There’s been plenty of innovation in the snack world recently, led by the proliferation of healthy options that are shaking up the category. These include plant-based and gluten-free alternatives, as well as snacks packed with more protein, less sugar, functional benefits and more. 

“Snack companies and their R&D departments are consistently coming to us asking for ways to make more and innovative better-for-you (BFY) snacks,” noted Nico Roesler, North American pretzel & snack equipment sales manager, Reading Bakery Systems (RBS). “The big thing is functional snacking: adding ingredients that not only provide protein or other nutrients to a diet but also taste great.” 

While consumers are snapping up the BFY snacks that hit these marks, these foods can push production to the limit. 

“Snack makers are working very hard to use ingredients that are considered healthy without compromising the taste and texture that make people want to eat them when snacking,” explained Dave Nichols, vice president of sales and marketing, Volkmann USA. “But the gluten-free, sugar-free and plant-based demands put quite a burden on food engineers and processors to replicate the same properties.”

To ease this burden, producers are turning to the latest extruders that can process even the trickiest ingredients, textures and shapes of today’s snacks.

BFY snacks often feature emerging ingredients like pulses, seeds and alternative and ancient grains, all of which can be obstacles when extruding.

“Whether a particular ingredient will pose a challenge depends on its level of starch, fat, oil, moisture content, etc.” said John Barber, sales manager, US and Canada, Clextral USA. “For example, when working with high-protein recipes, pulses, or fruit and vegetable ingredients, obtaining a quality shape, or a desired level of expansion can be a challenge. For ingredients with higher levels of fat, the challenge is finding the right balance for the desired crunch, or hardness and expansion.” 

Heat is often the biggest consideration for bakers looking to achieve the perfect texture for their healthier extruded snack, Mr. Roesler noted. 

“Pulses tend to break down and burn at low temperatures compared to corn,” he said. “For something like peas, operators need to know the different acceptable temperatures and how higher temperatures cause the ingredient to react in an extruder. Pea flour and protein can change state from good to firm very quickly in an extruder, causing units to get blocked and then burn ingredients.”

These plant protein blends and other alternative powders also tend to flow through the extruder more difficultly and require a delicate process, said Sharon Nowak, global business development manager, food and pharmaceutical industries, Coperion and Coperion K-Tron. 

The company’s Actiflow, for example, is a real-time vibration device mounted externally to the feeder but directly tied to its loss-in-weight signal, detecting any changes in the extrusion process. 

“If the feeder experiences a bridge or rat-hole and little or no material is being sent to the screws, the ActiFlow vibration is activated, and the bridge breaks,” Ms. Nowak explained. “After the weight signal is stable again, the vibration is deactivated, preventing additional packing that may sometimes occur with traditional vibration devices.”

Another trend that can challenge extruders is larger particulate or inclusion size.

“People are trying to incorporate larger pieces, whether it’s fruits or nuts, to get more product definition and a better appearance,” said Ken Hagedorn, vice president of the bakery sector for Handtmann. 

When extruding these larger and potentially more delicate inclusions, snack producers need a process that won’t break them down or diminish final product quality. One possible solution is a vane cell pump. 

“Other extrusion systems tend to smear or break ingredients like blueberries, and eventually the dough will start to change colors,” he said. “With the vane cell technology, we really don’t get that breaking up of the particulates.”

Similarly, Reiser’s Vemag double-screw pump can transport product without damaging larger particulates. For snack bar production, Reiser’s bar extruder attachment ensures consistent size and weight, and a waterwheel flow divider can also be added for multilane production. 

Bakers must also ensure these large particulates don’t end up drying out the dough and making it difficult for the extruder to process them, he added. 

Coperion K-Tron’s new vibratory feeder is also ideal for these inclusions, Ms. Nowak said. The patent-pending vibratory drive ensures accurate mass flow without any attrition. The company also offers a new Smart Glide Finishing (SGF) anti-stick surface treatment that can prevent sticking and glazing of certain ingredients. This is another common issue bakers encounter with certain BFY snack ingredients. 

“For example, if you add a 3/8-inch nut piece, as opposed to a 3/8-inch apple piece, they’re the same size, but the apple passes through really easily because it tends to be slippery, whereas a nut is very dry, and you can have a harder time getting it through the system,” Mr. Hagedorn explained.

With so many potential challenges when extruding, it’s critical to understand how to adjust a process to handle a variety of BFY ingredients. 

Because alternative ingredients may be more sensitive to heat, it’s important producers consider when to introduce water to the extruder, as well as its temperature, Mr. Roesler noted. He recommended that operators introduce room temperature or chilled water. 

“Then, when managing the temperature of the barrel and screw, we recommend lowering the temps in the cooking zones by turning heaters off,” he said. “The temperature from the friction inside the extruder will naturally rise but not to boiling point or to the point of negatively affecting the process. Then, the die face is heated externally, and the product’s starches will rapidly expand as it is extruded through the hot die face plate.”

The screws of RBS’s high-pressure extruder are built in small interchangeable parts. Each section is roughly 5 inches long and can be added or removed depending on the product. 

“For alternative ingredients like pulses, operators can arrange a screw design to add friction and reduce slip back,” Mr. Roesler said. “For corn, they can use a screw arrangement that allows more slip back, and they can add heating elements if required.”

Clextral’s Evolum twin-screw extruders offer Advanced Thermal Control, a self-learning system that ensures a precise temperature in each barrel of the extruder, improving energy efficiency and stability when extruding heathy snack ingredients, Mr. Barber noted. 

Certain ingredients may require adjustments to the conveying system transferring them to the extruder as well, including alterations to air flow or reduced conveying velocity, Mr. Nichols noted.

“This way, very sensitive ingredients can be protected during the vacuum transfer and more durable ingredients can be allowed to flow faster,” he said. “The Volkmann conveying system is fitted to the hopper of the extruder, and when the extruder is ready for more material, it signals the Volkmann controller to automatically transfer more material from storage to the extruder hopper for feeding. This minimizes the need to adjust the extruder when feeding these ingredients.

Manufacturers will also turn to co-extrusion when making the latest BFY filled products like snack bites and bars. John Giacoio, vice president of sales, Rheon USA, noted that the company’s co-extruders are built to handle a wide variety of new and more delicate ingredients and can be easily adjusted, capable of extruding up to four different materials. 

“The basic shape that our co-extruders make are ball and stick shape, but we have many options and attachments to make these filled products into almost any shape,” he said. “We have heat stampers to make an impression, half-moon stampers and many more forming and shaping options. We also offer automated panning systems that easily connect to these machines.

Snack makers are also implementing twin-screw extrusion lines to improve product quality, flexibility and throughput. 

“Twin-screw extrusion technology versus single screw allows you to manage the expansion for an array of ingredients, especially more fatty, oily, wet and sticky type ingredients,” Mr. Barber said. “This is much more difficult if not impossible on single-screw extrusion technology.”

Making innovative products with these extruders thankfully does not typically require new technology, he added. 

“New products can be made on the twin-screw extruder by making adjustments in process parameters, dies, screw profile, barrel length, specialty shape production kits and more,” he said. “In other cases, we can make new products by changing upstream or downstream equipment.”

For example, Clextral offers a variety of “clip-on auxiliaries” that can be added and removed for downstream operations as needed, including die face cutting for curl or ring shapes and co-extrusion die for filled snacks. 

Handtmann’s vane cell pump systems also promote flexibility as vanes can be added or removed, providing a variety of chamber sizes when extruding. 

And the modular design of Coperion K-Tron’s extrusion barrel and screws means the process can be adapted to the special needs of emerging ingredients. The Coperion ZSK food extruder’s outer to inner working screw diameter ratio of 1.8 and screw speed of 1,800 RPM enable it to process a wide range of raw materials and ingredients at high capacities.

This article is an excerpt from the December 2022 issue of Baking & Snack. To read the entire feature on Extrusion, click here.