Impact of high-pressure homogenisation of milk on physicochemical, microbiological, and textural characteristics of sheep milk yoghurt

Yoghurt samples were produced from sheep milk that was high-pressure homogenisation (HPH) treated at 0 (control), 30, 50, 70 and 100 MPa. Depending on the acidification kinetic parameters, HPH treatment increased the acidification rate and shortened the fermentation time. HPH-treated samples had lower pH, increased water holding capacity, decreased syneresis, decreased particle size and higher acetaldehyde content than the control. At 0 and 14 days of storage, the tyrosine value of HPH-treated samples was higher than the control. Although HPH resulted in higher L∗ and a∗ values, it caused lower b∗ values in yoghurt samples. Up to 30 MPa, HPH increased firmness and consistency; however, these were decreased above 50 MPa. During storage, Streptococcus thermophilus and Lactobacillus bulgaricus counts ranged from 6.12 to 8.20 log cfu g−1 and 5.70 to 8.96 log cfu g−1, respectively. Depending on the increasing pressure, HPH caused higher S. thermophilus and L. bulgaricus counts.