Postharvest Quality of `Thompson Seedless' Grapes after Insecticidal Controlled-atmosphere Treatments

Abstract

Non-SO2-fumigated `Thompson Seedless' table grapes (Vitis vinifera L.) were stored at 5 or 20 °C for 6 and 4.5 days, respectively, in air or one of four insecticidal controlled atmospheres (ICA); 0.5% O2 + 35% CO2; 0.5% O2 + 45% CO2; 0.5% O2 + 55% CO2; or 100% CO2. The fruit were evaluated for weight loss, berry firmness, soluble solids concentration (SSC), titratable acidity, berry shattering, rachis browning, berry browning, and volatiles (acetaldehyde and ethanol). Fruit quality was not affected at 5 °C with the exception of greater rachis browning in fruit treated with 0.5% O2 + 45% CO2. At 20 °C, ICA treatments maintained greener rachis compared to the air control; however, SSC was reduced in the fruit treated with 55% and 100% CO2. At both temperatures, ICA induced the production of high levels of acetaldehyde and ethanol. Ethanol concentrations were two-thirds lower at 5 °C than at 20 °C. Consumer preference was negatively affected by some ICA treatments for grapes kept at 20 °C, but not by any of the treatments at 5 °C. Preliminary data for mortality of omnivorous leafroller pupae (Platynota stultana Walshingham), western flower thrips (Frankliniella occidentalis Pergande) adults and larvae, and pacific spider mite (Tetranychus pacificus McGregor) adults and larvae indicate that many of the ICA treatments would provide significant insect control.