Abstract In this study, the effect of storage temperature (2 or 4°C) on the composition of milk and microbiological load was investigated over 96 h. Milk samples were collected from farm bulk milk tanks after one complete milking and stored at 2 or 4°C over 96 h. Total bacterial count (TBC), psychrotrophic bacterial count (PBC) and proteolytic bacterial count (PROT) were affected by storage time and temperature and varied significantly between farms (P < 0.05). The levels of TBC, PBC and PROT bacterial count increased from 4.37 to 6.15 log cfu/mL, 4.34 to 6.44 log cfu/mL and 3.72 to 4.81 log cfu/mL, respectively, when the milk was stored for 96 h at 2°C. The milk samples stored at 4°C had higher increases in these bacterial counts after 72 h in comparison to milk samples stored at 2°C. The casein fraction content was lower in milk samples stored at 4°C, which could be due to high levels of PROT bacteria or enzyme activity in these samples. Milk stored for 96 h at 2°C has less impact on composition or processability parameters compared to milk stored at 4°C.

中文翻译：

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评估储存条件对牛奶微生物质量和成分的影响

摘要 在这项研究中，研究了 96 小时内储存温度（2 或 4°C）对牛奶成分和微生物负荷的影响。牛奶样品是在一次完全挤奶后从农场散装牛奶罐中收集的，并在 2 或 4°C 下储存 96 小时。总细菌数 (TBC)、嗜冷菌数 (PBC) 和蛋白水解菌数 (PROT) 受储存时间和温度的影响，不同农场之间差异显着（P < 0.05）。当牛奶在 2°C 下储存 96 小时时，TBC、PBC 和 PROT 细菌计数水平分别从 4.37 增加到 6.15 log cfu/mL、4.34 到 6.44 log cfu/mL 和 3.72 到 4.81 log cfu/mL . 与储存在 2°C 下的牛奶样品相比，储存在 4°C 下的牛奶样品在 72 小时后这些细菌计数的增加更多。在 4°C 下储存的牛奶样品中酪蛋白组分含量较低，这可能是由于这些样品中的 PROT 细菌或酶活性水平较高。与在 4°C 下储存的牛奶相比，在 2°C 下储存 96 小时的牛奶对成分或可加工性参数的影响较小。