I’ve read this canonical question about food safety, so my question is explicitly not about the safety aspect. I was curious if there were quality implications of storage of the sauce, and what the expected storage lifetime would be in the fridge.

Specifically, I’m making a mixture of:

Quantity Ingredient
2 Tbsp Low-sodium soy sauce
2 tsp Sesame Oil
1/4 cup Water
2 Tbsp Brown Sugar (packed)
2 tsp Corn Starch

Based on the linked question I would expect it to be safe in the fridge for at least 3-5 days, but I was wondering if there’s any weird interactions to be aware of, such as between the sugar, soy sauce, and corn starch that would degrade the quality even if it’s still safe to eat.

This is a sauce for a stir fry that is intended to thicken after being heated, and I don’t know whether the corn starch will still be effective after a few days, for example. I was hoping to be able to make a somewhat larger amount and cook with it over the course of a week or so. I plan on mixing these ingredients but not actually heating them until I actually add the sauce to the dish.

  • It's unclear from your description -- do you intend to cook the sauce (thickening it) before storage, or just to have the cornstarch mixed in and quickly settling to the bottom?
    – Sneftel
    Commented May 5, 2023 at 9:24
  • @Sneftel good point; it’s intended to be mixed but not heated until I actually want to cook with it Commented May 5, 2023 at 15:16

1 Answer 1


I would imagine your main enemy will be separation.

The oil will float to the top - which is easily if temporarily fixed by shaking it…

… but the corn starch will solidify at the bottom, which will require much more vigorous shaking, and may in fact resist all attempts short of disturbing it with a spoon/stirrer once it's fully settled. [It can do this in 20 minutes. I've never tried leaving it for much longer.]

As there seems to be some uncertainty as to whether you're going to cook it first… if cooked, the corn starch will gelatinise on cooling, which makes it rather intransigent afterwards.

  • What you call 'intransigent' I call 'homogeneous'. I'd much rather scoop thick sauce than figure out how to bring 1/4 of the corn starch up from the bottom to go with 1/4 of the sauce.
    – Sneftel
    Commented May 5, 2023 at 15:19
  • Hmmm, didn’t realize how finicky the corn starch could be. My plan was to use a squeeze bottle which would make vigorous shaking fairly simple, but it sounds like the corn starch might not mix even then Commented May 5, 2023 at 15:20
  • 1
    @fyrepenguin - try a couple of portions & see how it goes. Cornflour [cornstarch] is funny stuff at the best of times, its properties make it good for 'fun' scientific experiments too. Mix it really, really thick & if you push it it squishes, but if you hit it with a hammer it shatters. Google for videos if you don't want to try it yourself.
    – Tetsujin
    Commented May 5, 2023 at 15:41
  • 1
    @Tetsujin oh believe me, I’ve made both cornstarch and borax based non-Newtonian liquids. They’re fun as heck. Commented May 5, 2023 at 15:52
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    Reporting back; I've tried this a couple times since asking the question, and it works just fine. Some vigorous shaking successfully mixed in the corn starch as well as mixing in the oil. And yes, the sauce does gelatinize a bit on cooling, but it's basically a sauce for a stir fry, so that's more or less expected. Side note: I've discovered that the sauce (with a bit less sugar and soy and a tad more water) works shockingly well with scrambled eggs. added just before the eggs are done cooking. Looks ugly as heck, but tastes great Commented Feb 5 at 10:52

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