Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 28, 2002
Publication Date: November 19, 2002
Citation: BAI, J., HAGENMAIER, R.D., BALDWIN, E.A. VOLATILE RESPONSE OF FOUR APPLE VARIETIES OF DIFFERENT COATINGS DURING MARKETING AT 20°C. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2002. v. 50. p. 7660-7668. Interpretive Summary: Coatings are applied to apples to increase gloss and improve marketability, but these also have some affect on flavor because they block air from passing into the fruit. Five apple coatings with different resistance to gas exchange were used with `Delicious', `Fuji'. `Braeburn' and `Granny Smith' apples. These had a big affect on oxygen concentration inside the fruit, which in turn affected flavor. The carnauba and candelilla wax coatings gave intermediate values of oxygen and resulted in highest concentrations of two compounds (butyl acetate and 2-methylbutyl acetate) important to flavor. The shellac coatings resulted in such low internal oxygen for `Braeburn' and `Granny Smith' apples that a considerable amount of alcohol was generated in the fruit, and fermentative flavor was noted. We also found that the coatings affected flavor by trapping inside the apple the compounds that contribute to flavor.
Technical Abstract: Five experimental coatings with different resistance to gas exchange were used with freshly harvested and 20-week commercially stored apples of `Delicious', `Fuji', `Braeburn' and `Granny Smith' varieties. The coated or non-coated apples were held at 20 °C for up to 4 weeks. The gas partial pressures inside the fruits for the various coatings ranged from 1-25 kPa CO2 and 20-1 kPa O2. Volatile evaporation rates were measured as also were their compositions in the fruit. The coatings with intermediate gas resistance (carnauba-shellac mixture and candelilla) gave intermediate values of CO2 and O2 in the internal atmosphere of `Delicious', `Fuji', and `Braeburn' apple, and the highest concentrations of butyl acetate and 2-methylbutyl acetate, in the fruits. The coatings with highest gas resistance (shellac and shellac-protein) caused high internal CO2, and low O2, resulting in anaerobic fermentation in `Braeburn' and `Granny Smith' apples and relative high amounts of low molecular-weight ethyl esters trapped within the fruit. A small portion of the alcohols evaporated from fruits compared to esters, this attributed to their high Henry's law coefficients.