Exploring the link between microbial community structure and flavour compounds of traditional fermented yak milk in Gannan region

The rapid fermentation of Euphausia superba sauce and revealing of the relationship between key flavor compounds and core microorganisms

Euphausia superba is a highly stocked biological resource, while its utilization in producing shrimp sauce is rarely reported. Traditional fermentation methods of seafood sauces usually need long fermentation period. This study proposed a rapid fermentation method for Euphausia superba sauce (AKS) and verified the feasibility, then revealed the key flavor substances and functional core microorganisms and established their relationship. Results showed that the rapidly fermented AKS owned the amino acid nitrogen content of 1.10 g/100 mL, the total nitrogen of 15.21 %, the volatile base nitrogen of 63.94 mg N/100 g, and the liquefaction rate of 87 %. Asp, Glu, Thr, GMP, malic acid, acetic acid, lactic acid, methanethiol, pentanal, propanal, etc. were screened out as the key flavor compounds. Peptoniphilus, Halomonas, Paenochrobactrum, Proteus, etc. were picked out as the core microorganisms. Further analysis revealed that Paenochrobactrum, Halomonas, Erysipelothrix, Aquamicrobium and Leucobacter were involved in the generation of free amino acids, organic acids, aldehydes and ketones. This study provided a reference for the rapid fermentation of AKS during industrial production, laying the foundation for effective control fermentation process and ensuring quality stability of prepared AKS.

Differentiation and characterization of volatile compounds in five common milk powders using HS-GC-IMS, HS-SPME-GC-MS, and multivariate statistical approaches

Aroma is a key factor in milk powder quality evaluation and consumer choice. However, research has mostly focused on processing effects, with little on flavor differences among milk powders. This study analysed and identified the flavor characteristics of five common types of milk powders in China, including yak milk powder, donkey milk powder, camel milk powder, goat milk powder, and cow milk powder, using Headspace-Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS), Headspace Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS), and multivariate statistical analysis. Results identified 55 and 86 volatile compounds via HS-GC-IMS and HS-SPME-GC-MS, respectively, revealing significant differences between milk powders. PCA, OPLS-DA, PLS-DA, and heatmaps further distinguished the sources. Based on VIP values, 27 and 24 key compounds were identified. These results underscored the potential of utilizing these combined techniques for quick flavor analysis and detecting adulteration in milk powder.

Analysis of Flavor Differences in Yak Milk Powder at Different Milk Production Stages by Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The aroma of yak milk powder is a crucial sensory indicator for evaluating its quality and flavor. Yak milk powders collected from different lactation periods exhibit distinct flavors, but no studies have thoroughly investigated the aroma characteristics and variation patterns of yak milk powders across these periods. This study identified and analyzed the volatile compounds in freeze-dried colostrum powder (YCSP), freeze-dried mature milk powder (YMMP), and freeze-dried ending milk powder (YEMP) using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and multivariate statistical analysis. A total of 48 volatile compounds were identified, with significant differences in the types and contents of these compounds across the three samples. Compared to YCSP and YEMP, YMMP contained higher levels of acids and esters, while the levels of alkanes and alcohols were lower. Principal component analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA), and hierarchical clustering heatmap analysis revealed a high degree of differentiation and notable variation in volatile compounds between the samples from different lactation periods. Key compounds such as aldehydes, alcohols, and esters were found to distinguish the lactation stages, with certain compounds more prevalent in colostrum and others in mature and ending milk. These findings suggest that the methodologies employed-HS-SPME-GC-MS combined with multivariate analysis-can effectively distinguish flavor differences among yak milk powders from different lactation periods. This approach allows for the rapid and comprehensive analysis of volatile components in milk powders, aiding in the identification of collection periods and providing valuable insights for improving the flavor quality of dairy products. Furthermore, the results can benefit the dairy industry by enhancing product development, quality control, and flavor profiling of milk-based products across different stages of lactation.

Volatile Flavor Analysis in Yak Meat: Effects of Different Breeds, Feeding Methods, and Parts Using GC-IMS and Multivariate Analyses

This study investigates the effects of breeds, feeding methods, and parts on the volatile flavor of yak meat. Gas chromatography-ion mobility spectrometry (GC-IMS) and multivariate analysis were used to analyze the volatile organic components (VOCs) in yak meat from various sources. A total of 71 volatile compounds were identified, 53 of which were annotated based on the GC-IMS database. These include 20 alcohols, 16 ketones, 10 aldehydes, four alkenes, one ester, one acid, and one furan. Using VOC fingerprinting and multivariate analysis, yak meats from different sources were distinctly categorized. Breed had the most significant impact on yak meat VOCs, followed by feeding method and then part. Six volatiles with a variable importance in projection value greater than one were identified as potential markers for distinguishing yak meat. This study offers insights into the flavor profile of yak meat from different sources and demonstrates the efficacy of GC-IMS and multivariate analysis in characterizing and discriminating meats.

Sustainability implications and relevance of using omics sciences to investigate cheeses with protected designation of origin

Cheese, a fundamental component of the human diet and a cornerstone of the global food economy, has a significance beyond its role as a commodity, playing a crucial part in the cultural identity of various communities. The intricate natural aging process known as maturation involves a series of reactions that induce changes in the cheese's physical, biochemical, microbiological, and particularly sensory characteristics, making it a complex aspect of cheese production. Recently, the adoption of omics sciences (e.g., metagenomics, metabolomics, proteomics) has emerged as a new trend in studies related to protected designation of origin (PDO) cheese. This mini-summary aims to outline the relationship between omics studies in these food matrices and all the sustainability facets of the production chain in general, and to discuss and recognize that the importance of these studies goes beyond comprehending the cheese biome and extends to fostering and ensuring the sustainability of the production chain. In this context, numerous studies in recent years have linked the identification of intrinsic characteristics of PDO cheeses through omics sciences to crucial sustainability themes such as territoriality, biodiversity, and the preservation of product authenticity. The trajectory suggests that, increasingly, multidisciplinary studies spanning various omics sciences will not only contribute to the characterization of these products but will also address sustainability aspects directly related to the production chain (e.g., authenticity, microbial biodiversity, functionality). This expansion underscores the multidisciplinary nature of these studies, broadening their social impact beyond the academic realm. Consequently, these pivotal studies play a crucial role in advancing discussions on PDO products and sustainability. © 2024 Society of Chemical Industry.

Polymorphisms within the PRKG1 Gene of Gannan Yaks and Their Association with Milk Quality Characteristics

Yak milk, known as the "liquid gold", is a nutritious food with extensive consumption. Compared with cow milk, yak milk contains higher levels of nutrients such as dry matter, milk fat, and milk protein, which demonstrates great potential for exploitation and utilization. Protein kinase cGMP-dependent 1 (PRKG1) is an important functional molecule in the cGMP signaling pathway, and its significant influence on milk fatty acids has been discovered. The aim of this study is to explore the correlation between single nucleotide polymorphisms (SNPs) in the PRKG1 gene and the quality traits of Gannan yak milk in order to identify candidate molecular markers for Gannan yak breeding. In this study, genotyping was performed on 172 healthy, 4-5-year-old lactating Gannan yaks with similar body types, naturally grazed, and two to three parity. Three SNPs (g.404195C>T, g.404213C>T, and g.760138T>C) were detected in the PRKG1 gene of Gannan yaks, which were uniformly distributed in the yak population. Linkage disequilibrium analysis was conducted, revealing complete linkage disequilibrium between g.404195C>T and g.404213C>T. After conducting a correlation analysis between SNPs in the PRKG1 gene and milk quality in Gannan yaks, we found that PRKG1 SNPs significantly increased the content of casein, protein, and SNFs in yak milk. Among them, the TT homozygous genotype at the PRKG1 g.404195C>T loci exhibited higher casein and protein contents compared to the CC and CT genotypes (p < 0.05). The SNP g.760138T>C locus was associated with casein, protein, SNFs, and TS traits (p < 0.05). The CC genotype had higher casein and protein contents than the TT and TA genotypes (p < 0.05). However, there were no significant differences in milk fat, lactose, and acidity among the three genotypes (p > 0.05). In summary, PRKG1 gene polymorphism can serve as a candidate molecular marker for improving milk quality in Gannan yaks.

GC-IMS and multivariate analyses of volatile organic components in different Chinese breeds of chickens

This study examined the difference in volatile flavor characteristics among four different local breeds of chicken by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with multivariate analysis. In total, 65 volatile organic compounds (VOCs) were identified (17 aldehydes, 12 alcohols, 7 ketones, 5 esters, 2 acids, and 22 unidentified, i.e., 26.15% aldehydes, 18.46% alcohols, 10.77% ketones, 7.69% esters, 3.08% acids, and 33.84% unidentified), of which 43 were annotated. The chicken meats from the four breeds exhibited good separation in topographic plots, VOC fingerprinting, and multivariate analysis. Meanwhile, 20 different volatile components, with variable importance in projection value > 1, were selected as potential markers to distinguish different breeds of chicken by partial least squares discriminant analysis (PLS-DA). These findings provide insights into the flavor traits of chicken meat. Also, HS-GC-IMS combined with multivariate analysis can be a convenient and powerful method for characterizing different meats.

Association between Single Nucleotide Polymorphisms of PRKD1 and KCNQ3 Gene and Milk Quality Traits in Gannan Yak (Bos grunniens)

Protein kinase D1 (PRKD1) functions primarily in normal mammary cells, and the potassium voltage-gated channel subfamily Q member 3 (KCNQ3) gene plays an important role in controlling membrane potential and neuronal excitability, it has been found that this particular gene is linked to the percentage of milk fat in dairy cows. The purpose of this study was to investigate the relationship between nucleotide polymorphisms (SNPs) of PRKD1 and KCNQ3 genes and the milk quality of Gannan yak and to find molecular marker sites that may be used for milk quality breeding of Gannan yak. Three new SNPs were detected in the PRKD1 (g.283,619T>C, g.283,659C>A) and KCNQ3 gene (g.133,741T>C) of 172 Gannan lactating female yaks by Illumina yak cGPS 7K liquid-phase microarray technology. Milk composition was analyzed using a MilkoScanTM milk composition analyzer. We found that the mutations of these three loci significantly improved the lactose, milk fat, casein, protein, non-fat milk solid (SNF) content and acidity of Gannan yaks. The lactose content of the TC heterozygous genotype population at g.283,619T>C locus was significantly higher than that of the TT wild-type population (p < 0.05); the milk fat content of the CA heterozygous genotype population at g.283,659C>A locus was significantly higher than that of the CC wild-type and AA mutant populations (p < 0.05); the casein, protein and acidity of the CC mutant and TC heterozygous groups at the g.133,741T>C locus were significantly higher than those of the wild type (p < 0.05), and the SNF of the TC heterozygous group was significantly higher than that of the mutant group (p < 0.05). The results showed that PRKD1 and KCNQ3 genes could be used as candidate genes affecting the milk traits of Gannan yak.