Preparation of amidated pectins through enzymatic method: Structures, hydrogel properties and its application potential in fat substitutes.

In this paper, α-alanine and β-alanine were used as modifiers to prepare α-alanine amidated pectin (α-AP) and β-alanine amidated pectin (β-AP) through enzymatic method. The effects of alanine and its isomer on the amidation degree and physicochemical properties of pectin were studied. Fourier transform infrared spectrum, proton nuclear magnetic resonance analysis, X-ray photoelectron spectrum and elemental analysis indicated that the amino groups from α-C and β-C could be aminated with the carboxyl group of pectin to form the corresponding aminated pectin. The alanine grafting ratio of α-AP and β-AP were 21.99% and 18.92%, respectively. The results showed that the dynamic viscosity of β-AP was significantly higher than that of α-AP due to the influence of amino acid side chain. However, due to the higher alanine grafting ratio of α-AP, the strength of hydrogel prepared by α-AP was higher than that of β-AP, and it also has the highest elastic modulus and swelling capacity. In addition, pectin, as a carbohydrate-based fat substitute, has been widely used in the field of food to simulate the smooth and delicate taste of fat. Compared with High methoxy pectin (HMP) and β-AP, α-AP had better colloid stability and smaller hydrogel particles in the composite system. The results provide references for the application of amidated pectin in low-fat food.