Recovery of phenolic compounds from the by-products of yellow mustard protein isolation

Nanofiltration (NF) (MWCO 150–300 Da) was evaluated for the recovery of phenolic compounds from the wastewater from the production of yellow mustard protein isolates. Rejection coefficients of 0.70 and 0.87 and transmembrane fluxes of 51.3 L/hm2 and 28.8 L/hm2 were observed under alkaline and acidic conditions, respectively. At low pH, 77% of the phenolic compounds fed to the process were recovered in the retentate. Combination of diafiltration (DF) with NF was beneficial only when processing at low pH. The permeate from the NF process a contained <100 ppm total phenolics, which suggests the possibility of recycling these effluents in the production of yellow mustard protein isolates. p-Hydroxybenzoic acid was the major phenolic compound found both in the waste effluent and in the products of NF processing. Sinapic acid constituted a secondary fraction, and derivatives of quercetin and kaempferol were also detected.