How is the length of time for food to spoil staying in an open environment comparable with the length of time food normally stays in the stomach?

This sounds like a topic for a paper or a study.

If you are asking for a comparison of the time it takes for exposed food to spoil with the time it takes for the stomach to empty the same, unspoiled food when consumed, there are just too many variables for a definitive answer.

For example, we don't know the food involved, the environment it is in, or how spoilage is defined. Pests could immediately descend upon the food making it inedible. Yeast could start fermentation which could be evident in a couple hours. In a few hours, pathogenic bacteria could reach levels to make someone sick but would not be obvious. A fresh whole piece of fruit could be unaffected for days.

Concerning the time food normally stays in the stomach, different foods will take different times to get through the stomach based on the difficulty of digestion and the quantity consumed. Normalcy would also need some basis of definition.