ISI 40-1e Determination of Residual Juice in Potato Starch


1. Scope The method is applicable to native potato starch

 

 OJB 1960
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.

Judgement

 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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