为了解不同低温条件下生鲜乳中嗜冷菌的菌群结构变化,将采自河北地区奶牛养殖场中的新鲜生牛乳置于不同低温条件下存储不同时间,高通量测序分析其在存储过程中的菌群结构变化和嗜冷菌的多样性.结果表明,10个处理30个样本共注释到20门、41纲、76目、162科、319属和364种.各处理优势菌门与优势菌属差异显著,且占比各不相同;α-多样性显示生鲜乳不同处理的细菌群落多样性差异显著(P<0.05);这一结果表明不同低温条件下生鲜乳中的菌群结构差异显著,同一温度条件下的不同贮藏时间的样品中的菌群结构显著不同,为进一步延长生鲜乳及其制品的货架期提供理论依据.

Raw milk is a nature media of microbiota that access milk from various sources, which constitutes a challenge in dairy production. This study characterizes the relationship between the raw milk quality and the bacteria diversity at different sampling sites in dairy farms, aiming to provide a strong scientific basis for good hygienic practices and optimized procedure in milk production. High-throughput sequencing of 16S rRNA V3-V4 region was used to analyze the components, abundance and diversity of 48 bacterial population sampled from 8 different sites in dairy farm: pre-sterilized cow's teats (C1), post-sterilized cow's teats (C2), milking cluster (E), milk in storage tank (M1), transport vehicle (M2), storage equipment (E2), cow's dung samples (F) and drinking water (W). Firmicutes account for predominantly 32.36% (C1), 44.62% (C2), 44.71% (E), 41.10% (M1), 45.08% (M2), 53.38% (F) of all annotated phyla. Proteobacteria accounts for 81.79% in W group and Actinobacteria 56.43% in E2 group. At the genus level, Acinetobacter was the most abundant genus that causes bovine mastitis, Acinetobacter and Arthrobacter were dominant in C1, C2, and E groups, Kocuria in E2 group and Arcobacter in W group. E, C1, and C2 group have very similar bacterial composition, and M1 and M2 demonstrated similar composition, indicating that the milking cluster was polluted by the environment or contact with cow udders. Bacterial population composition in different sampling sites identified by NGS reveals a correlation between the bacteria communities of raw milk production chain and the quality of raw milk.

Ponkan (Citrus reticulate Blanco) is one of the most popular citrus fruits for daily consumption and processing in China. In this study, limonene was removed from ponkan essential oil (PEO) by using an effective methodology to estimate the optimum levels of three independent variables of molecular distillation (MD) in order to minimize the limonene content and (b) maximize the removal rate. A three-factor Box-Behnken design (BBD) was employed to evaluate the effect of distilling temperature (45.00～55.00 ℃ ), wiper rolling speed (150.00～250.00 r/min) and distilling pressure (25.00～35.00 Pa). The optimum parameters within the experimental range of the variables were extrapolated to be: distilling temperature 47.00℃ , wiper rolling speed 203.00 r/min and distilling pressure 30.00 Pa. Optimal values extrapolated by response surface methodology (RSM) for the limonene content and removal rate of the desirable PEO were 47.82％ and 84.67％, respectively.