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ISBN 9783843917490

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978-3-8439-1749-0, Reihe Lebensmitteltechnologie

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Cross-Flow Electro Membrane Filtration for the Fractionation of Dairy-Based Functional Peptides

163 Seiten, Dissertation Universität Hohenheim Stuttgart-Hohenheim (2014), Softcover, A5

Zusammenfassung / Abstract

Milk proteins, in particular micellar casein and beta-casein, are known to be precursors of functional peptides with different beneficial properties. These peptides are inactive within the sequence of the protein molecule and can be liberated by gastrointestinal digestion, fermentation or enzymatic hydrolysis. Despite the application of specific proteases, enzymatic hydrolysis of milk proteins represents a complex system, resulting in a mixture of numerous different peptides. Consequently, a great variety of naturally formed functional peptides are found to be leading to difficulties with respect to their selective fractionation or isolation for the application of target functional peptides as food ingredients. Although several techniques have been applied for peptide fractionation, these processes are insufficient to produce satisfactory results in practice.

Therefore, the objective of this work was to establish the application of cross-flow electro membrane filtration for the selective fractionation of dairy-based functional peptides. Consequently, micellar casein and beta-casein were subjected to tryptic hydrolysis. The main functional peptides were isolated, identified and characterized by LC-ESI-MS and RP-HPLC in order to selectively fractionate or enrich peptides having the same functionality. In order to quantify a few selected target peptides with potential bio- and techno-functional properties, a RP-HPLC method was established. A cross-flow ultrafiltration process was constructed to investigate the effects of pH, temperature and molecular weight cut-off of the membrane depending on the raw material, more precisely, micellar casein or beta-casein. Afterwards, the impact of a superimposed electrical field on pressure-driven ultrafiltration was examined for the fractionation of antihypertensive peptides, and the effect of fouling during long-term fractionation was determined. In addition to the fractionation efficiency, the angiotensin-I-converting enzyme inhibitory capacity was specified as an index of bioactivity. With the aim of optimizing the electro membrane filtration, the impact of diffusion, transmembrane pressure and the applied electrical field was studied more closely and the sensitivity of functional peptides against electrolytic effects and oxidative modification was determined.