Kinetics of soybean oil extraction

OTERO NOELY; BAÜMLER, ERICA; CARELLI, AMALIA; CARRIN, M.E.

Córdoba

Congreso; VI Congreso Internacional de Ciencia y Tecnología de los Alimentos; 2016

Ministerio de Ciencia y Tecnología de la provincia de Córdoba

In the conventional oil extraction process from soybeans, hexane is the solvent mostextensivelyused because of its low cost and high solubilizing power. However, its substitution byalternative solvents such as ethanol is of great interest because hexane comes from non-renewablefossil resources and it is highly flammable. There are a lot of published works about the soybean oilextraction using ethanol. However, the majority of them did not take into account its lowerselectivity towards triglycerides in comparison with hexane extraction. As a result, the availableinformation about oil (principally triacylglycerols) yield is not completely accurate and, moreover,the knowledge about other compounds extracted during the oil extracting process is limited. Inorder to evaluate the feasibility of using ethanol to extract soybean oil is mandatory to know the realoil (triacylglycerols) yield. So, it is necessary to know the composition of the extract obtained afterthe extraction process. The aim of this work was to perform soybean oil extraction tests usingethanol as solvent, evaluate the oil quality in terms of tocols and phospholipids composition, andcompare these results with those using hexane. The extraction assays were carried out in a batchsystem at 60ºC and using a solid (soybean collets):solvent ratio of 1:10 (w/v). The miscella obtainedafter each extraction contained the total extracted material. So, it was fractionated in oil (hexanesolublefraction) and other compounds (hexane-insoluble fraction) to determine the actual oilextraction yields. The results obtained, for both solvents used, showed a first step with higherextraction rate corresponding to the washing step. Moreover, it was found that hexane providedsimilar yield of total extracted material yield, but higher oil yield than ethanol (24.76 ± 0.47% and22.86 ± 0.27% d.b., respectively at 960 min, equilibrium condition). On the other hand, ethanolshowed more ability than hexane to extract phospholipids, being phosphatidylcholine andphosphatidic acid the major components, respectively. It was observed, in both cases, that therelative percentage of the major phospholipid stayed constant over time. In the case of tocols, both,the total content and their relative percentage did not show significant differences among solvents atinfinite time (p>0.07). However, their extraction using ethanol happened more quickly. The tocolsamount extracted at 90 min did not show significant differences with that at 960 min (p>0.1), beingthe major component γ-tocopherol. It can be concluded that although hexane resulted in higher oilyield from soybean collets, ethanol was also effective in the soybean oil extraction. Furthermore,ethanol was able to remove higher amount of phospholipids. So, the soybean meal obtained afterthat extraction could be considered with a better quality to be use as source of protein, not onlybecause it was not in contact with hexane, but also because it was more concentrated.