Ph.D. Dissertation:

Optimization of Novel Extraction Methods and Microencapsulation of Rosa Damascena Extract and Evaluation of its Antioxidative and Antimicrobial Properties in Model and Food Systems (Sponge Cake)

The aim of this study was to use microcapsulated extract of Rosa damascena with desirable phenolic compounds as a natural flavoring in sponge cake formulation to produce a functional product. Extraction by solvent, ultrasound-assisted and microwave-assisted extraction methods were performed to evaluate the yield, amounts of phenolic compounds, and antioxidant properties of the extracts. The alcohol extract under ultrasound pre-treatment for 30 minutes was determined as the best sample with the highest yield and quality properties and was used for the microcapsulation with different concentrations of two wall materials of maltodextrin (5, 10 and 15%) and calcum alginate (0.1%). Microcapsulated samples were dried by freeze dryer. The optimal sample was selected based on the yield of microcapsulation, microstructure, moisture content, amounts of phenolic compounds, DPPH free radical scavenging activity and ferric reducing antioxidant potential (FRAP). To investigate the kinetics of decomposition of the extract’s effective compounds, the microcapsulated samples were packed in impermeable plastics and were stored in desiccator at 4° C for 2 months. The measurement of total phenolic compounds was performed every 15 days at starting from zero time to evaluate the stability of microcapsules during the storage time. The results of analysis of variances (ANOVA) show that the storage time had a significant effect on the amounts of phenolic compounds in microcapsules (P<0.05). The amounts of phenolic compounds in microcapsules were decreased by increasing the storage time. The microcapsules containing maltodextrin (%5) with calcium alginate (0.1%) showed the highest amounts of phenolic compounds (210.73 mg/ml) after 45 days of storage at 4°C. The microcapsulated extracts were added to the formulation of sponge cake. The evaluations of the amounts of phenolic compound, texture and organoleptic properties of samples were performed immediately after preparation of sponge cake and for 14 days of storage at 25°C. The sample containing maltodextrin (15%) with calcium alginate (0.1%) was selected as the optimal sample despite the better taste of control sample.

Keywords: Freeze drying, Rosa damascena extract, Functional, Ultrasound, Sponge cake