It is best to run a starch test on every batch of maltose that is made - if the starch has not been properly converted, difficulty will be encountered in filtering the juice.
One drop of medicinal iodine is diluted with 10 ml of water (this makes a solution about the colour of tea). One drop of the juice is added to this solution. If the solution turns brick red, there is no starch present, but if there is any blueness, it means there is still some starch left.
If the mixture turns blue, or the juice will not filter properly, another batch of crushed seedlings should be added and the mixture should be left for another 2 – 3 hours.
First, a decision (mainly depending on availability and cost) should be made whether to use rice or maize, or perhaps to use another cereal grain. To select a small number of varieties to test, it is best to tap existing sources of information, such as seed manufacturers, local brewers or maltsters and the Department of Agriculture. A good malting variety is best. It is likely to be a fast growing variety with a large germ. Tests should then be run to find out whether any of the screened varieties is satisfactory, and which is best. Lots with good viability (at least 90% germination and preferably with over 95% germination) should be obtained.
In the event that no suitable variety can be found, suitable seed for multiplication can be obtained from the Director, National Institute of Agricultural Science (INSA), Vandien, Thomh-tri, Hanoi, Viet Nam.
Equipment and materials needed for the test
Scale This scale should be capable of weighing 20 grams of seedlings to within 1 g and 130 or 200 grams of starch to within 5 grams. It is far better to measure the seedlings and the starch by weight, but if no suitable scale is available, a fair indication can be gained by measuring quantities by volume, according to the following table.
|Sedimented (wet) starch
|Dry starch, lightly tamped
Measuring cylinder. 100 ml or 250 ml capacity.
Pestle and mortar, or any other means of crushing 20 grams of seedlings.
Saucepan, 1 litre capacity.
Implement for stirring (spoon or piece of wood).
Starch test materials (see above)
Clear plastic or glass container, capable of withstanding boiling water, between 1 and 2 litres capacity.
The way to run the test
Measure out 800 ml of water and bring it to the boil. Meanwhile, crush the seedlings, slurry the starch in the clear container (if the starch is wet, use 50 ml of water and if it is dry, use 120 ml of water) and mix in the crushed seedlings. Finally, when the water is boiling pour it into the slurry, mixing constantly and stirring in any ungelatinized starch (which still looks white). Within a minute, the slurry should be grey and free running: it should be only a little thicker than water.
If the liquid remains thick, the variety is unsuitable and the test can be abandoned, but if it becomes thin, the second part of the test can be applied, as follows:
Immediately cover the container and wrap a cloth around it. 60 minutes after adding the boiling water, the solution should be tested for starch (see above). If there is blueness it means that there is still some starch present and the variety may be unsuitable. The mixture should be kept hot for 3 hours and the test run again.
If there is no blueness, the variety will be satisfactory.