Effects of de‐esterification treatment of lemon pectin on its stable capability against protein precipitation in acidified milk drinks

Abstract

AbstractIn this work, we extracted pectin from lemon peel and used pectin methyl‐esterase (PME) to obtain pectins with different degree of methyl esterification (DM). The effects of different de‐esterification treatments of lemon pectin (LP) on physicochemical properties, structural characteristics and its stable capability against protein precipitation in acidified milk drinks (AMDs) were systematically investigated. The results revealed that degree of methyl esterification (DM) decreased as the increasing of PME treatment time, whose DM values were 82.58%, 71.92%, 71.44%, 70.35%, 42.17%, and 32.54% for LP, LP‐E‐1, LP‐E‐2, LP‐E‐3, LP‐E‐4, and LP‐E‐5, respectively. There were no obvious differences in monosaccharide composition and molecular weight among the five fractions. The higher viscosities of LP‐E‐4 and LP‐E‐5 were probably attributed to the increase in zeta‐potential values and intrinsic viscosity, which would be explained by the removal of methoxy groups, resulting in stronger hydrogen bonds in solutions. Furthermore, LP‐E‐1, LP‐E‐2, and LP‐E‐3 had better AMDs stability against protein precipitation than LP, since they performed in better accelerated physical stability and storage stability, smaller particle size and lower Turbiscan stability index values. It suggested that PME de‐esterification on pectin could increase and concentrate its negative charges to wrap protein, while the remaining methoxy provides spatial resistance, both of which avoid protein precipitation.