This paper examines the distribution of mono- and sesquiterpene secondary metabolites in 47 plants present in grazing areas from which cheeses are produced. In total, 54 terpenoid volatiles, derived from both highland and lowland plants, were obtained by a gaseous purge-and-trap system without the use of organic solvents and then identified by automated GC/MSD-FID analysis using mass spectral libraries, retention indices, and data acquired by the authors with authentic substances. Single ion monitoring proved valuable in identifying overlapping compounds with similar spectra for the subsequent semiquantitative determination of compositions. These are displayed as radar plots. It is suggested that flavor/aroma differences in cheeses produced from animals grazing in different areas and seasons arise from species (n = 38), phenological stages (n = 8), locations (n = 4), and seasonal variation in terpenoids present (the most common were trans-β-ocimene, limonene, and trans-β-caryophyllene). This hypothesis is supported by the fact that distinct variations in terpenoids with differing odor descriptors and abundances were found. It is also possible that terpenes with a higher polarity are less efficiently recovered by the purge-and-trap method than compounds of lower polarity. As the radar plots display relative concentrations based on detection limits, the relative efficiency of detection for different classes of compounds needs to be taken into consideration. Keywords: GC/MS; flavor; volatile; monoterpene; sesquiterpene; plant; highland; lowland; pasture; retention index

S. Hispa! nico cheese, a semi-hard Spanish variety, was manufactured from a mixture of pasteurized cows' and ewes' milks (4 : 1) using a commercial mesophilic LD-type starter comprising Lactococcus lactis subsp. cremoris, Lc. lactis subsp. lactis, Lc. lactis subsp. lactis var diacetylactis and Leuconostoc mesenteroides subsp. cremoris. Varying amounts (0-1n0 g\kg) of an Enterococcus faecalis INIA 4 culture in milk were added as a bacteriocin-producing adjunct. Differences in pH between cheeses manufactured with and without the bacteriocin producer did not exceed 0n11 pH units. Starter lactococci lost viability more rapidly in cheeses made with the bacteriocin producer, which reached counts of up to 6i10( cfu\g during ripening. Aminopeptidase activity in 1-d-old cheese made from milk inoculated with 1n0 g bacteriocin-producing culture\kg was twice that in control cheese. Degrees of overall proteolysis and levels of total free amino acids in 45-d-old cheese made with 1n0 g bacteriocin-producing culture\kg were 1n80-fold and 2n17-fold those in control cheese of the same age. Inoculating milk with 1n0 g\kg bacteriocin-producing culture reduced the level of hydrophobic peptides in the resultant cheese, increased the concentrations of 3-methyl-1-butanal, diacetyl and acetoin, and resulted in the highest scores for flavour quality and flavour intensity throughout ripening.

The present article reviews the most commonly used methods, techniques and equipments for instrumental analysis of volatile (flavour) compounds in milk and dairy products. After listing sorne previous important review articles, several methods commonly used for samp1e treatment are described, as weil as the following techniques for extraction and concentration prior to gas chromatographic (GC) analysis: static and dynamic headspace, steam distillation, high-vacuum distillation, molecular distillation, direct extraction (liquidlliquid or liquidlsolid), supercritical fluid extraction (SFE), simultaneous (steam) distillation extraction (SDE), dialysis, solid-phase extraction (SPE) and solid-phase microextraction (SPME). Two c1assical injection deviees are also described: oncolumn injection and the so-called 'purge and trap' system. The main advantages and disadvantages of CUITent commercially available types of fused silica capillary columns are briefly considered. The newly developed 'chiral' phases are also described. The article reviews sorne of the numerous detection systems used for qualitative and/or quantitative analyses such as FID or MS detection, FTIR detection, SCD, FPD and NPD detectors used for sulfur-and nitrogen-containing components, AED detection and the 'sniffing deviee'. Sorne usefullibrary search systems such as PBM, INCaS ™ and SISCaM (ie, MassLib®) are mentioned to complete the overview of this topic. Finally, this paper briefly points out sorne other methods (ie, photometrie), capable of determining various specifie chemical functions responsible for flavour (carbonyl compounds, etc), as weil as promising techniques involving new electronic noses. milk / dairy product / volatile compound / flavour / analytical method Résumé-L'analyse instrumentale des composés volatils (de l'arôme) du lait et des produits laitiers, Le présent article passe en revue les méthodes, techniques et équipements les plus utilisés Oral communication at the lDF Symposium 'Ripening and Quality of Cheeses',

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A dynamic headspace technique (purge and trap) coupled to gas chromatography-mass spectrometry was used for the study of the volatile fraction of pasteurized ewe's milk cheese. The effect of the addition of the cysteine proteinase of Micrococcus sp. INIA 528 to milk on the formation of volatile aroma compounds in cheese was also evaluated. Forty-five compounds, in total, were identified, including hydrocarbons, alcohols, ketones, aldehydes, esters, terpenes and sulfur compounds. The abundance of most volatile compounds increased significantly (P < 0.05) with ripening time, except those of ethanol and 2,3-butanedione which decreased. Acetaldehyde and some minor components did not vary remarkably during ripening. Acetaldehyde, 2-methyl-I-butanal, 3-methyl-I-butanal, 2-propanol, 2-pentanone and 3-methyl-3-buten-1-ol were the only compounds affected by the addition of cysteine proteinase. The more extensive proteolysis in cheese with cysteine proteinase might have enhanced the formation of volatile compounds derived from amino acids, such as acetaldehyde, 2-methyl-1-butanal and 3-methyl-I-butanal, formed from threonine, isoleucine and leucine breakdown, respectively.