Now the first thing to start with is, all grain bourbon takes a lot of work to get to the product stage, it is not simple by any means and takes a lot of hours agitating mash, watching temperatures, waiting for conversion, and straining solids out of the wash. But for those that really want to do it, the product is definitely worth the trouble.
If you do further reading and research you will find that there are many ways to do this such as various mashing methods, and many ways to cook your corn, but you can make it work for you depending on the equipment you have available.
There are several laws relating to the production and marketing of Bourbon:
1. Distilled from a mash that at least 51% corn.
2. Distilled to no more than 80%ABV
3. Aged in brand new charred oak barrels.
4. Put into the barrel for ageing at no more than 62.5%ABV
5. Bottled at or above 40%ABV.
6. Produced in the United States.
7. Bourbon has no ageing time requirements, but there is a classification called ‘Straight Bourbon” which requires at least 2 years ageing. If straight bourbon is aged less than 4 years, it must also be clearly labelled.
8. There is also the label of ‘Kentucky Straight Bourbon’ if all of the above criteria are met, and it is produced in the state of Kentucky.
Now as far as I see it, laws 6, 7, and 8 are political factors which they would have enforced to keep their traditions safe. I think at a hobby level you can follow pretty much the rest of this. The other variation may be with the use of a single pass distillation in a bubbler. I would say the distillation values above relate to a double pot still run, whereas when using a bubbler you are not going to distill below 80%ABV, but I think we can overlook this from a hobby level as it still produces a product with the right flavours, and usually requires less ageing. I think providing we follow the 51% corn minimum, distill it with plenty of flavour carry over, and age it at the right ABV on new charred oak, then you can call it bourbon.
BACKGROUND
Starting at the basics, we know that sugars are consumed by yeast to create alcohol. When the sugars are provided from an all grain mash, there are a few steps to obtaining the sugars, as opposed to just using raw sugar in a wash.
The first step is to break down the starches from the grain, which is achieved by subjecting the grain to heat and water. The starch molecules are broken down in this process, which allows them to absorb more water and therefore swell up. This process is known as gelatinisation.
Different grains have different temperature ranges they are required to be subjected to heat and water in order for those starches to break down. Corn unfortunately, being one of the most difficult. The chart below shows the general gelatinisation temperature range for various grains.
Once the starches have been broken down, absorbed water and gelatinised, enzymes are required to convert the starches into sugars. I won’t go into details about the specifics of the enzymes, as I’d only be quoting other sources, and you can go and research yourself if you’re interested enough.
The two enzymes that we are concerned with are Alpha amylase and Beta amylase. To put simply, Beta amylase can only work on the ends of the starch chains, where Alpha amylase can break the long chains into smaller ones, providing more ends for Beta amylase to work on.
Alpha is most active in the temperature range of 68-73 deg C, and Beta most active between 54-65 deg C. These two enzymes work best in combination, which puts our area of interest as distillers somewhere between 64-70 deg C for a simple single step mash.
There are a few different methods to use when mashing. You will hear some people refer to a step mash, which is more beneficial when using malts which are under modified. This involves raising the temperature of the mash and resting at particular temperatures. These steps include a protein rest at 50 deg C, a saccharification rest at 63-65 deg C for beta amylase to work, a conversion rest at 71-72 deg C for alpha amylase to work, and a ‘mash out’ at 76 deg C. I have not used a step mash myself so cannot comment where the benefits lie for a bourbon mash, but I have not had any issues with my single step method.
Another simple method is the iso-thermal infusion, or commonly known as the single step mash. This is the method which I use, and have had no conversion or yield issues, so have not seen the need to look into further methods. This method utilises the temperature ranges of Alpha and Beta amylase, and holds the mash at a middle ground temperature to obtain the best of both enzymes at one temperature rest. The enzymes will still convert slightly outside of their optimum ranges, however they will take longer. In beer brewing, it is usually quoted for a single step infusion between 66-70 deg C, where a colder rest temperature yields more fermentable sugars, and a hotter rest temperature retains a greater mouth feel and body, with slightly less fermentable sugars. Seeing as we are distilling, I usually aim a little lower in the 63-65 deg C range to reach for those fermentable sugars to yield a higher strength wash.
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This may not seem to be a big difference, but if someone worked out incorrectly by weight for 16% barley and 14% wheat, they would have far less malt in the grain bill with more corn and a high possibility of not having enough diastatic power (enzymes) for conversion of the corn.
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). I get it from a rubber supply place, and it's a dense black foam, with the silver reflective sheet on one side (except no bubbles like I've seen on the stuff from the U.S.).