Design, optimization and characterization of freeze-dried emulsions based on sodium alginate and whey protein isolate intended for cosmetic and dermatological applications

Prus-Walendziak, Weronika and Douglas, Timothy and Kozlowska, Justyna (2025) Design, optimization and characterization of freeze-dried emulsions based on sodium alginate and whey protein isolate intended for cosmetic and dermatological applications. ACS Omega. ISSN 2470-1343

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Abstract

Traditional water-based emulsions dominate personal care products, offering minimal skincare benefits but consuming significant amounts of water resources. This sustainable prototype of biopolymer-based skincare products reduces water usage due to the potential to reuse water sublimed during freeze-drying and enhances biopolymer-based materials’ performance. This study presents the development and characterization of freeze-dried emulsions formulated with biopolymers, specifically sodium alginate and whey protein isolate, aimed at cosmetic and dermatological applications. Emulsions were modified with cryoprotectants, including glycerin, propylene glycol, sorbitol, mannitol, and trehalose, as well as oils (sunflower oil or sea buckthorn oil), beeswax, and Span 80 as an emulsifier. The methodology involved varying the time and speed of emulsion homogenization to optimize the size distribution of the oily phase droplets. The prepared freeze-dried emulsions were characterized by scanning electron microscopy (SEM), mechanical properties, residual moisture content, porosity, and density measurements. The physicochemical properties of obtained matrices significantly depended on the concentration of WPI, aqueous-to-oily phase mixing ratios, and the addition of different types and concentrations of cryoprotectants, oils, and beeswax. The results revealed that the obtained materials exhibited promising porosity (59–95%) and density (varying from 116 to 308 mg/mL), low residual moisture content (from 2.3 to 10.9%), and favorable mechanical properties (ranging from 240 kPa to 1.7 MPa), positioning them as novel materials with potential for skin application. Optimization and a combination of existing technologies for a sustainable, functional skincare solution show a superior performance over conventional formulations in terms of shelf life, microbial stability, reduced preservatives, and more efficient transport and storage.