Publisher's Synopsis
English summary: A biomimetic approach was carried out to stabilize and modify physically assembled food structures based on enzyme technology. Two different enzymes, namely an oxidoreductase (laccase) and an acyltransferase (transglutaminase), were used as ing agents. First, the enzymatic crosslinking of biopolymer layers adsorbed at the interface of oil-in-water emulsions was investigated. A sequential two step process, based on the electrostatic deposition of pectin onto a fish gelatin interfacial membrane was used to prepare emulsions containing oil droplets stabilized by fish gelatin-beet pectin-membranes (structure formation). Laccase was added to the fish gelatin-beet pectin emulsions and emulsions were incubated for 15 min at room temperature (structure modification). The pH- and storage stability of primary, secondary (coated) and secondary, laccase-treated emulsions was determined. Results indicated that crosslinking occurred exclusively in the layers and not between droplets, since no aggregates were formed. Droplet size increased from 350 to 400 nm regardless of oil droplet concentrations within a matter of minutes after addition of laccase suggesting formation of covalent bonds between pectin adsorbed at interfaces and pectin in the aqueous phase in the vicinity of droplets. During storage, size of enzymatically treated emulsions decreased, which was found to be due to enzymatic hydrolysis (Chapter 2). Crosslinked pectin-coated oil droplets had similar or significantly better stability (p 0.6) was crucial to promote a transglutaminase-induced crosslinking of single oil droplets (Chapter 7). German description: Der Einsatz vernetzungsfahiger Enzyme wurde am Beispiel einer Laccase bzw. Transglutaminase zur Stabilisierung und Modifizierung neuer Verkapselungssysteme untersucht. Ziel der Studien war es insbesondere den Wirkmechanismus der vernetzenden Enzyme in komplexen Lebensmittelmatrizen zu klaren. Im Fokus der Forschung stand die Wirkung der Oxidase Laccase auf eine Fischgelatine-Zuckerrubenpektin-stabilisierte Ol-in-Wasser-Emulsion. Die Ergebnisse belegen, dass ausschliesslich Biopolymere, die an der unmittelbar zur kontinuierlichen Phase hin zuganglichen Grenzflache der Ol-in-Wasser Emulsionen durch die Laccase vernetzt werden konnten. In konzentrierten Emulsionssystemen konnen vernetzende Enzyme neben der Katalyse kovalenter Bindungen innerhalb der Grenzflachenmembran auch Tropfen-Tropfen-Netzwerke induzieren. Die Ausbildung partikularer Emulsionsgele hangt dabei wesentlich vom mittleren Abstand der Emulsionstropfen ab. Diese Dissertation hat gezeigt, dass vernetzende Enzyme wie Laccase oder Transglutaminase in der Lage sind, die Struktur und Eigenschaften von Lebensmitteldispersion zu modifizieren.
