With just the change of a nozzle, snack producers can create a filled pretzel of different sizes and shapes. Source: Handtmann

Just the right fill
In filled pretzel production, the outer dough jacket is extruded and injected with filling at the same time in a coextrusion system. Pumping consistently and measuring the exact amount per pretzel nugget, stick or loaf helps minimize any issues related to inconsistent product quality.

“With these products, you have to keep the filling under control,” Mr. Eshelman said. “You have to keep it locked within the dough jacket, and that’s a challenge in and of itself.”

Pump speed controls the proper amount of filling that goes into the dough jacket. Snack producers must determine the ratio of dough mass to filling mass — a common ratio being 60% filling and 40% dough — and pump rate is determined by that ratio.

“Typically, a customer comes in and tells us, ‘I want as much filling as possible,’ but when they see the amount of filling they can put in there, they always back off because it’s typically the most expensive part of the equation,” Mr. Giacoio said.

Those ratios can change at the push of a button on Rheon USA coextruders.

“Some of our equipment will go from 10 grams to 300 grams per piece with an infinite amount of adjustability within the ratio,” he continued. As long as the dough has the extensibility to handle the amount and type of filling, Rheon’s coextruders can deliver a wide range of dough-to-filling.

Handtmann’s coextruders use servo motors to give operators ultimate control over even the slightest changes in the ratio.

“If you need more filling, we can slightly increase the ratio because it’s a servo filler and we control how much we’re delivering,” said Cesar Zelaya, bakery sales and technology manager, Handtmann.

Once the ratios and pump speeds are decided, this can largely be left alone with minor tweaks. Visual cues will alert operators to under- or over-filling.

“If you start to see blowouts, you’re either over-filling them or the integrity of the crimp seal has been lost on the cutter,” Mr. Eshelman said. “If you start to see collapsed products, it’s quite possible you’re under-filling them.”

Choosing the pumping mechanism is a different animal. Not all pumps work with all fillings, and testing is critical for finding the right pump for each product.

“There are a couple of different styles of positive displacement pumps, and we have several different types in our technical center, but we’ve found there is no one pump that does it all,” Mr. Eshelman said.

Suppliers of fillings are often in RBS’s technical center testing their products on the equipment and the pumps to qualify the materials for pre-baked filling applications, he said. Mr. Eshelman also encouraged pretzel producers to test their own products to determine the appropriate pump and settings to ensure accurate weights as well as other processing parameters.