Effects of the sowing dates on the nutritional and edible quality of sorghum

To determine the suitable sowing date of sorghum and realize high quality and efficient production, three sowing dates of April 30 (T1), May 14 (T2), and May 28 (T3) during 2013-2014 were set with sorghum 'Liaoza 11' and 'Shenza 5' as the experimental materials. After harvest, the yield and nutritional contents of crude protein, tannin, crude fat, amylose, and amylopectin in the grains were measured. The viscosity of sorghum starch was measured using a Rapid Visco Analyzer (RVA), and the edible qualities were evaluated. Meanwhile, the effects of meteorological factors on the nutrition and edible quality of sorghum were analyzed. The results showed that a delay in the sowing date could significantly increase the yield of 'Shenza 5' but had no significant effect on 'Liaoza 11'. With the delayed sowing dates, the contents of crude protein and tannin in the grain decreased, while the contents of amylose, amylopectin and total starch increased. The delay in the sowing date also increased the peak viscosity, break down viscosity, final viscosity, and expansion rate of sorghum starch. As a result, the taste scores of the two sorghum hybrids increased with the delayed sowing dates. Compared with that of T1 and T2, the taste score of 'Liaoza 11' in T3 increased by 11.86%-12.81% and 6.83%-8.44%, respectively. Compared with that of T1 and T2, the taste score of 'Shenza 5' in T3 increased by 6.48%-7.18% and 3.33%-4.06%, respectively. The contents of crude protein and tannin were negatively correlated with the eating quality (except for the texture of cold porridge), and the contents of crude fat, amylose, amylopectin, and total starch were significantly or very significantly positively correlated with the edible quality. The peak viscosity, hot pulp viscosity, break down value, final viscosity, and consistence viscosity were significantly or very significantly positively correlated with the palatability, taste, and smell. We can conclude that a late sowing date (May 28 in Shenyang) can reduce the contents of crude protein and tannin of sorghum, and increase the contents of amylopectin, which led to an increase in the peak viscosity and beak down value of sorghum, resulting in an improvement in the edible quality.