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Les ruminants, comme tous les mammifères, hébergent des billions de microbes symbiotiques, constituant les « microbiotes » de la peau, des voies digestives, respiratoires et génitales etc. La composition et les fonctions de ces microbiotes dépendent, entre autres, de leur habitat. L’utilisation des approches « -omiques », en particulier le séquençage de nouvelle génération, a permis de caractériser les organismes composant les microbiotes, leurs gènes et leurs activités. Les ruminants se distinguent par la présence dans leur rumen d'un microbiote spécialisé, composé principalement de bactéries, de protozoaires, d’archées et de champignons. Situé en amont des sites d'absorption, il joue un rôle central dans la nutrition des ruminants. La production des ruminants est particulièrement influencée par le microbiote intestinal (dont la population est diversifiée et spécifique du segment considéré) et le microbiote associé à la peau de la mamelle (réservoir important de la diversité microbienne du lait cru). Ces différents microbes interagissent entre eux et avec leur hôte sous l'influence de divers facteurs de variation, dont le principal est le régime alimentaire, mais aussi le milieu de vie et les pratiques d'élevage au début et milieu de la vie de l'animal. Des études récentes montrent un contrôle génétique potentiel par l'hôte de ses communautés microbiennes. En outre, il existe une accumulation de preuves des liens entre les microbiotes et la santé animale, l'efficacité de l'alimentation, les performances, la qualité des produits et la production de gaz à effet de serre. Ces constatations justifient l'intérêt croissant des éleveurs pour les microbiotes des animaux et leur modulation.

The objective of this work was to determine whether the effects of farming systems on the cheese sensory properties are reduced when the milk used to make cheese is pasteurised. The milk of cows reared under two grazing systems (extensive and semi-extensive) was processed into raw and pasteurised milk cheeses. These grazing systems were mainly differentiable by the milk fatty acid (FA) composition and, to a lesser extent, by their levels of lactic acid bacteria, which were higher in milk from the extensive grazing system. In cheese, the different FA composition persisted and affected the texture of the cheese regardless of the milk treatment. The effects of each grazing system were indistinguishable in several cheese characteristics (proteolysis, texture, and aroma) after pasteurisation. In contrast, among pasteurised milk cheeses, those resulting from an extensive system had greyer rinds, while no difference in rind colour was observed among raw milk cheeses.

In Press; The milking of Salers cows requires the presence of the calf. The removal of the calf would simplify the milking routine, but it could also modify the milk yield and the milk and cheese composition. Therefore, the aim of this experiment was to evaluate the effect of calf presence during milking during sampling period (winter or grazing periods), on dairy performance, milk fatty acid (FA) composition, lipolysis and cheese yield and composition. Nine and 8 Salers lactating cows were milked in the presence (CP) or absence (CA) of their calves respectively. During winter, the cows were fed a hay-based diet and then they only grazed a grassland pasture. Calf presence during milking increased milk yield and milk 16:0 concentration and decreased milk fat content and milk total odd- and branched-chain FA (OBCFA) concentrations. Calf presence only increased initial lipolysis in milk collected during the winter season. Milk from CP cows compared to CA cows resulted in a lower cheese yield and ripened cheeses with lower fat content. Milk from the grazing season had lower saturated medium-chain FA and OBCFA concentrations and higher 18:0, cis-9-18:1, trans-11-18:1 and cis-9, trans-11-CLA concentrations than that from the winter season. Initial milk lipolysis was higher in the winter than in the grazing season. These variations could be due to seasonal changes in the basal diet. Furthermore, the effect of calf presence during milking on milk fat composition was lower than that on dairy performance, cheese yield and composition. Removing the calf during the milking of Salers cows seems feasible without a decrease in milked milk, and with a positive effect on cheese yield and fat content, under the condition that we are able to select cows having the capacity to be milked easily without the calf.

International audience; Milk fatty acid (FA) profiles and sensory properties of Cantal cheese from three equivalent groups of 12 Montbeliarde cows kept indoors and fed hay and concentrates (I), grazing on upland pasture with a diversified flora under continuous mode (C), or grazing on upland re-naturalized temporary grassland under rotational mode (R) were compared. C milk was richer in total cis-C18: 1 isomers, odd-andbranched- chain, mono-unsaturated, n-3 and n-6 FAs, while R milk was richer in total trans-C18: 1 isomers, rumenic acid and poly-unsaturated FAs. Differences in FA profiles between R and C milks could be explained by differences in grass quality. Cheeses were made on three consecutive days. Panellists were unable to distinguish R and C cheeses at 12-week ripening; differences became perceptible after 24 weeks. The 24-week ripened C cheese gave more intense odour, more intense and persistent aroma, and sourer, more pungent and saltier taste than the corresponding R cheese.

International audience; Linseed supplementation of dairy cows' diet increases unsaturated fatty acid (FA) concentrations, which could lead to oxidised off-flavours in dairy products if antioxidant content is low. The FA profiles and sensory properties of milk and uncooked pressed cheese (Saint-Nectaire type) from four groups of six cows receiving a corn silage-based diet with no additional lipid (control), or supplemented with extruded linseeds (5% of additional fat-in-dry matter intake; EL), EL and vitamin E (7500 IU per cow per day of DL-alpha-tocopherol; ELE), or ELE and plant extracts rich in carotenoids and polyphenols (1% of dry matter intake) were compared. Feeding EL decreased milk and cheese 4- to 16-carbon saturated FA, and increased 18:1 cis-9, 18:3n-3 and total trans FA concentrations. Extruded linseeds did not induce oxidised off-flavours but led to a less firm and more meltable texture in cheese. Vitamin E supplementation increased a-tocopherol concentration, but did not affect sensory properties.

L'objectif de cette etude correlationnelle etait de : (1) caracteriser la composition de fromages fermiers au lait de vache en termes de teneurs moyennes et de variabilite en acides gras, retinol, α-tocopherol, folate, β-carotene, xanthophylles, calcium, phosphore, magnesium, potassium, zinc, chlorure de sodium et potentiel antioxydant total (TAC), et (2) identifier les caracteristiques du troupeau et les pratiques alimentaires associees a des differences de composition du fromage. Trois cent six fromages fermiers a pâte pressee, produits en conditions reelles tout au long de l'annee, ont ete preleves. Les conditions de production du lait ont ete prealablement identifiees au moyen d'enquetes. Le fromage fermier se caracterise par une grande variabilite de composition. La nature de la ration fourragere (pâturage vs. fourrages conserves, en particulier) explique une grande partie de la variabilite en composes liposolubles du fromage. La matiere grasse du fromage est plus riche en C4:0, C18:0, C18:1 cis-9, C18:1 trans-11, C18:2 cis-9, trans-11 (CLA), β-carotene, xanthophylles, retinol, α-tocopherol et TAC et plus pauvre en C10:0, C14:0 et C16:0 avec les rations a base de pâturage comparees aux rations a base de fourrages conserves. En periode de pâturage, elle est la plus pauvre en C6:0 a C14:0, en β-carotene et en retinol et la plus riche en C18:1 cis-9, C18:2 n-6 et C18:3 n-3 avec un pâturage en alpage. Elle est plus riche en C18:1 trans-11, CLA, β-carotene et xanthophylles et plus pauvre en C16:0 avec un pâturage de premiere utilisation compare a un pâturage d'utilisation de rang superieur. Un pourcentage plus important de concentre est associe a des niveaux plus importants en C14:0 et C16:0 et plus faibles en C18:1 trans-11, CLA, C18:2 n-6, C18:3 n-3, xanthophylles et retinol. En hiver, la matiere grasse du fromage est la plus pauvre en C18:1 trans-11, CLA, C18:3 n-3 et β-carotene avec les rations a base de mais, tandis que la supplementation en vitamines A et E est associee a des niveaux plus importants de retinol et d'a-tocopherol, respectivement. Les caracteristiques du troupeau ont peu d'incidence sur la composition du fromage excepte la race. En particulier, les races Abondance et Montbeliarde sont associees a un pourcentage en CLA plus eleve dans le fromage que la race Holstein, alors que la teneur en carotenoides du fromage est la plus elevee avec la race Montbeliarde et la plus faible avec la race Abondance.

De facon a etudier la relation entre les conditions de production du lait et les teneurs en composes d'interet nutritionnel dans le fromage, il est necessaire de savoir dans quelle mesure la variabilite de composition du fromage depend de celle du lait d'origine. Les effets respectifs de la composition du lait et de la transformation fromagere sur la variabilite de composition du fromage en composes d'interet nutritionnel ont donc ete etudies en conditions reelles de production du fromage et en considerant quatre technologies fromageres differentes. Les caracteristiques nutritionnelles du lait a l'origine du fromage sont soumises a de grandes variations en partie dues a l'espece animale (vache vs. chevre). Mis a part les aspects lies a la teneur en matiere seche du fromage, la variabilite de composition du fromage en acides gras, en β-carotene, en xanthophylles et en vitamine E depend principalement de la composition du lait d'origine, alors que pour la vitamine A celle-ci est influencee a la fois par la composition du lait d'origine et par la transformation fromagere. Par contre, la composition en folates et en mineraux du fromage, ainsi que son potentiel antioxydant total, varient principalement avec la transformation fromagere. Par ailleurs, le type de technologie fromagere exerce un effet important sur la composition du fromage en mineraux et en folates, mais n'a aucun effet sur les autres composes influences par la transformation fromagere. En consequence, la teneur du fromage en composes liposolubles, contrairement aux composes hydrosolubles, depend directement des conditions de production du lait. Le potentiel antioxydant total des fromages a pâte pressee, a la difference de leur lait d'origine, est positivement correle avec certains composes antioxydants liposolubles. Il pourrait par consequent etre influence par les conditions de production du lait.

International audience; The interactions between botanical composition of pasture, quality of herbage grazed, performances of dairy cows and sensory and nutritional properties of dairy products were investigated using an integrated system approach. Two contrasting grazing systems were evaluated from May to September in two years. The treatments included a continuous grazing system (DIV) managed at a lenient stocking rate (1.0 LU ha−1) on a botanically-rich permanent pasture, and a rotational grazing system (PROD) set up at a higher stocking rate (1.7 LU ha−1) on a former temporary grassland presenting moderate biodiversity. DIV aimed to maximize biodiversity and obtain high sensory and nutritional quality cheese, whereas PROD was oriented towards milk production and herbage quality. In each system, 12 non-feed-supplemented Montbéliarde cows were used. The DIV system led to higher milk production per cow in the early grazing season than the PROD system (22.2 vs. 19.9 kg d−1). At the beginning of summer, this milk production pattern was inverted following a decrease in grass nutritive value in the DIV system. In parallel, DIV cows showed a more marked loss of body condition than PROD cows over the season. In terms of milk fatty acid profile, the DIV system proved very interesting early in the grazing season but lost its value over time as the herbage matured. Cheese sensory properties differed between systems only after a long ripening period (6 months). Regarding the ecological performances, the DIV plot showed greater botanical and entomological biodiversity than the PROD plot. This study provides evidence that the balance between animal performances, dairy product quality and biodiversity in dairy systems is more complex than previously thought, since the expected benefits of each system vary markedly over periods. The evolution of herbage vegetation stage during the grazing season combined with the botanical composition of the pasture is a key component for understanding these variations.

The relation between the useful material content (protein+fat content) of milk and cheese yield was analyzed on 189 manufactures of pressed uncooked cheeses. These manufactures were realized under controlled conditions in the same experimental cheese dairy, within the frame- work of eight different experiments, from milks of high hygienic quality (cows free of clinical mas- titis) partially skimmed so as to have a fat/protein ratio of 1.15. The fat+protein content of manufactured milks varied from 55 to 85 g.kg -1 . The relation between fat+protein content and cheese yield was lin- ear for this wide range of variation. Fat+protein content accounted for 77% of fresh yield and 87% of dry matter yield variability. Once the effect of fat and protein contents have been taken into account, other milk parameters (pH, κ-casein variants) may have a significant effect on cheese yield, but in a marginal way. milk / fat and protein contents / cheese yield

The transfer of monoterpenes and sesquiterpenes from forages into milk fat was stud- ied in a group of cows fed successively with forages containing high and low amounts of these sub- stances. In a first 24-d period the cows received 11 kg of a cocksfoot hay containing low quantities of monoterpenes and sesquiterpenes. In a second 36-d period, 3 kg of the cocksfoot were replaced by 3 kg of yarrow, a plant rich in terpenoids. In a third 24-d period the cows returned to the cocksfoot- based diet they were fed in the first period. The quantities of monoterpenes and sesquiterpenes des- orbed from the milk fat were measured by dynamic headspace - gas chromatography - mass spec- trometry. Results showed that the quantities of monoterpenes had increased by the first milking carried out 8 h after ingestion of yarrow, whereas the increase in the quantities of sesquiterpenes was observed only after the third milking, 32 h after the diet change. The maximal quantities of monoterpenes and sesquiterpenes were measured after 4 d of the yarrow-enriched diet, after which the total quantities decreased, despite the constant supply of yarrow. Four days after discontinuing yarrow the amounts of monoterpenes and sesquiterpenes desorbed from the milk fat reverted to those measured during the first period. traceability / type of feeding / terpenoid analysis / purge-and-trap / gas chromatography-mass spectrometry

Forty-two multiparous dairy cows of 3 different breeds (Holstein, Montbeliarde and Taren- taise) were divided into 2 groups (A and B) according to β- and κ-casein genetic variants, and were fed 3 floristically different types of hay (cocksfoot, rye-grass-rich and native mountain grassland hay) according to a 3 〈 3 Latin-square design. The milk produced by these cows was used to make Saint-Nectaire-type cheese, using identical and controlled cheesemaking techniques. The cheeses made from cocksfoot diet milk had higher pH (P < 0.01), lower fat in dry matter ( P < 0.05), more elas- tic texture and a strong cellar odour ( P < 0.1). The cheeses produced from the milk of cows fed native mountain grassland hay exhibited a slightly gritty and yellower body, and had a pronounced vinegar and cabbage odour. Rheological analysis confirmed the beneficial effect of the B variant of β- and κ-caseins on milk rennet clotting ability. This effect did not seem to affect the cheeses because they could not be distinguished by any of their sensory characteristics. milk / cheese / genetic variant / diet

Cette synthèse fait le point sur les effets directs et les conséquences de modifications de la conduite des animaux à la traite. Les effets recherchés répondent à des besoins de pilotage du troupeau ou de maîtrise de la qualité du lait. Ils visent à ajuster le niveau de production laitière sur l’exploitation, optimiser la qualité chimique, structurelle et microbienne du lait et piloter la conduite du troupeau. Les moyens pour intervenir sont variés allant de modifications de fréquence/intervalles de traite, à l’optimisation de la conception et des réglages de la machine à traire et des systèmes de stockage/réfrigération du lait en passant par les pratiques de traite. Il ressort de cette synthèse que la modulation de la fréquence de traite est un outil efficace pour moduler la production de lait et la durée de la lactation, et qu’elle peut contribuer à améliorer les performances de reproduction, gérer les réserves corporelles des vaches et dans certains cas limiter l’apparition de boiteries. Les choix de matériel de traite et de stockage/refroidissement du lait ainsi que les réglages de la machine à traire permettent d’optimiser l’extraction du lait, la durée de la traite et de collecter et conserver un lait d’une qualité maîtrisée sans nuire à la santé de la mamelle. Enfin, l’entretien de la machine à traire, les pratiques de traite et la peau des trayons des animaux semblent jouer un rôle primordial sur la richesse des laits crus en germes d’intérêt pour l’industrie laitière, les équilibres microbiens résultant d’une combinaison de pratiques de production dont la hiérarchisation reste encore difficile., This review covers the effects of alterations to the standard milking routine in order to manage on-farm milk production, optimise the component and microbial composition of milk and optimise herd management, through altering milking frequency and milking intervals, proper functioning of the milking machine and hygiene practices during milking. It is discussed how milking frequency can be an effective tool to manage both milk production and lactation length, as well as to improve reproductive performance and body condition and to reduce the incidence of lameness in cows. The review also highlights the role of the milking machine in determing milking speed and milk quality. Finally it is discussed how the proper maintenance of the milking machine, the milking practice itself and the skin condition of the teats are critical factors in controlling the microbial profile in unpasteurized milk.

International audience

The diversity of the microbial community on cow teat skin was evaluated using a culture-dependent method based on the use of different dairy-specific media, followed by the identification of isolates by 16S rRNA gene sequencing. This was combined with a direct molecular approach by cloning and 16S rRNA gene sequencing. This study highlighted the large diversity of the bacterial community that may be found on teat skin, where 79.8% of clones corresponded to various unidentified species as well as 66 identified species, mainly belonging to those commonly found in raw milk ( Enterococcus , Pediococcus , Enterobacter , Pantoea , Aerococcus , and Staphylococcus ). Several of them, such as nonstarter lactic acid bacteria (NSLAB), Staphylococcus , and Actinobacteria , may contribute to the development of the sensory characteristics of cheese during ripening. Therefore, teat skin could be an interesting source or vector of biodiversity for milk. Variations of microbial counts and diversity between the farms studied have been observed. Moreover, Staphylococcus auricularis , Staphylococcus devriesei , Staphylococcus arlettae , Streptococcus bovis , Streptococcus equinus , Clavibacter michiganensis , Coprococcus catus , or Arthrobacter gandavensis commensal bacteria of teat skin and teat canal, as well as human skin, are not common in milk, suggesting that there is a breakdown of microbial flow from animal to milk. It would then be interesting to thoroughly study this microbial flow from teat to milk.

This study is the first that assessed the influence of farming practices and individual cow characteristics on a large number of microbial groups (n = 10) and cow samples (n = 192). Its aim was to establish how farming practices and intrinsic characteristics of dairy cows can influence the microbiota on teat skin. Microbial flora of 96 cow teat skin from 16 farms, sampled during milking and before washing, was counted on ten dairy-specific media. Gram-positive catalase-positive bacteria including coagulase-negative staphylococci, were at high level on teat skin (4.7 ± 1.5 log cfu.mL−1) whereas lactobacilli, enterococci, Gram-negative bacteria, moulds and yeasts were at a level below 3 log cfu.mL−1. Gram-positive catalase-positive bacteria and yeasts were lower in heifers and when milking hygiene practices were intensive. Higher Lactobacillus and Enterococcus counts were linked to a silage-based diet, free stalls with straw bedding and moderate milking hygiene but also to multiparous cows. This study showed that dairy cow characteristics could interact with farming practices to affect the counts of microbial flora on teat skin. It offered prospects to better control teat microbial balance taking into account the milking hygiene practices, the parturition and the type of animal housing.

International audience; To determine how farming practices and the intrinsic characteristics of individual dairy cows can influence the composition of the microbial community on teat skin, sixteen dairy farms in the Cantal region of France were studied. Microbial groups of the teat skin of 6 dairy cows per farm were counted using 10 dairy-specific media. Farms were classed into three groups according to the milking hygiene practices, the litter and the forage. Cows were also classed into three groups according to individual characteristics. Teat hygiene seems to be the factor that causes the greatest changes in the level of microbial flora on the teat. Whatever the type of practice, rather young cows are associated with lower levels of microbial flora on the teat skin. The microbial community on cow teat skin belonging to 3 groups of farms was evaluated by combining a culture-dependent method and a direct molecular approach. The diversity of this microbial community was large as 79.8% of clones corresponded to unidentified and 66 identified species belonging to most of those commonly found in raw milk. Then teat skin is an interesting source or vector of biodiversity for milk.

International audience; The objective of this work was to compare milk fatty acid (FA) profile and texture and appearance of Cantal cheeses obtained from cows grazing 2 different upland grasslands: a highly diversified pasture (74 species) of area 12.5 ha managed under continuous mode (C), and a weakly diversified pasture (31 species) of area 7.7 ha (an old temporary grassland) managed under rotational mode (R). A control group of cows fed a hay-based diet (indoors, I) was used. Three equivalent groups of 12 Montbeliarde cows underwent the 3 treatments from May to September 2008. The cheeses were manufactured during 3 consecutive days in early June, early July, and late August (27 cheeses in all). The texture, appearance, and chemical composition of the cheeses were determined after 12 wk of ripening. Concentrations of total saturated FA and monounsaturated FA were higher and lower, respectively, in I milks compared with pasture milks. The concentrations of trans-11-C18:1 and cis-9-C18:1, and polyunsaturated FA as well as yellowness decreased during the season in C-derived milk but remained constant in R-derived milk, through a combined effect of grass development stage and the cows' grazing selection. The I cheeses were, on average, firmer, less creamy, less elastic, and less yellow than the pasture cheeses. Decreasing and increasing trends in texture firmness during the season were observed for C and R cheeses, respectively. The rind of the pasture-fed cow cheese had fewer, less intensely colored, and less prominent spots than did that of I cheeses. This difference was probably due to greater migration of fat to the rind during pressing because of the lower fat melting point of the pasture-fed cow cheeses, which had higher unsaturated FA content. The greater amounts of fat deposited on the rind of the pasture-fed cow cheeses may have partially inhibited the microbial activity responsible for rind appearance. Our trial underlines the importance of the effects of grazing management associated with vegetation type on milk and cheese characteristics.

International audience; The aim of this study was to evaluate the milk properties and the yield and sensory properties of Cantal cheese made with milk from Holstein or Montbeliarde cows milked once or twice daily. Sixty-four grazing cows [32 Holstein (H) and 32 Montbeliarde (M) cows] in the declining phase of lactation (157 d in milk) were allocated to 1 of 2 equivalent groups milked once daily (ODM) or twice daily (TDM) for 7 wk. The full-fat raw milk collected during 24 h from the 4 groups of cows (M-TDM, M-ODM, H-TDM, and H-ODM) was pooled and processed into Cantal cheese 4 times during the last 4 wk of the experimental period. In all, 16 cheeses were made (2 milking frequencies x 2 breeds x 4 replicates) and analyzed after a ripening period of 15 and 28 wk. The results showed that for both breeds, the pooled milk content of fat, whey protein, casein, total protein, and phosphorus as well as rennet clotting time and curd firming time were significantly higher with ODM cows, whereas the casein-to-total protein ratio was lower, and lactose, urea, calcium, and free fatty acids contents of milk remained unchanged. The acidification and draining kinetics of the cheese as well as cheese yields and the chemical and rheological properties of the ripened cheese were not significantly modified by milking frequency. For both breeds, the cheeses derived from ODM cows had a slightly yellower coloration but the other sensory attributes, except for pepper odor, were not significantly affected by milking frequency, thereby demonstrating that ODM does not have an adverse effect on the sensory properties of Cantal cheese. Compared with that of Holstein cows, milk from Montbeliarde cows resulted in a higher cheese yield (+1.250 kg/100 kg of milk) and ripened cheeses with lower pH, dry matter, calcium, sodium chloride, and water-soluble nitrogen concentrations. These cheeses had also a less firm and more elastic texture, a more acidic taste, and a yogurt/whey aroma.

National audience

Cantal cheese was made with either raw or pasteurized milk from cows fed either pasture or a hay and concentrate diet, and was analyzed after 3- and 6-month aging. The cheese aroma was rather mild for pasteurized-milk cheese and rather strong for raw-milk cheese, and was little affected by the cows’ feeding patterns. Gas chromatography of the volatile compounds coupled with a new 8-way olfactometry device revealed 42 odorous peaks. The major odour-active compounds were butanoic acid, 2,3-butanedione, 3-methylthio-propanal, hexanal, acetic acid, isobutanoic acid, and 1-octen-3-ol. The intensity of butanoic acid was much stronger in raw-milk than pasteurized-milk cheese. The intensities of isobutanoic acid, pentanal, E-2-hexenal, cyclohexanone, tetramethylpyrazine and γ-heptalactone were lower in the 6-month-aged than the 3-month-aged cheeses, and only ethylbenzene intensity was higher. Isopentanoic acid odour was weaker when the milk had been obtained from cows fed a pasture diet.

The link between milk production practices and bacterial diversity of 67 raw milks from dairy farms in the Savoie and Haute-Savoie regions of France was studied by Single Strand Conformation Polymorphism (SSCP) analysis. The milking practices and the cleanliness of different parts of the cow housing were evaluated. The SSCP bacterial profiles allow to classify the 67 milks into three groups: group A was characterised by a majority of Gram-positive non-lactic acid bacteria (Corynebacterineae and Micrococcaceae) and a high level of hygiene in milking practices. The SSCP profiles of groups B and C were close but different from those of group A: they were both dominated by lactic acid bacteria and by a less intensive hygiene practices. The group B milks were characterised by the dominance of Gram-negative bacteria and Lactococcus lactis species while those of group C were dominated by Brevibacterium linens and Leuconostoc mesenteroides. The variation of balance between bacterial populations can be associated with differences in hygienic milking production practices.

The aim of this experiment was to study the effect of the addition, to milk, of an essential oil (EO) obtained from the hydrodistillation of plants collected from a mountain natural pasture on the milk and cheese sensory properties. The EO was mainly composed of terpenoid compounds (67 of the 95 compounds identified) as well as ketones, aldehydes, alcohols, esters, alkanes, and benzenic compounds. In milk, the addition of this EO at the concentration of 0.1 microL/L did not influence its sensory properties, whereas at 1.0 microL/L, sensory properties were modified. In cheeses, the effect of adding EO into milk was studied in an experimental dairy plant allowing the production of small Cantal-type cheeses (10 kg) in 3 vats processed in parallel. The control (C) vat contained 110 L of raw milk; in the other 2 vats, 0.1 microL/L (EO1) or 3.0 microL/L (EO30) of EO were added to 110 L of the same milk. Six replicates were performed. After 5 mo of ripening, chemical and sensory analyses were carried out on the cheeses, including determination of the volatile compounds by dynamic headspace combined with gas chromatography-mass spectrometry. The EO did not influence the sensory properties of the cheeses at the lower concentration (EO1). However, the EO30 cheeses had a more intense odor and aroma, both characterized as "mint/chlorophyll" and "thyme/oregano." These unusual odors and aromas originated directly from the EO added. In total, 152 compounds desorbing from cheese were found, of which 41 had been added with the EO; in contrast, 54 compounds of the EO were not recovered in the cheese. Few volatile compounds desorbing from cheeses, other than the added compounds, were affected by EO addition. Among them, 2-butanol, propanol, and 3-heptanone suggested a slight effect of the EO on lipid catabolism. The antimicrobial activity of terpenes is not or is only marginally involved in the explanation of the influence of the botanical composition of the meadows on the pressed cheeses sensory properties.

Terpene profiles in cheese can be considered a ‘terroir’ fingerprint as the information contained in it should enable the pastures on which the animals were fed to be recognised. Yet a certain elasticity of the signature must be taken into account when determining authentication strategies, since products acknowledged as containing a common signature may have undergone certain procedures, such as cheese making and milk pasteurisation, that could have potentially altered their terpene profiles. In this study, Cantal and Saint-Nectaire-type cheeses were made from both raw and pasteurised milk from the same herd of dairy cows that had been grazed on natural grassland. Cheeses from raw and pasteurised milk were made from the same milking on the same days. Cantal and Saint-Nectaire-type cheeses were made on 4 different days, alternatively over four weeks. The terpenes in the cheese fat were analysed by dynamic headspace/gas chromatography/mass spectrometry. A great diversity of monoterpenes, sesquiterpenes and oxygen-containing derivatives were identified. The major terpenes identified in most cheeses were β-caryophyllene, α- and β-pinene and limonene. Milk pasteurisation did not induce changes in the terpene profile of the cheese. Significant differences (p < 0.001) were observed between Cantal and Saint-Nectaire cheeses: α-pinene, β-myrcene and β-phellandrene were, respectively, three, five and five times more abundant in Cantal cheese, while tricyclene, α-phellandrene and geraniol were found exclusively in Cantal cheese. In contrast, unidentified sesquiterpenes with retention indices (KI) = 1342 and 1511, α-cubebene, longifolene and γ-elemene were more abundant or exclusively found in Saint-Nectaire cheese. A significant relationship with the date of milking (p < 0.01) was observed for α-pinene and tricyclene in Cantal, for β-myrcene, δ-3-carene, p-cymene and α-terpinene in Saint-Nectaire cheese. Copyright © 2005 Society of Chemical Industry

Twenty-eight multiparous dairy cows were divided into 2 groups: one group (S) was fed a ray-grass silage diet and the other one (H) a hay-based diet. The milk produced by these cows was used to make Saint-Nectaire-type cheese on one day and Cantal cheese on the following day, using identical, controlled cheesemaking techniques for each model. The S cheeses, regardless of the model, had higher fat (P < 0.01) and fat in dry matter (P < 0.05) contents but lower total nitrogen content (P < 0.001) and exhibited a more yellow tone. The differences in sensory characteristics were more pronounced in Cantal cheeses: H cheeses had more "butter" and "grass" odours, "citrus fruits" - "hay" -"hazelnut" aromas and more persistent flavour than S cheeses, which showed more "alcohol" odour, "chemical" aroma and had a less "melting", "mellow" texture. The dietary effect was greater with Cantal cheese because of a diet / cheese model interaction., Effet d'une alimentation à base d'herbe ou de foin sur les caractéristiques du fromage : interactions avec le modèle technologique. Vingt-huit vaches laitières ont été divisées en deux groupes : l'un (S) a reçu un régime à base d'ensilage de ray-grass et l'autre (H) à base de foin. Le lait de ces animaux a été transformé un jour en fromage de type Saint-Nectaire et un autre jour en fromage de Cantal, dans des conditions technologiques contrôlées et identiques d'une fabrication à l'autre pour chaque type de fromage. Quelque soit le modèle fromager, les fromages S ont eu des taux plus élevés de matière grasse (P < 0,01) et d'extrait sec (P < 0,05) mais une plus faible teneur en azote total (P < 0,001) et ils ont été plus jaunes. Les différences de caractéristiques sensorielles ont été plus marquées dans le cas du Cantal : les fromages H ont été caractérisés par des odeurs " beurre " et " herbe ", des arômes " agrumes ", " foin ", " noisette ", et une flaveur plus persistante que les fromages S, qui ont révélé une odeur d'" alcool ", un arôme " chimique " et une texture moins " fondante " et " moelleuse ". L'effet régime alimentaire a été plus marqué dans le cas du fromage de Cantal révélant une interaction entre l'alimentation des animaux et le modèle fromager.

Abstract This review summarizes the recent developments in understanding of the relationships between the diet of animals and the sensory quality of dairy products. Feeding dairy cattle with maize silage by comparison with hay or grass silage leads to whiter and firmer cheeses and butter and sometimes to differences in flavour. Major differences in sensory characteristics were observed between cheeses made with milk produced by cows on winter diets (based on hay and grass silage) or turned out to pasture in the spring. Conversely, preserving grass as silage, by comparison with hay, has no major effect on cheese sensory characteristics, except on colour, the cheese being yellower with grass silage. Several recent experiments have shown a significant effect of grass botanical composition on cheese texture and flavour. These effects are due to the presence in milk of specific molecules directly introduced by feeding (carotenes, terpenes) or produced by the animals (plasmin, fatty acids) under the effect of specific diets.

The composition and sensory characteristics of matured cheeses are controlled by a number of factors, among which the type of feed is important. The influence of feeding can be reflected by the presence in cheeses of terpenes and sesquiterpenes, compounds typically indicating their vegetable origin (Mariaca et al. 1997). Indeed, several investigators have already established that these compounds could characterize the forage even to a specific geographical location. Dumont & Adda (1978), Dumont et al. (1981), Guichard et al. (1987), Bosset et al. (1994) and Moio et al. (1996) were thus able to distinguish cheeses from lowland and upland regions. In most of these studies, the conditions under which milk was produced and processed were not completely controlled. Furthermore, all these studies analysed only the volatile fraction of cheeses and did not examine the volatile compounds in the forages used. Recently Bosset et al. (1994), in one part of the project described by Jeangros et al. (1997), showed that highland grass with a highly diversified botanical composition produces milk and cheeses with significantly different chemical compositions from those from lowland grass. To improve our understanding of the relationship between animal feed and cheese composition, we have investigated under controlled experimental conditions both the composition of the terpene and sesquiterpene fractions of four forages with different botanical diversities and the influence of those forages on the terpene fraction of cheeses.

Forty-two multiparous dairy cows of three different breeds (Holstein, Montbéliarde and Tarentaise) were fed on the same type of forage (natural grassland) preserved in the form of either hay (H) or silage (GS), according to a changeover design (two 4 week periods). The proportion of concentrate in the diet and the energy and nitrogen contents were similar in both treatments. The milk produced by these cows was used for the manufacture of Saint-Nectaire type cheeses, under controlled and identical cheesemaking technological conditions. More cheese was produced with the H treatment milk. The cheeses made with the GS treatment milk were more yellow and tended to be more bitter. The other chemical and sensory characteristics did not differ much between the two treatments. Of the 51 volatile compounds identified, four were in significantly higher proportion in the GS than in the H cheeses. Cheeses produced from Tarentaise cows' milk were more yellow and their pH was higher than those made with the milk of Holstein or Montbéliarde cows. The cheeses from Montbéliarde and Tarentaise cows' milk were firmer, more melting and tastier than those made with the milk of Holstein cows. Although some trends were apparent, there were no significant differences in cheese volatile compounds for different breeds.

National audience

National audience