Construction of a dynamic model to predict the growth of Staphylococcus aureus and the formation of enterotoxins during Kazak cheese maturation.

Staphylococcus aureus is a common pathogen found in cheese whose Staphylococcal enterotoxins (SE) are the main pathogenic factors that cause food poisoning. The objective of this study was to construct two models to evaluate the safety of Kazak cheese products in terms of composition, changes in S. aureus inoculation amount, Aw, fermentation temperature during processing, and growth of S. aureus in the fermentation stage. A total of 66 experiments comprised of five levels of inoculation amount (2.7-4 log CFU/g), five levels of Aw (0.878-0.961), and six levels of fermentation temperature (32-44 °C) were performed to confirm the growth of S. aureus and the presence of SE limit conditions. Two artificial neural networks (ANN) successfully described the relationship between the assayed conditions and the growth kinetic parameters (maximum growth rates and lag times) of the strain. The good fitting accuracy (R2 values were 0.918 and 0.976, respectively) showed that the ANN was appropriate. Experimental results showed fermentation temperature had the greatest influence on the maximum growth rate and lag time, followed by the Aw and inoculation amount. Furthermore, a probability model was built to predict the production of SE by logistic regression and neural network under the assayed conditions, which proved to be concordant in 80.8-83.8% of the cases with the observed probabilities. The maximum total number of colonies predicted by the growth model in all combinations detected with SE exceeded 5 log CFU/g. Within the range of variables, the minimum Aw for predicting SE production was 0.938, and the minimum inoculation amount for predicting SE production was 3.22 log CFU/g. Additionally, as competition between S. aureus and lactic acid bacteria (LAB) occurs in the fermentation stage, higher fermentation temperatures are conducive to the growth of LAB, which can reduce the risk of S. aureus producing SE. This study can help manufacturers to make decisions on the most appropriate production parameters for Kazak cheese products and to prevent S. aureus growth and SE production.

Probiotic potential of γ-aminobutyric acid (GABA)-producing yeast and its influence on the quality of cheese.

Kazakh cheese is a traditional dairy product in Xinjiang, China. To study the function and potential probiotic characteristics of yeast in Kazakh cheese and its contribution to cheese fermentation, we screened the γ-aminobutyric acid (GABA)-producing yeasts Pichia kudriavzevii 1-21, Kluyveromyces marxianus B13-5, Saccharomyces cerevisiae DL6-20, and Kluyveromyces lactis DY1-10. We investigated the potential probiotic properties of these strains and their use in cheese fermentation (cheeses designated CSP, CSM, CSS, and CSI, respectively); a control with no added yeast was designated CS. The results showed that the 4 yeast strains all showed high self-polymerization (2- and 24-h autoaggregation capacity of >80 and 90%, respectively), hydrophobicity (40-92% variation, low hydrophobicity in xylene, but within the range of probiotics), and the ability to survive the gastrointestinal tract (survival rate >75% after simulation), indicating the probiotic ability of the strains in vitro. The GABA production capacity of the CSM cheese increased (to 95.6 mg/100 g), but its protein content did not change significantly, and amino acid degradation was obvious. The GABA production capacity of the CSS cheese decreased (to 450 mg/kg); its protein content declined, and its amino acid content increased. Except for water and protein, we found no obvious differences in most physical and chemical indicators. Kluyveromyces marxianus B13-5 helped to form the desired texture. Multivariate statistical analysis showed that fermentation of the cheese with the 4 yeasts improved the production of esters and alcohols. The CSS cheese had good aroma production performance, because S. cerevisiae DL6-20 produced high concentrations of isoamyl alcohol, hexanoic acid ethyl ester, benzyl alcohol, octanoic acid ethyl ester, 3-hydroxy-2-butanone, and hexanoic acid; the content of 2-methyl-propanoic acid was low. Compared with the CSP cheese, the CSI and CSM cheeses had a fruitier aroma and a milder odor, but the CSI and CSM cheeses had high concentrations of ethyl acetate, butanoic acid, ethyl ester, 3-methyl-1-butanol-acetate, ethyl hexanoate, ethyl octanoate, acetic acid 2-phenylethyl ester, and ethyl lactate; concentrations of 3-methyl-butanoic acid, propanoic acid, acetic acid, and butanoic acid were low. The CSP cheese had stronger acid-producing ability. The order of fragrance production performance was CSS > CSI, CSM > CSP > CS. Research into the fermentation mechanisms of GABA-producing yeast in cheese will provide a theoretical basis for the quality control and industrial production of Kazakh cheese.

Identification and characterization of antioxidant peptides from Chinese dry-cured mutton ham.

BACKGROUND: Chinese mutton ham is a dry-cured meat product with a long ripening time. The aim of this study was to identify and characterize antioxidant peptides from Chinese mutton ham. RESULTS: Mutton ham peptides (MHPs) were purified by gel filtration, anion exchange and reversed-phase high-performance liquid chromatography steps. The 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free radical scavenging capacity was used to guide the purification of MHPs. Three antioxidant peptides were identified by liquid chromatography with tandem mass spectrometry (LC-MS/MS) as Met-Trp-Thr-Asp (MWTD), Ala-Pro-Tyr-Met-Met (APYMM) and Phe-Trp-Ile-Ile-Glu (FWIIE), with molecular weights 551.61, 611.76, and 706.84 Da, respectively. Among them, APYMM exhibited the highest ABTS radical scavenging activity. The three peptides had the ability to inhibit lipid oxidation and Fenton's reagent-induced protein oxidation and DNA damage. After simulated gastrointestinal digestion, FWIIE and APYMM showed increased antioxidant activity, while MWTD showed decreased activity. CONCLUSION: Three novel peptides isolated from Chinese mutton ham had strong biological activity. Chinese mutton ham is potentially a functional food and an excellent source of natural antioxidants. © 2019 Society of Chemical Industry.

Isolation and characterization of a novel lectin with mitogenic activity from Pleurotus ferulae.

Lectins are the tools for the determination of sugar chain structure. Recently, lectin arrays have become a popular new technology; therefore, lectins with specific sugar-binding properties are required. The objective of the study was to isolate a novel lectin from Pleurotus ferulae mushrooms and characterize its various biological activities. A novel lectin was extracted with deionized water, precipitated from the aqueous extract using 75% saturated (NH4)2SO4, and subjected on DEAE-cellulose followed by affinity chromatography on sepharose-6B. The activity was tested using hemagglutination assays, and carbohydrate-binding specificity was determined by glycan microarray analysis. Its effects on the mitogenic activity of mouse splenocytes were determined by MTT assay. The novel lectin was adsorbed on ion-exchange chromatography DEAE-cellulose and shown as a band with the molecular mass of 17.5 kDa on a SDS-PAGE and as a single 35.0-kDa peak in gel filtration on Superdex G-75. The hemagglutinating activity of the lectin was inhibited by D-glucose, lactose, D-galactose, and galactosamine. The lectin was stable on 60°C. The hemagglutinating activity of lectin was reduced by 50% at 70°C. At 80°C, it was further reduced to 6.25% of its original activity. The hemagglutinating activity was the highest at pH 6-9. Moreover, its hemagglutinating activity was inhibited by Mg2+ and Ca2+ ions. The lectin isolated from P. ferulae in the current study possessed highly potent hemagglutinating and proliferative activities toward mouse splenocytes.

Effect of low-frequency ultrasound-assisted acid extraction on gel properties and structural characterization of sheep's hoof gelatin.

In this study, we investigated the effects of various low-frequency ultrasound-assisted extraction processes, including ultrasound-assisted acid-soaked water bath extraction (UAW), ultrasound-assisted water bath extraction after acid soaking (AUW), acid-soaked water bath extraction followed by ultrasonics (AWU), and acid-soaked water bath extraction without ultrasound (CON), on the structural properties, thermal stability, gel properties, and microstructure of sheep's hoof gelatin. The results revealed that the primary components of sheep's hoof gelatin consisted of α1-chain, α2-chain (100-135 kDa), and ß-chain. In addition, it was observed that among the three sonication groups, sheep's hoof gelatin extracted in the AUW group exhibited the highest yield (27.16 ± 0.41 %), the best gel strength (378.55 ± 7.34 g), and higher viscosity at the same shear rate. The gelling temperature (25.38 ± 0.45 °C) and melting temperature (32.28 ± 0.52 °C) of sheep's hoof gelatin in the AUW group were significantly higher than those in the other groups (p > 0.05). Moreover, our experiments revealed that the sequence of low-frequency ultrasonic pretreatment processes was a crucial factor influencing the gel properties and structural characteristics of sheep's hoof gelatin. Specifically, the acid treatment followed by the ultrasound-assisted approach in the AUW group yielded high-quality and high-yield sheep's hoof gelatin.

Assessing the structural and foaming property changes in egg yolk proteins due to malondialdehyde: Experimental and molecular docking studies.

This study evaluated the effects of varying levels of malondialdehyde (MDA) on the structural and foaming properties of the egg yolk proteins (EYPs), and the interaction between them was explored by molecular docking. The results showed that oxidative modification due to MDA increased the carbonyl content of EYPs by 4.49 times. Simultaneously, the total sulfhydryl content was reduced by 21.47%, and the solubility of EYPs was significantly decreased (p < 0.05). Continuous oxidation disorders the previously ordered structure of EYPs. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that some proteins underwent crosslinking and aggregation with increased MDA oxidation, aligning with changes in particle size and zeta-potential. Moderate oxidation (<1 mmol/L) enhanced the foaming capacity and foam stability of EYPs. Additionally, molecular docking results uncovered favorable interactions between MDA and specific EYPs, primarily through hydrogen bonding. This research offers valuable insights into managing the functional and quality changes of yolk products during processing.

Gelatin/polyvinyl alcohol films loaded with doubly stabilized clove essential oil chitosomes: Preparation, characterization, and application in packing marinated steaks.

In this study, a promising active food-packaging film of Gelatin/polyvinyl alcohol (GEL/PVA) integrated with doubly stabilized clove essential oil chitosome nanoparticles (CNP) was developed to maintain the freshness of marinated steaks. Results from the XRD and SEM experiments indicated excellent compatibility between the CNP and GEL/PVA matrix. Additionally, CNP was found to introduce more free hydroxyl groups, enhance the water retention and surface wettability of the CNP-GEL/PVA (C-G/P) film, and significantly reduce the swelling index from 963.78% to 495.11% (p < 0.05). Notably, the highest tensile strength and elongation at break (53.745 MPa and 46.536%, respectively) were achieved with the addition of 30% (v/v, based on the volume of gelatin) CNP; UVC was fully absorbed with 40% CNP; and films containing 60% CNP showed optimal inhibition of both Staphylococcus aureus and Escherichia coil, extending the shelf life of marinated steak from 3 to 7 days.

Development and characterization of wax-bovine bone protein-grapeseed oil composite oleogels: Experimental and molecular simulation studies.

Three new types of composite oleogel formulations were designed. Specifically, oleogels were prepared using 90% grapeseed oil as the oil phase and carnauba wax (CW)/beeswax/rice bran wax-bovine bone protein (BBP) as gelators. All samples were solid and had an oil-binding capacity of >90%. BBP addition considerably improved the waxy texture of the oleogel and had an important effect on the crystalline network. X-ray diffractometry indicated that BBP increased the ß'-crystal content. All samples showed sol-gel thermodynamic behavior under temperature scanning. Fourier-transform infrared spectroscopy and molecular docking confirmed the formation of noncovalent interactions dominated by van der Waals forces during the development of the oleogel. The optimal components of the three oleogels exhibited an excellent effect of slowing down the release of free fatty acids. This study could serve as a reference for the development and application of wax-protein as a new binary gelator in the food industry.

Impact of Coreopsis tinctoria Nutt. Essential oil microcapsules on the formation of biogenic amines and quality of smoked horsemeat sausage during ripening.

The present study evaluated the effect of Coreopsis tinctoria Nutt. essential oil (CEO) and its microcapsules (CEOM) on the accumulation of biogenic amines (BAs) and the quality of smoked horsemeat sausage during fermentation. The results showed that CEO could effectively inhibit Enterobacteriaceae growth and the formation of BAs (cadaverine, putrescine, tyrosine, histamine and tryptamine) in smoked horsemeat sausages, and the inhibition of CEO was enhanced after embedding (P < 0.05). Compared with other groups, thiobarbituric acid reactive substances, total volatile basic nitrogen and pH were lower in the microcapsule group. Furthermore, the sensory evaluation indicated that the addition of CEOM was a more effective way to maintain color and delay the deterioration of the sensory quality of sausages. Therefore, it is suggested that the CEOM can be used as a natural preservative in traditional fermented meat products to inhibit BAs accumulation and improve quality.

Effects of Thyme Essential Oil Microcapsules on the Antioxidant and Quality Characteristics of Mutton Patties.

This study aimed to assess the stability of thyme essential oil microcapsules (TEOMs) and their impacts on the antioxidant properties and quality of lamb patties. The results demonstrated that gum Arabic effectively enhanced the stability of phenols within the thyme essential oil (TEO), with an optimal core/wall ratio of 1:8. Substituting TEO with TEOMs in lamb patties led to reductions in the thiobarbituric acid content, carbonyl content, sulfhydryl loss, and protein cross-linking. Additionally, the TEOMs positively influenced the mutton patties' color, texture, microbiological stability, and sensory attributes. These findings substantiate the idea that TEOMs exhibit significant potential as a natural preservative to enhance the quality of mutton patties.

Evaluation of changes in egg yolk lipids during storage based on lipidomics through UPLC-MS/MS.

A comprehensive UPLC-MS/MS-based lipidomics analysis of egg yolk at different storage periods was performed. Through the analysis, 836 lipid species from 27 subclasses were detected, including 159 significantly different lipid species. Glycerolipids (GL) and glycerophospholipids (GP) were the most abundant lipids, followed by fatty acyls (FA), sphingolipids (SP), sterol lipids (ST), and prenol lipids (PR). PCA and OPLS-DA showed that egg yolk lipids changed significantly with prolonged storage. Moreover, glycerophospholipid metabolism and glycerolipid metabolism were key metabolic pathways, as phosphatidic acid (PA), lysophosphatidic acid (LPA), and diglyceride (DG) were key lipid metabolites in the related metabolic pathways of egg yolk during storage. Furthermore, egg yolk quality changed the most when stored up to 21 days. Our study establishes a foundation for the quality control and the lipid oxidation mechanism of eggs during storage.

Bacterial community succession and volatile compound changes in Xinjiang smoked horsemeat sausage during fermentation.

This study examined the bacterial community dynamics and their relationship with volatile compounds in Xinjiang smoked horsemeat sausage during fermentation. We employed single-molecule real-time sequencing (SMRT) to identify the bacterial composition, while headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was utilized to detect volatile compounds in the sausage. The findings indicated that Staphylococcus xylosus, Lactococcus garvieae, Latilactobacillus sakei, Lactococcus lactis, and Weissella hellenica were the predominant species during the fermentation. Moreover, we identified 56 volatile substances in the smoked horsemeat sausages, including alcohols, esters, ketones, acids, aldehydes, terpenes, and phenols. Notably, the correlation analysis demonstrated positive associations between the major bacteria and the primary volatile compounds, with notable connections observed for Staphylococcus xylosus, Lactococcus garvieae and Weissella hellenica. These research findings provide a foundation for future endeavors aimed at enhancing the flavor quality of smoked horsemeat sausage.

UPLC-MS-MS-based lipidomics for the evaluation of changes in lipids during dry-cured mutton ham processing.

Six key stages in the processing of dry-cured muton ham were selected, and changes in the main lipid metabolites as well as the major pathways involved were identified using a lipidic metabolomics approach based on UPLC-MS-MS. In total, 581 lipid metabolites from 22 subclasses were identified, including 521 significantly differential lipids (p < 0.05, VIP > 1). Glycerolipids (GL) were the most abundant lipids, followed by glycerophospholipids (GP), fatty acyls (FA), and sphingolipids (SL). PCA and OPLS-DA of metabolites showed that the quality of mutton ham changed the most during the P3 fermenting stage, including TG(18:1/18:2/18:3), PE(20:5/18:1), and TG(16:1/18:1/18:4) that were significantly downregulated, and CE(20:3), FFA(24:6), LPC(20:3/0:0), and FFA(18:4) that were significantly upregulated. Moreover, glycerophospholipid metabolism and sphingolipid metabolism were the key metabolic pathways involved in the processing of dry-cured mutton ham. Our results provide a basis for quality control and product improvement of dry-cured mutton ham.

Effects of apple polyphenols and hydroxypropyl-ß-cyclodextrin inclusion complexes on the oxidation of myofibrillar proteins and microstructures in lamb during frozen storage.

This study aimed to evaluate the effect of inclusion complexes (ICs) on the oxidative stability of myofibrillar proteins (MPs) and microstructures in lamb during frozen storage. The inclusion process between apple polyphenols (APs) and hydroxypropyl-ß-cyclodextrin (HP-ß-CD) was verified using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and the antioxidant activity of APs. Results showed that the sensitivity of MPs to oxidation improved after 40 weeks. The ICs (0.2-1.6 mg/mL) significantly reduced the carbonyl content, particle size aggregation, protein degradation, fluorescence quenching effect, and decreased the α-helix contents loss of MPs. Additionally, the changes in protein oxidation showed a correlation with the microstructure of muscles, and the addition of 1.6 mg/mL IC remarkably improved the structure of muscle tissues while that of 3.2 mg/mL IC was detrimental to the structural properties. Overall, the exertion of antioxidant activity significantly influenced the cryoprotective effect of ICs on frozen lamb meat.

Sensory Properties and Main Differential Metabolites Influencing the Taste Quality of Dry-Cured Beef during Processing.

This study adopted widely targeted high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) metabolomics and multivariate data analysis methods to evaluate the correlation between changes in metabolites and their taste formation in dry-cured beef during processing. The physicochemical profile changed significantly in the maturity period (RG), especially due to the continuous hydrolysis and oxidation of proteins. The sensory characteristic of dry-cured beef was highest in saltiness, umami, overall taste, and after-taste in RG. Overall, 400 metabolites were mainly identified, including amino acids, peptides, organic acids, and their derivatives, nucleotides, and their metabolites, as well as carbohydrates. Cysteine and succinic acid were significantly up-regulated during the process of dry-curing beef compared to the control group (CG). Moreover, glutamine and glutathione were significantly down-regulated in the fermentation period (FG) and in RG. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that glyoxylate and dicarboxylate metabolism, glutathione metabolism, alanine, aspartate, and glutamate metabolism, arginine biosynthesis, taurine, and hypotaurine metabolism were the main metabolic pathways influencing the taste of dry-cured beef during processing. Results of correlation analysis revealed that umami is positively correlated with salty, L-cysteine, L-arginine, inosine, creatinine, and succinic acid. Our study results provide a better understanding of the changes in taste substances and will contribute to quality evaluation of dry-cured beef.

Application of iTRAQ Technology to Identify Differentially Expressed Proteins of Sauce Lamb Tripe with Different Secondary Pasteurization Treatments.

Vacuum-packed sauce lamb tripe was subjected to secondary pasteurization by high-pressure processing (HPP) and heat treatment (HT), and iTRAQ technology was applied to investigate the differentially expressed proteins (DEPs). The analysis revealed 484 and 398 DEPs in the HPP and HT samples, respectively, compared with no treatment. These DEPs were sorted by texture results, and it was revealed that these DEPs acted in different biological processes with many structural proteins and protein subunits related to lamb tripe texture. The results verified by Western blot were consistent with the protein expression changes observed by proteomics. The bioinformatics analysis showed that the hardness and gumminess of the sauce lamb tripe after HT might be related to changes in the expression of CNN1 and FN1. The changes in the expression of TMP, FN1, YWHAG, TTN, collagen isoforms, and ARPC3 might be related to the improved springiness and chewiness of lamb tripe after HPP.

The Effect of the Ratio of Gamma Aminobutyric Acid-Producing Saccharomyces cerevisiae DL6-20 and Kluyveromyces marxianus B13-5 Addition on Cheese Quality.

Kazakh cheese is a traditional dairy product in Xinjiang, China. The function and potential probiotic characteristics of Saccharomyces cerevisiae DL6-20 and Kluyveromyces marxianus B13-5 in Kazakh cheese and its contribution to cheese fermentation was studied. In this study, the effect of the addition ratio of gamma aminobutyric acid (GABA)-producing S. cerevisiae DL6-20 and K. marxianus B13-5 on cheese quality was investigated. Cheeses were prepared by fermentations with a total of six treatments: comercial culture alone as control (CS), a combination with one yeast, either; K. marxianus B13-5 (CSM); S. cerevisiae DL6-20 (CSS); and three different proportions of this two yeasts (CSM:CSS 1:1, 1:2, 2:1). We measured the GABA content of cheese, as well as basic physical and chemical indicators, microbial content, free amino acid (FAA) content, texture, and flavor compound content. The total FAA content of mixed bacteria fermentation was higher than that of the single bacteria alone. The GABA content CSM:CSS 1:2 GABA content was 0.114 g/100 g, CSM:CSS 2:1 GABA content was 0.12 g/100 g, CSM:CSS1:1 content of GABA produced in the late ripening period of cheese was the highest, reaching 0.189 g/100 g and the number of LAB and yeasts in CSM:CSS 1:1 was higher than that of other cheeses. The mixed-strain fermentation generally produced cheeses with a higher protein content than that of the single-strain fermentation in the late stage of the maturation process, especially the protein content of CSM:CSS 1:1 during the ripening period, when the protein content was highest at day 50. CSM:CSS 1:1 had a low moisture content, making it easy to store. With the exception of water and protein content, there is no significant difference in other physical and chemical indicators. CSM:CSS 1:1 contributed to the formation of cheese texture. In addition, multivariate statistical analysis indicated that mixed-strain fermentation was beneficial to the production of cheese aroma, with the aroma production performance of CSM:CSS 1:2 and CSM:CSS 2:1 found to be better than that of CSM: CSS 1:1.

Heterologous Expression and Application of Multicopper Oxidases from Enterococcus spp. for Degradation of Biogenic Amines.

BACKGROUND: Biogenic amines are harmful to human health at a certain extent. As a kind of biogenic amine oxidase, multicopper oxidase can be used to degrade them. Currently, the literature about enzyme from Enterococcus spp. are limited, and recombinant multicopper oxidase might be an effective way to degrade biogenic amines. OBJECTIVE: (i) Select and identify strains that can degrade biogenic amines, (ii) overexpress enzyme from Enterococcus spp., (iii) measure gene expression and probe amine-degradation differences among strains (native, E. coli DH5α, and L. delbruckii), and (iv) examine the biochemical properties of recombinant multicopper oxidase, (v) apply the recombinant enzyme into smoked horsemeat sausage. METHODS: Reverse transcription PCR and high-performance liquid chromatography were performed to examine gene expression and amine degradation rate. RESULTS: The results demonstrated that target enzymes were successfully overexpressed, accompanied by increased amine-degrading activity (P <0.05). Gene from E. faecalis M5B was expressed in L. delbrueckii resulted in degradation rates for phenylethylamine, putrescine, histamine and tyramine of 54%, 52%, 70% and 40%, respectively, significantly higher than achieved by other recombinant strains. CONCLUSION: In this work, gene expression levels were higher in recombinant M5B than recombinant M2B, regardless of host. E. coli is more stable to express multicopper oxidase. Besides, the amine-degrading ability was markedly increased in the two recombinant strains. After prolonged incubation, the recombinant enzyme could degrade three amines, and it displayed high alkali resistance and thermostability.

Antioxidant activities of peptides derived from mutton ham, Xuanwei ham and Jinhua ham.

The aim of the study was to evaluate antioxidant activity of crude peptides with molecular weight less than 3 KDa extracted from Xuanwei ham, Jinhua ham and mutton ham. UPLC-Q-TOF-MS/MS was used for composition analysis of peptides and homologous protein matching. Further, crude peptide (<3 KDa) was purified using G-15 gel filtration chromatography, and the main antioxidant peptide identified. Analysis showed that mutton ham peptide (MHP) has the highest Fe2+ chelating ability, whereas Jinhua ham peptide (JHP) had the highest ABTS and DPPH free radical scavenging ability (P < 0.05). A total of 346, 203 and 296 peptides were identified in JHP, Xuanwei ham peptides (XHP) and MHP, respectively. Most of the peptides were derived from myosin, accounting for 21.97% in JHP, 18.72% in XHP, and 21.96% in MHP. Myosin, actin, myoglobin, troponin, tropomyosin and pyruvate kinase proteins were the main source of peptide differences in the three types of dry cured ham.

Impact of Thyme Microcapsules on Histamine Production by Proteus bacillus in Xinjiang Smoked Horsemeat Sausage.

Here, we explored the influences of thyme microcapsules on the growth, gene expression, and histamine accumulation by Proteus bacillus isolated from smoked horsemeat sausage. RT-qPCR was employed to evaluate the gene expression level of histidine decarboxylase (HDC) cascade-associated genes. We used HPLC to monitor histamine concentration both in pure culture as well as in the processing of smoked horsemeat sausage. Results showed that histamine accumulation was suppressed by thyme microcapsule inhibitory effect on the histamine-producing bacteria and the reduction in the transcription of hdcA and hdcP genes. Besides, compared with thyme essential oil (EO), thyme microcapsules exhibited higher antibacterial activity and had a higher score for overall acceptance. Therefore, the addition of thyme microcapsules in Xinjiang smoked horsemeat sausage inhibits histamine accumulation.