Researchers from the University of Leeds in the UK report the formulation of an acidified caseinate-stabilised emulsion using lactam (lactic acid esters of monoglycerides) as a surfactant.
"At higher LACTEM concentrations, foams even more rigid and brittle than whipped cream could be produced from aeration/acidification of the systems, although this was accompanied by irreversible aggregation," wrote Kirsty Alen, Brent Murray, and Eric Dickinson in the International Dairy Journal.
"Incorporation of low concentrations of LACTEM into mixed emulsions containing various ratios of totally solid and totally liquid droplets has enabled us to reduce the proportion of all-solid droplets required to mimic the whipped cream rheology."
The research may help to significantly extend the life of foam-based food products, such as whipped cream, ice cream, sorbets, and mousses, already the focus of much R&D attention.
Only recently, research from Unilever reported the use of fungus proteins called hydrophobin HFBII to produce a foam with exceptional stability, as well as the production of microbubbles using a sucrose surfactant which forms a coating around the air bubbles. Both approaches have produced foams stable for over a year, which is a considerable improvement on traditional whipped cram which has an "effective shelf-life of up to about one day," said Alen, Murray, and Dickinson.
In order to effectively mimic whipped cream, the emulsion must be 'brittle', said the researchers. "This brittle character of traditional whipped cream may partly explain its popular textural appeal: whilst it behaves like a soft elastic solid that can be easily shaped and can support its own weight, it also flows readily in the mouth, possessing a smooth creamy texture."
Using different levels of lactem, an emulsifier already used by the food industry as a 'whipping aid' for dairy and non-dairy creams, the Leeds-based researchers to mimic whipped cream in an emulsion formulation with 30 per cent groundnut oil (liquid) or n-eicosane (solid) and stabilised with sodium caseinate (two per cent).
The emulsifier was found to work by partially displacing the casein protein from the droplet surface in the non-aerated systems, while in aerated/whipped systems it reduced the fracture strain, thereby increasing the brittleness.
"In the latter case, it was possible to make aerated acidified emulsion systems as rigid and as brittle as normal whipped cream," stated Alen, Murray, and Dickinson.
"It would seem that, in order to mimic the textural characteristics of traditional whipped cream, the presence of aggregated solid emulsion droplets is essential to impart the necessary rigidity," wrote the authors.
"The action of an oil-soluble emulsifier is required to displace some of the interfacial protein, thereby inducing strong interdroplet crystal-crystal interactions during whipping, and conferring the desired large-deformation rheology on the aerated system.
"Hence this study has highlighted the importance of solid crystalline fat, even when partial coalescence does not occur. On the other hand, the principle has been established that the amount of solid fat can be significantly reduced by incorporating a low level of emulsifier in aerated emulsions containing a mixture of all-solid and all-liquid droplets," they concluded.
Source: International Dairy Journal
Published online ahead of print, doi: 10.1016/j.idairyj.2008.04.003
"Whipped cream-like textured systems based on acidified caseinate-stabilized oil-in-water emulsions"
Authors: K.E. Alen, B.S. Murray, E. Dickinson