Abstract:

Milk of white yaks grazing pastures in Tianzhu county, Gansu province was processed into hard cheese. The processing parameters were optimized using one-factor-at-a-time and orthogonal array design in which the interactions between the variables were neglected. In addition, cheese products in ripening period were subjected to analysis of proximate composition and microstructure observation under SEM. High hard cheese yield and good sensory quality both could be achieved when addition amounts of fermentation starter, rennet and CaCl2 were 3%, 30 μl/100 ml and 0.03%, respectively, temperature 40℃, and pH 6.1. The product on the 30th day of ripening contained 27.82 % protein and 36.43% fat, and the yield was 15.5%; no significant microstructure changes were founded during ripening (observed on the 30th, 60th and 90th day).

Key words: milk of white yak, hard cheese, processing technology, microstructure, SEM