The ingredient potential of peanut protein concentrate
with a cost-effective and alternative emulsifying ingredient,
suggests a study by US scientists.
"Results obtained from this study suggest that the PPC could be used in food formulations requiring high emulsifying capacity, but would not be suitable for applications requiring high water retention and foaming capacity," wrote lead author Jianmei Yu in the journal Food Chemistry (doi: doi:10.1016/j.foodchem.2006. 08.012).
Emulsifiers are used by food makers to reduce the surface tension between two immiscible phases at their interface - such as two liquids, a liquid and a gas, or a liquid and a solid - allowing them to mix.
According to a report by market researcher Frost & Sullivan, the US market for food emulsifiers currently stands at around $505mn, and is estimated to reach $668mn by 2012.
Propelled by consumer health concerns, food makers are under pressure to design tasty foodstuffs that cut back on the fat. And with the changing needs of the food industry, there has been a growing demand for 'multi-purpose' emulsifiers, said Frost & Sullivan.
And the researchers, from the Food and Nutrition Program, North Carolina A&T State University, see a wide range of applications for peanut protein concentrate (PPC) prepared from defatted peanut flour, an inexpensive, protein-rich and underused by-product of the peanut industry.
"The ability of peanut flours and peanut protein concentrate to be functional is primarily due to their soluble protein contents," explained Yu.
"Proteins with high oil and water binding are desirable for use in meats, sausages, breads, and cakes while proteins with high emulsifying capacity are good for sausages, bologna, soups and salad dressing.
"Fermented peanut flour and the derived protein concentrate showed better functional properties, particularly, water holding and emulsifying capacity, than the unfermented flour and protein concentrate," said Yu.
These observations were based on a study of PPC prepared by dried by spray or vacuum drying of defatted peanut flour (DPF). The functional properties (protein solubility, water/oil binding capacity, emulsifying capacity, foaming capacity and viscosity) were compared to the raw DPF and a soy protein isolate.
The researchers report that, compared to the DPF protein content of 50 per cent, the concentrate contained over 85 per cent protein, as well as exceeding the solubility of the flour.
Yu and colleagues, Mohamed Ahmedna and Ipek Goktepe, report that the spray dried PPC had better functional properties, especially concerning the emulsifying and foaming capacity, than the vacuum oven dried concentrate.
Interestingly, "spray dried PPCs also showed comparable oil binding and foaming capacity to commercially available soy protein isolate (SPC)," they said.
The viscosity of the SPI was superior, however, at lower temperatures, said the researchers, but the viscosity of PPC suspension increased significantly after heating at 90 degrees Celsius.
All of these characteristics were taken as positives by the researchers, who pointed out the industrial applicability of the research.
"The extremely high emulsifying capacity of this PPC makes it also a good candidate for food formulations requiring high emulsifying capacities such as salad dressing and creamy soup," they said.
"The low viscosity of PPC suspension at room temperature and higher viscosity upon heating make PPC a desirable thickener for high protein soups."
The researchers concluded: "Thus, peanut protein isolates and concentrates have the potential to add value to the peanut industry and provide food processor with affordable source of plant proteins with unique flavour and functional characteristics."
The study was funded by the USAID (US Agency for International Development) Peanut Collaborative Research Support Program (CRSP).
