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Why do onions turn pink...

Discussion in 'Professional Chefs' started by frizbee, Nov 18, 2010.

  1. Nov 18, 2010 #1
    frizbee

    frizbee

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    Hey  Ya'll it's been a while...

    Missed ya.

    Question...What is the science behind why onions turn red when they are being baked? I understand carmelization so what prevents the onion from compeletely carmelizing when in the oven?

    Thanks in advance as always...

    Frizbee
     
  2. Nov 18, 2010 #2
    phatch

    phatch Moderator Staff Member

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    Which onions?  

    Red onions are full of pH sensitive cyoanthins. They turn pinker when exposed to bases and purple-blue when exposed to acids. Or maybe it's the other way around, but they do change color according to pH.

    I've not noticed the yellow onions I normally use turning pink when they get baked.
     
  3. Nov 24, 2010 #3
    frizbee

    frizbee

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    Specifically I was asking about yellow onions.. Yes, why do they turn pink when baked and how do you stop this?

    Thanks
     
  4. Nov 24, 2010 #4
    chefedb

    chefedb

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    They are simply put, Bleeding. When subject to a high dry temp they are on the road to the sugar content caramelizing. This lite caramelzation will appear pink in particular on thick skin sweet onion. It will not hurt the product but will give a weird color.
     
  5. Nov 24, 2010 #5
    nicko

    nicko Founder of Cheftalk.com Staff Member

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    Doesn't it also have something to do with the pan they are being baked in? I believe this will happen when baking them in an aluminum pan but I could be wrong on that. Great question and glad your back at ChefTalk.
     
  6. Nov 24, 2010 #6
    chefedb

    chefedb

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    Nicko ! I have seen it in a black roasting pan and on a aluminum sheet pan and a ss bain marie insert.