Using physical processes to improve physicochemical and structural characteristics of fresh and frozen/thawed sheep milk

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 applicationSheep 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.