We have two methods for determining starch levels, the iodine method and the enzyme method.
- Iodine method
The iodine method is a simple field method used to determine the amount of dissolved starch in a filtered sample. The iodine method is based on the fact that the amylose content in starch forms a blue complex with iodine. The higher the concentration, the deeper the blue colour. The relationship between absorbance and dissolved starch is linear up to 100 ppm. The drawback with the iodine method is that it does not provide correct results in all systems, but is usually a good way to follow trends. In some furnishes where bleaching agents are used the blue colour can disappear so quickly that there is no time to carry out a measurement
- Enzyme method
The enzyme method is a more advanced method that provides us with the possibility for determining amounts of adsorbed starch, dissolved starch and total starch content. The enzyme method can be used with both dry and wet samples. The sample is treated with various enzymes in order to break the starch down into glucose. The glucose is then detected using an ion-chromatograph, a liquid-chromatograph or a spectrophotometer. We can obtain a complete picture of the starch chemistry in the wet-end with the enzyme method. The drawback is that it takes a relatively long time before the results are obtained and that the equipment is considerably more advanced.