The juices were adjusted to pH 2.4~4.4 respectively and stored for 20 days at 40°C. The off-flavor developed more heavily in the juices of decreased pH. Therefore, the differences in the quantities of volatile components among the juices of various pH were investigated. The recoveries of terpene hydrocarbons, predominantly d-limonene, were at the maximum level in the juice of pH 3. 2~3. 4, but the recoveries decreased to 60% or less in the juice of lower than pH 2. 9 or higher than pH 3. 8. In fresh aroma components, linalool and citronellal were well preserved in the juice of increased pH. In off-flavor components, the formations of fenchyl alcohol, β-terpineol and α-terpineol were strongly influenced by pH of the juice and the amounts of these terpene alcohols formed during storage were increased linearly with decrease of pH. Judging from this fact, the reactions of formations of off-flavored terpene alcohols were acid-catalyzed hydration of terpene hydrocarbons. As an exception, effect of pH could not be observed with respect to formation of terpinen-4-ol. These results lead to the conclusion that the quality of flavor is well preserved in the juice of higher pH.
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