Phenolic compounds, flavonoids, lipids and antioxidant potential of apricot (Prunus armeniaca L.) pomace fermented by two filamentous fungal strains in solid state system

Background: The use of agricultural and food by-products is an economical solution to industrial biotechnology. The apricot press residues are abounding by-products from juice industry which can be used as substrates in solid state fermentation process (SSF), thus allowing a liberation and increase of content from various biomolecules with high added value. Methods: The evolutions of phenolic levels (by colorimetric assays and high performance liquid chromatography, HPLC-MS) and antioxidant activities (by DPPH assay) during SSF of apricot pomaces with Aspergillus niger and Rhizopus oligosporus were investigated. The changes in fatty acid compositions of oils in apricot kernels during SSFs were also analyzed by gas chromatography (GC-MS). Results: The results showed that the levels of total phenolics increased by over 70% for SSF with R. oligosporus and by more than 30% for SSF with A. niger. A similar trend was observed in the amounts of total flavonoids (increases of 38, and 12% were recorded for SSF by R. oligosporus and A. niger, respectively). Free radical scavenging capacities of methanolic extracts were also significantly enhanced. The main phenolic compounds identified through HPLC-MS in fermented apricot press residues were chlorogenic acid, neochlorogenic acid, rutin, and quercetin 3-acetyl-glucoside. This work also demonstrated that the SSF with filamentous fungal strains not only helped in higher lipid recovery from apricot kernels, but also resulted in oils with better quality attributes (high linoleic acid content). Conclusion: The utilization of apricot by-products resulting from the juice industry as waste could provide an extra income and at the same time can help in solving solid waste management problems