Postharvest quality and bioactive properties of tomatoes (Solanum lycopersicum) stored in a low-cost and energy-free evaporative cooling system

Abstract

The aim of this study was to investigate the effect of low cost evaporative cooling system on the quality of two tomato cultivars, namely, 9065 jam and round tomatoes. Both the tomato cultivars were harvested from a smallholder farmer's field at Umsinga and stored for 20 days in one of the three storage conditions namely; cold room (CR), room temperature (RT) and evaporative cooling system (ECS) and sampling done every 5 days. The tomato samples were laid out as a factorial design with four replications. Results obtained proved that the storage conditions and storage period had a significant effect (p < 0.05) on the lycopene content (LC), antioxidants, total phenolic content (TPC) and ascorbic acid (AA) of the tomato samples. A decreasing trend with storage time was observed for antioxidants and TPC for both the cultivars whilst there was an increasing trend of AA and lycopene content on both the cultivars stored in the different storage conditions. Ascorbic acid was highest in samples stored in RT (0.173 mg/100g for round tomatoes; 0.172 mg/100g for 9065 jam tomatoes), second highest in samples stored under ECS (0.16 mg/100g for round; 0.17 mg/100g for 9065 jam) and lowest in samples inside the CR (0.11 mg/100g; 0.12 mg/100g for 9065 jam). Lycopene content was highest in samples stored in RT (45.31 mg/100g for round tomatoes; 52.9 mg/100g for 9065 jam tomatoes) second highest in samples stored under ECS (32.46 mg/100g for round tomatoes; 42.98 mg/100g for 9065 jam tomatoes) and lowest in samples inside the CR (14.16 mg/100g for round tomatoes; 8.79 mg/100g for 9065 jam tomatoes). Total phenolic content was highest in samples stored in CR (0.17 mg/100g GAE for round tomatoes; 0.19 mg/100g GAE for 9065 jam tomatoes) second highest in samples stored under ECS (0.124 mg/100g GAE for round tomatoes; 0.126 mg/100g GAE for 9065 jam tomatoes) and lowest in samples inside the RT (0.11 mg/100g GAE for round tomatoes; 0.12 mg/100g GAE for 9065 jam tomatoes). Antioxidant activities were highest in samples stored in CR (2.05 mg/100g for round tomatoes; 2.03 mg/100g for 9065 jam tomatoes), followed by samples stored under ECS (1.82 mg/100g for round tomatoes; 1.96 mg/100g for 9065 jam tomatoes) and lowest in samples inside the RT (1.02 mg/100g for round tomatoes; 1.07 mg/100 g for 9065 jam tomatoes). The correlation relationship among cultivars was positive and PCA proved that the cultivars were similar. Although CR provided the best storage condition for the investigated parameters, the results provided sufficient evidence that ECS can be the best method to increase shelf life in rural communities due to its association with cost reduction.