Foam-mat Drying of Carrot Juice and Thin Layer Modeling of Drying

Abstract

Drying of fruit and vegetables are critical step of processing which can be very destructive for nutrients and especially for bioactive compounds. However, novel drying methods like foam-mat drying helps to decrease the drying period and exposure to drying air therefore protect the bioactives against thermal degradation as well as improving final powder quality. The foam-mat drying of carrot juice foams and modelling of experimental drying data with theoretical models has not yet been studied in the literature. In this study, the effects of foam-mat drying at 50, 60 and 70°C on the drying behavior of carrot juice with the addition of 15% egg albumen (EA) and 15% egg albumen+ 10% whey protein isolate (WPI) as foaming agents and thin-layer modeling of the foams at different thicknesses was evaluated. Compared to control sample (only carrot juice), the drying time of the foamed carrot juice was reduced by 25% to 60% depending on the foam thickness and drying temperature. This result was consistent with the effective diffusion coefficients, since the control sample had comparably low values than the 15% EA and 15% EA+10% WPI foams. Among the fitted mathematical models, Midilli et al. had better prediction capacity with the highest adjusted correlation coefficients, the lowest sum of squared error and root mean square error values for every formulation, foam thickness and drying temperatures compared to other theoretical models.