Effects of cold storage on the quality parameters of goat milk

The small-scale goat milk production requires its storage, and such operation is allowed by Brazilian laws. This study aimed at evaluating the cooling and freezing effects on physical-chemical and microbiological characteristics of goat milk. However, no variability was verified in average acidity, alcohol stability, density, fat protein, total solids and lactose values after cold storage. Heat instability was not observed in any of the analyzed samples. There was a decreasing tendency in the somatic cell count (SCC) of frozen milk in comparison to fresh and refrigerated milk. The quantification (NMP) of total and thermo-tolerant coliforms varies from < 3 (no growth) to > 1,100 UFC/mL, regardless of the storage method. However, a slightly higher count (p < 0.0001) was observed for total and thermo-tolerant coliforms in the samples kept under refrigeration. In the lacto-fermentation test, digested, flocculated and grooved clots were observed without establishing a correlation between them and the bacterial count. SCC and microbial count are the criteria adopted when paying for the quality of goat milk, and the storage temperature may affect these criteria.

小规模山羊奶生产需进行储存作业，该操作符合巴西相关法律规定。本研究旨在评估冷藏与冷冻处理对山羊奶理化及微生物学特性的影响。然而，经冷藏储存后，山羊奶的平均酸度、酒精稳定性、密度、脂肪与蛋白质含量、总固形物及乳糖含量均未出现显著变化。所有待测样本均未观察到热不稳定性现象。与鲜羊奶及冷藏羊奶相比，冷冻羊奶的体细胞计数（Somatic Cell Count, SCC）呈下降趋势。总大肠菌群与耐热大肠菌群的最大似然数（Most Probable Number, NMP）范围为<3（无生长）至>1100 UFC/mL，且不受储存方式影响。然而，冷藏储存的样本中总大肠菌群与耐热大肠菌群的计数略高（p < 0.0001）。在乳酸发酵试验中，观察到了消化状、絮凝状及沟槽状凝块，但未发现这些凝块形态与细菌计数之间存在相关性。体细胞计数与微生物菌落数是山羊奶品质计价的判定标准，而储存温度会对该标准产生影响。