Animal Products Inspection Laboratory, Paraná, 86.057-970, Brazil.
Animal Products Inspection Laboratory, Paraná, 86.057-970, Brazil.
J Dairy Sci. 2018 Jan;101(1):75-83. doi: 10.3168/jds.2017-13069. Epub 2017 Nov 6.
Refrigerated raw milk may contain psychrotrophic microorganisms that produce thermoresistant exoproteases and lipases, which may compromise the quality of processed fluid milk and dairy products during storage. The aim of this work was to quantify and identify the deteriorating psychrotrophic microbiota in Brazilian refrigerated raw milk using genetic diversity analysis. The mean psychrotrophic count was 1.1 × 10 cfu/mL. Of the total isolates, 47.8 and 29.8% showed deteriorating activity at 35°C within 48 h and 7°C within 10 d, respectively. Among the proteolytic species, more isolated by this study were Lactococcus lactis (27.3%), Enterobacter kobei (14.8%), Serratia ureilytica (8%), Aerococcus urinaeequi (6.8%), and Bacillus licheniformis (6.8%). Observed among lipolytics were E. kobei (17.7%), L. lactis (15.6%), A. urinaeequi (12.5%), and Acinetobacter lwoffii (9.4%). The isolates S. ureilytica, E. kobei, Pseudomonas spp., and Yersinia enterocolitica potentially produced alkaline metalloprotease (aprX). Despite the low counts, a considerable portion of the psychrotrophic microbiota presented spoilage potential, which reaffirms the need for rigor in the control of contamination and the importance of rapid processing as factors that maintain the quality of milk and dairy products.
冷藏生牛乳可能含有嗜冷微生物，它们会产生耐热的外蛋白酶和脂肪酶，这可能会在储存过程中影响加工液态奶和乳制品的质量。本工作的目的是使用遗传多样性分析来量化和鉴定巴西冷藏生牛乳中变质的嗜冷微生物群。嗜冷菌的平均计数为 1.1×10 cfu/mL。在总分离株中，分别有 47.8%和 29.8%的分离株在 35°C 下 48 小时内和 7°C 下 10 天内表现出变质活性。在蛋白酶种中，本研究分离到更多的乳球菌（27.3%）、肠杆菌科（14.8%）、尿液化沙雷氏菌（8%）、尿生殖道阿克曼氏菌（6.8%）和地衣芽孢杆菌（6.8%）。在脂肪分解菌中，观察到肠杆菌科（17.7%）、乳球菌（15.6%）、尿生殖道阿克曼氏菌（12.5%）和阿克曼氏菌（9.4%）。分离到的尿液化沙雷氏菌、肠杆菌科、假单胞菌和小肠结肠炎耶尔森菌可能产生碱性金属蛋白酶（aprX）。尽管计数较低，但相当一部分嗜冷微生物群具有变质潜力，这再次证实了严格控制污染和快速加工的重要性，这是保持牛奶和乳制品质量的因素。
