What each one does
A conventional preservative creates a chemical hurdle that works regardless of conditions. A bioprotective culture creates a biological one by occupying the product, which requires it to be alive and active, and therefore requires the right temperature and pH.
What decides it
Where shelf life is actually ending, and under what conditions the product is stored. If the product goes off because fat oxidised, no preservative of either kind will help and the answer is an antioxidant.
Where the obvious answer is wrong
The obvious answer to a clean label brief is to swap the preservative for a culture at the same point in the process. The culture usually needs to be added earlier and to have time at a temperature where it can establish, which can mean changing the process rather than the formulation.
