Abstract

                                Step type and cabinet solar dryers were used for drying vermicelli in cottage industry. Initially Jaboratory studies were undertaken to dry the vermicelli in an electric hot air oven to find out the optimum hot air temperature, yielding the best product quality. The time required for drying vermicelli at five temperature namely 40, 50, 60, 70 and 80°C were determined along with the quantity of dried broken vermicelli less than 25 mm length, to analyze the quality. Vermicelli of 0.7 mm diameter, dried at 55 to 60°C yielded 21±1 per cent broken. Another laboratory study was conducted on step type and cabinet dryers to record the stagnant temperatures for 0, 25, 33, 50 and 100 per cent opening area of ventilation outlet. Based on the study, the air outlet opening area was optimized to maintain 55 to 60° C temperature inside the dryers. The dryers were then installed in a cottage industry and the product was dried maintaining the optimized temperature. The time taken to dry a batch of vermicelli from 24 to 6 per cent moisture on a sunny day was 120 min in the dryers, compared to 315 min in open air. The drying time observed on the dryers during cloudy day was 180 min as compared to 420 min in sun drying with thin layer of spreading. The rehydration studies on the dried products from all the treatments indicated 200±10 per cent water absorption within 20 min using 50°C hot water.

Key words : Vermicelli, Solar drying. Cabinet dryer. Step type dryer, Relydration, Drying temperature.