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Can cornstarch get too old?

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Thickening with cornstarch has always been hit or miss for me - today I thickened some fabulous (IMHO) lamb jus (about 1.25 cups) with the properly done slurry of cornstarch (1 tbsp CS/1 tbsp cold water) ...... and nothing material happened.

I served it anyway - it was delicious but I would have liked it to be thicker. Reducing it further wasn't an option because the flavour was perfect.....reducing it would have made it too salty/too acidic.

I make a great roux for gravy but didn't want that effect for the lamb jus.....maybe try arrowroot?

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  1. I have never had cornstarch lose it's thickening properties from age.
    Did come back to a Boil?
    Acids can reduce corn starches ability to thicken.
    Whisking to vigorously can make it not work, but it usually thickens first and then thins out.

    2 Replies
    1. re: chefj

      Not a hard boil.....I thought that thinned it out again?

      Maybe it's the acid.....there was a fair bit of red wine in the jus

      I didn't whisk hard - but it didn't thicken off the top at all.

      Maybe cornstarch is just my nemesis! Thanks for the thoughts.

      1. re: ElizabethS

        You need to be at a full boil for a minute or so for it to properly thicken. The recommended ratio is 1 TB to 1 cup, so you may have just needed more cornstarch.

    2. My favorite for thickening is a buerre manie.. A mixture of flour and softened butter. You just keep adding at the end until you have the desired consistency. You do get a nice butter flavor.... Not sure if that's what you want.

      1. MIL used arrowroot never corn starch. I've never used arrowroot rely on corn starch.
        can it lose its' umph, prob. it's only about a buck-I'd toss yours & get a new Argo.
        jmo