The authors of the study, which was grant aided by the Nestlé product technology centre in the UK and published in the journal Reactive & Functional Polymers concluded that the polymeric surfactant, ethycellulose, is an efficient stabilizer for emulsion and lipid based dispersions and has potential for use in reduced fat products.
Surfactants are an important ingredient in the manufacture of chocolate. Their role is to coat the surfaces of the sugar and cocoa particles dispersed in fat, generally cocoa butter, to maintain or enhance the flowability of molten chocolate, said the authors.
They note that controlled flow behaviour of molten chocolate is a requirement for successful processing and for optimal mouthfeel, and this factor is particularly crucial in the formulation of fat-reduced chocolate.
“An obvious approach to minimize the impact of fat reduction on the flow properties of chocolate, as described in literature, is to optimize the concentration and type of surfactants currently used in chocolate manufacture,” said the scientists.
Previous research, they note, reported a significant reduction in viscosity of reduced-fat chocolate by increasing emulsifier level and by using a mixture of lecithin, polyglycerol polyricinoleate (PGPR) and sucrose polyerucate all of which are low molecular weight surfactants.
But they said that using high levels of these surfactants - above one per cent - is generally limited due to resulting off-flavours, legal curbs, or negative rheological effects.
And the authors said that recent studies point to the ability of polymeric surfactants to effectively stabilize particle and droplet dispersions and to modify their flow properties, and they said their goal was to test these types of surfactants ability to modulate the flow properties of reduced-fat chocolate using ethylcellulose in their experiments.
In foods, the use of ethylcellulose has been limited to encapsulation of flavours and vitamins and in food packaging materials, said the authors. “But despite the amphiphilic nature of ethylcellulose, it has not been extensively studied as a polymeric surfactant for the stabilization of dispersed systems,” they claim.
The researchers studied the effect of ethylcellulose on the stabilization of sucrose particles dispersed in vegetable fat (cocoa butter equivalent).
They concluded that on its own ethylcellulose was not sufficiently functional to fluidify the sucrose suspension to a level comparable to a reference sample containing lecithin only.
However, when combined with lecithin, ethycellulose, at concentration as low as 0.05 wt per cent, had an overwhelming effect on the fluidization and dispersibility properties of sucrose particles, improving the preparation of fat-based food confections with reduced fat content.
“In the presence of lecithin both surfactants coexist at an oil-water interface in a co-operative way,” said the authors.
However they said that the adsorption and conformation properties of ethylcellulose molecules at the sucrose-vegetable oil interface, particularly in the presence of lecithin, are complex and not yet understood so more research is merited on the interfacial layer between oil and sucrose particles.
Source: Reactive & Functional Polymers
Published online ahead of print: doi: 10.1016/j.reactfunctpolym.2010.07.012
Title: Use of Ethylcellulose Polymers as Stabilizer in Fat-based Food Suspensions Examined on the Example of Model Reduced-fat Chocolate
Authors: T-A.L. Do, J.R. Mitchell, B. Wolf, J.Vieira