טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNephomnyshy Ina
SubjectDevelopment and Characterization of Zein-Based Emulsion
Gels for Edible Oil Structuring
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Dr. Maya Davidovich-Pinh


Abstract

Oleogelation has recently gained popularity as a strategy for transforming liquid oil into soft solid-like structured gels to obtain the functionality of trans and saturated fats in food products. The gel-like structure is achieved by oil entrapment within 3D network created by self-assembled molecules (oleogelators). Among food grade high molecular weight oleogelators, proteins offer the greatest potential since they are widely available, relatively cheap and are considered healthy ingredient in modern diet. This thesis focuses on the characterization of protein stabilized emulsion gel fabricated using one-step procedure at moderate temperature feasible for large-scale production. The formation of a composite system where the oil droplets are dispersed within continuous protein network composed of particulate protein aggregates was observed by confocal scanning microscopy (CLSM) and Cryo-SEM images. Stability studies, at accelerated physical conditions using analytical centrifugation and thermogravimetric analysis (TGA) revealed glycerol syneresis is responsible for the instability of the emulsion gel at room temperature. Glycerol syneresis resulted in significant increase of hardness and decrease in cohesiveness measured by texture profile analysis (TPA). The deterioration of the mechanical properties after glycerol migration was related to additional intermolecular interactions between zein chains, previously disrupted by glycerol molecules. An oscillatory temperature sweep measurement demonstrated a gel behaviour, with storage modulus (Gʹ) higher than loss modulus (Gʺ) from 4 to 90 °C, suggesting a soft to hard gel transition. While frequency sweep experiment confirmed the formation of physical gel based on hydrogen bonding where the thermo-reversible behavior during the two cooling/heating cycles was attributed to strengthening and weakening of hydrogen interactions between particulate protein aggregates. The emulsion gel showed excellent thixotropic recovery properties with recovery ability up to 100%. Overall, these results provide an important insight on the gelation mechanism and gel characteristics of zein based emulsion gels, which can be used for various food applications.