Researchers from Chinese Academy of Agricultural Sciences in Beijing report that protein concentrates from sweet potato could form stable emulsions at a concentration of about 1 per cent, according to findings published in Food Hydrocolloids.
Emulsifiers work by stabilizing oil suspended in water, and this is achieved electrostatically. Part of the emulsifier is attracted to water, while another part is attracted to the oil. The isoelectric point (pI) is the pH at which the emulsifier has no electrical charge, and therefore in a food with a pH close to the pI the emulsifier can no longer stabilize the emulsion effectively.
Emulsifiers, stabilisers and gelling agents are to be subjected to an EFSA review. All additives approved before 20 January 2009 are to be subject to a review, as some were approved as long as 30 years ago and the state of the science has moved on since then. Emulsifiers, stabilisers and gelling agents will follow the current review of colours.
The Beijing-based scientists examined the effects of sweet potato protein concentrates at levels ranging from 0.1 to 2 per cent and with emulsions with oil values ranging from 5 to 45 per cent.
Results showed that the emulsifying properties of the sweet potato proteins depended on both variables, with protein levels over 1 per cent producing more stable emulsions, they said.
Furthermore, oil levels below 35 per cent were found to decrease the creaming rate of the emulsion.
Analysis of the protein showed that the main components at the boundary between the oil and water were Sporamin A and Sporamin B, added the researchers.
“This study provided valuable information on the potential application of SPP as emulsifiers in food industries,” wrote the researchers.
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2010.05.011
“Emulsifying properties of sweet potato protein: Effect of protein concentration and oil volume fraction”
Authors: Q. Guo, T.H. Mu