|M.Sc Student||Ashkar Areen|
|Subject||Designing Functional Foods with Controllable Lipid|
Digestion Based on Olegelation Mechanism
|Department||Department of Biotechnology and Food Engineering||Supervisor||Dr. Maya Davidovich-Pinh|
|Full Thesis text|
Fats are an important ingredient in many food products, contributing to food sensory and textural properties, providing energy and needed for metabolic pathways. High intake of saturated and trans unsaturated fats was found to be related to negative health effects leading to search for healthier fat replacements. The multi-functionality of fat in food products raises a great challenge for the development of fat replacement or reduction. In light of these effects, oil structuring has been proposed as a promising strategy for fat replacement due to their solid texture and high unsaturation content. Oil structuring can be achieved using various structurant types which lead to various gelation mechanisms. The current research aim to explore the relation between gelation mechanism, oleogel properties and oleogel digestibility. Three different oil structuring types were examined with canola oil; ethyl cellulose (EC), E471 (Mono- and diglycerides of fatty acids), and β-sitosterol/γ-oryzanol mixture. Mechanical analysis exhibited gel hardness in the order of E471<EC< β-sitosterol/γ-oryzanol mixture. While simulated pH-stat lipolysis on the same samples demonstrated a significantly different lipolysis scheme for the different gelation mechanisms. More specifically, total lipolysis percentage in the order of EC< β-sitosterol/γ-oryzanol mixture <E471 was received suggesting an indirect relation between mechanical properties and oleogel digestibility. EC based oleogels with various concentrations did not differ significantly in their extent of lipolysis, while increasing the molecular weight lead to lower extent of lipid hydrolysis. However, the use of higher concentration of β-sitosterol/γ-oryzanol mixture as oleogelator reduced the percentage of FFAs released during lipolysis suggesting stronger gels exhibit inferior lipolysis. Interestingly, E471 based oleogel show a revers tendency where increase in E471 concentration alludes to an increase in the percentage of FFAs released although harder gels were obtained. This behavior was related to the lipolysis of the structuring agent used. These results suggest that gelation mechanism has an immense effect on the lipolysis rate.
The ability to control the rate and extent of lipid digestion of oleogel systems by using combination of different structuring agents was also examined. E471 and EC with different viscosities (20 cP, 45 cP) were used. The results suggest that the combination of E471 and EC leads to the formation of new oleogel system with different gel mechanical properties and digestibility in comparison to each components oleogel characteristics. More specifically, harder gels were obtained in the mixture E471: EC (20cP) in comparison to simple addition of each component contribution suggesting a synergistic interaction between these two components. On the other hand the use of EC 45 cP as gelling agent showed significant increases in hardness value in compare to the mixture E471:EC (45cP). While combination of E471 and EC with different viscosities allude to new lipolysis profile with intermediate FFA release, up to 50%, in comparison to each structuring agent lipolysis.
Overall, this study demonstrated the ability to design new functional food material with controllable lipid digestion. An improved understanding of the relationship between food properties and digestion would facilitate the rational design and fabrication of foods with improved nutritional properties.