Effect of pre-treatments, freezing methods and drying temperature on the quality parameters of dehydrated potato cubes

Freezing method, pre-treatment, drying temperature and residual moisture content affect the quality of the dehydrated potato cubes. Blanching of potato cubes at 70°C and soaking in solution containing sugar, NaCl and glycerol followed by slow freezing and drying at 60 and 40°C showed 1:2.2 and 1:1.75 rehydration ratio (RR), 20 and 25 min rehydration time (RT), 34 and 58% shrinkage, respectively. While the blast freezing and drying at 60 and 40°C showed 1:2.1 and 1:1.6 RR, 22 and 24 min RT, 36 and 60% shrinkage, respectively. Above treatment without glycerol and subjected to slow freezing and drying at 60 and 40°C showed 1:1.6 and 1:1.2 RR, 30 and 36 min RT and 46 and 59% shrinkage, respectively. Whereas, blast frozen 60 and 40°C dried samples showed 1:1.4 and 1:1.22 RR, 36 and 35 min RT, 57 and 62% shrinkage, respectively. All the samples blanched in presence of glycerol and subjected to slow freezing and low temperature drying had firm texture. The thermal analysis of the samples revealed an elevation in glass transition temperature (Tg) of the samples subjected to slow freezing, glycerol treatment and dried at 60°C.