Influences of seasonal variations in contents of glycogen and its metabolites on browning of cooked scallop adductor muscle

Seasonal variations in contents of glycogen and its metabolites in scallop adductor muscle and their influences on browning during cooking were studied. Glycogen content was lowest in January (0.49%) and highest in June (6.60%). The content of glucose ranged between 0.1 and 0.9 mu mol/g in winter and spring, and exceeded 1 mu mol/g in summer when glycogen was abundant, and it retained the level through autumn. The content of glucose-6-phosphate (G6P), which amounted to about 80% of total amounts of sugar phosphates, varied from 0.3 to 3.5 mu mol/g, and tended to be abundant in summer. During storage of unfrozen scallop adductor muscle, glycogen was converted to G6P. The higher the content of glycogen, the larger the increase in G6P content, which led to a strong browning of cooked muscle. Accumulated G6P during thawing was not affected by glycogen content, though a stronger browning during cooking was observed in the muscle containing larger amounts of glycogen. When frozen and thawed muscle was stored at 5 degrees C after thawing, muscles containing larger amounts of glycogen showed a further increase in G6P, which resulted in an increase in the degree of browning, but muscles containing smaller amounts of glycogen showed decrease in G6P, which resulted in decrease in browning. The glycolysis which progresses during storage and cooking seems to influence the browning of cooked scallop adductor muscle.