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  • Author or Editor: Kate M. Maguire x
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The maintenance of optimal storage conditions for fresh produce is rarely achieved in commercial cool chains. The impact of deviations for short time periods from these optimal storage conditions on fruit quality has not been thoroughly investigated. In this study, ‘Cripps Pink’ apples (Malus domestica) stored at 0 °C in air were exposed to periods at 20 °C (for 1, 3, and 6 days) to simulate breaks in the cool chain. The influence of harvest maturity, storage time before exposure, length of exposure, and multiple exposures to 20 °C on fruit physiology during and after the exposures was monitored through 27 laboratory-based scenario simulations. Preclimacteric apples exposed to 20 °C hastened climacteric development, whereas postclimacteric apples were induced to produce ethylene at ≈1.5 times the normal on return to cool storage at 0 °C irrespective of the fruit harvest maturity or timing, length, and number of exposures to 20 °C. The observed increase in ethylene production did not increase rates of reduction of either fruit stiffness (a measure of flesh texture) or background color measurement (hue angle). This research suggests that fluctuations in temperature have a greater effect in terms of changes in quality for preclimacteric apples than postclimacteric fruit. The reasons why changes in fruit stiffness and background hue angle in postclimacteric fruit did not respond to increases in ethylene production require further investigation.

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Research quantified contributions to total variation in water vapor permeance from sources such as cultivar and harvest date in `Braeburn', `Pacific Rose', `Granny Smith', and `Cripps Pink' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. In a study on `Braeburn' fruit from eight orchards in Central Otago, New Zealand, >50% of the total variation in permeance was associated with harvest date. This variation was the result of a large increase in water vapor permeance from 16.6 to 30.2 (se = 0.88, df = 192) nmol·s-1·m-2·Pa-1 over the 8 week experimental harvest period. Fruit to fruit differences accounted for 22% of total variation in permeance. Interaction between harvest date and orchard effects explained 7% of the total variation, indicating that fruit from the different orchards responded in differing ways to advancing harvest date. Tree effects accounted for only 1% of the total variation. Weight loss from respiration [at 20 °C and ≈60% relative humidity (RH)] comprised 3.04±0.11% of total weight loss, averaged across all harvest dates. In a second study of fruit of four apple cultivars, almost 30% of the total variation in water vapor permeance was associated with cultivar differences. Mean water vapor permeance for `Braeburn', `Pacific Rose', `Granny Smith', and `Cripps Pink' fruit was 44, 35, 17, and 20 (se = 4.3, df = 300) nmol·s-1·m-2·Pa-1 respectively. Over 20% of the total variation was associated with harvest date and arose from a large increase in water vapor permeance from 21 nmol·s-1·m-2·Pa-1 at first harvest to 46 nmol·s-1·m-2·Pa-1 (se = 5.3, df = 200) at final harvest, 10 weeks later, on average across all four cultivars. There was large fruit to fruit variation in water vapor permeance accounting for 25% of the total variation in permeance values. Tree effects only accounted for 4% of the total variation. Water vapor permeance in `Pacific Rose'` and `Braeburn' increased substantially with later harvest but values remained relatively constant for `Granny Smith' and `Cripps Pink'. A simple mathematical model was developed to predict weight loss from `Braeburn' fruit. Based on these findings, it appears worthwhile to increase the stringency of measures to control weight loss in `Braeburn' and `Pacific Rose'` apples, particularly those harvested late in the season.

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