The aroma composition of swiss gruyère cheese iv. The acidic volatile components and their changes in content during ripening

Abstract

Part IV first reports a list of acidic volatile components isolated and identified by GC-MSD in a pool of five mature, first class Swiss Gruyère cheeses. The analysis of the outer zone (including the smear-coated rind), the middle and central zones revealed concentration gradients for some of the volatile components. The compounds found were principally fatty acids such as ethanoic, butanoic, propanoic, hexanoic, 2-methylbutanoic, 2-methylpropanoic, 3-methylbutanoic, pentanoic, octanoic and decanoic acids ranked by decreasing concentration, and hydroxybenzene (phenol). Changes in the content of these acidic volatile substances were then studied in two zones of eight first class Swiss Gruyère cheese over a 12-month ripening period. Quantitative determination of main constituents were performed separately by GC-TCD for the eight loaves. Semi-quantitative analyses of minor compounds were carried out by GC-MSD or GC-FID only in a pooled sample. The content of 2-methylpropanoic, 2-methylbutanoic, 3-methylbutanoic, 4-methylpropanoic, hexanoic (particularly in the inner zone), octanoic, and decanoic acids as well as hydroxybenzene increased in an approximately exponential way during the ripening period. On the other hand, concentrations of total volatile fatty acids, ethanoic, propanoic, butanoic, pentanoic and hexanoic (particularly in the outer zone) showed a more linear increase. Some possible metabolic pathways for the formation of these cheese flavour components are reviewed. © 1993 Academic Press.