Structural features, physiological functions and digestive properties of phosphorylated corn starch: A comparative study of four phosphorylating agents and two preparation methods.

Phosphorylation is an important modification to modulate functional and digestive properties of starches. We systematically investigated starch phosphorylation process parameters by using two different preparation methods (slurry and semi-dry conditions) and four commonly used phosphorylating agents, namely sodium tripolyphosphate (STPP), sodium trimetaphosphate (STMP), STMP/STPP (99: 1), and sodium phytate (SP). The effects of phosphorylation on physicochemical characteristics, techno-functionalities, digestive properties and structural features of corn starch were analyzed. Phosphorylation with the semi-dry method resulted in higher phosphorus content, degree of double helix, and degree of starch aggregation and lower amylose content and relative crystallinity than with the slurry method. Phosphorylation using semi-dry conditions, irrespective of the used phosphorylating agent, furthermore decreased the gelatinization temperature, enthalpy, the temperature corresponding to the maximum starch mass loss rate and estimated glycemic index of corn starch, and increased solubility, swelling power, peak viscosity, transmittance, and resistant starch content. Of the phosphorylating agents, independent of the used preparation method, STMP and STMP/STPP resulted in the highest degrees of starch phosphorylation and therefore modulated the physiochemical, functional and digestive properties of corn starch more than STPP and SP. The findings of this systematic comparison provide important information to tailor phosphorylated corn starches to meet specific food requirements.