How to get milk out of a futon mattress?

[attheendoftheday]

Yesterday dd1 emptied a cup of cow's milk on her futon bed. Dp didn't do a very good job of cleaning it up, and I only found out about it when I went to get dd1 up this morning. There is a crusty bit on the mattress and it smells!

What can I do to clean it? There must be a domestic goddess who can advise me.

I would use cold water, to not re-heat the milk and make it sour, then use Troubleshooter 1001 on the stain. It smells of citrus afterwards, but may not be colourfast.

Can you get the futon's cover off? Or is it through the wadding too?

Thank you! I'll give that a try. It has gone through to the wadding