![]() The number 145 represents the maximum amount of dissolved solids (sugar) that can be dissolved in water. This is a measure of the dissolved solids in the liquid. Second, we need to calculate the Apparent Extract with (145 - 145 / SG). Let’s break this formula down which is based on several empirically derived constants:įirst we multiply the ☋x by 1.646, a constant that represents the conversion factor between ☋x and ABV accounting for the dissolved sugars in solution. However in sake, there are actually dissolved solids (sugars) which will increase the density of the liquid, and result in an incorrect ABV. could tell us exactly the % of alcohol because there is a direct correlation of an Ethanol and Water solution to density. If there was nothing but alcohol and water in the liquid, the S.G. represents the density of the liquid compared to the density of water. (specific gravity) into the following formula:Īs stated earlier, ABV represents the percentage of alcohol in a given volume of liquid, ☋x is a measure of sugar concentration, and S.G. This is because alcohol also contributes to the refractive index of the sake, and thus many different combinations of sugar % and alcohol % can lead to the same refractometer ☋x value.Īlcohol Content can be estimated by entering the ☋x (brix) and S.G. ![]() For this reason, we cannot simply apply the common assumption that fermenting 1 degree Brix of sugar will produce approximately 0.55% to 0.6% Alcohol by Volume (ABV).īrix measurements are further complicated by that fact that once the level of alcohol begins to increase due to fermentation, independent refractometer assessments no longer yield an unambiguous proxy measure of sugar content. Please refer to the A/B Line article for more information on tracking your fermentation progress. Unlike wine and beer that have an “original gravity” and “current gravity” that tell us how much sugar has been converted to alcohol, the presence of active koji enzymes in the mash mean that sake’s gravity can actually increase as the fermentation progresses. just use the Estimation method and based on our side-by-side tests, this is accurate within about a 0.6% ABV margin of error, which falls within the 1% range currently allowed as of 2023. However, it should be noted, that several commercial brewers in the U.S. Commercial brewers should use Distillation or Ebulliometry methods because they are more precise for regulatory matters and require more expensive equipment. The easiest and least expensive method (~20USD) is Estimation and is recommended for homebrew. The most common forms of measuring Alcohol are Distillation, Ebulliometry, and Estimation. *Beer brewers and Wine makers should not skip this section.Īlcohol content is typically measured in terms of Alcohol by Volume (ABV) and is represented by a percentage of the overall liquid. The following are ways to measure glucose during your fermentation and also after pressing. This one provides more clarity that you may or may not feel is relevant to your process. While measuring Brix can estimate total sugar content, a more accurate measurement of glucose levels can help us get a better sense of our koji performance (ex: relative enzyme makeup), sense of flavor balance, as potential decisions for when to press. For sake, we use the heavier scale because it is used early in fermentation when there are lots of dissolved solids (mostly sugars) ☋ is a more complicated measurement and has two separate scales for liquids heavier or lighter than water. It represents the ratio of the mass (weight) of a given volume of liquid to the identical volume of water. SG is the most commonly used scale to express liquid density and is measured using digital or analog hydrometer. This value is also commonly referred to as the Nihonshu-do SMV is measured using specialized hydrometers at 15☌ (ex: +15 to -40 SMV). This is an extremely important metric to track the fermentation progress of sake because the increase and decrease of density due to sugar and alcohol concentration helps us make corrections to temperature and water ratios to control yeast health and potential alcohol. (specific gravity), SMV (sake meter value), and ☋ (degrees Baumé) are all relative measures of a solution’s Density. Sample Ferment examples (acidity, temperatures, etc.) While the science is fundamentally the same, the literature you might encounter will often use specific metrics that common in Japanese sake production and so this can serve as a primer to explain those and how to interpret graphs and charts you see. You’ll find conversions and equivalents to beer and wine mostly. This page tries to explain how sake is measured and how that might differ from other types of fermentation.
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