Abstract:
As a whole grain food with high content of moisture and rice bran, fresh brown rice noodles are perishable, including retrogradation and rancidity. The quality of fresh brown rice noodles deteriorates rapidly and the shelf life is short, which seriously affects its market circulation. It is of great significance for the quality management and control of fresh brown rice noodles to establish a dynamic model of quality change for brown rice noodles. However, there are few studies on predicting the quality change and shelf life of fresh brown rice noodles. In the study, the pH value, cooking loss rate, hardness before and after cooking of fresh brown rice noodles were determined after stored at 4 ℃ for 0, 24, 48, 72, and 120 h, 25 ℃ for 12, 24, 36, 48, and 60 h, and 37 ℃ for 6, 12, 18, 24, and 30 h, respectively. Each data and the logarithm of each data were analyzed by linear regression, and the reaction rate constant
k and the determination coefficient R
2 were obtained to determine the reaction order of index changes. According to the reaction rate constant
k of each index at different storage temperatures, ln
k and the reciprocal of thermodynamic temperature were substituted into the Arrhenius equation, and
Ea and
A were calculated according to the Arrhenius equation.
Ea and
A were brought into the equation combined with the reaction kinetic model equation and Arrhenius equation, and the reaction kinetic model equation of the index was obtained. Finally, the reaction kinetic model equation was validated by calculating the percentage error between the true and predicted values. The results showed that the pH value and hardness after cooking of fresh brown rice noodles were gradually decreased, and cooking loss rate and hardness before cooking of fresh brown rice noodles were gradually increased with the increase of storage time. The storage temperature was higher, and the changes of pH value, cooking loss rate, and hardness after cooking of fresh brown rice noodles were higher. The hardness before cooking of fresh brown rice noodles was significantly increased when fresh brown rice noodles were stored at 4 ℃, which was mainly attributed to the easy retrogradation of starch stored at 4 ℃. The changes of pH value and cooking loss rate of fresh brown rice noodles were accorded with the first-order reaction, and the fitting coefficient
R2 of the model was 0.955 0 and 0.999 5, respectively. The changes of hardness before and after cooking were accorded with the zero-order reaction, and the fitting coefficient
R2 of the model was 0.963 2 and 0.984 8, respectively. The four models have been well verified, and can be used to predict the quality changes of fresh brown rice noodles during storage process at 4-37 ℃.