Rheological and microstructural properties of rennet gel made from caprine milk treated by HP

Abstract

Caprine milk has poor rheological properties, which usually result in low cheese yield, as well as economic loss to cheesemakers. Several methods had been used to improve its coagulation properties. However, high pressure (HP) had been rarely used. With the aim of improving the milk coagulation properties, this study therefore assessed the effects of HP treatment on caprine milk before rennet-induced coagulation. Additionally, the rheological, textural, microstructural characteristics and water-holding capacity of the curds were evaluated as a function of pressure (300, 400 and 500 MPa), holding time (20, 40 and 60 min), and temperature (20, 40 and 60 °C) using a response surface methodology. The Box-Behnken design was used to investigate the effect of process variables. The results showed that with an increase in pressure level or holding time, or a decrease in temperature, the rennet coagulation time showed a decreasing trend while curd firming rate and coagulum strength showed the opposite. Also, an increased pressure level, temperature and time resulted in an increase in water-holding capacity and a subsequent decrease in the gel-firmness of the curds. The trend of the results was confirmed by Scanning electron micrographs of the curds. HP could therefore be an alternative technology for improving the coagulation properties of caprine milk.