composition, health benefits, and rheological characteristics. At 500 µg/mL concentration, DHS, FDHS, HSC, and FHSC extracts exhibited the ability to inhibit DPPH radicals, with 32.46 %, 47.35 %, 33.85 %, and 47.41 %, respectively. Similarly, they demonstrated potential to scavenge ABTS radicals by 13.7 %, 27.87 %, 14.40 % and 25.70 %, respectively. For lipase inhibition activity, FDHS (72.92 %) and FDHS (85.89 %) outperformed DHS (52.94 %) and HSC (43.08 %). Furthermore, FHSC enhanced the survival and reduced fat accumulation in glucose-supplemented Caenorhabditis elegans. We used HPLC and UHPLC-ESI-QTOF-MS for metabolite analysis, quantifying eight polyphenols using HPLC and identifying thirty-four metabolites with UHPLC-ESI-QTOF-MS. Generally, metabolomics indicated an improved metabolite profile after fermentation. Fermentation also showed impact on rheological characteristics, modifying viscosity, loss modulus, and storage modulus. These findings collectively demonstrate the ability of fermentation in enhancing overall value of hempseed.

Volatilome, Microbial, and Sensory Profiles of Coffee Leaf and Coffee Leaf-Toasted Maté Kombuchas

Kombucha is a fermented beverage traditionally made from the leaves of Camelia sinensis. The market has drastically expanded recently, and the beverage has become more elaborated with new, healthy food materials and flavors. Pruning and harvesting during coffee production may generate tons of coffee leaves that are discarded although they contain substantial amounts of bioactive compounds, including those found in maté tea and coffee seeds. This study characterized the changes in volatilome, microbial, and sensory profiles of pure and blended arabica coffee leaf tea kombuchas between 3-9 days of fermentation. Acceptance was also evaluated by consumers from Rio de Janeiro (n = 103). Kombuchas (K) were prepared using black tea kombucha starter (BTKS) (10%), sucrose (10%), a symbiotic culture of Bacteria and Yeasts (SCOBY) (2.5%), and a pure coffee leaf infusion (CL) or a 50:50 blend with toasted maté infusion (CL-TM) at 2.5%. The RATA test was chosen for sensory profile characterization. One hundred volatile organic compounds were identified when all infusions and kombucha samples were considered. The potential impact compounds identified in CL K and CL-TM K were: methyl salicylate, benzaldehyde, hexanal, nonanal, pentadecanal, phenylethyl-alcohol, cedrol, 3,5-octadien-2-one, β-damascenone, α-ionone, β-ionone, acetic acid, caproic acid, octanoic acid, nonanoic acid, decanoic acid, isovaleric acid, linalool, (S)-dihydroactinidiolide, isoamyl alcohol, ethyl hexanoate, and geranyl acetone. Aroma and flavor descriptors with higher intensities in CL K included fruity, peach, sweet, and herbal, while CL-TM K included additional toasted mate notes. The highest mean acceptance score was given to CL-TM K and CL K on day 3 (6.6 and 6.4, respectively, on a nine-point scale). Arabica coffee leaf can be a co-product with similar fingerprinting to maté and black tea, which can be explored for the elaboration of potentially healthy fermented beverages in food industries.

Selective influence of garlic as a key ingredient in kimchi on lactic acid bacteria in a fermentation model system

Garlic is an essential ingredient added to kimchi, a fermented vegetable, in small amounts owing to its sensory and antibacterial properties. This study aimed to elucidate the complex relationship between garlic and specific lactic acid bacteria (LAB) and the resulting metabolite changes in a controlled kimchi model system using nine strains as mixed and individual starters. The group without garlic using mixed starters showed the highest LAB growth activity, which influenced lactic acid production, pH, and titratable acidity. The group without garlic also showed differences in the composition of bacteria, such as Latilactobacillus sakei, Levilactobacillus brevis, unclassified Leuconostoc, and Weissella koreensis, during the fermentation period. In addition, the altering patterns of metabolites in the group without garlic during fermentation differed from those in the group with garlic. In addition, the metabolic profile of L. brevis group was mostly different from that of the other strains in the controlled model kimchi system using individual starters, suggesting that changes in LAB composition by garlic could subsequently affect metabolites during fermentation. This study provides valuable insights into the complex interactions among food ingredients, LAB succession, and metabolite production during fermentation.

Effects of ingredient size on microbial communities and metabolites of radish kimchi

In this study, changes in physicochemical characteristics, microbial communities, and metabolites were investigated to identify the fermentation characteristics of radish kimchi according to the size of radish cubes used. The small-sized radish kimchi group showed the highest hardness value and glucose content in the early stages of fermentation. The relative abundance of major lactic acid bacteria, including Leuconostoc, Weissella, and Lactobacillus, was the highest in the small-sized radish kimchi group on day 5 of fermentation, which resulted in rapid production of lactic acid, thereby causing a decrease in pH and an increase in titratable acidity. The size of the radish in kimchi plays a pivotal role in determining various factors, most notably during the first 5 days of fermentation, leading to marked metabolic changes. A total of 17 metabolites, including glucose, sucrose, lactic acid, malic acid, citric acid, and GABA, exhibited significant differences in the small-size radish kimchi group. Interestingly, the sucrose content was higher in the large-sized radish group at the beginning of fermentation. This study revealed that ingredient size can selectively affect the growth of specific microorganisms in an environment where several microorganisms coexist, which could change the quality of radish kimchi.

Characterizing the impact of species/strain-specific Lactiplantibacillus plantarum with community assembly and metabolic regulation in pickled Suancai

To investigate the colonization and impact of the specific Lactiplantibacillus plantarum strains, four isolated strains were applied in pickled Suancai which is a traditional pickled mustard (Brassica juncea). Results showed that strain-8 with the highest lactic acid bacteria (LAB) counts and acetic acid (p < 0.05). There were 11.42 % ∼ 32.35 % differential volatile compounds detected, although nitriles, esters, and acids were predominant. L. plantarum disturbed the microbial community, in which the microbial composition of strain-11 was most similar to the naturally fermented sample. Amino acids, carbohydrate metabolism, and metabolism of cofactors and vitamins were the main functional classes because of the similar dominant microbes (Lactiplantibacillus and Levilactobacillus). The functional units were separated based on NMDS analysis, in which bacterial chemotaxis, amino acid-related units, biotin metabolism, fatty acid biosynthesis, and citrate cycle were significantly different calculated by metagenomeSeq and Benjamin-Hochberg methods (p < 0.05). The contents of most flavor compounds were consistent with their corresponding enzymes. In particular, glucosinolates metabolites were different and significantly related to the myrosinase and metabolic preference of LAB. Therefore, this study revealed the impact mechanism of the specific L. plantarum strains and provided a perspective for developing microbial resources to improve the flavor diversity of fermented vegetables.

Metagenomic analyses reveal microbial communities and functional differences between Daqu from seven provinces

Microbial communities perform the brewing function in Daqu. Macrogenomics and PICRUST II analyses revealed the differences in microbes and metabolic functions among Daqu from the seven Baijiu-producing provinces. Jiang-flavored Daqu (Guizhou, Shandong, and Hubei provinces) generally forms an aroma-producing functional microbiota with Kroppenstedtia, Bacillus, Thermoascus, Virgibacillus, and Thermomyces as the core, which promotes the metabolism of various amino acids and aroma compounds. Light-flavored Daqu (Shanxi Province) enriched the Saccharomycopsis, Saccharomyces, and lactic acid bacteria (LAB) microbiota through low-temperature fermentation. These microbes can synthesize alcohol and lactic acid but inhibit amino acid metabolism within the Light-flavored Daqu. Bifidobacterium and Saccharomycopsis were dominant in the Tao-flavored Daqu (Henan province). This unique microbial structure is beneficial for pyruvate fermentation to lactate. Research also found that Strong-flavored Daqu from Jiangsu and Sichuan provinces differed significantly. The microbial communities and metabolic pathways within Jiangsu Daqu were similar to those within Jiang-flavored Daqu, but Sichuan Daqu was dominated by Thermoascus, LAB, and Thermoactinomyces. In addition, Spearman correlation analysis indicated that Kroppenstedtia, Bacillus, and Thermomyces were not only positively related to flavor metabolism but also negatively correlated with Saccharomycopsis. This research will help establish a systematic understanding of the microbial community and functional characteristics in Daqu.

Effect of headspace gas composition in kimchi packaging on the quality characteristics of kimchi

This study evaluated the effects of gas composition in kimchi packaging on kimchi quality. Completely sealed packaging without gas inflow/outflow during fermentation (S1), packaging allowing gas outflow (S2), and packaging allowing gas inflow and outflow (S3) were used. Microbial composition analysis, volatile compound content analysis, and sensory evaluation were performed to determine the differences in kimchi quality among samples. Metabolites were examined using principal component analysis. Gas composition analysis showed that the ratio of CO2 increased during the storage period in S1, the ratio of nitrogen and CO2 contents was constant in S2, and the ratio of oxygen was significantly higher in S3. No significant differences in the lactic acid bacteria number were observed. However, coliforms were only detected in S3, and yeast and mold proliferated faster in S3 than in S2 or S1. The main compounds detected in S1 and S2 were alcohols, whereas those in S3 were esters such as β-phenethyl acetate produced by yeast. Sensory evaluation showed that S3 had the lowest odor, taste, and overall scores, whereas S2 had the highest. In conclusion, the gas composition inside the kimchi package greatly affects the quality of kimchi. Our findings provide important data that can be useful in the manufacture of commercial kimchi.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05795-z.

Bacteriocin-Producing Enterococcus faecium OV3-6 as a Bio-Preservative Agent to Produce Fermented Houttuynia cordata Thunb. Beverages: A Preliminary Study

Microbial contamination affects the quality of the fermented Houttuynia cordata Thunb. (H. cordata) beverage (FHB). The present study aimed to assess the bio-preservative property of Enterococcus faecium OV3-6 (E. faecium OV3-6) during the production of FHB. The antimicrobial activity against Escherichia coli, Salmonella, Bacillus cereus, and Staphylococcus aureus and the survival of E. faecium OV3-6 were studied. Then, FHB fermentation was performed with different preservatives (non-preservative, E. faecium OV3-6, cell-free supernatant of E. faecium OV3-6, and nisin) with and without representative pathogens. The maximum antimicrobial activity against S. aureus and B. cereus was observed after 18 h of cultivation in an MRS medium. E. faecium OV3-6 was used as a starter to produce the FHB, and the strain survived up to 48 h in the fermented beverage. E. faecium OV3-6 and its cell-free supernatant inhibited the growth of E. coli, Salmonella, B. cereus, and S. aureus in the stimulated FHB. The non-preservatives and nisin-containing FHB showed inhibition against Gram-positive pathogens. The FHB treated with E. faecium OV3-6 was rich in lactic acid bacteria, and the product was at an acceptable level of pH (less than 4.3). Certain limitations were identified in the study, such as lack of nutritional, metabolomics analysis, and safety and consumer acceptability of FHB. The results suggested that E. faecium OV3-6 could be used as a bio-preservative to produce fermented plant beverages (FPBs).

The Impact of Different Cooking Methods on the Flavor Profile of Fermented Chinese Spicy Cabbage

Chinese spicy cabbage (CSC) is a common traditional fermented vegetable mainly made of Chinese cabbage. In addition to eating raw, boiling and stir-frying are the most common cooking methods for CSC. To identify the impacts of boiling or stir-frying on the quality of CSC, the physicochemical properties, flavor compounds, and sensory properties of CSC were analyzed. A total of 47 volatile flavor compounds (VFCs) were detected by gas chromatography-mass spectrometry. Sulfide was determined as the main flavor compound of CSC, mainly contributed by cabbage, garlic, and onion odors. The content of sulfide decreased significantly after cooking. Nonanal, geranyl acetate, and linalool were newly generated after boiling with odor activity value (OAV) > 1, and contributed fatty, sweet, fruity, and floral odors to BL-CSC. 1-Octen-3-one, 1-octen-3-ol, octanal, nonanal, and (E)-2-nonenal were newly generated after stir-frying with OAV > 1, and contributed mushroom, fatty, and green odors to SF-CSC. Diallyl trisulfide, nonanal, (E)-β-ionone, β-sesquiphellandrene, and (E)-2-decenal were considered as the potential key aroma compounds (KACs) to distinguish the CSCs after different heat treatment. After cooking, the total titratable acidity of CSC increased and the sensory properties changed significantly. This study provides valuable information and guidance on the sensory and flavor changes of thermal processing fermented vegetables.

Volatile, Microbial, and Sensory Profiles and Consumer Acceptance of Coffee Cascara Kombuchas

Given the substantial world coffee production, tons of coffee fruit cascara rich in bioactive compounds are discarded annually. Using this by-product to produce potentially healthy and acceptable foods is a sustainable practice that aggregates value to coffee production and may help improve people's lives. This study aimed to elaborate kombuchas from coffee cascara tea, evaluate their microbial profile, and monitor the changes in the volatile profile during fermentation, together with sensory attributes and acceptance by consumers from Rio de Janeiro (n = 113). Arabica coffee cascaras from Brazil and Nicaragua were used to make infusions, to which black tea kombucha, a Symbiotic Culture of Bacteria and Yeasts (SCOBY), and sucrose were added. Fermentation of plain black tea kombucha was also monitored for comparison. The volatile profile was analyzed after 0, 3, 6, and 9 days of fermentation via headspace solid phase microextraction GC-MS. A total of 81 compounds were identified considering all beverages, 59 in coffee cascara kombuchas and 59 in the black tea kombucha, with 37 common compounds for both. An increase mainly in acids and esters occurred during fermentation. Despite the similarity to black tea kombucha, some aldehydes, esters, alcohols, and ketones in coffee cascara kombucha were not identified in black tea kombucha. Potential impact compounds in CC were linalool, decanal, nonanal, octanal, dodecanal, ethanol, 2-ethylhexanol, ethyl acetate, ethyl butyrate, ethyl acetate, β-damascenone, γ-nonalactone, linalool oxide, phenylethyl alcohol, geranyl acetone, phenylacetaldehyde, isoamyl alcohol, acetic acid, octanoic acid, isovaleric acid, ethyl isobutyrate, ethyl hexanoate, and limonene. The mean acceptance scores for cascara kombuchas varied between 5.7 ± 0.53 and 7.4 ± 0.53 on a nine-point hedonic scale, with coffee cascara from three-day Nicaragua kombucha showing the highest score, associated with sweetness and berry, honey, woody, and herbal aromas and flavors. The present results indicate that coffee cascara is a promising by-product for elaboration of fermented beverages, exhibiting exotic and singular fingerprinting that can be explored for applications in the food industry.

Effect of Levilactobacillus brevis as a starter on the flavor quality of radish paocai

The aim of this study was to investigate the effectiveness of Levilactobacillus brevis on the fermentation kinetics and flavor quality of radish paocai. Compared with spontaneous fermentation (SF), the radish paocai of inoculated fermentation (IF) using Levilactobacillus brevis PL6-1 as a starter could rapidly utilize sugar to produce acid, thus accelerating the fermentation process. The texture including hardness, chewiness, and springiness of the IF were all higher than that of the SF, and the IF paocai showed higher L value in color. L. brevis PL6-1 as a starter could increase the final levels of metabolites of mannitol (5.43 mg/g), lactic acid (543.44 mg/100 g) and acetic acid (87.79 mg/100 g). Fifteen volatile organic compounds (VOCs) were identified as key aroma-active compounds in radish paocai and 8 differential VOCs were considered as the potential markers. L. brevis PL6-1 could improve the levels of 1,8-cineole, 1-hexanol, hexanoic acid, 2-methoxy-4-vinylphenol, and eugenol, giving the radish paocai floral, sweet, and sour aroma, and reduce the unpleasant odor of garlic, onion, and pungent, contributed by erucin, diallyl disulfide, and allyl trisulfide. Sensory evaluation results showed that the appearance, taste, texture, and overall acceptability of IF paocai were all better than the SF group. Therefore, L. brevis PL6-1 could be a potential starter to improve the flavor and sensory quality for radish paocai fermentation.

Dynamics changes in physicochemical properties, volatile metabolites, non-volatile metabolites, and physiological functions of barley juice during Bifidobacterium infantis fermentation

The purpose of this research was to explore the potential of Bifidobacterium infantis fermentation to modify the composition and physiological properties of barley juices. B. infantis JFM12 showed a potent capability to decrease the total sugar contents from 0.39 ± 0.01 mg/mL to 0.35 ± 0.01 mg/mL within 24 h of fermentation. The volatile metabolite profiles were enriched after B. infantis JFM12 fermentation, leading to the changes of 13 aldehydes, 11 ketones, 10 acids, 7 alcohols, and 6 esters. A total of 98 key non-volatile metabolites were identified in the barley juice between before and after B. infantis JFM12 fermentation, including 80 non-volatile metabolites that were remarkably increased and 18 non-volatile metabolites that were remarkably reduced. Furthermore, the antioxidant activities and lipase inhibitory activities of fermented barley juice were higher than those of unfermented barley juice. Overall, B. infantis JFM12 was beneficial in increasing the quality of barley juice.

Microbial communities and metabolite profiles during the fermentation of Chinese Dongbei suancai with Chinese baijiu as supplementary material

BACKGROUND

In industrial production of suancai, baijiu is commonly used to inhibit the spoilage bacteria and enhance the flavor. However, the effects of baijiu on the microbial diversity and metabolic pathways of suancai are rarely reported in the literature. This study aimed to explore the microbial community, its predicted functional roles, and the metabolites formed during fermentation of Chinese Dongbei suancai fermented using a mixed starter with Chinese baijiu as supplementary material.

RESULTS

Results showed that Lactobacillus, Enterobacter, and Leuconostoc were the major bacterial genera in the Dongbei suancai fermented by adding baijiu. Linear discriminant analysis effect size indicated that Leuconostoc was the major biomarker in the early stage of fermentation, whereas Lactococcus, Weissella, and Lactobacillus plantarum were biomarkers in the middle and later stages of fermentation. A total of 638 metabolites were detected in suancai fermented by adding baijiu. However, the principal component analysis showed that baijiu significantly affected the metabolites of suancai in the early and later stages of fermentation. Furthermore, 58, 22, and 26 significantly differential metabolites (P < 0.01) were found on day 0, day 2, and day 30 of fermentation respectively. Moreover, Lactobacillus, Lactococcus, and Enterobacter had positive correlations with amino acids, nucleotides, organic acids, alcohols, and esters. Functional analysis implied that carbohydrate, amino acid, energy, and nucleotide metabolism were the major determinants of the characteristics of suancai fermented with baijiu as supplementary material.

CONCLUSION

Baijiu changed the metabolites of inoculated fermented Dongbei suancai. © 2023 Society of Chemical Industry.

Inhibition of Perilla frutescens Essential Oil on Pellicle Formation of Candida tropicalis and Pichia kluyveri and Its Effect on Volatile Compounds in Sichuan Pickles

Pellicle formation is the most typical characteristic of deteriorating fermented vegetable products. Perilla frutescens essential oil (PEO) is widely used as a useful natural preservative. However, few studies have addressed the antifungal activity and mechanism of PEO in pellicle formation microorganisms, and it is still unclear whether it can inhibit pellicle formation and affect its volatile compounds in Sichuan pickles. The current study showed that PEO can inhibit pellicle formation during fermentation of Sichuan pickles as it had significant antifungal activity against the pellicle formation microorganisms Candida tropicalis SH1 and Pichia kluyveri SH2. The minimum inhibitory concentration (MIC) of PEO against C. tropicalis SH1 and P. kluyveri SH2 was determined to be 0.4 μL/mL, and the minimum fungicidal concentrations (MFCs) were 1.6 μL/mL and 0.8 μL/mL, respectively. The antifungal mechanism was activated as a result of damage to the cell membrane, an increase in the cell permeability, a decrease in the mitochondrial membrane potential, and the inhibition of ATPase activity. Meanwhile, the addition of PEO to Sichuan pickles can enrich the profiles of volatile compounds during fermentation, including limonene, myrcene, 1,8-cineole, linalool, perilla ketone, heptanal, hexanal, α-thujone and β-terpineol and thus improve the overall sensory acceptability. These results indicated that PEO has the potential to be used as a novel food preservative to control pellicle formation in fermented vegetables.

Microbiota Succession and Chemical Composition Involved in Lactic Acid Bacteria-Fermented Pickles

Pickles are a type of traditional fermented vegetables in China. To ascertain the effect of different lactic acid bacteria on pickles, the chemical composition characteristics, flavor substances, and bacterial diversity of the pickles fermented by natural bacteria, Lactobacillus plantarum R5, Lactobacillus pentosus R8, and L. plantarum R5 plus L. pentosus R8 were investigated in this study. The results showed that Lactobacillus enhanced the decrease in pH, increase in total acid content, degradation of nitrite, and production of organic acid (lactic acid and malic acid) of fermented pickles. A total of 80 flavors were detected in the pickles fermented for 14 days, and esters in pickles fermented by Lactobacillus were more plentiful. Firmicutes emerged as the predominant microbial phyla. Amongst these, the commonly encountered microorganisms were Lactobacillus, unclassified Enterobacteriaceae, Pantoea, and Weissella. The multivariate statistical analysis further showed that Lactobacillus had a strong negative correlation with pH and a strong positive correlation with malic acid and lactic acid, and the microorganisms in pickles could acclimate to the changing fermentation environment. The insights gained from this study may be of assistance to us in obtaining new insights into the microbiota succession and chemical compounds involved in the pickles fermented by Lactobacillus.

The in-situ dextran produced in rice protein yogurt: Effect on viscosity and structural characteristics

Phase separation is one of the primary quality control issues for plant-based beverages during storage. This study applied the in-situ-produced dextran (DX) from Leuconostoc citreum DSM 5577 to solve this problem. Rice flour milled from broken rice was used as the raw material and Ln. citreum DSM 5577 as the starter to prepare rice-protein yogurt (RPY) under different processing conditions. The microbial growth, acidification, viscosity change, and DX content were first analyzed. Then, the proteolysis of rice protein was evaluated, and the role of the in-situ-synthesized DX in viscosity improvement was explored. Finally, the in-situ-synthesized DXs in RPYs under different processing conditions were purified and characterized. The in-situ-produced DX caused a viscosity increase up to 1.84 Pa s in RPY and played a major role in this improvement by forming a new network with high water-binding capacity. The processing conditions affected the content and the molecular features of DXs, with a DX content up to 9.45 mg/100 mg. A low-branched DX (5.79 %) with a high aggregating ability possessed a stronger thickening ability in RPY. This study may guide the application of the in-situ-synthesized DX in plant protein foods and may promote the utilization of broken rice in the food industry.

The volatile organic compounds and palatability of mixed ensilage of marigold (Tagetes erecta L.) crop residues

With increasing acreage of cash crops, the use of their by-products as supplements for livestock feed becomes an important factor. Marigold (Tagetes erecta L.) account for more than half of the world's loose flower production. However, there is no precedent for the abundantly available marigold crop residue (MCR) being used as feed in agricultural production, probably because of its strong pungent taste. This study aimed to evaluate the biotransformation of the volatile organic compounds (VOCs) of MCR by mixed ensilage and assess its palatability by cattle. Caryophyllene, the most prevalent VOC in MCR, decreased by 29.11% (P < 0.05), 38.85% (P < 0.05), 37.15% (P < 0.05), and 28.36% (P < 0.05) ensilage with corn meal (CM), bran (BR), crop corn (CC), and straw (ST), respectively. The acetic acid content increased by 686.05% (P < 0.05), 1337.21% (P < 0.05), 1244.19% (P < 0.05), and 1795.34% (P < 0.05) after mixed ensilage with CM, BR, CC, and ST, respectively. The total amount of alcoholic VOCs followed an overall increasing trend during mixed storage and 10 new alcohols were obtained. Over seven days, feed intake of mixed ensilage MCR by cattle differed significantly (P < 0.05) among treatments compared with MCR and was highest in MCRCM. Combined with palatability trials, the best MCR feed intake was achieved with MCRCM. The findings shed light on how feed odor can be improved and how degradation of terpenes can be enhanced in practical applications by mixed ensilage.

Rapid Quantitative Analysis of Metabolites in Kimchi Using LC-Q-Orbitrap MS

Kimchi is a traditional Korean salted spontaneous lactic acid bacteria (LAB)-fermented food made using various vegetables. Organic acids, free sugars, and amino acids are key metabolites produced during LAB fermentation that determine the taste and quality of kimchi. However, each metabolite is typically analyzed using an independent analytical method, which is time-consuming and expensive. Therefore, in this study, we developed a method based on LC-Q-Orbitrap MS using which 20 types of representative fermented kimchi metabolites were selected and simultaneously analyzed within 10 min. The established method was validated, and its detection and quantification limits, linearity, precision, and accuracy were found to satisfy the Association of Official Agricultural Chemists (AOAC) validation guidelines. The 20 metabolites were simultaneously extracted from kimchi with different degrees of fermentation and quantitatively analyzed using LC-Q-Orbitrap MS. These results were analyzed using linear discriminant analysis and heat mapping, and the metabolites were grouped into early, middle, and late stages of fermentation. Malic acid (6.518-7.701 mMol) was only present in the initial stage of fermentation, and l-phenylalanine rapidly increased from the middle stage (2.180 mMol) to late stage (4.770 mMol). Lactic acid, which is representative of the sour taste of kimchi, was detected in the middle stage and increased rapidly up to 74.452 mMol in the late stage. In summary, in this study, 20 major kimchi metabolites were accurately analyzed within 10 min and grouped based on the degree of fermentation. Therefore, the method established in this study accurately and rapidly provides information on kimchi consumption and fermentation that could be highly valuable to the kimchi industry and kimchi consumers.

Variations in volatile flavour compounds in Crataegi fructus roasting revealed by E-nose and HS-GC-MS

Introduction

Crataegi fructus (CF) is an edible and medicinal functional food used worldwide that enhances digestion if consumed in the roasted form. The odour of CF, as a measure of processing degree during roasting, significantly changes. However, the changes remain unclear, but are worth exploring.

Methods

Herein, the variations in volatile flavour compounds due to CF roasting were investigated using an electronic nose (E-nose) and headspace gas chromatography-mass spectrometry (HS-GC-MS).

Results

A total of 54 components were identified by GC-MS. Aldehydes, ketones, esters, and furans showed the most significant changes. The Maillard reaction, Strecker degradation, and fatty acid oxidation and degradation are the main reactions that occur during roasting. The results of grey relational analysis (GRA) showed that 25 volatile compounds were closely related to odour (r > 0.9). Finally, 9 volatile components [relative odour activity value, (ROAV) ≥ 1] were confirmed as key substances causing odour changes.

Discussion

This study not only achieves the objectification of odour evaluation during food processing, but also verifies the applicability and similarity of the E-nose and HS-GC-MS.

Detection of the Inoculated Fermentation Process of Apo Pickle Based on a Colorimetric Sensor Array Method

Apo pickle is a traditional Chinese fermented vegetable. However, the traditional fermentation process of Apo pickle is slow, easy to ruin, and cannot be judged with regard to time. To improve fermentation, LP-165 (L. Plantarum), which has a high salt tolerance, acidification, and growth capacity, was chosen as the starter culture. Meanwhile, a colorimetric sensor array (CSA) sensitive to pickle volatile compounds was developed to differentiate Apo pickles at varying degrees of fermentation. The color components were extracted from each dye in the color change profiles and were analyzed using principal component analysis (PCA) and linear discriminant analysis (LDA). The fermentation process of the Apo pickle was classified into four phases by LDA. The accuracy of backward substitution verification was 99% and the accuracy of cross validation was 92.7%. Furthermore, the partial least squares regression (PLSR) showed that data from the CSA were correlated with pH total acid, lactic acid, and volatile acids of the Apo pickle. These results illustrate that the CSA reacts quickly to inoculated Apo pickle and could be used to detect fermentation.

Effect of Starters on Quality Characteristics of Hongsuantang, a Chinese Traditional Sour Soup

Hongsuantang (HST) is a traditional Chinese and famous sour soup. However, the quality of naturally fermented HST is not controllable. We investigated the effects of different lactic acid bacteria starters on HST acid production, color, antioxidant capacity, total phenols, total carotenoids, organic acids, volatile substances, and sensory properties to determine the most suitable strain for HST production. The results showed that among the seven lactic acid bacteria strains used to inoculate fermented HST, Lactiplantibacillus plantarum SQ-4 exhibited the most excellent fermentation characteristics. SQ-4 rapidly reduced the HST’s pH by 0.77. It significantly increased the HST’s color, organic acids, total phenols, carotenoids, lycopene, and free radical scavenging ability. Lactiplantibacillus plantarum SQ-4 was an excellent starter for preparing HST with good acid production capacity, moderate sourness and spiciness, and good sensory and other characteristics. Each starter produces its distinct flavor components. α-Pinene, myrcene, α-copaene, and guaiol were vital aroma compounds in HST fermentation by the starter. This study laid a foundation for selecting HST starters and potential industrial production.

Real-Time Monitoring the Effects of Storage Conditions on Volatile Compounds and Quality Indexes of Halal-Certified Kimchi during Distribution Using Electronic Nose

The food logistics system is an essential sector for maintaining and monitoring the safety and quality of food products and becoming more crucial, especially during and after the pandemic of COVID-19. Kimchi is a popular traditional fermented food originally from Korea and easily changes because of the storage conditions. This study aims to evaluate the effects and the contributions of temperature to volatile compounds, quality indexes, and the shelf life of Halal-certified Kimchi, and to identify alcohol and find the correlation between the identified variables using an electronic nose and conventional method with the integration of multivariate analysis. Thirty-two volatile compounds (VOCs) were detected and correlated with pH, titratable acidity (TA), and lactic acid bacteria (LAB) counts during storage time. Ethanol was also found in the ripened Kimchi and possibly became the critical point of halal Kimchi products besides total acidity, pH, and LAB. Furthermore, the correlation between pH and benzaldehyde, titratable acidity and 3-methylbutanoic acid, and among lactic acid bacteria with ethanol, acetic acid, ethyl acetate, and 3-methylbutanoic acid properly can be used as a given set of variables in the prediction of food quality during storage and distribution.

Flavour Generation during Lactic Acid Fermentation of Brassica Vegetables—Literature Review

Fermentation is a method of food preservation that has been used for centuries. Lactic acid fermentation, apart from extending the shelf-life of vegetables, affects significantly the flavour of food products. In this review, the formation of flavour, including both taste and aroma, in fermented Brassica vegetables is summarized. The flavour-active compounds are generated in various metabolic pathways from many precursors present in raw materials used for fermentation. In Brassica vegetables, a unique group of chemicals, namely glucosinolates, is present, which significantly influence the flavour of fermented products. In this summary, we took a closer look at the flavour of two of the most commonly eaten worldwide fermented Brassica products, which are sauerkraut and kimchi. Finally, the needs and directions for future studies were addressed.

Functional Fermented Probiotics, Prebiotics, and Synbiotics from Non-Dairy Products: A Perspective from Nutraceutical

The current trend of health-conscious consumers and healthy food habits prompts researchers to explore developing food products with synbiotic benefits. Synbiotic foods have gained popularity in recent years due to their functional, nutritional, physiological, and therapeutic characteristics. Lactose intolerance, dyslipidemia, and allergic milk proteins become the barriers in the development of dairy probiotics. The present scenario of an increase in the demand for vegetarian products leads to a rise in the consumption of non-dairy probiotics. Prebiotics like, resistant starch, inulin, and polyphenols are selectively used by gut microbiota to enhance the selection and colonization of probiotics bacteria. Probiotic's action mechanisms include the production of bacteriocins, peptides, short-chain fatty acids, amino acids, vitamins, and other metabolites. Therefore, this review article explores the alternative sources of probiotics so it will help to an understanding of non-dairy based functional fermented foods for both pro and prebiotics. Dietary fibers in vegetables, fruits, and cereals are one of prospective prebiotics and highlighted the various methods for making non-dairy synbiotics based on dietary fibers, such as microencapsulation, freeze-drying, and spray drying is also addressed.

Tetracycline residue alters profile of lactic acid bacterial communities and metabolites of ginger pickle during spontaneous fermentation

Antibiotic residue, an emerging contaminant, has been an increasing concern worldwide in vegetables. However, the focus is still limited to its accumulation in vegetables and its adverse health effect on humans, with little mention of its impact on the vegetable process. Fermentation is an important method of the vegetable process. Tetracycline (TC) is the most widely used antibiotic, and its residue is often higher than other antibiotics in ginger. Therefore, current research was to characterize how the TC residue affected the lacticacidbacterial (LAB) communities and metabolites during the salted fermentation of ginger. The TC residue, organic acids, volatile compounds and LABs were analyzed during the fermentation, and the correlations between the LABs and compounds were also revealed. The results suggested that the hetero-lactic fermentation did not happen under the TC residue although the TC residue decreased from 4 mg/kg to 2.56 mg/kg in salt brine of ginger fermentation. Meanwhile, TC residue affected the occurrence, propagation and succession of LABs. The LAB biomarkers shifted to Lab. parafarraginis, Lab. buchneri and Lab. kisonensis under TC residue. Responded to LAB communities, the organic acids and volatile compounds were also markedly changed under the TC residue. And the important volatile compound variables shifted to citronellol, allylsenevol, geranyl acetate, vinylstearylether, isothiocyanic acid phenethyl, 3-octanol, geraniol, bingpian, citral and camphor. The transformation of LAB biomarkers induced by TC residue was the main cause of the change of important volatile compound variables, but interestingly, not all of them had significant positive or negative correlations. These results indicated that the antibiotic residue has an adverse ecological effect on the vegetable fermentation process.Therefore, the antibiotic residue should be listed as a quality control index in fermented vegetable raw materials.

Bioactive Properties, Volatile Compounds, and Sensory Profile of Sauerkraut Are Dependent on Cultivar Choice and Storage Conditions

Sauerkraut is produced by cabbage fermentation either spontaneously or by adding lactic acid bacteria. Although commercial cabbage cultivars are more desirable due to their higher yield and uniformity, traditional cultivars are highly prized for their unique sensory characteristics and suitability for fermentation. The aim of this study was to investigate the properties of sauerkrauts from traditional cabbage cultivars ('Brgujski' and 'Žminjski') compared to commercial samples, and to unravel the effects of ambient (18 °C) and cold storage (4 °C) on sauerkraut properties. Higher total phenolic contents and total antioxidant capacities measured by both FRAP and DPPH methods were observed for sauerkrauts from traditional cultivars. In total, 32 volatile compounds were identified, and differences in the volatile profile were observed among the investigated sauerkrauts. The sensory properties of traditional cabbage cultivars were on par, or even better, compared to those of commercially available sauerkraut products. The cold storage conditions characteristic of commercial environments preserved the total antioxidant capacity, the red to green color ratio (a), as well as the lightness (L) of sauerkraut compared to the ambient temperatures characteristic of domestic conditions, indicating the preservation of bioactive compounds responsible for the purple cabbage head coloration of the investigated traditional cultivars.

Effect of Fermentation Duration on the Quality Changes of Godulbaegi Kimchi

Fermentative and antioxidative characteristics of Godulbaegi kimchi (LGK), a traditional, fermented Korean food, were conducted. For the study, LGK kimchi was made of Godulbaegi kimchi with pepper powder, salted shrimp, refined salt, green onions, and so on, and fermented at 5C for 6 months. The pH was decreased, and total acidity was increased during fermentation. Furthermore, lactic acid bacteria and yeast were increased, while the total viable count was decreased. The LGK showed the highest DPPH-scavenging activity, phenol content, and nitrite-scavenging activity with methanol extract among methanol, ethanol, and water. In addition, we screened strains among LGK kimchi with high antimicrobial activity and isolated them. We tested antimicrobial activity for 20 lactic acid bacteria, and we separated and identified nine strains of lactic acid bacteria with high antimicrobial activity. Given these results, LGK is expected to be an effective food in considerable antioxidative activity with an antimicrobial effect. These results are expected to serve as basic data for the study of Godulbaegi kimchi.

Immunomodulatory Activity of Extracellular Vesicles of Kimchi-Derived Lactic Acid Bacteria (Leuconostoc mesenteroides, Latilactobacillus curvatus, and Lactiplantibacillus plantarum)

Lactic acid bacteria present in Kimchi, such as Leuconostoc mesenteroides (Lm), Latilactobacillus curvatus (Lc), and Lactiplantibacillus plantarum (Lp) produce extracellular vesicles (ECVs) that modulate immune responses. The ECVs of probiotic Kimchi bacteria are abbreviated as LmV, LcV, and LpV. Treatment of macrophages (RAW264.7) with ECVs (LmV, LcV, and LpV) increased the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, and interleukin-6 (IL-6). Immunostimulatory effects exerted on the RAW264.7 cells were stronger after treatments with LmV and LcV than with LpV. Treatment of mice with LcV (1 mg/kg, orally) induced splenocyte proliferation and subsequent production of both NO and cytokines (INF-γ, TNF-α, IL-4, and IL-10). Furthermore, pre-treatment of macrophages and microglial cells with ECVs prior to LPS stimulation significantly attenuated the production of NO and pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6). Therefore, ECVs (LmV, LcV, and LpV) prevent inflammatory responses in the LPS-stimulated microglial cells by blocking the extracellular signal-regulated kinase (Erk) and p38 signaling pathways. These results showed that LmV, LcV, and LpV from Kimchi probiotic bacteria safely exert immunomodulatory effects.

Influence of Salinity on the Microbial Community Composition and Metabolite Profile in Kimchi

Kimchi, a popular traditional Korean fermented food, is produced by fermenting vegetables with various spices and salt. Salt plays an important role in the preparation of kimchi and affects its taste and flavor. This study aimed to investigate the effects of salinity on kimchi fermentation. The salinities of five sets of kimchi samples were adjusted to 1.4%, 1.7%, 2.0%, 2.2%, and 2.5%. The characteristics of each kimchi sample, including its pH, acidity, free sugar content, free amino acid content, organic acid content, and microbial community composition, were evaluated during kimchi fermentation. The low-salinity kimchi sample showed a rapid decline in the pH at the beginning of the fermentation process, a relatively high abundance of Leuconostoc mesenteroides, and high mannitol production. In the late fermentation period, Latilactobacillus sakei had a higher abundance in the kimchi sample with high salinity than in other samples. In the initial stage of fermentation, the metabolite composition did not differ based on salinity, whereas the composition was considerably altered from the third week of fermentation. The findings showed variations in the characteristics and standardized manufacturing processes of kimchi at various salt concentrations. Therefore, salinity significantly affected the types and concentrations of fermentation metabolites in kimchi.