DEVELOPMENT AND PERFORMANCE EVALUATION OF A MACHINE FOR EXTRACTING ESSENTIAL OIL FROM SELECTED AGRICULTURAL MATERIALS

Abstract

Essential Oils (EOs) are imported into the country with little or no significant production from the nation. Hence, the development of a simple essential oil extractor (DE). The machine was evaluated using different citrus rinds sweet orange (Sw), natural tangerine (Nt) and tangallo (To) and compared with other four standard extraction methods: Soxhet (Sox), Pressurized Liquid Extractor (PLE), Hydro-distillation (HD) and Supercritical carbon-dioxide (SCO2). The developed extracting system consists of a boiler, water condenser and oil collector. The boiler provides space for water, steam, distillation tray and furnace, while water transfer energy from combustion or a processed steam to an operating fluid. The boiler is a low pressure natural circulation water boiler with an allowable pressure of 103.42kpa or less with about 20 litres in capacity and requires about 5175 kJ of heat energy to operate for an hour. The Sw rinds cut transversely (SwT=Sw1 and Sw3) and longitudinally (SwL=Sw2 and Sw4) of moisture contents 58 and 39 % (dry basis) were fed to the DE while the Nt and To cut longitudinally were fed at moisture contents 32 and 28 % (dry basis). Milled Sw of moisture content at 6.5% (dry basis) was used in the other four extraction methods. The extracts were purified using chemicals and Thin Layer Chromatography (TLC) to determine the presence of other compounds. Bioactivity profile such as total phenolic contents (TPC) and antioxidant activity was detected using 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS radical) and 22 -diphenyl, 1- picryl-hydrazyl (DPPH).The volatile profile of EOs was determined using gas chromatography mass spectrometry (GC- MS) with auto-sampler. The boiler has an efficiency of 83 %. The extracts yield ranged from 0.213 - 53.34 % with soxhlet having the highest and DE the lowest value. Transversely cut sweet orange rinds (Sw1) has higher yield than longitudinally cut rind (Sw2) at constant moisture content from the DE extracts. The result of Sw1 was greater than that of Sw3 cut transversely under different moisture content. The total phenolic compounds (TPC) ranges from 504-1,319 mg GAE/g vii with Sw1 having the highest and PLE the lowest value. The Sw1 had higher value of TPC than Sw2 at constant moisture content cut longitudinally. The result from purified extracts using TLC and chemicals indicated additional polyphenols compounds with volatile oil from PLE, SCO2, soxhlet and that hydro-distillation and extracts from DE are pure essential oil. The antioxidant activity results using ABTS radical ranged from 11.53 – 11.77 mg trolox/g with highest and lowest values in Sw1 and SCO2, respectively. The DPPH value ranged from 22.49- 71.62 mg/g with Sw1 and PLE having the highest and lowest values respectively. The results of antioxidant using ABTS indicated that Sw1 cut transversely had the highest value for the antioxidant than the other treatments from DE and similar result was recorded for DPPH. It can be concluded from the result that the fresh sample of sweet orange rinds cut transversely performed best with the DE. The result from statistical analysis using Pareto chart and Response surface analysis (RSA) generated from PLE showed that yield and ABTS were influenced by temperature (T) and by the interaction between T and C (T×C).The regression model generated for first order can be used to predict the yield and ABTS of sweet orange rinds. The result from GC-MS showed the presence of 92 constituents of volatile compounds that were identified for the citrus rinds belonging to seven functional chemical classes of natural products: terpenes, acids, oxides, esters, aldehydes, aromatic and alkanes. The chromatogram mass spectra for the fresh sweet orange rinds cut transversely (Sw1) and dried sweet orange rinds (HD) showed the identification of volatile compounds above 98 %. This indicated that there was no significant effect of drying on the phytochemical constituents of volatile compounds of sweet orange rinds essential oil. Thus the developed extractor is good for extracting essential oil from citrus species rinds with high value of total phenolic contents and antioxidant that conformed to the international standards. This indigenous machine is simple and can be used by the local farmers, small and medium scale entrepreneurs.