A method based on 1H NMR spectral data useful to evaluate the hydrolysis level in complex lipid mixtures

A new approach is reported, based on Proton Nuclear Magnetic Resonance (1H NMR) spectral data, to study qualitatively and quantitatively the hydrolysis level in complex lipid mixtures. It is based on a detailed study of the spectra of tri-, di-, mono-glycerides and fatty acids. It has been validated by using mixtures of standard compounds which simulate the complex mixtures formed in lipid digestion. To this aim the 1H NMR spectra of pure compounds, as well as of mixtures containing different known proportions of triglycerides, 1,2-diglycerides, 1,3-diglycerides, 1-monoglycerides, 2-monoglycerides and fatty acids, were acquired. These mixtures cover a very broad range of concentrations and simulate edible oils and fats of vegetable and animal origins, including fish, with different levels of hydrolysis. Equations based on spectral data are proposed to determine the molar percentage of the different kinds of compounds that may be formed in lipid digestion, thus allowing quantification of the advance of lipolysis. To the best of our knowledge, this is the first time that a method based on 1H NMR spectral data to quantify triglycerides, as well as partial glycerides and fatty acids in complex lipid mixtures coming from lipolysis is proposed. This methodology offers many advantages and is useful not only in the fields of food technology and nutrition, but also in others like enzymology, pharmacology, medicine and petrochemistry, among others.This work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, AGL2012-36466), by the Basque Government (EJ-GV, GIC10/85-IT-463-10) and by the Unit for Education and Research “Food Quality and Safety” (UPV/EHU-UFI-11/21). B. N-E. thanks to the UPV/EHU for a predoctoral fellowship

Usefulness of 1H NMR in assessing the extent of lipid digestion

Proton Nuclear Magnetic Resonance (1H NMR) is proved to be, for the first time, a very useful technique in monitoring the extent of lipid hydrolysis in digestion processes. Sunflower oil and minced fish flesh, as model foods, were subjected to different in vitro digestion experiments and the lipolysis levels reached were evaluated using 1H NMR spectral data. Simple observation of the spectra gives very valuable information about the extent of the lipolysis and enables a rapid discrimination among samples having different hydrolysis degree. Equations were developed to quantify all the lipolytic products, and either referred to acyl groups plus fatty acids, or to glyceryl structures. The main hydrolysis products were 1,2-diglycerides, 2-monoglycerides, glycerol and fatty acids, although small proportions of 1,3-diglycerides and of 1-monoglycerides were also found. With this methodology, determination of the extent of lipid digestion in its different definitions can be made. It has been shown that these definitions are not equivalent, which is evidence for the need for a consensus in this regard.This work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, AGL2012-36466), by the Basque Government (EJ-GV, GIC10/85-IT-463-10) and by the Unit for Education and Research “Food Quality and Safety” (UPV/EHU-UFI-11/21). All authors participate in the COST Action FA1005 INFOGEST. B. N-E. thanks the UPV/EHU for a predoctoral fellowship