Abstract
This work presents mixed protein-starch systems as effective foaming agents and stabilisers. The starch size and hydrophobicity play a dominant role in determining the levels of synergy observed. Egg White Protein (EWP) and Pea Protein Isolate (PPI) were selected at two concentrations (0.5, 1 wt. %) along with three starch species of concentrations between 0.5, 1, 3 & 5wt. %. Two commercial OSA-modified starches are compared to a native granule and its heat-treated counter part. The system's effectiveness to incorporate air (overrun) as well as its capacity to hold structure (half life) is evaluated. starch's physical properties (contact angle and size) and their effect on the nature of the Air/Water (A/W) interface (interfacial dilatation rheology, surface tension) are also explored. The effect of protein species as well as starch size and hydrophobicity on foam stability is determined and discussed. The study demonstrates that addition of OSA modified starch (0–5wt%) to (EWP) foams can enhance foam stability by up to 1200% without compromising the foaming capacity, mainly due to a hypothesised exclusion volume effect. Where as the larger heat-treated starch granule is found to increase stability of wet foams by 800%, through a combination of mechanisms.
Highlights
The essential building component of many aerated structures found in products such as cakes, breads and ice cream are protein foams (Davis, Foegeding, & Hansen, 2004)
The Pea protein isolate (PPI) systems show little tolerance to the presence of starch and the overrun is compromised when compared to the original foam solutions (~650%)
Egg white proteins (EWP) foams on the other hand show greater tolerance, but even enhancements in overrun when combined with OSA2
Summary
The essential building component of many aerated structures found in products such as cakes, breads and ice cream are protein foams (Davis, Foegeding, & Hansen, 2004). Recent study into stabilisation of foams and emulsions by mixtures of proteins and particles observed that the addition of surface-active particles in the presence of protein facilitated the formation of a more rigid interfacial layer, due to enhanced packing at the interface. This augmentation of the interfacial layer in the presence of both particles and proteins was observed without any evidence of electrostatic interactions between the molecules (Murray et al, 2011). The focus of this study is to induce potential synergy at pH7 where electrostatic interactions between the molecules is minimised, with the aim of seeking out novel formulations for producing foams of high stability and comparable foaming capacity to EWP, that can serve as a potential (partial) replacers
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