Process of foam-mat drying of purple rice bran extract and evaluation of product properties

Abstract

The present study examined the process of foam-mat drying “Cám” purple rice bran extract, including optimization foaming conditions and effect of drying temperatures on the drying behaviours and powder's qualities. The egg album and xanthan gum at different levels were used as foaming agents, which further optimizied by the response surface methodology. The optmial foam was dried at four levels of temperature (50-80oC). Moisture content was further recorded every 30 minutes. Four common emperical models were applied for predicting the pattern of moisture content. Under the effect of heat treatment, the final qualities of Cám purple rice bran foam-mat dried powder were determined. The results showed that when egg albumin and xanthan gum were used, 12.04% and 0.337% could maximize foam expansion and stability. These conditions could facilitate the efficiency of the drying process. Moreover, among the four models, the Page model showed the best fit for predicting the change in moisture ratio. The effective diffusivity and activation energy were from 6.73 x 10-10 to 1.66 x 10-9 m2/s and 22.72 kJ/mol, respectively. The study also revaled that at temperature of 70oC, the product could maintain high antioxidant proper conditions for storage and high acceptance by consumer.