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Environment and sustainability

Technology from the physics laboratory can make yoghurt more palatable

Scientists have used advanced laser technology to analyse the viscosity of dairy products. This technology can make it easier for food scientists and the food industry to analyse such properties as keeping dairy products from spoiling and optimally maintaining consumer interest.

The food industry is gigantic. Every day, food worth billions and billions of dollars is produced to feed the world’s population. Unfortunately, a lot of food is also thrown out, and dairy products such as yogurt, milk and crème fraîche are often dumped in the trash can, simply because the texture has changed since production.

In a world in which sustainability requires increasing consideration, food scientists and industry actors are struggling to discover the properties in foods such as dairy products that ensure that they do not lose the texture that customers prefer and are therefore not discarded.

So crème fraîche or yogurt should preferably always have the viscous, creamy and firm texture that people like.

Now researchers from the University of Copenhagen have shown that a laser technology that originated in the physics laboratory and was developed for space research can be used very simply to measure the viscosity of a dairy product.

“We suggest using dynamic laser speckle patterns to analyse the viscosity of dairy products as food is developed. This means that the products can be kept sterile and sealed throughout the process, which cannot be done today,” says first author Dmitry Postnov, postdoctoral fellow, Department of Biomedical Sciences, University of Copenhagen.

The new study was recently published in PLOS One.

Current technology for measuring viscosity is inadequate

Most current methods of measuring the viscosity of milk or yoghurt require direct contact with the food.

The problem with this is that contact with the food means that it cannot be sealed and kept sterile. This leads to several complications in analysis, which therefore takes longer and requires additional sampling to obtain proper measurements.

For example, researchers cannot measure how the texture of a dairy product changes over a week under real-life conditions if the product continually has to be placed in an instrument for measurement.

Instead of current technologies, Dmitry Postnov therefore proposes using the correlation between viscosity and the dynamic laser speckle pattern.

“Dynamic laser speckle patterns are well known in physics. They were first observed in astrophysics but have since expanded into other fields, including playing a major role in biomedicine and optical imaging techniques such as laser Doppler flowmetry and speckle contrast imaging. In our experiments, we have shown that the viscosity of a liquid can be analysed through glass without compromising the sterility of the product. This will enable us to study how the viscosity changes over time in real-life situations,” says Dmitry Postnov.

How dynamic laser speckle patterns work

Dynamic laser speckle patterns result from particles interfering with laser light.

For example, in milk, fat and protein particles scatter incoming light and create a speckle pattern that researchers can capture with their instruments.

Changes in the speckle pattern mean that the particles are moving, and the researchers can use this to determine the viscosity of the fluid.

“This is simple physics. When no external force is applied, the fat and protein particles will continue to mingle with each other because of the Brownian motion. The speed of these movements indicates how viscous the fluid is. The more viscous it is, the slower the particles move, and we can estimate this,” explains Dmitry Postnov.

Technology easily transferable to the food industry

Dmitry Postnov and colleagues have investigated how precisely this technology can determine the viscosity of dairy products.

In their experiments, the researchers created milk samples with varying amounts of CREMODAN® 719, which the industry uses to increase the viscosity of dairy products.

Then the researchers used dynamic laser speckle patterns to determine the viscosity of the milk samples. The results showed that they could do this very precisely, which validated the method.

“I believe that the food industry can use this technology. The instruments need to be calibrated, but otherwise they are easy to use and require no special training,” says Dmitry Postnov.

Developed laser technology to determine blood flow

In fact, Dmitry Postnov’s research only partly focuses on dairy products.

His research mainly focuses on developing laser technology to study blood flow in blood vessels so that doctors can make better diagnoses and determine whether a given treatment improves the circulation.

Dmitry Postnov’s research has three strands:

• developing the technology;

• using technology to carry out physiological and pathophysiological experiments on animals; and

• transferring the lessons from these laboratory experiments to clinical application in humans.

“Our experiments have led to significant improvement in this technology, which we will translate to human and clinical science applications. Among other things, laser speckle imaging enabled us to study the blood flow in animal kidneys and led to some interesting discoveries in renal physiology related to synchronized activity within the kidneys. In collaboration with our colleagues in Boston, we have also applied this technology to understand the physiology of stroke and to find potential treatment for it,” says Dmitry Postnov.

Dairy products viscosity estimated by laser speckle correlation” has been published in PLOS One. In 2017, the Novo Nordisk Foundation awarded a grant to Dmitry Postnov, Department of Biomedical Sciences, University of Copenhagen for the project Optical Biopsy: A New Tool for Early Diagnostics of Cardiovascular Related Diseases.

Dmitry Postnov
Postdoc, International Researcher
Blood flow imaging is an essential part of modern biomedical research, particularly in vascular and neurovascular physiology. Various imaging modalities are used, such as ultrasound, MRI, laser Doppler flowmetry, optical coherence tomography and laser speckle contrast imaging (LSCI). The latter three belong to the laser speckle based modalities and are leading technologies for contrast agent-free imaging of the microcirculation. After a brief introduction to the general laser speckle theory, this overview will focus on LSCI, as the most extensively used tool for rapid wide-field flow characterization. We will address its technological aspects: signal to noise ratio, spatial and temporal resolution, the relation of contrast to speed; and physiological applications: vasomotion, cardiac pulsatility in the microcirculation and renal blood flow synchronization studies. As the conclusion, we will discuss the cutting edge developments in the speckle analysis and capability of LSCI to become a quantitative tool.