Effects of imbibition and modified atmospheres on the soluble sugar content of supersweet sweet corn embryo and endosperm

The contents and compositional changes of soluble sugars in ‘Supersweet Jubilee’ sweet corn kernels exposed to 0, 24, 48 and 72 h water imbibition and modified atmospheres were determined. In the unimbibed dry embryo, sucrose and raffinose constituted a major pool of soluble sugars. There were two to three times more sucrose and raffinose in the embryo than in the endosperm. With progressive duration of imbibition, these sugars decreased five to eight-fold in the embryo and two to eight-fold in the endosperm. Concurrently, the glucose of the imbibed embryo increased significantly and coincided with the time of radicle emergence. Fructose of embryo and endosperm remained relatively unchanged. Modified atmospheres having 4% oxygen or 10% carbon dioxide and normal atmosphere imposed on imbibing sweet corn kernels did not significantly alter the content and composition of soluble sugars, or firmness of the pericarp. However, over half the kernel soluble sugars content was leaked into the external medium during imbibition; with glucose, fructose and sorbitol being the major sugars leaked. The liberal leakage of soluble sugars from the sweet corn kernels during the first 72 h of imbibition may predispose planted supersweet sweet corn to microbial decay.