Reliability is a turn on

29-Oct-2007 - Last updated on 14-Mar-2017 at 16:59 GMT

Related tags Mix

It's not whizzy new technology that users want, but mixers that are faster, easier, more flexible and more reliable, says John Dunn

From nuclear reactors to jet propulsion for boats, the food industry is capable of coming up with some remarkably advanced technology for mixing and blending its products. But for the majority of firms, mixing and blending technology has changed little over the years, and it is all the better for that. Except for the fish eyes.

Most food manufacturers have no need of whizzy new technology. What they want is more of the same, but they want it "faster", "easier", "more flexible", "more reliable". The reason is that firms are having to change products so quickly that flexibility in mixing and blending operations is vital, says James Winkworth, md of Winkworth Machinery, manufacturer of mixers and blenders.

"The customer wants machines that are easier to use and easier to clean and maintain." And coupled with the rise in the use of foreign workers, they also want machines that are easier to operate, he says. "Customers want machines that are as straightforward and as simple as possible to operate. In fact we are seeing a move away from advanced computer control systems back to more basic controls."

The key, he says, is flexibility, operator friendliness and ease of use and maintenance. "It's about reducing the downtime in the factory. So we are making life as easy as we can with developments such as push-in seals that are a doddle to clean."

Greater accuracy

But there is a growing demand for more accuracy, if not necessarily more technology, as Alan Slack, manager beverage category, Tetra Pak Processing, has noticed. When you're mixing syrup together with water to make a soft drink such as Coca-Cola, the more accurately you can mix it, the less syrup you need to make the final product and the less the give-away, he says. "The screw is always on reducing give-away."

Let's say you're producing a soft drink that aims to have a sugar content of 11.1°Brix, ie 11.1g of sugar in 100g of the finished drink. Now, says Slack, if you are using a concentrate and diluting it, then you may need to set your machine's control system to 11.3°Brix to ensure you always get a minimum of 11.1°Brix in the final product.

"But if you can increase the accuracy of mixing by ± 0.1°Brix, then on average for each drop of product, you have saved 0.1°Brix - and when you add that up over billions of litres of drink it can be a lot of money.

"You could test each batch of syrup first and then set your process controls accordingly, rather than measure the finished product on-line. But we know from milk standardising systems used in the dairy industry that the electronic measurements you make on-line are more accurate than taking a sample and testing it in a lab."

But the emphasis is not just on improved accuracy, says Slack. The move towards more natural ingredients in beverages, such as pectin-based thickeners, is making life very difficult for customers, he says. Pectin is extremely difficult to mix properly and creates "fish eyes" or blobs of undissolved pectin powder in the product.

"If you just threw pectin into a tank and stirred it with a spoon, you wouldn't contact all the individual grains of it with water. Some would start to swell and trap others to create fish eyes - like badly mixed wallpaper paste."

Vacuum mixer prevents fish eyes

Tetra Pak has developed the Tetra Almix vacuum mixer to help mix the more awkward ingredients such as pectin and skimmed milk powder. It is a high-shear mixer that really thrashes the ingredients to produce a homogeneous product free from lumps. The powder is introduced under the liquid surface to reduce the foaming that you can get from skimmed milk powder, for example, and the vacuum also helps cut entrained air.

The downside to using high-shear mixers is their high power consumption, says Slack. "But you can run a high-shear mixer for a shorter time and get a better product than using a low-shear, lower-power consumption mixer for a longer time."

Although lower power consumption, increased output and reduced give-away are increasingly important to food mixing and blending operations, good old-fashioned reliability is still a big driver, according to John Smith, recently appointed director of the new UK office for German mixing specialist Ekato Group.

"Yes, customers are looking for reduced ingredient usage, for more throughput, for reduced energy usage, and for faster processes to cut their operating costs. But they are also looking for more reliability - not just mechanical reliability, but consistency of results."

Final product consistency, particularly for sauces, mayonnaises and pastes, is related to their rheology - the way they flow when a force is applied to them, such as in blending and mixing. And most food companies rely on quick yes/no tests such as dip-in viscometers to tell them whether they have got the rheology right and their product is within spec.

Viscosity measured by torque

However, a number of food companies are now turning to the technology of torque measurement for a better way of monitoring the consistency of their mixes and blends. By connecting a surface acoustic wave non-contact torque sensor to the shaft of their mixer or blender, they can monitor the turning force being applied. This gives them a real-time picture of what's happening inside the mixing bowl and a more accurate measure of the product's rheology and so, ultimately, its consistency and quality.

Torque measurement is particularly useful for monitoring non-uniform foods such as those containing particulates, fibres, vegetables, meat, nuts, raisins, biscuits and so on. And pioneering research at University College Dublin, using Torqsense torque sensors developed by Sensor Technology, has investigated the quality of everything from tomato ketchup and chocolate to pasta sauce and chicken tikka massala.

"Real-time process control is vital if food processors are to achieve the ultimate in product quality," says PJ Cullen who leads the research. But to achieve this outside the lab with a torque sensor means that it has to be sensitive enough to detect changes in food consistency yet tough enough to withstand the regular wash-downs and general industrial abuse of a real food factory.

According to Tony Ingham, marketing director of Sensor Technology, the company's original Torqsense technology was developed over 30 years ago and used at Sellafield to monitor the concrete mix for the encapsulation of radioactive waste. It was about 18 months ago that company developed a state-of-the-art self-contained version that was robust enough for the rough and tumble of food factories.

"You can't measure food mixes and sauces using classic viscometers," says Ingham. "They only work with a pure liquid and even then you have to take a sample out of the mixing bowl and put it in the viscometer by which time things may have changed in the mixer."

The Torqsense is not a bolt-on device - it needs connecting in-line between the motor and the paddle of the mixer. It's relatively straightforward, says Ingham, but he is hoping that a mixer manufacturer will incorporate the technology in its machines as an option, and he says that Sensor Technology is "in discussion" with a number of mixer companies at the moment.

Sonic wave mixing

The PDX Sonic system for pumping, heating, entraining, mixing, emulsifying and homogenising sauces and liquid food products all in one go is the "new kid on the block", says Stephen Davies, md of Pursuit Processing Equipment. It is a technology that was originally developed in Australia as a marine propulsion unit to power boats.

Pursuit Processing Equipment is the sales arm of Pursuit Dynamics, the UK company that bought up the rights to the PDX technology. Having spent five years developing the technology, it launched its first commercial system for the food industry, the PDX Sonic, late last year. So far it has sold 16 units to food companies around the world, including Coca-Cola and AAK in the UK. Another unit capable of processing 12t/h of sauces has just been commissioned for a "very large" UK food processor, with a second one on order.

Most PDX Sonic customers are using the technology to get more throughput from an existing facility, says Davies. But breweries are using PDX for energy saving in pumping and heating the wort, and a number of soft drinks companies are now using the technology to eliminate those dreaded fish eyes.

"The PDX Sonic will mix very difficult-to-mix powders very well," says Davies. FM

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