a2 chem special study module - food science

Chapter 6, investigating flour:

expt 6.7c - qualitative test for ascorbic acid.

method: pour a little 2% iodine solution (aq) over wet flour in a petri dish.

what are the positive and negative results of this test?

thanks

Reply 1

ShOcKzZ

7

rae

Chapter 6, investigating flour:

expt 6.7c - qualitative test for ascorbic acid.

method: pour a little 2% iodine solution (aq) over wet flour in a petri dish.

what are the positive and negative results of this test?

thanks

food science? ...what the???

Reply 2

rae

OP

for the nuffield chemistry course at A2 we have to do a special study module - ours is food science. its basically learning the contents of a book. thing is, ive parted company with some of my experiment notes and im doing the past papers where they ask for the procedure and results...

Reply 3

halc

Firstly I can't help so I shouldn't really post, sorry...

But which wackjob college has decided to do a course module that splices an empirical science with cookery!?

And actually, thinking about it, wouldn't the ascorbic acid reduce the iodine in solution to iodide? - therefore the qualititive positive test would be decolourisation of the dark violet solution.
When titrating with iodine it's customary to use starch indicators because of the complexes iodine forms with starch, I don't know if that could be a further facet to a test for it or not...

I'm just a simple AQA Chem student, what would I know about cake baking!

Reply 4

Unregistered

rae

Chapter 6, investigating flour:

expt 6.7c - qualitative test for ascorbic acid.

method: pour a little 2% iodine solution (aq) over wet flour in a petri dish.

what are the positive and negative results of this test?

thanks

hiya
If i remember rightly (and i pity you doing the dreaded food science, we are too) first it goes blue/black as it reacts with the starch, but then if abscorbic acid is present you get little "islands" of white reappearing as the iodine is reduced to I-, as someone else said :smile:

Rosie

a2 chem special study module - food science

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