Wheat-gluten uses and industry needs L. Day ab * , M.A. Augustin ab , I.L. Batey bc and C.W. Wrigley bc & a Food Science Australia, Werribee, VIC. 3030, Australia (Tel.: C61 3 9731 3233 fax: C61 3 9731 3250; e-mail: li.day@csiro.au) b Value-Added Wheat CRC, North Ryde, NSW 1670, Australia c Food Science Australia, North Ryde, NSW 1670, Australia Gluten, the dough-forming protein of wheat flour, is the key to the unique ability of wheat to suit the production of leavened products. The past five decades have seen the rise of gluten as a commodity in its own right, through the large- scale industrial separation of wheat starch from gluten, plus the controlled drying of the gluten so as to retain its functional properties. The resulting Vital Dry Gluten is most widely used in bakery products. However, gluten (vital, de-vital or modified) is finding increasing use as a food ingredient to provide a range of functional properties at a more modest price than competitors such as milk and soy proteins. Introduction Gluten may be defined as the ‘cohesive, visco-elastic proteinaceous material prepared as a by-product of the isolation of starch from wheat flour’. A further definition might include the genes involved in the synthesis of the gluten proteins in the developing grain—the Gli-1 and Gli-2 loci coding for the gliadin proteins, plus the Glu-1 and Glu-3 loci, coding for the glutenin polypeptides (Gianibelli, Larroque, MacRitchie, & Wrigley, 2001). A biological definition might include the origins of the gluten–protein complex as being derived from the ‘storage proteins of the wheat grain’ (Shwery & Halford, 2002). Such definitions are correct but there is more to tell. The most significant aspect of the gluten story for the food industry is the importance (and the potential) of gluten as a commodity, sold for a wide range of uses around the world. In its most familiar form, gluten is traded in the dried state as ‘Vital Wheat Gluten’. In this form, the functional properties of wheat gluten may be regenerated by rehydration. In addition, many products are derived from gluten by various forms of modification, thereby suiting them to a wide range of value-added uses. The proteins that form gluten are storage proteins, according to their function for the wheat grain (Shewry, 1999). The grain also contains the residue of many metabolic proteins (mainly water-soluble) that have been needed by the developing grain, together with the proteins providing those putative mechanisms that must carry life on into the next generation of the wheat plant when the germination process commences (Shewry, 1999). This is the basic context in which we should see the storage proteins, not as the dough-forming gluten proteins, but as the grain’s storage proteins laid down specifically to provide an essential supply of amino acids for the developing plant. In these respects, the storage proteins of the mature wheat may not differ much from those of other grains (Shwery & Halford, 2002). However, the distinctive feature that makes wheat unique is the visco-elastic properties of its storage protein. When the grain is milled and mixed with water, what was ‘merely storage protein’ forms a dough with unique rheological properties, capable of retaining gas bubbles, suiting this dough to the wide range of products we have come to expect from wheat flour. It is these properties that make wheat alone suitable for the preparation of a great diversity of food products— breads, noodles, pasta, cookies, cakes, pastries and many other foods. It is also these unique properties that account for wheat being cultivated by man in such enormous quantities throughout the world. The name given to this unique group of proteins is ‘gluten’, an enigmatic complex of proteins. Given the unique properties of wheat gluten, it is not surprising that it has been the subject of intense attention by the food industry. That interest has extended to the commercial separation of gluten from the starch and soluble proteins of flour. In fact, it is the cohesive properties of gluten that makes its commercial prep- aration a relatively simple process. ‘Vital Wheat Gluten’ is now a significant ingredient in the food industry and 0924-2244/$ - see front matter Crown Copyright q 2005 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.tifs.2005.10.003 Trends in Food Science & Technology 17 (2006) 82–90 Viewpoint * Corresponding author.