Calcium dips enhance volatile emission of cold-stored 'Fuji Kiku-8' apples

Despite the relevance of volatile production for overall quality of apple (Malus x domestica Borkh.) fruit, only a few studies have focused on the effects of calcium treatments on this quality attribute. In this work, 'Fuji Kiku-8' apples were harvested at commercial maturity, dipped in calcium chloride (2%, w/v), stored at 1 degrees C and 92% relative humidity for 4 or 7 months under either air or ultralow oxygen (ULO; 1 kPa of O(2)/2 kPa of CO(2)), and placed subsequently at 20 degrees C. Ethylene production, standard quality parameters, emission of volatile compounds, and the activities of some related enzymes were assessed 7 days thereafter. Calcium concentration was higher in CaCl(2)-treated than in untreated fruit, suggesting that the treatment was effective in introducing calcium into the tissues. Higher calcium contents were concomitant with higher flesh firmness and titratable acidity after storage. Furthermore, calcium treatment led to increased production of volatiles in middle-term stored apples, probably arising from enhanced supply of precursors for ester production as a consequence of increased pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities. After long-term storage, higher volatile emission might have arisen also from the enhancement of alcohol o-acyltransferase (AAT) activity, which was increased as a result of calcium treatment. In addition to storage period, the effects of calcium treatment were also partially dependent on storage atmosphere and more noticeable for fruit stored in air.