Control Of Polycyclic Aromatic Hydrocarbons(PAHs) In The Processing Of Roasted Fragrant Oil

Polycyclic aromatic hydrocarbons(PAHs) are ubiquitous in nature and widely present in atmosphere, water, food, plants and animals. According to the number of benzene ring in the compounds, PAHs can be divided into two categories: light polycyclic aromatic hydrocarbons(LPAHs), heavy polycyclic aromatic hydrocarbons(HPAHs).The EU made a more comprehensive and stringent requirement: the content of Ba P in edible vegetable oil(except cocoa butter and coconut oil) shall not exceed 2 μg/kg, while the sum of four PAHs(benzo[a]pyrene, benzo[a]anthracene, benzo[a]fluoranthene and chrysene, referred PAH4) shall not exceed 10 μg/kg. The aim of this article is to improve the detection method of GB/T 23213-2008 "Determination of polycyclic aromatic hydrocarbons in vegetable oils–GC-MS method" to be more accurate and simple, gave a simple statistical analysis of the PAHs contents in the vegetable oils and oilseeds; to measure the PAHs content of the roasted fragrant oil in roasting and frying procedures, and remove the PAHs effectively, ensuring the flavor and nutrients at the same time; to establish the sufficient removal techniques of PAHs by bleaching and deodorization in the solvent extracted oil processed by "pre-press-leaching".The purpose is to make a feasible technical support for the roasted oil.(a)A methord for the analysis of EPA16 PAHs in edible oil and oilseeds samples by isotope dilution gas chromatography-mass spectrometry(GC-MS) was built. The calibration curves had good linearity within 1~100 μg/kg for each pesticide(0.9999>R>0.9989). The limits of the detection ranged from 0.06 μg/kg to 0.17 μg/kg and the limits of quantitation ranged from 0.18 μg/kg to 0.56 μg/kg. The recoveries of 16 PAHs varied from 84.26% to 115.31% with the relative standard deviation of 0.12%~10.36%(n=6)at the spiked levels 2,5,10 μg/kg. The concentrations of Ba P and PAH4 were ranged from 0.24 to 24.69 μg/kg、1.11~112.72 μg/kg in the 21 tested oil samples. The concentrations of Ba P were lower than the limitation level of GB 2716-2005, and the qualification rate of Ba P was 85.71%. The qualification rates of Ba P and PAH4 were76.20% and 71.43% according to the EU No 835/2011 limits. The concentrations of Ba P and PAH4 in the dense fragrant oil were higher than the limitation level of EU, it is serious polluted than the ordinary oils. The concentrations of Ba P and PAH4 were ranged from 1.37 to 19.39 μg/kg, 0.10~2.50 μg/kg in the 21 tested oilseed samples, it was generally low than the oil samples. The contribution rate of HPAHs and PAH4 to the total concentrations of PAH16 were 0.46%~4.5%, 0.55~6.91%. Nph and Phe were the biggest pollution, and had a contribution rate of 14.92%~55.77%, 18.31%~44.11% to the the total concentration of PAH16.(b)Roasting is the key for the roasted fragrant oil, but also it is the way of PAHs and other harmful substances generated. So it is very important to study the changes of PAHs in the roasting process. By roasting the sunflower seed kernels and rapeseed seeds, we found that: With the increase of roasting temperature, roasting time, the content of Bap and PAH4 in the sunflower seed kernels and rapeseed seeds were showing an upward trend, the roasted conditions on the content of PAHs had a greater impact than rapeseed. Considering the limit provisions of Ba P and PAH4. EU. The color and the flavor of roasted oil,recommend reasonable roasted sunflower seed kernels and rapeseed temperature did not exceed 160 ℃, the roasted time of sunflower was no more than 30 min, and the rapeseed was no more than 40 min. At a temperature of 160 ℃, 30 min, the content of Bap, PAH4 in sunflower seeds was from 0.15, 2.79 μg/kg increasing to 0.64, 8.01 μg/kg, and that in in rapeseed was from 0.15,5.80 μg/kg increasing to 0.78, 8.30 μg/kg. The Bap and PAH4 content did not exceed the EU limit of No 835/2011, The content of LPAHs was much larger than HPAHs.(c) The research of high efficiency removal of PAHs in the roasted fragrant oil, without losing its flavor and less loss of nutrients were stuided. The effect of the adsorbent for the removal of PAHs were Norit activated carbon> WY activated carbon> activated clay; The activated clay had the stronger ability on flavor remove, and an excess of activated clay would make the oil more peculiar smell; Adsorption experiments had little influence on the fatty acid composition; Different adsorbents had significantly different effect on the removal of VE, the activated clay retained had the better and the Norit activated carbon had the worst ability on retaining VE and sterol.The optimal conditions were:0.3% dosage of the Norit activated carbon, adsorption time was 25 min, adsorption temperature was 110 ℃. In this condition, the removal rates of Ba P、 PAH4、HPAHs、LPAHs and PAH16 were 99.57%, 95.25%, 97.14%, 80.64% and 82.62%, respectively. The loss rate of VE was 22.08%, sterol was 32.92%, the score of flavor was 8.17. If just meet the criterion of Ba P and PAH4 that set by EU, we could select another conditions: 0.05% dosage of the Norit activated carbon. In this condition, the residue of Ba P and PAH4 were 0.37,5.12 μg/kg,respectively. The loss rate of VE was 7.31%, sterol was 11.63%, the score of flavor was 8.50.(d)The effects of mixed adsorbent(consisting of activated clay and WY activated carbon) on the removal of PAH16 and color for the extraction oil were studied. The purpose was to get the PAH16 removed, the color in the crude oil was removed, at the same time. Considering the effect of the Ba P, PAH4, HPAHs, LPAHs, PAH16 removal and the bleaching rate, the optimal removal conditions were that: 3%+1% dosage of the mixed adsorbent, adsorption time was 35 min, adsorption temperature was 110 ℃.In this conditions, the residue of Ba P, PAH4, HPAHs, LPAHs, PAH16 were 0.02, 2.09, 0.83, 42.18 and 43.01 μg/kg, the removal rates were 99.88%, 95.49%, 97.63%, 83.63%, 85.71% and 79.43%, respectively. Lovibond values Y was 15, R was 0.1, the index of color reached the first grade of sunflower oil; If just meet the criterion of Ba P and PAH4 that set by EU, the selected conditions were that:2%+0.2% dosage of the mixed adsorbent, adsorption time was 35 min, adsorption temperature was 110 ℃. In this condition, the residue of Ba P and PAH4 were 0.15, 2.25 μg/kg. Lovibond values Y was 15, R was 1.2.(e)The influences of deodorization process on PAHs in edible oils was studied. With the deodorization temperature rises and the removal time increase, the removal efficiency of PAHs was better. Under the experimental conditions(the temperature was 260 ℃, the time was 120 min), the concentrations of Ba P, PAH4, HPAHs, LPAHs and PAH16 were decreased to 1.21, 8.28, 16.62, 23.83, 40.44 μg/kg, respectively, and the removal rates were 89.64%、86.36%, 69.94%, 92.39%, 89.02%. The removal of LPAHs was better than HPAHs.The content of TFA was 3.25%, and the loss rate of VE was 35.01%. At the deodorized condition of 260 ℃ and 60 min, the Ba P content could get the limit of GB level. But to get the limit of EU, it required extend the deodorizing time to 120 min, at that time, the TFA content increased and the VE content reduced,greatly.