Lipid complexation improves the mechanical properties and functionality of legume starch gels

Legume starches often find limited use in food applications due to their high amylose content and the inherent brittleness and hardness that amylose imparts. We propose that the lipid-complexation of high amylose legume starches may improve some of the functional challenges associated with a high amylose content. In this research fatty acid solutions containing stearic acid, oleic acid, capric acid (CA), glycerol monopalmitate (GMP) and glycerol monostearate (GMS) at 5 %, 7.5 %, 10 % and 12.5 % (w lipid /w dry starch ) lipid concentrations were added to gelatinized pea, chickpea starch and fava starch under heating and constant shear. Changes in mechanical and rheological properties were characterized using texture profile analysis and small deformation oscillatory rheological methods. Complexation of the three legume starches with CA, GMP and GMS reduced hardness by over 20 N, while no changes in cohesiveness, springiness or resilience were observed in the pea starch gels. All starches complexed with CA, GMP and GMS also displayed increased crossover shear strains and reduced linear viscoelastic regions in comparison to their respective un-complexed counterparts. These results suggest that starch complexation with lipids reduced hardness and increased flexibility of the gels. The greatest functional improvements were achieved using CA. Powder X-Ray diffraction revealed the emergence of V-type starch crystallinity from native B-type starches in all lipid-starch complexes, with increases in total crystallinity. Small-angle X-ray scattering analysis revealed that lipid complexation reduces the correlation length, crystalline thickness and amorphous phase length in the starch hydrogels. This work shows that lipid complexation of legume starches improves their functionality. • Starch-lipid complexation increases elasticity and malleability while reducing brittleness. • Starch complexation with capric acid resulted in the most improved mechanical functionality. • Starch-lipid complexation increased total retrograded starch crystallinity and reorganized the solid-state.