Heat Treatment Temporarily Inhibits Aroma Volatile Compound Emission from Golden Delicious Apples

Volatile compounds were collected by porous polymer trapping from Golden Delicious apples (Malus domestica Borkh.) that had been heat-treated for 4 days at 38 °C, a treatment developed to reduce physiological and pathological disorders during storage, and then stored at 1 °C. Heat treatment of apple fruits markedly inhibited emission of total volatile esters (compounds commonly associated with apple aroma) and total volatiles (comprised principally of the volatile esters and α-farnesene) of apple within 1 day of treatment. However, after an extended refrigerated storage at 1 °C, the heat-treated fruit recovered and produced more total volatiles, increasing from 4% compared to non-heat-treated fruit directly after heat treatment to 145% of non-heat-treated fruit after 6 weeks of storage. Total volatile production of non-heat-treated fruit declined over 5-fold during the 6 weeks of cold storage, while that of heat-treated fruit increased over 6-fold. Total volatile esters from heat-treated fruit declined after 1 week of storage but had increased 4-fold from the initial sampling date after 6 weeks of storage. The heat treatment effect on emission of volatile compounds was observed immediately following heat treatment. The fruit cuticle and epidermis were not barriers to volatile emission by heat-treated fruit since slicing both heat-treated and non-heat-treated fruit after treatment resulted in total volatile yields similar to intact fruit. Heat treatment apparently temporarily inhibited but did not destroy, or destroyed but allowed resynthesis of, the enzyme systems catalyzing volatile compound synthesis as shown by increasing emission over time by heat-treated apples.