摘要
Shelf life of pasteurized milk is relatively short, mainly due to cold chain conditions. This study investigated the effects of different storage temperatures （8, 10 and 12 ℃） on acidity, microorganism index, physical and chemical indicators and sensory quality of pasteurized milk packaged in glass bottle to determine the main factor affecting the quality of pasteurized milk during shelf life under different tem- peratures. The results showed that within the first five days, the protein, fat, lactose and non-fat milk solids contents in the milk samples did not change under different storage temperatures; the acidity was almost unchanged at 8 and 10 ℃, and in- creased slightly at 12 ℃; the sensory quality of milk samples did not change at 8 and 10 ℃, and began to decline from the 4th d at 12 ℃; the aerobic plate count in the milk samples accorded with the requirement of national standard at 8 and 10℃, and exceeded the national standard on the 5th day at 12℃. No coliform bac- teria were detected in the milk samples within the storage time at 8 ℃. When the milk samples were stored at 10 ℃, the coliform group count exceeded the national standard on the 5th day. When the milk samples were stored at 12 ℃, coliform bacteria began to be found in the milk samples from the 2rd day, and the coliform group count exceeded the national standard from the 3rd day. It indicated that stor- age time had a great impact on the quality of glass bottled pasteurized milk. Low storage temperature and relatively short storage time were conducive to the reten- tion of high quality of pasteurized milk. Coliform group count was one of the impor- tant factors affecting the quality of glass bottled pasteurized milk during shelf life.
巴氏杀菌乳受冷链的影响,一般货架期较短。通过对玻璃瓶装巴氏杀菌乳在不同贮存温度8、10和12℃下的微生物指标、理化指标和感官品质进行评估,探讨不同温度下影响巴氏杀菌乳货架期品质的主要因素。研究表明,在1-5 d时间内,不同贮存温度下,样品的蛋白质、脂肪、乳糖和非脂乳固体几乎不变;酸度在8和10℃下几乎不变,而12℃时有所增加;样品在8和10℃的感官品质不变,而12℃的样品在第4 d感官品质开始下降;微生物指标检测结果表明,在5 d保质期内,样品菌落总数在8和10℃贮存均符合国家标准,而12℃贮存第5 d其结果超过国家标准;样品大肠菌群,在5 d保质期内,8℃贮存时未检出,10℃贮存第5 d超出国家标准;12℃贮存第2d开始检出大肠菌群,第3 d超出国家标准。说明贮存温度的控制对样品品质的影响非常重大,低的贮存温度及相对短的贮存时间有利于巴氏杀菌乳优良品质的保持。结果同时表明大肠菌群数量是影响玻璃瓶巴氏杀菌乳货架期品质的重要因素之一。
