EFFECT OF PROCESSING METHODS ON QUALITY OF TURMERIC (Curcuma longa L.) FINGER RHIZOME GROWN IN TEPPI, SHEKA ZONE, ETHIOPIA.

Abstract

Turmeric is a rhizomatous herbaceous perennial plant of the ginger family, Zingiberaceae, is a widely cultivated plant. Turmeric was originally valued mainly as a spice for food and natural dye for clothing until recently when it was discovered as a potential source of new drugs for a variety of diseases. A study was conducted to determine the effects of boiling time, rhizome form and drying methods on the quality characteristics of turmeric. The experiment consisted of four levels of boiling times (15, 30, 45,and 60 minutes); two levels of rhizome forms (sliced and unsliced rhizome) and two levels of drying methods (open-sun drying and poly tunnel solar drying) laid out in a 4x2x2 factorial arrangement using Completely Randomized Design (CRD) with three replications. Data of Physical quality parameters (recovery percentage, percentage of corkish layer, percentage of thickness shrinkage, length shrinkage, whole rhizome color and powder color; and biochemical quality data (oleoresin content, essential oil content, curcumin content, ash content and moisture content data were taken using standard methods and subjected to Analysis Of Variance (ANOVA). Mean separation was done by using LSD at p<0.05. Highest recovery percentages of 20.45 and 19.20% were attained from the shortest (15 min) boiling time of unsliced samples dried in sun. Lowest corkish layer (4.6 to 6.43%) were recorded for the shortest (15 min) boiling time regardless of drying method and rhizome form. Highest rating (2.73 to 2.92) of rhizome color were observed for sliced samples irrespective of drying method and boiling time. Most of high rated (3.17 to 3.68) powder color were obtained from unsliced samples regardless of boiling time and drying methods. Boling of unsliced rhizomes for 15 min followed by tunnel drying yielded higher oleoresin, curcumin, essential oil content, and powder color. Poly tunnel solar dried products retained the colour more than the open air sun dried samples. Boiling for 60 minutes then slicing paired with sun drying resulted in reduction of quality such as oleoresin, curcumin, essential oil, rhizome colour and powder colour. Unsliced rhizomes also resulted in highest (4.06 to 4.46%) curcumin content when combined with solar tunnel drying. Same combination of treatments resulted in highest (16.53 to 17.57%) oleoresin content and (3.93 ml/100g) of essential oil. The sliced rhizome had relatively lowest moisture content than unsliced rhizome. Generally, all three factors display significant role in influencing different quality attributes of turmeric rhizomes. Among the various boiling time, rhizome form and drying techniques studied, unsliced rhizome boiled for 15 minutes followed by poly tunnel solar drying was found superior based on the physico-chemical analysis and concluded for future study on turmeric processing.