Stability of Sub-Micron Oil-in-Water Emulsions Produced by Ultra High Pressure Homogenization and Sodium Caseinate as Emulsifier

Abstract

Ultra high pressure homogenization (UHPH) is a non-thermal technology capable of producing emulsions, inducing microbial and enzymatic inactivation and confering new functional characteristics, due to changes in the structures of produced foods. Emulsions containing 1.5 % of sodium caseinate (SC) and 20 % oil (15 % sunflower + 5 % olive) were obtained by colloidal mill (CM, 5000 rpm for 5 min) and by ultra-high pressure homogenization (UHPH, 50-300 MPa). Emulsions were characterized for their physical properties including rheological behaviour, surface protein concentration, visual stability to creaming and oxidative stability under light (2000 lux/m2). The particle size of the CM emulsions was significantly reduced (P < 0.05) by UHPH treatments, although the differences between UHPH treatments were scarce. All CM emulsions were visually totally separated in 2 h; however, no visual separation was observed in all UHPH emulsions even after 20 days of cold storage. Examination of the rheological properties of emulsions in all cases exhibited Newtonian behaviour (n ˜ 1), showing higher viscosity in UHPH emulsions than CM emulsions, although these differences were only significant in emulsions treated at 50 MPa. The oxidative stability analyses revealed a significant increase (P < 0.05) in both primary and secondary oxidation products in CM emulsions as compared to UHPH emulsions.