Study On Stress Crack Characteristics And Quality Of Xiaozhan Rice Stored At Middle And Low Temperature

Compared with storage at room temperature,the quality of rice stored in large-scale cold storage can be retained for longer,but there is a lack of research on how the quality of Xiaozhan rice will change during storage at low temperatures.In the process of storage of rice,broken rice will often appear.Cracks in the storage of rice will cause the rice to break,and the taste of the broken rice will be greatly reduced.Studying the quality and cracks of Xiaozhan rice during storage provides a theory for the practical application of Xiaozhan rice storage.The research content of this paper includes three parts:First,through storage experiments,the moisture content,color difference,smell and eating quality of Xiaozhan rice during storage at 273.15K,277.15K,283.15K,288.15K,298.15K are studied.The changes in total protein content,catalase activity and starch content;secondly,the moisture absorption experiment of Xiaozhan rice in a constant temperature and humidity environment is set up according to the change of moisture content of Xiaozhan rice.The relationship between the elastic modulus,Poisson's ratio,and wet linear expansion coefficient and temperature and moisture content of the rice after absorbing moisture was studied.Finally,according to the microstructure of the stress crack of the rice after moisture absorption,the stress cracking was carried out.Theoretical research and low-field nuclear magnetic detection of the water distribution inside the small station rice.According to the experiment,the research results show that:(1)During storage,the moisture content of Xiaozhan rice fluctuates and the color difference increases.With the increase of storage temperature,the content of sulfide gradually decreases,and the aroma of rice becomes weaker.The luster of the rice becomes darker,and the rice grains in the rice no longer maintain their integrity.A small portion of the rice grains appear popped.After the rice is cooled,it forms a solid mass.When chewing,it sticks to the teeth and becomes harder.When the storage temperature is high,the activity of catalase decreases,and hydrogen peroxide accumulates in the rice,accelerating the deterioration.Comprehensive quality index,the suitable storage temperature of Xiaozhan rice is 283.15K and 288.15K.(2)Through moisture content measurement and compression experiments,and the fitting method to obtain the mechanical characteristic parameters of Xiaozhan rice material,it is found that the elastic modulus and Poisson's ratio of Xiaozhan rice are related to temperature and moisture content.The higher the temperature,the higher the moisture content.The elastic modulus and Poisson's ratio of Xiaozhan rice are smaller.Through image processing,the relationship between the wet linear expansion coefficient of Xiaozhan rice and the moisture content and temperature is obtained.The higher the temperature,the higher the moisture content,and the smaller the wet linear expansion coefficient.(3)Through theoretical analysis of cracks in Xiaozhan rice measured by microstructure,the critical expansion force at different absorption temperatures was calculated,and it was found that when the moisture absorption temperature is 277.15K,the critical expansion force is large,and the rice grains are not prone to cracks.When the moisture absorption temperature is 298.15K,the critical expansion force is small,the rice grains are prone to cracks.The low-field NMR results showed that after Xiaozhan rice absorbed water,the proportion of free water and bound water increased.The relaxation time T₂₁of Xiaozhan rice gradually increased with the increase of moisture absorption temperature and moisture absorption time.Towards a higher migration rate.