San-do – Home Brew Sake

A friend¹ helped me to understand the chemistry behind these characteristic sake parameters; san-do (acid level) and amino san-do (amino acid level). It is not that complicated once the basics are explain but without understanding the basics it is impossible to really know what is going on.

Foundational concept: the mole. A mole is a quantity of objects like a dozen. It allows us to map reactions between individual molecules and atoms and more manageable quantities like grams and liters. One mole of hydrogen is 1 gram. Hydrogen is the simplest and lightest atom with one proton and one electron. The electron weight is so small it is insignificant in comparison to the proton. So the proton as hydrogen itself has an atomic weight of 1. Each atom has an atomic weight, ignoring electrons, equal to the number of protons and neutrons it contains. The neutron weighs the same as the proton.

A carbon atom has 6 protons and 6 neutrons and thus has an atomic weight of 12. Because the carbon atom is 12 times that of hydrogen one mole of carbon would also be 12 times the weight of hydrogen or 12 grams.

Foundational concept: molarity or moles/Liter. To create a one molar solution (solution of one molarity) of carbon in water simply place 12 grams of carbon in a one liter container and add water until reaching the one liter level. When we talk about the concentration of elements based on chemical reaction equations we do so in molarity or moles per liter. Continue reading “The chemistry behind the measurements – San-do and Amino San-do”

My fried is Jonathan Musther of New Zealand. ↵

In part one I talked about how to measure the Nihonshu-do or Sake Meter Value (SMV) or your sake. In part two I covered how to measure the Arukoru bun (アルコール度数) or Alcohol percent by volume (%ABV). In this part, part three I will discuss how to measure the san-do or acidity of sake.

To measure the san-do (acidity) of sake at home, there are two very closely related methods available. The easier and less expensive of the two methods is to use a wine acidity test kit. This kit contains almost every think you need to measure the acidity on sake. However, there is a difference getting from the physical test to the interpreted value, but I am getting a little ahead of myself. The second method differs from the first in that a pH meter is used rather than Phenolphtalein to determine the point of neutrality. Often the second method employs more sophisticated equipment for each of the components but this is not strictly necessary.

So, what do wine acid test kits come with? Well, they come with a small beaker to mix the sample and chemicals in, a syringe to measure with, a solution of Sodium Hydroxide, usually at a concentration of 0.1 Molarity (M) and Phenolphtalein. The idea behind the test is that we have some unknown amount of acid in our sample that we want to measure. To do this we add a known amount of base to neutralize the sample pH. When we have neutralized the sample pH with a known amount of base we can then work out the original amount of acid. Clear as mud? Perhaps an example will help.

Continue reading “Measuring your Sake – Part Three: San-do (酸度)”