Microbubbles for more efficient drying

Cold boiling: sounds like an oxymoron, right? According to researchers at the University of Sheffield, cold boiling is a more efficient way to dry products for food manufacture, using tiny, hot bubbles.

Instead of boiling a product to evaporate water - the most common technique used by industry - the Sheffield team injected hot microbubbles through the liquid, causing the water to evaporate without boiling.

“We’ve applied this principle, called ‘cold boiling’, to separate water from methanol,” said Professor Will Zimmerman, who led the study. “Although conventional bubbles have been used in evaporation processes before, they still transfer a lot of their heat to the mixture. This wastes a lot of energy and can also ‘cook’ the mixture, which in most cases makes it unusable.

“The process we have developed involves applying the right concentration of hot microbubbles to a thin layer of liquid. This causes the water to vaporise with very little heating of the mixture.”

The cold boiling technique can be used in many industrial processes, from food processing to biofuel production.

Professor Zimmerman’s team is currently working on a pilot project with South Yorkshire company Carbon Sequestration, using the technique to remove excess water from whey. The technique is ideal for whey processing, as overheating whey can significantly reduce its nutritional value.