As far as I am aware here are no legal standards for this as it's a quality not food safety issue:
These are the last figures I had when I worked in the bread industry:
Microbiological Testing Specification (start of life)
Target Unacceptable Frequency
Bacillus spp <10/g >100/g Survey
Yeasts & Moulds <100/g >1 x 103/g Survey
S.aureus <20/g >100/g Survey
However it does very much depend on your environment, formulation & declared product shelf life because, unless you have a controlled atmosphere (most bakeries don't) you might give yourself unnecessarily strict standards.
You could use micro testing to establish your standard but as bread is quite cheap & testing is quite expensive (and doesn't test the entire loaf) observation works best as a first pass.... so, take 100 packed loaves (or packs) from your line and retain half at room temperature ie. 20oC & half at 25oC (most customer's kitchens are warmer than 20oC so both incubation temperatures are required) and visually check daily, over 6 days for signs of mould development. Mould development will start to be visually apparent from day 3 & by day 5/6 you can tell how many (%) are going to be affected at each temperature. The exercise should be repeated at least 3 times (UK retailer standard).
In my experience although the standard is supposed to be "mould free" at end of life usually incidence is about 1% - especially in summer where there are more atmospheric spores & growth proceeds at a faster rate.