Homogenisation in the dairy process - conventional processes and novel techniques

Abstract

Milk and dairy products are typical examples of high pressure homogenized commodities. High pressure homogenization is therefore a well established process and realized at around 10 Mio tons per year in the dairy industry. Milk and dairy products are homogenized to improve product properties such as color, consistency, taste, creaming stability, creaminess and mouthfeel [1]. The basic idea of high pressure homogenization is to pressurize an emulsion premix up to several hundred bars and then pump it through a disruption system (full stream homogenisation). State of the art as disruption systems are flat valves. Besides conventional flat valves a simple or complex orifice type of valves like the interaction chamber of Microfluidics® may also serve as disruption system [2]. Within the talk, different disruption systems will be compared with regard to disruption effectiveness and power efficiency. As high pressure is required for droplet disruption into the submicron range high investment, energy and maintenance costs result from high pressure homogenization processes. The product active ingredients are subjected to intense mechanical and thermal stresses. Problems in term of costs, maintenance and ingredient degradation may be overcome by a novel micro-structured orifice called “Simultaneous Emulsification and Mixing” (SEM) [3], which will be presented in the second part of the talk. It combines the two unit operations ‘mixing’ and ‘emulsification’ in one single process unit, which results in significant energy and cost reduction, product quality improvement and process intensification. For this, an additional stream (e.g skim milk for dairy processes) is injected directly into the droplet disruption zone of a high-pressure disruption system. The design of these SEM-valves is based on CFD simulations of local flow conditions. The fabrication of the valve is realized with micro process engineering tools. The influences of product and process parameters on energy efficiency and product quality are discussed for the dairy process.