Evaluation of the effects of supply chain routes and pre-storage treatments on the postharvest quality of stored 'Nemo-Netta' tomatoes.

Abstract

Tomato postharvest losses are the major constraints that limit optimum competitiveness and marketability of tomatoes. This becomes a serious threat since tomatoes are highly perishable, and lose quality at any stage of the supply chain. In this study, the effects of supply chain routes, pre-storage treatments and storage conditions on microbial quality were evaluated in ‘Nemo-Netta’ tomatoes harvested at pink maturity stage. The effects of supply chain routes, harvesting maturity stages, pre-storage treatments, pre-storage treatments, and storage conditions on physiological, biochemical and chemical quality of ‘Nemo-Netta’ tomatoes were also evaluated. The study also evaluated the combined effects of integrated postharvest technologies. The effect of disinfecting tomatoes with different solutions (anolyte water, chlorinated water and hot water) or coating tomatoes (with Gum Arabic), on the microbiological quality of tomatoes during storage after transportation in non-refrigerated trucks along three different supply chain routes was evaluated (Chapter 3). Upon the arrival of tomatoes in Pietermaritzburg market, they had condensed droplets on the fruit surfaced which was speculated to be due to the differences in temperatures and relative humidity within truck during transportation. Droplets on the fruit surface became a conducive environment for microorganisms to proliferate. Pink-matured tomatoes with freedom from blemishes were treated, stored on either ambient (16 °C in winter / 25 °C in summer) or cold (11 °C), and sampled on day 0, 16 and 30 for quality assessment. An experiment was laid out as a factorial split-plot design with supply routes as main plots, storage conditions as subplots and random allocation of treatments within each subplot. An experiment was conducted in two seasons during winter harvest and during summer harvest. The results revealed a highly significant difference (P < 0.001) in the microbiological population (log cfu cm-2) and marketability (%) of tomatoes from different supply routes, storage environments, and treated with different disinfectants. Anolyte water was the most effective treatment in maintaining quality of tomatoes. It reduced the initial microbial load significantly (P < 0.001) to 3.779 log cfu cm-2. This represented the second highest log reduction of 1.049 log cfu cm-2 when compared to untreated control which had 4.828 log cfu cm-2. Furthermore, three-way interaction of supply route, disinfectants, particularly anolyte water with low temperature storage remained the most superior treatment in the microbial quality of pink-matured tomatoes. It reduced the initial microbial load significantly (P < 0.001) to 2.835 log cfu cm-2. This represented the highest log reduction of 1.470 log cfu cm-2, when compared to untreated samples. Anolyte water also maintained the highest percentage of the general marketability of pink-matured tomatoes, however a three-way interaction of supply route, disinfectants, particularly anolyte water with low temperature storage remained the most superior treatment in maintaining marketability of pink-matured tomatoes across all the supply routes. The effect of disinfecting tomatoes with different solutions (anolyte water, and hot water) or coating tomatoes (with Gum Arabic), and their combinations on the physiological, chemical and biochemical quality of tomatoes during storage after transportation in non-refrigerated trucks along three different supply chain routes was evaluated in Chapter 4. Green, pink and red matured tomatoes with freedom from blemishes were treated, stored on either ambient (16/ 25 °C) or cold (11 °C), and sampled on day 0, 8, 16, 24 and 30 for quality assessment. An experiment was laid out as a factorial design, split-split plot with supply routes as main plots, maturity stages as subplots, storage conditions as sub-subplots and random allocation of treatments with each subplot. An experiment was conducted in two seasons during winter harvest and during summer harvest. The results revealed highly significant impact (P < 0.001) of individual technologies in maintaining quality, which was measured by number of parameters including colour, texture, TSS, physiological weight loss, respiration rate, total phenolic compounds, Total antioxidant capacity and general marketability. Furthermore, integrated technologies had more superiority in maintaining quality of tomatoes. Therefore anolyte water and Gum Arabic coating need to be researched further as potential substitutes of chemical treatments that are currently used by tomato industry.