International Starch: ISI 40 Determination of Residual Juice in Potato Starch.

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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	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.

Keywords: laboratory method determination potato juice pulp fibre fiber starch