Influence of high temperature stress on postharvest quality of processing and non-processing tomato cultivars

Tomato fruits from a processing cultivar, 'Dorado' and a non-processing cultivar, 'Star Pak', were subjected to three prestorage heat treatments over a 5-h period under unshaded (34 +/- 2C), shaded (29 +/- 2C) and pre-cooled (20 +/- 2C) conditions followed by storage for 18 and 36 days at 20C. Terminal symptoms of heat injury and disease infection were evaluated in relation to changes in physical, physiological and chemical characteristics of the fruits during storage. Unshaded fruits demonstrated effects of heat injury resulting in reduced bioelectrical resistance, increased electrolyte leakage, increased total acidity and decreased total soluble solids during storage at 20C. Pre-cooling and shading proved to be effective methods to remove or prevent accumulation of field-heat and minimize heat injury. Pre-cooling was most effective, accounting for 28% and 14% less infected fruits for 'Dorado' and 'Star Pak', respectively, compared with unshaded fruits, after 36 days storage at 20C.