Bourbon Production Question

[Gillman]

Does anyone know if one or more bourbon distilleries pasteurise the mash before it is distilled?

Gary

[cowdery]

In cooking the mash, the corn is cooked at 212 degrees F for about 25 minutes, then cooled to 156 degrees F. The rye is then added and cooked at that temperature for about 10 minutes. The mixture is then cooled to 148 degrees and the malt is added. It too is cooked for about 10 minutes. The mash is then cooled to about 76 degrees F before going to the fermenters. Depending on the air temperature and the extent to which the fermenting temperature is supressed, the temperature in the fermenters can exceed 90 degrees F. After fermentation is complete the temperature again falls to about 76 degrees F before it goes into the still, where it obviously reaches alcohol's vaporization temperature. The temperature in the still column runs between 178 and 196 degrees F.

Milk is typically pasteurized by heating it to 145 degrees F for half an hour or 163 degrees F for 15 seconds.

Does that answer your question?

[Gillman]

In Canadian whisky production, or at least Hiram Walker's, the mash is sterilised after fermentation is complete. This appears to be a separate step, involving a subsequent heating, to prevent bacterial contamination and acidification. It appears this is not done per se in U.S. practice.

Gary

[cowdery]

Perhaps they hold their fermented mash for some period of time before it goes into the still. That's the only way I can imagine such as step would be necessary. Do they use a sweet mash system? That could be the answer. Part of what sour mash accomplishes is making the medium inhospitable to everything except the microorganisms you want. Still, unless they are holding the mash for some period of time in the open air, I don't see how anything would get a chance to grow.

[Gillman]

No, set back is used typically in Canada. Let me check further, I have some references on this.

Gary

[cowdery]

Anyway, I know of no "pasteurization" step in USA whiskey production.

[tdelling]

They might use this as a way to stop fermentation a touch early
by killing the yeast. I've heard that Maker's Mark likes to
stop fermentation a little early, but I think they just pump out
the mash and send it to the still... I'd imagine that even if you're
clever with energy management, it's a little costly to actually
pasteurize.

Yeast start to act differently when alcohol %s go up and available
sugar goes down... and after that, yeast undergo "autolysis", i.e.
they are digested by their own enzymes, so letting things ferment
to absolute completion is sometimes not really what you want.

If you're gonna leave a little sugar in there, it probably makes sense
to pasteurize, but it will definitely lower your yield of alcohol.

I'm a little surprised that they pasteurize.

Tim Dellinger

[Gillman]

This gets complicated, more than I thought, I think I was wrong to state sterilisation occurs after fermentation, rather, the mash is heated to around 120 degrees C before yeast and enzymes are added to cause fermentation (growth of yeast cells by acting on nutrients in the yeast mash). The fermenting vessels have to be fitted with jackets to permit such heating by steam coils. This is detail I recall reading in a manual some time ago, Canadian Club also refers to mash sterilisation on its website but no technical details are given. Anyway it involves a heating I know (in Canadian whisky production) to well over Farenheit boiling point. The sources I read said some older fermenter equipment couldn't sterilise to that degree because it was open to the air.

Gary

[Gillman]

My reason for asking the question about sterilisation of the mash was whether this practice, where done, may result in a product blander than one distilled from a mash not heated to over 120 Centigrade. It may be hard to answer this question, but I note for example that Charlie Thomason lamented in the 1960's the passing of small plant production methods in favor of large scale, modern production which in his view produced a product quite different from traditional whiskey, one that was lighter and had less body and taste. For example, he said whiskey should have "bouquet" which he described as a fruity smell akin to a very ripe apple or ripe other fruit. Very few straight whiskeys today have that bouquet: ORVW 13 year old rye does, and one or two other whiskeys. (Although I recall Elmer Lee telling me two years ago that in his opinion such a characteristic was not a necessary attribute of good whiskey, and fair enough). WR and Old Forester have a fruity element in the taste but not really in the nose. The 1970's Mellow Mash of Yellowstone Bobby brought to the last Sampler had a soft fruit character, in flavour and nose, that seemed attuned to what Thomason was saying. I am wondering if sterilisation of the mash - along with modern warehouses where used, reduction of rye and barley malt content in bourbon in favour of corn, use of chemical agents to ensure cleanliness of vessels and the other modern methods noted by Thomason - may be helping to impart a noticeably clean taste to whiskey. A clean taste is a hallmark of Canadian whiskey and a lot of that comes from the high proof base but I think there is more to it than that, and it does not surprise me to learn that CC for example sterilises its mash, and I know other Canadian producers do. I note from Chuck's comments the beer still temperatures he mentioned but that is one aspect, I am wondering if flavor can be affected by subjecting the mash to a high boil before yeast is introduced. The yeast can only make of the cereal slurry what is there, and is the mash "diminished" by such a sterilisation procedure? Those familiar with beer production know that flash or the slower tunnel pasteurisation methods (practiced on the finished beer, i.e., on what is effectively draft beer) can have a noticeable effect on taste. A cooked flavour is sometimes imparted to the beer, for example. Michael Jackson said in his classic World Guide To Beer (late 1970's): "pasteurisation kills stone dead all the life and character of the true English Bitter".

Gary

[tdelling]

A few thoughts:

> For example, he said whiskey should have "bouquet" which he described as a
> fruity smell akin to a very ripe apple or ripe other fruit. Very few straight
> whiskeys today have that bouquet

I'm a big fan of that bouquet myself... which is one of the reasons I seek out
underaged/moonshine-style whiskies. My feeling is that with a lot of bourbons,
there's plenty of big barrel flavor to hide behind, so this can cover up or
overpower any deficiencies that might be there. With the less barrel-y
styles, you rely less on the aging and more on the raw whiskey, so you
have to really get it right.

> I am wondering if flavor can be affected by subjecting the mash to a
> high boil before yeast is introduced.

Absolutely! There's a component of whiskey fermentation that gets very
little press... people just don't talk about it very much. It's the
action of bacteria. How do you think the sour mash gets sour? Bacteria!
There have been studies done in Scotland all about the different strains of
bacteria in whiksy mashes, and the various effects (some good, some potentially
bad) that these have on the fermentation and on the final flavor. I haven't
delved into the literature enough to pin the "fruity" flavors on bacteria,
but there are definintely positive benefits that the bacteria give.

A sterilization of the mash before introduction of the yeast would, of
course, kill the bacteria.

I can see why they might do it, though... if the bacteria get out of
control, they can reduce yield... or even ruin the whole batch.

Tim Dellinger