Changes in the Composition and Amounts of Volatile Compounds of Apple Juice Associated with Thermal Processing

Abstract

Studies were undertaken to analyse the changes in the composition and concentration of volatile compounds after thermal processing of apple juice and to evaluate the suitability for processing of five main cultivars in Japan. Juice yield of the cultivars examined ranged from 65.7% in 'Kogyoku' to 77.2% in 'Hatsuaki' throughout the processing. Seventy to 80 kinds of volatile compounds were detected in chromatographic peaks of which 39 compounds were identified by gas chromatographmass spectrometry. The compounds of each class included 27 kinds of esters, 6 of alcohols, 2 of aldehydes, 2 of hydrocarbons, a phenol and an acid. Average percentage of retention of each class of volatile compounds of the five cultivars was highest, 71.9%, for the alcohols, followed by 50.7% for the esters and 30.5% for the aldehydes. Total amounts of volatile compounds recovered after thermal processing were highest in the cultivar 'Kogyoku' amounting to 7.58ppm followed by 'Hatsuaki' with 5.83ppm, 'Mutsu' 3.20ppm, 'Golden·Delicious' 1.44ppm and lastly 'Fuji' with 1.41 ppm. From these results, it was apparent that the higher concentration of volatile compounds in the juice of cultivar 'Kogyoku' and related cultivar 'Hatsuaki' after thermal processing, accounted the higher suitability of juice making of these cultivars.