Specialty starches

The US corn wet-milling industry is represented by the Corn Refiners Association, Inc., a Washington, DC-based trade association which provides technical, regulatory, legislative and communications support for its members. 

Starch in its native form is a versatile product, and the raw material for production of many modifications, sweeteners and ethanol. Starting in the 1930s, carbohydrate chemists have developed numerous products that have greatly expanded starch use and utility. 

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A specialty starch is defined as one where some form of chemical modification takes place to give properties to the starch that are lacking in the native product. The remainder of this paper will discuss the chemistry of modification and the chemical and physical reasons for the use of specialty starches in treating paper. 

This paper will also assume that the reader has basic starch and cellulose knowledge and that it is not necessary to review the structure of the molecules. It is, however, important to know that starch from native, non-genetically selected sources, is a mixture of two molecules and not simply one compound. Amylose is an essentially linear molecule and differs from amylopectin, which has about 4-6%oC-(l—>6) branches, even though both molecules are mainly o4 -(1—>4) linked D -glucose. The differences in these two molecules and their chemical modifications are the basis of application technology and the reason for the growing importance of specialty starches. 

The physical nature of the products produced by these processes is the principal reason for the growing use of specialty starches. 

Another factor is the need for thinner viscosity binders. This puts a heavy demand on the water holding property of the starch. A retrograded starch will result from a non-derivative made to a low viscosity. Specialty starches are providing the properties needed... 

Before discussing specialty starches for size press applications, it should be noted that the largest volume of starch applied at the size press is either enzyme converted or ammonium persulfate hydrolyzed native corn starch. These are economic considerations and the properties resulting from these treatments do not compare to the properties provided by specialty starches. It is also fair to state that all grades of paper do not require a specialty starch and it is only through the need for improved paper performance that specialty starches are required. 

The dominant specialty starch used in size press applications is the hydroxyalkyl derivative commonly made wjth ethylene oxide to yield a hydroxyethyl starch. Low substituted hydroxypropy1 starch has similar properties. These starches were introduced to the industry in 1950 and they have grown in importance each year. Recent expansions in production by major producers has indicated their continuing dominance of the specialty starch surface sizing and coating field. 

Many coatings will use latex as a binder either singly or in combination with starch. Addition of specialty starch allows cost control and depending on the quality demanded, the level of starch can be varied. Many formulas will use 16 to 18 parts of binder based on the clay and frequently ratios of 5 starch and 12 latex are used. 

As a native starch, lipids and protein residuals are significantly lower than they are in many other commercial starches. These properties of tapioca starch have been utilized in many industries and further enhanced by means of physical and/or chemical modifications which give close control of its properties to fit the needs of customers in process and product applications. However, tapioca starch is regarded as a specialty starch outside of its local production area. 

For most corrugating applications, unmodified com starch is used. Specialty starches are being offered for increased corrugator speed or better warp control through minimizing the amount of water added to the board. Hydroxyethylated com starch will... 

It is conceivable that methodology such as that used to increase starch quantity could be used to influence starch quality by manipulation of starch synthase and branching isoforms. These new starches may have greater usefulness in food and industrial processes. The production of modified "specialty starches via molecular biology techniques is promising, and perhaps more beneficial and more economical than the chemical modification of starch for industrial purposes. 

CORN PRODUCTS Specialty Starch Products(Continued) Product by Trade ... 

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