Dry Run

Article by Cordelia Selomulya CEng FIChemE and Yong Wang

Smarter testing for powder development in the dairy industry

IMAGINE you’re an event manager trying to put together the best possible musical performance for the opening ceremony of the Olympic Games. Would you take the following approach? Step one: you go to your local pub and listen to a few bands to see how well they do in front of their audience of 30 or so patrons. Step two: you put the best one on live television in front of the world at the Olympics. Step three: if they don’t perform well under these entirely different and more stressful conditions, you go back to your local pub and look for a different band for the next Olympics. Better luck next time.

Something roughly akin to this costly trial-and-error process used to be the only way for the dairy industry to develop spray-dried milk powders. After successfully testing a small batch of a new powder in a lab or pilot-scale dryer, manufacturers would then advance to far more costly industrial-scale production. Unfortunately, a huge range of factors can influence the end results of spray drying, and many of these factors will vary across differently-sized dryers. Moving to a much larger scale is an expensive way to discover that a certain dairy-powder formulation does not achieve the outcomes you were able to achieve at smaller scales.

Our research group at the Department of Chemical Engineering at Monash University, together with our international partners in China, France, and the US, have worked to develop a more predictive approach, avoiding this costly trial-and-error process.

To continue with the music analogy, the trick is to go into much greater depth in understanding the properties of the bands at the local pub. If we can determine what it is about the way the band (the pianist, singer, and drummer), the venue (the lighting, audience, and seating), and many other factors combine to give a strong performance, we can more effectively predict how well they will do on a larger stage.

Likewise, if we use chemical engineering principles to understand the mechanics of spray drying in exacting detail – from examining the behaviour and properties of single droplets of milk as they dry, to accurately modelling how these properties will change under different drying conditions – we can potentially avoid the trial-and-error. With a thorough understanding of the initial formulations of the liquid feed, and of how particular drying tools and processes will affect that feed, we can predict (and hence tailor) the final product that we’re after. It’s all about precision.

So how does this benefit society?

Reducing the guesswork means new, tastier, healthier, safer, better products. Given that commercial dryers are huge and energy-intensive (processing from 25,000–200,000 t/y of dried milk powder), the risks of trial-and-error are untenable. Hence, the industry has been reluctant to go beyond its tried and true methodologies. Our precision approach removes this obstacle. We have developed close partnerships with many Australian and global manufacturers who are working with us to create, for example, new infant milk powders with a longer shelf-life, or processed cheese with reduced salt and better functional properties.

Although this began with dairy, the principles of precision manufacturing apply throughout the food and dairy industry. The range of applications for spray drying research is increasing every day. We are working with our industry partner to replace white refined sugar with spray-dried low-GI (glycemic index) sugar products. Reducing sugar consumption is an important step in overcoming obesity and diabetes – health problems which are reaching epidemic proportions across many parts of the globe. Another example: low-quality dairy powders can be a nutritional and safety concern in poorer nations. High-quality powders are easier to export if we can engineer them to be longer-lasting, bringing nutritional benefits to people who could not previously afford them.

How it works

We have been building and expanding a Smart Drying Research Platform at Monash University since 2007 (see Figure 1), in collaboration with our international research partners in China (Soochow University), France (Agrocampus Ouest, INRA), and the US (South Dakota State University). We first use single droplet drying (see Figure 2) to understand how materials behave under different drying conditions, and to obtain drying kinetics data from a small sample without the need to run costly trial-and-error experiments. We can then apply different modelling approaches (computational fluid dynamics, mathematical modelling) to optimise spray drying parameters in a larger operation.

Article By

Cordelia Selomulya CEng FIChemE

Former Director of Graduate Research Industry Partnership (GRIP) for the Food and Dairy Industry at Monash University; Professor of Chemical Engineering and Research, and Commercialisation Director of Future Food Systems CRC at UNSW Sydney

Yong Wang

Research Fellow, Department of Chemical Engineering, Monash University

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