Masters Theses

Date of Award

12-2002

Degree Type

Thesis

Degree Name

Master of Science

Major

Biosystems Engineering Technology

Major Professor

Lester O. Pordesimo

Committee Members

Jochen Weiss, Luther R. Wilhelm

Abstract

Soybeans, one of the world’s leading cash crops, contain appropriately 20% lipid. Currently, soybean oil is the principal vegetable oil used in the U.S. and the world market, totaling 29% of the world vegetable oil production in 2001. Development of extraction technology that could increase oil yield would thus significantly enhance the profitability of the soybean industry and reduce processing costs significantly. It has been shown that both ultrasound-assisted and microwave-assisted extraction methods can enhance extraction of phytochemicals from plant sources while reducing processing time and solvent consumption. However, little is known about how ultrasound and microwave can affect the soybean oil extraction.

The main objectives of the research were to (1) determine the effect of ultrasound on soybean oil extraction, (2) determine the effect of microwave on soybean oil extraction, and (3) study the effect of different solvents on soybean oil extraction. Thus, this study aimed to compare the yield, composition, and quality of extracted soy oil obtained by traditional and ultrasound-assisted or microwave-assisted processing methods. The effects of different solvents and levels of ultrasound or microwave treatment on the extracted soybean oil were evaluated. Both laboratory-scale ultrasound-assisted and microwave-assisted soybean oil extraction procedures were developed in this research.

Ultrasound-assisted extraction was found to be a simpler and more effective alternative to traditional methods for soybean oil extraction. Two different soybean or using a traditional procedure without ultrasound application. It was found that the ultrasound-assisted extraction of oil from soybeans yielded greater oil than the traditional method regardless of soybean variety. Higher sonication intensity allowed for more efficient oil extraction (faster and greater oil yield). The solvent influenced the sonication enhancement, i.e., the oil yield extracted by this procedure was highest when using hexane:isopropanol solvent mixture. Fatty acid profile analysis measured by GC indicated that the oil quality did not appreciably change from traditionally extracted oil when ultrasound assistance was used. varieties (TN 96-58, N 98-4573) were used in the experiments. Oil was extracted using different solvents [hexane, isopropanol, and mixed solvent (hexane:isopropanol 60%:40% v/v)] under either direct sonication by an ultrasonic probe at intensity levels ranging from 16.4 Wcm-2 to 47.6 Wcm-2 or using a traditional procedure without ultrasound application. It was found that the ultrasound-assisted extraction of oil from soybeans yielded greater oil than the traditional method regardless of soybean variety. Higher sonication intensity allowed for more efficient oil extraction (faster and greater oil yield). The solvent influenced the sonication enhancement, i.e., the oil yield extracted by this procedure was highest when using hexane:isopropanol solvent mixture. Fatty acid profile analysis measured by GC indicated that the oil quality did not appreciably change from traditionally extracted oil when ultrasound assistance was used.

Microwave-assisted extraction can increase the oil yield and extraction process rate. Three different solvents (hexane, isopropanol, and a mixed solvent (hexane:isopropanol 60%:40%, v/v)) were used to extract soybean oil after being irradiated with microwaves (2450 MHz) at increasing reaction times. Oil yield obtained with microwave irradiation was highest using the mixed solvent. Microwave-assisted extraction of oil from soybeans yielded markedly higher oil percentages than traditional method, i.e., oil yield of microwave-assisted group was 0.45 g higher than that of control group during a 2 hr. extraction time. Increased microwave reaction times increase oil as well. For the mixed solvent, 4.17 g more oil was extracted when the reaction time changed from 30 to 120 min.

Both ultrasound and microwave treatment had a positive effect on soybean oil extraction. Increases in soybean oil yield were achieved with the hexane:isopropanol mixed solvent. Further research is planned to evaluate the potential of ultrasound- and microwave-assistance in soybean oil extraction.

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