低场核磁共振法快速检测炸油质量

Application of Low Field Nuclear Magnetic Resonance on Rapid Determination of Frying Oil Quality

由于在高温油炸过程中的快速劣变,市场上油炸用油的质量问题日益受到人们的关注.为了研究低场核磁共振技术在市场上复杂油炸条件下的油炸用油质量快速检测中的表现,从上海市10个行政区的市场上共采集油炸用油样品107个,包括大豆油96个,起酥油11个.通过测定油样的极性组分和黏度,发现6个(占总样品数5.6%)油样的极性组分超过国家标准,说明市场上油炸用油存在一定的安全问题.通过线性分析发现极性组分和黏度之间的线性关系良好,R2为0.892,除去样品中11个起酥油后R2则达到0.927.用低场核磁共振仪测定各油样后,通过对多组分T2弛豫图谱中T21峰面积(S21)比例的分析发现,S21比例与极性组分和黏度呈现良好的相关性,R2值分别为0.860和0.840,除去油样中的起酥油后R2值略有上升,分别达到0.865和0.854.这说明可以利用低场核磁共振技术达到快速检测市场上油炸用油品质的目的.

There has been growing concern about the frying oil quality due to its remarkable deterioration during the frying process. To investigate the performance of LF-NMR in the rapid determination of frying oil from various frying conditions, deep frying oil samples （n = 107） including 96 soy bean oil samples and 11 shortening samples were collected from street vendors in 10 districts of Shanghai. Total polar compounds （TPC） and viscosity of the oil samples were determined. TPC values of 6 oil samples （5.6% of all the oil samples） were above the national standard for frying oil, indicating the quality problem of frying oil from the street vendors. The linear analysis showed a good linear relationship （R^2 = 0.89：2） between TPC and viscosity, while R^2 was 0. 927 after the removal of shortening samples. After the analysis of the ratio of T2, areas （ S21 ） in transverse relaxation （ T2 ） spectra, the good correlations between S21 and TPC, S21 and viscosity were obtained, R2 was 0. 860 and 0. 840, respectively. After removing the shortening samples, R2 slightly increased to 0. 865 and 0. 854. The results demonstrate that LF-NMR has the potential to rapidly evaluate the quality of deep frying oil.