The trans-18:1 acid content and distribution in fats from ewe and goat milk, beef meat and tallow were determined by a combination of capillary gas-liquid chromatography and argentation thin-layer chromatography of fatty acid isopropyl esters. The trans isomers account for 4.5 _+ 1.1% of total fatty acids in ewe milk fat (seven samples) and 2.7 +_ 0.9% in goat milk fat (eight samples). In both species, as in cow, the main isomer is vaccenic (trans-11 18:1) acid. The distribution profile of trans-18:1 acids is similar among the three species. The contribution of ewe and goat milk fat to the daily intake of trans-18:1 acids was estimated for people from southern countries of the European Economic Community (EEC): France, Italy, Greece, Spain, and Portugal. It is practically negligible for most of these countries, but in Greece, ewe and goat milk fat contribute ca. 45% of the daily consumption of trans-18:1 acids from all dairy products (0.63 g/person/day for a total of 1.34 g/person/day). The trans-18: t acid contents of beef meat fat (ten retail cuts, lean part) and tallow (two samples) are 2.0 +_ 0,9% and 4.6%, respectively, of total fatty acids (animals slaughtered in winter). Here too, the main isomer is vaccenic acid, Other trans isomers have a distribution pattern similar to that of milk fat. Beef meat fat contributes less than one-tenth of milk fat to the trans-I 8:1 acid consumed. The daily per capita intake of trans-18:1 acids from ruminant fats is 1,3-1.8 g for people from most countries of the EEC, Spain and Portugal being exceptions (ca. 0.8 g/person/day). In France, the respective contributions of ruminant fats and margarines to the daily consumption of trans-18:1 acids are 1.7 and 1.1 g/person/day (60 and 40% of total, respectively). These proportions, based on consumption data, were confirmed by the analysis of fat from milk of French women (ten subjects). The mean content of trans-18:1 acids in human milk is 2.0 _+ 0.6%, with vaccenic acid being the major isomer. Based on the relative levels of the trans-16 18:1 isomer, we could confirm that milk fat is responsible for the major part of the daily intake of trans-18:1 acids by French people. The daily individual intake of trans-18:l isomers from both ruminant fats and margarines for the twelve EEC countries varies from 1.5 g in Spain to 5.8 g in Denmark, showing a well-marked gradient from the southwest to the northeast of the EEC. JAOCS 72, 259-272 (1995).

The successive steps of an integrated analytical procedure aimed at the accurate determination of butterfat fatty acid composition, including trans-18:1 acid content and profile, have been carefully checked. This sequential procedure includes: dispersion of a portion of butter in hexane/isopropanol (2:1, vol/vol) with anhydrous Na2SO4, filtration of aliquots of the suspension through a microfiltration unit, subsequent preparation of fatty acid isopropyl esters (FAIPE) with H2SO 4 as a catalyst, and analysis of total FAIPE by capillary gas-liquid chromatography (GLC). Isolation of trans-18:1 isomers was by silver-ion thin-layer chromatography (Ag-TLC), followed by extraction from the gel of combined saturated and trans-monoenoic acids with a biphasic solvent system. Analysis of these fractions by GLC allows the accurate quantitation of trans-18:1 acids with saturated acids (14:0, 16:0, and 18:0) as internal standards. A partial insight in the distribution of trans-18:1 isomers can be obtained by GLC on a CP Sil 88 capillary column (Chrompack, Middelburg, The Netherlands). All steps of the procedure are quite reproducible, part of the coefficients of variation (generally less than 3%, mainly limited to butyric and stearic acids) being associated with GLC analysis (injection, integration of peaks) and, to a lesser extent, to FAIPE preparation. FA1PE appear to be of greater practical interest than any other fatty acid esters, including fatty acid methyl esters (FAME), for the quantitation of short-chain fatty acids, because peak area percentages, calculated by the integrator coupled to the flame-ionization detector, are almost equal (theoretically and experimentally) to fatty acid weight percentages and do not require correction factors. With this set of procedures, we have followed in detail the seasonal variations of fatty acids in butterfat, with sixty commercial samples of French butter collected at five different periods of the year. Important variations occur around mid-April, when cows are shifted from forage and concentrates during winters spent in their stalls to fresh grass in pastures. At this period, there is a decrease of 4:0-14:0 acids and of 16:0 (-2 and -6%, respectively), while 18:0 and cis-plus trans-18:1 acids rise suddenly (2 and 5%, respectively). These modifications then progressively disappear until late fall or early winter. Other variations are of minor quantitative importance. Although influenced by the season, the

The seed oils from twenty-five Conifer species (from four families--Pinaceae, Cupressaceae, Taxodiaceae, and Taxaceae) have been analyzed, and their fatty acid compositions were established by capillary gas-liquid chromatography on two columns with different polarities. The oil content of the seeds varied from less than 1% up to 50%. Conifer seed oils were characterized by the presence of several A5-unsaturated polymethylene-interrupted polyunsaturated fatty acids (A5-acids) with either 18 (cis-5,cis-9 18:2, cis-5,cis-9,cis-12 18:3, and cis-5,cis-9,cis-12,cis-15 18:4 acids) or 20 carbon atoms (cis-5,cis-11 20:2, cis-5,cis-11,cis-14 20:3, and cis-5,cis-11 ,cis-14,cis-17 20:4 acids). Pinaceae seed oils contained 17-31% of A5-acids, mainly with 18 carbon atoms. The 20-carbon acids present were structurally derived from 20:1 n-9 and 20:2n-6 acids. Pinaceae seed oils were practically devoid of 18:3n-3 acid and did not contain either A5-18:4 or A5-20:4 acids. Several Pinaceae seeds had a A5-acid content higher than 50 mg/g of seed. The only Taxaceae seed oil studied (Taxus baccata) had a fatty acid composition related to those of Pinaceae seed oils. Cupressaceae seed oils differed from Pinaceae seed oils by the absence of A5-acids with 18 carbon atoms and high concentrations in 18:3n-3 acid and in A5-acids with 20 carbon atoms (A5-20:3 and A5-20:4 acids). A5-18:4 Acid was present in minute amounts. The highest level of A5-20:4 acid was found in Juniperus communis seed oil, but the best source of A5-acids among Cupressaceae was Thuja occidenta[is. Yaxodiaceae seed oils had more heterogeneous fatty acid compositions, but the distribution of A5-acids resembled that found in Cupressaceae seed oils. Except for Sciadopytis verticillata, other Taxodiaceae species are not interesting sources of A5-acids. The distribution profile of AS-acids among different Conifer families appeared to be linked to the occurrence of 18:3n-3 acid in the seed oils.JAOCS 73, 765-771 (1996).

The fatty acid composition of seeds from seven species of the genusPinus (P. pinaster, P. griffithii, P. pinea, P. koraiensis, P. sylvestris, P. mughus, andP. nigra) was established. Pine seeds are rich in oil (31–68% by weight) and contain several unusual polymethylene‐interrupted unsaturated fatty acids with acis‐5 ethylenic bond. These are thecis‐5,cis‐9 18:2,cis‐5,cis‐9,cis‐12 18:3,cis‐5,cis‐11 20:2, andcis‐5,cis‐11,cis‐14 20:3 acids, with a trace ofcis‐5,cis‐9,cis‐12,cis‐15 18:4 acid. Their percentage relative to total fatty acids varies from a low of 3.1% (P. pinea) to a high of 30.3% (P. sylvestris), depending on the species. The majorcis‐5 double bond‐containing acid is generally thecis‐5,cis‐9,cis‐12 18:3 acid (pinolenic acid). In all species, linoleic acid represents approximately one‐half the total fatty acids, whereas the content of oleic acid varies in the range 14–36% inversely to the sum of fatty acids containing acis‐5 ethylenic bond. The easily available seeds fromP. koraiensis appear to be a good source of pinolenic acid: their oil content isca. 65%, and pinolenic represents about 15% of total fatty acids. These values appear to be rather constant.Pinus pinaster, which is grown on several thousand acres in the southwest of France, is an interesting source ofcis‐5,cis‐11,cis‐14 20:3 acid (7% in the oil, which isca. 35% of the dehulled seed weight), an acid sharing in common three double bonds with arachidonic acid. Apparently,P. sylvestris seed oil contains the highest level ofcis‐5 double bond‐containing acids among pine seed oils that have ever been analyzed.

The formation of linolenic acid geometrical isomers (LAGIs) was studied in linseed oil that was heated under vacuum in sealed ampoules at different temperatures (190-260°C) for several durations (2-16 h). A temperature of about 190°C seems to be necessary to induce the formation of LAGIs. At higher temperatures, disappearance of linolenic acid follows a first-order kinetic. The formation of LAGIs increases with both heating time and temperature, degrees of isomerization of linolenic acid higher than 50-60% could easily be obtained by simply heating the oil under vacuum. Side reactions remain at a low level. The mean probabilities of isomerization of individual ethylenic bonds are similar to those determined in linolenic acid-containing oils marketed in European countries, 41.9, 4.7 and 53.3% for double bonds in positions 9, 12 and 15, respectively. The di-trans t,c,t (trans, cis, trans) isomer is formed via the mono-trans c,c,t and t,c,c isomers by a two-step reaction. The proportions of the c,c,t and t,c,c isomers (relative to total LAGIs) decrease linearly with the heating time. The proportion of the c,t,c isomer is only slightly affected by this parameter; however, it increases with temperature. The proportion of the t,c,t isomer increases linearly with heating time at each tested temper- ature, at the expense of the c,c,t and t,c,c isomers. However, there is no simple relationship linking the disappearance of each of the mono-trans isomers and the formation of the di-trans isomer. KEY WORDS: Deodorization, geometrical isomers, heated oil, linolenic acid, linseed oil, trans fatty acids.Linolenic acid geometrical isomers (LAGIs) have been detected in edible soybean and rapeseed oils marketed in North America (1), France (2), some other European countries (Belgium, Germany, Great Britain) (3), Poland (2) and Israel (4). They may also occur in foods containing such oils (2,5) and in refined walnut oils (6). Although LAGIs can be generated in soybean and rapeseed oils that are overheated for prolonged periods in the laboratory (7) or in restaurants (8), it is now evident that the main dietary source resides in the "fresh" commercial oils themselves.The appearance of LAGIs in oils is linked to the deodorization step (1,9}. This operation is generally conducted at high temperatures (230 to 250°C) (10,11), under vacuum and in the presence of steam, for periods ranging from a few minutes to several hours. The resulting LAGIs have the structure cis- 9#is-12,trans-15, trans-9#is-12#is-15 (85-90% of total LAGIs), cis-9,trans-12,cis-15, trans-9, cis-12,trans-15 (10-15%) and trans-9,trans-9#is-15 and cis-9,trans-12,trans-15 (trace amounts, generally not detected without preliminary concentration) (1,5).

The delta5-unsaturated polymethylene-interrupted fatty acid (delta5-UPIFA) contents and profiles of gymnosperm seeds are useful chemometric data for the taxonomy and phylogeny of that division, and these acids may also have some biomedical or nutritional applications. We recapitulate here all data available on pine (Pinus; the largest genus in the family Pinaceae) seed fatty acid (SFA) compositions, including 28 unpublished compositions. This overview encompasses 76 species, subspecies, and varieties, which is approximately one-half of all extant pines officially recognized at these taxon levels. Qualitatively, the SFA from all pine species analyzed so far are identical. The genus Pinus is coherently united--but this qualitative feature can be extended to the whole family Pinaceae--by the presence of delta5-UPIFA with C18 [taxoleic (5,9-18:2) and pinolenic (5,9,12-18:3) acids] and C20 chains [5,11-20:2, and sciadonic (5,11,14-20:3) acids]. Not a single pine species was found so far with any of these acids missing. Linoleic acid is almost always, except in a few cases, the prominent SFA, in the range 40-60% of total fatty acids. The second habitual SFA is oleic acid, from 12 to 30%. Exceptions, however, occur, particularly in the Cembroides subsection, where oleic acid reaches ca. 45%, a value higher than that of linoleic acid. Alpha-linolenic acid, on the other hand, is a minor constituent of pine SFA, almost always less than 1%, but that would reach 2.7% in one species (P. merkusii). The sum of saturated acids [16:0 (major) and 18:0 (minor) acids principally] is most often less than 10% of total SFA, and anteiso-17:0 acid is present in all species in amounts up to 0.3%. Regarding C18 delta5-UPIFA, taxoleic acid reaches a maximum of 4.5% of total SFA, whereas pinolenic acid varies from 0.1 to 25.3%. The very minor coniferonic (5,9,12,15-18:4) acid is less than 0.2% in all species. The C20 elongation product of pinolenic acid, bishomo-pinolenic (7,11,14-20:3) acid, is a frequent though minor SFA constituent (maximum, 0.7%). When considering C20 delta5-UPIFA, a difference is noted between the subgenera Strobus and Pinus. In the former subgenus, 5,11-20:2 and sciadonic acids are < or =0.3 and < or =1.9%, respectively, whereas in the latter subgenus, they are most often > or =0.3 and > or =2.0%, respectively. The highest values for 5,11-20:2 and sciadonic acids are 0.5% (many species) and 7.0% (P. pinaster). The 5,11,14,17-20:4 (juniperonic) acid is present occasionally in trace amounts. The highest level of total delta5-UPIFA is 30-31% (P. sylvestris), and the lowest level is 0.6% (P. monophylla). Uniting as well as discriminating features that may complement the knowledge about the taxonomy and phylogeny of pines are emphasized.

The fatty acid compositions of rapeseed and soybean oils marketed in France have been determined by gas liquid chromatography on a fused-silica capillary column coated with a 100% cyanopropyl polysiloxane stationary phase. Under the operating conditions employed, methyl esters of linolenic acid geometrical isomers could be separated and quantitated easily without any other complementary technique. With only one exception, all samples under study (eight salad oils and five food samples) contain geometrical isomers of linoleuic acid in measurable, although variable, amounts. Total tran~18:3 acids may ao count for up to 3% of total fatty acids. This value col responds to a degree of isomerization (percentage of trans isomers relative to total oc~adecatrienoic acids) of 30%. Examination of our data indicates that the distribution pattern of linolenic acid geometrical isomers does not depend on the degree of isomerization. The two main isomers always have the c,c,t and the t,c,c configurations. These isomers occur in the almost invariable relative proportions of 47.8 --_. 1.7% and 41.1 --1.0%, respectively. The third mon~trans isomer is present in lower amounts--6.5 --4"--0.7%. The only di-trans isomer that can be quantitated with sufficient accuracy is the t,c,t isomer (4.9 +--1.5%).Monwtrans isomers of linoleic acid are also present in these oils. However, their maximum percentages are lower than those determined for linolenic acid geometrical isomers. In the oils showing the highest degrees of isomerization, trans isomers of linoleic acid account for 0.5% (rapeseed oils) and 1% (soybean oils) of total fatty acids. Taking into account all data, it would appear that the probability of isomerization of linolenic acid is about 13-14 times that of linoleic acid. KEY WORDS: Fatty acid composition, linoleic acid, linolenic acid, rapeseed oil, soybean oil, trans isomers.Deodorization is an important step in rapeseed and soybean oil refining. This operation is realized at high temperature (optimum range of 245-250~ under vacuum (absolute pressure of 1-6 mm Hg) for 15 min to several hours in the presence of steam (1). However, such conditions have been shown to induce geometrical isomerization of linoleic (cis-9~is-12 18:2, further referred to in the text as the r or all-cis isomer) and linolenic (cis-9~is-12~is-15 18:3, further referred to in the text as the r162 or aU-c/s isomer) acids (2,3). Refined soybean and rapeseed oils marketed in North America may contain up to 25% of their total 18:3 acids as geometrical isomers (2). The main isomers that accumulate have the r162 and the t,r structures. These artefacts are accompanied by smaller amounts of the Ct, c and t,c,t isomers (2).

Twelve commercial samples of French butter, purchased in October-November, and 12 other samples, purchased in May-June, were analyzed with particular attention to their tr~tadecenoic acid contents. The isomeric fatty acids were quantitated by a combination of gas-liquid chromatography (GLC) of total fatty acids as isopropyl esters on a polar capillary column (CPSi188) and of silver nitrateimpregnated thln-layer chromatography followed by GLC of the pooled saturated {used as internal standards) and trans-octadecenoic acid fractions. Autumn butters contained 3.22 ___ 0.44% trans-octadecenoic acids (relative to total fatty acids), whereas those collected during the spring contained 4.28 +---0.47% (P < 0.01). Minimum and maximum values for the two sets of butters were 2.46 (autumn) and 5.10% (spring), respectively. The annual mean value for the trans~ctadecenoic acid content in all butter sampies was 3.8% of total fatty acids (ca. 2% for the tran~11 18:1 acid). This value allows calculation of the daily individual intake of ~deeenoic acids from dairy products by populations of member states of the European Economic Community (EEC}. It varies from 0.57 g {Po~ tugal) to 1.66 g (Denmark). The mean value for the twelve countries of the EEC is 1.16 g/person/d, which is close to data published for the United States. In France, the consumption of trans octadecenoic acids from dairy fat is higher than that from margarines (ca. 1.5 vs. 1.1 g/person/d).