Mulberry perishes easily due to its high water content and thin skin. It is important to extend the shelf life of mulberry by proper processing methods. In the present study, the influence of three drying techniques, including hot air drying (HAD), vacuum drying (VD), and vacuum freeze-drying (VFD) on the quality maintenance of mulberry was comprehensively evaluated. Bioactive compounds, antioxidant activity, and the sensory and volatile flavor compounds of mulberry have been researched. The results showed that VFD treatment maintained the highest anthocyanins (6.99 mg/g), total flavones (3.18 mg/g), and soluble sugars (2.94 mg/g), and exhibited the best DPPH· (81.2%) and ABTS⁺· (79.9%) scavenging ability. Mulberry also presented the lowest hardness and the greatest brittleness after VFD. Additionally, VFD maintained the optimal color and presented the best sensory attributes. Furthermore, 30, 20, and 32 kinds of volatile flavor compounds were detected in HAD, VD, and VFD, respectively, among which aldehydes, esters, and ketones were the most abundant compounds. This study indicated the potential application value of VFD for the drying of fruit and vegetable foodstuffs.

The quality of Baijiu was largely affected by raw materials, which determine the flavor and taste. In the present study, organic acids, polyphenols, volatile flavor components and microbial community in Hovenia acerba-sorghum co-fermented Baijiu (JP1) and pure sorghum-fermented Baijiu (JP2) were comprehensively analyzed. Organic acids, polyphenols and volatile flavor components in JP1 were more abundant than JP2. The abundance and diversity of bacteria and fungi in JP1 was higher than that in JP2 in the early stage of fermentation, but presented opposite trend in the middle and late stages. Leuconostoc, Lentilactobacillus and Issatchenkia were dominant genera in JP1. Whereas, Cronobacter, Pediococcus and Saccharomyces occupied the main position in JP2. Lentilactobacillus and Issatchenkia were positively related to most of organic acids and polyphenols. Pseudomonas, Rhodococcus, Cronobacter, Pediococcus, Brucella, Lentilactobacillus, Lactobacillus, Saccharomycopsis, Wickerhamomyces, Aspergillus, Thermomyces and unclassified_f—Dipodascaccae were associated with the main volatile flavor components. The main metabolic pathways in two JPs exhibited the variation trend of first decreasing and then increasing, and the metabolism activity in JP1 were higher than that in JP2. The results demonstrated the introduction of Hovenia acerba improved the functional ingredients and volatile flavor components, which is helpful for the quality promotion of Baijiu. This study identified the key microorganisms and discussed their effect on organic acids, polyphenols and volatile flavor components during the fermentation of Baijiu with different raw materials, providing a scientific basis for the development and production of high-quality Baijiu.

Mulberry Jiaosu, derived from natural fermentation using fresh mulberry fruit as a raw material, refers to an edible product containing specific bioactive substances. However, the dynamic changes in the bioactive substances of organic acids, amino acids and polyphenols as well as the species and function of microorganisms in mulberry Jiaosu are still not clear. Herein, the whole fermentation process of mulberry Jiaosu was comprehensively researched by analyzing the microbial community structure and bioactive substances. The results showed that the change in physicochemical parameters mainly happened within 30 days of fermentation. The total organic acids and total polyphenols presented upward trends. Total amino acids were partly consumed during the fermentation. A total of 173 fungal genera and 295 bacterial genera were detected in mulberry Jiaosu, mainly including Torulaspora, Zygosaccharomyces and Lactobacillus, whose abundance can be influenced by changes in the fermentation environment. During the fermentation of mulberry Jiaosu, 8 organic acids, 17 amino acids and 9 polyphenols were observed, which could be regulated by the metabolism of microorganisms. Zygosaccharomyces exhibited positive correlations with the majority of the organic acids, amino acids and polyphenols, presenting a great influence on the formation of bioactive substances. Compared with fungi, bacteria contributed more to the synthesis of organic acids, free amino acids and polyphenols. This study revealed the bioactive substances and microbial diversity during the fermentation of mulberry Jiaosu, which are findings that will contribute to the precise regulation of the fermentation process and improvement of the product quality.