Simulating Process Conditions for Improved Flow Characterisation of Food Powders
Powders and other particulate materials are widely used within the food and nutraceutical industry, so in order to fully understand and optimise unit operations and processes, knowledge of powder properties, including flow behaviour, is critical. Powder processing typically involves several unit operations, with each subjecting the powder to different stress and strain regimes, from the high stress, static conditions present in hoppers to the dispersed, dynamic state of a fluidised bed dryer. As powder behaviour is influenced by process conditions, flowability will vary across applications and the requirements for optimal performance will differ. Poor flowability can reduce production efficiency, increase waste and ultimately lead to an increase in production costs.
Case Study 1 - Quantifying the Impact of Humidity on Food Powders
With many dry foodstuffs the ingress of even small quantities of water can compromise product performance. Prime examples include instant coffee, sugars, gravy granules and seasonings (pictured below), which can all change from being relatively free-flowing, easily manageable powders to far less desirable clumps or even a solid mass with the uptake of moisture. Likewise, in manufacture, inadequately controlled moisture levels can compromise flow characteristics and other properties of the process stream, leading to blockages, stoppages and reduced efficiency.
There are two potential solutions to problems associated with moisture absorption, either tightly control humidity levels during storage and processing, or dry the powder within the process stream. However, both solutions come at a significant cost, particularly energy intensive drying processes. Food powder processors therefore need to understand the extent to which a powder will take up moisture and, crucially, how this will affect processability characteristics in the various environments encountered during production. This understanding provides a secure platform from which to assess which moisture control strategies may be required.
The complex behaviour of powders creates a genuine need within the food industry for techniques that offer a complete rationalisation of powder behaviour at various humidity levels. Powder testers, such as the FT4 Powder Rheometer and Uniaxial Powder Tester, offer intuitive and efficient solutions to this problem. The data they provide support effective process optimisation with respect to humidity, avoiding energy intensive and costly moisture control strategies.
Take a look at the studies below (bottom of page) for further information.
Case Study 2 - Process Relevant Properties of Drink Powders
In vending machines, powdered formulations are often reconstituted with water to produce a variety of drinks, such as coffee, hot chocolate and soup. Dispensing of the powders must be accurately controlled in order to achieve a consistent product when reconstituted and to prevent blockages in the machine. The nature of many food powders means that this is often challenging. Powders with a high fat content can be cohesive, may suffer from inconsistent flow, and if left for an extended period of time, can be susceptible to agglomeration and ‘caking’. These same issues can also increase variability, or even cause null results, in traditional powder flow tests such as Angle of Repose, flow through an orifice and shear cell testing.
The variety of storage and dispensing methods used by different machines will subject the powder to a range of conditions, meaning that various properties will influence performance. No single parameter will accurately describe performance in all vending machines and therefore, a range of properties must be quantified in order to understand the likely relationship between powders and how they perform in a given dispensing operation.
In the study below, three similar powdered formulations were produced for dispensing in vending machines. Depending on the type of machine, there will be differences in the way the powders are stored (e.g. container size, or ambient humidity and temperature where the machine is located) and the dispensing method (gravity, screw feeding, etc.) The three formulations were characterised using an FT4 Powder Rheometer, which identified clear and repeatable differences that varied with respect to test conditions.