I'm making a meringue and I just realized I don't have tartar or lemon juice, but I do have oranges? And I read that you can use anything acidic but I dont know. So I would like to know if it's ok to substitute lemon juice with orange juice?
Only heat can pasteurize egg white. You might be thinking about stabilizing egg white, to help prevent over beating. In this case, cream of tartar is recommended. If that is unavailable, lemon juice or white vinegar can be substituted. I don't think orange juice would be helpful. You could always just leave these additions out, and be careful not to over whip.