Extrusion Processing: New Whole-Grain Opportunities

As research continues to prove the value of whole grains as a vital part of a healthy diet, health organizations around the world are recommending that people consume whole grains in their daily meals. Since 1999, FDA has allowed manufacturers of foods containing at least 51% whole grains to make a label claim in reference to the foods role in reducing the risk of heart disease and cancer. The public is well aware of these health benefits, contributing to the commercial success of whole grain foods. However, there is confusion by consumers about the difference between whole grains and fiber. Whole grains and dietary fiber have been independently recognized to provide the same health benefits, which leads to the confusion. But, there is a difference.
Whole grains typically contain the three layers of the grain: bran, germ and endosperm. The bran is particularly rich in dietary fiber, and many fiber-enriched foods contain only this portion of the kernel. The germ (the kernels center) holds most of the vitamins, minerals and fatty acids. In between lies the endosperm, which contains some vitamins and minerals and most of the starch. Thus, whole grains provide fiber and starch, plus protein, antioxidants, fatty acids and phytochemicals, which have been credited with reducing risk of diabetes and heart disease. This article describes the incorporation of the whole grainendosperm, bran and germinto extruded products.
Five years ago, whole grain-enriched foods were mostly found in the nutrition bar and diet cereal categories. Today, whole grains are found in breakfast cereals, snack foods, co-extruded products, flatbreads, pasta products and more. While most whole-grain foods are made from flour or meal that contains all three layers of the kernel ground together, a current trend is to use visible whole grains to give a natural look and authentic mouthfeel to the finished product.
Twin screw extrusion gives processors a flexible tool to create a new palette of healthy whole-grain foods that taste greatcrispy, expanded products with open cell structure; much different than traditional whole-grain formulations that exhibit heavier texture and denser mouthfeel. A good example of a healthy whole-grain product with high consumer appeal is the multigrain chip. The unique processing technology of the twin screw extruder provides a production environment not possible in the single screw extruder; the intermeshing screws create necessary micro-mixing, combined with intricate regulation of temperature and pressure within individual barrel modules, to successfully produce market-quality multigrain chips that are a hit with consumers. Up to 100% whole-grain formulas are transformed into palatable foods using twin screw technology. This is accomplished by varying the ingredient mix and the processing parameters including temperature, pressure, screw speed and configuration, which are different for each product.

Whole-grain possibilities
Extrusion processing can lead to an array of whole-grain products.

Expanded snacks and breakfast cereals: Using twin screw extrusion, processors can create a variety of healthy expanded snacks and breakfast cereals. Extrusion makes it possible to produce crispy, expanded products with an open cell structure that is much different than traditional whole-grain formulations that exhibit a heavier texture and denser mouthfeel. This is accomplished by varying the ingredient mix and the processing parameters. In this area, improvements in technology are literally reshaping these products. Advances in die and cutter designs are giving processors an entirely new set of templates for creating innovative product shapes.  Plus, recent developments in extruder design and control allow more textures and density combinations; for example, light texture with visible inclusions.

Filled snacks: Filled (co-extruded) snacks have crisp cereal shells and soft fillings that delight consumers of all ages.  Processors can incorporate whole-grain flour into the cereal shell of sweet or savory coextruded products, adding a healthy benefit to these consumer favorites. Pre-engineered dies let processors create many shapes, such as bars, pillows, nuts, balls and triangles. Fillings range from fruit purée, jelly or creams for sweetened snacks, to cheese and meat for savory products. 

Breakfast cereal and flaked snack products: Today, consumers munch on cereal flakes for breakfast and between-meals snacks. Manufacturers can use twin-screw extrusion to make whole-grain flakes for breakfast cereals or add this healthy component to snack blends. Twin-screw extrusion offers an economical alternative to traditional processing of corn, wheat, rice or bran into flakes. Other advantages include: faster manufacturing time (30 minutes for complete extrusion cooking line vs. 6 to 7 hours for traditional process); reduced space requirements; continuous production system that can be automated; quick start-up, shut down and cleaning procedures; ability to switch easily from one product to another; simplified maintenance; greater ingredient flexibility; and higher product consistency.

Crunchy nuggets and inclusions: Breakfast cereal, snack and bakery manufacturers can enhance their products with the nutritional benefits of whole grains in the form of consumer-preferred crunchy nuggets and crisps made by extrusion. These can be added to nutrition bars, breakfast cereals, snacks, granola mixes and bakery products. Inclusions can be designed with specific attributes, such as size, color, flavor, density and texture. The twin-screw extruder processes the whole-grain ingredients at required pressure and temperature to form the dense, crunchy texture, and the die forms the product into the desired shape.

Extrusion opportunities
Development of extruded foods can be complex, especially for the uninitiated. Manufacturers often rely on the expertise of food scientists and engineers in test-plant settings to test and develop whole-grain foods that will win the consumers approval. The goal of the test plants is to streamline the product development process and produce marketable products on a desired timeline. Many R&D centers can supply limited-run products for market evaluation or test marketing. Consumers want it all when it comes to healthy foodsfreshness, flavor and variety. Food manufacturers want processing equipment that can help them supply this dynamic market. Twin-screw extrusion processing technology is a solution, giving processors the processing power and flexibility to produce a wide range of products, continuously, on automated equipment and at high production efficiencies. Extrusion processing advances have enhanced product textures and made it possible to incorporate dramatically increased percentages of whole grains and fiber into products, improving their consumer appeal. With new generation twin-screw extruders and improvements in die-flow design, higher throughputs are available on smaller extruders, optimizing investment and operating costs. 

Mike Shaw works on food extrusion projects and test plant consulting as a regional manager with Clextral , and facilitates co-processor projects for food processors. Shaw holds an engineering degree and an M.B.A. in Marketing, and has 15 years of food industry experience in extrusion, baking and packaging. For more information, email [email protected] .