Addition of amino acids to modulate structural, physicochemical, and digestive properties of corn starch-amino acid complexes under hydrothermal treatment.

Amino acids are the structural units (monomers) that make up proteins and play many critical roles in human diets with or without food processing. In this study, corn starch (CS) mixed with Lys, Ser, Ala, or Asp were subjected to heat moisture treatment (HMT) or annealing (ANN). We evaluated the morphological properties, swelling power, pasting properties, thermal properties, crystallinity structure, and in vitro digestibility of CS and CS-AA complexes. HMT increased the gelatinization temperatures and retarded the retrogradation for CS with or without AAs, while ANN had little impact on gelatinization temperature and promoted the recrystallization. Generally, HMT samples were more enzyme resistant than the ANN samples. For the uncooked samples, the addition of Ser, Ala, and Asp decreased rapidly digestible starch (RDS) and slowly digestible starch (SDS) contents, but increased resistant starch (RS) content. Compared with the control (CS without AA), CS-AA complexes had lower contents of RDS following HMT. Under ANN, CS-AAs had higher content of RDS compared with the control. In all groups (physically mixed, HMT, and ANN) with cooked samples, the addition of different AAs decreased the contents of RDS and increased RS contents to varying degrees.