Preparing grain wash

Preparing grain wash

Grain does not contain ready-made sugar in the amount yeast needs. Most of the raw material is starch. That is why grain wash cannot be set up on the “water, grain and yeast” scheme: first the starch has to be converted into soluble sugars, then the wort cooled and fermented.[2][5]

Two working schemes are described below: saccharification with malt and saccharification with industrial enzymes. Both begin the same way, with preparing the raw material and the water. Temperatures and times are given as working guidelines: the exact regime depends on the grain, the degree of milling, the share of malt, the water composition and the instructions for the enzyme product.

What you will need

• food-grade grain with no musty smell, insects or traces of mould;
• clean drinking water;
• a grinder or mill;
• a mashing vessel with spare volume;
• an accurate thermometer and, preferably, a pH meter or suitable narrow-range indicator strips;
• an iodine solution for testing starch;
• a fermentation vessel with an airlock;
• a saccharometer or hydrometer and a measuring cylinder;
• yeast intended for grain wort.

For contact with the wort use food-grade materials: stainless steel, food-grade plastic, glass or suitable copper. Vessels and tools are washed, rinsed and sanitised in advance. Traces of detergents, rust, unknown seals and containers that once held chemicals are not suitable for wash.

Grain and milling

Wheat gives a soft grain profile, rye usually makes the mash more viscous, corn requires more intensive cooking, and barley gives a pronounced malty aroma. The choice of grain is not only a question of yield but also of the flavour of the future distillate.

The milling must open up access for water and enzymes to the starch. Grain that is too coarse saccharifies worse, and flour forms a dense mass that is hard to stir and filter. For a thick mash it is more practical to start with fine grits and adjust the milling based on the result. Flakes pre-processed by the manufacturer can be used without full cooking if their labelling allows it.

Grain with mould, or with a rancid or chemical smell, is not used. Mould can penetrate inside the kernel, and some mycotoxins survive subsequent processing. Scraping off the visible bloom and putting the rest into the wash is an unsafe way to “rescue” the raw material.[9]

How much water to take

For a first attempt it is convenient to take about 3 l of water per 1 kg of grain. A thicker mash needs good stirring and tolerates overheating less well, while a thinner one is easier to handle but loses heat faster. The actual water volume is adjusted to the size of the vessel and the method of separating the spent grain.

Do not try to bring any water to a single “correct” pH in advance by adding acid, gypsum or a buffer at somebody else’s dosage. The pH of the finished mash is affected by the water’s alkalinity, mineral content, malt, grain and the water-to-grain ratio. If pH is controlled, measure the mash itself after mixing the water and grain, not just the source water. For enzymatic saccharification the working guideline is a slightly acidic environment of about pH 5.2–5.8.[2][3] The target value is checked against the enzyme’s instructions.

Option 1. Saccharification with malt

Malt is sprouted and dried grain in which enzymes have already formed. Alpha-amylase thins the long chains of starch, and beta-amylase produces a significant part of the fermentable sugars.[2][3] If all the grain is unmalted, it is usually not enough on its own: malt or added enzymes are needed.

Mashing

This sequence suits base malt and pre-gelatinised flakes. Unmalted grits are first prepared according to the regime for the chosen grain. If cooking is required, the main portion of malt is added only after cooling: boiling destroys its enzymes. The share of malt depends on its diastatic power, the ability to saccharify starch. Roasted or caramel malt does not replace enzymatically active base malt.[2]

1. Heat the water to a temperature at which, after the grain is added, the mash will land roughly in the 60–65 °C range.
2. Add the milled grain and malt, and thoroughly break up the lumps.
3. Hold the mash for about 60 minutes at around 62–65 °C. At a lower temperature you usually get a more fermentable wort; at a higher one the share of dextrins and the body of the drink increase.
4. If a lot of wheat, rye or oats is used and the mash turns out viscous, an additional rest may be needed according to the instructions of the chosen process. Do not raise the temperature blindly: enzymes quickly lose activity when overheated.
5. Do an iodine test. On a clean white surface mix a drop of liquid wort with a drop of iodine. A blue or blue-black colour means starch is still present; repeat the reaction after an additional hold. Do not return the iodine to the food vessel.

The ranges of enzyme activity overlap: roughly, beta-amylase works at about 54–66 °C, and alpha-amylase at about 66–71 °C.[2][3] So a single rest at about 63–65 °C is a compromise for getting a well-fermentable wort, not a universal law for any malt.

Option 2. Saccharification with industrial enzymes

The enzyme method is convenient for unmalted grain. Usually a heat-stable alpha-amylase is used for liquefaction and glucoamylase for the further production of glucose. Names and regimes differ between manufacturers, so the dosage, pH and temperature are taken only from the data sheet of the specific product.

The general sequence looks like this: cook or gelatinise the starch according to the requirements of the grain, add alpha-amylase at the specified temperature, then cool the mass to the glucoamylase range and hold it for the required time. Some products allow saccharification at the same time as fermentation — this is a separate technology, not a reason to add enzymes “by eye”.

For corn and some rye mashes, simple heating to 63–65 °C may not be enough: the gelatinisation temperature of starch depends on the grain. If the starch has not become accessible to water, the enzymes cannot work properly. This is one of the reasons why the technology for wheat cannot be transferred to corn unchanged.

An example wheat mash from a forum thread

The translation of Ian Smiley’s recipe gives 4 kg of pre-processed wheat flakes, 0.75 kg of crushed wheat malt and 23 l of water. Saccharification is done at about 65 °C for 90 minutes. That is about 4.8 l of water per kilogram of total grist — a thinner mash than the 1:3 guideline above. The 30 l of mash stated by the author is not equal to the volume of clean wort after the spent grain is separated.[1]

For fermentation the original specifies yeast with added amyloglucosidase (AG). So this is not a proven malt-only recipe: the additional enzyme takes part in producing fermentable sugars. If you replace the flakes with raw grits, a different preparation is needed; if you replace the malt, check its enzymatic activity. The yield and fermentation time stated in the source are not guaranteed.[1]

Cooling and preparing for fermentation

After saccharification, quickly cool the wort to the pitching temperature specified by the manufacturer. Do not add yeast to hot mash: high temperature damages it. The working range may differ for different strains, so the “30 °C” value from one commercial recipe cannot be considered universal.

A thick mash can be left with the spent grain if the chosen technology allows it, or the liquid wort can be separated. Before transferring, make sure the fermentation vessel is clean and has free volume for foam. If necessary, the wort is aerated before pitching the yeast, but after fermentation begins extra access to air is not needed.

Fermentation

Add healthy yeast in the amount specified for the particular strain and wort volume. Close the vessel with an airlock: carbon dioxide must be able to escape, but air and contaminants must not get in freely. The fermentation vessel must never be sealed airtight.[6]

• keep the temperature in the range recommended by the yeast manufacturer;
• measure gravity with the same instrument each time, applying its temperature correction;
• do not rely only on the bubbles in the airlock — they may stop because of a leaky lid;
• do not hurry to consider the wash ready by the calendar: the time depends on the starting gravity, the sugar composition, the strain and the temperature;
• if fuzzy mould, coloured spots, slime or a sharp putrid smell appears, the batch is not distilled or tasted.

Gravity is checked again, for example after 24–48 hours. This is a practical observation interval, not a mandatory fermentation time. Stable readings are compared with the expected attenuation of the particular wort: a high, unchanging gravity may mean the yeast has stopped. In that case check the temperature, pH and the condition of the culture. For measuring, take a liquid sample without spent grain, remove gas bubbles and account for the calibration temperature of the instrument. The iodine test only answers the question about starch and does not show whether alcoholic fermentation has finished.

Clarifying and preparing the wash

After fermentation ends, let the solids settle. If necessary, the wash is chilled or a food-safe fining agent is used according to its instructions. Racking off the sediment reduces the amount of suspended matter, but does not turn a doubtful or infected wash into a safe one.

Grain suspension can settle on a heated surface and scorch. Before further processing, separate the thick spent grain in the way provided for by the design of the equipment. Do not clog filters and steam channels with dense mass: a clogged steam path is dangerous because pressure builds up.

Safety

• Hot mash and steam cause severe burns. Transfer it only with suitable equipment and do not open a heated sealed system.[6]
• Carbon dioxide is released during fermentation. Do not put a large vessel in a small unventilated room and do not lean over the neck with your face.
• Before any subsequent distillation, check that the steam path is free, the connections, the cooling, and that there is no overfilling. The steam path must never be blocked.
• Ethanol vapours are easily flammable. Rule out smoking, open flame and sparks; a gas flame is especially dangerous near the apparatus.
• Do not leave heating and cooling unattended. If the water stops, there is an unusual noise, liquid is ejected or there is a smell of overheating, turn off the heat in a safe way and wait until it has cooled completely.
• Mouldy grain and wash with signs of mould are not used: mycotoxins may remain after processing.

Typical mistakes

• Yeast added to hot wort. First measure the temperature, then add the culture according to its instructions.
• The wort stayed starchy. Check with iodine and adjust the milling, temperature, pH or enzyme regime.
• Took the dosage from somebody else’s recipe. Enzymes and yeasts have different activities; follow the product data sheet.
• Closed the vessel tight. Fermentation needs a way for carbon dioxide to escape through an airlock.
• Started further processing based on bubbles. The end of fermentation is confirmed by repeated gravity measurements.
• Used mouldy grain. Such a batch is not “cured” by boiling or distillation.
• Left a lot of spent grain before heating. Thick suspension can scorch and block the steam path.

What to write in the batch log

Record the grain and its mass, the type of malt, the water volume, the names and dosages of products. During the work note the actual temperatures and the length of rests, the pH with the sample temperature, the result of the iodine test, the starting and final gravity, and the fermentation temperature. These records will help you understand the cause of an incomplete fermentation or low yield and repeat a successful batch.

A short process sheet

1. Choose clean food-grade grain and mill it.
2. Prepare the water and clean equipment.
3. Cook the starch if the grain and the chosen enzyme require it.
4. Saccharify the mash with malt or enzymes in their working range.
5. Check that no starch remains with the iodine test.
6. Cool the wort to the pitching temperature.
7. Add the yeast and ferment under an airlock.
8. Confirm the end of fermentation with repeated gravity measurements.
9. Clarify and separate excess spent grain before further processing.

Sources and limitations

The practical basis of the article is a discussion of wheat mash on the HomeDistiller forum. The process parameters were compared with materials from Distiller Magazine and the American Homebrewers Association on starch gelatinisation, the action of alpha- and beta-amylase, and the influence of temperature and pH. General information on raw materials and mycotoxins was checked against WHO materials. The rules of the specific enzyme product, yeast and equipment take priority over the general guidelines of this article.

[1] HomeDistiller: All-Grain wheat vodka and discussion of the technology

[2] Distiller Magazine: Mash Chemistry 101

[3] American Homebrewers Association: Enzymes in Beer

[5] Chattermark Distillers: Our Process

[6] DistilCalc: Safe Distilling Practices

[9] WHO: Mycotoxins

This article describes preparing grain wash for personal use. Before any further processing, check the legal requirements of your country and region. Do not consume a product of unknown composition and seek medical help if poisoning is suspected.