INFLUENCE OF MICROWAVE DRYING METHOD ON THE CHARACTERISTICS OF THE SWEET POTATO DICES

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TEL: 0086-510-85877225; FAX: 0086-510-85877225; EMAIL: min@jiangnan.edu.cn

Abstract

ABSTRACT

Three different drying methods, microwave-spouted bed drying (MSBD), microwave-vacuum drying (MVD) and hot air drying (AD), were used to dry diced sweet potato. The drying characteristics and product quality are discussed in terms of the drying kinetics, rehydration ratio, expansion ratio, breaking force (crispness), product color and retention of β-carotene. As expected, the drying rates in MSBD and MVD were much faster than that obtained in hot AD; the largest drying rate was obtained in MSBD with 2.5 W/g microwave (MW) power level. The products dried using MSBD and MVD displayed good puffing: rehydration ratios were about 2.0 after 18 min, expansion ratio was close to 1.0, and the breaking force below 600 g. The color of MSBD product was uniform as well. Retention of β-carotene was about 80% in MSBD and MVD but only 40% in AD product compared with that present in the fresh produce.

PRACTICAL APPLICATIONS

MSBD can be used to produce dried sweet potato dices with good expansion ratio, low breaking force, high rehydration ratio and better color, compared with MVD and AD. Furthermore, MSBD overcomes the uneven characteristics observed when only MW drying is applied. MSBD could be regarded as a potentially new drying technology for production of high-quality snack foods in the form of puffed sweet potato dices.

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