Mealiness of ‘Forelle’ Pears - Quo Vadis?

Abstract

Abstract'Forelle' (Pyrus communis), a late season blushed pear cultivar grown in South Africa, requires a minimum of 12-weeks cold storage (-0.5 °C) to ripen evenly. Mealiness, a dry texture disorder, may develop at this time. In contrast to other pear cultivars, longer cold storage periods result in less mealiness. This could be related to insufficient total ACC build up and ethylene production, during the first 12 weeks of cold storage, for juicy texture development, during ripening. 'Forelle' pears were stored for 3 weeks at -0.5°C, treated with ethylene (100 µL L -1 , 24h, 20°C), stored at 20°C for 2 days and thereafter 3 weeks at -0.5°C. Ethylene treatment led to an increase in mealiness after this period. However there were no differences in treated and control fruit following further ripening at 15°C for 7 days. Mealiness could not be linked to insufficient ethylene during shorter storage periods. Harvest maturity, a factor known to influence mealiness, was tested by harvesting fruit 2 weeks prior to commercial harvest, during commercial harvest, and 2 and 4 weeks after commercial harvest. Mealiness occurred at all harvest dates after 6 weeks at -0.5°C and 7 days at 15°C. Storage temperature was also tested as another factor influencing mealiness. Fruit were stored at -0.5°C, 4°C and 7.5°C for 6 weeks and ripened for 7 days at 15°C. Fruit stored at 4°C and 7.5°C ripened with 0 and 8% mealiness, respectively, in contrast to 70% in control fruit. Results could, however, not be confirmed in 2002 and 2003 as all treatments exhibited low mealiness levels (<4%). As high temperatures prior to harvest may influence mealiness, overhead evaporative cooling was applied during 2003 from early fruit development or from 2 weeks prior to harvest. Little to no mealiness developed in all treatments making it difficult to conclude if cooling prior to harvest affects mealiness.