CONTENTS OF TASTE-RELATED COMPONENTS OF SUGARS, ORGANIC-ACIDS AND FREE AMINO-ACIDS IN CURRENT SWEET CORN (ZEA-MAYS L) KERNELS

Taste-related components such as sugars, organic acids and free amino acids in sweet corn kernels were determined. The samples were commerci al four sweetness-enhanced cultivars available in current markets of f resh vegetables including yellow, white and bicolor kernel types. Thes e new cultivars showed higher water contents in kernels at harvesting maturity than honey-bantam types which was previous major cultivars in Japan. The cooked kernels of the four cultivars exhibited a good tast e in addition to juicy endosperms and soft pericarps. Sucrose was a do minant sugar and its accumulation (8.44 similar to 9.98 g/100 gFW) of the four cultivars was higher than those of the old types of honey-ban tams. On the other hand, contents of glucose and fructose (0.5 similar to 1.0 g/100 g) in new cultivars were lower than those in old types. Starch including phytoglycans (2.4 similar to 4.3 g/100 g fresh weight ) was present in the kernels corresponding to 25 similar to 50% of suc rose content. Activities of ADP-glucose pyrophosphorylase, a key enzym e of starch synthesis, were much lower in four cultivars than in norma l corns. This was one of the typical properties of super sweet cultiva rs, and was consistent with low starch and high sucrose accumulations in kernels of those cultivars. However, no relationship was observed i n four cultivars between the enzyme activity and starch (or sucrose) c ontent. The levels of total free amino acids, glutamic acid and alanin e was 300 similar to 400, 70 similar to 120 and 80<similar to>110 mg/1 00 gFW, respectively. Since pH of boiled kernel was estimated to be 7. 1+/-0.2 in all four cultivars, glutamic acid would be present as mono potassium salt having umami-taste. The most abundant organic acid was malic acid followed by alpha-ketoglutaric acid, citric acid and succin ic acid. Although the total contents were high (ca. 0.3 g/100 gFW), th ey would not affect sour-taste. There were no differences in the amoun ts of sugars, organic acids and free amino acids except sucrose syntha se activities between white kernels and yellow kernels of the same ear s in a bicolor kernel type.