 |
||||||||||||||||||||||||
 |
||||||||||||||||||||||||
 |
|
|
  GLUTENBackgroundThe principle grain used for flour is wheat. Whole wheat flour contains the entire wheat kernel, whereas for white wheat flour; the flour is separated from the bran and germ. The protein and starch content of flour, provides baked flour products with its body and structure.Protein makes up about 12% of the dry wheat kernel. Traditionally, wheat protein has many classifications, but we are emphasizing the soluble and insoluble distinction. Wheat proteins can be divided into four main classes; globulins, albumins, gliadins and glutenins.1 Albumins and globulins are soluble proteins. But approximately 85% to 90% of the proteins in white flour are insoluble in water, and these insoluble proteins are divided into the two fractions gliadin and glutenin. Gliadins (28-42%) are the major prolamin protein (prolamin is a group of similarly structured proteins) in wheat, and are soluble in 70-90% alcohol. Glutenins (42-62.5%) are the major glutelin proteins in wheat, soluble in dilute acid or alkali solutions.2,3,4,5 A single variety of wheat may have over 40 different gliadin proteins, but glutenins are more difficult to characterise, so their exact numbers are unknown.6 By some definitions, gluten is found only in wheat, yet the term gluten is commonly used to refer to any similar prolamin protein in any grain that is harmful to a sensitive individual.3,7,8,9 Along these lines, the Codex Alimentarius defines gluten as “a protein fraction from wheat, rye, barley, [oats] or their crossbred varieties and derivatives thereof, to which some persons are intolerant and that is insoluble in water and 0.5M NaCl."10 According to this definition, gluten is a protein complex inherent in wheat, but by other definitions gluten is formed by gliadins and glutenins when flour is moistened with water and thoroughly kneaded or mixed. 11 During gluten development the glutenin molecules are stretched out in linear chains. Through a number of chemical reactions sheets are formed around gas bubbles. During the early stages of processing, the gliadin and glutenin fractions adhere to each other and become aligned alongside each other to form gluten. Hydrogen bond formation will takes place, and at this stage the dough will be more resistant to mixing.6 Starch granules are entrapped by the developing gluten, which probably interacts with lipids and other dough components as well.11 The gliadin, a syrupy substance that binds the gluten mass together, is responsible for the viscous properties of dough, because gliadin has little or no resistance to expansion. Glutenin, on the other hand, contributes to elasticity, through resisting expansion. It exhibits toughness and rubberiness. Gluten development during kneading is important for providing structure and strength for the dough and the finished product and is primarily responsible for both the viscous and elastic characteristics of wheat flour dough.11 Gluten can be extracted from a flour-and-water dough by washing with water to separate the starch granules and other soluble material from the gluten. The extracted gluten has cohesive and elastic properties.6,10 Wheat flour contains between 7 and 12% gluten proteins by weight.7 Other grains such as rye, barley, oats and triticale (wheat-rye hybrid) each contain their own prolamins, which cause the same intestinal damage in sensitive individuals that the gliadin fraction in wheat gluten causes. This is due to the similarity in protein structure. The following is a list of the type of prolamin in each grain and the percentage that the prolamin contributes to the grain's protein content: • Wheat: Gliadin (69%) It is the amount of gluten (prolamin protein) in a product that determines whether a sensitive individual will be affected. Corn, rice, and other cereal grains such as sorghum, millet, teff, ragi, Job’s tears, buckwheat, quinoa and amaranth, can safely be ingested by a person with Celiac Disease (CD), for whom gluten would be harmful. Wheat, barley, rye, spelt (which is often used as a replacement for wheat) and kamut, however, contain prolamin and should be avoided in CD.9,12 The safety of the ingestion of oats has been, until recently, quite controversial. However, oats were found to be safe and well tolerated by adults with Celiac Disease, though the risk of wheat contamination of commercial oat products remains a cause of concern.13,14
ProblemsAdverse reactions (by Karen du Plessis, registered dietitian):
Adverse reactions to wheat can be divided into immune reactions, such as allergy and Celiac Disease (CD) (gluten sensitivity) and non-immune reactions, e.g. intolerance. The immune system is capable of a number of reactions, e.g. allergy- and cellular reactions. An allergic immune reaction to wheat can be caused by any protein in wheat, including gluten. Celiac disease (CD) (gluten sensitivity) is a non-allergic immune reaction to gluten. Intolerance is usually due to enzyme deficiency. Wheat allergy involves an immune reaction to one or more of the proteins/allergens found in wheat or wheat-containing foods or to the inhalation of or contact with flour that contains wheat, e.g., baker’s asthma.1,2,4 Wheat allergy is more prevalent in certain groups: in the baking industry wheat allergy is responsible for occupational asthma in up to 30% of individuals.17 The majority of wheat allergies involve the albumin and globulin fractions of wheat, but one can also have an allergy to the gluten. Gluten can also result in an allergic reaction upon contact. It has been shown to cause atopic dermatitis in workers exposed to it.18,19,20,21 Celiac Disease (or gluten sensitive enteropathy) is a hereditary disorder of the immune system. The ingestion of gluten induces inflammation of the intestinal mucosa and atrophy of the villi. This can result in the inadequate absorption of nutrients such as proteins, carbohydrates, fats, vitamins, minerals, and, in some cases, water and bile salts. The disease is permanent, and damage to the small intestine will occur every time gluten is consumed, regardless whether symptoms are present or not.2,8,16,17,22,23,24,25It has been reported that as little as 0.03 grams (30ppm) of ingested gluten can trigger symptoms.26 CD is one of the most common life-long disorders in certain countries. CD is frequently under-diagnosed, particularly in adults, who may present with only subtle symptoms.17 In some countries the incidence is as high as 1 in 200 (Sweden). It primarily affects caucasians of northwestern European decent and rarely affects Africans, people of Mediterranean extraction or Asians. It affects twice as many females as males.24,27 It was thought that Celiac disease affects less than 1 in 2500 children in the United Kingdom, but in a recent study (2004) it was found that at age 7, 1 % of children have subclinical celiac disease. Less than 0.1% of these children were reported to be on a gluten-free diet.28 There is no consistent set of symptoms. There are "classic" symptoms (diarrhoea, bloating, weight loss, anemia, chronic fatigue, bone pain, and muscle cramps), but CD frequently presents with other symptoms. In some cases only one symptom is experienced (e.g., anemia, a run-down feeling, or behavioural problems).16 CD usually develops in childhood but can begin at any age. Typically the disease presents at the age of 6-24 months, after wheat has been introduced into the diet, or in early adult life (the 30's and 40's).17,24,27,29 Sometimes the disease exists from childhood but symptoms appear only in adulthood. Enteropathy associated T-cell lymphoma (a type of cancer) is widely recognized as a complication of CD, and gluten restriction has been shown to decrease the risk of this malignancy to the level in the general population. This circumstance renders appropriate treatment of CD crucially important.30 For further details read more in Allergy Advisor Educational Review: Food Problems: The additive L-cysteine is sometimes used in flour as a treatment agent to aid in the relaxing of gluten in doughs, such as pizza bases, that are heavily manipulated. In controlled amounts, it will break the sulfhydryl bridges between gluten proteins, producing weakened flour. With an excess amount however, dough will be converted into a slimy substance.6 For a “gluten-free” claim to be made on a food product, the product must be tested to determine whether the gluten content is below the level set in the relevant regulations. The Enzyme-Linked Immunosorbent Assay (ELISA) test is used to determine the amount of gluten present in a product. Even if wheat or gluten is not an ingredient in a food product, it can be present as a “hidden” allergen. This can occur through cross-contamination or gluten can be “hidden” in one of the compound ingredients used in the product. Developing gluten-free products can be challenging. Often flours such as rice flour, tapioca flour, potato starch or cornstarch are mixed together in an attempt to lend the same characteristics to a product as gluten would. Xanthum gum or guar gum is often added to gluten-free baked products, to prevent them from crumbling. The availability of non-grain flours, such as bean-, amaranth- and buckwheat flour has improved gluten-free baking.31 In many countries these substitute ingredients for wheat (gluten) are expensive and not freely available. It can be time consuming and troublesome to source these ingredients, especially for small-scale manufacturers.
Labelling IssuesWheat and gluten may appear under various names in a product’s ingredient list, such as “filler” or “thickener”. Ingredients such as hydrolysed vegetable protein or hydrolysed protein can be derived from wheat as well as from other sources.15 Codex is leading with the regulation that wheat-derived ingredients need to be identified in the ingredient list, to protect allergic or intolerant individuals, and many countries are following. In some countries, such as Canada, the labelling regulations state that a product must contain 20ppm gluten or less in order for a claim to be made that the product is gluten-free. Other countries are very seriously considering adopting this regulation. For now, however, 200ppm remains a widespread permitted gluten level internationally. The Codex Alimentarius Commission has not made a final decision in this regard but this topic is receiving a great deal of attention. A gluten-free product must be prepared in accordance with Good Manufacturing Practice (GMP) to avoid contamination. On the product label, the term “gluten-free” must be written in the immediate proximity of the name of the product. For a gluten-free claim to be made for a product, the product must be tested to determine its gluten level. For the determination of gluten level, the Enzyme-Linked Immunoassay R5 Mendez (ELISA) Method must be used.7
Food AlertsAvian influenza (“bird flu”) The outbreak of Avian influenza (“bird flu”) in regions in of South-East Asia and North America has caused a great deal of panic worldwide. Avian influenza (“bird flu”) is an infectious, potentially fatal disease. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. The virus is highly contagious and readily transmitted from farm to farm by mechanical means, through, for example, contaminated equipment, vehicles, feed, cages, or clothing. The virus can survive for long periods in the environment, especially at low temperatures. Strict sanitary measures on farms can, however, give some degree of protection.32 There are concerns that “bird flu” could be spread through contact with contaminated dead poultry, in addition to direct contact with live infected animals. To date, there is no information to suggest that the disease can be transmitted through contaminated food. Some countries have put trade restrictions in place, however, even though there is no evidence that products shipped from affected areas can be the source of infections in humans. The European Union and UK has banned all chicken imports from Thailand, and other countries in South-East Asia. 32 Japan has suspended the import of chicken from America.The WHO are working toward confirming or refuting the known facts about transmission, but present the organization does not conclude that any processed poultry products (, including refrigerated or frozen carcasses, products derived from these, and eggs) in or arriving from areas currently experiencing outbreaks of Avian influenza pose a risk to public health. It is nevertheless important to emphasize the importance of good hygiene practices during handling of poultry, particularly hand washing, prevention of cross-contamination and thorough cooking.33
TrendsSoy based foods and ingredients Even though soy derivatives are being used in food, there is a demand for more and a better variety of food products made from soy, such as beverages and snack foods. Soy based products is not only for vegetarians, but many milk or wheat allergic individuals will use these products, as well as any individual trying to lead a healthy lifestyle. It is important to ensure that the soy being used in a product is not contaminated with, for example wheat. Contamination often occurs during transportation and storage. This is especially important if you claim that your product is wheat-free.
New Products
Journal ArticlesChitin - the undisputed biomolecule of great potential "Of the truly abundant polysaccharides in Nature, only chitin has yet to find utilization in large quantity. Chitin is the second most abundant natural biopolymer derived from exoskeletons of crustaceans and also from cell walls of fungi and insects. Both chitin/chitosan and their modified derivatives find extensive applications in medicine, agriculture, food, and non-food industries as well. They have emerged as a new class of physiological materials of highly sophisticated functions. Their application versatility is a great challenge to the scientific community and to industry. All these are the result of their versatile biological activity, excellent biocompatibility, and complete biodegradability in combination with low toxicity. Commercial availability of high-purity forms of chitin/chitosan and the continuous appearance of new types of chitin/chitosan derivatives with more and more useful and specific properties have led to an unlimited R&D efforts on this most versatile amino polysaccharide, chitin to find new applications, which are necessary to realize its full potential." Chitin--the undisputed biomolecule of great potential. Editorial comment: Chitosan is being used in certain dietary supplements, especially those for weight control. It assists with fat binding. Studies so far have shown that it is effective only in animals, not in humans. Mycotoxins in infant cereal foods from the Canadian retail market Mycotoxins in infant cereal foods from the Canadian retail market. Methods for allergen analysis in food: a review. Methods for allergen analysis in food: a review. Editorial comment: Food and Allergy Consulting and Testing Services (F.A.C.T.S), with its team of experts and other specialized resources in food safety and adverse reactions, offers allergen testing and labelling advice.
Compiled by Maritza van DykFACTS REFERENCES |
|
||||||||||||||||||||
 |
||||||||||||||||||||||||
