my roommate has this absurd (i think) idea that the left over exploded food on the inside of the microwave (exploded nacho cheese, soup ect.) will contaminate his cup of boiling water for his coffee, amongst the other things he heats up.
does this theory have any validity at all? i doubt it… bacteria can’t live amongst those waves right? and even if they could, how would they “jump” from the side of the microwave to the cup of water?
The Food Safety and Inspection Service say -
Microwave ovens can play an important role at mealtime, but special care must be taken when cooking or reheating meat, poultry, fish, and eggs to make sure they are prepared safely. Microwave ovens can cook unevenly and leave “cold spots,” where harmful bacteria can survive.
But if you’re too lazy to clean off the accumulated crud, just tell your roommate to put his cup in a plastic bag.
Yes, microwaves can kill bacteria. But, OTOH, your microwave ain’t no autoclave. There are cold spots, as mentioned, and, unless you zap the stuff long enough to kill every last bacteria present, the survivors can quickly reproduce back up to high levels when the zapping is over.
I wouldn’t say it’s a huge risk, but it’s not impossible. Of course, the larger danger is your roommate kicking your ass for being an inconsiderate slob. Oh, wait, I see you don’t say that you left the food in there. Well, pass that on to whoever did it.
ok, since the cold spots could leave bacteria, maybe my last question is the deciding factor: how would the bacteria critters “jump” from side of oven into roommate’s cup of water/bowl of soup?
the idea is absurd to me. unless there is physical contact, then no way this could happen, right? anyone know about airborne bacteria!?
by the way, i cleaned the oven last night for roommate… it hadn’t been cleaned in 3.5 years!!! i am fairly clean person, but refused to clean that oven for that long because no one could ever give me a good logical reason to. i just made sure no guests ever saw it. 
i am very interested in your answers, as i have been preaching my stance on this issue doggedly for some time now.
Many bacteria are airborne, or can easily be transported by small (dust-speck-sized) amounts of food. The bacteria do not have to survive microwaving, as the dried food can be recolonized by airborne bacteria in the kitchen. Many will survive anyway, as endospores are very hardy. Finally, bacterial aerosols are easily created by heating.
Yes, it’s a little less likely than sticking a dirty spoon directly in the coffee, but there’s still a significant risk of contamination. If microwaves were terribly effective at killing bacteria, don’t you think they’d be using them in hospitals?
wow, looks like i have been getting some additional “nutrition” with my microwaved meals for the past 3 years!
Dude! Bacteria CAN jump from a splotch into your pristine food! If there is a lump of gook on a surface in the microwave, it can pop when heated, carrying whatever is left alive along with it around the microwave.
I suggest one of those little Micro-Shields. Plastic things a little bigger than the average plate, about 4 inches high. A cutaway
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Something spatters and it hits the shield, not the microwave walls. There are small holes or slits to let water vapor escape through the shield, those aren’t entirely necessary, as there shan’t be a good seal.
You can wash these shields very easily.
yeah, they could explode if they were newer pieces of food, but they are mostly 3 year old crusts on there. those crusts don’t “pop”. but yeah, you are right.
I think bacteria could grow in a microwave. The last place I worked had mold in a mircowave that was used many times a day for years.