Starch damage, measurement

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. 

The same functions used in agriculture can be applied to processed foods. In baked goods, wheat gluten, various additives, starch damage, and water absorption are just some of the parameters measured [21-24]. Dairy products are also important and often analyzed by NIR. Moisture, fat, protein, lactose, lactic acid, and ash are common analytes in the dairy industry [25-28]. 

Figure 8.1.1 shows that the first point of NIR analysis in a typical mill is for the testing of wheat at intake. This was the first application of NIR in the flour milling industry. In addition, automated systems based on whole-grain NIR are available for the control of wheat blending. The next opportunity for a control system would be in the reduction system. Here, an NIR measurement of flour starch damage would provide the opportunity (not yet realized) to implement a feedback control of the... 

It must be concluded that NIR is not applicable to the prediction of flour baking quality and is of limited use for measurement of ash. However, it may be used on a routine basis for measurement of protein, moisture, starch damage, water absorption, particle size, and color. 

Starch damage due to faulty storage or sprouting can be determined via hydrolysis with a-amylase or indirectly determined by a measurement of the viscosity of a slurry prepared from the ground grain or flour. The lower the viscosity, the greater the starch damage. 

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. 

One of the problems highlighted in recent times is the importance of fiber in the diet. Normal starch is rapidly broken down into simple sugars by enzymes (amylases) in the human body. A high consumption of starch can lead to spikes in blood sugar level. The rate and extent of this rise are measured by the glycemic index. To avoid sharp fluctuations, which are thought to be damaging to health, inclusion of a certain amount of fiber in the diet is recommended. 

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). 

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