Bitterness in processed cheese caused by an overdose of a specific emulsifying agent?

Abstract

In Austria, a big manufacturer of processed cheese was faced with a mysterious problem of bitterness and a texture defect in processed cheese slices occurring in distinct batches every once in a while and unexpectedly. To clear up this phenomenon, reference samples of good quality as well as problem cheeses were analysed for chemical composition. Proteolytic changes were studied by urea-polyacrylamide gel electrophoresis (PAGE), SDS-PAGE and isoelectric focusing of caseins as well as of soluble nitrogen fractions. Peptides of the water-soluble nitrogen fractions were analysed by reversed phase-high performance liquid chromatography (RP-HPLC). Surprisingly, bitter cheese samples showed very weak or even no bands in the α s1 - and β -casein region, but only γ -caseins and mainly low molecular weight peptides, which was also confirmed by Kjeldahl analysis. In comparison with the respective reference samples, RP-HPLC profiles of bitter cheese samples showed extremely high concentrations of hydrophilic and hydrophobic peptides. Since significantly higher concentrations of ash and phosphorus were detected in bitter cheese samples, it was noticed that the respective batches of processed cheese slices had been produced apparently using an overdose of a specific emulsifying agent (of high phosphorus content).