Synthesis of Edible Vegetable Oils Enriched with Healthy 1,3‐Diglycerides Using Crude Glycerol and Homogeneous/Heterogeneous Catalysis

Quality Analysis of Peanut Oils and Peanut Diacylglycerol Edible Oils After Frying Using Raman Spectroscopy Combined with Oil Microscopy Method

BACKGROUND

The thermal stability and quality of fats change during oil-frying, directly impacting food safety and nutritional value; however, traditional analysis methods are time-consuming and complex.

OBJECTIVE

This study aimed to develop a rapid monitoring protocol using a portable Raman spectrometer for peanut oils and peanut diacylglycerol (DAG) edible oils after frying zero to five times at 150°C.

METHODS

Raman spectral data and the acid and peroxide values were determined for 48 oil test samples. Raman spectral data were analyzed using the characteristic band intensity ratio method and oil microscopy method.

RESULTS

The peroxide values of peanut oil correlated with I729/I1076, I1076/I1300, and I1268/I1655 (I: Raman spectral intensity; subscript: wave number corresponding to Raman shift), whereas the acid and peroxide values of peanut DAG edible oil correlated with I863/I1655, I1076/I1300, and I1268/I1655. Oil microscopy method analysis revealed that the fried peanut DAG oil had higher trans-fatty acid and acid values (AV) and lower unsaturated fatty AVs than regular peanut oil. Furthermore, oil microscopy method revealed changes in the functional groups of the oils and fats, further elucidating the quality changes that occur in oils and fats after frying.

CONCLUSION

Raman spectroscopy combined with oil microscopy method can be used to rapidly monitor the quality of frying oil after frying.

HIGHLIGHTS

Peanut DAG oil is more oxidatively stable after frying than peanut oil; a characteristic band intensity ratio method can be used to classify frying oils; the peroxide value of peanut oil is related to I729/I1076, I1076/I1300, and I1268/I1655; the acid and peroxide values of peanut DAG edible oil are related to I863/I1655, I1076/I1300, and I1268/I1655; oil microscopy method revealed oil functional group changes and could improve frying quality analysis.

Kinetics and Mechanism of Solvent Influence on the Lipase-Catalyzed 1,3-Diolein Synthesis

1,3-Diacylglycerol preparation has roused increasing attention in recent years as the 1,3-diacylglycerol-rich oils can suppress the deposition of visceral fat and prevent the body weight increasing. Lipozyme TL IM-mediated esterification of oleic acid with monoolein was effective for 1,3-diacylglycerol production. During the esterification process, the solvent shows obvious influence on the diolein synthesis as well as the 1,3-diolein production. This work investigated the related kinetics and mechanism of the solvent effect on the esterification and Lipozyme TL IM performance. The results indicated that both the esterification rate constant and the acyl migration rate constant positively correlated with the logP of the solvent, while the site specificity of lipase has negative correlation with solvent logP. The acylation toward the 2-position of 1-monoolein was more sensitive to the solvent logP compared to the 1-position of glycerides. Molecular dynamics simulation revealed that solvents with different logP influenced the structure of Lipozyme TL IM including RMSD, hydrogen bond, and radial distribution function to a large extent, which subsequently led to the catalytic activity and selectivity variation of the lipase.