Pros
As long as meat is properly refrigerated while it is marinating, I would not make a separate batch of marinade to serve as the sauce. At refrigerator temperatures, it takes 12 hours for one bacteria to become two bacteria. There is little chance that enough toxins could be produced in that time frame to make someone sick.
And if the marinade is high in acidic ingredients, as most are, bacterial growth will be suppressed due to a low pH. Combine that environment with low temperatures and your marinating meats will be safe.
Cons
Another point is that if the marinade contains those toxins, they are already on the meat you are cooking and the heat will not disable them. If you are that concerned about toxins that bacteria produce, your best choice may be to avoid eating meat, period.
It's simply not possible to ensure that 100% of our food will be 100% safe 100% of the time. If you become very concerned about food poisoning, even if you handle food as safely and correctly as possible, you run the chance of not enjoying nourishment.
Where It Stands
Always, always marinate meat in the refrigerator. If you want to be very safe, even if marinating for 20-30 minutes, put the meat in the fridge. And make sure that the raw meat and marinade do not come into contact with any food that will be eaten raw, like fruits and vegetables.
And remember to boil the reserved marinade for 2-3 minutes before serving. Bring the marinade to a rolling boil that cannot be stirred down. And use a fresh spoon to serve the hot marinade. If you want to be very safe, simmer the marinade for 15 minutes.
If, however, you have a person in the high-risk group in your household (children, elderly, pregnant women, those with chronic diseases), you may want to take that extra precaution and make a separate batch of marinade. Be sure to boil the marinade to bring it to a desirable serving temperature.
Given the concerns about food safety and the lack of proper inspections of food in this country, if you are in a high-risk group you may want to think about avoiding meat and dairy products altogether. A vegetarian diet can be safer, although fruits and vegetables can also be contaminated with bacteria through improper handling.
We really have to start from the point that all foods can cause a food-borne illness. Most people have developed an immunity to low levels of bacteria and will not become sick as long as the food only has a small amount of the bacteria.
The best course of action is to follow food safety standards, be scrupulous about keeping your kitchen clean, and make decisions about food consumption that you are comfortable with.
Now that you're informed, you can make the decision that is best for you and your family.
