Kett, A.P., Chaurin, V., Fitzsimons, S.M., Morris, E.R., O’Mahony, J.A. and Fenelon, M.A.

2013

Unknown

Food Hydrocolloids

Influence of milk proteins on the pasting behaviour and microstructural characteristics of waxy maize starch

Published

()

Starch; Waxy maize; Pasting; Casein; Whey protein

30

661

671

Gelatinisation of 5 wt% waxy maize starch (WMS) under shear (16.8 s−1), alone and in mixtures with 5 wt% α-lactalbumin (α-lac), β-lactoglobulin (β-lg), α-caseinate or β-caseinate, showed reinforcement of the starch granule structure by both caseinates, but not by the whey proteins (α-lac and β-lg). Reinforcement was evident from (i) later onset of increase in viscosity on heating; (ii) higher gelatinisation temperature by differential scanning calorimetry; (iii) micrographs showing reduced swelling during heating and in the final pastes obtained on cooling; and (iv) elimination of a characteristic “secondary swelling peak” observed for WMS immediately after completion of heating to 95 °C and attributed to fracture of a restricting layer of lipid and protein at the surface of the granules. A likely mechanism of reinforcement is binding of caseinate to the lipid–protein layer. Images from confocal laser scanning microscopy with fluorescent labelling of protein showed attachment of aggregated β-caseinate to the surface of WMS granules in mixtures that had been heated (under shear) to 70 °C. Corresponding images for mixtures with α-caseinate (which is less aggregated) showed penetration of protein to the interior of the granules, which would allow binding to occur on the inside of the surface layer as well as the outside. The inability of the more hydrophilic whey proteins to reinforce the WMS granules suggests that binding of caseinates to the lipid–protein layer occurs predominantly by hydrophobic association. The understanding that caseinates make gelatinised WMS granules smaller and tougher could be useful in product formulation.

10.1016/j.foodhyd.2012.08.002