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International Starch Institute
Science Park Aarhus, Denmark
ISI 40-1e Determination of Residual Juice in Potato Starch
|1. Scope||The method is applicable to native potato starch
Rev. LT 17.12.99
|2. Principle||Peroxidase in potato juice oxidises benzidin (as a hydrogen-donor) by means of hydrogen peroxyde as a hydrogen-acceptor. H2O2 + AH2 = 2H2O2 + A.||A is colored|
|3. Apparatus||3.1 Test tube|
|4. Reagents||4.1 Diluted hydrogen peroxide, 0.3%. 1 ml 30% H2O2 is diluted to 100 ml with distilled water.|
|4.2 Benzidine solution, 0.5%. =.50 g benzidin (H2NC6H4-C6H4NH2) is dissolved in 5 ml concentrated acetic acid and diluted to 100 ml with distilled water|
|5. Procedure||2 g sample is transferred 10 a test tube (3.1) with 10 ml distilled water and 1 ml diluted hydrogen peroxide (4.1). Cork the tube and shake well. Add 1 ml benzidine solution and shake well.|
|Wait 3 min. and judge the relative amount of dark-blue stained particles.|
|6. Reporting||Report the relative amount of particles with residual juice (stained particles) as per cent.|
|7. Notes||The methods was in general use in the fifties. It lost importance with
the introduction of newer and more efficient refining techniques. The method is difficult
to carry out in an objective way.
|The original author referenced is OJB = Ole Jens Borud a great Norwegian starch chemist.|
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Keywords: laboratory method determination potato juice pulp fibre fiber starch