Effect of annatto addition and bleaching treatments on ultrafiltration flux during production of 80% whey protein concentrate and 80% serum protein concentrate1

The goals of this study were to determine if adding annatto color to milk or applying a bleaching process to whey or microfiltration (MF) permeate influenced ultrafiltration (UF) flux, diafiltration (DF) flux, or membrane fouling during production of 80% whey protein concentrate (WPC80) or 80% serum protein concentrate (SPC80). Separated Cheddar cheese whey (18 vats using 900 kg of whole milk each) and MF permeate of skim milk (18 processing runs using 800 kg of skim milk each) were produced to make WPC80 and SPC80, respectively. The 6 treatments, replicated 3 times each, that constituted the 18 processing runs within either whey or MF permeate UF were as follows: (1) no annatto; (2) no annatto + benzoyl peroxide (BPO); (3) no annatto + hydrogen peroxide (H2O2); (4) annatto; (5) annatto + BPO; and (6) annatto + H2O2. Approximately 700 kg of whey or 530 kg of MF permeate from each treatment were heated to 50°C and processed in 2 stages (UF and DF) with the UF system in batch recirculation mode using a polyethersulfone spiral-wound UF membrane with a molecular weight cutoff of 10,000 Da. Addition of annatto color had no effect on UF or DF flux. The processes of bleaching whey or MF permeate with or without added color improved flux during processing. Bleaching with H2O2 usually produced higher flux than bleaching with BPO. Bleaching with BPO increased WPC80 flux to a greater extent than it did SPC80 flux. Though no differences in mean flux were observed for a common bleaching treatment between the WPC80 and SPC80 production processes during the UF stage, mean flux during WPC80 DF was higher than mean flux during SPC80 DF for each bleaching treatment. Water flux values before and after processing were used to calculate a fouling coefficient that demonstrated differences in fouling which were consistent with flux differences among treatments. In both processes, bleaching with H2O2 led to the largest reduction in fouling. No effect of annatto on fouling was observed. The reasons for flux enhancement associated with bleaching treatments are unclear.