Effect of high hydrostatic pressures and milk pasteurization on yogurt quality made with sheep milk

The objective of this work was to study the effect on physicochemical, rheological and sensory parameters of a yogurt made with ewe milk treated by high hydrostatic pressure compared to a traditional yogurt made with pasteurized milk.

For this purpose, Churra ewe's milk was collected and divided into two batches with their replicas. One batch was subjected to high hydrostatic pressure treatment (600MPa, 6 minutes at 20° C) and the second batch was pasteurized (92° C, 5 minutes).

Fermentation was carried out at 42° C by inoculation of a Lactobacillus bulgaricus and Streptococcus thermophilus started.

Treatment with high hydrostatic pressure significantly (p <0.05) affected the fat content, dry matter and colour parameter b*.

Likewise, yogurts made with milk treated at high pressure did not show significant differences in texture parameters, except for adhesiveness, with respect to yogurts made with pasteurized milk.

At the rheological level, both treatments showed elastic thixotropic behaviour with higher values ​​for elastic modulus (G´), viscous modulus (G´´) and apparent viscosity in yogurts made with pasteurized milk.

Sensory analysis, using a trained tasting panel, resulted in significant differences (p <0.05) in sliminess, creaminess, flavour and overall preference where the high-pressure batches received the best scores.

In conclusion, the treatment showed significant differences, being yogurts made with milk treated with high hydrostatic pressure the best evaluated in the sensory analysis.