A Comparative Study of Combined Microwave Techniques for Longan (Dimocarpus longan Lour.) Drying with Hot Air or Vacuum

Abstract

AbstractThe aim of this study is to find a better drying method to replace conventional hot air drying (HAD) in terms of faster, energy efficient and better product quality. Two alternative drying techniques, microwave combined with hot air drying (MHD) and microwave vacuum drying (MVD), are compared in this study to dry peeled and destoned longan fruit. Both MHD and MVD reduced the drying time up to 48 % and energy consumption as compared to HAD. These techniques provided lower product redness, yellowness and shrinkage but higher lightness and porous structure as compared to HAD. MVD reduced hardness and toughness of the dried product. MHD provided the highest preference score in terms of colour and shape and was as acceptable as the commercial product dried by HAD. MHD is the most suitable method for longan drying.