Basic information

• Potato
  Potatoes are grown for production of starch mainly in Europe and to a minor extent in the United States. Today, starch, is not the only
  raw material extracted from industrial potatoes; both potato protein, potato fibre and fertilisers are extracted at the same time.
• Tapioca
  Tapioca is a very fast growing plant that is primarily grown in Asia and South America. It is the roots that are used for starch extraction, and these roots can be harvested up to three times a year.
• Maize/corn
  Corn is by far the major source of starch in the world. When starch is extracted from the corn seeds there is also oil protein extracted at the same time.

• Wheat
  Wheat is a starch raw material that has grown in importance during the recent years. Wheat gluten (protein) is extracted during the production of wheat starch.
• Legume
  Legumes are for example peas and beans. These plants contain starch and high levels of proteins.

The starches need to be prepared before usage. Our product data sheets contain information of recommended preparation for each product. The most common methods are:

• Jet cooking
  Starch powder and water are mixed to a slurry. The slurry is cooked in a jet cooker at 120-140°C depending on the product and then diluted with water.
• Batch cooking
  Starch powder and water are mixed to a slurry. This slurry is cooked at 90 – 95 °C for 15-30 minutes depending on the product.
• Cold-water soluble starches
  Pre-gelatinized starch powder is dispersed in luke warm water.

Starch preparation at laboratory scale for laboratory tests. It is important to imitate full-scale preparation as far as it is possible in order to obtain reliable results in laboratory trials. It is often hard to obtain a fully cooked solution in laboratory trials as the shear forces are significantly lower than in full-scale preparation. The usual result is a rather uneven structure with a large share of swollen granules and a lot of granule remnants.

Starch is excellent food for bacteria. Usually bacteria, fungi and yeasts enter the paper mill with the water intake. This means that the odds of bacterial problems during starch preparation are high. The largest risk is in the slurry preparation and in the final starch solution that is normally stored in a tank. In order to minimize problems, the time in slurry preparation and storage tank should be as short as possible. The temperature of the ready cooked starch solution in storage should be above 60°C. It is vital that good hygiene is maintained during starch preparation and it may be necessary to add a biocide. We recommend regular cleaning and follow-up of bacteria, yeasts and fungi occurrences.

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 enzymes in order to break down the starch 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 using 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.