Characterization of whey protein isolate obtained from milk microfiltration permeate

Abstract

Summary - Whey protein was concentrated from milk microfiltration permeate or Cheddar cheese whey using batch ultrafiltration and diafiltration. Permeate flux declined more rapidly for milk microfiltrate during concentration, but similar flux profiles were observed on both wheys during diafiltration. Protein contents in concentrates from milk microfiltrate and cheese wheys were respectively 95 and 74% on a dry matter basis, while their fat contents were respectively 0.2 and 15%. Protein solubility of the milk microfiltrate isolate was over 95% between pH 3 and 8, while protein solubility of cheese whey concentrate varied between 75 and 90% over the same pH range. J3-Lactoglobulin in cheese whey concentrate showed ex1ensive structural alteration as evidenced by the low proportion of SH groups in native position. J3-Lactoglobulin structural alteration was less severe in protein isolated from milk microfiltrate, but still significant. Milk microfiltrate protein isolate showed better gelling properties th an cheese whey protein concentrate. Cheese whey protein concentrate did not foam at ail, while stiff and stable foams were produced from milk microfiltrate protein isolate. Gelation and foaming were very sensitive to the ionic environment and were controlled by a balance between the pH and the calcium concentration. Reduction of calcium content in milk microfiltrate protein isolate, using saline solution during diafiltration, had only slight effects of protein functional properties.