Effect of fermentation on total phenolic content and antioxidant activity of sourdough from Calabria (Italy)

It is well known that the use of sourdough leads to improve aroma, texture, and shelf-life of bread [1]. Other than these characteristics, consumers are conscious and pay attention to food health aspects. Efforts are being made to stabilize bakery products towards oxidation also using synthetic antioxidants [2]. It was reported the possible use of sourdough fermented wheat germ to reduce white bread oxidation [3]. The aim of the present work was to study the effect of fermentation in sourdoughs from Calabria (Italy) on phenolic content and antioxidant activity. Four sourdoughs were collected from bakeries located in two Calabrian Provinces: Catanzaro (PF1, PF2, and PF4) and Reggio Calabria (PF5) together with a dough for white bread used as control, were tested for lactic acid content by HPLC, total phenols by Folin-Ciocalteu, and antioxidant activity by DPPH method. For the microbiological analyses, each sourdough sample was homogenized, serially diluted, and plated in MRS and SDB for lactic acid bacteria (LAB) and in YPD for yeasts. The LAB load ranged from 6.50 to 8.90 Log CFU/g in MRS, and from 6.59 to 9.07 Log CFU/g in SDB. The load of yeasts detected ranged from 5.41 to 8.27 Log CFU/g. Compared to the control dough, the highest lactic acid content (4.892 mg/g) was found in PF1 while PF2 exhibited the lowest value (0.329 mg/g). The total phenolic content (expressed as mg of gallic acid/g of sourdough) ranged from 48.929 (PF2) to 92.089 (PF4) and in the control dough the content was 35.405. The highest antioxidant activity expressed as percentage of inhibition was found in PF5 (22.27%), whereas the minimum activity was found in PF2 (19.27%). The control dough exhibited a value of 17.77%. The microflora responsible for the sourdough fermentation determines an increase in the phenolic content and antioxidant activity; so, this is useful to naturally extend the bread shelf-life. LAB and yeasts technological analyses will be carried out to select the best strains to use as starter.