Atmospheric freeze-drying of potato (Solanum tuberosum)

Abstract

By applying the method known as Atmospheric Freeze-Drying (AFD) which uses low temperature and calcium chloride or silica gel as hygroscopic agents, two varieties of potatoe (Gabriela and Chaucha) were dehydrated. Three different pre-treatments were performed on the potatoes for the analyses. From the obtained data, following values were estimated: (i) the coefficients of surface mass transfer (from 61.77 to 148.55 kg·m-2·s-1), (ii) the heat transfer (from 5.75 to11.22 W·m-2·°C-1), (iii) the un-dimensionless number (from 1.03 to3.98), (iv) the drying time (from 200.00 to 303.26 h) and (v) the rehydration index (1.7 - 2.7). Furthermore, the mass transfer mechanism that controls the AFD was assessed. This process was assessed, and changes in the colour of the products at three different stages of the process using the Yellowness Index, and the microbiological properties of the atmospheric freeze-dried potatoes, were analysed. It was concluded that, the drying of potato slices by AFD can eliminate microbial growth and chemical reactions, and the pre-treatments step is necessary to prevent browning.