Evaluation of different coating materials for encapsulation of phenolic compounds extracted from onion (Allium cepa) skin


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Food Engineering, Turkey

Approval Date: 2017

Student: BÜŞRA AKDENİZ

Co-Supervisor: SERPİL ŞAHİN, SERVET GÜLÜM ŞÜMNÜ

Abstract:

Encapsulation provides a protective barrier to some vulnerable food ingredients such as phenolic and antioxidant compounds against some external factors. Moreover, by the help of encapsulation the unwanted odor or taste of core the materials are masked. The main objective of the study was to evaluate the effects of different type of coating materials on encapsulation of phenolic compounds extracted from onion skin. Coating materials were maltodextrin, gum arabic, casein and whey protein concentrate (WPC). As a coating material, maltodextrin was either used alone or it was combined with the other coating materials at ratios of 8:2 and 6:4. The emulsions were prepared with core to coating ratios of 1:10 and 1:20. Freeze dried capsules were evaluated in terms of total phenolic compounds, antioxidant activity, encapsulation efficiency, particle size distribution, morphology and heat stability. Total phenolic content and antioxidant activity values were higher in microcapsules with core to coating ratio of 1:10 than microcapsules with core to coating ratio of 1:20. Capsules with core to coating ratio of 1:20 had higher encapsulation efficiency values than capsules with core to coating ratio of 1:10. Combining maltodextrin with casein was effective for keeping the phenolic compounds inside the capsule with its higher efficiency values (84.39-89.15%). Particle size of the capsules with core to coating ratio of 1:10 were higher in terms of D32 than the ones with core to coating ratio of 1:20. Optical images of the microcapsules confirmed the particle size distribution results. Usage of casein coating were more efficient than whey protein in terms of increasing heat stability of capsules.