Starch mechanical damage

Another altered starch is damaged starch, which is purely mechanically modified starch. This is starch whose granules have been damaged in the milling process. The important property of damaged starch is that, unlike undamaged starch, it absorbs water in the cold. 

Several dye coloration scales are used to characterize starch varieties. Perhaps the oldest is the differentiation between starches based on the uptake of Saphranin and Gentiana Violet (see Table XXXVIII).787 Co-vello788 presented another coloration scale which is based on the use of six common acidic and basic dyes (see Table XXXIX). Like the Saphranin and Gentiana Violet dyes, these dyes adsorb directly on starch. Table XL presents a list of synthetic dyes tested in starch dyeing.789-790 Zwikker791 observed the reactions of mechanically damaged starch granules and amylo-... 

The main factors to bind liquids and/or to influence the consistency of the dough are wheat glutens, pentosanes and mechanically damaged starch (through the grinding process of the com) or hydrocolloids (for example thickeners). 

Clear fiour Name of the low-quality wheat flour obtained in the last stages of the milling process (last reduction rolls). The flour has lower quality in terms of color, mechanically damaged starch, and higher amounts of ash and fat. When a patent flour is fabricated, the clear flour is removed from the straight-grade flour. 

Modified starches tend to swell more after contact with water due to a weakened granular structure. Their suspensions have higher viscosity, lower maximum suspension solids and a slower settling rate. Suspension solids and viscosity are also affected by mechanical starch damage during drying. 

The decrease in expansion seems to occur at moisture levels above 30°/o moisture for both cereal (starch-based) polymer systems, and protein (soy grits). This corresponds to a point on their adsorption curves where water activity rises rapidly with added moisture that is, at a level where the water added to a mix has little effect on primary hydration of polymers, but behaves as a diluent. In mechanical terms, this may be explained by proposing that at above levels of 25°/o-30% water plasticisation of the polymers is complete, and further added water acts as a lubricant, reducing the shear-induced temperature rise and particle damage necessary for the formation of homogeneous melts. 

In summary, the effect of dextrans can be positive or negative depending on the cell type, bioreactor or even dextran grade and make used, but all experimental evidence so far suggests that dextran offers no mechanical protection. Dextrans and modified starches should not be used as protectants against shear damage. 

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