Application Requirements for Starch

Dispersions of starch have found wide use in papermaking and paper conversion due to their unique properties, viz., low-cost renewable adhesive, controlled viscosity, specific rheological characteristics, water-holding properties, electrostatic charge, film formation and bonding after drying. 

Starch is a natural product and as such is not uniform. Type, genetic variety and environmental factors of soil quality and weather during the growing season for the starch source may influence the rheological characteristics of the product. Additional 

The viscosity of a starch paste is often characterized differently by the starch manufacturer and by users in the paper industry. In the manufacturing plant, viscosity tests serve to control the starch modification process. As an example, the test is used to determine when to terminate a starch oxidation reaction for viscosity reduction. In the paper mill, viscosity testing is required to characterize the flow properties of starch-based coating formulations. 

Starch pastes obtained by heating in a recording viscometer are seldom completely dispersed, but are a mixture of granular fractions and dispersed molecules. The kinetics of phase transition of native and modified starches are analyzed by DSC.55 

Frequently used single-point viscosity tests in the starch plant are orifice pipettes,56 orifice funnels,57 the Hot Scott viscometer, and various methods to determine alkaline fluidity.58 For absolute measurements of the rheological properties, rotating viscometers with coaxial cylinders are used.59 The paper industry uses mainly the Brookfield viscometer and the Hercules viscometer for determining shear-dependent viscosity, pseudoplasticity, and thixotropy. Oscillatory and capillary viscometers are used for more detailed viscosity characterization, such as yield value, elastic properties, and viscoelasticity.60 

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An interesting possible application in our society is in super absorbers, which are currently made with polyacrylates, but these suffer from poor biodegradability. Since the demand for short-use super absorbers is growing, a product with a short lifetime and therefore a quick and safe disposal is required. Carboxylated starch can be such a product, but first, an efficient method to oxidize starch needs to be developed. Currently used methods produce stoichiometric amounts of waste products, so the search for a catalytic process is ongoing. 

Starch blends have better physical and mechanical properties than pure plant based polymers, which open up more application possibilities. For example, starch blends can produce film with better moisture barrier protection and higher clarity. Also in film packaging made from starch blend, the perforations that are normally required can be dispensed with because the optimum moisture content soon establishes itself automatically, even in freshly packaged fruit and vegetables. 

Comments. The method described is applicable to starch- and protein-rich tissues. For starch-poor tissues much less aqueous DMSO is required. For protein-poor tissues the PAW treatment may be omitted, but it should be borne in mind that in such cases the adsorbed detergent, some pigments, and small amounts of residual proteins would be removed by the subsequent aqueous DMSO treatment. The yield of CWM depends on the type of tissue from 100 g fresh parenchymatous (or immature) tissues the yields of dry CWM are as follows potatoes (1.0—1.2 g), runner beans... 

Xylan-degrading enzymes, especially xylanases, have considerable potential in several biotechnological applications. In some processes, the use of purified enzymes is required. However, in other applications, the presence of additional enzyme activities is desired. Commercial applications suggested for xylanases involve the conversion of xylan, which is present in wastes from the agricultural and food industry, into xylose (2). Similarly, xylanases could be used for the clarification of juices, for the extraction of coffee, plant oils and starch and for the production of fuel and chemical feedstocks (3). 

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