Zeng S S, Chen S S, Bah B, Tesfai K
E (Kika) de la Garza American Institute for Goat Research, Langston University, Langston, Oklahoma 73050, USA.
J Food Prot. 2007 May;70(5):1281-5. doi: 10.4315/0362-028x-70.5.1281.
Dairy goat herds in the United States generally are small, widely scattered, and distant from processing facilities. Unlike the situation for cow milk, it is not cost-effective to collect goat milk everyday or every other day. In some areas, goat milk is collected only once each week, which is in violation of regulations specified in the Pasteurized Milk Ordinance for grade A milk. This study was conducted to determine the effect of up to 7 days of refrigerated bulk tank storage on composition, somatic cell count (SCC), pH, and microbiological quality of goat milk. Duplicate farm bulk tank samples were taken daily after the morning milking for seven consecutive days each month during the lactation season. Samples were analyzed immediately for all variables except free fatty acids. There were no significant changes (P > 0.05) detected in milk fat, protein, lactose, nonfat solids, SCC, or pH during extended storage, although significant effects of stage of lactation (P < 0.05) were observed. The mean standard plate count (SPC) increased to 1.8 x 10(5) CFU/ml after 6 days of storage, exceeding the grade A limit (i.e., 1.0 x 10(5) CFU/ml). The mean psychrotrophic bacteria count increased steadily to 1.5 x 10(4) CFU/ml after 6 days of storage, whereas the mean coliform count was approximately 500 CFU/ml for the first 3 days and less than 2500 CFU/ml throughout the 7 days of storage. No significant changes (P > 0.05) in the concentrations of free fatty acids, except for butyric and caprylic acids, were observed during milk storage. When stored under refrigerated and sanitary conditions, goat milk in farm bulk tanks met the grade A criteria for both SPC and SCC during 5 days of storage but was of low quality thereafter because of the growth of psychrotrophic bacteria.
美国的奶山羊群规模一般较小，分布广泛且远离加工设施。与牛奶的情况不同，每天或隔天收集山羊奶并不划算。在一些地区，山羊奶每周仅收集一次，这违反了《巴氏杀菌乳条例》中对A 级牛奶规定的要求。本研究旨在确定冷藏储存在奶罐中长达7天对山羊奶的成分、体细胞计数（SCC）、pH值和微生物质量的影响。在泌乳季节，每月连续7天每天早晨挤奶后采集农场奶罐的重复样本。除游离脂肪酸外，对所有变量的样本均立即进行分析。在延长储存期间，乳脂肪、蛋白质、乳糖、非脂固形物、SCC或pH值均未检测到显著变化（P>0.05），不过观察到泌乳阶段有显著影响（P<0.05）。储存6天后，平均标准平板计数（SPC）增加到1.8×10⁵CFU/ml，超过了A级限量（即1.0×10⁵CFU/ml）。储存6天后，嗜冷菌平均计数稳步增加到1.5×10⁴CFU/ml，而在前3天大肠菌群平均计数约为500CFU/ml，在整个7天储存期间均低于2500CFU/ml。在牛奶储存期间，除丁酸和辛酸外，游离脂肪酸浓度未观察到显著变化（P>0.05）。在冷藏和卫生条件下储存时，农场奶罐中的山羊奶在储存5天内符合SPC和SCC的A级标准，但此后由于嗜冷菌的生长质量较低。
