Optimization of aqueous enzymatic extraction of oil from peanut

This study aims at developing a new eco-friendly and highly efficient method of gaining vegetable oil, as an alternative to commonly used solvent extraction method. As an alternative, enzyme added water extraction method has been chosen, and vegetable oil was gained from peanut seeds. Because of the low efficiency of extraction, it has been aimed to demolish plant cell walls, and let the components inside cells release easily, by adding/utilizing enzyme(s). Optimum conditions was determined, by changing the pH of environment, the amount of enzyme per each grams of seed, the incubation time and temperature parameters. In the second part of the study another enzyme at different rates was added experiment medias and work with the two enzymes was investigated. In this study, peanut seeds which has grown in Osmaniye/Turkey was utilized after being grinded, and the first oil content of the seeds was determined as 49%. Alcalase 2,4 L FG was selected as enzyme. The pH of the studying environment was determined as 4, 5, 6, 7, 8 (1:7 seed:buffer solution); the amount of enzyme per each gram of seeds was determined as 0,25, 0,5, 0,75, 1, 1,5 mL; the incubation time was determined as 6, 18, 24 hours, and the incubation temperature was determined as 40, 50, 60 ºC. The results were compared by calculating the efficiency of oil. The efficiencies of gained oil varied from 66,3% up to 75,5%. When it came time to evaluate the results; the maximum efficiency of oil gained in conditions of pH 7, 0,25 mL enzyme/g of amount of seed, 18 hours of incubation time and 50 ºC of temperature. The maximum efficiency of oil was detected as 75,5%. When previous studies close to this topic are examined, it can be seen that also pectinase (enzyme) provide higher efficiencies on gaining vegetable oil from peanut seeds. Therefore, it was decided to examine efficiency of alcalase-pectinase mix in different ratios. First of all, results from previous studies were adapted to optimum conditions of this study. pH 5, the environment that provide maximum efficiency with pectinase from previous study and pH 7 from current study were chosen, and it was studied for 18 hours incubation time with 0,25 and 0,5 mL amount of enzyme per each grams of seed. Oil yields were increased in the pH 5 medium from 60,6% to 65,1% and in the pH 7 medium from 58,5% to from 63,3% with increasing enzyme amount. The yields that was obtained with pectinase was similar in the two selected media. The results has shown that the medium of pH 7 was appropriate for pectinase.Then, 0,25, 0,5, 0,75 and 1 mL pectinases/ g of amount of seed were added to the medium in optimum operating conditions of alcalase. The rate of 0,25 mL alcalase/ g of amount of seed: 0,5 mL pectinase/ g of amount of seed, oil yield was reach 82% and maximum result had been obtained. In the last part of the study, solvent extraction, aqueous extraction and enzymatic aqueous extraction were compared. The yield that was obtained with solvent extraction was 95,7% and hexane was used as solvent. Aqueous extraction yield was detected as 57,5%. This result has shown the effect of enzyme. This value was increased to 82% with the enzyme additive and a yield was obtained that could compete with solvent extraction. The most important disadvantage of this method, which let the production of good quality oil with no needs to refining or purification, is high cost of enzymes. To provide the water circulation and recycle of the enzyme, or to use immobilized enzymes may reduce costs, and let this method be common and attractive. Key words: Peanut (Arachis hypogaea), enzyme, aqueous extraction, optimization