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 transfer of monoterpenes and sesquiterpenes from forages into milk fat was studied in a group of cows fed successively with forages containing high and low amounts of these substances. 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 cocksfootbased diet they were fed in the first period. The quantities of monoterpenes and sesquiterpenes desorbed from the milk fat were measured by dynamic headspace-gas chromatography-mass spectrometry. 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 Résumé-Transfert des monoterpènes et des sesquiterpènes des fourrages dans la matière grasse du lait. Le transfert des monoterpènes et des sesquiterpènes des fourrages dans la matière grasse du lait a été étudié sur un lot de vaches successivement nourries avec des fourrages riches ou pauvres

-To assess the relationship between conditions of milk production and cheese contents of components of nutritional interest, it is necessary to know to what extent the compositional variability of cheese depends on that of milk. The respective effects of milk composition and the cheese-making process on cheese compositional variability in components of nutritional interest were therefore studied under real conditions of cheese production considering four different cheese-making technologies. The nutritional characteristics of the original milk were subject to high variations partly due to animal species (cow vs. goat). Apart from the aspects related to the dry matter content of cheese, the cheese compositional variability in fatty acids, β-carotene, xanthophylls and vitamin E depended mainly on the composition of the original milk. For vitamin A, it was partially influenced by both the original milk composition and the cheese-making process. Regarding folates and minerals, as well as total antioxidant capacity, the cheese composition varied mainly with the cheese-making process. In addition, the cheese-making technology had a significant effect on the cheese composition in minerals and folates, but did not influence the other components affected by the cheesemaking process. Consequently, the cheese contents of fat-soluble compounds depend directly on the conditions of milk production. On the contrary, the composition of cheese in water-soluble compounds varies independently of the conditions of milk production. The total antioxidant capacity of pressed cheeses, unlike the original milk, was positively correlated with some fat-soluble antioxidants. It could therefore be influenced by the conditions of milk production. Résumé -Effets respectifs de la composition du lait et de la transformation fromagère sur la variabilité de composition du fromage en composés d'intérêt nutritionnel. De façon à étudier la relation entre les conditions de production du lait et les teneurs en composés d'intérêt nutritionnel dans le fromage, il est nécessaire de savoir dans quelle mesure la variabilité de composition du fromage dépend de celle du lait d'origine. Les effets respectifs de la composition du lait et de la transformation fromagère sur la variabilité de composition du fromage en composés d'intérêt nutritionnel ont donc été étudiés en conditions réelles de production du fromage et en considérant quatre technologies fromagères différentes. Les caractéristiques nutritionnelles du lait à l'origine du fromage sont soumises à de grandes variations en partie dues à l'espèce animale (vache vs. chèvre). Mis à part les aspects liés à la teneur en matière sèche du fromage, la variabilité de composition du fromage en acides gras, en β-carotène, en xanthophylles et en vitamine E dépend principalement de la composition du lait d'origine, alors que pour la vitamine A celle-ci est influencée à la fois par la composition du lait d'origine et par la transformation fromagère. Par contre, la composition en folates et en minéraux du fr...

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.

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.