Overview

Studies conducted in 2000 and 2001 by members of the Department of Food Science and Technology, Makerere University, and IPM CRSP, revealed that retailers at the fresh market level prefer visible signs of Dithane M-45 (DM45) on tomato fruits because they believe treated fruits have a longer shelf life. Thus, some farmers spray tomato fruits with DM45 immediately after harvest. The main objective of the present study therefore, was to determine the effect of different levels of DM45 on the postharvest storage quality of tomato fruits in order to verify the tomato retailers’ assertion and also to establish the DM45 residue levels on tomato fruits obtained from markets. Tomato fruits from farmers in Busukuma Sub-county were subjected to three treatments of DM45: control (no DM45), recommended levels (2.5 g/l) and excess levels (16.7 g/l) and were analysed for microbial growth, % spoilage, firmness, acidity, pH and total soluble solids at 4-day intervals, and for DM45 residues. Tomato fruits were also purchased from three markets in Kampala and their DM45 levels determined. Results indicate that generally, in all quality parameters analysed, there was no significant difference (p = 0.05) between fruit treated with recommended and excess DM45 levels. However, significant differences were observed between the control and treated fruit with the latter showing better fruit quality parameters throughout the storage period. The majority of untreated fruit (62%) were unsalable by day 16 of storage. Rhizopus rot, sour rot, gray mold rot and Mucor rot were the major spoilage diseases identified. DM45 residue levels increased with increasing treatment levels. However, both the control and treated fruit had more than twice the recommended DM45 residue levels. Fruit from all markets had DM45 residue levels higher than recommended, implying that tomato consumers are at high health hazard risk. It is concluded that although treating tomato fruit with DM45 improved some of their quality characteristics, fruit spoilage and microbial growth increased with storage time. There is therefore need to develop systems for reducing DM45 residues on tomatoes through developing safer methods of preserving fresh tomatoes.