Starch, lipids, and proteins are the three primary macronutrients in the human diet, providing the main source of energy. These macronutrients exist in many food systems, such as starchy foods, and they may undergo some interaction to alter texture, flavour, nutrition and other properties of starch. Cooked starch is susceptible to rapid digestion by digestive enzymes in the body, leading to postprandial hyperglycemia. Amylose-lipid complexes and amylose-protein interactions have been shown to affect the physicochemical properties of starch, reducing the amount of rapidly digestible starch and increasing the amount of resistant starch. This study aims to investigate the possible formation of ternary complexes between stearic acid (SA), cowpea protein isolates (CPI) and high amylose maize starch (HAMS) and their effect on physiochemical properties of HAMS and in vitro starch digestibility (IVSD). Stearic acid (1.5 and 3% wt.) and protein (10 and 15% wt.) were pasted with HAMS for a short time (30 minutes) and an extended time (2 hours). The paste was freeze-dried and characterised by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and IVSD (Figure 1). The addition of SA and CPI to HAMS resulted in a prominent peak viscosity during cooling that was not observed in the control, suggesting the formation of ternary complexes (starch-lipid-protein). The DSC and XRD results confirmed that the addition of SA resulted in the formation of a V-type complex, and the latter was affected by CPI. The IVSD results (Figure 1) showed that the SA alone and CPI alone with HAMS reduced rapidly digestible starch (RDS), estimated glycemic index (eGI) and increased the amount of resistant starch (RS) compared to the HAMS. The combination of both SA and CPI further reduced RDS, eGI and increased RS compared to HAMS, which contains SA alone and CPI. This further suggests the formation of a ternary complex (starch-lipid-protein) that leads to HAMS, which was less susceptible to digestible enzymes, thus having a lower glycemic index and higher resistant starch content. These ternary complexes between HAMS, CPI and SA may be used as a food-grade ingredient in starchy foods to reduce digestibility and can reduce postprandial hyperglycemia. However, In Vivo digestibility studies may be necessary to ascertain the effect of ternary complexes on the digestibility of HAMS