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I recently started making bread with a breadmaker and was wondering if it's safe to keep sterilized milk in the machine for a few hours before the program starts. I'm using the timer function to have a fresh bread ready in the morning. I know that it is recommended not to use perishable ingredients, like milk and eggs, when using the timer function. Does this also apply to sterilized milk?

Where I live, the average room temperature in summer is 28 degrees Celcius, which probably does not help.

Update: I did some more searching and found this:

When an increase and then a rapid decrease in heat occurs, bacteria such as lactococci and lactobacilli can form. [...] Milk actually spoils when bacteria converts the lactose into glucose and galactose, which results in the production of lactic acid.

http://ehow.com/how-does_4572637_what-makes-milk-spoil.html

Basically the question boils down to:

  1. Are these bacteria also present in sterilized milk?
  2. Can these bacteria be introduced from the air or from the bread flower?
  3. Are there other bacteria or toxins that will develop in sterilized milk when exposed to room temperature for a few hours?
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What's the average temperature in your kitchen at night? It should be lower than the quoted average temperature, which is probably the mid-afternoon maximum. –  Peter Taylor Jul 8 '13 at 8:19
    
NO. This is not a good idea. You are leaving perishable food out in the danger zone for an extended period of time. See: cooking.stackexchange.com/questions/34670/… –  SAJ14SAJ Jul 8 '13 at 11:13
    
I did some more searching. From ehow.com/how-does_4572637_what-makes-milk-spoil.html : "When an increase and then a rapid decrease in heat occurs, bacteria such as lactococci and lactobacilli can form. [...] Milk actually spoils when bacteria converts the lactose into glucose and galactose, which results in the production of lactic acid." Are these bacteria also present in sterilized milk? Are there other bacteria that will develop in sterilized milk when exposed to room temperature? –  konrad Jul 8 '13 at 12:44
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1 Answer 1

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Are these bacteria also present in sterilized milk?

If something is sterile, then by definition it does not have any live bacteria in it. That only applies while the milk is sealed in its original sterile container, though.

Can these bacteria be introduced from the air or from the bread [flour]?

Absolutely. There are bacteria and yeast living in the air, flour, and on every surface in your kitchen (including your bread maker). Wild yeast and bacteria in the air and flour are used to make traditional sourdough bread.

Are there other bacteria or toxins that will develop in sterilized milk when exposed to room temperature for a few hours?

I'm not sure how this differs from the above question, so: yes.


Speaking practically, if you are setting the timer for less than 4 hours, I think the risk of getting some sort of illness from this is rather low. The baking process will likely kill the bacteria before they have a chance to produce enough nasty toxins to make you sick. If you refrigerate the milk beforehand, you can even buy yourself a little extra time, since the milk would need to warm up slightly before bacteria could start reproducing in it. I still wouldn't make a habit of this, since there is still some risk of contamination. Leaving milk out on the counter just isn't a good idea, even if it was originally sterile.

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Random suggestions (add to your answer if you'd like): 1) If the recipe includes water (as well as milk), then switching part of that water to ice (same amount, by weight, and spread out at the bottom with the milk) will keep the milk cold much longer [don't use too much, or the dough will be too cold to rise]. 2) Powdered (dry) milk, placed on top of the flour –  derobert Jul 8 '13 at 16:24
    
Thanks for the answer and feedback! I will start using milk powder just to be safe. I suspect that using sterilized milk is safer then pasteurized milk due to the initial lack of bacteria, but with a lack of evidence on how much longer you can keep sterilized milk, it's better to be safe. If no one comes up with some great statistics on bacterial development in sterilized milk versus pasteurized milk in the next few days I will accept this answer. –  konrad Jul 9 '13 at 12:19
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