The researchers, led by MaryAnne Drake from North Carolina State University, report that whey protein contributed to sweet flavours while soy protein contributed to cereal/grainy flavours in prototype beverages.
"These results will aid researchers and product developers in optimizing sensory quality in meal replacement products," wrote the authors in the Journal of Food Science .
According to background information in the article, the meal replacement product market if estimated to reach $8bn (€5.8bn) in the US by 2008, and are designed to provide 100 per cent of the U.S. Recommended Daily Intake (RDI) for at least 12 essential vitamins and minerals.
They should also contain eight to ten grams of protein.
While both soy and/or whey proteins are commonly added to these products, flavour remains a major challenge for formulators, said Drake and co-authors, when adding protein to food products.
"Proteins can often impart off-flavours or aftertastes," they said.
To gain a better understanding of this, the researchers formulated prototype beverages and bars with three levels of whey and soy protein (100 per cent whey, 50-50 whey-soy, 100 per cent soy), and then recruited 85 consumers to test the products.
The bars were peanut butter-flavoured, while the beverages were flavoured with vanilla.
The prototypes were also compared to commercial products.
They report that both the type of protein used and the formulation of the product contributed to differences in flavour and texture.
"Sensory properties of prototype bars and beverages fell within the spectrum of commercial products," they added.
Drake and co-authors also report that the prototype bars made with whey protein were characterised by a sweet aromatic and vanillin flavour, while the texture was characterised by adhesiveness and cohesiveness.
On the other hand, prototype bars made with soy protein had a nutty flavour and the texture was denser. "
Consumers liked prototype meal replacement bars and beverages made with whey or a combination or whey and soy over bars made with only soy.
Formulation plays a crucial role in protein ingredient applications and different proteins contribute distinct flavors and textures ," concluded the researchers.
Source: Journal of Food Science Published online ahead of print, OnlineEarly Articles , doi: 10.1111/j.1750-3841.2007.00429.x "Sensory Properties of Meal Replacement Bars and Beverages Made from Whey and Soy Proteins" Authors: J.L. Childs, M.D. Yates, M.A. Drake