Sour Mash

One style that is sometimes used for whiskey is that of a "sour mash".

Jack explains ...
    The reason sour mashing is done is to lower the pH of the fermenting mash in order to help prevent bacterial infections. It is used in both rum and bourbon making because both grain and sugar cane/molasses have a large amount of naturally occuring yeast and bacteria growing on them because of the high sugar and starch content these products tend to have. It is much easier (on an industrial scale) to reuse the liquid left in the still after the run is finished to adjust the pH of the next batch, rather than using higher cost food grade acids. It will also help to create a more consistant product from batch to batch.
Jack on how to do a bourbon/sourmash ...
    All the grains you listed (I'd used rye flakes, corn grits & barley flakes but got into trouble) look like a de-husked, pre-processed variety (that will prevent any husk flavors - wheat is (I think) the only grain you can leave in the ferment without worrying about off (tannic) flavors developing. The husk on any other grain will make a drink that tastes like hay horse bedding). It also looks like a bourbon recipe, so, keeping with the industry standard, you ferment on the grain (only malt whiskey is sparged, anything with corn or rye in it is fermented on the grain).

    Here is how I do it.
    • Mix your grain bill together and weigh it out. For every 3 pounds of grain (1344 grams) you will need one gallon (4 liters) of water.
    • Put the grain-I use 15 pounds (6.75 Kilos) per 5 gallon (20L) batch- into your fermentor (sanitized, 20+liter buckets are best), pour in 10 liters of room temperature water, and mix it with the grain. Make sure there are no lumps or clumps, and that all the grain has been wetted down (no dry spots are allowed). The first water mixed with the grain MUST NOT BE HEATED!! If it is, the grain will clump together, leaving dry spots in the middle of the clumps, leading to an infection.
    • Take the next 10 Liters of water and bring it to a boil in a pot on the stove. Once it's boiling, pour it into the bucket with the pre-wetted grain, and stir it up to prevent any clumping. This will liquify the starch, and sanitize the batch (the precooling effects of the grain/water in the bucket will prevent the bucket from warping/melting).
    • Leave the hot water/grain filled bucket overnight. When cool, add your yeast and your enzyme, and let it ferment. Depending on the grain, when you add the yeast, the mash may be as thick as oatmeal- don't add any more water, it will thin out in a day or so, during the ferment.
    • Wait until all foaming and bubbling has stopped, and all the grain settles to the bottom (3 days to 2 weeks, depending on temperature), filter this through a layer or two of cheesecloth, and distill it.
    This is how bourbon is made commercially in the US. It's also how I've been doing it for the last year.

    If you want a true sourmash bourbon, after the distilling of this whiskey, save 4liters of slop from the still (it will be sour after it's been stripped of it's alcohol) and add it to the grain, along with 6 liters of room temp water, instead of just adding 10 liters of cool water. The idea is to get a mix of water/still slop that is 25% still slop (this is the minimum amount required by law to call the stuff sourmash bourbon in the US). The sour slop will lower the pH dramatically, helping to prevent bacteria, and helping to promote enzyme activity. There you go- no extra equipment needed, and you can fill your fermentor up to just about the top.

    Mashing (holding the temps, etc) is a waste of time for whiskey- the enzymes work in about 90 minutes at mashing temperatures- at room temp, they take about 2 or 3 days (you know, about the same amount of time for a seed to sprout- this is a natural proccess, after all). Because the yeast is in the mix all ready, no time is really lost. As soon as starch converts, it's fermented.

Ted Palmer advises
    In distilling 'sour mash' is the process of using up to 1/3 of the stillage (ie the grains left after in the wash after fermentation & distilling) in the next batch of mash. The pH is low and it helps save water in the distillery.

    (This is different from 'sour-mash' as done by beer brewers, where sour mash is made by allowing lacto baccilus bacteria to lower the pH of the mash before or during ferment. No distiller would ever add lacto or any other bacteria to his mash, for the reason that the bacteria lower the yield of ethanol. If you want to try making a lacto culture take barley malt and soak/cover it with water and let it set for a day or two. You should smell a vinegar aroma, if not, toss it out and try again. Lacto bacillus live on grain)
Brad also adds ...
    I have never done it but it is used occasionally in brewing. Some like a sour tang in stouts and Belgian wheat ales. The procedure is very simple. Bring a few handfuls of cracked pale malt in a small mini-mash up to a warm temperature, around 50 °C or so. Hold for a few hours and leave for a couple of days covered with aluminium foil. Some people put it inside a thermos flask to keep the temperature up. The naturally occurring lactobacillus on the grains will multiply and acidify (lactic acid) and sour the malt. It is then added to the main mash. I don't know the theory or practice behind sour mash whisky nor why it is done.
Jeff writes about the "backset" coming from still residue...
    The most explicit is Waymark & Harris _The Book of Classic American Whiskeys_ (although they contain some other inaccuracies) (p. 59 - 60): "Meeting the fresh mash in the fermenting tub is some of the leftover 'distiller's beer' from the lasts distillation. Called by many names - - thin slop, backset, setback, yeast back - the proportion of this 'yeast back' tends to be around 25 per cent of the total volume of the new mash. The high temperature of the distilling column has taken out the alcohol and killed the yeast, but the leftover spent beer is mildly acidic as a result of the fermentation process. Added to the new mash, the boost in acidity provided by the spent beer inhibits undesired bacteria and yeasts, making the mash - technically, but rarely by distillers, called 'wort' at this stage - safe for the desired distiller's yeast. it also provides a certain continuity in character between batches. It is from this step that we get the term, 'sour mash.' Because of the limestone character of the water, a sweet mash, that is, a mash not using any of the acidic 'yeast back,' would be pH neutral or even a bit alkaline, and hence at high risk of spoilage through undesired microbiological growth."

    BTW, backset is also added to the mash, not just the fermenter (from Murray's _Classic Bourbon, Tennessee and Rye Whiskey_): It is also at this stage [the mash] ,that the sour mash process is introduced (adding an amount of the backset, that is the spent grains from the previous distillation, the thin stillage, to the mash). This succeeds in controlling the acidity of the mash and helps prevent bacterial infection."

    Regan & Regan define backset in their _Bourbon Companion_ (p. 173): "Liquid strained from the mash after its primary distillation. Sometimes referred to as sour mash, stillage, spent beer or setback."

    So here we have it described as both spent grains and as liquid. It would appear that since the writers are neither distillers of even brewers that they are not writing from a position of first hand familiarity with the processes.

    Regan & Regan write in their _Book of Bourbon_ (p 211): All sour-mash whiskeys use a measure of backset to bring continuity of style to subsequent batches of fermentable mash. _Every_ straight bourbon, rye and Tennessee whiskey made at present is made by the sour-mash method. [I don't know if they are including Anchor's Old Potrero - JSR] Regulations used to require a minimum of 25 percent of the total mash be made of of backset in order for a whiskey to use the words "sour mash" on the label. Although that rule no longer applies, most distilleries still use upwards of 20 percent."

    Regan & Regan list the percentage of sour mash used by different distillers in their _Bourbon Companion_ (although I think this should be taken with a grain of salt - for one thing, Murray says that Beam declined to provide details of their processes and recipes but the Regans give details). They range from 20 - 25% at many distilleries to 32% at Maker's Mark to an astounding 41% reported for Jim Beam!

    As an example of how backset is used in both the mash and the fermentation, Murray reports (p. 50) that Bernheim uses 12.5% in each, for a total of 25%.

    I have seen some authors (but can't find it right now) compare sour mash to sourdough in that it provides a continuity of process, but as a baker who knows sourdough, this is not an entirely apt comparison. Sourdough, after all, contains live organisms.
Ian Smiley explains how the sour mash recipe is a variation on the "no-cook" technique :
    The reason that modern mashing methods use specifically optimized temperature, pH, water chemistry, etc is to maximize the efficiency of the operation. And, some distillers over the years have argued that such practices over-process the mash and produce a much less natural or desirable flavour.

    No-cook recipes have been around for centuries and there are people even today that swear by them. However, a no-cook recipe is very slow and extremely inefficient, and that is why the old-time sour-mash methods were developed, probably about 200 years ago.

    The sour-mash method involves the mixing of corn pone (i.e. meal), and other grains such as rye or wheat, with water, and sometimes barley malt, at ambient temperature. Almost all no-cook recipes nowadays involves the addition of sugar as well. A large charge of whiskey yeast is added and a very slow and inefficient fermentation takes place. When the fermentation is complete, the spent grains that float to the top are skimmed off and discarded. The liquid is strained from the mash and distilled into whiskey.

    A mixture of about 50% backset (i.e. the left-over liquid in the still after the distillation is finished) and 50% water is added to the remaining grain in the fermenter, and some additional grain is added to make up for what was skimmed off and discarded. There's ample yeast left in the grain sediment in the fermenter so no additional yeast is required. And, a second batch is fermented. When the fermentation is complete, the process is repeated, and so on.

    This no-cook sour-mash method is very inefficient by commercial standards, but in the end almost nothing is lost. The same grain and the same liquid (backset) is recycled again and again, with only the spent grains removed. Even the residual alcohol and non-fermentable sugars in the backset is cycled back for another enzyme exposure and fermentation.

    It was by this sour-mash method that distilleries were achieving very high grain-to-alcohol conversion efficiencies 200 hundred years ago with very little scientific understanding of the process.
Regarding Old Prorero Jack offers ...
    Rye mash is fermented on the grain- it is not sparged, or boiled.

    Old Protrero recipe:
    • Mash 100% rye malt at 110F for 30minutes, then 145 (30minutes), then 155 (30minutes) to get the best conversion, then cool with a wort chiller to 80F and add your yeast. (if you wonder about water chemistry, use the kind for "California common" styles of beer)
    • The 110F rest is called a "beta-glucan" rest- it is done to break up the gums in malted and unmalted grain, and in beer brewing can increase sugar yields by as much as 15%.
    • Double distilling in a potstill (collect the run in separate lots, say 100ml, and blend them together by taste) is what is done for Old Protrero (they use an old fashioned alembic style still- it looks like a onion-topped Cognac still).
    • It is aged for just about one year in UNCHARRED American oak barrels- he did this to allow the peppery/honey quality of the rye to come through more strongly than the vanillins from charred oak, plus, he admits to trying to replicate an early 1800's whiskey, and charred barrels were not required in America until 1933- he ("he" being Fritz Maytag- the founder of the distillery, and founder/owner of the Anchor Steam brewery) is also experimenting with some new charred oak for his later runs- but I don't think any has been released


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