How likely is hiv infection from giving oral sex without climax to a unknown male while having food burn on top of mouth.

Not much: Any disruption of the normal integrity of the skin or mucous membranes (like in the mouth) can provide an entry for the virus. The virus can be transmitted in the semen. Even without climax, there can be small amounts of secretions that can leak out. But how likely will you get it?Can't say for sure but it's probably a low risk. Best to know the HIV status of your partner. Have him checked for HIV