Study On Potassium Carbonate-Glycerol Catalyzed Interesterification Of Oils And Fats

Chemical interesterification（CIE）is an innovative method for the modification of fats and oils.In this study,glycerol（G）-potassium carbonate（K₂CO₃）deep eutectic solvent（DES）was used as a catalyst for catalytic interesterification of oils and fats,and the properties of modified fats and oils were evaluated.Firstly,the DES was structurally characterized and used to catalyze the interesterification of lard（LR）to study its catalytic effect and mechanism.The effect of reaction conditions on G-K₂CO₃ DES catalyzed lard interesterification was investigated,as that of the interesterification degrees（IDs）on the physicochemical properties of lard.Then,the catalyst was utilized for the catalytic interesterification of palm stearin（PS）to high oleic acid sunflower oil（HOSO）.The study also used interesterified lard and PS-HOSO for cake making to evaluate the influence of interesterification on their application properties.The results of the study would provide a theoretical reference for the application research of chemical interesterification and modification of oils and fats.A series of deep eutectic solvents were synthesized from potassium carbonate and glycerol,and their chemical structure and hydrogen-bonding interactions therein were confirmed by FTIR and ¹H NMR.Compared with K₂CO₃,simplified K₂CO₃ and glycerol（K+G）and sodium methylate,the synthesized DES exhibited excellent catalytic activity of interesterification of lard.Moreover,the high efficiency of G-K₂CO₃ DES is mainly due to the activation of hydroxyl groups by carbonate ion,and the activated hydroxyl oxygen is more favorable to attack the positive carbon of carbonyl group coordinated with K⁺.Combined with the analysis of glycerides content and fatty acid composition,it was found that the DES was effective in catalyzing the interesterification of oils and fats.The G-K₂CO₃ deep eutectic solvents were used to catalyze the interesterification of lard,and the suitable process conditions were investigated by one-factor experiments:temperature of 120℃,time of 60 min,addition amount of 2%,and catalyst ratio of 3:1（G:K₂CO₃,mol:mol）;under these conditions,the IDs could reach more than 80%.The interesterification degrees had implications on the properties of lard.As IDs increased,the fatty acids composition of lards was almost unchanged;however FAs at Sn-2 position significantly changed,free FAs（FFAs）and monoacylglycerols（MAGs）in modified lards increased slightly,diacylglycerols（DAGs）raised,and triacylglycerols（TAGs）decreased,trisaturated triacylglycerols and triunsaturated triacylglycerols increased gradually.Compared with LR,modified lards had relatively flatter solid fat content（SFC）curves.Modified lards with higher IDs（over 50%）had higher slip melting points（SMPs）and distinctive thermal property.The polymorphism of lards transformed fromβ-form toβ′-form with IDs increase,but the stacking pattern of crystals was unchanged.The micromorphology of interesterified lards were much finer.The crystallization behaviors of modified lards at 20℃were affected by IDs and different distinctly from that of original lard.The results showed that the interesterified lards with higher IDs（over 50%）were more suitable as shortenings in comparison with original lard.Lard was used in cake baking experiments,and the results verified that lard with higher IDs could give the cake a fluffier texture and delicate taste with better crispness.The G-K₂CO₃ deep eutectic solvents were used to catalyze the interesterification of PS-HOSO,the results showed that the saturated FAs content increased significantly with the increase of PS ratio and CIE hardly changed the FAs composition and content.The SSS and UUU TAGs content decreased significantly,the UUS and USS TAGs content increased significantly after interesterification,while new TAG species were generated,which led to a significant decrease in SMPs and SFCs and a shift in the plasticity range toward lower temperatures,along with similar changes in melting and crystallization properties.The content of FFAs,MAGs and DAGs increased while TAGs content decreased after interesterification.The physical mixtures of PS-HOSO were composed of large spherical crystals aggregated by closely arranged needle-like crystals,which exhibited a predominantlyβ′-form.After CIE,they microscopic morphology consisted of a structure of fine and dense needle-like,short rod-like or small spherical crystals,which showed a predominantlyβ-form.The stacking pattern of the PS-HOSO mixture crystals all exhibited double chain that did not change before and after interesterification.The shortening properties of the modified blends were improved and gave the cake product a fine texture.