Carmen Cuesta

Trans fatty acid production in deep fat frying of frozen foods with different oils and frying modalities

Abstract Frying process has been considered to be a source of trans fatty acids. However, most trans fatty acids found in foods would come from the oil used and not from the process itself. To test this, the trans fatty acid production was measured frying in extra virgin olive oil (EVOO), high oleic sunflower oil (HOSO) and sunflower oil (SO) various frozen foods 20 times with frequent replenishment (FR) or without replenishment (NR) of the used oil with fresh oil during the frying. Further, the fat extracted from potatoes fried in the EVOO, HOSO and SO from the frying 8 and 20 was also analyzed by gas liquid chromatography to compare it trans fatty acid profile with that of the corresponding fryer oil. Trans fatty acids appear in lower amounts than 5 mg/g oil or fat in both FR and NR. Elaidic acid was the most abundant trans fatty acid in EVOO or in the fat extracted from EVOO fried potatoes while trans linoleic isomers were more abundant in SO. HOSO was in between. Present data suggest that frequent addition of fresh oil through the frying process minimizes the fatty acid changes contributing to obtain fried foods with less amount of trans fatty acids. The consumption of a large standard ratio (∼ 140 g) of these fried potatoes would implied the irrelevant amount of less than 0.13 g of trans fatty acids.

Eicosanoid production, thrombogenic ratio, and serum and LDL peroxides in normo- and hypercholesterolaemic post-menopausal women consuming two oleic acid-rich diets with different content of minor components.

The present paper compares the effects of two monounsaturated oils, extra virgin olive oil (EVOO) and high-oleic acid sunflower oil (HOSO), on serum and LDL peroxides, eicosanoid production and the thrombogenic ratio (thromboxane (TX) B2:6-keto-prostaglandin F1alpha) in fourteen non-obese post-menopausal women. The subjects, mean age 63 (SD 11) years, were assigned to two consecutive oleic acid-rich 28 d dietary periods. EVOO and HOSO represented 62 % of the total lipid intake and were used as the only culinary fat during the first and second dietary periods respectively. Serum peroxides, plasma alpha-tocopherol and TXB2 levels in stimulated platelet-rich plasma (PRP-TXB2) were significantly higher (P < 0.01, P < 0.001, and P < 0.05, respectively) after the HOSO diet than after the EVOO diet. The relationship between the serum cholesterol level (< 6.21 mmol/l or > or = 6.21 mmol/l) and the type of dietary oil on eicosanoids, peroxides and alpha-tocopherol were evaluated by two-way ANOVA. Dietary oil significantly affected (P < 0.05) the PRP-TXB2 level, whereas serum and LDL peroxides were significantly affected (P < 0.001 and P < 0.01, respectively) by the serum cholesterol level. The plasma alpha-tocopherol level was significantly affected by the serum cholesterol level and the type of dietary oil (both P < 0.001). No significant relationships were found between serum cholesterol levels, serum peroxide or LDL peroxide levels, plasma alpha-tocopherol concentrations or alpha-tocopherol intakes with eicosanoid production or the thrombogenic ratio due to dietary changes. However, in spite of their higher alpha-tocopherol levels, hypercholesterolaemic subjects showed increased peroxidation in serum and LDL in comparison with normocholesterolaemic subjects on the HOSO diet in comparison with the EVOO diet. These findings suggest that differences in the type of minor compounds, as well as in the concentration of linoleic acid, in both these monounsaturated oils may play an important role in modulating eicosanoid production and lipoprotein peroxidation when they constitute a large proportion of the diet of post-menopausal women.

Male and female cord blood lipoprotein profile differences throughout the term-period.

Age- and gender-related differences in cord serum lipids and lipoproteins were studied in 548 singletons from the Toledo Study, Spain, aged 37.0- < 42.0 wk, with body weight between 2.500 and 3.999 kg and Apgar score of > or = 7 at 1 min and > or = 9 at 5 min. Cord total cholesterol (TC) and LDL-cholesterol were significantly higher in females than in males (1.89 +/- 0.53 vs 1.72 +/- 0.42 mmol/l, p < 0.001; and 0.88 +/- 0.43 vs 0.74 +/- 0.36 mmol/l, p < 0.001, respectively). With the exception of triglycerides which significantly increased through the term period in males and females (both p < 0.01), other serum and lipoprotein lipids remained rather constant between wks 38 and 42 in both sexes. However, all lipids and lipoproteins tended to be higher in 38 wk- than in 37 wk-newborns. Females showed higher HDL-cholesterol levels (p < 0.05) at wk 37, and higher TC and LDL-cholesterol values (both p < 0.05) at wks 39 and 40. TC was more or less equivalently carried by LDL and HDL in both sexes but males transported significantly more cholesterol by VLDL (p < 0.001) and less by LDL (p < 0.05) than females. TC was significantly correlated with LDL-cholesterol (p < 0.001) and HDL-cholesterol (p < 0.001). The different levels of TC and LDL-cholesterol, and the cholesterol distribution for lipoproteins in male and female neonates suggest that gender-related factors might influence lipid levels at term-period.

Deep fat frying of frozen foods in sunflower oil. Fatty acid composition in fryer oil and frozen prefried potatoes

The fatty acid pattern was used to evaluate the alteration of a sunflower oil that had been used 20 times to fry various frozen foods with frequent replenishment (FR) or without replenishment (NR) of the used oil with fresh oil during frying. Furthermore, the fat extracted from potatoes fried in the sunflower oil from fryings 1, 5, 8, 12, 16 and 20 was also analysed by gas–liquid chromatography to compare its fatty acid profile with that of the corresponding fryer oil. The amount of unaltered fatty acids decreased from 96.2 mg per 100 mg oil in the unused sunflower oil to 89.6 mg per 100 mg oil after 20 fryings in the FR oil and to 88.9 mg per 100 mg oil in the NR oil, following a linear adjustment (r > 0.97; p < 0.001). Linoleic acid also decreased while palmitic and oleic acids increased in the bath oil. Fatty acid variations were more pronounced in NR than FR oil for major fatty acids and not only related to the degradation of unsaturated fatty acids but also to the interactions between the bath oil and the fried food fat. Thus the increase in palmitic acid of the fryer oil could be due to migration of this fatty acid from the prefried frozen potatoes as revealed by the composition of the fat extracted from those potatoes. Although the fatty acid variation (eg myristic, palmitic, oleic, trans–cis isomers of linoleic and linoleic acids) was not equivalent in FR or NR fryer oil and in the fat of the potatoes, the changes in total unaltered fatty acids were not significantly different in oil and potatoes. Present data suggest that frequent addition of fresh oil throughout the frying process minimises the fatty acid changes, contributing to the obtainment of fried foods with a healthy fatty acid profile. © 2000 Society of Chemical Industry

Effects of age and cigarette smoking on serum concentrations of lipids and apolipoproteins in a male military population

The effects of age and cigarette smoking on lipids and apolipoproteins were studied in men, 20-65 years old, randomly selected from a military population in the Madrid area, Spain. Subjects were classified as non-smokers, medium smokers (10-20 cigarettes/day) and heavy smokers (more than 20 cigarettes/day). Smoking prevalence was 58%. Serum apolipoprotein A-I and HDL-cholesterol (HDL-C) were not age-dependent, while total cholesterol (TC), triglycerides (TG), LDL-cholesterol (LDL-C) and the TC/HDL-C ratio increased with age. None of the variables studied was age-dependent over 30 years. The effects of smoking on TC, TG, LDL-C, HDL-C, TC/HDL-C ratio, apolipoprotein A-I, apolipoprotein B, and apo A-I/apo B ratio in the 20-29-year-old group appeared to be prominent in heavy smokers (P values less than 0.001, less than 0.05, less than 0.01, less than 0.05, less than 0.001, less than 0.05, less than 0.01 and less than 0.05, respectively) but not in medium smokers, in which only TG increased significantly (P less than 0.001). Few differences were noted between non-smokers and smokers over 30 although the TC/HDL-C ratio did increase in heavy smokers (P less than 0.05).

Dietary effects on growth, liver peroxides, and serum and lipoprotein lipids in rats fed a thermoxidised and polymerised sunflower oil

The effect on food intake, weight gain, liver lipid peroxides, lipemia and lipoprotein composition was determined in rats fed a diet with 15% sunflower oil used repeatedly for frying and containing ∽19% polar material (group 2). These dietary effects were compared over a 4 week study period with those found in rats fed a control diet that contained 15% unused sunflower oil with ∽5% polar material (group 1). Both groups had similar food and nutrient intakes (except for linoleic acid, significantly lower (P<0·01) in group 2), yet the final weight gain and food efficiency and protein efficiency ratios were significantly lower in group 2. As a consequence of thermoxidised oil ingestion, liver homogenates from group 2 presented higher (P<0·02) levels of thiobarbituric acid reactive substances (TBARS) Liver TBARS levels were significantly correlated (P<0·01) with the amount of thermoxidised substances ingested. No treatment effect was found on VLDL lipid composition. However, the LDL fraction of group 2 animals appears enriched (P<0·05) in total and free cholesterol. In group 2 rats, phospholipids, and total and esterified cholesterol were significantly increased (P<0·05) in HDL. As a consequence of the changes in the lipoprotein composition, the amount of all forms of serum cholesterol, and serum phospholipids was significantly higher (at least P<0·05) while the amount of serum triacylglycerols remained unchanged in rats fed the used oil. HDL-phospholipids were significantly correlated (P<0·02) with the amount of thermoxidised compounds ingested. The increase in serum cholesterol and phospholipids, and in HDL-cholesterol and HDL-phospholipid concentration seens in group 2 rats may be a protective mechanism against the peroxidative stress produced by the ingestion of used sunflower oil.