EFFECTS OF PROCESSING METHODS ON THE QUALITY OF TURMERIC (CURCUMA LONGA L.)

Abstract

Turmeric (Curcuma longa) plant belongs to Zingiberaceae family. The quality of turmeric depends largely on curing process. Ethiopian farmers’ turmeric processing methods are boiling and drying carried out by conventional method which is slow, tedious and labour intensive. This study was conducted in order to recommend appropriate processing and drying methods and also to share the information for the scientific community. The experiment consisted of six independent rhizome processing methods (10, 20, 30 minutes of steaming time; 3 and 5 millimeter slice thickness and the conventional boiling) and two drying methods (open-sun and poly tunnel solar drying) laid out in 62 factorial arrangement using CRD with three replications. Data of physical and biochemical quality attributes and drying duration were taken. All data were subjected to analysis of variance and mean separation was done by using LSD at p<0.05. The highest and lowest percentages recovery, 19.47 and 17.8 respectively, were found from 20 minutes steaming time and the conventional practice. The conventional practice had significantly highest value (8.46%) of corckish layer. The percentages of thickness and length shrinkage showed significant (P<0.05) increment when increasing steaming time. The highest brightness color value of 52.7 was recorded for the sample steamed for 10 min and sun dried. Significantly much shorter duration of drying (4 days) was observed for sliced and poly tunnel dried sample. When steaming time increased from 10 to 20 and 30 min, the ash content significantly decreased from 8.58% to 7.66 and 7.48%, respectively. The highest essential oil content (5.63 ml/100g) was recorded for 5 mm sliced sample. Significantly highest value of ash, Oleoresin, moisture and crude protein contents with values of 8.86, 17.7, 9.47 and 6.34, respectively, were recorded for samples with 10 min steaming time and poly tunnel solar dryer. Essential oil content of 5.72% recorded from sliced and solar dried sample was significantly the highest. Generally, this study showed that turmeric processing methods (steaming and slicing) and Polly tunnel solar drying method had showed better performance as compared to the conventional processing method in regard to all the parameters considered under this study.