Abstract The definition of “quality” raw milk for UHT milk manufacture is not well defined. The UHT process produces a commercially sterile product. However, some proteases produced by bacteria from the raw milk survive UHT treatment, limiting the shelf life of UHT milk. To provide some information on the microbiological quality limits for raw milk for the manufacture of UHT products, bacterial isolates (Pseudomonas) showing heat-stable proteolytic activity and commonly found in raw milk were grown to different numbers (4–7 log cfu mL−1) in UHT milk and then the milk was UHT treated again. The storage life of this product was monitored over different temperatures (20, 30 and 55 °C) and time periods (up to 9 months). With this information guidelines for the manufacture of UHT milk with a specific shelf life can be made based on the initial microbiological content of the raw milk.

中文翻译：

---

用于生产超高温灭菌牛奶的牛奶中假单胞菌数量与对产品质量影响的关系

摘要 用于 UHT 牛奶生产的“优质”原料奶的定义尚不明确。UHT 工艺生产商业无菌产品。然而，由生奶中的细菌产生的一些蛋白酶在 UHT 处理后仍能存活，从而限制了 UHT 奶的保质期。为了提供有关用于制造 UHT 产品的原料奶的微生物质量限制的一些信息，将显示热稳定蛋白水解活性且常见于原料奶中的细菌分离物（假单胞菌）培养到不同的数量（4–7 log cfu mL−1 ) 在 UHT 牛奶中，然后再次对牛奶进行 UHT 处理。在不同的温度（20、30 和 55 °C）和时间段（最多 9 个月）内监测该产品的储存寿命。