Spyros Apostolos, Philippidis Angelos, Dais Photis
NMR Laboratory, Department of Chemistry, University of Crete, 71409 Iraklion, Crete, Greece.
J Agric Food Chem. 2004 Jan 28;52(2):157-64. doi: 10.1021/jf030586j.
Diacylglycerol isomers and free acidity were determined for five extra virgin olive oils of different initial acidities by employing a facile (31)P NMR methodology as a function of storage time and storage conditions. The kinetic treatment of the hydrolysis of triacylglycerols (TGs) and the isomerization of 1,2-diacylglycerols (1,2-DGs) to 1,3-diacylglycerols (1,3-DGs) during storage of 18 months at ambient temperature in the dark and light and at 5 degrees C in the dark showed that the isomerization is strongly dependent on the rate of the TGs hydrolysis, the initial free acidity (H(0)) of the virgin olive oil samples, and storage conditions. Although the time-evolution of the diacylglycerols (DGs) depends on the TGs hydrolysis, the ratio D of the concentration of 1,2-DGs to the total amount of DGs was found to be independent of this factor. From the kinetic expression of the ratio D, a quantitative measure was formulated that allows the estimation of the storage time or age of virgin olive oils. Application of this quantitative measure to several olive oil samples of known and unknown storage history resulted in a very good agreement with respect to the actual storage time for up to 10-12 months of storage. For a longer storage period, where the isomerization of DGs is close to its equilibrium state, the calculated age index is only indicative.
采用简便的（31）P NMR方法，测定了五种初始酸度不同的特级初榨橄榄油中甘油二酯异构体和游离酸度随储存时间和储存条件的变化。在黑暗和光照条件下于室温以及在黑暗中于5摄氏度储存18个月期间，对三酰甘油（TGs）水解以及1,2 - 二酰甘油（1,2 - DGs）异构化为1,3 - 二酰甘油（1,3 - DGs）的动力学处理表明，异构化强烈依赖于TGs水解速率、初榨橄榄油样品的初始游离酸度（H(0)）以及储存条件。尽管甘油二酯（DGs）的时间演变取决于TGs水解，但发现1,2 - DGs浓度与DGs总量的比值D与该因素无关。根据比值D的动力学表达式，制定了一种定量方法，可用于估算初榨橄榄油的储存时间或陈化时间。将该定量方法应用于几个已知和未知储存历史的橄榄油样品，在长达10 - 12个月的储存期内，与实际储存时间非常吻合。对于更长的储存期，此时DGs的异构化接近其平衡状态，计算出的陈化指数仅具有指示性。
