Why do onions turn pink...

[frizbee]

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

 

[phatch]

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.

 

[frizbee]

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

Thanks

 

[chefedb]

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.

 

[nicko]

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.

 

[chefedb]

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