Sake beyond sushi, and the acidity number that tells you which bottle to pour

Most people in D.C. meet sake at a sushi counter, and plenty of them never order it anywhere else. That is a narrow use for a drink that Japan's National Tax Agency describes as typically 15 to 16 percent alcohol, carrying organic and amino acids that it says make a sake taste dry, rich or light. Those three things decide whether a drink can stand next to a plate of food, and most importers print them as numbers on their technical sheets. This post is about one of them, acidity, and three foods that test it harder than raw fish does.

Why sushi got the reputation

There is a real reason sake and seafood get along, and the best evidence for it comes from wine. In 2009 Takayuki Tamura and colleagues at Mercian, a Japanese wine company, published a study in the Journal of Agricultural and Food Chemistry in which tasters ate scallops with 38 red wines and 26 white wines. The fishy aftertaste grew stronger as the iron in the wine went up, and it faded when the researchers added a substance that binds iron. They concluded that iron is the essential cause of a fishy wine and seafood pairing.

Sake brewers keep iron out of their water for reasons of their own. Sake Street, working from the Brewing Society of Japan's commentary on the national institute's standard analysis methods, lists the requirement for brewing water as 0.02 ppm of iron or less, preferably undetectable, and says brewers filter it out because it spoils the taste. Nobody I could find has repeated the scallop test with sake, so the connection is a reasonable guess and not yet a result. It helps explain why raw fish became the default pairing. It tells you nothing about what happens when the food is fatty, sour or aged, and that is where the acidity figure earns its place on the sheet.

What the acidity number measures

On a sake sheet, acidity is a small figure, usually somewhere between 1 and 2. It comes from a titration. Sake Street describes the standard method as taking 10 millilitres of sake and adding a 0.1 N sodium hydroxide solution until the pH reaches 7.2, and the acidity is however many millilitres that took. The NTA's page on the components of sake says the figure indexes organic acids such as lactic, succinic and malic acid, puts the average at 1.2 to 1.5, and notes that acidity makes sake taste dry and rich. Amino acidity, the figure sometimes printed beside it, averages 1.3 to 1.5 on the same page and tracks the amino acids that make a sake taste richer.

June's bottles spread across that range. Okunomatsu Tokubetsu Junmai publishes 1.4, right in the middle. Hatsumago comes in at 1.5 and Kurosawa Junmai Kimoto at 1.7, and both are kimoto, the old starter method in which lactic acid arrives from bacteria living in the brewery instead of from a bottle. Sake Street notes that lactic acid is especially prominent in kimoto and yamahai, and both of ours sit above the NTA average. Momokawa Pearl, which won the night, is listed by Blue Note Sake at 2.5, the highest figure of any bottle we have poured. Hananomai Katana and Murai Family do not publish one. Every published number for all six is on the score sheet.

Tomatoes, and the rule wine drinkers already use

The first rule in Wine Folly's pairing guide is that a wine with less acidity than the food will taste flat. A ripe tomato is about as hard a test of that rule as dinner offers, because it is sour and it is also full of glutamate. The Umami Information Center lists 246 milligrams of naturally occurring glutamate per 100 grams of tomato, and says the level rises as the fruit ripens.

Glutamate is an amino acid, and that is where sake has something to bring. A tomato salad, a margherita pizza or a pan of shakshuka wants a drink with enough acid to keep pace and enough savoury depth to meet the glutamate halfway. The sheet tells you which bottles have the acid. Pearl has the most, but at a sake meter value of -18 it is also very sweet, and sugar changes the picture in ways one number cannot capture. The two kimoto are the drier choice. Kurosawa's page carries the serving note that it reads lean and acidic when cold, and that cold version is the one to put next to a tomato.

Fried chicken and aged cheese

Fat is the other half of Wine Folly's guide. Fatty foods, it says, need either an acidic wine or one high in alcohol, or the wine will taste flabby. Sake arrives with the alcohol already, at the NTA's typical 15 to 16 percent, and a genshu, with no water added after pressing, carries more. Fried chicken is the case where that matters most, whether it is karaage at an izakaya or a box from a carryout. Reach for a bottle with acid and body and serve it cold. Hananomai Katana, a junmai ginjo at a sake meter value of +7, has the body to stand up to grilled food according to its serving note, and fried food asks for the same weight.

Aged cheese pulls in a different direction. The Umami Information Center gives Parmigiano Reggiano at 1,200 to 1,680 milligrams of glutamate per 100 grams, five to seven times what a tomato holds, and the cheese is salty besides. That points to the richest, most acidic bottle on the table, served warm. The post on serving temperature covers what warming does to a kimoto, and Kurosawa's serving note says that past 100°F its sweetness and the chocolate notes come forward. A hard cheese is the most forgiving place to try a warm pour for the first time, because the cheese is strong enough to cover a bottle that is not quite at its best temperature.

Most importers publish acidity on the technical sheet for each bottle, and some print it on the back label, which the post on reading a label walks through. If the number is missing, the starter method is the next clue, since a kimoto or yamahai builds its lactic acid slowly. A cold pour tells you little about any of this. Both kimoto finished at the bottom in June, and both are the bottles from that table worth reaching for first with a tomato or a block of Parmigiano. The October 30 tasting adds The Diplomat, a nama yamahai from Proper Sake Co. in Nashville, and if the brewery publishes an acidity figure for it, that number will go on its page next to the room's score.

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