Influence of milk with a high somatic cell count on the physical characteristics and yogurt fermentation process

Abstract The aim of this study was to evaluate the fermentation characteristics and yogurts made from milk with high or low milk somatic cell count (CCS) and added or not with milk solids. Raw milk was collected at six days and subjected to various electronic analyzes of protein, fat, lactose, total solids, CCS and total bacterial count (CBT). The profile of the fermentation was monitored by pH and acidity, expressed as lactic acid. Yoghurts were analyzed for pH, acidity expressed as lactic acid and syneresis of final product at different storage times. The experiment was conducted in a randomized block design, with six replicates and split plots with treatments in installments (CCS levels x added or not added milk solids) and fermentation times and storage periods for yogurts subplots. Data were subjected to analysis of variance (ANOVA), regression or Pearson Correlation analysis, according to the tests. The results showed that CCS levels had effects on some milk parameters (p<0,05). However, no effects were observed on the fermentation profile and characteristics of yoghurt during storage, according to the CCS levels or adding milk solids.

摘要 本研究旨在评估不同体细胞数（milk somatic cell count, CCS）牛乳在添加或不添加乳固体条件下的发酵特性，以及由其制备的酸奶品质。本研究于6个采样日采集生鲜牛乳，对其蛋白质、脂肪、乳糖、总固体、体细胞数（CCS）及总细菌数（total bacterial count, CBT）开展多项电子检测分析。发酵过程通过pH值及以乳酸计的酸度进行监测。针对不同贮藏时间下的成品酸奶，分别检测其pH值、以乳酸计的酸度与析水率。本实验采用随机区组设计，共设置6次重复；裂区设计中，主区处理为体细胞数水平与乳固体添加与否的组合，副区处理为酸奶发酵时间与贮藏周期。根据不同检验需求，对实验数据分别实施方差分析（analysis of variance, ANOVA）、回归分析或Pearson相关分析。结果表明，体细胞数水平对部分牛乳理化指标具有显著影响（p<0.05）；但无论体细胞数水平或乳固体添加与否，均未对发酵过程特性及贮藏期酸奶品质产生显著影响。