Effect Of Fat Content On Cheese Quality And Fat Degradation During Yak Milk Hrad Cheese Ripening

Fat degradation is an important reaction in the cheese maturation process,it will lead to the deterioration of cheese texture,flavor,color,fatty acid,etc.during processing,maturation,storage and transportation.Therefore,exploring the law of fat content on the oxidative degradation of fat and fatty acid oxidation during the mature period of yak milk hard cheese provides a theoretical basis for the industrial development of yak milk.In this experiment,fresh yak milk from Gansu gannan Tibetan autonomous prefecture was used as the raw material,three kinds of hard yak cheese(full fat,semi-fat and low fat)were prepared with skim yak milk and full fat yak milk by volume ratio of 0:1,1:1 and 2:1,to study the effects of fat content on cheese quality and fat degradation during cheese ripening.Determine the functional characteristics of fresh yak milk hard cheese,dynamically monitor the physical and chemical,color,texture,microstructure and oxidation degree of cheese during the ripening process of 0-6 months,and use gas chromatography mass spectrometry to determine the ripening process Cheese fatty acids.The main results are as follows:(1)The fat content affects the cheese yield and has a certain influence on the rheological properties and cheese sensory quality.The fat content of full-fat,semi-defatted and low-fat cheese was 41.85%,20.31% and 14.25%,the production rates were 15.6%,13.03% and10.83%,respectively,full-fat> semi-fat> low fat.The lower the fat content in fresh cheese,the greater the elastic modulus;the higher the fat content,the greater the viscoelastic properties;and the sensory score in the cheese is directly proportional to the fat content.(2)The fat content in cheese affects the physical and chemical indicators,texture and microstructure of cheese.The fat content of the cheese is inversely proportional to the moisture content and proportional to the NaCl content and pH value;the brightness and yellowness are directly proportional to the cheese fat content,the greenness decreases with the increase of fat content;hardness,chewability It is inversely proportional to elasticity and fat content,and cohesiveness is proportional to fat content.The microstructure of cheese changes with the change of fat content.The fat particle size distribution is: full fat> semi-fat>low fat,full fat cheese fat balls are tight,full fat cheese fat balls are tightly distributed,and fat fat balls in low fat cheese It is more dispersed;as the cheese matures longer,the NaCl content increases,the water content decreases,and the pH value decreases first and then increases;the brightness decreases,the greenness and yellowness increase;the hardness,elasticity,and cohesiveness decrease;Chewing increased.In the microstructure,fat is degraded,the cavity(3)becomes larger and sparse,the structure is relatively loose,and the diameter of the fat sphere increases,forming a "fat trough".(4)The cheese fat content affects the degree of cheese oxidation.During the maturation process,the activity of lipoxygenase decreased with the extension of maturation time.The CV value,ADV value and TBA value of the three cheeses were proportional to the maturation time,and the POV value increased first and then decreased.With the increase of fat content,the four oxidation indexes of lipoxygenase activity,ADV,POV,CV and TBA all decreased.Throughout the maturation process,the fat oxidase activity of 6-month full-fat,semi-defatted and low-fat cheese was reduced by 87.76%,81.19% and 79.45% compared to the 0-month cheese.Low-fat cheese has the smallest decrease in enzyme activity.(5)During the ripening process of full-fat,semi-defatted and low-fat cheese,there are five main fatty acids: oleic acid,palmitic acid,myristic acid,isoleic acid and stearic acid.The TFA content of full-fat,semi-defatted and low-fat cheese at 0 months was 92.24%,93.19%and 95.78%;the TFA content of full-fat,semi-fat and low-fat cheese at 6 months was 95.52%and 98.64%,respectively.And 99.77%,the TFA content of yak milk low-fat cheese is higher than that of semi-defatted and higher than full-fat cheese,and the fat content has a significant effect on the TFA content of cheese.The content of short,medium,and long-chain fatty acids is low fat> semi-fat> full fat.In summary,during the ripening of yak milk cheese,the fat content is closely related to the cheese quality.Milk fat content is inversely proportional to fat degradation,the antioxidant capacity of cheese is positively correlated with milk fat.The more fat content,the faster the fat oxidase activity declines during the ripening process,and the slower the fat degradation,high fat and low oxidation.This provides a theoretical basis for the industrial development of yak milk cheese in China.