Neutral volatile compounds in the raw milks from different species

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Abstract
A comparative study was carried out on the flavour constituents of bovine, ovine, caprine and water buffalo fresh raw milks. The volatiles were isolated from milks by means of vacuum distillation and liquid–liquid extraction. Eighty neutral volatile compounds were identified using high resolution gas chromatography (HRGC) and HRGC-mass spectrometry. About 30 of these components have not been detected previously in milk. The volatiles in milk were similar for the four species, although several quantitative differences might explain the different odours. The volatiles consisted mainly of ethyl esters, especially those derived from butyric and hexanoic acids. Dimethylsulphone alone comprised ~ 25% of the volatile components in bovine, caprine and ovine milk, but only 4% in buffalo milk. Among the aldehydes, pentanal and nonanal were the most representative. Other aldehydes were present selectively: 3-methylbutanal was found only in buffalo milk; phenylacetaldehyde and benzaldehyde were present in large quantities in caprine milk, and in trace amounts in the other milks. The content of ketones, mainly 2-methylketones, was higher in buffalo milk than in the other three types. Alcohols varied between species, from 1·5% (bovine) to 5% (buffalo). Among these, 1-octen-3-ol and phenylethanol could be particularly important for the aroma of milk. The level of l-octen-3-ol in the milks was: buffalo > ewe > goat ≫ cow. Phenylethanol was not found in ewes' and goats' milk and its concentration in buffalo milk was 100 times higher than in bovine milk. Finally, indole and 4-methylphenol, interesting because of their odorant properties, were present in higher quantities in buffalo, ewes' and goats' milks than in cows' milk.