Comparison of fungal communities and flavour substances in surface and inner layers of fermented grains during stacking fermentation of sauce-flavour baijiu.

The stacking fermentation process plays a vital role in the production of sauce-flavour baijiu. The aim of this paper is to elucidate the effects of environmental variables on the fungal communities of different layers of fermented grains (zaopei) during the sixth round of stacking and the changes in volatile flavour substances during this process. The composition of the fungal communities in different layers during the stacking fermentation process was analysed. Principal coordinate analysis (pCoA) showed that the dominant fungal communities in different layers differed significantly with the stacking fermentation process. The dominant fungal genera were Thermoascus, Thermomyces and Issatchenkia. The total content of flavouring substances in the surface layer of zaopei were higher, but the types of flavouring substances were less than in the inner layer. The relationship between temperature, moisture content, acidity, starch content and reducing sugar content and microbial community was analysed by Redundancy analysis. The results showed that the correlation between microbial communities and physicochemical indexes in different layers of zaopei varied. The core fungal genera in the surface layer were mainly influenced by acidity, and the microorganisms in the inner layer were more strongly correlated with temperature. Spearman correlation coefficient revealed the correlation between fungal community and volatile flavour substances, and the results showed that microorganisms in different layers of zaopei have different correlations with flavour substances. This study contributes to the understanding of the evolution of different layers fungal communities during the stacking of sauce-flavour baijiu and their relationship with volatile aroma substances.

Study of meat quality and flavour in different cuts of Duroc-Bamei binary hybrid pigs.

BACKGROUND: Meat quality and flavour are important criteria for judging fresh pork and processed products. However, there have been few studies on meat quality and volatile flavour substances of different parts of binary hybrid pigs. OBJECTIVE: To study the differences in meat quality and volatile flavour substances between different cuts of pork, which could provide the basis for consumer decision-making when purchasing pork. METHODS: Twenty Du-Ba binary hybrid pigs (first filial [F1] generation) bred from Duroc and Bamei pigs were used. This study systematically compared and analysed the basic nutritional components, amino acid composition, fatty acid composition and flavour profiles of longissimus dorsi, rib muscle and tendon meat of four Du-Ba binary hybrid pigs; all assays were repeated in triplicate. RESULTS: Crude protein, calcium and phosphorus content in tendon meat were higher than that in the longissimus dorsi. The intramuscular fat content of the rib muscle was higher than that in the longissimus dorsi and tendon meat (p < 0.05). The amino acid content was highest in the tendon meat. The levels of essential amino acids and flavour-associated amino acids per kilogram of longissimus dorsi were higher than those in the rib muscle and tendon meat. Moreover, the content of aspartic acid, serine and cystine were higher in the longissimus dorsi than in the other two parts. The type of saturated fatty acids and the type and content of unsaturated fatty acids in tendon meat were higher than in the longissimus dorsi and rib muscle. The total content of volatile flavour compounds was higher in the longissimus dorsi than in the rib muscle and tendon meat. CONCLUSION: The rib muscle contains high deposits of fat, and tendon meat has a relatively high nutritional value, while the longissimus dorsi has a stronger flavour.