Influences of granule-associated proteins on physicochemical properties of mungbean and cassava starches

The architecture and physicochemical properties of mungbean starch (MB) and cassava starch (CS) granules were modified by calcium cross-linking under extreme alkaline conditions (pH ∼ 12) and the addition of cysteine and calcium lactate at slightly acidic conditions (pH ∼ 5–6). The presence of calcium lactate up to 100 mM at pH ∼ 12 resulted in the low swelling of heated starch granules but high degree of starch leaching. Confocal laser scanning microscopy indicated that the formation of a rigid starch envelope induced by Ca2+ cross-linking under extreme alkaline pH led to the massive leaching of starch content without collapsing the envelope and consequently lowered the final viscosity of both MB and CS (P < 0.05). However, the addition of both cysteine and calcium lactate increased gelatinisation temperature of both starches. Results suggested that the protein-containing envelope plays an important role in determining the granule’s ability to retain the starch content after heat treatment and subsequent pasting and thermal characteristics of MB and CS.