CAO Zhijun, YU Jingdan, GUO Jingxian, LIU Min
To evaluate the feasibility of Pichia pastoris (JR-21) on promoting the ripening of cheddar cheese, the fermentation broth of Pichia yeast (JR-21, JR-42, M-19) was evaluated, and JR-21 strain was selected as the yeast for the subsequent fermentation of Cheddar cheese, two different types of cheddar cheese were prepared without addition (control) and with auxiliary starter culture (JR-21), and the texture and flavor parameters of the two cheeses were measured during the 40-day maturation period, and the effects of Pichia pastoris on the physicochemical characteristics, texture and flavor changes of cheese during the ripening period were explored.Results showed that with the extension of the ripening period, there were no significant differences in moisture content or protein content between the two groups (P>0.05). At 0 d of cheese ripening, the pH values of the two groups showed a significant difference (P<0.05). Between 30 and 40 d of ripening, the changes in fat content between the experimental group (M) and the control group (S) differed significantly (P<0.05), in which the addition of JR-21 fermented cheese produced organic acids, polysaccharides, and protein binding to increase the compactness of the protein network structure, making its hardness and chewiness higher than that of the control group, while the elasticity, cohesion, and adhesion did not change significantly, compared with the control group, the addition (JR-21) made the cheese appear honeycomb structure, forming the iconic “eye” pores.With the extension of the ripening period, the two kinds of cheese contained acids, alcohols and esters, and the characteristic flavor compounds detected by the addition (JR-21) fermented cheese at 40 days of maturation were the most abundant, mainly including organic acids such as caprylic acid and acetic acid, alcohols such as ethanol and isoamyl alcohol, and various ester compounds such as ethyl caprate and ethyl caprylate.The control group reached a peak at 30 days and included only 6-caprylic acid, acetic acid, ethanol, ethyl caprate, ethyl caprylate, and ethyl caproate.The addition of Pichia pastoris changed the content and proportion of different organic acids in cheese, and the content and proportion of alcohols and esters synthesized with them as precursors also changed, among which ethanol, isoamyl alcohol, 1-pentanol, ethyl caprate, ethyl caprylate, ethyl heptanoate, amyl formate and ethyl acetate were significantly higher than those in the control group in the addition (JR-21) fermented cheese.Therefore, the addition of Pichia pastoris JR-21 can effectively promote protein breakdown and cheese maturation, while improving the flavor and texture of cheese.