[5-1015-C] Postharvest/Food Technology and Process Engineering (5)

[5-1015-C-03] Effects of Pre-drying treatment and Drying-air Temperature on Moisture Ratio and Effective Moisture Diffusivity of Tomato (Nigerian Local and Foreign Varieties)

*Obafemi Ibitayo Obajemihi¹, Joshua Olanrewaju Olaoye², Mayowa Saheed Sanusi¹ (1. Food Engineering Department, University of Ilorin(Nigeria), 2. Agricultural and Biosystems Engineering, University of Ilorin(Nigeria))

キーワード：Hausa, Tiwantiwa, Honey and Sugar, Tomato

Tomato is a crop that is highly perishable and there are huge postharvest losses incurred annually in Nigeria. Drying of the fruit is important and suitable for developing economies. However, the heat employed during drying of tomato can influence its quality adversely, as a result it is important to use pre-drying treatments prior to drying operation. Therefore, the aim of this research was focussed on studying the effects of pre-drying treatment and drying-air temperature on moisture ratio (MR) and effective moisture diffusivity of tomato. Three varieties (Hausa, Tiwantiwa and Roma VFN) of fresh tomato were obtained from local farmers in Ilorin province, Kwara state of Nigeria. The samples were sorted and cleaned under running water, and were sliced at different thicknesses (5 mm, 7.5 mm and 10 mm), deseeded and blanched in hot distilled water at 90oC. The samples were further pre-treated using different chemical and osmotic solutions (2% ethyl acetate, 1% MgCl2 .6H₂O and 0.5% Na₂S₂O₅, 0.5% NaCl and 40oBx of honey and sugar) and Control (Non-pretreated). Samples were drained for 10 minutes after pre-drying treatment and were dried at different temperatures (45, 55 and 65oC) in an automated forced convection cabinet dryer (FCCD) instrumented for the purpose of this experiment. Weight loss of the samples were recorded at different intervals (15 - 60 min) on the trays per stage with the aid of a weight reduction sensing mechanism attached through the rear of the dryer. The drying process was stopped (through a computer system connected to the dryer) when the samples had reached their final moisture content < 5% (db). The data obtained from the drying process were used to compute the samples moisture ratio and effective moisture diffusivity and were analyzed using regression and analysis of variance (ANOVA) with Design expert v. 6.0.6 statistical tool at p < 0.05. The results obtained show that samples lowest MR were obtained under these conditions; processed Hausa variety, 10 mm thickness, ethyl acetate pre-drying treatment and dried at 55oC while highest effective moisture diffusivity were obtained under these conditions processed Hausa variety, 5 mm thickness, honey and sugar pre-drying treatment and dried at 65oC in a FCCD. It was therefore concluded that processed Hausa variety was more preferable to other varieties used as it promotes low MR and high effective moisture diffusivity during the drying process. This will help reduce energy consumption associated with drying process.