Chapter 6 Cereal science
Read our general notes on Risk Assessment
When I carried out the qualitative test for ascorbic acid in flour (Experiment 6.7c), adding iodine caused the flour to turn black, but then the black parts started to disappear. I’m stuck, what is the explanation for this?
Igloo replies
This test normally works very well indeed. I’m not sure what you mean by “the black parts started to disappear”. Usually, after a minute or so, white spots develop on a blue-black background. The white spots represent places where reduction has taken place, i.e. where there are tiny crystals of ascorbic acid. If the entire surface has turned white I suspect that the flour has been “doctored” with large quantities of finely powdered ascorbic acid, or at any rate some other reducing agent.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
back to Chapter 6 Cereal science
Rate this page or react
Share your views on this page, 0 ratings so far
updated: 25 January 2006
