Starch damaged

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. 

Damaged starch is also more readily degraded by enzymes. The ability to absorb water is the most important property of damaged starch since it adds to the ability of flour to absorb water. If all the starch in a flour is undamaged then only the protein will absorb water. 

It should be appreciated that a high level of starch damage is not essential in bread. French bread is made from soft wheat flour with a low starch damage. Starch damage is generally undesirable in biscuits. In biscuits the product is cooked to a very low moisture content so binding in water is undesirable. 

The desirability of damaged starch varies between products, in some products damaged starch is desirable while in others it is undesirable. Even in bread too high a starch damage is undesirable as product quality suffers. 

It is not particularly easy to measure the degree of starch damage present. The usual method involves treating the flour with a-amylase, which can only attack the damaged starch. The procedure requires an a-amylase preparation that has to be standardised. Alternatively, an estimate can be made by optical microscopy or by calculating from the water absorption of the flour and its protein content, assuming that the water absorption that exceeds that to be expected from the protein alone is due to the damaged starch. 

Once any directly fermentable sugars have been used up the yeast can only be fed by sugars produced from the starch. The only starch that can be broken down is the damaged starch. This explains why a certain amount of starch damage and some amylase activity is desirable in a bread flour. 

The preference for low protein, low starch damage flour in biscuits is obvious when the role of protein and damaged starch as water binders is considered. The aim in making biscuits is to produce a low moisture food. Incorporating components that bind water makes that aim more difficult. Table 2 considers the relative properties of biscuit and bread flours. 

Wheat <Dairy products> starch, protein, moisture, ash, hardness, damaged starch, a-amylase activity, amino add, color value, ratio of contaminated bran, bread making quality, discrimination of cultivar... 

Damaged Starch in Flours Analysis by Enzymatic Vs Imaging Methods... 

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-... 

Fungal amylase has a widespread application in bread baking. As it is inactivated at lower temperatures when compared with malt- and bacterial- amylases, it can only convert damaged starch into fermentable sugars, which are used by the yeast to produce carbon dioxide and alcohol. 

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). 

P. L. Finney, J. E. Kinney, J. R. Donelson. Prediction of damaged starch in straight-grade flour by near-infrared reflectance analysis of whole ground wheat. Cereal chem 65 449-452, 1988. 

Most bread recipes include diastatic barley malt flour. Diastatic malt contains high levels of a- and P-amylases and proteases that mainly hydrolyze damaged starch granules and proteins, respectively. These enzymes gradually and slowly provide substrate for the fermenting of yeast. Diastatic malt is especially important in those formulations where sugar is not used, such as in French breads. Many commercial hard-wheat flours are supplemented with diastatic malt in order to adjust their diastatic activity, usually measured by the falling number assay (Chapter 15). The quantities used vary from 0.1% to 1.25% (Doerry 1995, Kulp and Ponte 2000, Stauffer 1990). 

Dye test used to differentiate between native and gelatinized and damaged starch. Undamaged native starch granules do not stain, whereas damaged or gelatinized granules stain red. 

Damaged starch is the portion of starch that is mechanically disrupted. Starch damage is based on susceptibihty to a- and ()-amylases or amyloglucosidases. Undamaged starch granules are resistant to ()-amylase, while damaged counterparts are attacked at a measurable rate. 

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