Effects of postharvest storage at room temperature on the quality of south subtropical sweet corn in China

【Objective】 The purpose of the study was to investigate the postharvest storage at room temperature on the quality of excellent sweet corn varieties in Guangdong and Guangxi，so as to provide theoretical basis for the research on preservation technology of postharvest sweet corn and the breeding of new varieties. 【Method】 Treatments was set up at room temperature 0，1，3，and 5 d after harvest. The kernel water content，soluble protein content，soluble sugar content， polysaccharide content，sucrose content and starch content of 6 sweet corn varieties were separately measured after different treatments. The key factors affecting the post harvest quality of sweet corn were evaluated using principal component analysis. 【Result】 As the number of storage day after harvest increased，water content，the soluble sugar content and su‐ crose content decreased in the sweet corn kernels，while the starch content increased. There were great differences in the changes of soluble protein content and polysaccharide content among varieties. Compared with 0 d after storage，the contents of soluble protein，soluble sugar and sucrose in Guitian 619 decreased the most （26.07%，56.22% and 57.03% respectively），while starch content increased the most（101.57%）5 d after storage. Yuetian 38 had the smallest decrease in soluble sugar content（28.75%）and the smallest increase in starch content（14.64%）；Guitian 111 had the smallest decline in sucrose，which was 28.97%. During the postharvest storage period of each variety at room temperature，the highest values of soluble sugar and starch content were 93.47 mg/g and 55.64 mg/g respectively，when Guitan 111 was stored for 1 d； the lowest values of soluble sugar and sucrose content were 33.48 mg/g and 16.72 mg/g for Guitian 619 stored for 5 d. In the average coefficient of variation during the postharvest storage period at room temperature，the coefficients of variation of polysaccharides and starch were large，which were 19.02% and 19.86% respectively. The results of correlation analysis showed that water content was significantly and negatively correlated with polysaccharide content（P<0.05，the same below），and extremely significantly and negatively correlated with starch content（P<0.01，the same below）；soluble sugar content was extremely significantly and positively correlated with sucrose content，and significantly and negatively correlated with starch content. Principal component analysis showed that the cumulative contribution rate of the 3 principal components reached 83.05%，and the soluble sugar，sucrose and starch contents were the main indexes to determine the storage quality of sweet corn after harvest. 【Conclusion】 Postharvest storage at room temperature has significant impact on the quality of 6 sweet corn varieties. The conversion rate of sugar substances and the degradation rate of protein among different sweet corn varieties has great differences. The soluble sugar，sucrose and starch content can be adopted as primary reference indexes for evaluating the quality of sweet corn stored at room temperature after harvesting.