Does Seasoning Order Matter? Testing Sashisuseso

There is an official order and there is a stated reason attached to it, and the two are worth reading separately. Both come from one government description of washoku seasoning, quoted in full below, and what the diffusion literature can and cannot say about that stated reason is the rest of this post.

Start with what the rule actually is, in full.

Japan's Ministry of Agriculture, Forestry and Fisheries describes sashisuseso, the basic seasonings of washoku, as sugar, salt, vinegar, soy sauce, and miso, and states that this is not merely a list of seasoning types but the order in which they go into a dish: sugar goes in ahead of salt because its molecules are larger, vinegar comes next so that a moderate acidity is left, and soy sauce and miso are used last, partly for the sake of aroma.¹

So the sequence is stated as a sequence, not just a list of five things. Sugar first because of molecule size, vinegar next to keep some acidity alive, soy sauce and miso last to keep their aroma. The aroma part is easy to accept: heat drives volatiles off, so late is better. The size part is the one worth pushing on.

What diffusion studies do show

Salt moving into meat has been measured carefully, and the first finding is that the rate is not a fixed property of salt.

In a published study of wet salting pork, salt diffusion coefficients at 15 degrees Celsius ranged from 1.99 to 2.33 times ten to the minus tenth square metres per second while at 1 degree Celsius they ranged from 1.33 to 1.54, and the authors attributed the difference to modifications of the viscoelastic properties of the pork that increase the permeability of cell membranes with increasing temperature.²

Warmer means faster, by a factor of roughly one and a half across that range. And the shape of the journey has been mapped as well.

In a published simulation study of cured pork tenderloin, the sodium chloride content at the meat surface increased rapidly from 0 to 1350 moles per cubic metre over the first 12 hours and then increased slowly as the diffusion distance grew, with the salt reaching a position 10 millimetres from the surface after 12 hours.³

Fast at the surface, then slow going inward. Twelve hours to reach a centimeter, which is a useful reality check against expecting a marinade to season a thick cut all the way through.

The part that touches the sugar claim

One study came at the question from the side, by dissolving something else in the brine and watching what happened to the salt.

In a published study of cured pork tenderloin, the effective diffusion coefficient of sodium chloride fell from 1.29 to 1.22 to 1.2 to 1.15 times ten to the minus ninth square metres per second as added xylitol rose from 0 to 4 to 8 to 12 percent by weight, so a polyol dissolved in the curing liquid measurably slowed salt transport.⁴

So one dissolved sweet-tasting molecule measurably slowed salt down. That is consistent with the traditional rationale in spirit, though xylitol is not sucrose and a curing brine is not a simmering pot. It is support by analogy, not proof of the original claim.

Where the evidence stops

The same authors were careful to fence in what their numbers cover, and that fence matters here.

In a published study the authors warn that their salt diffusion coefficients are applicable only to the same pork cut under similar processing conditions, since the coefficients do not fully represent the complexity of the water, salt, and solid matrix and depend on factors such as brine pH, stirring, and sample dimensions.⁵

Different cut, different pH, different stirring, different numbers. So the honest verdict is that the aroma half of sashisuseso rests on straightforward physics, while the sugar-before-salt half is traditional guidance that the diffusion literature gestures toward without settling. Following it costs nothing.

Test it on one dish

This one is easy to run because the order is the only thing you change, and a simmered dish holds still long enough to judge.

• Make the same simmered dish twice, same ingredients, same weights, same pot.
• In the first, add sugar, then salt, then vinegar, then soy sauce, giving each a moment before the next.
• In the second, add everything at once at the start.
• Cook both for the same length of time at the same heat.
• Taste them side by side, paying attention to the soy sauce aroma first since that is where the clearest difference should be.
• If you cannot tell them apart, that is worth knowing too. The aroma effect is the one most likely to show up in a home pot.
• Serve whichever one you liked with rice and let the experiment become dinner.