A novel flow system for the concurrent product and process design of emulsion-based formulations

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.Rapid formulation of products with regard to the consumers’ needs is one of the strategic challenges in the food industry. Having once employed advanced manufacturing methods for designing and developing a product and a process, it is of imperative importance to achieve the rapid and concurrent product and process design of consumer-driven food formulations. Many consumer products are emulsions as either semi-finished or finished products. This research aims to develop an integrated continuous formulation system that employs a flow processing protocol to explore the design and optimisation of liquid-liquid dispersions and mainly emulsions. Three novel flow system designs, studied in the current research, are a continuous flow system (A) which is an Oscillatory Baffled Flow Reactor (OBFR); a continuous flow system (B) which is designed and developed by integrating a membrane emulsification device with the OBFR and; a continuous flow system (C) which is designed and developed by the integration of the OBFR and a premix membrane emulsification device. A case study of a food-grade orange beverage emulsion is investigated based on Response Surface Methodology (RSM) combined with Principal Component Analysis (PCA). The results indicate that the food macroemulsion can be produced by the continuous flow system (C) with droplet sizes in the range of 4.18-14 μm depending on various experimental conditions such as ingredient concentrations. It is also obtained by operating the system under 4.14 bar of backpressure at 1.72 ml/min net flowrate, 9.0 mm oscillation amplitude and 2.5 Hz oscillation frequency. The continuous flow system (B) and the OBFR have not shown such ability to produce the macroemulsion with these values whereas the minimum droplet size obtained is 18.56 μm. When comparing the flow system (C) with classic mechanical emulsification systems such as high-pressure homogenizers, the system (C) has some advantages that are low energy consumption, control of droplet size distribution (i.e. the choice of membrane), mild shear stress technique and less time-consuming process. Furthermore, the case study implies the elucidation of empirical models using the flow system (C) to link quality attributes and formulation parameters. These models are used to then predict and make a target formulation for the orange beverage emulsion of the case study. Such capability can drastically reduce the lead-time in developing new products that satisfy customer requirements. For instance, the target formulation has concentrations of 14.90% (w/w) Arabic gum, 0.22% (w/w) xanthan gum and 8.22% (w/w) orange oil. The PCA procedure is also used to identify the importance of rates for quality attributes (i.e. mean particle size, emulsion stability and density) to provide research and development team of new product development with a structural quality model of the orange beverage emulsion. Thus, the RSM coupled with the PCA is a capable tool for designing and developing product and process in the least time and cost effective manner. Overall, this research contributes to knowledge in developing a continuous flow system that is a promising alternative for the formulation of product and process design. It combines several advantages of the OBFR and the membrane emulsification method to formulate finished products with the desirable quality requirements from manufacturers and customers simultaneously such as shear sensitive products and high-value products