Gelatinised starch

One of the important properties of starch is that it undergoes gelatinisation. Starch is insoluble in cold water and intact starch granules do not absorb cold water. However, it is possible to prepare a dispersion of... 

The role of the enzymes is three-fold. Firstly there is the use of very thermostable df-amylases to pre-thin the gelatinised starch, reducing its viscosity so that it can be easily handled and further processed. This process is conceptually very similar to many other commercial uses of hydrolases, especially proteases and glycosidases. Pre-thinning takes place at 105°C and the thermostable df-amylase from B. licheniformis actually has a temperature optimum of almost 100°C. 

Pre-gelatinised starch 5-10 Cold water-soluble, so easier to prepare than starch. 

Their properties are similar to those of seaweed gums and the term is often applied to aqueous suspensions or solutions of gums and gelatinised starches. 

Otey has studied the interactions between the ethylene-acrylic acid (EAA) copolymer and gelatinised starch since 1977 [7-83]. 

Formulations based on thermoplastic starch, EAA and PE in different ratios, are suitable for film production. In Table 8.1 a few examples of such compositions (some of them also containing polyvinyl alcohol (PVA)) with their related tensile strength properties are reported. As can be seen, the film obtained with a gelatinised starch level of about 50% shows good tensile properties. 

Takagi S, Koyama M, Kameyama H, Tokiwa Y, (1994) Development of PCL/ Gelatinised starch blends and tbeir enzymatic degradation , in Biodegradable plastics and polymers, Y Doi, K Fukuda (eds), 437. 

Commercial water-resistant starch based bioplastics are produced by using fine molecular blends of biodegradable synthetic polymers and starch. These materials are made with gelatinised starch (up to 60-85%) and hydrophilic synthetic polymers (e.g. ethylene vinyl alcohol copolymer) or hydrophobic synthetic polymers (e.g. polyeaprolactone or Ecoflex ) and compatibility agents (Fritz et al., 1994). The most important starch based material on the market is proposed by Novamont as Mater-Bi . 

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