Viscosimetric and tensiometric investigations of interactions between gelatin and surface active molecules of various structures

Gelatin is a protein widely used in food, pharmaceutical and cosmetic products. Polypeptide structure of gelatin molecule facilitates its interactions with different surface active ingredients that are often present in such products. These interactions can significantly change properties of gelatin solution in the bulk, as well as on the interface, and therefore influence the stability of the system. In this study interactions between gelatin and different surface active molecules: two small molecule surfactants (Tween 80, Triton X100) and two surface active polymers: starch derivative (octenyl succinic starch, OSA) and cellulose derivative (hydroxypropylmethyl cellulose, HPMC), were investigated using tensiometric and viscosimetric measurements. The results show that possibility and mechanisms of interaction between gelatin and surface active molecules depend not only on the nature of molecules, but also on its chemical structure. Thus, non-ionic, branched small molecule surfactant Tween 80 shows hydrophobic mechanism of interaction with gelatin, while other used linear small molecule surfactant, Triton X100, does not interact. Polymeric surfactant OSA starch is a weak anionic polyelectrolyte, but due to hidden polar group, shows hydrophobic interaction with gelatin, dependant on pH of the solution. HPMC molecule, which is non-ionic with small hydrophobic substituents, does not interact at all.