|Venkitasamy, Chandrasekar - University Of California|
|Teh, Hui - University Of California|
|Atungulu, Griffiths - University Of California|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2014
Publication Date: 10/30/2014
Citation: Venkitasamy, C., Teh, H.F., Atungulu, G.G., Mchugh, T.H., Pan, Z. 2014. Optimization of mechanical extraction conditions for producing grape seed oil. Transactions of the ASABE. 57(6):1699-1705. doi: 10.1301/TTSANS57.10570.
Interpretive Summary: Grape seeds contain about 10-22% oil that has high linoleic acid and high vitamin E which are beneficial to prevent heart and circulatory problems. The objective of this study was to examine the effect of moisture content, particle size of grape seeds, screw speed and die diameter of mechanical expeller on grape seed oil yield by using a single screw oil expeller. The optimum oil extraction conditions from whole grape seeds were 5.3% MC, 500 rpm and 10 mm die diameter, which resulted in grape seed oil yield of 7.6 %. The oil extraction rate was 0.57 kg h-1 and seed residence time was 8.6 s. The results proved the feasibility of extracting grape seed oil through the mechanical method as an alternative to solvent extraction.
Technical Abstract: In the United States, over 150 thousand metric tons of dried grape seeds containing 13-19% of oil are produced every year, as a byproduct from processing of about 5.8 million metric tons of grapes. The health promoting properties of grape seed oil is due to the presence of many bioactive components such as unsaturated fatty acids, antioxidants, and high-density lipoprotein. The chemical (hexane) extraction method is detrimental to these vital bioactive components and accelerates the oil oxidation process. The objectives of this study were to determine the effects moisture content (MC) and particle size of grape seeds, screw speed and die diameter of mechanical expeller on grape seed oil yield, and optimize the operating conditions of the expeller for maximum grape seed oil yield. Results showed that preheating of screw press with a ring heater to 60 °C almost eliminated the initial time lag to extract oil. Reducing the particle size by grinding of seeds did not significantly influence the oil yield, and hindered the extraction by clogging the feeding chute. Increasing screw speed from 140 to 500 rpm increased the filtered oil production rate from 0.20-0.57 kg h-1 at 10 mm die diameter and 5.3% seed moisture content, without significantly affecting the oil extraction percentage. Increasing the die diameter from 6 to 10 mm increased the oil production rate from 0.15 to 0.43 kg h-1 at 380 rpm for 5.3 % moisture seeds and decreased the filtered oil extraction percentage from 9.2 % to 7.3%. The seed moisture content in the range of 3.1% to 8.7% did not affect the oil yield; however, beyond 8.7% MC, oil yield was reduced significantly. Extracting whole grape seeds of 5.3% MC at 500 rpm using 10 mm die diameter was found to be the optimum condition which produced grape seed oil yield of 7.6 % at an oil extraction rate of 0.57 kg h-1 and seed residence time of 8.6 s.