Application of Multielement Stable Isotope Ratio Analysis to the Characterization of French, Italian, and Spanish Cheeses

Abstract

The stable isotope ratios (delta13C, delta15N, and delta34S of casein and delta13C and delta18O of glycerol) measured by IRMS of French, Italian, and Spanish cheeses are presented and discussed. Variability factors such as animal-feeding regimen, geographical origin, and climatic and seasonal conditions were studied to check the possibilities of cheese characterization offered by each isotopic parameter. Delta13C values of both casein and glycerol appeared to be strongly correlated to the amount of maize in the animal diet. Delta15N and delta34S of casein proved to be mostly influenced by the geoclimatic conditions of the area (aridity, closeness to the sea, altitude). Delta18O of glycerol was more dependent on the geographical origin of the cheeses and on climatic/seasonal parameters. By applying a multivariate stepwise canonical discriminant analysis, good discrimination possibilities for the different European cheeses were obtained, confirmed by the classification analysis, when >90% of the samples were correctly reclassified.

Influence of dietary composition on the carbon, nitrogen, oxygen and hydrogen stable isotope ratios of milk

“…Comparing the casein values with those of the feed, we observed an increase in the d 15 N values of about 2.8% for farm C and 2.1% for farm M. This situation is in agreement with what has been observed in meat protein, 39 even with less individual variability, 17 in cheese casein, 11 and in bulk milk. 25 The different 15 N enrichment observed in the two farms led to significantly ( p < 0.001) different d 15 N values of the relevant milk casein (C ¼ 5.6 AE 0.2%; M ¼ 4.6 AE 0.1%), which were not evident between the two overall diets.…”

“…The d 13 C values corresponded with those in the literature, 6,11,19,20,24 in particular with those for feed from Germany, probably due to the similar climatic conditions. The d 15 N values appeared to be more variable, having been proved to be influenced by a greater number of factors including soil conditions, climate, distance from the sea, fixation of nitrogen from air, intensity of crop practices and the use of fertiliser.…”

“…The d 15 N values appeared to be more variable, having been proved to be influenced by a greater number of factors including soil conditions, climate, distance from the sea, fixation of nitrogen from air, intensity of crop practices and the use of fertiliser. 11,16,28 As expected, the C 4 feeds (maize silage and maize flour) showed higher d 13 C values than the C 3 plants (hay of Medicago sativa, Festuca arudinacea and Lolium multiflorum, soybean, barley, cotton seed), due to the different photosynthetic CO 2 fixation pathways used by plants. 29 Table 2.…”

“…11 The D/H and 18 O/ 16 O ratios of feed and casein were measured in one run using IRMS following pyrolysis of the sample in a high-temperature conversion/elemental analyser (TC/EA; ThermoFinnigan). A high furnace temperature (14508C), low instrumental H 3 factor (<8, for correction of the contribution of [H 3 ] þ to the m/z 3 signal) 27 and special care to maintain dry conditions during analysis were ensured, to obtain reproducible results.…”

“…The aims of these studies were to obtain dietary reconstruction, to study animal movement patterns, [1][2][3][4][5] and to characterise the geographical origin. [6][7][8][9][10][11][12][13][14][15][16] Another important aim could be to study and quantify the alteration of stable isotope ratios (SIRs) in milk by substituting a C 3 plant diet with maize. This could be important in order to protect milk and milk derivatives produced using traditional or 'organic' practices of pasture compared with products produced with cheaper diets based on maize derivatives.…”