Effect of limited hydrolysis of sunflower protein on the interactions with polysaccharides in foams

The objective of the work was to study the effect of different non-surface active polysaccharides on the foaming properties of intact and hydrolysed sunflower protein isolate (SP) (degree of hydrolysis of 1.5 and 9.8%) at neutral pH where a limited incompatibility between macromolecules can occur. Foams were obtained by whipping and the overrun, liquid drainage and collapse of the height of foams were evaluated. A limited enzymatic treatment substantially enhanced foaming properties of sunflower protein. A small degree of hydrolysis (DH=1.5%) enhanced both foam overrun and foam stability against liquid drainage and collapse. However, an increase of DH to 9.8% did not further improve foaming properties. The overrun of foams was decreased in the presence of all the polysaccharides but the performance of polysaccharides as stabilizers of foams depended on the protein hydrolysis, the structure of the polysaccharide and its concentration in the liquid used to make the foam. Xanthan gum at 0.25 and 0.5%, due to its high viscosity performed as stabilizer of both intact and hydrolysed SP foams. The other polysaccharides at 0.25% performed as stabilizers when added to the intact SP foams but destabilized the foams containing the hydrolysed SP. By increasing PS concentration, the detrimental effect could be partially reverted. The results may be interpreted in terms of the bulk and surface rheological properties of the mixed protein/polysaccharide foams and suggest that protein–polysaccharide interactions are strongly affected by the hydrolysis of the protein.