Beer Battered Onion Rings -- what makes them look shiny?
The shininess is from oil that has seeped into your food. According to About.com, the temperature at which oil starts to seep into food is around 163˚C (325˚F). You need to keep the temperature above that to prevent it getting shiny. Remember to use an oil with a high smoking point so you don't replace the shine with a carcinogen.