Whey proteins from cow's milk are used as emulsifiers in a broad range of food products including ice creams, beverages, salad dressing and sports supplements, and are classified as either concentrates (protein content between 25 and 80 per cent) or isolates (more than 90 per cent protein).
The new research, published on-line in the journal Food Research International (doi:10.1016/j.foodres.2006.01.007), compared standard whey protein concentrates (WPC) with nutritionally modified whey protein concentrates (MWPC) to form and stabilise oil-in-water emulsions.
"This study provides data that specialty MWPCs may provide additional benefits over commodity WPC in food emulsions. It may give food formulators and processors the ability to produce more stable or nutritionally enhanced products, potentially avoiding the use of non-natural emulsification systems," co-researcher Loren Ward from Glanbia Nutritionals told FoodNavigator.com.
A recent survey by Danish 3A Business Consulting on whey and lactose ingredients, suggests that food makers are increasingly viewing whey and lactose products as an ideal means of achieving added value.
As such the global whey protein concentrates and isolates market is estimated at 395,000 MT in 2004 representing a value of just over $1bn. The US remains the biggest producer at 187,000 MT followed by Europe with 159,000.
The MWPC in this study was manufactured using Glanbia's proprietary membrane filtration process that filters out the low molecular weight proteins and retains the high molecular weight proteins in the concentrate. The standard WPC retained all the proteins.
Whey contains a variety of proteins, each with unique functional and nutritional characteristics, such as beta-lactoglobulin, alpha-lactalbumin, glycomacropeptide, serum albumin, immunoglobulins, lactoferrin and lactoperoxidase.
"We have concentrated the larger molecular weight proteins such as immunoglobulins and lactoferrin to provide a WPC with unique and enhanced nutritional and functional characteristics," said Loren.
The scientists, led by Professor Julian McClements from the University of Massachusetts, prepared oil-in-water emulsions by adding 10 per cent corn oil to the 90 per cent WPC solutions, the latter had been prepared by adding between 0.05 and 2 per cent of the WPC powder to a phosphate buffer solution, adjusted to neutral pH.
McClements and colleagues found that the stabilised MWPC emulsion contained smaller average particle sizes and fewer large droplets, an effect attributed to the high molecular weight content of the modified whey and the increased concentration of phospholipids.
"The lipid portion of the MWPC contains 30-40 per cent phospholipids. In addition to providing increased emulsion stability, by enriching the phospholipids, the product provides more phosphatidylcholine, phosphatidylserine and sphingomyelin with potential additional nutritional benefits," explained Ward.
The importance of the higher phospholipid content is proposed to be due to the phospholipids adsorbing to the droplet surface more rapidly than proteins, creating smaller droplets with increased repulsive interactions, thereby limiting the formation of larger droplets.
Another possibility is that phospholipids and proteins may also interact at the water-oil interface, which could boost stability. Also, other studies have suggested that a greater high molecular weight protein content improves emulsion stability.
The improved stability of the emulsion could also explain the higher resistance of the MWPC to higher salt concentrations and thermal processing. The result could have important implications for the food industry, allowing food formulators to produce stable emulsions with enhanced nutritional functionality.
Ward confirmed that the MWPC used in this study is currently commercially available from Glanbia, and said that other versions are also available depending on the final product application.