Study On The Changes Of Static, Transient Rheological Properties And Microstructure During Cheese Ripening

The changes of static, transient rheological properties and microstructure during the cheese ripening from Od to 180d were studied. The purpose was to explore the correlation of cheese maturity and rheological properties. Cheese samples for the maturity of 180d and cheese samples for different fat content were manufactured. The samples were measured by uniaxial compression test, stress relaxation test, creep test, TPA test and scanning electron microscope observations during 180d ripening. The samples for different fat content were measured by physicochemical indexes, TPA test, stress relaxation test during 45d ripening. The degree of protein and fat hydrolysis of cheddar cheese was reflected by microstructure electron scanning in the process of maturity. During cheese ripening for 0-180d cheddar cheese and 0-45d different fat content cheeses, the results of the experiment were as follows:(1)For the sample of 180d maturity, protein and moisture decreased significantly during ripening. pH decreased at first and then increased, change extent is not big. During ripening period, no significant changes of salt content were observed.(2)During cheese mature process, the elastic modulus decreases gradually. The elastic linear range became smaller with ripening time.(3)Relaxation time and Deborah number in mature 0-15d increased and they were up to the maximum level λrel=184 s and De=0.61, then decreased gradually. The stress relaxation time and cheese maturity index showed a significant linear negative correlation. This indicated that the more mature cheese, the greater the viscosity.(4)Based on Peleg and Normand model for stress relaxation characteristic parameters ki, k2 gradually declined with mature period. It showed that relaxation strength weakened of 0-180d cheddar cheese in the mature process and viscosity increased.(5)Initial creep compliance Jo, delay creep compliance J1 increased with mature period gradually.(6)The results of TPA tests showed that the hardness, gumminess and chewiness decreased significantly as ripening progress for the sample of 180d maturity. The adhesives increased during ripening. Springiness increased after the first down. The cohesiveness decreased during ripening.(7)Microstructure electron scanning results showed that with the extension of maturity, the volume of fat decreased. Protein hydrolysis increased and protein micelles become fragmented. With the protein hole became bigger, cheese structure weakened fragile during the ripening period 0-180d.(8)The rheological properties and textural properties of cheeses with different fat content were tested. Increase in the fat content of cheese resulted in the decrease of hardness, relaxation time and Deborah number.