Retrospective evalution of non-fatty solids in samples of raw milk in the state of Rio Grande do Sul according to season, Brazil

ABSTRACT: The present study described the chemical composition and somatic cell score (SCS) of samples of refrigerated raw milk collected from commercial farms in the state of Rio Grande do Sul in order to better understand the behavior of constituents present in non-fatty solids (NFS) in milk according to the season of the year. Means were used to describe statistical data. To estimate the probability of NFS levels meeting IN 76 (BRAZIL, 2018), binary logistic regression was used. It was reported that 18.2% (233.817) of analytical results showed NFS below 8.4%, representing the minimum required by IN 76. The highest average NFS level observed in the five-year period was registered in the micro-region of Passo Fundo (8.70%) in winter. The microregion with the lowest results was Porto Alegre (8.53%); however, it still demonstrated levels within the limits established by IN 76. The study indicates that milk constituents show differences between seasons. In autumn and winter, the constituents remained equal to or higher than those required by current legislation, while spring and summer were the periods with the lowest NFS values. The SCS was also influenced by the seasons, with the highest rates in spring, summer, and autumn.

摘要：本研究采集巴西南里奥格兰德州商业牧场的冷藏生乳样本，分析其化学成分与体细胞评分（Somatic Cell Score, SCS），旨在明晰乳中非脂乳固体（non-fatty solids, NFS）的组分特征随季节的变化规律。本研究采用均值法对统计数据进行描述；为估算非脂乳固体含量符合巴西2018年第76号规范性指令（IN 76, 2018）要求的概率，采用二元逻辑回归分析法开展建模。研究结果显示，18.2%的分析结果（对应233817份样本）中非脂乳固体含量低于8.4%，未达到该指令规定的最低限值。五年观测期内，非脂乳固体平均含量最高的区域为帕苏丰杜微区域，冬季测得其平均含量达8.70%；含量最低的微区域为阿雷格里港（8.53%），但其含量仍符合该指令规定的限值要求。本研究表明，乳成分存在显著的季节差异：秋季与冬季采集的乳样组分含量均达到或超过现行法规标准，而春季与夏季为非脂乳固体含量最低的时段。此外，体细胞评分（SCS）同样受季节影响，在春季、夏季与秋季达到峰值。