Revealing the intrinsic relationship between microbial communities and physicochemical properties during ripening of Xuanwei ham.

To clarify the relationship between microorganisms and physicochemical indicators of Xuanwei ham. Six ham samples for the first, second and third year were selected, respectively. The changes of physicochemical properties, the free fatty acids and microbial communities of Xuanwei ham were investigated by GC-MS and high-throughput sequencing technology. Results showed that scores of colour, overall acceptability, texture, taste and aroma were the highest in the third year sample. With increasing ripening time, moisture content, water activity (Aw), lightness (L*), springiness, and resilience decreased continuously, and yellowness (b*) was the highest in the second year sample. 31 free fatty acids were detected, and unsaturated fatty acids such as palmitoleic acid, oleic acid, and linoleic acid were the major fatty acids. The content of palmitoleic acid, oleic acid and eicosenoic acid increased significantly during processing. At the phylum level, the dominant bacteria were Proteobacteria and Firmicutes, and fungi were Ascomycota. At the genus level, the dominant bacteria were Staphylococcus and Psychrobacter, and fungi were Aspergillus. Correlation analysis showed that water content and Aw were closely related to microorganisms, and most unsaturated fatty acids were significantly correlated with microorganisms. These findings showed that microorganisms played an important role in the quality of Xuanwei ham, and provided a scientific basis for the quality control of Xuanwei ham.

Effect of Stewing Time on the Small Molecular Metabolites, Free Fatty Acids, and Volatile Flavor Compounds in Chicken Broth.

Chicken broth has a taste of umami, and the stewing time has an important effect on the quality of chicken broth, but there are fewer studies on the control of the stewing time. Based on this, the study was conducted to analyze the effects of different stewing times on the sensory, small molecular metabolites, free fatty acids, and volatile flavor compounds contents in chicken broths by liquid chromatography-quadrupole/time-of-flight mass spectrometry, gas chromatography-mass spectrometry, headspace solid-phase microextraction, and gas chromatography-mass spectrometry. Eighty-nine small molecular metabolites, 15 free fatty acids, and 86 volatile flavor compounds were detected. Palmitic and stearic acids were the more abundant fatty acids, and aldehydes were the main volatile flavor compounds. The study found that chicken broth had the best sensory evaluation, the highest content of taste components, and the richest content of volatile flavor components when the stewing time was 2.5 h. This study investigated the effect of stewing time on the quality of chicken broth to provide scientific and theoretical guidance for developing and utilizing local chicken.

Effect of different salt additions on the taste and flavor-related compounds in chicken soup.

Chicken soup is popular among consumers because of its delicious taste, strong flavor, and abundant nutritional value. Twenty-four Yunnan local hens were stewed by adding different amounts of NaCl [1.5, 2, 2.5, 3%, m/m, calculated based on chicken carcass weight; chicken: water = 1:2 (m/m)] to study the effect of salt addition on taste- and flavor-related compounds in chicken soup. Sensory evaluation results showed that the 2 and 2.5% NaCl treatment groups had higher scores. Water-soluble small molecule compounds were detected by LC-Q/TOF-MS based metabolomics approach, among which amino acids and their derivatives, nucleic acids, and small peptides were the main components. The concentration of Water-soluble small molecule substances in chicken soup samples with different salt additions showed a clear trend of separation and reached the highest in the 2.5% NaCl treatment group. Volatile flavor compounds in the chicken soup were analyzed by HS-SPME-GC-MS, including aldehydes, and alcohols, and the relative concentration of flavor compounds in the 2.5% salt treatment group was the highest. In summary, the addition of salt could improve the overall flavor of chicken broth, and the optimal salt addition of NaCl in chicken soup is 2.5%.

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

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

Flavor Characteristics of Umami Peptides from Wuding Chicken Revealed by Molecular Dynamics Simulation.

Wuding chicken is famous for its delicious meat, and HLEEEIK, LDDALR, and ELY were jointly extracted from different processing stages of Wuding chicken. However, whether these peptides can be used as umami supplements is unclear. The sensory evaluation tests were used to study the taste characteristics. The secondary structure of the peptides and their interaction with T1R1/T1R3 were predicted by the circular dichroism spectrum and molecular dynamics simulation. The umami threshold was 0.03125 to 0.06250 mg/mL, all of which could increase umami, saltiness, sweetness, and mask bitterness. Compared with HLEEEIK, the frequency of umami active fragments and the improvement rate of the umami score of EEE increased by 133.35% and 40.09%, respectively. Peptides were dominated by umami taste according to sensory analysis, among which EE-3 (3.18) has the highest umami intensity followed by LR-4 (2.58), HK-7 (2.13), and EY-3 (1.82). The main secondary structure of umami peptides was ß-folding, and Tyr74, Arg323, Arg272, and Gln35 were the key amino acid residues for binding of umami peptides to the receptor. This study further elucidated that the umami intensity of the peptides could be altered by changing the sequence composition of the peptides, which enhanced our understanding of the complex flavor properties of umami peptides.

Identification of characteristic flavor compounds and small molecule metabolites during the ripening process of Nuodeng ham by GC-IMS, GC-MS combined with metabolomics.

To investigate effects of metabolites and volatile compounds on the quality of Nuodeng ham, gas chromatography-mass spectrometry (GC-MS), ultra-high performance liquid chromatography-Q exactive orbitrap-mass spectrometry (UHPLC-QE-MS), and gas chromatography-ion transfer spectroscopy (GC-IMS) were used to analyze the differences of free fatty acids, small molecule metabolites and volatile compounds of Nuodeng ham at different ripening stages (the first, second and third year sample). 40 free fatty acids were detected. 757 and 300 metabolites were detected in positive and negative ion modes, respectively. 48 differential metabolites (VIP ≥ 1.5, P < 0.05) might important components affecting flavor differences of Nuodeng ham. Metabolic pathways revealed that fermenting-ripening of ham was associated with 31 metabolic pathways, among, 19 pathways were significant (Impact > 0.01, P < 0.05). 58 volatile compounds were identified, combined with PCA and PLS-DA, 15 flavor markers were screened out. These findings provide a scientific basis for further research on the flavor formation mechanism of Nuodeng ham.

Comparison of the Fatty Acid Composition and Small Molecular Metabolites between Yanjin Blackbone Chicken and Piao Chicken Meat.

The fatty acid composition and small molecular metabolites in breast and leg meat of Yanjin blackbone chickens (YBC) and Piao chickens (PC) were detected by gas chromatography-mass spectrometry and liquid chromatography-quadrupole static field orbital trap mass spectrometry. Thirty-two fatty acids were detected, and the total fatty acid content of PC was significantly higher than that of YBC (p<0.05). Oleic acid, linoleic acid, palmitic acid, stearic acid, and arachidonic acid were the main fatty acids in the two chicken varieties, and the composition of fatty acids in the two varieties were mainly unsaturated fatty acids, being more than 61.10% of the total fatty acids. Meanwhile, 12 and 16 compounds were screened out from chicken legs and chicken breasts of YBC and PC, respectively, which had important contributions to the differences between groups.

UHPLC-MS/MS-based lipidomics for the evaluation of the relationship between lipid changes and Zn-protoporphyrin formation during Nuodeng ham processing.

The effects of changes in lipids on the formation of Zn-protoporphyrin (ZnPP) during the processing of Nuodeng ham were analyzed using a lipidomics approach based on UHPLC-MS/MS. The Nuodeng ham samples had a strong fluorescence emission peak at 590 nm, and the fluorescence intensity increased with the processing time. Lipid profiles were mainly affected by processing time. A total of 5 lipid classes were detected, of which glycerophospholipids (GP) and glycerolipids (GL) were the most abundant lipids. Fifty differential lipid compounds were screened, which were mainly GP and GL. Correlation analysis showed that 13 differential lipid compounds were significantly positively correlated with ZnPP content, and they contained more linoleic acid and oleic acid branch chains. Meanwhile, all triglycerides (TG) were negatively correlated with heme content, and they were enriched in stearic acid and palmitic acid branch chains. These findings can deepen the understanding of the relationship between ZnPP and lipids.

Identification of umami peptides from Wuding chicken by Nano-HPLC-MS/MS and insights into the umami taste mechanisms.

Wuding chicken is popular with consumers in China because of its umami taste. This study aimed to identify novel umami peptides from Wuding chicken and explore the taste mechanism of umami peptides. The molecular masses and amino acid compositions of peptides in Wuding chicken were identified by nano-scale liquid chromatography-tandem mass spectrometry (Nano-HPLC-MS/MS). The taste characteristics of the peptides synthesized by the solid-phase method were evaluated by sensory evaluation combined with electronic tongue technology. The secondary structure of the peptides was further analyzed by circular dichroism (CD), and the relationship between the structure and taste of the peptides was elucidated by molecular docking. The results showed that eight potential umami peptides were identified, among which FVT (FT-3), LDF (LF-3), and DLAGRDLTDYLMKIL (DL-15) had distinct umami tastes, and FT-3 had the highest umami intensity, followed by LF-3 and DL-15. The relative contents of ß-sheets in the three umami peptides were 55.20%, 57.30%, and 47.70%, respectively, which were the key components of Wuding chicken umami peptides. In addition to LF-3 embedded in the cavity-binding domain of the TIR1, both FT-3 and DL-15 were embedded in the venus flytrap domain (VFTD) of the T1R3 to bind the umami receptor T1R1/T1R3. The main binding forces between the umami peptides and the umami receptor T1R1/T1R3 relied on hydrogen bonds and hydrophobic interactions, and the key amino acid residues of the combination of umami peptides and the umami receptor T1R1/T1R3 were Glu292, Asn235, and Tyr262.

Combined application of high-throughput sequencing and LC-MS/MS-based metabolomics to evaluate the formation of Zn-protoporphyrin in Nuodeng ham.

In order to deepen the understanding of the formation mechanism of Zn-protoporphyrin (ZnPP), Nuodeng ham was used as the research object, and the effects of bacterial communities and small molecule metabolites on the formation of ZnPP during the processing of Nuodeng ham were analyzed by high-throughput sequencing and LC-MS/MS-based metabolomics. With the prolongation of processing time, the ZnPP content increased significantly, while the heme content decreased significantly. Compound curing agent significantly inhibited the formation of ZnPP and significantly decreased the heme content. The bacterial communities changed dynamically and the five bacterial genera were significantly positively correlated with ZnPP content. Forty-seven differential metabolites were obtained through screening, of which seventeen differential metabolites were significantly positively correlated with ZnPP content. Correlation analysis showed a strongly positive correlation between Staphylococcus, Delftia, Acinetobacter and these seventeen differential metabolites. These findings can provide a theoretical basis for further establishing the color control measures of Nuodeng ham.

Effects of different cooking methods on free fatty acid profile, water-soluble compounds and flavor compounds in Chinese Piao chicken meat.

Piao chicken breast meat was cooked by three different methods (boiling, frying and roasting). Non-volatile and volatile substances in the three cooked chicken were analyzed by GC-MS, UPLC-Q-Exactive-MS and GC-IMS, respectively. Arachidonic acid was the highest in boiled chicken, oleic acid was the highest in roasted chicken, linoleic acid, EPA and DHA were the highest in fried chicken. Compared with the control group, the total content of small molecular metabolites of chicken in each treatment group decreased. The total amount of amino acids in roasted chicken was 2.90 times of that in boiled chicken (P < 0.05), and 2.23 times of that in fried chicken (P < 0.05). A total of 26 volatile flavor compounds were detected. Phenylacetaldehyde etc. were the main volatile flavor compounds in boiled chicken, 3-butanedione etc. were the main volatile flavor compounds in fried chicken, while 3-methylbutyraldehyde etc. were the main volatile flavor compounds in roasted chicken.

1H NMR-based water-soluble lower molecule characterization and fatty acid composition of Chinese native chickens and commercial broiler.

The aim of this study was to compare the water-soluble low molecular weight (WLMW) compounds and fatty acids (FAs) in raw meat and chicken soup between the two Chinese native chickens (Wuding chicken and Yanjin silky fowl chicken) and one typical commercial broiler (Cobb chicken). The WLMW compounds of chicken meat was studied using 1H nuclear magnetic resonance spectroscopy (1H NMR) and the FAs were identified and quantified using gas chromatography-mass spectrometry (GC-MS). Compared with typical commercial broiler, the main flavor substances (WLMW compounds and FAs) content were significantly higher in the breast and leg meat of the two Chinese native chickens (P < 0.05). Instead, the content of main flavor compounds was significantly higher in chicken soup of typical commercial broiler (P < 0.05). These results contribute to a further understanding the distinction of the flavor compounds between the typical commercial broiler and Chinese native chickens, which could be used to help assess the meat quality of different local broilers.

Evaluation of small molecular metabolites and sensory properties of Xuanwei ham salted with partial replacement of NaCl by KCl.

The study was to understand the effect of the partial substitution of NaCl by KCl on small molecular metabolites and sensory quality of Xuanwei ham. Thirty green hams were randomly divided into five treatments, and salted with 100% NaCl (I), 70% NaCl+30% KCl (II), 60% NaCl+40% KCl (III), 50% NaCl+50% KCl (IV) and 40% NaCl+60% KCl (V), respectively. With the increase of KCl substitution, the moisture content of Xuanwei ham increased. Non-targeted ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-Q-Exactive-MS) was used to study the effect of partial substitution of NaCl by KCl, and twenty-eight metabolites were identified as markers of small molecular metabolites in the different treatments. KCl substitution promoted the release of tryptophan, histidine, citrulline, lysine, creatine and oleic acid, which contributed to improve the flavor and taste of ham. Therefore, the treatment II and III could reduce the NaCl content of Xuanwei ham by 30% and 40%, and maintained a better sensory acceptability.

1 H-NMR-based water-soluble low molecular weight compound characterization and fatty acid composition of boiled Wuding chicken during processing.

BACKGROUND: Boiled Wuding chicken was produced using whole chicken by washing, boiling 1 h with salt, deep frying, and boiling 2 h. The effect of the process on the water-soluble low molecular weight (WLOM) compound profiles of products was characterized using proton nuclear magnetic resonance spectroscopy, and the fatty acid composition of products was analyzed using gas chromatography-mass spectrometry. RESULTS: The metabolome was dominated by 49 WLOM compounds, and 22 fatty acid compounds were detected. Principal component (PC)1 and PC2 explained a total of 93.4% and 3% of variance respectively. Compared with the control group, the total WLOM compound and fatty acid contents of the chicken breast were significantly decreased in the other three processing stages (P < 0.05). Comprehensive multivariate data analysis showed significant differences about precursor substance between the different processing including creatine, lactate, creatinine, glucose, taurine, anserine, and acetate (P < 0.05). CONCLUSION: These results contribute to a more accurate understanding of precursor substance changes of flavor in chicken meat during processing. Boiled, treated chicken had significant effects on fatty acid and WLOM compounds. © 2018 Society of Chemical Industry.

1H NMR-based metabolic characterization of Chinese Wuding chicken meat.

The aim of this study was to evaluate the chemical composition of precursor flavor substance of Wuding chicken with the age of 110, 140, 170, 200 and 230 days. The metabolic composition of chicken meat was studied using 1H nuclear magnetic resonance (NMR) spectroscopy. Compared with 110 days, the total metabolite content was significantly higher in other four periods for the chicken breast and leg meat (P < 0.01). Organic acid and small peptides were the two most metabolites for the chicken breast and leg meat. Comprehensive multivariate data analysis showed significant differences about precursor substance between the chicken samples of 230 days and other four ages including lactate, creatine, IMP, glucose, carnosine, anserine, taurine and glutamine (P < 0.05). These results contribute to a further understanding of changes in chicken meat metabolism as chicken ages, which could be used to help assess the quality of chicken meat.