Effects of raw material and oil production technology on phthalatic acid esters content in peanut oil

Abstract: Phthalatic acid esters (PAEs) are one of the major risk components in edible vegetable oil. Peanut is the advantageous oil crop in China, and its output ranks the forefront in the world. Peanut oil is also the traditional high-end edible oil, and especially the majority of consumers enjoy the fragrant peanut oil because of its unique flavor. However, the study on the content of PAEs in peanut and its effect on the content of PAEs in peanut oil was very scarce. In this paper, the peanut raw material in different peanut producing areas was collected and peeled, and the contents of PAEs in peanut kernel, peanut coat and peeled peanut kernel were measured respectively. Then the peanut crude oils were obtained from peanut kernel or peeled peanut kernel by solvent extraction or pressing. The content of PAEs in peanut raw material and its corresponding crude oil were tested and analyzed, and in addition, the effects of raw material quality and oil production on the content of PAEs in peanut crude oil were explored. The results showed that PAEs were determined in all peanut materials, nevertheless, the distribution of PAEs in peanut was uneven, and the PAEs content in peanut coat was significantly higher than that in its corresponding peeled kernel and whole oilseed. The contents of dibutyl phthalate (DBP), di (2-ethtlhexyl) phthalate (DEHP), diisononyl ortho-phthalate (DINP) and the total content of 8 PAEs (Σ8PAEs) in 7 peanut samples were 0.085-0.540, 0.325-1.372, 0.422-0.771 and 0.964-3.403 mg/kg, respectively, while the Σ8PAEs content in peanut coat was 1.15-19.21 times that of peanut kernel. The PAEs in peanut would migrate and be enriched in crude oils during the process of oil production, what was more, the PAEs contents in peanut crude oil were different with different peanut raw material and processing techniques. The migration rate of the PAEs in solvent-extracted crude oil was greater than that of the pressed crude oil. For example, the average contents of DBP, DEHP, DINP and Σ8PAEs in peanut solvent-extracted crude oils were 1.39, 1.23, 1.16, and 1.22 times that of the pressed crude oils, respectively. For crude oil obtained from peanuts after peeling, the exposure risk of PAEs was lower than the oil obtained from peanut without peeling. For example, the contents of DBP, DEHP, DINP and Σ8PAEs in peeled peanut kernel crude oil could be reduced by 33.0%-36.4%, 26.7%-29.4%, 15.0%-18.7% and 22.5%-23.0%, respectively. All in all, the quality of peanut raw material from different origins was quite different, the PAEs content in crude oil was significantly different under different oil production processes, and the solvent-extracted oil had higher degree of risk of PAEs pollution than the oil obtained by pressing. The oil obtained from peanut after peeling could reduce the PAEs content in crude oil, reducing the exposure risk of PAEs in crude oil. In the production of peanut oil, especially for the roasted fragrant peanut oil production, the contents of PAEs in peanut kernels should be strictly controlled by using peeled peanuts and pressing technique to produce crude oil, which is important for the prevention and control of PAEs in peanut oil products.