Investigations into The Shelf Life and Nutritional Quality of Fresh Tomato Fruit (Solanum Lycopersicon) Following Two Post - Harvest Treatments.

ABSTRACT

 Tomato production in Ghana is characterized by a glut and high post – harvest losses during the major season followed by scarcity and high prices during the off season. This is the result or absence of a standard method for preservation of fresh fruits. This research was conducted to determine an effective method for the post - harvest treatment of fresh tomato fruits to enhance shelf life while preserving its physicochemical and nutritional properties. Two experiments were conducted, each with a factorial design of 5x2. In experiment one, the fruits were subjected to 0, 1, 2, 3 and 4 kGy gamma radiation and stored at 10±1ºC and 28±1ºC. In experiment two, CaCl2 dissolved in distilled water at 0, 1.00, 1.50, 2.00 and 2.50 % concentrations were used to coat tomato fruits and stored at 10±1ºC and 28±1ºC. Gamma radiation at 4kGy extended the shelf life of tomato by 5 and 9 days above control when stored at 28±1ºC and 10±1ºC respectively. The use of CaCl2 at 2.50% greatly extended the shelf life of tomato by 11 days and 18 days above control when stored at 28±1ºC and 10±1ºC respectively. For both treatments, shelf life increased with increasing dose of radiation/ concentration of CaCl2. Weight loss was higher in control fruits as well as fruits treated with gamma radiation or CaCl2 coating stored at 28±1ºC temperature than treated fruits stored at 10±1ºC. Tomato fruits treated with gamma radiation at 1 and 2 kGy and untreated fruits showed an increase in pH and Total Soluble Solids (TSS) which was paralleled by a decrease in Total Titratable Acidity (TTA) as storage period advanced at both storage temperatures. However, fruits treated with CaCl2 at 1.00% had little effect on pH and TTA of tomato during the storage period. Nutritionally, CaCl2 coating significantly maintained the vitamin C and lycopene concentrations in tomato fruit more than control and gamma irradiation which reduced vitamin C and lycopene contents in the fruits significantly with days of xxi storage. Storage at 10±1ºC better preserved the antioxidants properties of the fruits better than storage at 28±1ºC. Elemental composition (Na, K, Zn, Cu and Mn) of the tomato fruits analysed on the initial and final days of storage showed K to be the element with the highest concentration whilst Zn was the least. Generally, gamma irradiation led to an increase in the concentration of Na and K for all doses whilst CaCl2 coating significantly decreased the concentrations of the same elements at both storage temperatures. Concentrations of Zn, Cu and Mn reduced significantly in the tomato fruits by the final day of storage for all treatments following storage at 10±1ºC whilst there were inconsistencies in the contents of the elements in tomato fruits stored at 28±1ºC. Gamma radiation and CaCl2 significantly reduced the microbial load in tomato at both temperatures compared to the control. The reduction was proportional to increasing dose of irradiation and concentration of CaCl2. However, CaCl2 significantly reduced Total Aerobic Mesophiles as well as Mould and Yeast growth in tomato fruits compared to gamma irradiation at both temperatures. In general, treated tomato fruits stored at lower temperature (10±1ºC) had more stability and longer shelf life as well as the ability to maintain nutritional properties than those stored at 28±1ºC.