Snack and bakery extrusion companies seek flexibility ...

Flexibility, greater sanitation, gentle handling of ingredients, quicker changeovers, more precise weight control, and the ability to make products with healthier ingredients are top of mind features and benefits for snack and bakery customers of extrusion equipment and technology.

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Market demands

'Customers do not want dedicated equipment anymore,' says John McIsaac, vice president of strategic business development for Reiser, Canton, MA. 'They do not want dividers that produce only one type of product.' Flexibility is the key, he notes, along with gentle handling.

Jeff Zeak, bakery specialist with Reiser, adds that customers want superior finished product quality, portion weight control accuracy, ease of machine use and sanitation, low cost of ownership, and flexibility of equipment capability.

Customers of Buhler Group, Uzwil, Switzerland, don't expect many global changes in twin-screw extruder, aside from sanitary improvements, says Michael Shaw, sales manager, North America, extrusion, snacks and cereals. 'They want less flat surfaces'more rounded. Things like that,' he says.

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Greater uptime with fewer changeovers are among the most frequent requests from customers of Franz Haas Machinery of America, Inc., Williamsville, NY, says Kevin Knott, key account manager. Weight control is also paramount, especially considering the cost of ingredients, he says. 'We're reducing giveaway by hitting the weights more precisely.'

Rick Warner, director of sales, American Extrusion International, South Beloit, IL, says his customers want equipment that can handle higher percentages of plant-based protein and/or multigrain recipes. 'There is a general trend to meet the demand for healthier snacking options,' he says.

Customers of Andy J. Egan Co., Inc., Grand Rapids, MI, seem increasingly interested in toppings on products that provide higher nutritional content, says Mike Sherd, managing partner. 'We've sprinkled anything from sesame seeds to dried fruits,' he says. 'A lot of customers will have us top it and then lightly press it into the top of the product.'

Plant protein bases and clean label snacks are high priorities for Jose Coelho, president, Clextral USA, Tampa, FL. 'Our customers are looking to develop new, trendy snacks that are at the same time tasty, healthy, and with ingredient origins and processes that are good for our environment,' he says. 'The good news is that these new ingredients and products do not necessarily require new extrusion equipment or technology, as the twin-screw extruder is highly adaptable and flexible.'

More nutritional snacks and baked goods have been top requests from customers of Baker Perkins, Peterborough, England, says Keith Graham, business development manager. 'Twin-screw extrusion can be utilized to penetrate this expanding market for foods high in fiber and protein. Proteins from wheat, dairy, soy, or pulses, as well as fiber, can be added to co-extruded products.' Gluten-free is another category seeing rapid growth. 'Again, extrusion can help manufacturers respond to demand by using flours from gluten-free grains,' he says.

New and improved

Reading Bakery Systems, Robesonia, PA, has rolled out a co-extruder that can cut in front of the oven, set up with a wire cut mechanism. New in , the Genesis Pro WCS300 encompasses two servos on the feed rolls, four on the wire cut mechanism, three on the cutter and one of the belt, says Sam Pallottini, director of cookie, cracker and pet food sales. 'The design of the machine is capable of doing so much,' he says. 'The biggest feature that separates this from everything else is the linear servo-cutting system that pinches the ends prior to the bake.' That enables the user to construct miniature bite-sized pastries.

Reiser has introduced several new technical advances in recent months, starting with a 33 percent larger infeed for double-screws on the Vemag divider, McIsaac says. 'This means less work on the dough as it flows into our exclusive double-screw pumping system,' he says. 'It allows our customers to expand the types of variety breads they can offer. They can produce higher-volume breads. They can produce both a closed or open crumb structure with the same machine.'

For smaller producers, Reiser has introduced the V2 cutter, a servo-driven portioning system that increases production rates on Vemag 500 series machines. 'The servo drive eliminates pneumatics, and improves on our benchmark scaling accuracy,' McIsaac says. Reiser also has partnered with Gemini to produce full rolls lines, dividing them directly into the pan and using a horizontal discharge system to replace vertical chutes. 'We have full control of the dough ball from divider to pan,' he says. 'Teamed with a Vemag divider, it allows the high-speed production of sort rolls and profitable hard or hybrid rolls on the same system.'

Reiser has also added line extensions for its Vemag MMP223 high-speed cutting device for protein and meal-replacement bar extrusion portioning; the BC236 and BC237 ball control machines for production of sphere and multi-shaped, high-protein, and Keto-friendly snacks and pet food treats; and the multi-lane co-extrusion servo crimper system for filled products like bagel bites, calzones, empanadas, and breadsticks, Zeak says.

Buhler Group has been promoting its AeroExpander unit that's mostly sold internationally to U.S.-based snack managers looking to produce pellet-based snacks. Available in three sizes, the main benefits are that it's horizontal and provides both low-pressure and high-pressure extrusion. 'Instead of the traditional way of a rotary drum'with pellets bouncing all over the place, and some over-popped, and some under-popped, and you don't get a lot of consistency'in the bucket you get very consistent airflow, very consistent exposure to heat, and uniform popping,' Shaw says. 'It's an inexpensive way for a smaller company to get into the snack and cereal business.'

Franz Haas, which is part of Buhler Group, has developed a machine, called the , with a removable head that's used to make higher-end high-protein bars, which allows quick changeovers, Knott says. 'We developed a system to take the extrusion head offline onto a cart, put a second one back on, so they can be up and running within 20 minutes, instead of a two- to four-hour shutdown,' he says. Developed originally for a particular customer, the has since been sold to others, he adds.

Andy J. Egan Co. produces machines to handle extruded bars, and primarily does custom builds, Sherd says. Recent custom machines have included direct-drive motors with no gears, parts that can be removed without tools for easy cleaning, and a lack of bolt holes to go with the lack of bolts'which cuts down on places that could harbor bacteria, he says. The company's new four-roll co-extruder reduces product changeover time and adds flexibility. It also can be adapted for use as a two-roll extruder when single-layer products are required.

Baker Perkins has enhanced its wirecut extrusion machines with weight control technology that's added to the profitability of cookies and bars, reducing variations in piece weights by individually adjusting the output from each die cup, Graham says. 'The savings in dough and waste, and the economic benefits, are significant,' he says. 'These wirecuts cover a wide range of cookie and bar applications for high-fat soft doughs.'

The latest TruClean servo wirecut from Baker Perkins offers a combination of automation and economy, Graham says. 'Outstanding flexibility and process control are key attributes of the patented two-axis servo system,' he says. 'Tailored profiles can be treated for each individual product and loaded at the touch of a button, improving ease of operation, product changeover times, cleaning, and maintenance.'

Known for its single-screw and rotary-head extruders that make sheeted chips, co-extruded snacks, sticks and three-dimensional shapes, American Extrusion has brought to market its first twin-screw extruder, Warner says. 'New items in addition to the twin-screw extruder are a tube cutter that cuts various lengths of tubes, such as a churro-type product, and an adaptation to our crimping machine that makes green pea pods,' he says. 'Our technology focuses on keeping the process simple and easy to operate, while allowing a lot of flexibility in terms of raw material usage.'

Clextral has worked on developing snack lines designed to be flexible for rapid product changes when running high capacities without losing production efficiency, Coehlo says. 'Particular attention to sanitary design and higher capacities were integrated into our clip-on equipment that makes new snack product shapes post-extrusion, and also equipment to add ingredient inclusions in the extruded melt,' he says. 'These developments will allow our customers to build their new product portfolios, using existing lines without major investments and following the latest operational sanitary requirements.'

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Extrusion in food processing consists of forcing soft mixed ingredients through an opening in a perforated plate or die designed to produce the required shape. The extruded food is then cut to a specific size by blades. The machine which forces the mix through the die is an extruder, and the mix is known as the extrudate. The extruder is typically a large, rotating screw tightly fitting within a stationary barrel, at the end of which is the die. In some cases, "extrusion" is taken as synonymous with extrusion cooking, which cooks the food with heat as it is squeezed through the die.

Extrusion enables mass production of food via a continuous, efficient system that ensures uniformity of the final product. Products made through extrusion (without simultaneous cooking) include pasta, breads (croutons, bread sticks, and flat breads), pre-made cookie dough, and sausages. Products made through extrusion cooking include many breakfast cereals and ready-to-eat snacks, confectionery, some baby foods, full-fat soy flour, textured vegetable protein, some beverages, and dry and semi-moist pet foods. Food products manufactured using extrusion usually have a high starch content.

Process

Extrusion cooking

In the extrusion cooking process, raw materials are first ground to the correct particle size, usually the consistency of coarse flour. The dry mix is passed through a pre-conditioner, in which other ingredients are added depending on the target product; these may be liquid sugar, fats, dyes, meats or water. Steam is injected to start the cooking process, and the preconditioned mix (extrudate) is then passed through an extruder. The extruder is a large, rotating screw tightly fitting within a stationary barrel, at the end of which is the die.[1] The extruder's rotating screw forces the extrudate towards and through the die. The extrudate is in the extruder for the residence time.[citation needed]

Many extruded products puff and change texture as they are extruded because of the reduction of forces and release of moisture and heat.[1] The extent to which it does so is known as the expansion ratio. The extrudate is cut to the desired length by blades at the output of the extruder, which rotate about the die openings at a specific speed. The product is then cooled and dried, becoming rigid while maintaining porosity.[citation needed]

Cooking takes place within the extruder, where the product produces its own friction and heat due to the pressure generated (10'20 bar). The process can induce both protein denaturation and starch gelatinization under some conditions.

Many food extrusion processes involve a high temperature for a short time.[1] Important factors of the extrusion process are the composition of the extrudate, screw length and rotating speed, barrel temperature and moisture, die shape, and rotating speed of the blades. These are controlled based on the desired product to ensure uniformity of the output.[citation needed]

Moisture is the most important of these factors, and affects the mix viscosity, acting to plasticize the extrudate. Increasing moisture will decrease viscosity, torque, and product temperature, and increase bulk density. This will also reduce the pressure at the die. Most extrusion processes for food processing are carried out at low to intermediate moisture (moisture level below 40%). High-moisture extrusion is known as wet extrusion, but it was not used much before the introduction of twin screw extruders (TSE), which have a more efficient conveying capability. The most important rheological factor in the wet extrusion of high-starch extrudate is temperature.[2]

The amount of salt in the extrudate may determine the colour and texture of some extruded products. The expansion ratio and airiness of the product depend on the salt concentration in the extrudate, possibly as a result of a chemical reaction between the salt and the starches in the extrudate. Colour changes as a result of salt concentration may be caused by "the ability of salt to change the water activity of the extrudate and thus change the rate of browning reactions". Salt is also used to distribute minor ingredients, such as food colours and flavours, after extrusion; these are more evenly distributed over the product's surface after being mixed with salt.[3]

History

The first extruder was designed to manufacture sausages in the s.[4] Dry pasta has been produced by extrusion since the s,[2] and the method has been applied to tater tots (first extruded potato product: Ore-Ida in ).[4] Some domestic kitchen appliances such as meat grinders and some types of pasta makers use extrusion. Pastry bags (piping bags), squeezed by hand, operate by extrusion.[citation needed]

The first extrusion cooking machine was the expanding pelleting machine from Wenger Mixer Manufacturing from . Its first mentioned use seems to be with Purina in , which developed extruded food for dogs, monkeys, and fish.[4][5] In , the USDA and UNICEF tested a full fat soy flour produced from extrusion-cooked soybeans as a source of nutrients for children. Milk substitutes were later developed from this flour. In , the US government started providing a CSM (Corn-Soya-Milk) formula to protein-deficient children in the Third World. The later Meals for Millions project also prominently featured soy flour in its Multi-Purpose Food (MPF), a high-protein food supplement that could be made for just three cents per meal.[5]

The idea of using extrusion cooking to produce breakfast cereal has been mentioned since the Wegner patent of . In , the Israeli Shefa Protein Industries introduced a line of breakfast cereal called Krunch, made from cereal flour and full-fat soy flour. It's unclear whether there has been an earlier breakfast cereal made from extruded products.[5] Meat analogues have been made through extrusion since .[5]

Effects

Extrusion enables mass production of food via a continuous, efficient system that ensures uniformity of the final product. This is achieved by controlling various aspects of the extrusion process. It has also enabled the production of new processed food products and "revolutionized many conventional snack manufacturing processes".[6]

Chemical changes with cooking

Extrusion cooking results in "chemical reactions that occur within the extruder barrel and at the die" like most other forms of cooking.[7] Extrusion enables mass production of some food, and will "denature antinutritional factors"[1] while destroying toxins or killing microorganisms. It may also improve protein quality and digestibility[1] and affects the product's shape, texture, colour, and flavour.[1] Changes associated with extrusion include:

• Destruction of certain naturally occurring toxins and antinutrients (including trypsin inhibitors, haemagglutinins, tannins and phytates)[1][8]
  • All four listed antinutrients reduce the absorption of protein. Phytate and tannins also reduce the absorption of minerals.[8]
• Reduction in the level of microorganisms in the final product.[1]
• Partial destruction of heat-liable vitamins (A, B, C, and E).[1][8]
• Moderate increase in protein digestibility, due to protein protein denaturation and the inactivation of antinutrients.[8]
• Maillard reactions, which reduce the available amounts of certain amino acids, including the essential amino acid lysine.[9][10] Lysine loss can be reduced by using wetter mixtures.[7]
• Breakdown of complex carbohydrates (starches and non-starch polysaccharides) into simpler components. Part of this action is caused by amylase from the cereal themselves.[2]
  • This increases glycemic index and creates starches more likely to cause and insulin resistance. The "extrusion process significantly increased the availability of carbohydrates for digestion".[11]
  • This may also lead to higher tooth decay.
  • On the other hand, this breakdown converts insoluble fibers into soluble fibers.[7]
• Binding and volatization of flavor compounds.[7]
• Gelatinization of starch.[7][12]
• An increase in iron content due to the wearing of machine components. No significant change in zinc absorption.[7]
• As of , little is known about the stability or bioavailability of phytochemicals involved in extrusion. Phenols appear to be decreased.[7]

Overall, the effects of "extrusion cooking on nutritional quality are ambiguous",[8] as extrusion may change carbohydrates, dietary fibre, the protein and amino acid profile, vitamins, and mineral content of the extrudate in a manner that is beneficial or harmful.[8] Nutritional quality has been found to improve with moderate conditions (short duration, high moisture, low temperature), whereas a negative effect on nutritional quality of the extrudate occurs with a high temperature (at least 200 °C), low moisture (less than 15%), or improper components in the mix.[8] High-temperature extrusion for a short duration "minimizes losses in vitamins and amino acids".[1]

A research paper indicates that use of non-traditional cereal flours, such as amaranth, buckwheat or millet, may be used to reduce the glycemic index of breakfast cereals produced by extrusion.[13] The extrudate using these cereal flours exhibits a higher bulk and product density, has a similar expansion ratio, and has "a significant reduction in readily digestible carbohydrates and slowly digestible carbohydrates".[13] A paper states that replacing 5% to 15% of the wheat flour and white flour with dietary fibre in the extrudate breakfast cereal mix significantly reduces "the rate and extent of carbohydrate hydrolysis of the extruded products",[11] which increased the level of slowly digested carbohydrates and reduced the level of quickly digested carbohydrates.[11]

Texture

The material of which an extrusion die is made can affect the final product. Rough bronze dies on pasta extruders produce a rougher surface than smooth stainless steel dies, considered to make more liquid pasta sauces adhere better;[14] pasta made this way is labelled "bronze die" pasta to indicate a premium product.[15]

• Pasta dies
• Front of a die for making elbow macaroni
• Back of the same plastic die
• Old metal dies for pasta, showing bottom and top of the dies

Products

Extrusion has enabled the production of new processed food products and "revolutionized many conventional snack manufacturing processes".[6]

The various types of food products manufactured by extrusion typically have a high starch content.[1] Directly expanded types include breakfast cereals and corn curls, and are made in high-temperature, low-moisture conditions under high shear. Unexpanded products include pasta, which is produced at intermediate moisture (about 40%) and low temperature. Texturized products include meat analogues, which are made using plant proteins ("textured vegetable protein") and a long die to "impart a fibrous, meat-like structure to the extrudate",[4] and fish paste.[16]

• Cheese curls, a directly expanded snack food
• Pasta, an unexpanded food
• Meat alternative, a texturized food

Some processed cheeses and cheese analogues are also made by extrusion. Processed cheeses extruded with low moisture and temperature "might be better suited for manufacturing using extrusion technology" than those at high moisture or temperature. Lower moisture cheeses are firmer and chewier, and cheddar cheese with low moisture and an extrusion temperature of 80 °C was preferred by subjects in a study to other extruded cheddar cheese produced under different conditions.[17] An extrudate mean residence time of about 100 seconds can produce "processed cheeses or cheese analogues of varying texture (spreadable to sliceable)".[18]

Confectionery made via extrusion includes chewing gum, liquorice, and toffee.[16] Other food products often produced by extrusion include some breads (croutons, bread sticks, and flat breads), various ready-to-eat snacks, pre-made cookie dough, some baby foods, some beverages, and dry and semi-moist pet foods. Specific examples include cheese curls, macaroni, Fig Newtons, jelly beans, sevai, and some french fries.[19]

Extrusion is also used to modify starch and to pellet animal feed.[citation needed]

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See also

• Flash pasteurization

References

Further reading