My icing (powdered) sugar has 97% sugar and 3% "maize starch".

Answers to a recent question accidentally ate raw corn starch say that corn starch, like wheat flour, is meant to be cooked before eating, but icing sugar isn't usually heated. Does this mean the starch is pre-cooked (or otherwise processed to kill any bacteria) or that this isn't really a worry?

  • 1
    Sugar itself is good at inhibiting bacteria so it might be that the 97% sugar content plays a role here.
    – dbmag9
    Commented Feb 9, 2022 at 8:58
  • @dbmag9 I would expect packed corn starch to be dry enough to prevent bacterial growth but the answers at the linked question are more concerned with pre-existing contamination of the starch
    – Chris H
    Commented Feb 9, 2022 at 8:59

1 Answer 1


It's raw.

Raw cornstarch generally shouldn't be eaten raw, due to risks of causing digestive issues . But it's relatively low-risk when consumed in micro-quantities.

Here's a recipe on YouTube on how to make icing sugar, and it uses 1 cup of sugar and 1 tsp of raw cornstarch: How To Make Icing Sugar At Home

Many other store-bought items also use cornstarch as an anti-caking agent, such as candies and shredded cheeses (some brands, not all).

  • 1
    In a very brief Google search and Wikipedia, I have not been able to find an authoritative source that claims there is any danger from bacteria or other health issues.
    – Rob
    Commented Feb 10, 2022 at 2:15
  • In addition, the water activity in non-cooked applications of icing sugar is generally too low to support bacterial growth (though it won't kill some type of pathogens), so you tend to get less risk of a high inoculum and as a consequence lower chance of disease. Icing has about 0.78 and most bacteria need over 0.9 to grow according to Bakerpedia
    – bob1
    Commented Feb 10, 2022 at 3:31
  • @Rob Updated to reflect your comment; you're right, the sites that stated it weren't necessarily reputable. Commented Feb 10, 2022 at 3:55

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