Ripening of apples during storage: III.—Changes in chemical composition of Golden Delicious apples during the climacteric and under conditions simulating commercial storage practice

Abstract

Knee: Rbening of Appfes during Storage. III 371 necessary to study metabolic processes in supranormal C02 concentrations.There is no reason to suppose from other work with plant tissues that a concentration of 5 % CO2 would have an inhibitory effect on decarboxylative or other enzymes in the glycolytic pathway and the tricarboxylic acid cycle.8-10 However, the reactions catalysed by malic enzyme are readily reversible and C02 fixation occurs in McIntosh apples stored in gas mixtures containing carbon dioxide.11 There is no evidence of acid accumulation in apples stored under such conditions, though it is possible that acid could be dissimilated in other pathways.In support of previous finding@ no marked change in whole fruit or peel respiration followed the onset of ethylene production in fruits stored at 3 . 5 "~. This event in itself implies a change in the metabolic state of the fruit, in that a new synthetic pathway becomes operative. The onset of ethylene production was little delayed by a decrease of temperature from 12"c to 3 . 5 "~ but much delayed in 2% 0 2 and more so in 5 % COz/3 % 0 2 .Discussion of the relationship between respiratory meta-bolism, and ethylene production and chemical changes in the fruit will be made in a later paper of this series's Golden Delicious apples were harvestedpre-climacteric and samples of fruit were stored in air at 12"c, air at 3.5'c, 5 % COa/3% 0 2 at 3.5"~ and2% Ozat 3 . 5 "~. Chlorophyllanrlcarotenoidin the fruitpeel, alcohol-soluble carbohydrate, titratable acidity and polysaccharide components of the alcohol-insoluble residue of the fruit cortex were estimated after periods of storage.In fruit stored in air at 12°C chlorophyll decreased and carotenoid increased rapidly, neutral pectic polysaccharides decreased and soluble polyuronide increased in the early stages of storage. At 3.5"~ the pigment changes were retarded and further so in the modified atmosphere; loss of neutralpolysaccharides occurred rapidly at first under all conditions but was arrested in 5% C 0~/ 3 % 02; increase of soluble polyuronide occurred with little delay at 3 . 5 "~ in air, after 113 days in 2% 0 2 and was not observed in 5 % COz13 % 0 2 . Loss of sugar and acid were retarded at the lower temperature and further retarded by modified atmospheres.The implications of these results for commercial storage are discussed and an attempt is made to relate them in the developmentalphysiolog) of appk fruits.

Freezing Fruits

“…'Gravenstein' apples can be held under refrigeration in good condition in air only about 2-3 months, but in CA storage they can be held about 6 months. Knee (1971) reported on CA storage of 'Golden Delicious' apples at 3SC (38.3°F) under 5% CO 2 plus 3% O 2 , Loss of sugar and acid was retarded by CA storage.…”