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Lactic acid bacteria (LAB) are frequently used in meat fermentation, and mixed stater cultures are reported to perform better than single ones. Lactiplantibacillus plantarum 3-19 and Pediococcus pentosaceus 18-1 were chosen from 28 sour-meat-origin strains to examine the effects of single and combined inoculation on sour meat quality. Natural fermentation was used as a control to investigate changes in pH, water activity (a w ), amino acid nitrogen (AN), texture, microbial diversity, and volatile organic compounds (VOCs) during fermentation. The pH and a w of each inoculation group were significantly decreased, and AN content was significantly increased. The inoculation of P. pentosaceus 18-1 significantly reduced putrescine, cadaverine, and tryptamine content (p < 0.05), while the inoculation of Lpb. plantarum 3-19 significantly reduced cadaverine amounts (p < 0.05). At the fermentation endpoint, the total biogenic amines content in the C group was 992.96 ± 14.07, which was 1.65, 2.57, and 3.07 times higher than that in the Lp, Pe, and M groups, respectively. The mixed inoculation group combined the advantages of both strains and decreased total biogenic amines most significantly. At the end of fermentation, the VOCs in C, Lp, Pe, and M groups were 10.11, 11.56, 12.45, and 13.39 times higher than those at the beginning of fermentation. Inoculation promoted the production of key VOCs (OAV > 2000) such as heptanal, octanal, and (E)-2-nonanal. The mixed inoculation group had the highest variety and content of VOCs and the highest content of the above key VOCs, significantly enhancing its fruity, floral, ester, and other aromas. Sensory evaluation indicated that the M group had the best overall acceptability. Finally, it was suggested that a combination of Lpb. plantarum 3-19 and P. pentosaceus 18-1 is a novel and efficient starter culture for processing sour meat since they lower the amounts of biogenic amines in the meat and promote the production of VOCs., Competing Interests: Declaration of competing interest The authors confirm that they have no conflicts of interest with respect to the work described in this manuscript., (Copyright © 2024. Published by Elsevier B.V.)

The Amadori rearrangement products are an important flavor precursor in the Maillard reaction. Its thermal decomposition products usually contribute good flavors in foods. Therefore, investigating the thermal breakdown of Amadori products is significant for understanding the flavor forming mechanism in the Maillard reaction. In this study, volatiles from thermal decomposition of Amadori products in cysteine and glucose Maillard reaction was investigated by a thermal desorption cryo-trapping system combined with gas chromatography-mass spectrometry (GC-MS). A total of 60 volatiles were detected and identified. Meanwhile, the forming mechanism of 2-methylthiophene, a major decomposition product, was also investigated by using density functional theory. Seventeen reactions, 12 transition states, energy barrier and rate constant of each reaction were finally obtained. Results reveal that it is more likely for Amadori products of cysteine and glucose to undergo decomposition under neutral or weakly alkaline conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Decanal is one of the main products of lipid oxidation. It has been shown that decanal can oxidize to form volatiles with shorter carbon chains during heating, but the mechanism is still unclear. In this study, volatile compounds formed in the decanal thermal oxidation were verified using thermal-desorption cryo-trapping combined with GC-MS. A total of 32 volatile compounds were identified. The oxidation mechanism of decanal was studied by applying density functional theory. Results revealed that the carbonyl carbon atom was the thermal oxidation site of decanal and two pathways of peroxide oxidation were determined: the ortho‑carbon and the meta‑carbon oxidation. The ortho‑carbon oxidation pathway is superior to the occurrence of the meta‑carbon oxidation pathway. The oxidative mechanism of decanal was finally summarized as the peroxide oxidation based on radical attack on the carbonyl carbon, which would provide a theoretical basis for exploring the oxidation mechanism of other saturated aldehydes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Unsaturated fatty aldehydes are the main products of fatty acid oxidation, and could be further oxidized to form volatile compounds with shorter carbon chains. Therefore, studying the oxidation of unsaturated fatty aldehydes is an important way to reveal the mechanism of food flavor formation during heating. In this study, volatile profiling of (E)-2-decenal during heating was firstly investigated by using thermal-desorption cryo-trapping combined with gas chromatography-mass spectrometry (GC-MS). A total of 38 volatile compounds were detected. Then, twenty-one reactions in the heating process of (E)-2-decenal were obtained by using density functional theory (DFT) calculations, and grouped into three oxidation pathways, namely, peroxide pathway, peroxyl radical pathway and alkoxy radical pathway. Meanwhile, the priority of these three pathways was the alkoxy radical reaction pathway > peroxide pathway > peroxyl radical reaction pathway. Moreover, the calculated results agreed well with the experimental results., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Saccharomyces cerevisiae is commonly used as a starter culture for alcoholic beverages but is less applied in meat products. In this study, the effects of S. cerevisiae LXPSC1 on sour meat during fermentation were investigated. It was found that samples inoculated with S. cerevisiae LXPSC1 (Sc group) had better sensory characteristics and higher levels of pH, ethanol, free amino acids (FAAs), volatile organic compounds (VOCs). The bacterial communities of both groups were dominated by Lactobacillus sakei, Weissella hellenica, and Lactobacillus plantarum, which might play a role in reducing pH and a w and increasing the content of lactic acid, FAAs, and esters. However, Candida zeylanoides and S. cerevisiae were the dominant fungi in the control group and Sc group, respectively. Moreover, S. cerevisiae was positively related to esters, alcohols, ethanol and total VOCs. Overall, S. cerevisiae LXPSC1 might be regarded as a desirable starter culture for improving product quality., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Comprehensive metabolite analysis was carried out by gas chromatography combined with mass spectrometry to investigate the time-dependent metabolic changes during wheat dough heating. Thirty-five volatile metabolites comprising alcohols, ketones, aldehydes, aromatic compounds, furans, acids and esters were identified. Sixty-four non-volatile metabolites, which covered a broad spectrum of polar and non-polar constituents, were also identified and quantified. Results showed that the content of most volatile metabolites increased during heating. Meanwhile, the levels of non-volatile polar metabolites, such as sugar and amino acid, increased and the levels of non-volatile non-polar metabolites decreased or remained constant, including fatty acid methyl ester and free fatty acids. PCA results demonstrated that metabolic changes could be reflected by time-dependent shifts in the PCA loading scores during heating. Analysis of the loadings further showed that most volatile metabolites and non-volatile polar metabolites were the major contributors of the heating time-driven changes during heating. Furthermore, lipid oxidation mainly occurred in the residues of oleic acid and linoleic acid of triglycerides., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Flavourzyme is known to promote protein decomposition, resulting in more peptides and amino acids which can improve the quality of fermented foods. In this study, the effects of flavourzyme addition on the fermentation of Suanzhayu fish were investigated. The results showed that the addition of 50 U/g flavourzyme reduced the water activity (a w ) of products and promoted the release of trichloroacetic acid (TCA)-soluble peptides and free amino acids (FAAs). Thus, the stability of the product was improved and its nutritional value was increased. In addition, with the addition of flavourzyme, Lactobacillus and Saccharomyces more quickly became the dominant genera in the fermentation. Furthermore, the formation of alcohols, aldehydes, and esters was promoted in flavourzyme addition group. Redundant analysis (RDA) indicated that Lactobacillus and Lactococcus play important roles in the formation of flavors, especially for the characteristic flavors of Suanzhayu. Flavourzyme addition may be a novel method to greatly improve the properties of Suanzhayu and shorten the fermentation time., Competing Interests: Declaration of competing interest The authors have no conflict of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Suancai, a popular traditional fermented cabbage in northeast China, is commonly prepared by the spontaneous fermentation process at a certain salt concentration. The salt can affect the metabolites by affecting the microorganisms during Suancai fermentation. The bacterial community and volatile flavor compounds in commercial Suancai from different regions of Northeastern China at different salt concentrations were investigated using next-generation sequencing and GC-MS. Firmicutes and Cyanobacteria were the dominant phyla in the commercial Suancai, and Lactobacillus, Pediococcus, and Leuconostoc were the dominant genera. Among them, Lactobacillus and Pediococcus were considered as the biomarkers of the low and high salt Suncai, respectively. Eighty-five volatile flavor compounds were detected, and HS exhibited higher contents of volatile flavor compounds than LS. Based on the results of correlation analysis, Pediococcus were highly correlated with the alcohols and nitriles in Suancai. The contents of alcohols and nitriles significantly increased in the Suancai, fermented by Pediococcus pentosaceus. The co-inoculated fermentation of Lactobacillus plantarum and P. pentosaceus could increase the concentrations of alcohols, esters, aldehydes, hydrocarbons, and nitriles in Suancai. This study provides a perspective for understanding the ecology of Suancai fermentation and facilitating the fermentation with multispecies inoculation fermentation at an appropriate salt concentration., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The development of ultra-fast response semiconductor gas sensors for high-accuracy detection of trace volatile organic compounds in human exhaled breath still remains a challenge. Herein, we propose a novel self-assembly synthesis concept for preparing intricate three-dimensional (3D) opal porous (OP) SnO 2 -ZnO hollow microspheres (HM), by employing sulfonated polystyrene (S-PS) spheres template-assisted ultrasonic spray pyrolysis. The high gas accessibility of the unique opal hollow structures resulted in the existence of 3D interconnection and bimodal (mesoscale and macroscale) pores, and the n-n heterojunction-induced change in oxygen adsorption. The 3D OP SnO 2 -ZnO HM sensor exhibited high response and ultra-fast dynamic process (response time ∼4 s and recovery time ∼17 s) to 1.8 ppm acetone under highly humid ambient condition (98% relative humidity), and it could rapidly identify the states of the exhaled breath of healthy people and simulated diabetics. In addition, the rational structure design of the 3D OP SnO 2 HM enables the ultra-fast detection (within 1 s) of ethanol in simulation drunk driving testing. Our results obtained in this work provided not only a facile self-assembly approach to fabricate metal oxides with 3D OP HM structures but also a new methodology for achieving noninvasive real-time exhaled breath detection.

Background: Exposure of plants to herbivore-induced plant volatiles (HIPVs) alters their resistance to herbivores. However, the whole-genome transcriptional responses of treated plants remain unknown, and the signal pathways that produce HIPVs are also unclear., Methodology/principal Findings: Time course patterns of the gene expression of Arabidopsis thaliana exposed to Lima bean volatiles were examined using Affymetrix ATH1 genome arrays. Results showed that A. thaliana received and responded to leafminer-induced volatiles from Lima beans through up-regulation of genes related to the ethylene (ET) and jasmonic acid pathways. Time course analysis revealed strong and partly qualitative differences in the responses between exposure at 24 and that at 48 h. Further experiments using either A. thaliana ET mutant ein2-1 or A. thaliana jasmonic acid mutant coi1-2 indicated that both pathways are involved in the volatile response process but that the ET pathway is indispensable for detecting volatiles. Moreover, transcriptional comparisons showed that plant responses to larval feeding do not merely magnify the volatile response process. Finally, (Z)-3-hexen-ol, ocimene, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene triggered responses in A. thaliana similar to those induced by the entire suite of Lima bean volatiles after 24 and 48 h., Conclusions/significance: This study shows that the transcriptional responses of plants to HIPVs become stronger as treatment time increases and that ET signals are critical during this process.

Strong-flavor Daqu, as a fermentation agent, plays a significant role in shaping the quality of strong-flavor baijius, and fungal species in Daqu are important factors affecting the quality of Daqu. Therefore, we selected strong-flavor Daqu from seven different origins to study the fungal composition and the effects of the fungal composition on the physicochemical properties and volatile organic compounds (VOCs). It was found that the fungal composition influences the physicochemical properties of Daqu. Specifically, there was a positive link between Rhizomucor, Rhizopus, Thermomyces, and liquefying activity and a positive correlation between Aspergillus and fermenting activity. Furthermore, the relationships between esterifying activity and Thermomyces, Rhizomucor, Aspergillus, Pichia, and Saccharomycopsis were found to be positive. The VOCs in Daqu were affected by Aspergillus, Issatchenkia, Pichia, and Thermoascus. Issatchenkia was significantly positively correlated with benzeneethanol as well as Aspergillus and pentadecanoic acid ethyl ester, ethyl myristate. Pichia and Thermoascus were significantly negatively correlated with benzaldehyde and 2-furaldehyde. This study deepens our understanding of the relationship between VOCs, the physicochemical properties with microbial communities, and reference significance for the production of better-quality strong-flavor Daqu. [ABSTRACT FROM AUTHOR]

Ethyl carbamate (EC), a 2A carcinogen produced during the fermentation of foods and beverages, primarily occurs in distilled spirits. Currently, most studies focus on strategies for EC mitigation. In the present research, we aimed to screen strains that can degrade EC directly. Here, we report two Candida ethanolica strains (J1 and J116), isolated from fermented grains, which can reduce EC concentrations directly. These two yeasts were grown using EC as the sole carbon source, and they grew well on different carbon sources. Notably, after immobilization with chitosan, the two strains degraded EC in Chinese Baijiu by 42.27% and 27.91% in 24 h (from 253.03 ± 9.89 to 146.07 ± 1.67 and 182.42 ± 5.05 μg/L, respectively), which was better than the performance of the non-immobilized strains. Furthermore, the volatile organic compound content, investigated using gas chromatography-mass spectrometry, did not affect the main flavor substances in Chinese Baijiu. Thus, the yeasts J1 and J116 may be potentially used for the treatment and commercialization of Chinese Baijiu. [ABSTRACT FROM AUTHOR]

Summary: The present study evaluated the relationship between the bacterial diversity and metabolites of various sour meats, a traditional fermented meat product. The results showed that sour meats had a low pH (average of 4.34), low water activity (aw, an average of 0.917), and high lactic acid (~19 177.48 mg kg−1) and free amino acid (FAA) (~4047.65 mg kg−1) concentrations. The lactic acid bacteria (LAB), especially Lactobacillus and Weissella, were predominated in the samples. The alcohols, aldehydes and esters accounted for the major components of volatile organic compounds (VOCs). Of which, (E)‐2‐octenal, nerol, cis‐4‐decenal, tetradecanal, linalyl acetate, linalool, 1‐octen‐3‐ol, hexanal, 1‐heptanol, benzaldehyde and (E)‐2‐decenal were considered as the key VOCs of sour meats. The redundancy analysis (RDA) and Pearson's correlation analysis revealed that LAB (Lactobacillus and Weissella) and salt were positively correlated with most FAAs and VOCs. Overall, higher salinity, lower aw and abundant LAB might be the indicators of good sour meat quality. [ABSTRACT FROM AUTHOR]