The Effect of Freezing Modes and Frozen Storage on Aroma, Enzyme and Micro-organism in Hami Melon

Abstract

The effects of freezing modes and time in frozen storage on aroma, enzymes and micro-organisms in Hami melon, also called cantaloupe melon (Cucumis melo. var. reticulatus Hami melon), were determined. Freezing process and frozen storage could not significantly reduce either micro-organisms counts or the enzymatic activities of polyphenoloxidase (PPO), peroxidase (POD) and lipoxidase (LOX) in melon. Liquid nitrogen ultra-rapid freezing maintained most aromatic components of the melon as compared with slow freezing. The mechanism of aromatic change in frozen melon was mainly ascribed to esters changing continuously in variety and concentration because of enzymolysis or synthetic reactions of esters catalysed by LOX. Meanwhile, increasing concentration of linoleic acid and linolenic acid in frozen melon cells promoted the biochemical reaction of unsaturated fatty acids in LOX system, so that enzymolysis of the double bonds in the ninth and tenth carbon of linoleic acid and linolenic acid was accelerated. Consequently, with the prolongation of time in frozen storage more and more unsaturated alcohols and aldehydes with 6 and 9 carbons were produced, the green notes of frozen storage melon became more and more intense, and the ester fragrance became more and more feeble. The above findings can benefit the development of cantaloupe melon process industry.