Impact of the order of acid and heat treatments on the composition of caseinomacropeptide isolate

Effect of the order of acidification and heat treatment on recovery, purity and stability of caseinomacropeptide (CMP) from sweet whey was investigated. In acid-heat treatment, sweet whey was first acidified to pH values in the range of 3–5 and then heat treated at 90 °C for 1 h. In heat-acid treatment, applying the same treatment parameters, sweet whey was first heated and then acidified. Supernatants from both treatments were separated by centrifugation and analysed as CMP isolates. Reducing the pH of sweet whey from 5 to 3 resulted in a loss of CMP and retention of most of whey proteins in the isolates obtained by both treatments. Recovery and purity of CMP were highest at pH 5 for both treatments and at pH 4.5 for heat-acid treatment. Heat-acid treatment at pH 5 preserved more of bound sialic acid compared with other treatment combinations; this treatment is recommended for isolation of CMP.