Bovine κ-casein glycomacropeptide (GMP) found in sweet whey is a 64 amino acid residue glycopeptide, which does not contain phenylalanine or other aromatic amino acids. There is, however, little information available concerning isolation of phenylalanine free GMP from sweet whey. In the study reported in this Research Communication, GMP was purified from three samples of sweet whey protein products (SWPP) by a procedure involving: (1) precipitation of protein by heat treatment; (2) precipitation of protein by pH shift to 4·6; and (3) diethylaminoethyl (DEAE)-Sephacel anion exchange chromatography of soluble portion of each sample obtained after removal of protein precipitates. The total protein precipitated with both heat treatment and pH shift accounted for average 61% of dry weight of SWPP. The GMP fraction obtained by DEAE-Sephacel chromatography accounted for average 7·5% of dry weight of SWPP. Amino acid analysis showed that there was no detectable level of phenylalanine in GMP fractions from all samples examined. The present method may help develop large scale methods of production of GMP.

The spontaneous fermentation of butter produces a highly fragrant product called smen. The short chain fatty acids (C4 to C10) have been traditionally considered the main aromas of this product but our work on the volatile fraction characterisation using SPME GC/MS showed that other products may also be important. Indeed, 183 different volatile compounds were detected belonging mainly to carboxylic acids, esters, ketones, nitrogen compounds and terpenes. However, only 19 compounds were common to more than 50% of the samples. These include short chain fatty acids (C4 to C10), their esters and short chain methylketones (C5 to C11). Despite their high levels in all samples, the amounts of C4 to C10 free fatty acids could not explain the differences in preparation and consumer appreciation of the samples. In contrast, the levels and nature of some methylketones and esters, particularly butanoic and hexanoic ethyl esters and 2-pentanone, seem to better reflect the effects of salt, thyme, acidity and consumer preferences.