Response of rice taste quality to nitrogen fertilizer during storage

【Objective】 Clarify the relationship between nitrogen fertilizer level and storage time and rice taste quality, in order to provide theoretical basis for the actual production and storage of high-quality rice.【Method】 High-yielding and high-quality rice, Deyou 4727(low-nitrogen high-efficiency type) and Jingyou 781(low-nitrogen low-efficiency type), were used as test materials. And set four nitrogen fertilizer levels as 0 kg/ha(N0), 90 kg/ha (N1), 150 kg/ha (N2), 270 kg/ha (N3), the yield of rice produced under different nitrogen fertilizer levels and the changes of its protein, amylose content, starch viscosity and other taste qualities after storage for 3 months and 12 months were analyzed. The correlation between storage time and cooking flavour quality was also analyzed.【Result】 Yield, protein content and straight-chain starch content of Deyou 4727 and Jingyou 781 increased with increasing nitrogen application, the yield of N2 treatment increased the most, which were 31.63% and 28.86% respectively. The contents of protein and amylose in N3 treatment increased more than those in the other three treatments, and the taste value was the lowest. After 12 months of storage, the cooking and eating quality under N3 treatment was worse than other treatments. Nitrogen fertilizer level was significantly correlated with storage quality of rice(P<0.05, the same below). After 12 months of storage, the increased application of nitrogen fertilizer led to the deterioration of the taste quality of rice. The rate of change in taste value of Deyou 4727 after 12 months of storage under N3 treatment was 13.36%, which was significantly higher than that of N0, N1 and N2 treatments;the rate of change in taste value of Jingyou 781 under N3 treatment was 18.19%, which was significantly higher than that of N0 and N1 treatments. The change rates of amylose content of Deyou 4727 and Jingyou 781 were 14.02% and 8.86% respectively in N3 treatment, which were significantly higher than N2 treatment. Rice storage time showed extremely significant positive correlations with straight chain starch content, protein content, pasting temperature, abatement value and recovery value(P<0.01, the same below), and extremely significant negative correlations with flavour value, peak viscosity, cold gel viscosity, hot slurry viscosity and disintegration value.【Conclusion】 Deyou 4727 and Jingyou 781 have the highest yield increase and the best taste quality when the nitrogen fertilizer level is 150 kg/ha. Over application of nitrogen fertilizer not only affects the edible quality of rice, but also accelerates the aging of rice during storage.