Optimisation of the Measurement of the Antioxidant Activity of Probiotics and Pathogens: a Crucial Step Towards Evidence-Based Assessment of Health Claims and Production of Effective Functional Foods.

The consumer's attention is increasingly attracted by a multitude of health claims floated from the biggest food industries about probiotics. To date, the European Food Safety Authority (EFSA) has rejected all the applications for their health claims because they were not evidence based. It follows that more studies to characterise these microorganisms are needed, for instance regarding their antioxidant activity against reactive oxygen species involved in a number of illnesses and ageing. Questions as to whether the results have any bearing on effectiveness in the human body demand new methods able to estimate the antioxidant activity in a way that mimics the physiological defence against free radicals. In the following, (i) we report on the optimisation of a method complying with these requests and compare it to the classical Folin-Ciocalteu assay, (ii) we assert and explain its eligibility as regards probiotics on the basis of the mechanism of their antioxidant activity and (iii) we apply this method to highlight for the first time that probiotic bacteria and potential pathogens share the antioxidant capacity even if to a different extent. We provided food scientists with a tool to let them make educated guesses concerning the selection of effective ingredients for the production of functional foods.