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Sake meter value (SMV), acidity level, and amino acid level


Two words used to describe sake are karakuchi (dryness) and amakuchi (mildness or sweetness). The dryness or sweetness of sake can be indicated numerically by two numbers: Nihonshu-do (sake meter value) and san-do (acidity level).


The sake meter value (SMV) is related to the amount of sugar in the sake. The acidity level is a measure of the quantity of acids such as lactic acid, succinic acid, etc.


The sake meter value and acidity level
The sake meter level (SMV) of a sake is a value calculated from its specific gravity relative to that of water. It is determined by the amount of sugar contained in the sake.


If the sugar content of a sake is high (i.e. the sake tastes sweet), it will have a negative value, while if the sugar content is low (i.e. the sake tastes dry), it will have a positive value.


Generally speaking, if the SMV is 5 or higher, it is considered to be dry. A value between 0 and 5 is taken as an indication of “medium dry,” while a negative value indicates “sweet.” However, the fact that the SMV has a high positive value should not be taken as necessarily indicating dryness. Sometimes a sake with a high positive value does not seem particularly dry.


That is because it is not only the sugar content that influences the perception of dryness and sweetness. The acidity level also plays a role.


For example, if an orange does not contain much acid, it tastes sweet. The perception of sweetness is influenced by the acidity level.


It is the same with sake. If the acidity level of a sake is high, it will make the sake taste dry, whereas if the acidity level is low, it will taste sweet. That is why, even if a sake has an SMV of 5, another sake with an SMV of zero can taste drier.


When determining the dryness or sweetness of sake, it is the sum of the two indicators, SMV and acidity level, that needs to be considered rather than just one or the other.


It is important not to give too much weight to these indicators. The right way to go about judging sake is to taste it with an open mind. The aim is not to look for faults like a professional sake taster, but rather to take the figures as a rough guide to the character of the sake.


Checking the acids present in the sake
The amount of acid contained in sake determines its flavor. However, it’s important to pay attention to the types of acid present as well. These acids may include lactic acid, succinic acid, malic acid, and citric acid.


For example, if lactic acid is present in cold sake, it will have a stimulating sourness, but warming the sake removes that sharpness so that it tastes quite mellow.


Two types of sake that are known for having high levels of lactic acid are those made according to the kimoto and yamahai methods. These types of sake have lactic acid bacteria naturally propagating, and this amount is increased during the brewing process. Even more lactic acid is then produced in the development of the kōbo (yeast starter culture).


Because of this, if these types of sake are consumed cold, they taste sharp. However, if they are warmed first, there is no sharpness, and the sake tastes refreshing.


Succinic acid is a constituent associated with umami or savoriness, and gives sake body. It is known as a constituent that gives sake a mellow sourness.


Apart from these, malic acid is found in fruits such as apples, and citric acid is contained in citrus fruits such as lemons. As you would imagine, these acids have a sharp sourness. If the sake is consumed cold, the taste is crisp, but if it is warmed, the taste becomes blurred. For this reason, these acids are often present in sake that is chosen to be served chilled in summer.


Amino acid level
Apart from the SMV and acidity level, there is another indicator known as the amino acid level (aminosan-do). This figure indicates the quantity of amino acids contained in the sake.


Generally speaking, if the quantity of amino acids is high, the sake will have umami (or savoriness) and body (or substance). If the level of amino acids is too high, the flavor will be strong and heavy. On the other hand, if the level is low, the flavor will be light and refreshing.


The outer layers of a rice grain contain a large amount of protein. Because proteins are composed of amino acids, if not much of the outer layer of the rice is polished off, the sake produced with it will contain a lot of amino acids. For sake types such as ginjō-shu, the aim is to remove as much as possible of any odd flavors, so the rice is polished to remove most of the outer layers. Doing so gives the sake a clear, refreshing taste.


Depending on the combination of factors represented by the sake meter value, the acidity level, and the amino acid level, the perception of dryness or sweetness, strength of flavor, and the feel of the sake in the mouth will all vary.

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