Reactively extruded corn starch foams via organocatalytic acetylation: Effect of l(+)-tartaric acid as an organocatalyst on the molecular, structural, and digestibility characteristics of starch

Organocatalytic acetylation of corn starch was done via reactive extrusion (REx) using acetic anhydride (AcAn) and l(+)-tartaric acid (TAc) as acylating reagent and green food grade organocatalyst, respectively, for the manufacture of health-promoting snack-type foams. The effect of the AcAn and TAc reagents on changes in fine (molecular) structure and digestibility of the starch was also independently evaluated. The reactively acetylated foam without the organocatalyst had a low degree of substitution (DS = 0.03). All TAc-containing foams showed cross-linking and hydrolysis of starch, even the one where organocatalytic acetylation was analyzed and confirmed. Regarding the impact of the resulting molecular changes on starch on digestibility characteristics, all TAc-containing systems had a significant reduction in resistant starch (RS) content compared to the control foam. The slowly digestible starch (SDS) content increased for these foam systems, a desirable attribute due to the satiety characteristic of this starch fraction.