Reducing water and chemical use in food processing

Researchers from Purdue University, supported by the US Department of Agriculture, have found a way to simplify the process of cleaning and sanitising food processing equipment, without requiring chemicals. This is achieved by creating microscopic bubbles in water, which reduce the need for both chemicals and copious amounts of water. The microbubbles can be used for cleaning, as well as foams used in foods, rapid DNA and protein assessments, destroying dangerous bacteria and more. Published in the journal Scientific Reports, the research describes the speeds at which pores made in films close, which is comparable to similar processes when bubbles are formed.

“When injecting air from a needle into a bubble, the bubble neck keeps thinning and the bubble forms. Understanding the collapse of a pore is going to help us understand the pinch-off point of bubble generation,” said Jiakai Lu, assistant professor of food science at the University of Massachusetts Amherst.

When a pore or hole is formed in a fluid, it has two options and will trend toward the one that uses the least amount of energy. If the hole is large it continues to expand, while smaller holes collapse, closing themselves up. Understanding the speed at which the pores closed has been challenging because, as a hole collapses, its curvature becomes infinite and a singularity is formed.

“This touches on a deep problem in physics. When that singularity is formed, the equations that govern the process don’t work any longer. We found ways to go around this problem to predict when the hole is going to collapse and use that to predict the volume of the microbubbles and the time it will take to form them,” said Carlos Corvalan, associate professor of food science.

Carlos Corvalan and Jiakai Lu modeled the creation of microbubbles, which may be useful for cleaning food processing equipment with fewer chemicals and less water. An emerging microbubble before pinched off (left) is similar to a contracting pore (right), in which fluids are driven toward the neck from a high-pressure region (red) to a low-pressure region (blue) near the pore tip. Image credit: Jiakai Lu.

In viscous fluids, pores close at a constant rate, but in water, the speed at which a pore closes continues to accelerate. For fluids with intermediate viscosity, the pore begins closing at an increasing rate, with the rate becoming constant until the pore closes. Using high-fidelity computational models, researchers predicted the point at which the speed changes from ever-increasing to constant. Using that information, researchers then designed pumps that can create the right size of bubbles.

“Although we have a singularity, the speed for the collapse becomes essentially constant,” said Corvalan.

In order to control the volume of microbubbles, researchers need to determine when the neck of the bubble will collapse. By predicting when it will collapse, researchers can also control the bubbles’ formation.

Top image credit: ©stock.adobe.com/au/Vera Kuttelvaserova