Effect of maturity and drying temperature on extraction of pepper essential oil and oleoresin
1993
Muralidharan, S.
Black pepper (Piper nigrum L.) is a major spice crop for Thailand. Processing of pepper in the form of essential oil, and oleoresin is an attractive option, because of the current slump in the price of whole pepper in international market. Pepper harvested from Chanthaburi province, at three different stages of maturity differentiated by the color, i.e. the green, yellow, and the red were subjected to three different drying temperatures, 50 deg C, and 60 deg C using an oven and the traditional sun drying method. Drying characteristics revealed that moisture removal followed a modified log model. A maximum oil content of 3.12 % on a moisture free basis was extracted from the green maturity stage. The oil content declined to 2.35 % for yellow and 2.0 % for red stage. Slightly higher oil contents were obtained from the pepper dried in an oven as compared to the sun dried pepper. No significant difference was observed between green stage of pepper dried at 50 deg C and 60 deg C. Oil extraction data was fitted to an exponential model for the three stages of maturity. A maximum oleoresin yield of 13 % was extracted from the green stage of pepper. The oleoresin yield declined to about 9 % in the yellow and red stages. No significant difference was found due to the drying temperatures at a 95 % confidence level. The extracted oil was subjected to physicochemical tests such as optical rotation, refractive index, and specific gravity, and was found to conform to the values specified by the international standards. A minimum piperine content of 50 % was obtained from the extracted oleoresin, which is higher than the Indian standard norm of 40 %. Harvesting of pepper at green stage during November to December and drying artificially at 60 deg C is recommended, for its processing into essential oil and oleoresin.
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