CHANGES OF COLOUR PARAMETERS AND ANTIOXIDANTS OF VINE RIPENED TOMATO (LYCOPERSICON ESCULENTUM MILL.) FRUITS AFFECTED BY NATURAL LIGHT

Changes in colour and antioxidant content on the on-vine ripening of tomato fruits (Lycopersicon esculentum Mill.) were studied under two solar exposures. A two year experiment was carried out to determine how the position of the fruit on trellised tomato plants influenced surface temperature, colour evolution and antioxidant content of fruits. The orientation of the rows resulted in non-shaded (NS) fruits that were exposed to full sunlight from 09.00 to 16.00 h, while shaded fruits (SF) were totally shaded during that period. There was a significant difference (p=0.05) between shaded (SF) and non-shaded (NS) fruit surface temperatures. The more direct sunshine the fruits received, the higher their surface temperatures increased. Only the average temperature of non-shaded fruits was significantly higher than the air temperature at 14.00 h. Changes in the colour of non-shaded fruits showed significantly higher CIELab Hue compared to shaded fruits at the end of the ripening process. A close negative correlation (R=-0.72) was found between the cumulative fruit surface-air temperature difference and the Hue colour parameters of NS fruits, but there was only a weaker (R=-0.53) correlation in the case of SF fruits. Solar exposure had a great influence on antioxidants. Higher surface temperature resulted in significantly more polyphenols and ascorbic acid and less lycopene content of tomato fruits.