Abstract
In order to evaluate the effect of changing temperature on maturation control of kiwifruit (var. Hayward) stored in modified atmosphere packages, storage tests were carried out. Two kiwifruits and a 10g sachet of ethylene absorbent (KMnO4) were packed in 0.03mm thick low-density polyethylene bags and initially stored at 1°C for 3 weeks. The fruits were then removed and stored at different temperatures until the 8th week. The conditions of storage were: (a) weekly temperature changing between 1°C and 10°C; (b) weekly temperature changing between 1°C and 15°C; (c) weekly stepwise temperature increase of 1°C; (d) constant temperature of 5°C; (e) constant temperature of 10°C; (f) constant temperature of 15°C; and (g) constant temperature of 1°C, which is ordinary storage condition for comparison with changing temperatures. Due to variations in quality indexes of test samples, such as total soluble solids (TSS), titratable acidity (TA), firmness, weight loss, etc., at each sampling time after the 3rd week, the range of quality values at the end of storage were compared with the values of ripened kiwifruit on retail.
As a comparison of inner quality indexes of test samples and fruits ripened for retail, the respective values at storage temperatures of 1°C and 10°C, respectively, at 8 weeks ranged from 12.0% Brix and 14.2% Brix. These values were lower than 15.7% Brix for fruit on retail. On the other hand, the TA values of fruits stored at changing temperatures between 1°C and 15°C and between 1°C and 10°C at 6 and 8 weeks, respectively, were 0.9 and 1.0 citric acid g/100ml. Compared with TA value of 0.71 citric acid g/100ml for ripened fruit on retail, test sample were higher in TA content. The results show that fruits stored at changing temperatures ripened less than fruits on retail.
Moreover, the respective firmness values of fruits at storage temperatures of weekly increase of 1°C and constant temperature of 5°C were 10.8 and 16.8N/mm, respectively. These values were higher than firmness value of 4.8N/mm for kiwifruit on retail. This confirmed that test samples were firmer after storage due to scrubbing of ethylene gas in the polyethylene bags.
Weight losses at storage temperatures of 1°C and changing temperature between 1°C and 10°C at 8 weeks ranged from 0.5% to 2.0%. These values were lower than the upper limit of about 5% in fruits usually acceptable to consumers.
