NEW POSTER: Sodium caseinates with an altered isoelectric point as emulsifiers in oil/water systems

Wednesday, 29 October 2008 16:57

Ma et al. investigated the possibility to improve the suitability of sodium caseinate as emulsifier in o/w emulsions at broad range of pH values. Proteins, such as casein and whey protein, are widely used as emulsifiers in various industrial application areas, e.g. food products, cosmetics and pharmaceuticals. A drawback with proteins as emulsifiers is their low solubility and low net charge at pH values close to their isoelectric points (pI). As a result of this, their emulsifying activity in that pH range is considerably reduced. In the case of caseins with an average isoelectric point around 4.5, reduction of its emulsifying activity at pH values 4-5 has been a severe limitation in its applications in the acidic pH range.

In this work, sodium caseinate was chemically modified in order to alter its isoelectric point (pI). Negatively charged carboxylic groups were introduced to lower the pI, and positively charged amino groups to achieve the opposite. Different chemical amino acid modification approaches were studied and the modified proteins were characterized using free amino group assays, SDS-PAGE, MALDI-TOF mass spectrometry and zeta potential measurements. Oil in water emulsions were prepared using these modified caseinates. The pH stability behaviour of the emulsions was monitored and interestingly the stability of the emulsion could be modulated through steering the pI of caseinate. Using different modified caseinates it was possible to create emulsions that were stable in the acid, neutral and alkaline regions of the pH spectrum. The stability behavior of the emulsions correlated well with the theoretical and experimentally determined pI values of the caseinates. Storage stability of emulsions was also studies at pH around 7, and emulsions made of modified caseinates showed storage similar stability to the unmodified caseinate emulsions.

Reference: Ma, H., Forsell, P., Partanen, R., Seppänen, R., Buchert, J. , Boer, H. Sodium caseinates with an altered isoelectric point as emulsifiers in oil/water systems, COST 928 Workshop, Istanbul 15 - 17 October, 2008.

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