Starch granules gelatinization

For instance, Soykeabkaew et al. (2004) prepared cellulose liber-reinforced starch-based composite foams (SCFs) by baking process. SCFs were prepared successfully by baking starch-based batters incorporating either jute or flax fibers inside a hot mold. Starch is an alternative material for making foams. Batters of starch and water can readily be baked in a closed, heated mold where the starch granules gelatinize and the evaporation of water causes the starch to foam out and take up the shape of the mold. Foams made from pure starch have major drawbacks on their brittleness and sensitivity to moisture and water. Since both the fibers and the starch matrix were naturally polar and hydrophilic, strong interaction between them was expected. 

The starch granule gelatinization temperature increases in proportion to the extent of cross-linking, while the swelling power decreases (Fig. 4.38). Starch stability remains high at extreme pH values (as in the presence of food acids) and under conditions of shear force. Cross-linked starch derivatives are generally used when high starch stability is demanded. 

Starch is insoluble in cold water, but in hot water the granules gelatinize to form an opalescent dispersion. It is made from corn, wheat, potatoes, rice and other cereals by various physical processes such as steeping, milling and sedimentation. It is used as an adhesive, for sizing paper and cloth, as an inert diluent in foods and drugs, and for many other purposes. 

Fig. 11 Effect of particle size of phenacetin on dissolution of drug from granules containing starch and gelatin. Q, particle size 0.11-0.15mm A, particle size 0.15-0.21 mm , particle size 0.21-0.30mm , particle size 0.30-0.50mm , particle size 0.50-0.71 mm. (From Ref. 17.).

Pea starch granules are oval, sometimes fissured, with a diameter of 20-40 ym (13). Molecular and structural characteristics of the two main components of field pea starch—amylose and amylopectin—are important in determining functional properties (25,26). Smooth field pea starch concentrate contains 97.2% starch of which 30.3-37.8% is amylose (9,23,25-27), and wrinkled pea starch concentrate contains 94.8% starch, which is 64% amylose (26). The gelatinization temperature of smooth pea starch is between 64 to 69 C, and that of wrinkled pea starch is greater than 99 C to 115 C. Gelatinization temperature depends on maturity of field pea seed and amylose content (26,27). 

Gelatinization is described as a transition of starch granules from an ordered state to a disordered state. This chapter critically evaluates and summarizes the "evolution of currently accepted theoretical descriptions of starch gelatinization process. 

Gelatinization, as we understand now, is not only associated with crystalline order, but is also influenced by structural changes in the amorphous region. XRD does not detect or account for the structural changes that occur in the amorphous regions of the starch granules. 

According to Evans and Haisman (1982), there are two phases of water in starch granules (1) the "tightly" bound phase, approximately 20% of the amoimt, absorbed by granules and (2) a "loosely" bound phase that is available for gelatinization. They foimd that the DSC measured onset temperature (Tq) increased rapidly below 0.6 g water per 1 g starch ( 29% water volume fraction) and stayed essentially constant between 0.6 and 2.0 g water per 1 g starch (29-57% water volume fraction) (Eig. 5.10). Changes observed in and Tp, and the peak separation pattern... 

Debet, M. R. and Gidley, M. J. (2007). Why do gelatinized starch granules not dissolve completely Roles of amylose, protein, and lipids in granule "ghosP integrity. /. Agric. Food Chem. 55, 4752- 760. 

Gough, B. M. and Pybus, J. N. (1971). Effect on gelatinization temperature of wheat starch granules of prolonged treatment with water at 50 °C. Starch/Starke 23, 210-212. 

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