Aim:
            To prepare colloidal solution (sol) of starch.
Principle:
           Starch forms a lyophilic sol when water is used as the
dispersion medium. The formation of sol is accelerated by
heating. The starch sol can be prepared by heating starch
and water at about 1000C. It is quite stable and is not
affected by the presence of any electrolytic impurity.

Apparatus required:
         

    ? Beaker (250 ml and 50 ml)          

Glass rod
? Funnel
? Filter paper
? Mortar and Pestle
? Tripod stand
? Wire – gauze and burner

Materials required:
? Soluble starch (1g) and distilled water. (250 ml)
Procedure:
h. Take 1 g of starch in mortar and add few ml of distilled
water.
i. Grind the starch to make a thin paste and transfer this
paste to a 50 ml beaker. Take about 125 ml of distilled water
in a 250 ml beaker and heat the beaker so that water starts
boiling.
j. Pour the paste slowly with stirring into boiling water in
the beaker
k. Continue boiling for about 2 – 3 minutes and then allow
the beaker to cool
l. Filter the contents of the beaker through a filter – paper,
fixed in a funnel. Label the filtrate ‘Starch Sol’.
Precautions:
c. The apparatus used for preparing sol should be properly
cleaned.
d. Distilled water should be used for preparing sols in
water
e. Starch should be converted into a fine paste before
adding to boiling water.
f. Starch paste should be added in a thin stream to boiling
water.
g. Constant stirring of the contents is necessary during the
preparation of the sol.
7.2 Preparation of colloidal solution (or
sol) of egg albumin

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
The 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 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 a bacterial attack during starch preparation are high. The largest risk is in the slurry preparation and in the final starch solution that normally is stored in a tank. In order to minimise attacks 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.