Improving thermal stability of hydrolysed whey protein based infant formula emulsions by protein carbohydrate conjugation.
Whey protein hydrolysate (WPH) ingredients are commonly used in the manufacture of partially hydrolysed infant formulae. The heat stability of these emulsion based formulae is often poor, compared with those made using intact whey protein. The objective of this study was to improve the heat stability of WPH based emulsions by conjugation of WPH with maltodextrin (MD) through wet heating. Emulsions stabilised by different protein ingredients, whey protein isolate (WPIE) whey protein hydrolysate (WPHE) heated WPH (WPH HE) and WPH conjugated with MD (WPH CE) were prepared and heat treated at 75degC, 95degC or 100degC for 15min. Changes in viscosity, fat globule size distribution (FGSD) and microstructure, evaluated using confocal laser scanning microscopy (CLSM) were used to monitor the effects of hydrolysis, pre heating and conjugation on the heat stability of the emulsions. Heat stability increased in the order WPHE<WPIE<<WPH HE<<WPH CE; emulsions WPHE, WPIE and WPH HE destabilised on heating at 75degC, 95degC or 100degC, respectively. Flocculation and coalescence of oil droplets were mediated by protein aggregation (as evidenced by CLSM) on heat treatment of WPH HE emulsion at 100degC, while no changes in FGSD or microstructure were observed in WPH CE emulsion on heat treatment at 100degC, demonstrating the excellent thermal stability of emulsions prepared with the conjugated WPH ingredient, due principally to increased steric stabilisation as a result of conjugation.
Food research international