Research on Quality Changes during Japonica Rice Milling Process and Moderate Processing

The study explored the effects of different degrees of milling, including the moderate processing technology on the quality of japonica rice using Longdao 18, Longjing 31, Yanfeng 47, Yujingxiang, and Nanjing 46 rice varieties. The results indicated that as the milling intensity increased, the whiteness of the japonica rice and broken rice rate continuously increased, but the bran retention rate decreased. The taste value first increased and then plateaued, while the content of vitamin B1 and mineral elements generally showed a declining trend. From brown rice to the first stage of milling, there was a significant decrease in protein content. During the milling process, the vitamin B1 content in japonica rice was significantly positively correlated with the levels of magnesium, phosphorus, potassium, calcium, manganese, iron, copper, and zinc. Iron was more concentrated in the outer layers, and reducing the milling degree could significantly increase the retention rate of iron. Analysis of the coaxial curve diagram based on the proportion of the maximum value in each group relative to the brown-to-white rice yield for broken rice rate, taste value, vitamin B1, and iron content of five japonica rice varieties revealed that the moderate processing range for japonica rice corresponds to a brown-to-white rice yield of 88% to 92%. Within this range, the taste value of japonica rice reached its highest level, and more vitamin B1 and mineral elements such as iron were retained.