Proper dosing of evaporators with amylase dramatically reduces the amount of starch in syrup. When amylase concentrations are correct, there is a difference in the amount of starch between clarified juice and syrup at the same Brix detected by an iodine test. The following procedure can be used to determine whether sufficient amylase is being added to reduce starch concentrations.
Procedure:
- Samples – clarified juice and syrup.Determine Brix of clarified juice. If the clarified juice is turbid, filter or centrifuge to clarify.
- Determine Brix of syrup, and then dilute with water to the same brix as the clarified juice.
- Prepare three test tubes, one is a control, one clarified juice and one dilute syrup. To each tube add 0.5 ml of the appropriate sample (water, clarified juice, diluted syrup).
- Add 0.2ml of 2N Sulfuric acid to each tube..
- Add 5.0ml of starch-iodine reagent to each tube and mix.
- Add 10 ml of water to each tube and mix.
- Determine the absorbance at 660 nm of the solutions in the clarified and diluted juice tubes, using the control solution to zero the instrument.
If the amylase dose is correct, there will be a significant difference in absorbance between the clarified and diluted syrup samples. The diluted syrup should be close to zero. It is possible to use this test to determine starch concentrations in samples simply by calibrating the absorbance produced, using a known concentration of starch. The response is linear with concentration.
Reagents: (concentrations required to make 1000 ml of solution)
Starch- Iodine, dissolve 0.88 gm of Iodine (99.8%) and 41.5 gm of Potassium Iodide in one liter of water. This solution should be stored in a dark bottle to protect it from light.
Sulfuric Acid (2N), add 55.5 ml of concentrated sulfuric acid to water and make up to one liter.