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Elephants standing on drawing pins - the world of high pressure technology

22 May 2015

Chemical engineer Professor Carl Schaschke is the Head of the School of Science, Engineering and Technology here at Abertay University.

He joined us last summer from the University of Strathclyde where he was Head of the Department of Chemical and Process Engineering.

The author of four books – with a fifth in the pipeline – he is an expert in fluid mechanics, with his principal area of research being high pressure technology.

This he will tell us more about during his Professorial Lecture on Wednesday, 27 May.

As a foretaste, here’s his brief overview of the subject, explaining how it can be used for everything from boiling eggs to killing harmful bacteria.

Food, glorious food

“We all enjoy and appreciate the foods that we eat each day, but do we fully understand how they reach our table? Apart from the fundamental necessity to sustain life, the way we consume food these days is quite different from even a generation ago.

“We expect excitement, novelty, value for money with tamper-proof but easy-to-open packaging that ensures the food inside is guaranteed safe to eat.

“We demand foods which are nutritious and healthy such as fortified organic and minimally processed foods, yet we also demand highly processed foods such as sausages, burgers, baked beans and dehydrated foods, as well as foods which have a long shelf-life or are completely sterile.”

Texture, colour and taste

“It is perhaps not surprising that the food and drinks industry that lies behind the mass production from farm to fork to feeding a nation should be the largest in the UK with a turnover in excess of over £95 billion.

“The challenge is to transform unpalatable or unacceptable raw materials into highly desirable products which are microbiologically safe to eat. All of this is further complicated by the need to maintain food quality in terms of texture, colour, appearance, smell and taste. After all, no-one buys food armed with a colour chart, but we can all recognise a bad apple, stale bread or a rotten fish.

“For the food manufacturer, producing consistent products is further complicated by having to use raw materials that are affected by day-to-day and seasonal variations. Products must be safe to eat, free from contamination, made in a safe environment that conforms to food safety standards and other legal requirements. Manufacturers must also be energy efficient and ensure minimal environmental impact.”

Boiled eggs

“There are many traditional as well as innovative ways in which foods are processed. Boiling, baking, roasting, grilling, frying and microwaving are the most familiar. One new technique, however, is the use of high pressure.

“The effect of applying massive and crushing pressures to the delicate molecular structure of foods is to change their functional properties in surprising and creative ways.

“Under pressures which are thousands of times greater than atmospheric - and in the absence of any heating effects - it is possible, for example, to create a boiled egg. That is, it is possible to coagulate egg white and yolk entirely at room temperature.”

High pressure technology

“The industrial application of high pressure is not new and has, in fact, long been successfully used in the production of plastics, ceramics, metal-forming and pharmaceutical tablet manufacture.

“The pressures used for foods are typically several times greater than those found at the bottom of the deepest oceans.

“With the exception of ma­rine biology and deep sea diving physiology, there has to date been little interest in the effects of pressure on life's delicate biochemistry. It is only within the last two decades that the technology has reached a stage which allows a better understanding and use of the strange effects of high pressure.”

Killing harmful bacteria

“Not only can high pressure kill harmful bacteria such as listeria and salmonella, it can also deactivate enzymes. Bananas and avocados turn black due to an enzyme reaction. Crushing the molecular shape of the enzyme can prevent it from carrying out the undesirable reaction thereby ensuring the fruit remains fresher-looking for longer.

“High pressure can also be used in exciting ways to change the functional properties of proteins and polysaccharides.

“Foams, gels and emulsions can be formed as well as cause solidification of fats or alter the melting point of ice used in the manufacture of chocolate and ice-cream.”

Chocolate, ice cream, jellies and juice

“Meat becomes more glossy, transparent, dense, smooth and soft. Fruit-based jams, jellies, purées and juices are noted as having an exceptional “just squeezed” flavour together with remarkable and striking natural colour. Protein from soya, milk and eggs can form soft textures to make new types of desserts and yoghurts.

“High pressure food processing also has the advantage over conventional cooking techniques by being able to transmit pressure both uniformly and rapidly throughout the body of the food rather than from the outside inwards. The pressure is applied equally from all directions with no distortion or misshaping of the food.”

Elephants on drawing pins

“While the benefits of using high pressure over other techniques are evident, the equipment itself is prohibitively expensive.

“Specialist thick-walled vessels with advanced seals are needed to contain the pressures that are created by using pressure-multipliers, which are equivalent to the weight of an elephant standing on a drawing pin!

“At present high pressure is largely limited to niche foods which have a high added value. Understanding the effects of pressure on the structure of foods forms the basis of my research. As we get to know more about the exciting effects of pressure, we can expect to find many more foods processed this way that we take for granted each day.”

The lecture – Pollution, Pressure and Play – will begin at 6pm on Wednesday 27 May in the Main Lecture Theatre at Abertay University.

In addition to Carl’s talk, we will also hear from Professors Joe Akunna and Gregor White.

The event is free, but booking is recommended. Please book your tickets on Eventbrite.

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