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Gluten-free foods

Concept, market and recent developments

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by Ece Ozdemir1, Dilek Boyacıoğlu1, Dilara Nilufer-Erdil1, M. Hikmet Boyacıoğlu2 Food Engineering Department, Faculty of Chemical and Metallurgical Engineering, Istanbul Technical University, Istanbul, Turkey, 2Food Engineering Department, Okan University, Istanbul, Turkey

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he consumption of gluten-free food has being undergoing a remarkable evolution for quite a long time. The major reason is a genetic disorder called celiac disease whose sufferers need to adhere to a strict gluten-free diet. Recent data shows that it occurs in one out of every 100-300 individuals all over the world. Media coverage of the irritating symptoms such as weight loss, skin rashes, fatigue and loss of concentration has increased, which makes gluten an ‘enemy of wellness’. There have also been a considerable amount of gluten-free consumers who are not diagnosed as celiac. They describe themselves as having ‘gluten sensitivity’ and withdraw gluten from their diet. A growing number of gluten-free brands were established and gluten-free private label lines were introduced by retailers around the World. This is thought to have made a great contribution to the gluten-free trend. Thus, due to promotion by retailers, the gluten-free diet as a medical issue has now become a health food marketing concept. In this article, current developments in gluten-free trends, including new gluten-related disorders, and a gluten-free market with labelling and regulatory issues will be examined.

Cereal proteins and toxicity of gluten

Proteins in the cereal endosperm can be divided into four major groups: albumin, globulin, prolamin and glutelin based on their solubilities in water, salt solution, alcohol and acidic or basic solutions, respectively. Prolamin is available in wheat, barley, maize and sorghum in relatively high amounts, while in rice and oats it is present at low levels. Prolamin differs from other protein fractions in its amino acid composition: it includes high amount of glutamic acid and proline while it is deficient in essential amino acids such as lysine. In general, it is believed that the prolamin (gliadin) fraction of gluten is the one which is responsible for celiac toxicity. Even though it is still uncertain which amino acid sequence in wheat gliadin causes celiac toxicity, two tetrapeptides have gained considerable importance recently: proline-serine-glutamineglutamine and glutamine-glutamine-glutamine-proline. It appears that the latter tetrapeptide is present in all three gliadin 48 | Milling and Grain

subfractions and some subunits of secalins, hordeins and avenins found in rye, barley and oats, respectively.

Gluten-free products

Strict adherence to a gluten-free diet, characterised by avoidance of the responsible proteins contained in certain grains, is the only treatment for celiac disease. Grains which should be avoided include wheat, rye, barley, kamut, spelt and triticale. The gluten-free diet involves food products obtained from gluten-free grains including corn, rice, buckwheat, millet, sorghum, amaranth, teff, oats, wild rice and quinoa. A large number of gluten-free cereal products have been produced for celiac patients, including not only breads but also pasta products, cookies, noodles, biscuits, snacks, beer and breakfast cereals. It is important to emphasise that there have been some mechanical and sensorial challenges during production of glutenfree products, as dough lacking gluten is difficult to handle technologically and results in a delicate dough structure and weak mouthfeel. Thus, more research on gluten-free products enables the use of a wide variety of ingredients, including starches, gums, hydrocolloids and dairy products together with prebiotics, other non-gluten proteins or a combination of these, in order to replace the gluten that provides the necessary viscoelastic properties to flour dough. In this way, improved structure and enhanced shelf life, mouthfeel and acceptability of gluten-free products becomes possible. Rice starch, corn starch, gums and thickeners such as locust bean gum and guar gum or dairy ingredients such as powders containing low lactose and high protein content (milk protein isolate and sodium caseinate) are used to overcome quality losses.

Nutritional quality of gluten-free products

Gluten-free cereal products may not offer the same nutritional value as that of wheat-based foods, particularly whole grain or enriched wheat-based foods. This can be attributed to the fact that gluten-free cereals are not fortified and are always obtained by refining flour and/or starch. Since grain foods are a source of B vitamins, fibre and iron, there are major concerns regarding how a gluten-free diet influences the intake of these nutrients. It is still uncertain whether a gluten-free diet is a nutritionally balanced diet or not,