Turbid Mashing

Since the next brew is going to be a Lambic, I thought it would be wise to review the traditional mashing technique used in making them, a Turbid Mash.

The turbid mash is a peculiar technique in that it pretty much goes against the main thing you learn to do as an all grain brewer, which is efficiently produce wort with high concentrations of fermentable sugar (Maltose, Sucrose). This mash is designed to just about the opposite, produce highly dextrinous wort or in other words, wort with lots of complex unfermentable sugars. The use of the word turbid show clue you in that mash is far from a typical mash. As it turns out, the bacteria that is used in Lambics really enjoys these dextrins. Brettanomyces for example is supper-attenuating and will eat complex sugars until it is 99.9% gone. This is important because it play a major role in how a lambic gets its flavor.

The history of the turbid mash actually explains a lot about how and why it came about. In the early 19th century, Belgium created a tax that was based on the size of your mash tun. This resulted in breweries trying to get away with the smallest mash tun possible and still make the same amount of beer. To do this the brewers would use a very thick mash with many steps, gradually added more water, stirring, and pulling wort off directly from the top of the mash. The wort pulled from the top of the mash was heated and later re-added to the mash prior to sparging. The wort was removed in this way in order not to disturb the grain bed too much. If pulled from the bottom is would certainly compact the grain bed and make sparging impossible. Additionally, pulling the wort off in the manner helped to create highly dextrinous wort. One additional explanation for the number of steps and strange procedure of pulling wort off the mash had to do with the fast that un-malted wheat was often used up to 30-40% of the grist. The early rests in addition to infusions of boil water helped at breaking down the glucans in the wheat to ensure that the lautering process went smoothly.

I found two references examples of how to do my own turbid mash at home. Both are very similar but have some differences that I want to present. Details are below: 

Homebrew Turbid Mash Schedules 

For comparison sake, going to assume the below is for a 10 gallon batch with 20 lbs of grains. I have highlighted the differences in red.

	From book "Wild Brews" by Jeff Sparow. Page 141	From BYO issue Jul-Aug '08, vol 14, No.4. Pages 48-54
	Assumes total water @ 2 qt/lb (40 qts or 10 gals)
1.	Dough-in with 20% of H20 (2 gals or 0.4 qts/lb) to raise mash to 113 degs F. Rest for 15 mins.	Dough-in with 0.3 qt/lb of H20 (1.5 gals) to raise mash to 113 degs f. Rest for 10 mins.
2.	Bring water in HLT to boil and maintain heat	Bring water in HLT to boil and maintain heat
3.	Add 20% of H20 (2 gals) at 212 degs F to raise mash to 126 degs F. Rest for 15 mins.	Add H20 to raise mash to 138 degs F. Should be a overall total of 0.45 qts/lb in mash. Hold 5 mins.
4.	Remove 33% of liquid from mash (1.32 gals), heat in secondary kettle to 190 degs F and hold	Remove 2 quarts of liquid from mash (0.5 gals), add to secondary kettle and heat to 180 degs F and hold.
5.	Add 30% of H20 (3 gals) at 212 degs F to raise mash to 149. Rest for 45 mins.	Add H20 to raise mash to 158 degs F. Should be a overall total of 0.625 qts/lb in mash. Hold 30 mins.
6.	Remove 50% of liquid from mash (2.84 gals), add to secondary kettle, reheat to 190 degs F and hold.	Remove 2 gallons of liquid from mash , add to secondary kettle, reheat to 180 degs F and hold.
7.	Add 30% of H20 (3 gals) at 212 degs F to raise mash to 162. Rest for 30 mins.	Add H20 to raise mash to 162 degs F. Should be a overall total of 0.625 qts/lb in mash. Hold 20 mins.
8.	Add 38% of total mash liquor volume (3.8 gals) into boil kettle and begin heating.	Drain of the same amount of liquid in the secondary kettle from the mash into the boil kettle.
9.	Add contents of secondary kettle to mash to raise to 172 degs F. Rest for 20 mins.	Add contents of secondary kettle to mash to raise to 167 degs F. Rest for 20 mins.
10.	Recirculate wort to remove husks and chunks.	Recirculate wort to remove husks and chunks.
11.	Sparge with 190 deg F H20 until gravity of runnings is less than 1.08 sg	Sparge with 190 deg F H20.

So you can see that they are very similar but, also have some differences. Main differences seem to be around the amount of water, number of steps, and the temperature of each step.

Question now is whether or not we should try and reproduce these steps or come up with some other method to get highly dextrinous wort. Options I can think of are to: use lots of dextrin malt, mash high, boil some wort prior to full conversion, add malto-dextrin to boil. I'm interested in hearing suggestions or thoughts on this.