Aroma Quality of Gravenstein Apples Influenced by Regular and Controlled Atmosphere Storage

Sammendrag

Gravenstein apples were stored at 2 °C in regular atmosphere (RA) for 2½ months and in controlled atmosphere (CA) for 3½ months. Firmness, soluble solids (SS), titratable acids (TA), sensory quality and volatile compounds were measured of newly harvested and stored apples. Apples stored in RA for 2½ months or in CA for 3½ months, which are both commercial relevant storage conditions, have almost equal quality. Firmness, SS and TA decreased during storage, but only the SS/TA ratio was affected by storage treatment, CA apples having lower ratio than RA apples. Sensory description of stored apples was similar, characterised by apple, acidic and fresh odour. Apples at harvest were described as more grassy. The most abundant volatile compounds in Gravenstein were 1-butanol, 2-methyl-1-butanol, 1-hexanol, ethyl butanoate, butyl butanoate, hexyl butanoate, hexyl hexanoate and a-farnesene. The compounds having the highest aroma values (concentration/odour threshold) were ethyl butanoate, ethyl 2-methylbutanoate and ethyl hexanoate. Ethyl butanoate could be an appropriate ripeness indicator compound in Gravenstein due to its increasing concentration during storage and its high aroma value. Amount of volatile compounds, especially compounds contributing to overall aroma increased during storage. Total aroma value increased 16 times in RA apples and 12 times in CA apples compared to apples at harvest.