Comparison of biochemical and physiological properties of nigerian tomato fruits ripened under different conditions

Abstract

The growth in chronic diseases such as obesity, diabetes, various types of cancers and cardiovascular diseases is an argument in favour of promoting fruit and vegetable consumption in Africa, with the main obstacle being the purchasing power. The objective of this study was to investigate the respective impacts of ripening stages and techniques of ripening on tomato fruit quality in order to recommend which of the conditions of ripening is better for optimum benefit of the tomatoes. The physiological and biochemical changes in tomato fruits of two varieties (Ibadan-Local and Roma cultivars) ripened using two different techniques (field and ambient temperature ripening) were monitored; the differences in the mean values between the ripening methods are discussed at appropriate significance levels. The mean differences in percent total solids for tomato fruits between the two conditions of ripening are significant (P<0.05 at the breaker stage of Ibadan-local cultivar and P<0.01 for other stages in the two varieties). The differences are much higher at the pink to fully-red stages in tomatoes ripened under the ambient temperature. Except at light-red stage of Ibadan-local cultivar and breaker stage of Roma cultivar, the mean differences in pH values between the ripening methods are significant (P<0.05 at the breaker stage of Ibadan-local cultivar and at the light-red stage of Roma cultivar and P<0.01 for other stages in the two varieties). Mean differences in percent titratable acidity (as citric acid) of the fruits under the two methods of ripening are also significant (P<0.05 at the breaker stage of Roma cultivar and P<0.01 for other stages in the two varieties) with exceptions at fully-red stage of the two varieties. However, high significant differences (P<0.01) exist between the mean values of reducing sugar, lycopene (but P<0.05 at breaker stage of Roma cultivars) and beta-carotene contents of the tomato fruits under the two conditions of ripening, with higher values obtained mostly in the field ripening method. About 69.2 g and 58.3 g of tomato fruits, ripened on the parent plants (field ripening), at light-red stage of Ibadan-local and Roma-type respectively, are recommended daily in accordance with average daily recommendation of 25.2 mg of lycopene per day in Canadian diet and from the study from Harvard School of Medicine. Equivalent quantities could only be reached by consuming higher quantities of tomatoes ripened at ambient temperature. 

Key words: Ripening, tomato, cancer, beta-carotene, lycopene