Hygiene-wise, need to clean grill/broiling tray after each use?

For the grate in an outdoor grill, I think you can feel safe not cleaning it, but only under the following condition: Before each use, you heat the grill to a temperature in excess of 250 degrees (F) for at least 15 minutes. Gotta heat it up to make sure you kill everything that might have got onto it since you last used it.

Since you really ought to heat the grate up pretty seriously before trying to cook on it anyway, this is almost a no-effort thing.

In terms of extending the life of your grate, it's good to give it a good burn-off AFTER cooking if you're not going to clean it outright. Burning off will make sure there aren't any wet or corrosive things still left on the grate.

As to the broiler pan, I would never let that one go unwashed. Unlike a grill grate, you don't preheat it, so you don't have a chance to kill the beasties that might have grown up in whatever you left on it from last time. If you cooked a steak yesterday and didn't wash the pan, the grease and juices have had 24 hours to attract and breed bacteria and whatever by the time you use it today. Then you pull it out, plop another steak right on your bacteria colony, and broil. What's exposed to the heat directly may get hot enough to kill germs, but what's directly under your steak almost definitely will NOT.

Will you get sick if you don't clean your stuff? Maybe not--it's your life. But please, please, please, don't be so casual about cleaning if you're cooking for ANYBODY else. And really, cleaning a broiler pan isn't that hard. You can man up and just do it.

One thing nobody seems to have mentioned is that it's not necessarily the bacteria themselves that are harmful.

Yes, any stray bacteria will almost certainly be killed each time you cook, but bacteria produce protein toxins as they grow, and these toxins are extremely dangerous, even lethal at relatively low doses.

In fact, the only reason bacterial poisoning (i.e. salmonella or e.coli) is a concern in the first place is because the bacteria can produce those same toxins while in your stomach and digestive tract. But at least when you've ingested the bacteria themselves, your immune system has a chance to react and try to get rid of it before the level of toxicity reaches lethal levels; if you ingest the toxins themselves, your body may not have the same opportunity.

Protein and LPS toxins, unlike the bacteria themselves, cannot be killed with direct heat because there is simply nothing to kill. They can be destroyed, certainly, but it takes a lot more heat to do so than it takes to cook the food - you'd basically have to incinerate it.

The good thing is that generally these toxins are water-soluble and are easily removed with sufficient soap and hot water. Running something through a dishwasher cycle is basically guaranteed to kill the bacteria and wash off any toxins.

But if you leave a pan or grill sitting around with a bacterial colony growing on it for a week, then the bacteria are no longer your primary concern; the toxins they've left behind are. Plop a piece of meat on top of it and those water-soluble toxins will get baked on or absorbed just like salt. Cooking the meat will have done absolutely nothing to get rid of them.

Do yourself a favour and wash your grills and cookware, so you can avoid serious health complications or costly lawsuits. You can burn off grills as bikeboy mentions, but don't just leave them sitting around potentially contaminated.

Purely from a standpoint of food safety, I'd say it's not necessary to clean a grill grate or broiler pan after each use. You're right that direct-heat grilling and broiling are high-heat cooking methods. If you're cooking a steak, for example, by the time you get the grill up to temp and cook the meat to a safe internal temperature any charred bits of whatever was left over from the last grilling session should be burned well beyond the point of being biologically inert. One could maybe make the case that broiling might be slightly less safe since the food is between the heat source and the pan, but I'm thinking you're still pretty safe.

But, you're probably going to contaminate the food flavor-wise by cooking it on the dregs of the last thing you cooked. The flavor of something that has been burned to charcoal is bitter and unpleasant. If your food picks that up it definitely won't improve the flavor of the meal.

I don't clean my grill after each use. Instead after I've gotten it up to temperature, I run a grill brush over the hot grate. Anything left over from the last grill session falls off easily at that point, and it takes maybe 15 seconds.

Regarding the broiler pan, I'd personally clean that after every use, but I don't store mine in the oven anyway (had one too many experiences of accidentally pre-heating an oven with a broiler pan in it to not take care of it immediately). It should be as simple as dumping any accumulated grease in the trash and giving it a quick soak with some Dawn and hot water.