MICROBIOLOGICAL CHARACTERISTICS OF WHOLE MILK AND DAIRY DRINK PROCESSED BY UHT (ULTRA-HIGH TEMPERATURE) DURING ITS SHELF LIFE

ABSTRACT UHT milk and dairy drinks are submitted to the same heat treatment, but they are different products, since the addition of up to 50% of whey is allowed in dairy drinks. The aim of this study was to evaluate the microbiological characteristics of these products in relation to current legislation, during the course of their shelf life. In the present study, 150 samples, 75 of each type of product, from 5 different national brands were analyzed. The 15 samples of each brand were separated into 3 lots containing 5 samples each, analyzed at the beginning, middle and end of the validity period. Upon microbiological analysis all UHT milk samples were in conformance with current legislation. After the samples were opened and chilled for 48 hours, 26.6% of them presented an increased psychrotrophic population. The dairy drink results showed that 12% of the samples were out of conformance with the current legislation. After the samples were opened and chilled for 48 hours, 36% of them presented an increased psychrotrophic population. These results should be considered as an alert in regard to the need for rigorous inspection of UHT milk and dairy drink products.

摘要：超高温灭菌奶（UHT milk）与乳制品饮料虽采用相同的热处理工艺，但二者属于不同产品，因乳制品饮料允许添加最高50%的乳清。本研究旨在评估两类产品在保质期内的微生物学特性，并对照现行法规进行验证。本研究共采集并分析了来自5个国内品牌的150份样品，两类产品各75份。每个品牌的15份样品被分为3个批次，每批次5份，分别在保质期的初期、中期及末期开展检测。微生物学分析结果显示，所有超高温灭菌奶样品均符合现行法规要求。将样品开封并冷藏48小时后，26.6%的样品嗜冷菌群（psychrotrophic）数量出现上升。乳制品饮料的检测结果显示，12%的样品不符合现行法规要求。将样品开封并冷藏48小时后，36%的样品嗜冷菌群数量出现上升。本研究结果提示，需对超高温灭菌奶与乳制品饮料实施严格的抽检监管，该发现应作为重要警示。