Conclusion

It takes a week until fresh baked whole wheat bread, with no preservatives, starts to grow visible mold.
Breads with preservatives keep for two weeks after the expiry day without mold. The white bread had the most preservatives but molded before the sourdough bread.

The sourdough bread did not mold at all!

We are amazed, that there are so many different preservatives.
We have visted two bakeries and they said that they do not try to use preservatives and instead use less yeast an sugar. One baker told us that the greater the yeast and sugar content, the faster bread will mold.