Effect of Drying Methods and Storage Conditions on Nutritional Value and Sensory Properties of Dehydrated Tomato Powder (Lycopersicon esculentum)

Abstract

The effects of two drying methods, (oven drying and sun drying) of tomatoes and storage conditions of the products were studied to assess their effects on chemical, nutritional quality and sensory properties. Eleven kilograms of Fresh tomatoes were obtained from Ankpa metropolis central market, Kogi state Nigeria. The fruits were washed, weighed, and divided into two equal parts (51/2 kg), one part was sliced into a non sticky pot, dehydrated, pressed through colander and re-dehydrated into a thick moulding consistency, it was sliced and oven dried at 60°C at a constant stirring using skewer. The second portion of the tomato fruits was blanched in 100°C hot water, sliced and sun dried. The Nutrient composition was determined using standard methods, the microbiological examinations were carried out using culture plate methods and sensory evaluation was evaluated using 9 points hedonic scales. Moisture contents in oven dried and sun dried tomato powders fluctuated between 8 – 10% and was slightly higher in the sun dried tomato product. The chemical analysis of four macronutrients (protein, fat, crude fibre and carbohydrates) were completed and the results were expressed as percentage dry matter. Significantly higher protein (3.70%), fat (0.82%) and crude fibre (6.37%) were found in the oven dried tomato product (P<0.05) compared with the respective values obtained in the sun dried tomato product and the carbohydrate contents was 77% in both. The chemical analysis of the five Phytochemicals; total flavonoid, tannins, Phenolic acid, and alkaloid were reported and their mean levels were significantly higher in the oven dried tomato compared with the values in sun dried tomato product. The microbiological examination showed that under storage conditions for 3 months, the total viable counts were of oven dried and sun dried (5.7x103cfu) and (7.7x105cfu) per gram of tomato, respectively. Under storage conditions for 6 months, the total viable counts increased slightly in the sun dried tomato product. Fungal growth was not visible in both tomato products after 3 months of storage. Yet, under storage conditions for 6 months, mean values were 1.9x103 and 2.1x105 colony forming units per g of oven dried and sun dried tomato, respectively. Sensory evaluation which included four parameters, i.e., revealed taste, flavour, consistency, colour beside overall acceptability were significantly superior (P<0.05) in the oven dried tomato product over the sun dried.