Extraction of phenolic compounds from agro-industrial by-products by fungal fermentation with potential use as additives for meat and meat products. A review

The present manuscript reviews the findings of different research studies that evaluate the use of fungal solid-state (SSF) and submerged culture fermentation (SCF) with agro-industrial residues as substrates to enhance the production of polyphenols and their possible uses as food additives. Some agro-industrial residues (peels, pulps and seeds) are an important source of phenolic acids (p-coumaric, p-hydroxybenzoic, chlorogenic, cinnamic, ferulic, gallic, gentisic, protocatechuic, rosmarinic, salycilic, syringic, and vanillic acids) and flavonoid compounds (apigenin, chrysin, (+)-catechin, kaempferol, myricetin, quercetin, rutin, hesperetin, and naringin). In addition, the utilization of these residues as substrates in SCF and SSF enhances polyphenol production, improves biological function by increasing antioxidant and antimicrobial activities, and provides a potential alternative to synthetic antioxidant uses in the meat and meat products industry.

Rhizopus oligosporus and Lactobacillus plantarum Co-Fermentation as a Tool for Increasing the Antioxidant Potential of Grass Pea and Flaxseed Oil-Cake Tempe

Tempe-type fermentation originating from Indonesia can enhance the antioxidant activity of plant material. However, this biological potential depends on substrates and applied microorganisms. This study aimed to determine whether co-fermentation with Rhizopus oligosporus and Lactobacillus plantarum improved antioxidant activity of tempe obtained from grass pea seeds with flaxseed oil-cake addition (up to 30%). For this purpose, substances reacting with Folin–Ciocalteu reagent and free radicals scavenging potential were measured in water-soluble fractions and dialysates from simulated in vitro digestion. Additionally, the water-soluble phenolic profile was estimated. The higher level of water-extractable compounds with antioxidant activity was determined in co-fermentation products than in fungal fermentation products. Moreover, the fermentation process with the use of L. plantarum contributed to a greater accumulation of some phenolic acids (gallic acid, protocatechuic acid) in tempe without having a negative effect on the levels of other phenolic compounds determined in fungal fermented tempe. During in vitro digestion simulating the human digestive tract, more antioxidant compounds were released from products obtained after co-fermentation than fungal fermentation. An addition of 20% flaxseed oil-cake and the application of bacterial–fungal co-fermentation, can be considered as an alternative tool to enhance the antioxidant parameters of grass pea tempe.