Sanjose Carmen, Fernandez Leonides, Palacios Petra
Departamento de Higiene y Tecnología de Alimentos, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.
J Food Prot. 1987 Dec;50(12):1004-1008. doi: 10.4315/0362-028X-50.12.1004.
Changes in milk native content of several carbon and nitrogen sources were studied, along with growth at 7°C of a Pseudomonas fluorescens strain. The aim was to characterize the particular compositional environment in milk in which psychrotrophic bacteria produce their extracellular proteinases. Glucose and lactate were depleted from milk, pyruvate and gluconate were significantly diminished, but citrate was mostly unused when proteinase was first detected by the Hide Powder Azure assay, the psychrotrophic count being around 10 CFU/ml. At that stage, levels of ammonia, amino acids and short peptides had just started to rise and only about 20% of the original urea had been consumed. A procedure to anticipate, in cold stored raw milk batches, the time for production of extracellular proteinase, on the basis of sensitive lactate and ammonia determination, is suggested.
研究了几种碳源和氮源在牛奶中的天然含量变化，以及荧光假单胞菌菌株在7°C下的生长情况。目的是确定牛奶中嗜冷菌产生细胞外蛋白酶的特定组成环境。当用藏红粉天青法首次检测到蛋白酶时，牛奶中的葡萄糖和乳酸已被耗尽，丙酮酸和葡萄糖酸盐显著减少，但柠檬酸盐大多未被利用，此时嗜冷菌数量约为10 CFU/ml。在那个阶段，氨、氨基酸和短肽的水平刚刚开始上升，仅约20%的原始尿素被消耗。建议根据敏感的乳酸和氨测定结果，预测冷藏生牛奶批次中细胞外蛋白酶产生的时间。
