We assessed the impact of stirring (ST), high shear dispersing (HSD) and low (LPH, 3.5 MPa) and high pressure homogenization (HPH, 50 MPa) on physicochemical and structural characteristics of whole and skimmed sheep milk fresh or previously frozen and thawed (FT). Freezing affected the size of the fat globules, their interaction with caseins, reduced calcium solubility (10%) and buffering capacity (5–11%). Amongst the studied processes, HSD was the only one unable to improve the milk stability. The other ones reduced the size of the fat globules and increased fat and casein interactions, favoring milk stability and reducing the creaming occurrence (>22%). LPH and HPH also reduced the sedimentation in skimmed milk (>37%). Moreover, all processes recovered the buffering capacity of FT samples. The effectiveness of the processes can be ordered as ST < LPH < HPH, but the final choice will depend on the stability improvement required for milk vs. acquisition and operational equipment costs.

Practical application

Sheep milk is normally not homogenized because it has a lower fat globule size than cow milk, which reduces the creaming occurrence. However, creaming happens in some instances and it can be intensified if the milk is preserved frozen (to accumulate enough volume) prior to the dairy production, causing defects in the final products (mainly yogurts). The studied physical processes can be strategically used to solve this problem, increasing the milk emulsion stability, reducing the sedimentation occurrence and changing the buffering capacity to reach the same value of fresh milk.

中文翻译：

---

利用物理过程改善鲜奶和冷冻/解冻羊奶的理化和结构特性

我们评估了搅拌（ST），高剪切分散（HSD）和低（LPH，3.5 MPa）和高压均质化（HPH，50 MPa）对新鲜或先前冷冻的全脂和脱脂羊奶理化和结构特征的影响。解冻（FT）。冷冻影响脂肪球的大小，它们与酪蛋白的相互作用，降低的钙溶解度（10％）和缓冲能力（5-11％）。在所研究的过程中，HSD是唯一无法改善牛奶稳定性的过程。其他的减少了脂肪球的大小，增加了脂肪和酪蛋白的相互作用，有利于牛奶的稳定性并减少了乳脂的产生（> 22％）。LPH和HPH还减少了脱脂牛奶中的沉淀（> 37％）。而且，所有过程都恢复了FT样品的缓冲能力。

实际应用

绵羊奶通常不均质，因为它的脂肪小球尺寸比牛奶低，从而减少了乳汁的产生。但是，在某些情况下会发生乳脂状，如果在乳制品生产之前将牛奶冷冻保存（以积累足够的体积），则会加剧乳化现象，从而导致最终产品（主要是酸奶）出现缺陷。研究的物理过程可以从战略上解决这一问题，从而提高牛奶乳液的稳定性，减少沉淀的发生并改变缓冲能力以达到与新鲜牛奶相同的价值。