基于介电常数和低场核磁共振技术的煎炸油品质分析

The quality analysis of frying palm oil based on dielectric constant and low-field nuclear magnetic

应用介电常数仪和低场核磁共振分析仪分别测定了150、180、210℃下煎炸棕榈油2～10h(每间隔2h取样)的介电常数和弛豫图谱。将介电常数(ε)结果与GC测定的相应游离脂肪酸含量变化相比较,将弛豫峰面积比例之比(S21/S22)与对应的油酸和棕榈酸比值(O/P)相比较,并进行相关性分析。结果表明,在三个高温的不同时间下,介电常数(ε)可以用于煎炸棕榈油的品质分析;弛豫时间T21、T22可以用来辨别棕榈油是否经过高温煎炸处理;在150、180℃下,S21/S22与O/P在不同时间下的变化趋势相似,呈显著正相关性(p<0.05,p<0.01),可以用于监测这两个温度下煎炸棕榈油劣变程度;在210℃下,S21/S22与O/P变化规律相差较大且无相关性。

The dielectric constant and relaxation spectrum of palm oil fried 2 ～ 10h（two hours interval）at 150,180,210℃ were measured by dielectric constant and low-field NMR.The comparison between the dielectric constant（ε）and the free fatty acids determining by GC was made,and the correlations between the ratio of relaxation peak area（S21/S22）and the ratio of oleic acid and palmitic acid（O/P）was made either.The results showed that：the degree of deterioration of palm oil could be monitored by the dielectric constant（ε）at 150,180,210℃ accurately.Relaxation time T21,T22 could be used to distinguish whether the palm oil was processed at high-temperature frying.At 150,180℃,the trend between S21/S22 and O/P was similar,the correlation of which was positive and significant（p〈0.05,p〈0.01）.So the S21/S22 could be used to analyze the quality of frying palm oil.At 210℃,there was no correlation and similar trend between S21/S22 and O/P.