View Full Version : Bourbon Production Question

10-12-2004, 13:23
Does anyone know if one or more bourbon distilleries pasteurise the mash before it is distilled?


10-12-2004, 15:11
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?

10-12-2004, 17:46
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.


10-12-2004, 18:27
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.

10-12-2004, 18:33
No, set back is used typically in Canada. Let me check further, I have some references on this.


10-12-2004, 18:48
Anyway, I know of no "pasteurization" step in USA whiskey production.

10-12-2004, 19:36
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

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

10-12-2004, 23:54
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.


10-14-2004, 00:58
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".


10-14-2004, 09:15
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

10-14-2004, 10:38
An effective sterilization can be done pretty quickly, so this might not be an issue, but consider why the grains are cooked at different temperatures: because the rye and malt would burn if subjected to the temperature at which the corn is cooked, and likewise the malt would burn if subjected to the temperature at which the rye is cooked. Maybe "burn" isn't the right word, "scald" perhaps, but this is definitely a taste issue.

The change in American whiskey after Prohibition was as much as deliberate response to changing tastes as it was a byproduct of larger scale production. Even with the size of modern plants, a product more like pre-Prohibition whiskey (lower proof of distillation, lower proof of entry) could be made, but isn't.

10-14-2004, 11:09
> ...but consider why the grains are cooked at different temperatures: because
> the rye and malt would [scald] if subjected to the temperature at which the
> corn is cooked...

I hadn't considered that possibility. I always assumed that rye just didn't
require as much cooking, so there's no reason to heat it more than you
have to (heat costs money). The malt, of course, is kept at a lower
temperature because heat destroys the enzymes that convert starches into

Tim Dellinger

10-14-2004, 12:23
All these comments (Chuck's, Tim's) are pertinent and fascinating.

Item on the issue whether different varieties of corn can "make a difference": in the current Malt Advocate is an excellent letter from a senior manager at Bruichladdich (sorry if I spelled it wrong, that name always confounds me). He said, people ask if different barleys will produce different flavors and some people say no but consider, the eaux de vie (white spirits) made from fruits such as apples, cherries, raspberries, each have strong, definable flavours deriving from that particular fruit. So, does it not stand to reason that barley produces its own flavour, and if everyone uses the same kind, that flavour will tend to be uniform, and vice versa?

This was a kind of epiphany for me: that blue corn, dent corn, etc. from some corner of the old South may well produce a quite different taste than the regular bulk grade used by most distillers. There must have been greater variety in the old days than now. This is another example of how an ultra craft taste could, as Chuck says, be created by returning to pre-1920 methods of production. I am not complaining about what is in the market but am intrigued by what whiskey might taste like using traditional methods Thomasson referred to and, say, dent corn, plus distilling out and entering in barrel at what was the norm in, say, 1900. Some of those old, beneficial bacteria may still be around - as long as the nasties can be kept out. http://www.straightbourbon.com/forums/images/graemlins/smile.gif


10-14-2004, 16:34
That's a good point! That is... the grain adding the flavor to the bourbon, just like brandies, with their various fruits. However, I wonder if the new charred barrels overpower the grains' flavors and that is why it may not make any differance what type (rather, particular brands or crops) of grains are used.

Just an idea. http://www.straightbourbon.com/forums/images/graemlins/wink.gif

10-14-2004, 18:25
Good point Hootch, which Tim Delling was driving at as well, I believe. But with whiskey aged anywhere from 4 - 20 years or so, grain differences surely would manifest themselves, at least at the younger end. In the U.K., the merits of the select Golden Promise barley variety are often compared to higher yield bulk varieties taking over the market. Scotches, even without the blitz effect of new barrels, are long aged, yet the barley type is vaunted by distillers still using old varieties such as Golden Promise. We won't know with bourbon until (likely) a micro-distiller takes the plunge and makes bourbon per the suggestions of Veach/Thomasson/Cowdery/Gillman. http://www.straightbourbon.com/forums/images/graemlins/smile.gif

Something like this will happen, but I hope I'll still be here to enjoy it. http://www.straightbourbon.com/forums/images/graemlins/smile.gif


10-14-2004, 19:11
I don't think anyone can say for sure if corn varieties would make a difference or not because no one really knows. They would have to try it. The only point I have made in the past is that, in current practice, anyone who in their ad copy talks about "the finest grains," etc., is BSing you, because in reality every distillery uses the same, commodity grade corn, rye, etc.

10-14-2004, 19:20
> yet the barley type is vaunted by distillers still using old varieties
> such as Golden Promise...

Interestingly enough, Golden Promise is a product of the Atomic Age.
In the grand old 1950s, barley was subjected to gamma radiation in order
to induce genetic mutations, and one of the results was Golden Promise,
with it's high crop yield and improved maltability. It reigned supreme
in Scottish agriculture 1970s and 1980s, and so it's what most of the
whisky was made with during The Rise of the Single Malt... and is thus
the barley of The Good Old Days.

Tim Dellinger

10-14-2004, 19:32
Speaking of grains, on the BT tour this year I asked our guide how frequently they have to turn a grain shipment away. The basic gist of his answer was that once the shippers hear about the distillery quality standards, they know to only send top quality stuff.

Anyway, the big thing they're testing for is water content, which leads to mold, right? What causes this? (ie. is it as simple as the grain gets rained on!? A leaky silo!? All of the above?) http://www.straightbourbon.com/forums/images/graemlins/confused.gif

10-14-2004, 19:55
Anyway, the big thing they're testing for is water content, which leads to mold, right? What causes this?

I don't have a source at the moment but I recollect that someone says the corn they use is about a year old by the time they get it to mash. I imagine a leaky silo or even a tear in a tarp ( particuliarly on a rainy day) could be a problem. Once on hand at a distillery, one would think that if the moisture content was near what they wanted and there was exterior moisture, they would just grind and mash it immediately and forego any further storage that might lead to molding of the grain.

10-15-2004, 01:07
The other day I was read a story in our local press about a French cider maker who came to Ontario to study local apple varieties. He was pictured munching a McIntosh apple from an orchard. He said this apple would not produce a correct cider and in turn would not produce a proper apple brandy because it was an eating apple, too sweet for this purpose. The French prefer acidic grapes from which to make brandy, and ditto evidently in apple choice for cider and calvados (apple brandy). If one did make an apple brandy from the McIntosh, no doubt it would taste different from French calvados (Normandy apple brandy where this gentleman, of the well-known Boulard distilling family, is from). I may get the chance to test this because I'll be in Quebec soon where apple brandy is made from local varieties, of which the Mac apple (from local Rougemont orchards) has always been the most prominent. I may buy some and compare the taste to the perfumed taste of a good "Calva". Note apple brandies are aged in oak which no doubt is toasted, at least, as for cognac production. One can perhaps draw inferences too from California brandy made from grapes that are different in type, and sweeter, than those used to make brandy in France. Thus, the Christian Bros. type of brandy is quite different to a standard Cognac. Now, assuming one can find a variety of corn that when cooked tastes different from the one currently used to make bourbon mashes, one would think, by parity of reasoning, that the ferment and distillate of the two would similarly taste different. Well, maybe, because apples are apples and oranges are ... cereal grains...? http://www.straightbourbon.com/forums/images/graemlins/smile.gif Cereals, or corn in particular, may act differently in this regard from fruits such as grapes and apples. I don't know for sure, but I don't think so, though. Some time ago I read about a certain kind of corn, I think a white corn, that was used to make whiskey in the early 20th century. Unfortunately I can't find the reference now. Something was said about flint corn or something like that, I can't recall the exact term used, but it seemed evident this was different from what is used today. That Golden Promise barley was developed in the 1950's (per Tim Delling) is interesting. Since growers would be looking constantly to improve yield and other characteristics (resistance to mold, for example) this is not a surprise. Certainly, it suggests barley of this type is different from barley used earlier in the 20th century and in the 1800's. In fact, Scottish distillers by and large did not use barley in the 1800's (of any type): they used bere, a hardy cereal which resembles barley but produces a thinner, lower yield. The famous whisky writer Alfred Barnard noted the pervasive use of bere in his late 1800's study of the Scottish distilleries.


10-15-2004, 03:25
Insufficient drying of the corn would also result a moisture content that is too high.

10-15-2004, 20:52
There is a huge variety of different kinds of corn. I've grown a lot of them. One of my favorites was "Bloody Butcher" - a red corn. I think it is a dent corn. The plants grew about 16 feet tall in my back yard! I dried the corn and used it for baking. It made some damned good pancakes. The depth and character of flavor is astounding compared to run of the mill commercial yellow corn. I'm sure that there would be some kind of difference in whiskey made from this.
An aside. I served some "Bloody Butcher" pancakes when one of my sons friends was here. (The red corn turns blue when you change the pH to the right pH for pancakes.) He said, "I expect my pancakes to be white", and he wouldn't eat them. He missed some great pancakes.
-Mark W

10-27-2004, 17:36
I asked Chris Morris and Dave Scheurich about this and they agreed with me that there would be no reason to pasteurize a fermented mash before it enters a still.

However, they noted that all distillers who use column stills must preheat their mash to about 140 degrees before it enters the column, not to kill bacteria but because introducing a room-temperature mash into a steam-filled, pressurized column still would cause the thing to collapse. I'm not sure what that is called, nor can I explain the physics of it, nor am I even sure it's physics that's involved, but I'm sure one of our resident scientists will explain it to those of us who became lawyers because it was the only profession that didn't require proficiency in math.

10-27-2004, 18:31
What determines the color of the bourbon? The ryes?, the charred barrel? The bottle I'm drinking now is dark reddish amber colored, similiar to say bookers....

10-27-2004, 21:41
All of the color in any aged spirit comes from the wood. The new distillate is clear.

10-28-2004, 07:59
Simply the same reason you don't pour cold water into the radiator of a hot engine I would think. When cold liquid hits hot metal the pressure of the steam is extreme and it builds up faster than it can be released. In a car, you crack the cast iron block. Just imagine what that pressure will do to a copper still.

10-28-2004, 08:15
I'll dust off my chemical engineering degree for a few moments.....as everyone knows, a distillation column is used to separate a mixture of components into two or more products. The "lighter" stuff goes overhead and the heavier "stuff" out the bottom. The column will have a temperature profile with the coldest temp at the top and hottest at the bottom. There is generally an optimum point to feed the raw mixture into the column and a corresponding temperature for that point in the column. Therefor, you heat (or cool)the feedstock to the approximate temperature of the feedpoint in the column. You don't have to get it exactly right....what is more problematic for distillations is a widely variable feedstock temperature.


10-28-2004, 08:52
Just want to add a different point to what Randy is saying. Some of the lighter congeners are not desirable if you want a very light whisky or neutral spirit. Yet, because their boiling point is under or slightly over that of ethanol, they go up with the alcohol, they don't run off at the bottom. What Canadian and GNS makers do is take the first distillate (low wines) and combine it with water, reducing the proof to about 40 (20% abv) or less. Because of the addition of water, the volatility of those lighter congeners is reversed. And steam heating of the diluted feedstock will siphon off those "bad" congeners at the top of the column, and the ethanol and water mixture comes out at the bottom for entry into the rectification column and refining to a high degree of alcohol by volume (maybe 94-96% abv). Furthermore, at different levels (trays) of the third column, at different temperature points of course as Randy says, it is possible to extract more congeners if felt necessary.

These steps are not done in bourbon production, to my knowledge.

Regarding mash/wash sterilisation, it is done in Canadian practice as far as I know (Hiram Walker says on their web site they do this). I would think it may have something to do with ensuring that the wash does not deteriorate from microbial action while being held in the beer well, but I don't know for sure.


10-28-2004, 10:18
Thanks, Dane. That's actually what I was looking for.

10-28-2004, 10:19
Regarding mash/wash sterilisation, it is done in Canadian practice as far as I know (Hiram Walker says on their web site they do this). I would think it may have something to do with ensuring that the wash does not deteriorate from microbial action while being held in the beer well, but I don't know for sure.

I ran that by Chris and Dave, and they just shook their heads.

10-28-2004, 10:28
This Friday night there is a whisky tasting event in Toronto, Forty Creek will be there although not Seagram or Hiram Walker. There will be some bourbon presence (Sazerac) and a fair amount of malt whisky. I'll ask some people about the sterilisation thing. Generally at such events one meets sales people who likely wouldn't know this stuff, but John Hall of Forty Creek may know. Anyway, I'll ask.


10-28-2004, 11:27
Hot water thrown on a hot piece of metal turns into steam FASTER than cold water does......the hot water might not crack the block though. http://www.straightbourbon.com/forums/images/graemlins/smile.gif Again, preheating the feedstock is a processing issue.....not a physics issue in this case.


10-28-2004, 11:31
That's not how Dave and Chris put it. They said introducing room temperature mash into a column still heated by live steam to 165-175 degrees would cause the column to collapse on itself, and that's the reason for pre-heating.

10-28-2004, 12:58
I think what they are saying is that if one were to put room temperature feed into an operating distillation column that had previously been operating with the feedstock at 140 deg, the still could colapse onto itsef. The introduction of colder feedstock is going to reduce the temperature of the column, rapidly condensing the rising steam and alcohol vapors, which perhaps puts too much liquid loading on the trays, causing them to collapse. Its not an explosive type of event....its the exact opposite. My comment about this being a process issue is that when designing a distilation column, there will be an optimum feedpoint location and temperature by design. Apparently 140 deg +/- is it for their column.


10-28-2004, 16:09
Yes, all of that. The feedpoint location is near but not exactly at the top of the column.

10-30-2004, 12:59
I don't think I got this quite right, and want to try again. Extractive distillation operates on the basis that the normal volatility of certain flavor compounds in spirit can be changed. One way to do this is to mix the low wines with a lot of water, to result in about 20% abv. In the (second) distillation column, the dilute distillate is introduced at the optimum point in the column. This is the tray where the temperature will volatilise compounds whose boiling point, due to miscibility with water, has now dropped below what it was before. Under the right conditions, the compounds lift off and are removed at the top of the column. Most of the ethanol and water stay (due to having a higher boiling point than what leaves); they are drawn off from the bottom of the column. Next, these high (or higher) wines are fed into the rectification column. This brings the alcohol level smartly to about 96% abv (94% abv for grain whisky production according to John Glaser last night at Spirit of Toronto - see www.compassboxwhisky.com (http://www.compassboxwhisky.com) for John Glaser's very interesting products - which answers a question a poster had on this point. Glaser said even 2 points below 96% abv can result in significant flavor improvement)). Finally, there is the potential in some plants to remove remaining congeners at different trays (temperature points) in the third column. The resultant grain neutral spirit will contain at best only trace amounts of congeners.

I believe this to be correct but if anyone with tech knowledge wishes to elaborate or correct I encourage same, in the interest of getting accurate information on the board. I hasten to add that these processes pertain to production of high proof spirits. This is alcohol intended for use in grain whisky (Scotland, Ireland), Canadian whisky or vodka and gin - not bourbon.


10-30-2004, 16:30
Your main point about there being an optimal feedpoint and temperature is
exactly right... and this is the reason to heat up the mash before putting
into the column. You could introduce room temperature mash higher up
in the column and it wouldn't collapse... but it would reduce the efficiency
of the distillation.

But I will nitpick a little bit:
> the introduction of colder feedstock is going to reduce the temperature
> of the column, rapidly condensing the rising steam and alcohol vapors,

so far so good....

> which perhaps puts too much liquid loading on the trays, causing them to
> collapse.

So you're saying that the trays can't take the weight of the liquid, and this
causes the collapse. That's probably not what's causing the collapse... there
are other, greater forces involved.

What causes the collapse is the pressure drop that happens when the gasses
condense into liquid. A partial vacuum is created... and since the external
pressure (atmospheric... about 15 pounds per square inch) is so high compared
to the internal pressure (partial vacuum), the column implodes. It's crushed
from the outside.

Google for:
atmospheric pressure demonstration
with various additions such as "video" or "55 gallon drum"
and you'll see this happen in a dramatic fashion.

Tim Dellinger

10-30-2004, 17:06
Everything you said was correct... and, as a matter of fact, there are
column still designs that use as many as five separate columns in order
effeciently extract this or that with improved efficiencies and purities
in order to make industrial alcohol.

Some of the things you mentioned about how volatility changes with water
concentration are some of the subtle and delicious little enigneering
details that make column distillation so interesting and complex. The
economic importance of petroleum distillation has funded all kinds of
research in this area... far more than the liquor industry would ever
merit... so it's a pretty advanced science by now.

> I hasten to add that these processes pertain to production of high proof
> spirits. This is alcohol intended for use in grain whisky (Scotland, Ireland),
> Canadian whisky or vodka and gin - not bourbon.

It's true that bourbon only uses one column, but like most other things, it's
all in how you use the column. With a little tweaking, I'm sure that a
bourbon distillation column could be used to make vodka. Probably not
efficiently, but I bet you could.

Tim Dellinger

10-31-2004, 17:40
Maybe I assumed too much regarding their process control systems. The distillation columns I operated in a petrochemical plant had what we called high/low pressure controls....wouldn't let the pressure exceed certain limits nor go below certain limits...ie atmospheric pressure. It never occured to me that they wouldn't install a system to prevent an implosion of the stil.