Volatiles of “Red Delicious” Apples Under Different Storage Conditions

Apples generate many volatile compounds responsible of apple flavor. The production of volatiles can be altered by several factors such as storage conditions: time, temperature, oxygen availability and carbon dioxide concentration. A small percentage of apples are commercialized immediately after harvesting, while a large percentage is stored, where characteristic flavor volatile compounds can be affected. The objective of this work was to measure volatile compounds in Red Delicious apples produced in Chihuahua, Mexico, during storage at 1°C under controlled atmosphere (3% CO₂ and 2% O₂) (CA), conventional refrigeration (CR), and CA plus seven days of stabilization under CR conditions (CA+CR). Apples were harvested at day 177 after full bloom (0.3ppm IEC) and stored in chambers under CR, CA or CA+CR for seven months. Volatile content of fruits was monthly analyzed by SPME-CG-MS. Results indicate that CR apples presented a higher production of flavor volatile compounds in comparison with CA and CA+CR. Ester production raised at first month of storage from 0.29ppm, at harvesting, to 69.87, 55.37, and 19.49ppm for CR, CA and CA+CR, respectively. Although the total ester concentration is very similar for both CR and CA apples, the ester composition differed. CR apples produced butyl acetate and 2-methyl butyl acetate in a proportion of 95% of total esters; while CA apples produced ethyl acetate, ethyl butanoate and ethyl-2-methyl butanoate, representing 88.3% of total esters. CA+CR showed 3 main compounds 2-methyl-butyl acetate, butyl acetate and n-propyl acetate representing 97% of total esters. In the post AC  period, there was a significant decrease in concentrations of ethyl acetate from 22.3ppm in CA to 0.01 in CA+CR, ethyl butanoate  from 16.8 to 0.05ppm, and ethyl-2-methyl butanoate from 9.8 to 0.04ppm. The highest concentration of alcohols was reached at the first month of storage, and was kept that level in CR conditions, while CA and CA+CR caused a decrease after the first month of storage. The main alcohols produced during apple storage were 1-butanol 2-methyl, 1-hexanol, and 2-methyl-1-propanol, in all storage conditions. Aldehydes showed a decrease of 40.73%, 53.41% and 84.92% during the first month of storage for CR, CA, and CA+CR, respectively. Under CA+CR aldehydes significantly increased after the first month of storage reaching 48.86ppm.  The main aldehydes produced during storage were 2-hexenal, cis-3-hexenal and hexanal. The use of CA storage produced a negative effect on the volatile compounds in comparison with CR and CA+CR failed to reach CR concentrations.