Doctor of Philosophy (PhD)


Engineering Science (Interdepartmental Program)

Document Type



Eggs are an excellent source of high quality protein containing all essential amino acids (EAA) including leucine. Food-grade protein hydrolysates can enhance the growth of lactic acid bacteria (LAB). Thermal degradation of bioactives normally occurs during microencapsulation by spray drying. Spray drying modeling using computational tools is essential to engineer new food powders and to minimize and thermal degradation of bioactives. The first chapter of this work discusses the optimization of an enzymatic process in terms of reaction temperature, pH, enzyme:substrate ratio, and reaction time using a response surface methodology (RSM) to produce food-grade protein hydrolysates from egg whites (EWH). Resulting EWH produced with proteases from Aspergillus oryzae contained all EAA and showed high antioxidant activity. The EWH were evaluated as a nitrogen source in MRS media for the growth of L. plantarum, L. acidophilus, and L. reuteri. MRS containing EWH had similar performance to that of conventional MRS and produced higher cell yields and better quality of biomass than MRS containing dried egg white proteins. Three-dimensional computational fluid dynamics (CFD) simulations were performed to study the effect of co-current and counter-current spray drying configurations on the quality of microencapsulated fish oil with EWH powders in the last section of this work. Also, the separation of powder particles from drying air at the spray dryer’s cyclone separator was evaluated using CFD. CFD models predicted the drying air flow pattern, particle histories including temperature, residence times (RT), moisture content and particle size of the microencapsulated powders. Predicted moisture content of powders was lower than measured values; however, the predicted mean particle sizes were similar to the measured values. Lower lipid oxidation and microstructure degradation was observed in emulsions dried at 130°C inlet air temperature at feeding rates of 1.0 Kg/h and under counter-current spray drying conditions. The 3D-CFD model predicted lower RT (s) for emulsions dried in counter-current compared to co-current spray drying configurations. The study demonstrated that EWH can be enzymatically produced and can be used as an effective nitrogen source in MRS media. Also, 3D-CFD spray drying modeling can be effectively used to study the moisture evaporation and to predict the final quality of spray dried powders.



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Committee Chair

Sathivel, Subramaniam