High Gravity Ferments

Please note that we at homedistller.org generally frown on high gravity mashes.

1. High gravity mashes are much more prone to off-flavors, especially because they tend to ferment at higher temperatures.

2. The production of a high quality spirit is not something which can be rushed. When you get greedy for a few more percentage points of alcohol, you run a greatly increased risk of creating an inferior product. The point of home distillation isn't to create a lot of alcohol, but rather to refine the art of creating particularly high quality spirits. Relax, take your time, do it right.

3. If you insist on high gravity washes, here are some older tips. Of course, the best place to ask for help or ideas is on the Homedistiller Forums.

If you want to use high concentrations of sugar, in order to realise final high alcohol, you need to take special steps.
From the Whitelabs site, the instructions for using their WLP099 Super High Gravity Yeast are as follows ....

  • Aerate very heavily, 4 times as much as with a normal gravity beer. Less oxygen dissolves into solution at high gravity.
  • Pitch 3-4 times as much yeast as normal.
  • Consider aerating intermittently during the first 5 days of fermentation. This will help yeast cells during a very difficult fermentation. Aerate with oxygen for 30 seconds or air for 5-10 minutes.
  • Higher nutrient levels can allow yeast to tolerate higher alcohol levels. Use 2 times the normal nutrient level. This is especially important when using WLP099 to make wine and mead, which have almost no nutrient level to begin with.
  • Do not start with the entire wort sugar at once. Begin fermentation with a wort that would produce a 6-8% beer, and add wort (it can be concentrated) each day during the first 5 days. This can be done together with aeration. This is mandatory if the reported 25% ABV is to be achieved.
Dr Clayton Cone writes..
    Here is a brief protocol for the production of high alcohol fermentations. You can down size to your needs. EC 1118 is a good choice up to 16 - 18 % alcohol. K1 and L2226 seem to work better at 18 - 20+% alcohol. The key to the success of fermenting to these high levels of alcohol is management of the yeast: lots of nutrients, pH control, small amount of aeration and occasional stirring to keep the yeast in suspension.

    High Alcohol Fermentation 15-20 +% v/w
    K-1or L 2226 Yeast Strain 6# / 1000 gallons
    Vi-A-Dry Inactive Yeast 2133 2# / 1000 gallons
    Fermaid K 2# / 1000 gallons
    Di Ammonium Phosphate (DAP) 4# / 1000 gallons

    Sprinkle the 6# K1 or L2226 yeast into 6 gallons of 105 F. water. While gently stirring ,to prevent lumping. Allow to set for a maximum of 30 minutes. Stir to disperse.

    To minimize cold temperature shock, cool the warm rehydrated yeast slowly , in stages, by adding equal volumes of juice to the slurry. The attemperating stage is important to prevent the formation of unhealthy yeast cells (petite mutants) which form when the yeast is suddenly exposed to greater than 20 F drop.

    Add the yeast inoculum to the bottom of the fermenter after a few gallons of the juice has been pumped in. This allows the yeast added time to get through its lag phase and exposes it to the necessary oxygen that it requires for healthy , alcohol resistant cells after the growth phase.

    Divide the nutrients into several portions and add in increments throughout the first 72 - 96 hours.

    Start the fermentation in juice that is below 24 brix, preferably 16-20 brix. The lower the initial brix the better the yeast will grow to achieve the necessary population required to complete the last stage of the high alcohol production.

  • Aerate or circulate gently for the first 24-48 hours. Do not put air cap on for first 48 hours. Oxygen during the yeast growth phase is necessary to produce the cell wall protection that is required towards the end of the fermentation.

    Monitor the pH carefully during the first 24 hours. Do not let it drop below 3.4. Adjust with potassium carbonate or other suitable alkaline material.

    Monitor the fermentation closely. When the sugar drops to 4 brix, add fermentable sugars to bring it back to 6 brix. Repeat this 4-6 brix. cycle until you reach the desired alcohol level, allowing the last cycle to go to completion (dry).

    The temperature should be 80 - 85F. for the first 48 hours and 70 - 80F. for the remainder of the fermentation.

    pH below 3.1 places an added stress on the yeast cell as the % alcohol increases. It is best to maintain a 3.4+ pH. Use carbonates such as potassium carbonate to keep the pH above 3.4. It is especially important to monitor the pH during the early hours of fermentation when you are using sugar, honey and some concentrates to increase the alcohol level. There is little or no buffering capacity in these sources of sugar.

    High levels of nutrients are absolutely essential for the yeast to produce high levels alcohol.

    100% fructose sugar is not recommended as a source of added fermentable sugars. Most wine yeast ferment fructose at a slower rate and often times have trouble fermenting to dryness.

    You can expect 0.58 - 0.60 % alcohol by volume for each 1% sugar. Thus the total brix or % sugar should be 33 -35.

    With experience you may be able to adjust the brix between 4 and 10 rather than 4 and 6 to minimize the number of sugar additions.

    Every juice ferments differently You may have to increase the yeast and nutrient levels or you may even be able to decrease one or more of them. If you are using sugar, honey or concentrate to increase the alcohol level, there are little to no nutrients present in these so you will have to add all that the yeast need for a healthy fermentation. .

    You should obtain a Clinitest Kit from your local drug store and use it to monitor the sugar level near the end of the fermentation. It cost about $0.10 per test. It is an ultra simple test normally used to test your urine for sugar. 3 drops fermenting wine + 10 drops water in a test tube + 1 tablet, wait about thirty seconds. Read color compared to a chart.

    One step, high gravity , 25-40 brix, fermentation:
    High nutrient and yeast inoculum levels are necessary..
    3-5X the above recommended yeast and nutrients are required.

  • Sugar is just as toxic to yeast as alcohol. Yeast growth decreases as the brix increases. Above 25 brix the growth drops dramatically and has to be compensated by increasing the inoculum. A general rule of thumb-1x10 6th yeast cells / ml./degree brix; 1/2 # K-1 / degree brix/1000 gallons juice; i.e., 1000 gallons of 30 brix juice would require 15# K-1 yeast.

    There is usually very little suspended matter in the high gravity juice and as a result the yeast tends to settle rapidly. The yeast on the bottom of the fermenter participate very little in the sugar to alcohol process. Therefore, stirring and or circulating constantly or frequently throughout the fermentation is recommended.

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