Controlled Atmosphere Storage of Highbush Blueberries cv. ‘Duke’

Abstract

The highbush blueberry cultivar ‘Duke’ was subjected to controlled atmosphere storage up to seven weeks under following CO2 + O2 conditions (kPa CO2 + kPa O2): 0.03+21 (=air, control); 6+18; 12+18; 18+18; 24+18; 12+2 and 18+2 at 0–1 °C storage temperature. The changes of ripening and quality parameters of the berries were monitored in 2–3 weeks intervals. In contrast to the experience with other fruits, blueberry fruits reacted to increasing CO2 partial pressure (>12 kPa) with loss of firmness, regardless of the height of O2 pressure. Only berries stored in 6–12 kPa CO2 maintained their firmness on acceptable values. The titratable acidity concentration of the fruits from the different storage treatments reacted in a similar way: Increasing CO2 partial pressure from 12 to 24 kPa resulted in an increasing loss of acidity. However, total soluble solids (TSS) of fruits did not differ significantly between all treatments in most sampling dates. Moreover, the respiration rate of fruits stored under increasing CO2 levels was significantly higher than that of air-stored fruits. Respiration quotient (RQ) values by these fruits reflected an enhanced consumption of organic acids as respiration substrate. Incidence of fungal diseases, mainly Botrytis cinerea, could be efficiently controlled by higher CO2 levels. In this respect, 6 kPa CO2 proved to be not high enough to retard the fungal growth. Weight loss of berries was minimized by all storage conditions. The overall judgment of the effect of storage conditions on fruit quality through the consumer sensory test revealed that blueberry fruits could be kept under air conditions at 0–1 °C up to three weeks in acceptable condition. However, for a longer storage period up to six weeks, it is highly recommended to store highbush blueberries cv. ‘Duke’ under high CO2 levels up to 12 kPa without O2 reduction. Higher CO2 level more than 12 kPa can not be recommended due to negative impact on flavour, firmness, and acidity content