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Enzyme-modified soybean sugar - another gum arabic replacer?

By Stephen Daniells , 14-Nov-2006

Soybean soluble polysaccharide (SSPS) modified by a rhamnogalacturonase (RGase) enzyme could be used in flavour emulsions, and is a potential replacement for gum arabic, say researchers from Fuji Oil Company.

"It is possible to prepare flavour emulsions with RGase-digested SSPS with improved stability, compared to SSPS or other high molecular weight emulsifiers such as gum arabic and modified starch," wrote lead author Akihiro Nakamura in the journal Food Hydrocolloids (Vol. 20, pp. 1029-1038).

The Fuji Oil researchers, in collaboration with researchers from the University of Guelph in Canada, looked into the emulsifying properties of enzyme-digested SSPS, and compared this to standard SSPS, an emulsifier already reported to be effective in stabilizing certain beverages, and in flavour emulsions thanks to its stability at a range of pH values, its high water solubility, and its low bulk viscosity.

 

While the results appear to show the great potential of the RGase-modified SSPS, other enzymes, such as polygalacturonase (PGase), galactosidase (GPase), and arabinosidase (Afase) were less positive as potential gum arabic replacers.

 

The supply of gum arabic (E414 in the EU) is variable due to political and climatic factors in the primary producing countries like Sudan and Nigeria and this has led to spikes in the price of the ingredient.

 

Gum arabic, known as the 'Rolls Royce' of gums, is widely used by the food and beverage industry, and the top producers (mainly Sudan) bring about 50,000 tonnes of the gum to the market each year.

 

Attempts to find an alternative have lead researchers to look into alternatives that could be used as a thickener, adhesive, and stabiliser for food and beverage applications.

 

The new research looked into the emulsifying properties and characteristics of the digested fractions in oil-in-water emulsions containing between 10 and 50 per cent soybean oil at low pH (4.0).

 

Droplet-size distribution and dilution stability were also investigated by Nakamura and co-workers.

 

The researchers report that the digestion with the RGase enzyme produced emulsions that were very stable when diluted. The average particle size is reported to have been between 0.61-0.65 micrometres in diameter, with no changes observed during 30 days of study at all the dilutions studied.

 

On the other hand, the researchers report that the other enzymes, PGase, GPase and AFase, all led to an SSPS with a reduced emulsifying activity and stability.

 

"Hydrolysis with RGase seemed to improve the emulsifying properties of SSPS, by modifying its size without affecting the composition of the polysaccharide," wrote Nakamura.

 

"It is possible to hypothesise that while the proteins associated with the polysaccharide chains are still playing a major role in anchoring the polysaccharide to the oil/water interface, the SSPS chain is more flexible, it has a smaller molecular weight distribution than that of the original SSPS but still contains the arabinan and galactan portions, so important for the formation of a thick hydrophilic layer on the surface of oil droplets."

 

The new study follows other research looking into potential replacers for gum arabic, ranging from corn fibre gum to maltodextrin-whey protein complexes.

 

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