AH Bio: Caculate Sugar Concentration

I'm currently doing my AH Biology investigation and am have trouble in finding a method to calculate the sugar concentraion in fruit juices (this is only a small part of the investigation and I have the rest of it worked out).

My initial theory was to use an indicator, set up a calibration graph for percentage transmission (colormetry) and then see the results with the fruit juices, but the fruit juice is clouded and the calibration graph wouldn't work.

I have spent 3 hours searching on the internet today and I can't find anything! The texts books I have available at school, in both the biology and chemistry department, don't help at all!!!

Any little hints or tips you might have will be helpful!!!!!!!!!!!!!

Reply 1

latentcorpse

sounds to me like u need to set up a very enjoyable experiment.........

............ keep going..................

get abunch of friends and do some tasting and see what they reckon!
P.S. probably help if u get pissed first
u can see why they don't like me (check the rep!)

Reply 2

latentcorpse

why don't u try something like centrifuging to throw heavier things like sugars to bottom - although that may also send other crap down as well

solvent extraction???

u could try and complex it with a transition metal and then do colorimetry although i dont think that'll work

errm... seperating funnel??

distillation??

i dont know if any of these will work i am just listing some extraction methods that spring to mind - talk to your teacher and so long as you have a few suggestions so as you don't look too desperate then they should be able to hint u in the right direction unless of course u r the first person in your school to do that project! (foolish move on my part in lets see now... ahh yes 3 of my 4 ah's) hope this helps a bit!

Reply 3

Hybrid

Unfortunately, I am the first to do that experiment. Bah. Chemistry was so much easier!!!!!!!!!!!!

Separating funnel won't work...it's not bits of juice that make it cloudy, it's the juice juice.

I've already asked about distillation methods, and thought i'd try it out (pre-investigation work to make sure my methods would work), and it didn't. There was still a brown hint to it (think concentrated apple juice, only a little cloudier) and it is still enough to affect the reading.

Centrifuge won't work either...

If I could get hold of a refractometer things would be so simple!!!

Reply 4

Acaila

How about I stick this in the Academic biology forum?
You may get some more advice there as this isn't really a subject specific place.

Reply 5

friendlyneutron

Someone I know did something similar with a quantitative reaction with benedict's solution? you could look into that and use colorimetry/spectrophotometry or summat. Best of luck! x

Reply 6

tiggerish

I've got this problem too. In the end I used diastix but they are crap.

You can try:
Quantitative Benedict's (its a special version)
Diastix
Rochelle Diabur 5000 sticks
Glucose oxidase to change the glucose into gluconic acid, then perform a weak acid-strong alkali titration (use phenolpthalein as your indicator)
and there's another method which requires you to make a calibration curve but I can't remember how that works

Reply 7

Hybrid

Glucose oxidase? Hrmmm....

I've finished most of the practical now (thanks for your posts everyone!), and used the clinistix too, but I might do a follow up with that idea if I have time.

Hrmmm....now the write up *groans*

AH Bio: Caculate Sugar Concentration

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