Ginn Roy, Packard Vernal
Dairy Quality Control Institute, Inc., 5205 Quincy St., St. Paul, Minnesota 55112.
Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108.
J Food Prot. 1990 Dec;53(12):1073-1075. doi: 10.4315/0362-028X-53.12.1073.
Standard Methods for the Examination of Dairy Products () requires that milk be sampled cold for analysis of both bacteria and somatic cells by the direct microscopic method. Preliminary observations made at Dairy Quality Control Institute, Inc. indicated that better precision in somatic cell counting could be obtained if milk was sampled at 38°C rather than 0-4.4°C. A study was undertaken to confirm preliminary findings. Three technicians made direct microscopic somatic cell counts (DMSCC) in triplicate on milk samples standardized to four different levels of counts. The grand average counts at the four levels of cells for cold vs warm milk sampling were, in thousands of cells per ml, 149 vs 154, 410 vs 416, 705 vs 697, and 1034 vs 1024. Grand average standard deviations for cold vs warm, respectively, at the four levels of count were 19 vs 17, 47 vs 42, 54 vs 50, and 69 vs 62. Thus, an improvement in precision of counting was observed at all four levels of somatic cells when raw milk is warmed to 38°C prior to sampling.
《乳制品检验标准方法》要求，通过直接显微镜法对牛奶进行细菌和体细胞分析时，应在低温下采样。乳制品质量控制研究所进行的初步观察表明，如果牛奶在38°C而非0 - 4.4°C下采样，体细胞计数的精度会更高。为此开展了一项研究以证实初步研究结果。三名技术人员对标准化至四种不同计数水平的牛奶样本进行了三次重复的直接显微镜体细胞计数（DMSCC）。低温采样与高温采样时，四个细胞水平下的总平均计数（以每毫升细胞数千个计）分别为149对154、410对416、705对697以及1034对1024。四个计数水平下，低温采样与高温采样的总平均标准差分别为19对17、47对42、54对50以及69对62。因此，当原料奶在采样前加热至38°C时，在所有四个体细胞水平上均观察到计数精度有所提高。
