Quantitative analysis of partial acylglycerols and free fatty acids in palm oil by 13 C nuclear magnetic resonance spectroscopy

Investigation of lipolytic activity of the red king crab hepatopancreas homogenate by NMR spectroscopy

The digestive gland of craboids (hepatopancreas) is rich in a huge number of various enzymes (collagenases, nucleases, hyaluronidases, proteases), which are well studied at the moment. However, little is known about crustacean lipases. In this work, using ¹H NMR spectroscopy, it was found that the hepatopancreas homogenate of the red king crab Paralithodes camtschaticus demonstrates high lipolytic activity against triacetin in a wide pH range and shows moderate activity against the caprylic/capric triglyceride emulsion. Under the action of the hepatopancreas homogenate, triacylglycerols are converted into 1,2-diacylglycerol, and then into 2-monoacylglycerol and 1-monoacylglycerol. The 1-monoacylglycerol predominates in the reaction products. The use of NMR spectroscopy makes it possible to quickly detect hydrolysis products and evaluate the reaction direction.

When detection of dairy food fraud fails: An alternative approach through proton nuclear magnetic resonance spectroscopy

This paper investigated the limits of the current approach for the determination of the fatty acids profile of milk fats from proton nuclear magnetic resonance data based on the hypothesis that the signal at 0.96 ppm, currently assigned in the literature as a marker for the "short chain fatty acids," is generated only by the butyric moiety (not by all of the short-chain fatty acids, which also include C6:0-caproic acid). The hypothesis was tested and experimentally confirmed. Moreover, the triplet at 0.96 ppm can also be due to n-3 fatty acids such as linolenic acid (C18:3); therefore, a previously reported methodology for the fatty acids profiling of dairy products-considered as general in the literature-cannot be used in fraud-detection approaches because it allows linolenic acid to be mistaken for butyric acid, consequently leading to misclassification of adulterated samples as nonadulterated. To support our opinion, we have applied the current literature approach for the determination of the fatty acids composition of 3 synthetic nondairy fat blends and have obtained fatty acid compositions similar to milk fats, allowing for their misclassification as genuine milk fats. However, in reality, the blends had very different compositions, as confirmed by gas chromatography. Consequently, we have highlighted the weaknesses of the existing methodology for the detection of dairy food adulteration. In return, new proton nuclear magnetic resonance descriptors based on various integral ratios of signals associated with CH₂ moiety versus signals associated with butyric and n-3 fatty acids were proposed to detect adulterations.

NMR Determination of Free Fatty Acids in Vegetable Oils

The identification and quantification of free fatty acids (FFA) in edible and non-edible vegetable oils, including waste cooking oils, is a crucial index to assess their quality and drives their use in different application fields. NMR spectroscopy represents an alternative tool to conventional methods for the determination of FFA content, providing us with interesting advantages. Here the approaches reported in the literature based on 1H, 13C and 31P NMR are illustrated and compared, highlighting the pros and cons of the suggested strategies.

High Resolution NMR Spectroscopy as a Structural and Analytical Tool for Unsaturated Lipids in Solution

Mono- and polyunsaturated lipids are widely distributed in Nature, and are structurally and functionally a diverse class of molecules with a variety of physicochemical, biological, medicinal and nutritional properties. High resolution NMR spectroscopic techniques including 1H-, 13C- and 31P-NMR have been successfully employed as a structural and analytical tool for unsaturated lipids. The objective of this review article is to provide: (i) an overview of the critical 1H-, 13C- and 31P-NMR parameters for structural and analytical investigations; (ii) an overview of various 1D and 2D NMR techniques that have been used for resonance assignments; (iii) selected analytical and structural studies with emphasis in the identification of major and minor unsaturated fatty acids in complex lipid extracts without the need for the isolation of the individual components; (iv) selected investigations of oxidation products of lipids; (v) applications in the emerging field of lipidomics; (vi) studies of protein-lipid interactions at a molecular level; (vii) practical considerations and (viii) an overview of future developments in the field.

Length-scale Specific Crystalline Structural Changes Induced by Molecular Randomization of Pequi Oil

Pequi fruit (Caryocar brasiliense Camb) is considered important since its pulp has a high content of oil and carotenoids. The oil's triacylglycerols (TAGs) contain mainly oleic (~57%) and palmitic (~36%) fatty acids, distributed primarily among POO, POP/PPO, and OOO TAGs. It displays a tendency to fractionate upon storage and has a relatively low melting temperature (SFC of 4% at 25°C). Pequi oil was modified through chemical interesterification, which increased the PPP content to ~6%. This caused a flattening in the SFC-temperature profile, raising the end of melt temperature significantly (SFC of 4% at 39°C). The interesterified oil does not fractionate and is thermally stable up to 40°C, with an SFC-temperature profile resembling that of roll-in shortening (SFC of 31% at 16°C) despite containing high amounts of oleic acid. Crystallization and melting behavior changed. Crystal packing became more disorganized as evidenced by a significant decrease in crystalline domain size in the [001] direction from 42.3 nm to 32.1 nm. Polymorphism remained of the triclinic (β) subcell type but polytypism changed from the 3L to the 2L type. Polarized light microscopy demonstrated that interesterification dramatically decreased crystal size, consistent with a higher rate of nucleation in the material. Moreover, the dramatic improvement in physical stability and functionality was not accompanied by a significant decrease in total carotenoid content (~390 mg/kg).

Enzymatic catalyzed palm oil hydrolysis under ultrasound irradiation: diacylglycerol synthesis

Diacylglycerol (DAG) rich oils have an organoleptic property like that of regular edible oils, but these oils do not tend to be accumulated as fat. Palm oil ranks first in the world in terms of edible oil production owing to its low cost. The aim of this study was to propose a new methodology to produce diacylglycerol by hydrolysis of palm oil using Lipozyme RM IM commercial lipase as a catalyst under ultrasound irradiation. The reactions were carried out at 55 °C with two different methods. First, the reaction system was exposed to ultrasonic waves for the whole reaction time, which led to enzymatic inactivation and water evaporation. Ultrasound was then used to promote emulsification of the water/oil system before the hydrolysis reaction, avoiding contact between the probe and the enzymes. An experimental design was used to optimize the ultrasound-related parameters and maximize the hydrolysis rate, and in these conditions, with a change in equilibrium, DAG production was evaluated. Better reaction conditions were achieved for the second method: 11.20 wt.% (water+oil mass) water content, 1.36 wt.% (water+oil mass) enzyme load, 12 h of reaction time, 1.2 min and 200 W of exposure to ultrasound. In these conditions diacylglycerol yield was 34.17 wt.%.

Determination of free fatty acids in pharmaceutical lipids by ¹H NMR and comparison with the classical acid value

Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. (1)H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new (1)H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this (1)H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The (1)H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed.

13C NMR quantification of mono and diacylglycerols obtained through the solvent-free lipase-catalyzed esterification of saturated fatty acids

In the present investigation, we studied the enzymatic synthesis of monoacylglycerols (MAG) and diacylglycerols (DAG) via the esterification of saturated fatty acids (stearic, palmitic and an industrial residue containing 87% palmitic acid) and glycerol in a solvent-free system. Three immobilized lipases (Lipozyme RM IM, Lipozyme TL IM and Novozym 435) and different reaction conditions were evaluated. Under the optimal reaction conditions, esterifications catalyzed by Lipozyme RM IM resulted in a mixture of MAG and DAG at high conversion rates for all of the substrates. In addition, except for the reaction of industrial residue at atmospheric pressure, all of these products met the World Health Organization and European Union directives for acylglycerol mixtures for use in food applications. The products were quantified by (13)C NMR, with the aid of an external reference signal which was generated from a sealed coaxial tube filled with acetonitrile-d3. After calibrating the area of this signal using the classical external reference method, the same coaxial tube was used repeatedly to quantify the reaction products.