Follow-up of the Delta 4 to Delta 16 trans-18 : 1 isomer profile and content in French processed foods containing partially hydrogenated vegetable oils during the period 1995-1999. Analytical and nutritional implications

A survey of the total content of trans-18:1 acids and their detailed profil e in Trench food lipids was conducted in 1995-1996, and 1999. For this purp ose, 37 food items were chosen from their label indicating the presence of partially hydrogenated vegetable oils (PHVO) in their ingredients. The cont ent as well as the detailed profile of these isomers was established by a c ombination of argentation thin-layer chromatography and gas-liquid chromato graphy (GLC) on long polar capillary columns. With regard to the mean trans -18:1 acid contents of extracted PHVO, a significant decrease was observed between the two periods, i.e., from 26.9 to 11.8% of total fatty acids. How ever, only minor differences were noted in the mean relative distribution p rofiles of individual trans-18:1 isomers with ethylenic bonds between posit ions Delta 4 and Delta 16 for the two periods, The predominant isomer was D elta 9-18:1 (elaidic) acid, in the wide range 15.2-46.1% (mean, 27.9 +/- 7. 2%) of total trans-18:1 acids, with the Delta 10 isomer ranked second, with a mean of 21.3% (range, 11.6, to 27.4%). The content of the unresolved Del ta 6 to Delta 8 isomer group was higher than the Delta 11 isomer (vaccenic acid), representing on average 17.5 and 13.3%, respectively. Other isomers Delta 4, Delta 5, Delta 12, Delta 13/Delta 14, Delta 15, and Delta 16, were less than 10% Each: 1.0, 1.6, 7.4, 7.1, 1.8, and 1.0%, respectively. Howev er, considering individual food items, it. was noted that none of the extra cted PHVO were identical to one another, indicating a considerable diversit y of such fats available to the food industry. A comparison of data for Fre nch foods with similar data recently established for Germany indicates that no gross differences occur in PHVO used by food industries in both countri es. Estimates for the absolute mean consumption of individual isomers from ruminant fats and PHVO are made for the French population and compared to s imilarly reconstructed hypothetical profiles for Germany and North America. Differences occur in the total intake of trans-18:1 acids, but most import ant, in individual trans-18:1 isomer intake, with a particular increase of the Delta 6-Delta 8 to Delta 10 isomers with increasing consumption of PHVO . It is inferred from the present and earlier data that direct GLC of fatty acids is a faulty procedure that results (i) in variable under-estimates o f total trans-18:1 acids, (ii) in a loss of information as regards the asse ssment of individual isomeric trans-18:1 acids, and (iii) in the impossibil ity of comparing data obtained from human tissues if the relative contribut ion of dietary PHVO and ruminant fats is not known.