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.