15 replies to this topic

[wjames]

Ive just stuck a batch of cornflour in the oven........to cook for a few hours at 160 degrees.


My question is.....

What ACTAULLY happens to cornflour to turn it into dextrin ?......ive had a quick look about, most people just give info on how to make it.....


anyone

[Mortartube]

I am probably wrong here but I seem to recall that it leaches out the natural starches which then make it more sticky when it it wetted. When it is cooked and cool. Wet your thumb and forefinger and put a little dtxtrin between them. You will find out it is quite sticky.

Pretty much all you ever wanted to know about dextrin is here.

http://www.answers.com/topic/dextrin

Edited by Mortartube, 09 November 2008 - 03:38 PM.

[wjames]

nice one mate.


great info there.


other than making it myself, im tempted just to buy a kilo of it......

[portfire]

Wet your thumb and forefinger and put a little dtxtrin between them. You will find out it is quite sticky.

Haha, thats my test I have tried the Iodine test but solution always turned brown (indicating starch) and now I always use the "finger test" after about 3-4Hr at 200C. Never had a problem with binding

[Mortartube]

I also tried the Iodine test once and it was pants. I threw a batch of dextrin away based on the Iodine test, so I use the sticky fingers test (ooohhh, sounds a bit rude). Lol.

[portfire]

LOL...works though

[bwdoz]

Haha, thats my test I have tried the Iodine test but solution always turned brown (indicating starch) and now I always use the "finger test" after about 3-4Hr at 200C. Never had a problem with binding

I'm not going to stake my life on it but I'm almost certain it should turn blue black if starch is present, not brown. Yellowy-brown is pretty much the colour that Iodine will stain anything. Might be worth checking!

[spanner]

If in doubt about the color, put the iodine on a freshly cut potato. THAT'S the color indicating starch. Kinda purplish blue, IMO. A brown color indicates, well, not starch!

[wjames]

well.....The batch i did tonight went wrong.....i think i might bin it......

It spent nearly 5 hours in the oven.....at 200 degrees c....elec fan assisted.... ( i test my oven !!!!!)

It came out WHITE......i checked it after 2 hours, then every half hour after that.....after 5 hours i got fed up, and took it out....

I tried a little bit with water....forms a paste, not unlike wallpaper paste......but not like i'd expect.

Perhaps this cornflour isnt what it should be !

[Mortartube]

I should be a nice golden brown, Stir it occasionally. After 5 hours I am surprised it hasn't burnt.

I use Sainsburys cornflour with no problems. How much did you put in? I cook up to 500 grams at a time.

This won't be the most interesting video you'll ever see but it shows you what to do. Corn starch is cornflour BTW to out transatlantic cousins.

http://uk.youtube.co...h?v=Xdua2zOmQcg

Did you cook it in the top, middle or bottom of the oven?

Edited by Mortartube, 10 November 2008 - 02:55 AM.

[spanner]

Removed due to redundancy, sorry.

Edited by spanner, 10 November 2008 - 05:32 AM.

[portfire]

I'm not going to stake my life on it but I'm almost certain it should turn blue black if starch is present, not brown. Yellowy-brown is pretty much the colour that Iodine will stain anything. Might be worth checking!

Sorry my bad your right. I remember now, (getting old) brown is the colour it stained the worktop

[Bonny]

I cook mine for about 2 hours @ 400F stirring every 15 minutes. When it reaches a nice golden brown, I consider it done. It seems to work fine for me.
See here:
http://www.wichitabu...ks/dextrin.html

[Mumbles]

It's probably worth noting that dextrins react with iodine too, just giving a different color. I found it useful to make a positive control buy making a suspension of starch and iodine to compare against my dextrin and iodine test. Mine usually has a little bit of starch left, but it works just fine. I cook it at 350F for about 2-3 hours, and pump it up to around 400-450 for last half hour to get that nice tan color.

I can tell by taste when it's done. It starts tasting sweet, and it just has a different texture, kinda slippery. When you have some really good dextrin, if you make a slurry of it, rub it between your fingers and pull it apart it starts making strings. I have a little bit of commercial stuff that does that. That dextrin makes stars as hard as cement. I don't really use dextrin anymore, I've moved to SGRS. I do, or at least should, still use it for making burst though. SGRS takes a while to activate, and rolling onto the burst carrier just doesn't work as well.

[bill]

Just as a matter of curiosity does anybody know the chemical make up of dextrin? I know its a glucose polymer but more than that I can't seem to find.