February 20, 2006

Mixing and Blending in the Food Industry

By FOOD Magazine (Australia) Journalist LAINE LISTER.  Published as feature article in FOOD Magazine, February 2006.

REMEMBER that special occasion when Mum's chocolate cake didn't hold together because she was prematurely forced to stop mixing the batter in response to kids demanding to lick the bowl?

If the role of a spatula in the home kitchen can have such an effect, underestimating the role of mixing and blending in food manufacturing is folly.

Such is its integral nature to food processing that it would be difficult to identify a food or beverage that doesn't feature mixing as a core part of its manufacturing process.

Dough batters for breads, chocolate mixes for confectionery, spice mixes, dairy formulations, and wines are just some examples of products where batching and mixing are crucial steps during manufacturing.

Mixing can perform a range of roles for these products including the obvious one of combining multiple ingredients, but can also contribute to modifying the structure of food or beverage mixes.

Mixing and blending can even have a crucial impact on the taste and texture experienced by a consumer when eating or drinking a product.

Ernest Fleming director Arthur Lowenstein says adverse effects from inadequate mixing and blending solutions can also be created in problems during the manufacturing process itself, costing manufacturers time and money.

"If mixing is incomplete or a product 'overmixes' during the mixing process it might start separating," Lowenstein said.

"If the product is being ground and is not done correctly it might become finer than desired, resulting in the wrong texture or even damage to the product."

According to Lowenstein much of the mixing and blending equipment that has been around for some time remains suitable for today's food and beverage manufacturing needs. Examples include ribbon blenders, emulsifiers, liquefiers, and granulators.

With the industry facing growing consumer demand for greater food choices and the consolidation of food operations, Lowenstein cites a move to larger mixing solutions.

"We have seen a trend towards bigger mixers rather than faster mixers," he said.

"Where people used to use a traditional 1000-litre mixer they are now opting for 1500 and 2000-litre mixers.

"Often in the food industry where each batch has to be analysed companies would rather produce a bigger batch than four smaller batches which require four separate processes that cost more and take much longer."

 

Automated mixing

In today's technological age, automation of processes is a key theme in many manufacturing scenarios.

According to Bürkert Fluid Control Systems' managing director Chris Hoey, this is particularly the case in mixing and blending.

"The key to successful mixing and blending is automation," he said.

"The main benefit of automation is quality because ultimately there needs to be high accuracy in batching.

"The food industry is no different to other industries in this regard. When buying petrol it shouldn't be 101 octane one day and 105 octane the next.

"Similarly if there's supposed to be 17% sugar in a yoghurt there should be 17% sugar both today and the following day, not 18.5% tomorrow because the systems vary.

"Repeatability and accuracy are the number one things that automation offers."

With greater focus by today's consumer on nutrition, the requirement for products to accurately match the nutritional labelling places even greater emphasis on the role of mixing and blending solutions.

Increased regulatory focus on product claims also means food manufacturers must achieve consistency and repeatability in the composition of their product mixes.

According to Hoey the case for automated mixing solutions is also made by a greater emphasis today on food safety.

"Blending by hand for food systems that increasingly require HACCP approval is simply not acceptable," he said.

"Not only is it unsuitable in terms of efficiency and man-power, but most importantly in terms of repeatability and for documentation verifying batches and blends.

"There's increasing demand for a documentation trail on everything we do. It's no longer enough just to run a batch.  Rather, we need to generate records to document that the batch ran, whether the pipe was full, where it was delivered and what time and date that was."

 

Sophisticated blending

The increasing plant-level sophistication required to stay competitive in a global food market has also influenced mixing and blending.

This is reflected in the growing application to food manufacturing of studies such as rheology, which analyses the flow of matter.

These efforts attempt to understand the various parameters involved in mixing food such that the process can be controlled to achieve the greatest efficiency and repeatable consistency of the final product. Flow modelling is another technique used to improve understanding of the mixing process.

According to Hoey, the extent of technological development in mixing and blending solutions is reflected in more sophisticated automated solutions than most plant control situations.

"The response times required for successful mixing and blending are totally different to that of a traditional process," he said.

"Consider a vessel that has 300 litres of chocolate and maintaining the temperature of the chocolate by running warm water through a jacket.

"If the warm water is turned off the chocolate temperature may drop half a degree every few minutes.

"Thus for normal process control a one or two second update is quite acceptable.  However; to deliver that same product quickly and precisely to another machine or process may require a response within milliseconds."

Hoey recommends distributed control as the automation solution for mixing and blending scenarios.

"True distributed control offers high speed communication," he said.

"This is the way companies are going by using programmable, distributed IO, with integrated high-speed counters and valve control.

"Thus the batch control occurs in the field rather than having to wait for a central system to process and respond.

One of the key advantages of a mixing solution with distributed intelligence, says Hoey, is that control tasks such as ration batching a sugar mix with water can be done locally rather than reporting back to the main system.

"Another example is a winery system that can make its own decision on coolant delivery based on integrated temperature control with direct valve outputs," he said.

Flexibility

While manufacturers should be encouraged towards automated systems, it is important that these systems remain modular and flexible.

"Older designs featuring hardwiring require huge projects to update systems and change field equipment," Hoey said.

"A flexible design puts the flexibility to change things out in the field."

Another aspect of flexibility required of equipment in many manufacturing plants today is the ability to cater for shorter runs and rapid changeovers.

"In the food industry many companies want mixers that are easy to switch over and easy to clean," Ernest Fleming's Arthur Lowenstein said.

Lowenstein says that while currently available equipment can handle demand for quick changeovers, the nature of the work performed by mixers also requires diligence from manufacturers.

"For example, ribbon blenders aren't too bad in terms of switchover times, but there can also be a few catch points that require more thorough cleaning."

As with all manufacturing machinery technological developments potentially make the job easier, but safety nevertheless remains a necessary focus.

"Many users aren't aware of the safety features of blenders and where they have improved," Lowenstein said.

"Simpler designs, covering up the drive end, and protecting the discharge and feed ends - these are features today that were not done properly in earlier mixers."