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RobertFromOz
04-25-2004, 06:34 PM
Could someone please tell me the way of estimating the colour of colour or roasted malts?

The malts I am working with are very pale malts produced from gluten free grains such as sorghum, and buckwheat (kilned to 40C). They are then roasted in an oven at temps ranging from 100C to 250C. The roasting destroys all the enzmes as they are very heat sensitive.

Some quite nice roasted malts have been produced, which add colour and flavour to otherwise very pale beers. I would lke to know how to estimate the colour contribution of the malts for recipe calculations.

Alex T
04-25-2004, 07:24 PM
You are most likely going to have to conduct a standard mash (50g in 500mL I think?) - and then measure the colour of the wort. There should be several methods available. Being in Australia, you will want the end result in degrees EBC. I believe this is done with a spectrophotometer at a certain wavelength. Someone else may know the procedure off the top of their head.

Maybe post this in the Malt Q&A section - the Cargill person should know.

Cheers,

Alex

gitchegumee
04-25-2004, 09:35 PM
I agree a standard infusion will likely be necessary to extract the colors to approximate a production mash. I have heard that one cheap way to estimate is to use a known beer's color and dilute either that beer or your beer (which is darker?) to obtain a close match. The dilution ratio and the beer's original color can be used to estimate. Another way is to buy color slides for a colorimeter. They are not expensive. The same techniques are used to estimate honey and maple syrup colors. Good question. Good luck.

RobertFromOz
04-26-2004, 03:54 AM
I know about the technique for diluting a beer of a known colour to estimate the colour of your beer. That's fine.

The problem is: how to extract the colour of a roasted malt which will have no enzymes, so that the colour can be measured.

A similar question would be how to measure the colour of a roasted barley (again no enzymes), so a standard mash can't be used.

Also, when a beer is fermented, the colour lightens as the yeast drops out. How is this compensated for.

Thanks for your thoughts

tarmadilo
04-26-2004, 05:38 AM
I believe they're suggesting you prepare mashes (in small amounts) of just the roasted grains, so you can get an accurate idea of how much color you'll get from each one.

Or maybe prepare a mash without the roasted grains, and one with 10% roasted grains, and compare the color difference.

I wouldn't worry about yeast, as your wort should be pretty much the same color after it drops out as it was before the yeast was pitched!

Cheers, Tim

Alex T
04-26-2004, 08:55 PM
Hi,

Just to elaborate a bit. (Note: This is not a published method!!! - I was looking in my brewing texts and couldn't find what I was looking for!)

- grind 50g of malt very fine (90% flour) with a laboratory disc mill
- mix with 500mL water.
- mash initially at 45degC for 30min, and then while constantly stirring, raise temp to 70degC.
- mash for 2hrs.
- cool to 20degC.
- filter the mash through filter paper.
- analyse the colour of the wort with a colorimeter or a spectrophotometer (not sure of the wavelength or calcuation!)

while you are at it, measure the extract. the cargill person should be able to get a more exact method for you.

cheers,

alex

Cargill Malt
04-26-2004, 10:46 PM
I'm guessing you're looking for the "Congress Mashing" procedure. This is the process used for the determination of malt color. I'll forward the wavelength details tomorrow. If memory serves you check the sample in a 1 cm cell at around 470 for color (absorption) and at 700 for turbidity. The check at 700 is to ensure that particles are not scattering too much light and giving you a false high color reading. If the result at 700 is too high you have to filter your sample again to get a true reading. The absorption result is multiplied by 12.7 for ASBC. I'll double check those wavelengths and get back to you.

As far as how you determine the color of very highly colored malts, you dilute them with pale malt. If you are checking an 80 color caramel malt for example, you might mix it 50/50 with pale malt. If you are checking roasted barley you would use more like 10% or less of the RB. If you don't dilute sufficiently with pale malt you will likely be measuring outside the sweet spot of your spectrophotometer. Lab instruments lose accuracy at the limits of their measuring capability. Simple math is used to adjust for the ratio of pale malt to the malt you are testing to get the undiluted color.

More details on process later.

Do you have a spectrophotometer that you have access to? This detail won't be too helpful if you don't.

Cargill Malt