Food safety and pre-prepping food

Factual Questions
1

How to consider the amount of time food spends waiting to be cooked in relation to how long it’s safe to eat after cooking and refrigeration. Some recipes recommend preparing some parts of dishes or full dishes in advance, and cooking them when you’re ready. For example, some I’ve seen some say lasagna gets better if you keep it 24-48 hours in the fridge after assembly and before cooking.

Say there’s two scenarios:

  1. I prep a lasagna, keep it 48 hours in the fridge, cook it, refrigerate as soon as possible
  2. I prep a lasagna, cook it immediately, refrigerate as soon as possible

If lasagna number 2 is good to eat for 4-5 days, is number 1 also safe to eat for 4-5 days after cooking? My gut feeling is that there is some microbial growth before the cooking, but it should be eliminated by the cooking process, and then restart again afterwards from near zero. Since the growth is exponential, 2 days pre +2 days post cooking is probably not as bad as 4 days post cooking, but it probably has some effect. Any bacterial growth in the first 48 hours before cooking would still contribute to waste products from the bacteria.

2

Your concern is exactly why you’re advised to keep your prepped-but-not-cooked lasagna in the fridge prior to cooking. It retards bacterial growth spoilage.

Post-cooking any bacteria that survived the fridge should be dead and harmless. The clock starts ticking again once it cools down, just as it does for the lasagna that wasn’t parked in the fridge for a day or two.

The only problem that might arise is that while the bacteria might be dead certain waste products from them are still around. If they’re toxic you could have a problem. But, again, that’s the reason for chilling things down, to prevent bacterial growth (and pooping) that could present health risks. The risks from a day or two in the fridge, assuming the ingredients weren’t sitting in the fridge for too long before you made the lasagna, would be minuscule.