Does Matcha Powder Expire?

Yes — and the date printed on the package refers to the unopened product. Once opened, a different clock starts.

Unopened

Matcha products commonly carry a best-before date six months to a year out.

Sweetened versions are sometimes given longer, since sugar binds free water in a product and slows deterioration — the same principle behind preserved fruit.

The specific date is on the package.

After opening

This is where the gap appears. Sellers of matcha typically suggest two weeks to a month once a package is opened.

A best-before date six months away does not change that. From the moment air reaches the powder, color and aroma begin shifting.

Why the difference is so large

Matcha is finely milled leaf. Particles run around 10 microns, and finer grades reach 1 to 5 microns — roughly an order of magnitude smaller than wheat flour at 30 to 60 microns.

More surface area means faster oxidation and faster loss of volatile aroma. Whole-leaf sencha holds up much longer for exactly this reason.

Past the date

A best-before date indicates quality, not safety. Nothing dramatic happens on that day.

But color dulls, aroma thins, and flavor flattens. Stop if you notice an off smell, visible clumping from moisture, or anything resembling mold.

Buying with this in mind

Larger packages cost less per gram and mean nothing if you cannot finish them.

At 20 g per serving, 300 g is 15 cups — about two weeks daily, roughly two months at twice a week. Choose a size that fits inside the post-opening window, and the per-cup math actually holds.

Writing the opening date on the package with a piece of tape removes the guesswork.