Biosynthesis of amidated pectins with ultra-high viscosity and low gelation restriction through ultra-low temperature enzymatic method

Abstract

In traditional industry, amidated pectin was usually prepared by adding ammonia gas under the alkaline condition or ethanol system which degrades the galacturonic acid chain of pectin and weakens the advantage of amidated pectin in gel. In this study, amidated pectin with ultra-high viscosity and low gelation restriction were prepared by grafting with the neutral aliphatic amino acids through enzymatic method at ultra-low temperature to extend the application of the pectin in food, daily use chemical, medicine and other fields. The amino acid grafting ratio of alanine amidated pectin (V-PE), valine amidated pectin (A-PE) and leucine amidated pectin (L-PE) were 14.12%, 24.36% and 18.94%, respectively. The results of dynamic viscosity showed that the dynamic viscosity of high methoxy pectin (HMP) increased from 186 to 39799 (V-PE), 20396 (A-PE) and 23781 mPa.s (L-PE), respectively. Through ultra-low temperature enzymatic, the V-PE with the highest amino acid grafting ratio had the highest solution viscosity and gel hardness. Furthermore, the hydrogel has better thermal stability, which can maintain the three-dimensional network structure of the gel at higher temperatures without collapse. Amidated pectin with ultra-high viscosity and low gelation restriction can provide valuable information in applications such as food and medicine. • Pectin was amidated by neutral aliphatic amino acids through enzymatic method. • In the two-phase system, the amide synthase activity of papain was dominant. • The amidated pectin can form hydrogels under low gelation restriction. • Compared with high methoxy pectin, amidated pectin has high dynamic viscosity.