Nutritional and postharvest quality attributes of commercial tomato varieties

Abstract

Tomato (Lycopersicon esculentum Mill) is the leading vegetable in terms of production in Kenya. The Kenyan local market has a wide variety of tomato cultivars with a wide range of morphological and sensorial characteristics but information on the nutritional and postharvest quality of these varieties is limited. The objective of this study was to investigate and identify tomato varieties of superior postharvest and nutritional quality. The study was conducted over two seasons in 2014. In the first season, thirteen tomato varieties were grown in a greenhouse. The tomatoes were harvested at three maturity stage (mature green, turning and red ripe) and stored at ambient room conditions (Temperature: 250C). For each variety and maturity stage, analysis of postharvest characteristics including cumulative weight loss, skin color changes, and ethylene production and respiration rates was done. The fruits were also analyzed for phytochemical and nutritional quality attribute including lycopene content, antioxidant capacity, total soluble solid content and total titratable acid. In the second season, eight varieties were grown for confirmatory studies on respiration and ethylene production rates. Significant differences (p< 0.05) was then determined for the data. The percentage weight loss of the tomato fruits relative to the initial was lowest in the Anna F1 (0.16%) at the mature green stage and highest in Nuru F1 (3.80%) at the turning stage. The respiration rate peaks in the first season ranged between 82.82-23.67 ml CO2Kg-1 h-1 compared to 43.34-9.82 ml CO2Kg-1 h-1 in the second season while the ethylene peaks in the first season ranged between 8.30-0.34 µl C2H4 kg-1h-1 compared to 5.51-0.97 µl C2H4 kg-1h-1 in the second season. The lycopene content was highest in Rambo (27.53 mg/100g) and the lowest in Cal J (0.41mg/100g). The lycopene content and antioxidant capacity were highest at the red ripe stage. Generally, the Anna F1 and Chonto F1 varieties displayed better postharvest quality that can prolong the shelf life of the fruits while for better phytochemical properties, harvesting at red ripe stage is recommended. In turn the turning stage of maturity proved to be a better stage to harvest tomatoes.