November 27, 2007

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Does Soy Sauce's Flavor Gradually Dissipate?

Have you ever noticed this phenomenon? You put soy sauce on your rice, begin eating, it's delicious, but then five minutes into the dish, you find that it no longer has enough soy sauce flavor? I have noticed this with multiple brands of soy sauce. So I conducted some experiments.

First I thought the rice might just be absorbing some of the soy sauce, dulling the overall soy-sauce flavor of my bites. So I tried it on things other than rice. Still happened.

Second I thought I might simply be building up a tolerance to the soy sauce very quickly. The same thing can happen with plain old salt: by the end of a very salty meal, it no longer tastes all that salty. But that effect can usually be negated by interspersing bites or drinks of a palate-cleansing astringent. So I tried the same with soy sauce. Every few bites of your soy-sauce-flavored food, take a minute to cleanse your palate, say, by sucking on a lemon, or by eating some bitter greens, or drinking some water mixed with baking soda (strongly basic). The soy-sauce flavor still dissipates!

It isn't too hard to believe that a very aromatic food gradually loses its volatile flavor and smell compounds--it happens to everything. That's why freshly ground spices, or coffee, taste much better than those bought pre-ground; the volatile chemicals that provide the aromas and flavors are gradually lost once the whole spices, or whole beans, are ground. But in the case of soy sauce, it seems less likely.

First, soy sauce is usually stored in bottles that are not airtight. If it loses so much flavor within five minutes of pouring it out of the bottle, why doesn't it lose more flavor in the two years that it sits in the cabinet? Obviously when your pour it out it vastly increases the surface area over which the volatile compounds can be lost, but would that cause so much more flavor dissipation than years of sitting in an open bottle, occasionally being shaken?

Second, it happens so quickly! Spices stay fresh for a week or two at least after being ground, and coffee stays fresh for at least a few hours. But maybe because the soy sauce is a liquid, it more efficiently dissipates some of its compounds?

Third, other liquid sauces similar to soy do not dissipate their flavors so quickly. Olive oil, for instance, changes its character immensely over time, but not nearly as quickly as soy. The olive oil you buy in the store is probably several years old. But "freshly-pressed" olive oil, as can be bought from small artisanal makers at farmers' markets, is still fresh (and super fruity and delicious) after a couple months. Fish oil, a sauce that has several things in common with soy sauce (they're both Asian sauces which are fermented and can be stored in non-airtight containers) is basically good forever, as far as I know.

So there remain a few experiments that might confirm my suspicions and further explicate the matter:

1) Prepare four identical dishes, with each containing, say, 1 cup of cooked rice. For two of them, keep the rice hot, and for two of them, let it cool to room temperature. For one of the hot dishes, and one of the cool dishes, pour in 1 tsp soy sauce each. Wait ten minutes. Then for the second hot rice and the second cool rice, pour in 1 tsp soy sauce each. Taste all of them immediately, and compare.

2) Do the same thing with a balsamic vinegar, which is probably one of the most similar sauces to soy (dark color, fermented, similar viscosity and density), but which is considered to improve with age.

3) Try very high-end soy sauces, to see whether they do the same.

4) Explore alternative methods of storing and serving soy sauces. For instance, vacuum-seal the soy sauce in airtight packages which allow very little osmotic transfer. For serving, explore methods in which the flavor of soy is somehow contained and then meted out either over time, or whenever the diner wants it. For instance, spherified soy sauce balls made from dropping small drops of a soy sauce and sodium alginate solution into a calcium chloride bath. Or if one could contain soy sauce in some kind of reversible matrix the same way the proteins in meat coil up during cooking to trap the juices, but then release them when cut or chewed. Any other ideas?

Posted at November 27, 2007 2:33 PM | Comments (10)


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Is Eatfoo officially dead? This would have been a good food post...

Posted by: Cara at November 27, 2007 10:06 PM


Are you using fermented or acid-hydrolyzed soy sauce? The latter has a bunch of compounds that aren't supposed to be there and that might react badly with flavor compounds upon heating. And with the latter, all the proteins have been broken down into amino acids, which are smaller and can boil off more easily. The longer-chain proteins that stick around during fermentation may help brewed sauces hold their flavor for longer.

Posted by: Jeff at November 28, 2007 5:53 PM


Just did a little experiment of my own. I left soy sauce out for 10 minutes and compared it to stuff fresh out of the fridge - no difference. Then I nuked one of them - the heated one definitely had a milder flavor. I think the saltiness isn't as powerful, though my palate isn't all that sophisticated so I don't really know how to describe the difference. All I know is that there was one, after seven seconds in the 'wave. So the heat is doing something.

(Caveat: I use the low-sodium stuff.)

Have I mentioned that tasting straight soy sauce is icky? Yech.

Posted by: Jeff at November 28, 2007 6:11 PM


Jeff, I love straight soy sauce. I must confess that I didn't know the cheaper stuff was not fermented! However, I have tried this with several brands, including one of the expensive, gourmet, organic, "Naturally Brewed" soy sauces from Whole Foods. The protein chain length theory does make sense, though.

As for the salt content being lower, that does not make sense. Generally, heating only intensifies saltiness because our perception of saltiness depends mainly upon concentration. Heating for a long time evaporates some of the liquid, raising the concentration of salt. 10 seconds in the microwave wouldn't have a noticeable effect on concentration, but we also perceive all (as far as I know) flavors as being stronger when they are present in warm food. Cold foods have to be more flavorful than warm ones or else they taste bland. Another reason why the soy-sauce phenomenon just doesn't make sense.

Posted by: Barzelay at November 29, 2007 1:16 AM


Cara, EatFoo is not officially dead, but it's definitely in hiatus, at least for me. No one else posts to it except Betty now, and she is going to start her own food blog. I've got about fifty food posts that just need writing (most of them with pictures ready to go), and I just have been putting them off over the past year or so because no one reads EatFoo because I never really hyped it around the internet because no one wrote on it. The plan is that, over Christmas break, I'm going to write up a whole bunch of EatFoo posts, and then trickle them out over the first month or two of the year, during which time I'll try to get some attention. I'm also going to invite some new authors. I'd be honored to have you writing again at that time.

Posted by: Barzelay at November 29, 2007 1:19 AM


Also, Jeff, when you say you "left it out for ten minutes," what do you mean? Poured it into a bowl, or poured it over a food? It may make a difference, because pouring it over a food is likely to increase it surface area by much more than pouring it into a bowl. Resting in a bowl isn't much different from resting in a soy sauce container; in both cases the soy sauce is not very spread out? Right?

It's also possible that microwave radiation could have a different effect from, say, boiling on a stove. The dielectric heating of a microwave would affect a sauce without much fat (e.g., soy sauce) much more than the it would affect a fatty sauce (i.e., beurre monté).

Posted by: Barzelay at November 29, 2007 4:39 AM


Yeah, it was in a bowl, and yeah, pouring it over food would increase its surface area since it's basically like separating the sauce into craploads of little droplets.

Anyway, there are only a few explanations for why flavor would dissipate. Let's run them down:

1) Flavor compounds are removed from the sauce. I know of no flavor compounds that are that volatile. It'd have to be acetone-like volatility, which just wouldn't happen with flavor compounds, which tend to be complex and fairly heavy.

2) Flavor compounds break down upon mild heating. Again, the chemistry doesn't make sense here. There could be some sort of bizarre reaction occurring that gets pushed over the activation energy barrier at a temperature between 25C and 40C, but how likely is that?

3) Soy sauce's flavor compounds react strangely with food. Possibility.

4) Heat masks a portion of the soy sauce flavor. You'd know more about the effect of heat on one's palate than I would - perhaps it restricts a taste that is more prominent in soy sauce than elsewhere. Though if heat intensifies all flavors, that wouldn't be sensible.

3) looks like the most likely to me. Maybe some of the free amino acids in soy sauce hook up with compounds in the food and sacrifice their flavor in the process. But yeah, this is quite the conundrum.

Posted by: Jeff at November 29, 2007 5:22 AM


Along the same lines, here's a possibly simpler explanation. It is thought that one of the main reasons salt makes things seem more flavorful (and not just more salty) is that "salt increases the ionic strength of aqueous solutions, making it easier for odorant molecules to separate themselves from food." Herve This, Molecular Gastronomy: Exploring The Science Of Flavor, p. 94 (2006).

My chemistry background is fairly weak, but perhaps the food is stealing some of the ions from the soy sauce, resulting in a perceived weakening of its odor and flavor because fewer of those compounds are released?

Posted by: Barzelay at November 30, 2007 1:45 PM


Your initial experiment is flawed. You have to taste the soy sauce independently of everything else. If you try the soy sauce by itself and it doesnt seem to lose flavor, then you can conclude that it has something to do with the food you put it on. Else, the soy sauce loses flavor in and of itself for some reason. If the former, the solution is simple: apply soy sauce in limited quantities, eat all the soy'd up food, and reapply. If the soy loses flavor independently, then you can start to experiment with the other variables; heat, time, etc.

Posted by: Chris Santoro at November 30, 2007 8:47 PM


I checked, and one of the soy sauces tested is definitely brewed, from a mixture of soy and wheat.

Posted by: Barzelay at December 3, 2007 1:42 AM

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