Granules, of starch

Pregelatinized starch is sometimes used as a coating binder,258 but these products are difficult to wet out uniformly and may cause problems due to clumping. Small granules of starch are used in specialty coatings.259... 

Drying and granulation of starches Drying and granulation of by-products and wastes. 

Starch is a white powder, having a peculiar slippery feel, or it appears in short columnar masses. The granules of starch differ in size and appearance according to the kind of plant from which they have been obtained. They are rounded or egg-shaped masses, having at the centre or toward one end a spot, called the hilum, around which are a series of concentric lines more or less well marked. Differences in size, shax)e, and markings of starch granules are shown in Pig. 40. 

Granules of starch are found in the interior of the vascular bundle (Figure 9.4). Silica bodies are also found in great number on the fiber strand. They attach themselves to circular craters which are spread relatively uniformely over the strand s surface. The silica bodies are hard, but can be dislodged mechanically. The removal of silica bodies leaves behind perforated silica-crater, which would enhance penetration of matrix in composite fabrication leading to interfacial adhesion stronger [25]. A compilation of the chemical composition and physico-mechanical properties of oil palm fiber... 

Starches are quite hydrophilic and the granules swell in water to several times their volume. In the preparation of starches for coating, the granules are heated at 93°C to ensure complete breakdown. The starch is then mixed with the pigment while it is fluid. Normal practice is to coat the paper at an elevated temperature to help control viscosity. 

Hydroxyethyl group introduction at low DS results in distinct modification of physical properties. Among these are decreased gelatinization temperature range (126), increased granule swelling rate (127), and decreased abiUty of starch pastes to gel and retrograde. 

The performance of several Sephacryl gel combinations is illustrated by results achieved for glucans from different types of starch granules. The applied Sephacryl gels of Pharmacia Biotech (15) are cross-linked copolymers of allyl dextran and N,N -methylene bisacrylamide. The hydrophilic matrix minimizes nonspecific adsorption and thus guarantees maximum recovery. Depending on the pore size of the beads, ranging between 25 and 75 im in diameter, aqueous dissolved biopolymers up to particle diameters of 400 nm can be handled. 

FIGURE 16.1 Preparative SEC of short-chain (scb) branched glucans of small" (<3S /u.m) starch granules of potato species Ostara separated on Sephacryl S-1000 (88 X 2.6 cm) eluent 0.005 M NaOH the normalized chromatogram (area = 1.0) was constructed from an off-line determined carbohydrate content of succeeding 5-ml fractions flow rate 0.67 ml/mln V d = 185 ml, V, = 460 ml fraction I high dp fraction fraction 2 low dp fraction. 

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