This section describes how to make 30L of corn mash (approximately 20L to be distilled after straining) in a large pot on a kitchen stove. This will yield approximately 2L of 45% alc/vol corn whiskey plus about a litre of feints. It is highly recommended that you not attempt to scale this procedure up to a larger quantity until you have familiarized yourself with the process by mashing this smaller quantity two or three times.
• a large plastic or wooden stirring spoon
• a floating dairy thermometer, graduated from 0oC to 110oC (32°F to 230°F)
• tincture of iodine
• measuring spoons
• 23L of fairly soft municipal tap water. E.g. hardness level of 4; almost no iron; 100 ppm calcium; pH 8.5.
• 95% sulphuric acid (H2SO4); or, citric or tartaric acid
This method is one of the simplest and least time consuming methods of mashing. Also, it scales up to large mashing quantities very well.
The principle behind this method, which is a single infusion-mash method, is to use flaked maize rather than undispersed hard grain such as corn meal. This eliminates the need to perform a full boil to disperse the grain starches.
With flaked maize, which is already-dispersed corn that is hot-rolled the way rolled oats are made, the grain starches easily disperse into the 65.5oC (150°F) mash water without the need of boiling.
See "Appendix A - Other Mashing Methods" for procedures on how to mash other types of grain and hard cereal grains (i.e. non-flaked grains).
Prepare the mash water by placing 23L of tap water in the large pot on the stove. Thoroughly mix the 10-ml (2-tsp) of gypsum into the water, and measure the pH using the range 2-12 pH papers. Use this pH measurement to determine what pH adjustment the water requires.
Let's assume the pH, as with most municipal tap waters, is approximately 8 or 9. Begin adding 95% H2SO4 one drop at a time, mixing thoroughly, and measuring the pH with the range 5.0-6.5 pH papers between each drop until the pH is 5.8.
If citric or tartaric acid is used, which are both powders, the additions should be 1W ml (W tsp), and will take about 10 ml (2 tsp) or so in total to achieve pH 5.8 to 6.0 from a source water of pH 8.5.
If you accidentally overshoot pH 5.8 with the acid, you can correct by simply making additions of 500 ml of source water (i.e. pH 8 or 9) and measuring the pH, until the target pH of 5.8 is achieved. Once this correction is complete, it will be necessary to remove a total equivalent volume of mash water as was added to do the correction and discard it, leaving 23L of mash water at pH 5.8.
Of course, if the pH of the source water were below 5.8, the water would require treating with calcium carbonate (CaCO3) instead of H2SO4. Similarly, an accidental overshoot can be corrected the same way with additions of the source water.
After the mash water is prepared, turn the stove on high, cover the pot, and let the water heat up to the conversion strike temperature, 74oC (165oF). You will have to periodically stir the water thoroughly and measure the temperature as the water heats up until the strike temperature is reached.
When the water is at the strike temperature, turn off the heat, and stir in the 7L of flaked maize. The temperature should come to rest at about 68oC (155oF) or higher. Stir the mash for about five minutes while the starches disperse (i.e. gel into a thick porridge). It should take about 15 to 25 minutes for the temperature to cool to 66.5oC (152oF). The mash should be stirred every five minutes or so until it cools to that temperature. When the mash is at 66.5oC (152oF), stir in the 1/L of crushed barley malt and the 5-ml (1-tsp) of gluco-amylase. The mash temperature should rest at 65oC (149oF).
Cover the mash pot and leave it for 90 minutes or longer for the starches to convert to sugars. It's helpful to stir the mash every 15 minutes or so during the 90-minute conversion rest. The mash can even be left for eight or ten hours (e.g. overnight) to cool to fermentation temperature (i.e. under 38oC (100oF)). Or, an immersion chiller can be used to force cool the mash to fermentation temperature after the 90-minute conversion rest is complete.
After the conversion rest, the starches should be completely converted to sugars. This can be tested for by the iodine starch test described above.
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