Recent advances in drying technologies for carrot and sweetpotato

Abstract

Some recent advances in drying technologies for carrot and sweetpotato are reviewed briefly in this paper. These include a novel low-pressure superheated steam drying (LPSSD), which is an airless drying technology that has recently received much attention as an alternative to conventional hot air drying for its ability to preserve various qualities, either in terms of physical or nutritional qualities, of the drying products. This drying technology finds its use in drying heat-and/or oxygen-sensitive products, which are generally of high values. From recent studies it is found that LPSSD could produce dried carrot of better quality, in terms of shrinkage, color, rehydration behavior and β-carotene content, compared with the products dried by conventional hot air drying and vacuum drying. Another advance technology is the use of combined latent heat storage (LHS) and solar-assisted drying for roots. With the use of LHS, energy saving of up to 40% could be obtained during solar-assisted drying of sweetpotato. The motivations for these technologies range from a need to produce higher-quality products, as in the case of low-pressure superheated steam drying, to a need to conserve energy during drying of low- to moderate-value products, as in the case of solar-assisted drying.