The effect of heat treatment on bioactive compounds and color of selected pumpkin cultivars

Abstract

In this study, the effect of selected thermal operations applied during processing of pumpkins of the cultivar Butternut Rugosa of the species Cucurbita moschata as well as hybrid grey pumpkin Nelson F1 and Hokkaido ‘Uchiki Kuri’ of the species Cucurbita maxima on the presence of selected bioactive compounds (gallic acid, quercetin, cyanidin 3-glucoside, l-ascorbic acid) and color expressed in CIE L*a*b* chromatic and L*C*H* cylindrical color spaces was evaluated. The highest content of polyphenols (13.296 mg(GAE)/g f.w.), flavonoids (0.732 mg(KW)/g f.w.) and l-ascorbic acid (19.38 mg (L-AA)/100 g f.w.) was found in Hokkaido cv. Uchiki Kuri (Cucurbita maxima), while the lowest content of these compounds was found in Butternut Rugosa (Cucurbita moschata). The analysis of the results showed that immersion cooking was the least favorable thermal treatment because of the loss of bioactive compounds up to 80% and that steam cooking was more favorable. It was also shown that blanching before freezing of pumpkins is advantageous from the point of view of minimization of nutrient losses. Despite the fact that pumpkins underwent different types of thermal treatment, their color was still characterized by orange shade with higher or lower saturation depending on the variety.