Abdel-Aal suggested three mechanisms through which addition of starch influences gluten-free formulations: enhancement of crumb softness, maintenance of the batter consistency during mixing and influencing starch gelatinisation during the baking process. For this reason, the addition of gel-forming starches such as pregelatinised starches and air cell stabilisers such as gums have been suggested as a means to provide gas occlusion as stabilizing agents. Starch gelatinisation could play an important role in gluten-free formulation, due to the ability of starch to form a matrix in which gas bubbles are entrapped, increasing the gas holding capacity of the batters. During the bread baking process starch granules gelatinise i.e., they swell and are partially solubilised, but still maintain their granular identity. On the other hand, Eliasson and Larsson described bread dough as a bi-continuous network of protein and starch. During dough preparation, starch absorbs up to 45% water, based on its own weight and is considered to act as inert filler in the continuous matrix of the dough. Cereal starches are usually considered gelling materials, and in baking they significantly contribute to texture and overall acceptability of cereal-based foods. In addition, other minor components of starch, such as proteins and lipids may be present. The starch biosynthetic pathway generally results in two types of glucose polymers being formed, the linear amylose and the high branched amylopectin. The size, shape and molecular arrangement inside the granules depend on the plant species, and the genetic-environment interactions. Native or raw starch occurs in the form of granules. Corn, cassava, sweet potato, wheat, and potato are the major sources of food starch, while sorghum, barley, rice etc., serve as minor source of starch in different parts of the world. Starch is obtained from a variety of plant sources. This is dependent on the interaction with other ingredients in the formulation and the type of food product. In gluten-free products, starch is incorporated into the food formulation to improve one or more of these properties. They are used as gelling, thickening, adhesion, moisture-retention, stabilizing, film forming, texturizing and anti-staling ingredients. In addition to their nutritive value, starches are widely used as ingredients in many foods to impart textural and overall acceptability. It provides 70%–80% of the calories consumed by humans worldwide. Starch is the primary source of stored energy in many plants including cereals, legumes, roots and tubers. Elimination of gluten increases the role and importance of starch in providing structure and texture to gluten-free products. Patients have to follow this diet throughout their life, since re-exposure to gluten can re-activate the disease, even after many years. However, the only treatment for patients with CD is the strict adherence to a gluten-free diet. In bakery products, the gluten network formation is particularly important. Gluten is unique due to its ability to form a visco-elastic network which can retain gas. Gluten-like proteins are the trigger for coeliac disease and are found in wheat, rye and barely. CD is one of the most common food-induced diseases in humans, causing inflammation of the small intestine due to the uptake of gluten and gluten like proteins. However, the true number of people suffering from CD is expected to be higher. Patients diagnosed with coeliac disease (CD) make up 1% of the world population. The emphasis of this review is on starch and its properties with respect to the quality of gluten-free products. This review covers a number of topics relating to starch including an overview of common and lesser researched starches chemical composition morphology digestibility functionality and methods of modification. In gluten-free products, starch is incorporated into the food formulation to improve baking characteristics such as the specific volume, colour and crumb structure and texture. Starch plays an important role in the formulation of bakery products and has an even more important role in gluten-free products. The starches can additionally be modified increasing or decreasing certain properties of the starch, depending on the application. The extent of these properties varies depending on the starch source. Starch is used as gelling, thickening, adhesion, moisture-retention, stabilizing, film forming, texturizing and anti-staling ingredient. When gluten is removed from a flour, starch is the main component left. The replacement of gluten in cereal-based products remains a challenge for scientists, due to its unique role in network formation, which entraps air bubbles. The increasing prevalence of coeliac disease (CD) and gluten-related disorders has led to increasing consumer demand for gluten-free products with quality characteristics similar to wheat bread.
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