A Comparative Study of Drying of Muga Cocoons using Convection and Infra-red Heating Method

Background: Muga is an exclusive golden-colored silk produced by the Antheraea Assamensis silkworm species in North-east India. In the silk processing stage, drying of Muga silkworm cocoon is essential to prevent the pupa from emerging from the shell and to preserve the cocoons for a longer period (3-6 months). It is necessary to reduce the potentially harmful high moisture level in the cocoon shell and pupa body to an optimum or safe level of moisture content (6-12%). In India, the natural sun drying method is the most common method to preserve Muga cocoons for a longer period. Considerably losses may occur using the sun-drying method due to various effects such as rodents, insects, rain, microorganisms, excessive temperature, etc. To address this issue the study was conducted to improve the quality of Muga silk yield using a comparative study between Convection and IR heating methods for cocoon drying. Methods: In this study, Muga cocoons were dried properly at optimum temperature (50-100°C) to obtain a safe moisture level for getting quality Muga silk. The drying of the Muga cocoon is processed using convection (1 kw) and Infrared (650 watts) modes of heating for the same duration of time. Muga cocoons were placed in a drying chamber initially at a high temperature (100±5°C) using both convection and Infrared heating methods separately to maintain the moisture content to an optimum level. It took approximately 75 minutes to obtain the temperature 100 from room temperature and every 15 minutes temperature measure was recorded for both methods and compared. The parameters studied were temperature, time, cocoon weight, shell weight, shell ratio and moisture content. These parameters were examined, evaluated and compared for both the Convection and IR heating methods. Result: The comparative study results indicated that the performance of the studied cocoon parameters namely temperature, cocoon weight, shell weight, shell ratio and moisture content are approximately similar for both convection and IR heating methods. Moisture content was maintained at the optimum range (6-12%) for both the convection and IR methods. The study provided a better performance using the IR heating method as compared to convection heating concerning energy consumption and safety for the same duration of time. Energy consumed by a 1 kW convection heater is 1.25 kWh, whereas energy consumption in a 650-watt IR heater is 0.8125 kWh.