| Glycidyl fatty acid esters(GEs) is the esterification products of glycerol and fatty acids. It’s mainly produced in the deodorization process of oil refining and exsited in a wide variety of refined vegetable oils and grease products. GEs which exists in edible oils and fats are more likely in the formation of esters, the glycerol it produced in lipid metabolism is genetic toxicity of carcinogens. At the same time, GEs is also an important precursor of 3-chloro-1,2-propanediol(3-MCPD). Glycerol is easily to transform into 3-MCPD in the presence of hydrochloric acid. In a word, GEs has caused wide public attention. In this paper, firstly, we established the method which using gas chromatography- mass spectrometry(GC-MS) to detect GEs in edible oils and fats. Secondly, some important factors which have great influences on the formation of GEs have been studied. Finally, a way to remove GEs after refining by adsorbent materials was studied. The main results were as follows:Firstly, an improved analysis method for the determination of GEs in edible oils has been established. The results showed that the most suitable transesterification time and temperature were 4~5 min and 20~30 ℃ with sodium methoxide. The optimal derivatization reagent amounts was 200 μL, the optimal derivatization time and temperature were 20 min and 30 ℃with phenylboronic acid(PBA). The limit of detection(LOD) and the limit of quantification(LOQ) were 10.00 and 35.60 μg/kg, respectively, the recovery rate was 91.02 %~100.17 %, and its relative standard deviation(RSD) was 2.16%~5.87%. The results showed that the features of analysis method were excellent in qualitative and quantitative accuracy,it had high sensitivity and good reproducibility, so it could meet the demands of further detection and analysis of GEs in edible oils.Secondly, some important factors which have great influences on the formation of GEs have been studied. In this way, the effect of oil type, amounts of diacylglycerol, oil refining processes, heating conditions and storage conditions on GEs were examined by GC-MS. The results showed that all those factors had significant influences on GEs. There is a widespread of GEs pollution in refined vegetable oils, the detection rate was as high as 96.55%, and the range was about 0.248 ~ 4.231 mg/kg, including palm oil content as high as 3.770 mg/kg and rice oil was 4.231 mg/kg. The study also found that the amounts of GEs had a positive correlation with diacylglycerol(R2=0.7649),which means diacylglycerol was one of the precursors of GEs’ formation. Besides, deodorization was the most important process to generate GEs during refining processes, after deodorization, the amounts of GEs in palm oil was 3.946mg/kg. The effect of heating temperature and time showed that when heating temperature was changing between 120 and 200 ℃, it had no significant influence on GEs, while the temperature increased to 260 ℃, GEs contents could increase to 9.912 mg/kg and then decreased.Finally, a way to remove GEs after refining by adsorbent materials was studied. The results showed that all the adsorbent materials chose for the study had a positive effects on the removal of GEs. Among these, AC1 had the best adsorption capacity, GEs contents was decreased from 3.770 mg/kg to 0.150 mg/kg after the treatment with AC1, its adsorbent rate was 95.92 %. Adsorbent conditions also had great influences on adsorption efficiency, the most suitable amounts of adsorbent was 1~5 %, the optimal absorption time and temperature were 30 min and 80~100 ℃. The results also showed that there were no adverse effects but even a slight improvement of oil quality after treatment with choosing adsorbent, the induction time of palm oil treated with AC1 was increased to 19.35 h. In the end, using adsorption kinetics to study the absorption mechanism of AC1 and KD, the two materials all met the pseudo-second-order kinetics, describing the the adsorption rate was relation with chemical adsorption. |
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