Development of a “Green” Emulsion with a Milk Protein Hydrolysate: An Evaluation of Rheology, Texture, In Vitro Bioactivity, and Safety

Abstract

Bioactive peptides are promising cosmetic active ingredients that can improve skin healthand appearance. They exhibit a broad spectrum of activity, including anti-aging, antioxidant, an-timicrobial, and anti-inflammatory effects. The aim of this study was to develop a safe, stable, andefficacious environmentally friendly (“green”) emulsion using a milk protein hydrolysate as a modelactive ingredient. Potential emulsions were formulated with biodegradable emollients, stabilizedwith naturally derived mixed emulsifier, and prepared by cold process. They were evaluated forrheological behavior (continuous rotation and oscillation tests), physical stability (dynamic me-chanical thermal analysis—DMTA test), and texture profiles, as well as cytotoxic, antioxidant, andantimicrobial effects. Rheological characterization revealed shear-thinning flow behavior with yieldpoint from continuous rotation tests and predominantly elastic character from oscillation (amplitudeand frequency sweep) tests, with small structural change detected in the DMTA test. These resultsimplied satisfactory rheological properties and good stability. Texture analysis revealed acceptablespreadability and substantivity of the emulsions. The protein hydrolysate showed antioxidant activity.The developed emulsions showed low antibacterial activity against selected microorganisms, butthis was due to the action of preservatives, not peptides. All potential emulsions showed a desirablesafety profile. The results obtained provide the basis for the next stage of formulation development,i.e., in vivo efficacy tests.