Evaluation of hot water and hot air heat shock treatments on South African avocados to minimise the occurrence of chilling injury

[摘要] ENGLISH ABSTRACT: The South African avocado fruit industry is export driven and the successfulstorage of fruits for extended periods is, therefore, essential. It was recordedthat 7.7 million cartons were exported during the 1995 season. The shippingof the avocados takes approximately 15 days and the fruits are being storedat low temperatures to minimise the possibility of fruits softening.Unfortunately low temperature storage results in chilling injury. A possiblemethod to increase avocado resistance to chilling injury is to administer a heatshock treatment. In this way the fruits are protected from chilling injury byinducing the formation of so-called heat-shock proteins which render the cellmembranes more resistant to chilling injury.The objective of this study was to evaluate different heat shocktreatment protocols as a method of preventing or minimising chilling injury andto extend the shelf-life of avocado fruits while exporting at the lowest possibletemperature. Examining the effect of different temperatures and exposuretimes on the quality of the different avocado cultivars pursued this. Theexterior chilling injury on each fruit was quantified and the firmness andinternal quality parameters evaluated.A total of 32 Experimental Studies were conducted. The resultsshowed that the Hot Water Heat shock Treatment (HWHST) workedeffectively for the South African 'Fuerte' cultivar between 40° and 42°C forexposure times of between 20 and 30 min. The 'Edranol' cultivar also showedpromising results between 40° and 42°C for exposure time of between 8 and22 min. The HWHST was not effective on the South African 'Hass' cultivar.The 'Ryan' cultivar with its thick skin made this cultivar less susceptible tochilling injury and therefore HWHST would be unnecessary. The 'Pinkerton'cultivar had a lot of factors that influenced the results. Therefore, moreresearch needed to be done on the 'Pinkerton' cultivar, before anyconclusions could be obtained from this cultivar, although it showed potential.Hot air treatment worked fairly well, but unfortunately the long exposure timeneeded made this treatment unpractical. Throughout the whole study theimportance of maturity surfaced as a major role in all the aspects of postharvest quality.

[发布机构] Stellenbosch University