METHODS OF DRYING OF TOMATO SLICES AND THE EFFECT OF THE USING OF ITS POWDER ON THE PRODUCTION AND CHARACTERISTICS OF EXTRUDED SNACKS

Abstract

In this study, tomato samples were subjected to different pre-treatments (0.2 % sodium meta bisulphate (Na 2 S 2 O 5), 1 % calcium chloride (CaCl 2)and steam blanching. Untreated samples served as control. After pretreatment, tomato slices were subjected to three different drying methods (oven air, solar and microwave / hot air) and milled in grinder to powder. Tomato powder had been packed in multilayer films consists of low density polyethylene, aluminum and Polyester. Physical properties and bioactive compounds (total phenolic compounds, total flavonoids, β-carotene, lycopene, and ascorbic acid) of tomato powder were studied. The powder produced was used in functional food (extruded snacks). Dried tomato powder was added to corn grits flour at levels of 3 and 6% and extruded in a single screw extruder to produce healthy extrudes. Sensory characteristics and physical properties of snacks were evaluated. The studied parameter (moisture, total phenolic, total flavonoids lycopene and β-carotene) were significantly (p ≤ 0.05) affected by different pretreatments processes and drying methods. The results showed that solar drying had negative effect of all characteristics of tomato slices and the color was dark. The sensory analysis findings showed that, extrudes contain 3 and 6% tomato powder (dried by oven and microwave/hot air) had significant higher color and taste scores. Adding tomato powder at level 6% led to increment in scores of crispness, flavor and overall acceptability.-1538-1. INTRODUCTION omato (Lycopersicum esculentum) is one of the major vegetables in the world, (FAOSTAT, 2010) indicates that the second most cultivated vegetable in the world was tomato, which gave a worldwide production of more than 100 million Mg per annum. Tomatoes and tomato products are rich in health-related food components as they are good sources of carotenoids (in particular, lycopene), ascorbic acid, vitamin E, folate and total phenolic compounds. Dried tomato in the form of slices or powder helps to develop new food materials for ready to eat products. Many chemicals including sodium chloride, calcium chloride, potassium meta-bisulphite and sucrose had been used by many authors (Lewicki et al., 2002; Davoodi et al., 2007; Souza et al., 2007and Marfil et al., 2008) as pre-treatment for tomato drying. Convective hot air is the drying most widely used technology for vegetables with air temperature around 55˚C and final moisture content of about 4-8% as wet weight basis (Grabowski and Marcotte, 2003). Solar drying can be considered as an elaboration of sun drying and is an efficient system of utilizing solar energy. Microwave drying uses electromagnetic waves as a form of energy, which interacts with materials, thus generating heat and increasing the drying rate dramatically (Mujumdar, 1987). Food extrusion of breakfast cereals is defined as a cooking-extrusion process based on expanded, high voluminous, crispy and taste acceptable products extrudates (Hagenimana et al., 2005). This study was undertaken to investigation the effect of different pre-treatment processes (sodium meta-bisulphite, calcium chloride and steam blanching) and different drying methods (oven air, solar and microwave/ hot air) on the drying characteristics and some quality attributes of pre-treatments tomatoes. Study the possibility of using tomato powder in extruded products (snacks).