Effect of ultrasound pretreatment on rennet-induced coagulation properties of goat's milk

Abstract

The effects of ultrasound (US) pretreatment on goat milk before rennet-induced coagulation were studied in order to improve the milk coagulation properties. Skimmed goat milk was subjected to US at 800 W for different times (0-20 min) and various parameters were evaluated. The particle sizes in US pretreated goat milk under the transmission electron microscopy were smaller than in untreated samples. For US pretreated samples, the degree of whey protein denaturation, contents of soluble calcium and phosphorus increased by 9.57%, 16.90% and 13.68%, respectively. The gel firmness, coagulum strength, final storage modulus, cohesiveness, water holding capacity and cross-linking of gels demonstrated marked increase. The turbiscan stability index (TSI) also confirmed the improvement of goat milk coagulation properties with increasing duration of US pretreatment, whereas the gelation time was prolonged.

Keywords: Coagulation properties; Goat milk; Rennet; Ultrasound.