Effect of cross-linking on physico-chemical, thermal, pasting, in vitro digestibility and film forming properties of Faba bean (Vicia faba L.) starch.

ABSTRACT

Faba bean starch was crosslinked (CL) at different levels (1, 3 & 5%) using sodium trimetaphosphate and studied for physicochemical, thermal, pasting and in vitro digestibility characteristics. Further, films were prepared from these starches and characterized for moisture content, thickness, water solubility, opacity, water vapor permeability (WVP) and mechanical properties. Amylose content, swelling power and solubility decreased after modification. CL resulted in decrease in peak viscosity (PV) whereas pasting temperature increased; CL (5%) showed the lowest PV (6474 mPa.s). Steady shear properties showed flow behavior index values <1 for starch pastes, indicating pseudoplastic and shear-thinning behavior. Thermal properties of CL starches showed higher transition temperatures and enthalpy of gelatinization (ΔHgel) as compared to native starch. ΔHgel values of CL starches ranged from 10.70 to 14.20 J/g whereas for native starch, the value was 9.47 J/g. CL resulted in increased resistant starch (from 49.8 to 61.1%), the highest value was for CL (5%). CL starch films exhibited lower moisture content, water solubility and WVP. Film thickness, however, was not affected by modification. CL (5%) starch film showed the highest tensile strength (14.28 MPa) and the lowest elongation at break (25.62%). CL resulted in improved mechanical and barrier properties of starch films.