COMPARATIVE STUDY OF THE PR Due 10 . F OIL FROM AVOCADO APPLE (Persea americana) USING EXTRACTION AND STEAM DISTILLAT ION

Abstract

This work compared the production of oil from the peri carps (peels) of av cado appl USlno steam distillation and extraction (direct and indirect leaching) methods with respect to th ) ields and economic analysis. An improvised steam distillation set-up was used at three different steam heating rates. It entailed the comminution of the sample materials suspended on a grid (perforated J;Iletal plate) 90 mm above the water level and the application of steam through the material. Variations in time and volume of water used to generate the steam for the process are as follows: 30, 60, 90,120,150 and 180 mins. and 1000 ml, 1250 ml and 1500 ml respectively. The improvised pilot plant was designed with appropriate provision for scaling up. In contrast, leaching method using two different solvents, n-hexane and anhydrous ethanol, were used. The extraction was carried out at different particle sizes, times and boiling points of the solvents. These were as follows: 0.75 mm, 1.00 mm, 1.59 mm and 2.00 mm; 30, 60, 90,120,150 and ] 80 mins.; 60°C and 78°C for n-hexane and anhydrous ethanol respectively. The active principles (oils) from both methods were further processed by treating them with activated clay and heating to a constant temperature of 100°C for 30 min. to produce high quality refined oiL Finally, the crude and refined oils were characterized in order to determine their suitability for industrial applications. The results from steam distillation revealed that the heating rate of 2.57 mlImin (moderate) gave the maximum oil yield of 59.8% whereas 4.72 mllmin (low) and 4.94 mlImin (high) heating rates gave oil yields of 38.7% and 39.6% respectively. On the other hand, the results from leaching method at the optimum extraction time (120 min.) and particle size (0.75 rom), gave optimum oil yields of 21.2% and 23.9% for indirect and direct leaching respectively using n-hexane, 35.9% and 42.0% for indirect and direct leaching using anhydrous ethanol respectively. The physicochemical analysis of the refined oil showed that the oils hfid a saponification value of 196.4, acid value of 5.653, iodine value of 1.27, specific gravity of 0.90261, viscosity of 181.180cp and refractive index of 1,600. The chemical engineering design of the steam distillation pilot plant gave the following specification: Diameter, 0.231 m; Height, 0.464 m and volume, 0.01944 m3 representing the geometry of the reactor with the overall rate controlled by the physical rate processes. The properties of the 'present oils are in conformity with the international standards (ISOffR 21092, ISO 212, ISOffR 210, and AOeS) and as such are potential substitutes for the most oils used for cosmetics and pharmaceutical drugs production. The comparative study of steam distillation and leaching revealed that, based on yields, steam distillation gave a yield of 59.8% compared with 35.2% for indirect and 42.0% for direct leaching. Also, based on economic analysis of the three production method tested, steam distillation method gave a rate of return (ROI) on investment of 78.88% and a payback period (PBP) of 1.3 years compared with 39.8% and 2.5 years for indirect leaching and 61.04% and 1.6 years for direct leaching respectively.