Thesis Type: Doctorate
Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Food Engineering, Turkey
Approval Date: 2010
Student: ELİF TURABİ
Co-Supervisor: SERPİL ŞAHİN, SERVET GÜLÜM ŞÜMNÜAbstract:
The main objective of this study was to design gluten free rice cakes containing different gums and an emulsifier for baking in infrared (IR)-microwave combination oven. In the first part of the study, the effects of different gums (xanthan, guar, xanthan-guar blend, κ-carrageenan, locust bean, hydroxypropyl methylcellulose (HPMC) and xanthan-κ-carrageenan blend) and emulsifier blend (PurawaveTM) on physical properties of cake batters were investigated. In the second part of the study, weight loss, specific volume and texture of the cakes baked in different ovens were determined. Macro and micro-structures of the cakes were investigated both qualitatively and quantitatively by using image analysis and Scanning Electron Microscopy (SEM). In the last part of the study, Response Surface Methodology (RSM) was used to optimize IR-microwave baking conditions and formulation of the cakes. Power law and Casson models were suitable to explain the rheological properties. Xanthan and xanthan-guar gum blends resulted in higher apparent viscosities as compared to other gums. Gum types affected the dielectric properties and gelatinization enthalpies of cake batter. Emulsifier addition increased the volume and porosity but decreased the firmness of the cakes baked in IR-microwave combination oven. More porous cakes were obtained when xanthan and xanthan-guar gum blend were used. Baking method was found to be important in affecting porosity, pore size distribution and microstructure of the cakes. The highest quality gluten-free rice cakes were obtained when the formulation contained xanthan gum and 5.38% emulsifier and baked using 40% microwave power, 60% halogen lamp power for 7 min in IR-microwave combination oven. In addition, baking time was reduced by 76.7% as compared to conventional baking.