Optimization of Refractance Window Drying Conditions for the Development of Beetroot Powder

Abstract

Refractance window drying technology can be used to produce high quality dried vegetable products due to its excellent retention of heat sensitive nutrients, organoleptic properties and bioactive compounds. This study optimized conditions for drying of grated beetroot using RWDT. I-optimal design in Design Expert software was used to generate temperature-time combinations in form of runs. The independent factors considered included drying temperature (70-900C) and time (40-120 minutes), and the responses included moisture content and vitamin C concentration. Response surface methodology (RSM) was used to optimize the drying temperature and time. The optimum solutions generated for RW drying temperature and time were 900C and 40 minutes respectively. The respective values for vitamin C and moisture content under optimal drying conditions were 50.4 mg/100g solids and 12.0% wet basis respectively. Models for prediction of these values had R2 values of 0.9855 and 0.9950 respectively, and non-significant lack of fit (p < 0.05) and the % retention of vitamin C was 90.0%. This indicates the suitability of the model in predicting the RWD operating conditions and the percentage retention shows that RWD can produce dried beetroot powder of high nutritional quality.