Improving phenolic compounds production and radical scavenging activity of barberry extract using solid state fermentation

Barberry fruits pre-extraction fermentation with the fungus Rhizopus oligosporous for 10 days led to a 4-fold increase in the extracted amount of phenolic compounds. Fermentation also increased the free radical scavenging activity of the extract and partially compensated monomeric anthocyanins loss due to heat sterilization. The extract obtained from fermented barberry had higher pH value and acidity in comparison with that from non-fermented counterpart. The pH increment was ascribed to organic acids decomposition due to heat sterilization and the departure of the resulting volatiles, as well as, to fermentation-born amino compounds and Rhizopus-released extracellular enzymes. The higher acidity of the extract from fermented barberry was not nevertheless associated with heat sterilization and was attributed only to phenolic acids production by R. oligosporous. Moreover, although heat sterilization of barberry had no major effect on reducing sugars content of the extract, but fermentation significantly decreased it. Extract color was effected by both heat sterilization and fermentation processes. Although the lightness parameter (L*) of the extract increased due to sterilization, thereby resulting in a decreased sensory color score, fermentation decreased the parameter to some extent, along with somewhat increased values for the parameters a* (redness) and b* (yellowness). Finally, all sensory parameters, except color, received higher scores for the extract from fermented barberry in comparison with that from the non-fermented sample.