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Manufacturing heat-stable whey protein isolate by clarification.

G. Subbiah Prabhakaran

Abstract:

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Manufacturing heat-stable whey protein isolate by clarification.
G. Subbiah Prabhakaran*1, J. A. Lucey1,2, M. Molitor2. 1University of Wisconsin, Madison Madison, WI, 2Wisconsin Centre for Dairy Research Madison, WI.

Residual fat (RF) in whey protein isolate (WPI) is detrimental for storage flavor and functional applications. Objective of this study was to remove RF without utilizing microfiltration. We believe that by demineralizing whey via ultrafiltration (UF), phospholipoprotein (PLP) fractions can be precipitated along with denatured proteins and removed by centrifugation. Ca is also removed which improves heat stability. By removing RF and hence reducing oxidation of PLPs, we expect the resultant WPI to have a longer shelf life. Demineralization was achieved by acidifying liquid WPC-34 to pH 4.5 using HCl and ultrafiltering it along with extensive diafiltration. Benchtop trials (n = 4, P < 0.05) studied effects of pH (4.1, 4.3, 4.5, 4.7, 4.9, 5.2), protein concentration (1, 2, 3, 5, 7, 9% wb) and conductivity (300, 500, 750, 1000, 1500 mS/cm2) of demineralized UF retentate (UF-r) on precipitation of RF. The UF-r was adjusted to various combinations of pH, protein concentrations (PC) and conductivities and centrifuged on a bench scale at 7500 � g for 10 min. Sedimentation of RF was estimated by measuring turbidity of supernatants. RF precipitation was highest at PC ≤3% because of reduced viscosity. At pH 4.5—4.7, precipitation was maximum showing that denatured protein and PLPs coagulate at pH values close to isoelectric point of denatured proteins. Reducing conductivity, increased precipitation of RF indicating that more coagulation occurs with reduced charge screening. SDS-PAGE analysis indicated there was sedimentation of PLPs, caseins and denatured proteins while native whey proteins remained soluble. Thus, isoelectric precipitation was effective in removing RF from sweet whey. Results were used to scale up the process. 200 gal of sweet whey was demineralized and clarified using a pilot-scale desludging clarifier and spray dried to produce WPI powder (91% protein, 2.6% fat db). Test for heat stability showed that 98% protein remained soluble when a 5% protein solution was heated treated at 80�C for 30 min. Future work will compare functional, flavor and storage properties of this WPI with some commercially available WPIs.

Keywords: whey protein isolate, isoelectric precipitation, clarification.

Biography: Graduate Research Assistant at the University of Wisconsin, Madison doing a Master's in Food Science.