Mixing and blending are among the most universal aspects of food production. Whatever food or beverage you can think of, there’s a good chance that somewhere along the line, to make it, something (or many things) had to be mixed or blended.
And with universal application comes universal concerns. Ask suppliers of mixing and blending equipment what their customers want, and they’ll run through the litany of general food processing priorities: sanitation, high throughput, flexibility, consistency, digital capability, etc.
The priorities may be universal, but they’re also changing in emphasis, says Gary Seiffer, sales specialist at EnSight Solutions (www.ensightsolutions.us), owner of the Likwifier brand of high-shear mixers.
“The concerns have shifted, and we have shifted with them,” Seiffer says. “Homogeneous blending in quick order is paramount as food producers look to increase capacities with what they have – all the while upping quality levels.”
According to Matthew Hartman, senior automation sales engineer at Blentech (www.blentech.com), the trend is away from homogeneous, do-it-all equipment and toward more specialization.
“We have seen a shift in thinking,” Hartman says. “In the past, we have seen our clients looking for equipment that can do it all. Today we see [them] asking for highly optimized processes designed for a particular family of products to maximize quality and minimize cost at the same time.”
One of the biggest imperatives is high throughput, which can be tricky. As a line’s or plant’s throughput increases, the mixing and blending operations must keep pace. But this can be a problem for two reasons. Mixing and blending have to be done thoroughly and can’t be rushed – at least, not without the right equipment. And mixing and blending usually are inherently batch processes, involving fixed quantities that have to come together in exact proportions.
One way to increase throughput in batches is simply to increase the batch sizes, which means upgrading the equipment’s capacity. This can be done by using several mixing receptacles, arranged so that a batch is always being worked on, says Ken Langhorn, technical director at Charles Ross & Son Co. (www.mixers.com).
“A buffer tank or a second batch tank can be utilized to provide a steady output,” Langhorn says. “When a change can-style mixer is utilized, multiple interchangeable mix vessels can be utilized to accomplish this. Often, a change can mixer will be operated with three vessels: one mixing, one discharging and one being cleaned and prepped for the next batch.”
However, there are applications where batch mixing and blending just won’t keep pace with production requirements. That’s where inline options come into play. Basically, they offer more capacity with less footprint and less steel.
“Processing from an inline perspective provides mainly process oriented advantages,” says Lee Holliday, regional sales manager for IKA-Works Inc. (www.ika.com/en). “For instance, large production volume requirements lend very well to inline processing. Space requirements can become an issue in facilities where several large vessels are needed to meet production demands. The addition of an inline process can significantly reduce the space required, without compromising the quality.
"An additional benefit can be realized in reduced labor related to personnel need for charging raw ingredient or cleaning,” he adds.
Inline mixing can have processing advantages, especially when a solid, usually a powder, is being combined with a liquid in which it is immiscible (i.e., the powder won’t dissolve in the liquid). This requires the solid and liquid to come together as a suspension, a situation often seen in viscous products such as dips, dressings and sauces.
A common arrangement is an in-line, high-shear mixer that uses a rotor immersed in a pipeline. The difference between the speed of the liquid in the middle of the rotor and its speed at the tip creates shear, or flow force. The shear can be enhanced by the addition of a stator, a sleeve that encloses the rotor and heightens the liquid’s flow as it exits. The high shear creates an environment in which powder or immiscible liquid can be dispersed with maximum efficiency. (High-shear mixing can also be done on a batch basis, with the rotor mounted on the bottom of the tank.)
Once the product has been blended, a common way to keep it that way while it’s being passed along for further processing or packaging is to put it through high-shear pumps. However, those can be hard to clean, making product changeovers more problematic, and many processors are trying to do without them, Seiffer says.