Two rice varieties in Korea, an Indica type $quot;Tongil$quot; and a Japonica type $quot;Jinheung$quot;, were stored at 5℃ and 30℃ for six months and the changes in organoleptic quality and lipid components were investigated to obtain the following results.
In storage, both varieties brought about increases of hardness, cohesiveness and gumminess, and a decrease of adhesiveness among textural parameters of cooked rice. Storage at 5℃ showed no change in organoleptic quality but storage at 30℃ caused the
occurrence of off-flavor in both varieties and a marked decrease of stickiness in Jinheung.
Rice samples before storage contained 5-times more free lipids than bound lipids and free lipid content of Tongil was 70∼80% of Jinheung. In storage, bound lipids tended to increase slowly while free lipids increased in both varieties at 5℃ and tended to increase in Tongil and to decrease in Jinheung at 30℃.
In free lipid fractions of rice samples before storage were found 9 components including triglycerides, free fatty acids and sterol esters and in bound lipid fractions were found 8 components including free fatty acids and sterol esters, as the major components. In storage, changes in lipid components were more remarkable in free lipids than in bound lipids and in Jinheung than in Tongil. It was, therefore, concluded that Tongil variety had a better storage stability than Jinheung variety and the deterioration of rice quality occurred mainly in free lipid fractions during storage.
|