Over the last decade, consumer demand for natural food products without synthetic ingredients has been constantly increasing. Moreover, public awareness for a healthy lifestyle and food with additional health benefits has been rising as well. Many products that are well accepted by consumers are emulsion based. Emulsions have also shown their great potential for encapsulating bioactive substances which further increases the nutritional value of the resulting food products. However, with regard to all natural ingredients some limitations for the formulation and processing of such products are given. While whey proteins are already known to be good emulsifiers, their usage in food products is restricted to certain pH values. This poses a limitation for the development of innovative food products both in terms of nutritional value as in sensory characteristics. One solution to overcome this constraint is the conjugation of whey proteins with hydrocolloids, namely pectins. Pectins are covalently bound to protein molecules via a Maillard like reaction to improve their performance in emulsifying and stabilizing emulsions at otherwise unfavorable pH conditions. The performance of these conjugates is evaluated in emulsification and storage experiments. At pH 3 and 7, emulsions formed with conjugates show droplet sizes equal or minor to those of emulsions formed only with whey protein. At pH 5.5 (the isoelectric point of whey proteins), usage of protein-pectin conjugates makes it possible to form submicron emulsions with excellent long term stability. Furthermore, the challenge to analyze protein-pectin conjugates regarding their molecular characteristics will be addressed. While SDS-PAGE shows the formation of high molecular weight complexes, the analysis of free amino groups in conjugates is disturbed by the presence of pectin. Interfacial tension measurements can only partly describe the improved emulsifying performance.
Principle investigator: Ulrike S. Schmidt ulrike.schmidt@kit.edu
References:
K. Frank, E. Walz, V. Gräf, R. Greiner, K. Köhler, H. P. Schuchmann, 2012, Journal of Food Science, 77 (12), N50–N57.
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