Effect of cross-linking on the resistance to enzymatic hydrolysis of waxy maize starch and low-methoxy pectin

Gelatinised waxy maize starch and low-methoxy pectin mixtures were solubilised/dispersed in water and cross-linked with sodium trimetaphosphate (STMP). The polysaccharides were subjected to a-amylase, ß-amylase or amyloglucosidase (AMG) hydrolysis for different times, and at two starch to pectin combination ratios (3:2 and 2:3). The extent of hydrolysis by porcine pancreatic a-amylase of the cross-linked (gelatinised) starch was 54.8–58.9% in comparison with gelatinised starch (for different incubation times), corresponding to 52.3–58.9% and 51.3–55.3% of the starch in the uncross-linked (UL) 3:2 and 2:3 starch to pectin ratios (for the same hydrolysis times). Blends of individually cross-linked starch to pectin ratios (3:2 and 2:3) were hydrolysed to 66.2–67.0% and 65.4–71.8%, respectively, compared with the corresponding UL counterparts. When the gelatinised starch was incubated for 0.5–36 h with ß-amylase, hydrolysis ranged from 9.2% to 26.2%, and from 5.4% to 12.2% when the starch was cross-linked (corresponding to 40.0–58.7% of the gelatinised starch).