How long does wagashi last?

The honest answer runs from a single afternoon to more than a year, and the word wagashi covers both ends. A nerikiri shaped like a chrysanthemum is meant to be eaten the day it is made. A bar of yokan from the same shop can sit in a cupboard until next autumn. What separates them is water.

Fresh wagashi (namagashi) lasts one to three days and should be eaten on the day you buy it if you can. Semi-dry wagashi lasts from about a week to a year: castella from one to several weeks, yokan six months to a year unopened. Dry wagashi and sugar candy last from two months to a year. Do not refrigerate mochi or sweets made with bean paste unless the packet tells you to, because the cold makes them hard; eat them the same day, or wrap and freeze. Once any sealed sweet is opened, treat it as fresh.

Real dates, from real packets

Most guides give you ranges. This month I went through the stated shelf life of Japanese sweets from a couple of dozen makers while choosing what could travel in a box, and the actual dates are more useful than any range. These are the makers' own figures where they publish them.

Look at the castella rows. The same sweet runs from about ten days to eight months depending on the maker and the packing. That is the real lesson of the table: the category tells you very little, and the date on the packet tells you everything.

Two kinds of date on a Japanese packet

If you buy sweets in Japan, or from a shop that keeps the Japanese label, you will see one of two dates, and they do not mean the same thing.

• Shōhi kigen (消費期限) is a use-by date. It appears on food that spoils quickly, usually within about five days, which is most fresh wagashi. After it, do not eat the sweet.
• Shōmi kigen (賞味期限) is a best-before date. It appears on food that keeps longer, such as yokan, candy and most packaged castella. It marks how long the maker promises the sweet will taste as intended, unopened.

Both assume the packet is sealed and stored as printed. Once you open it, the date no longer applies.

The chestnut sweets of autumn are a good example of fresh sweets made for their season; I describe them in autumn Japanese sweets with matcha.

If you are choosing a box of sweets from Japan, here is how to tell a Japanese snack box from a wagashi box.

Should wagashi go in the fridge?

Usually not, and this is where most people go wrong. Mochi and bean paste are made of starch, and starch stiffens in the cold. It happens fastest at ordinary refrigerator temperatures, just above freezing. A daifuku that was soft at noon is hard and grainy by the next morning in the fridge, and it does not fully come back.

So the choices for a fresh sweet are simple:

• Eat it today. That is what it was made for.
• If you cannot, wrap it tightly and freeze it. Freezing passes through the stiffening range quickly and stops it. Thaw at room temperature, still wrapped, for a couple of hours.
• Refrigerate only if the packet says so. Some sweets with cream, fruit or custard must be kept cold, and the label will tell you.

Yokan keeps unopened in a cool cupboard. Once cut, wrap the rest tightly and keep it in the fridge, and eat it within a few days; the cut face dries and weeps sugar if it is left out. Dry sweets and candy never need the fridge. Their enemy is damp, not warmth: keep them sealed, and kohakuto in particular will lose its crisp shell in a humid kitchen.

Questions I get asked

How long does wagashi last?

Fresh wagashi such as nerikiri and daifuku lasts a day to three days. Castella lasts from about ten days to eight months depending on the maker. Yokan lasts six months to a year unopened. Dry sweets and sugar candy last two months to a year. Always follow the date on the packet.

Does wagashi need to be refrigerated?

Most does not. Mochi and bean paste harden in the refrigerator, so fresh wagashi is best eaten the same day or wrapped and frozen. Refrigerate only if the label says to, and refrigerate yokan once it has been opened.

Can you freeze wagashi?

Yes, for fresh sweets made with mochi or bean paste. Wrap each piece tightly, freeze it, and thaw it at room temperature while still wrapped. Freezing avoids the hardening that happens in the refrigerator. Dry sweets and candy do not need freezing.

How long does yokan last once opened?

A few days. Wrap the cut bar tightly, keep it in the refrigerator, and eat it soon. Unopened, yokan commonly keeps six months to a year.

What is the difference between shōhi kigen and shōmi kigen?

Shōhi kigen is a use-by date for food that spoils within about five days; do not eat it after that date. Shōmi kigen is a best-before date for longer-keeping food, and marks how long it keeps its intended taste unopened.

Where this fits

Which sweets go with matcha, and why the sweet is eaten first, is in wagashi and matcha. The box I send each month includes a seasonal sweet chosen to keep well in transit, this month's page names it with its ingredients, and the tea and sweets set pairs a long-keeping sweet with a tin of matcha. The tea itself has its own clock, covered in how to store matcha.

Written by Mio.K, who chooses everything in this shop by hand in Japan.