Swelling starch

Starch is the main thickener in gravies, sauces, and puddings. It absorbs water, and becomes a gel when cooked. As the starch swells up with water, the amylose leaches out, and the amylopectin forms the gel. Some starches have higher amylopectin content and make better gels than those containing large amounts of amylose. 

Desired organoleptic properties, particularly textural ones, are a direct consequence of these microstructural changes. A chip must be firm and snap easily when deformed, emitting a crunchy sound (Krokida et al., 2001a), whereas in thick products the better the contrast between a rich and soft inner structure and a crispy outside, the better the product (Moreira, 2006). Firmness is often related to starch swelling and gelatinization, as well as to the stability of pectic substances of the cell wall and middle lamellae. 

Uses of partial-waxy and waxy wheat in Asian noodles, bread and tortillas have been reviewed.269,270,298 French bread made from double-null partial waxy wheat flour retained 1-2% more moisture in its crumb in 24 hours compared to bread from a wild type flour. French bread made from the mutant wheat had a softer crumb immediately and up to 48 hours after baking.299 Wheat noodles are made from flour and low levels of salts, so starch plays a major role in noodle quality. Flours from partial waxy wheats with —10% protein and 21-24% apparent amylose (starch basis) are favored for white salted (sodium chloride) noodles because partial waxy starch swells during cooking somewhat more than non-waxy wheat starch. For good appearing noodles, the flour should be from a white wheat low in polyphenol oxidase, and... 

The mechanism of action of disintegrating agents has been the subject of some debate. Some substances such as starch swell when they come into contact with water, and disruption of the tablet structure has been attributed to this. However, other effective disintegrants do not swell in this way, and are believed to act by providing a network of hydrophilic pathways inside the tablet through which water can diffuse. Irrespective of the precise mechanism of disintegration, it is clear that water uptake into the tablet must be the first step in the disintegration process. ... 

Solubility practically insoluble in cold ethanol (95%) and in cold water. Starch swells instantaneously in water by about 5-10% at 37°C. Polyvalent cations produce more swelling than monovalent ions, but pH has little effect. Specific surface area ... 

Starch granules are insoluble in cold water, but when a suspension in water is heated the granules swell and eventually gelatinise. On gelatinisation, potato starch granules swell greatly and then burst open cereal starches swell but tend not to burst. 

Martin, M.L., Zeleznak, K.J. and Hoseney, R.C. (1992) A Mechanism of Bread Firming, ly Role of Starch Swelling (in press). 

The main causes for the improved moisture resistance exhibited by the nanocomposites are the less hydrophilic nature of cellulose and the geometrical impedance created hy the C-NW, the constraint of the starch swelling due to the presence of the C-NW network, the resistance of the diffusion of water molecules along the nanofiUer—matrix interface, and the reduced mobility of the starch chains, resulting from an increase in the Tg or the ciystaUinity. 

Starch Swells (translucent) Soluble >80°C Deep blue No effect... 

These are used for bottle labeling. They are prepared by treating waxy starch or waxy fluidity starch with caustic under high shear. The starch swells in the caustic, and most of the caustic is neutralized with nitric acid. One formulation yields a final composition of 39% starch (40 fluidity waxy), 3% urea (an additive), 3% sodium nitrate (from the sodium hydroxide and nitric acid used), and 56% water (Ref. 10, p. 605). The viscosity as used is about 100,000 cP. The labels are cold water resistant. 

Starch form is basically made of carbohydrates (CgHioOs), found in many vegetables. When heated in water, starch swells into granules which disperse to a gel form. Modification with tacldlying inorganic salts, fillers, and plasticizers is necessary for obtaining useful adhesive forms. 

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