The choice of a homogenizer for a particular application depends on a number of factors, including the volume of sample to be homogenized, the desired throughput, energy consumption, the physicochemical properties of the component phases, the desired droplet size distribution, the equipment available, initial costs, and running costs. After choosing the most suitable type of homogenizer, one must select the optimum operating conditions for that particular device, such as flow rate, pressure, gap thickness, temperature, homogenization time, and rotation speed.
The conversion of separate oil and aqueous phases into an emulsion containing fairly large droplets (>2 |im) is normally achieved using a high-speed blender. For industrial applications using high-viscosity fluids (0.1 < nc < 1 Pa • s), a colloid mill is the most efficient type of homogenizer, but for lower viscosity liquids, either the high-pressure valve homogenizer or ultrasonic jet homogenizer is more suitable. For fundamental studies, one often needs small sample volumes; therefore, specially designed laboratory homogenizers are available, which are either scaled-down versions of the industrial equipment or instruments specifically designed for use in the laboratory. For studies where the ingredients are limited or expensive, an ultrasonic transducer could be used because it can produce small sample sizes. For studies where it is important to have monodisperse emulsions, it may be advantageous to use a membrane homogenizer.
The selection of an appropriate homogenizer for a particular application usually involves close cooperation between the food processor and the manufacturer of the equipment. The food processor must first specify the desired throughput, pressure, temperature, particle size, hygiene requirements, and properties of the sample. The equipment manufacturer will then be able to recommend a piece of equipment that is most suitable for the specific product (e.g., size, valve design, flow rates, and construction materials). It is good practice for food processors to test a number of homogenizers from different manufacturers under the conditions that will be used in the factory prior to making a purchase.
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