Effect of Sun-Drying on Some Quality Characteristics of Sweet Potato Chips

Abstract

In the Lake regions of Tanzania sun drying of sweet potatoes is normally done on thatched roofs after peeling and slicing the sweet potato tubers into chips. Future use of alternative drying surfaces including corrugated iron roofs may be practised as thatched roof houses are being slowly replaced with corrugated iron roof houses. This paper investigated the use of three different drying surfaces for various thickness levels of sweet potato chips. The surfaces employed included raised coffee wire (perforated surface), ground floor and corrugated iron sheet and the chip thickness levels were 4, 8, 12 and 16 mm. Drying was done continuously for a period of about 56 hours including day and night. The parameters investigated were weight loss during drying and moisture content derived from the weight loss values. Moisture content measured drying performance of the different treatments. Microbial count and sensory evaluation of the dry samples was investigated. Final moisture content on the different drying surfaces were as follows: 21.94%and 43.13%on the perforated surface, 23.71%and 44.50%on the ground surface and 24.5%and 39.82% on the corrugated iron sheet for 4 and 16 mm slices, respectively. The mean log counts of mould on the perforated surface and the corrugated iron sheet ranged between 8.2 and 8.4 compared with 9.09 on the ground floor. Similarly, bacterial mean log counts on the perforated surface and the corrugated iron sheet ranged between 6.43 and 6.52 compared with 7.04 on the ground floor. Perforated surface and the corrugated iron sheet gave sensory quality attributes ranging between 3.36 and 3.92 compared with 2.95 and 3.04 for the ground floor on a 5-point hedonic test. However, the perforated surface gave overall significantly higher (P