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Abstract
Broccoli (Brassica oleracea L., Italica Group) was held at 5°C in a stream of humidified air (control) or of humidified 14% O2/10% CO2 (CA), or it was wrapped with a nonperforated flexible polyvinylchloride (PVC) film and held in a humidified (90% to 95% RH) or nonhumidified (40% to 45% RH) stream of air for 3 weeks. Water loss was reduced 17% by the CA treatment and 50% by wrapping the broccoli. Broccoli stored in CA or wrapped in film retained quality significantly better than the controls. Atmosphere composition within packages reached equilibrium within the first 24 hr and did not change significantly over the 3 weeks. Self-generated atmosphere modification was greater within packages held in humidified air than within those held in nonhumidified air (7.8% vs. 13.2% O2; 9.0% vs. 6.7% CO2, respectively). The steady state of atmospheres within packages allowed the calculation of respiration rates of wrapped broccoli by monitoring changes in the air surrounding the package. Oxygen consumption and CO2 production by samples held in CA or in films were reduced 30% to 40% relative to the controls. The respiratory quotient for the CA and humidified wrapped samples was about 1.30, but 1.15 in the control and nonhumidified wrapped samples.
`Gala' apples [Malus silvestris (L.) var. domestica (Borkh.) Mansf.] were treated with ethanol vapor (5 mL·kg-1 fruit for 24 hours at 25 °C), heat (4 days at 38 °C and >98% RH), or 1-methylcyclopropene (1-MCP; 1 or 0.625 μL·L-1 for 18 hours at 20 °C) before processing into slices, then dipped in anti-browning solutions or coatings, drained, and packaged in perforated polyethylene bags. Residual effects of pretreatments on fresh-cut slice physiological and quality attributes were investigated during storage for up to 19 days at 5.5 °C. Ethylene production was reduced by ethanol, heat, and 1-MCP pretreatments, while ethanol and heat also reduced slice respiration. Heat and 1-MCP pretreatments inhibited slice texture changes, while ethanol had no effect on instrumental texture measurements but reduced sensory firmness. Ethanol pretreatment increased the contents of ethanol and ethyl esters in slices but reduced acidity, while heat reduced both acidity and aroma volatile levels. Both ethanol and heat pretreatments led to lower sensory scores for apple flavor and ethanol-pretreated slices also received higher scores for altered flavor, although all scores were in the acceptable range. Slice acidity was best maintained by 1-MCP pretreatment. Shelf life based on appearance was 15 to 16 days for ethanol-pretreated slices and 12 days for heat-pretreated slices compared to that of control, which was 8 to 9 days, while 1-MCP pretreatment promoted decay development on the cut surface, which reduced the shelf life to 7 to 8 days. Obvious separations were determined between ethanol- and heat-pretreated slices and untreated control by canonical discriminant analysis of headspace volatile levels determined by GC and electronic nose. Therefore, pretreatments with ethanol and heat are very effective for prolonging visual shelf life at the expense of aroma quality.