Effect of drying methods on the quality of tiger nuts (Cyperus esculents L.) and its oil

Abstract

This study investigated the effect of 4 different drying methods, i.e. sun-drying (SD), oven-drying (OD), microwave-drying (MD) and vacuum-drying (VD) on the color and microstructure of tiger nuts and quality of its oil. The results showed that SD and VD samples had the desirable color. The morphology of starch granules in cells was changed greatly in OD and MD samples. MD sample had the largest oil yield (22.26%), while VD sample showed the highest extraction rate. The oil extraction kinetic can be well described by an exponential model. In respect of oil quality, SD was ideal for retaining carotenoids, phytosterol and unsaturated fatty acids. The oil from MD sample had the highest oxidation degree, but the longest introduction period (53.27 h), while the one from VD sample had the opposite effect. No significant differences were found in acid value and tocols (tocopherols and tocotrienols) profile between all oil samples. Our results provided a guidance for the selection of drying technique based on specific processing purpose.