Formation of trans fatty acids in chicken legs during frying

The formation of trans fatty acids in chicken legs during frying in unhydrogenated and hydrogenated soybean oil was studied. Frying was conducted at 160 degrees C, 180 degrees C and 200 degrees C for 15, 30, 45, 60 and 75 min, with the various cis and trans fatty acids being analyzed in unhydrogenated and hydrogenated soybean oil, as well as chicken leg meat and chicken leg skin, using a gas chromatography-mass spectrometry technique. Results showed that the amounts of most fatty acids decreased along with increasing frying temperature and frying time when fried in unhydrogenated or hydrogenated soybean oil. No trans fatty acids were formed in chicken leg meat fried in unhydrogenated or hydrogenated soybean oil. Instead, the formation of trans fatty acids was observed in chicken leg skin fried in hydrogenated soybean oil, probably because of oil absorption. A maximum level of trans fatty acids occurred 15 min after frying and then declined thereafter.     

Formation of trans fatty acids during the frying of chicken fillet in corn oil

To assess effects of heated edible oils on intake of trans fatty acids (TFAs); the formation of TFAs in cooking conditions was investigated by a frying system model, in which chicken fillet was fried in a commercial corn oil at 170?°C, for 12 frying cycles. The main TFAs detected in chicken fillet were trans C18:2 fatty acids (FAs) and trans C18:3 FAs, which exhibited no significant differences among the frying cycles. Besides, the content of trans C18:1 FAs were very low in all samples on different frying cycles. The intake of TFAs was estimated to be 0.06?g/100?g when chicken fillet fried in this process was consumed. These results suggest that an ordinary frying process upon a commercial corn oil has little impact on the daily TFAs intake.     

Nonhydrogenated cottonseed oil can be used as a deep fat frying medium to reduce trans-fatty acid content in french fries

OBJECTIVE: The purpose of this research study was to evaluate the fatty acid profile, in particular trans-fatty acids, of french fries fried in nonhydrogenated cottonseed oil as compared with french fries fried in partially hydrogenated canola oil and french fries fried in partially hydrogenated soybean oil. DESIGN: Cottonseed oil, partially hydrogenated canola oil, and partially hydrogenated soybean oil were subjected to a temperature of 177 degrees C for 8 hours per day, and six batches of french fries were fried per day for 5 consecutive days. French fries were weighed before frying, cooked for 5 minutes, allowed to drain, and reweighed. Oil was not replenished and was filtered once per day. Both the oil and the french fries were evaluated to determine fatty acid profiles, trans-fatty acids, and crude fat. STATISTICAL ANALYSIS: A randomized block design with split plot was used to analyze the data collected. Least-squares difference was used as the means separation test. RESULTS: No significant differences were found between fries prepared in the three oil types for crude fat. Fatty acid profiles for the french fries remained stable. The french fries prepared in cottonseed oil were significantly lower in trans-fatty acids. The combined total of the trans-fatty acid content and saturated fatty acid content were lower in french fries prepared in cottonseed oil. CONCLUSIONS: Because deep fat frying remains a popular cooking technique, health professionals should educate the public and the food service industry on the benefits of using nonhydrogenated cottonseed oil as an alternative to the commonly used hydrogenated oils.     

动植物油脂中反式脂肪酸测定方法的建立

目的建立适合国内条件的动植物油脂中反式脂肪酸测定方法,为国标方法提供依据。方法选择普通植物油、动物油和氢化植物油三个大类共9种动植物油脂样品,参照国际标准经部分修改,建立了适合国内条件的反式脂肪酸气相色谱分析及用面积归一法定量的测定方法,并进行了重复性测定和实验室间的验证。结果在实验条件下,油脂中脂肪酸可以得到很好的分离;除个别含量极低的脂肪酸外,各脂肪酸组分10次分析结果的相对标准偏差均小于10%,其中反式脂肪酸总和的RSD值在豆油和氢化豆油中分别是2.0%和0.3%;实验室间验证结果也表明,该方法在不同实验室间的结果有很好的一致性,豆油、氢化豆油、猪油三种样品的反式脂肪酸总和的RSD值分别是5.0%、1.1%和4.6%,均远小于10%。结论该检测方法实验室内和实验室间的精密度均较高,且所需仪器比较普及,操作步骤简单易行,分析时间短,适合国内开展,可作为我国动植物油脂反式脂肪酸的测定方法之一。     

Evaluation of soybean oil quality during conventional frying by FTIR and some chemical indexes

Conventional deep fat frying is a common food preparation technique in Mauritius. The deterioration of soybean oil, commonly used in conventional frying, has been studied during frying of potato chips. The oil was subjected to continuous frying at 180 degrees C for a total of 600 min. The quality changes in soybean oil were evaluated at 90 min interval by Fourier transform infrared (FTIR) spectroscopy and some routine chemical parameters, namely peroxide value, iodine value and free fatty acid. An increase in hydroperoxide and free fatty acid concentration has been observed during the frying process by FTIR technique and the chemical parameters, peroxide value and free fatty acid respectively. A significant decrease in triglyceride ester linkage was observed by FTIR. The linear decrease noted for iodine value (P < 0.01) indicated a general loss of unsaturation. Furthermore, FTIR studies showed a loss of cis double bonds along with an increase in trans unsaturation. The formation of unsaturated aldehyde has also been observed during the frying process by FTIR technique.     

Nutrient losses and gains during frying: a review

Recent consumer interest in ‘healthy eating’ has raised awareness to limit the consumption of fat and fatty foods. What are the relative nutritional advantages and disadvantages of consuming fried foods? Are all fried foods bad for you? A review on macro-and micronutrients losses and gains during frying is presented here. Frying has little or no impact on the protein or mineral content of fried food, whereas the dietary fibre content of potatoes is increased after frying due to the formation of resistant starch. Moreover, the high temperature and short transit time of the frying process cause less loss of heat labile vitamins than other types of cooking. For example, vitamin C concentrations of French fried potatoes are as high as in raw potatoes, and thiamine is well retained in fried potato products as well as in fried pork meat. The nutritive value of the frying media is also important to take into consideration and therefore losses of nutrients from the frying oil are also discussed. Although some unsaturated fatty acids and antioxidant vitamins are lost due to oxidation, fried foods are generally a good source of vitamin E. It is true that some fat is inevitably taken up by the food being fried, contributing to an increased energy density. However, this also results in highly palatable foods with a high nutritional content. It is concluded that fried foods certainly have a place in our diets.     

Intensification of essential fatty acid deficiency in the rat by dietary trans fatty acids

Two studies were conducted using male rats to assess the effect of trans fatty acids upon essential fatty acid (EFA) deficiency. In the first study 5% corn oil (CO), hydrogenated coconut oil (HCNO) or margarine stock (MS, partially hydrogenated soybean oil) were fed, and the levels of trans fatty acids in tissue lipids were measured. The trans fatty acids present in MS were found to intensify EFA deficiency and to be retained in tissue lipids to a high degree, especially in heart phospholipids (PL). In the second study, as the level of trans fatty acids increased in the diet, increasingly higher levels of trans fatty acids were deposited in the heart PL. As dietary trans acid increased, a decrease in total omega 6 fatty acids, and a decrease in the sum of 18:2 omega 6 + 20:4 omega 6 - 20:3 omega 9 fatty acids in heart PL occurred, both criteria indicating a shift toward an increasing EFA deficiency state. Studies of delta 5 desaturase activity of liver microsomes in selected groups showed an increase in the conversion of 20:3 omega 6 to 20:4 omega 6 as the trans fatty acid level in the diet increased.     

The optimization of the deep-fat frying process of coated zucchini pieces by response surface methodology

The effect of Carboxymethyl cellulose (CMC) gum in three concentrations of 0.5, 1, and 1.5% (w/v) was investigated on the oil uptake and qualitative properties (moisture content, color, and overall acceptance) of zucchini during frying at 150, 165, and 180°C for 1, 3.5, and 6 min. To determine optimum conditions of frying operation, the response surface methodology (RSM) was used. Based on the modeling performed, the lowest oil uptake (1.93%) was determined for the coated samples with concentrations of higher than 0.75% of CMC gum and fried at temperatures less than 157.5°C for 2.25 min. The optimization results of RSM showed that oil uptake of zucchini coated with CMC gum during frying is decreased significantly (p < 0.05) with the reduction of operation time and temperature, and concentration of CMC gum. Optimum conditions for decreasing oil uptake of coated zucchini pieces were 153.46°C, 0.5%, 1.03 min for temperature, concentration and time, respectively.     

Stability During Frying of Moringa oleifera Seed Oil Variety “Periyakulam 1”

The frying performance of the Moringa oleifera seed oil variety Periyakulam 1 (PKM 1) from India, extracted using cold press (CP) and n -hexane (H), during frying of potatoes and cod was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175±5°C for 5 consecutive days. The chemical changes occurring in the oils were evaluated. Free fatty acid content, peroxide value, specific extinction at 232 nm, polar compounds colour and viscosity of the oils all increased, whereas the iodine values, smoke points, polyunsaturated fatty acid content, induction period and tocopherol concentration decreased. The effect of the oils on the organoleptic quality of these fried foods was also determined by expert panellists. The analytical and sensory data showed that the lowest deterioration occurred in cold pressure produced oil and the highest in n -hexane extracted oil. Therefore, cold pressure oil appears to be the most appropriate for frying. Potatoes and cod were also fried in virgin olive oil in order to have a direct comparison between the different oils. The results clearly indicated that virgin olive oil has the highest resistance to thermal deterioration during frying compared with the other two oils.     

Application of starch-albumen powder as breading material in fried foods: An optimization study

The potential of using starch-albumen powder (SAP) as solid coating powder for fried food application was studied. Egg albumen was mixed with 10–30% dried starch and dried at 40–60°C air velocity of 4.5 m/s to produce SAP. SAP was used to coat wet yam chips prior to frying at 180°C for 3 min. The drying temperature and starch content in SAP significantly affected the oil uptake and moisture of fried chips. The increased amount of albumen (or reduced starch) content significantly reduced oil uptake. The sensory attributes influenced the overall acceptability of the fried chips in the order of taste > flavor > texture > appearance. To minimize oil uptake and moisture content and maximize acceptability of the fried chips, SAP dried at temperature of 40°C with starch content of 11.3% should be used. The study further indicates the potential of using SAP as coating in some other food products.     

Intake of trans fatty acid-rich hydrogenated fat during pregnancy and lactation inhibits the hypophagic effect of central insulin in the adult offspring

OBJECTIVE: Using rats we examined whether maternal intake of hydrogenated fat rich in trans fatty acids affects brain fatty acid profile, hypothalamic content of insulin receptor and insulin receptor substrate-1 proteins, and the hypophagic effect of centrally administered insulin in 3-mo-old male progeny. METHODS: Throughout pregnancy and lactation, Wistar rats ate isocaloric/normolipidic diets with soybean oil (control) or soybean oil-derived hydrogenated fat (trans diet) as a fat source. Upon weaning, the trans offspring continued on the trans diet (trans group) or were switched to a control diet (trans-control group). RESULTS: Compared with control rats, trans rats had lower brain levels of eicosapentaenoic acid. Compared with trans rats, trans-control rats had increased levels of total polyunsaturated fatty acids and arachidonic acid and decreased levels of trans fatty acids, saturated fatty acids, and monounsaturated fatty acids. Insulin receptor and insulin receptor substrate-1 levels were significantly lower (44% and 38%, respectively) in trans than in control rats. In trans-control rats, insulin receptor was 26% lower (P < 0.05), whereas insulin receptor substrate-1 was 50% lower, than in control rats. Insulin decreased 24-h feeding in control (27%) and trans (38%) rats but failed to do so in trans-control rats. The latter group had increased serum glucose levels. CONCLUSIONS: The data suggest that the early (intrauterine/perinatal) exposure to hydrogenated fat rich in trans fatty acids programmed the hypothalamic feeding control mechanisms. As young adults, only trans-control animals showed loss of insulin-induced hypophagia, indicating that the mismatch between early and later nutritional environments was relevant. However, the trans group also showed signs of altered appetite signaling mechanisms, suggesting that the early adaptations may have deleterious consequences later in life.     

油炸食品及其煎炸油卫生质量检测与关系探讨

目的调查油炸食品及其煎炸油卫生质量,探讨两者间卫生指标的关系。方法在广州市64个煎炸点采取油炸食品及其相应的煎炸油,按国家标准方法分别测定羰基价(CGV)、酸价(AV)、过氧化值(POV),并进行模拟实验,对不同煎炸时间的油炸食品及其煎炸油三个指标进行检测。结果油炸食品及其煎炸油的CGV及AV与油炸时间正相关(P<0.05),POV随油炸时间变化无规律(P>0.1);油炸米面制品及臭豆腐CGV显著高于与相应煎炸油CGV,且分别正相关(P<0.001)。油炸米面制品、臭豆腐及动物性食品AV显著高于与相应煎炸油AV(P<0.001),米面制品、臭豆腐的AV分别与相应煎炸油AV正相关(P<0.05)。三类油炸食品POV与相应煎炸油间POV关系无规律(P>0.1)。结论对油炸米面制品及臭豆腐等食品不仅进行AV及POV的检测,还应增加CGV的检测及限量探讨,加强对煎炸点的卫生监督及管理。     

德阳市市售植物油中反式脂肪酸含量调查

目的 了解德阳市市售植物油中反式脂肪酸的含量范围。方法 利用分层随机抽样抽取12类德阳市市售植物油共计121份样品,应用气相色谱法对样品中反式脂肪酸进行分离检测,采用归一化法进行结果计算。结果 德阳市市售植物油中12种反式脂肪酸的含量范围为未检出至3.19%,以反式亚麻酸（C18:3T）为主,其中橄榄油未检测出反式脂肪酸,最常见的菜籽油、玉米油、调和油、大豆油的反式脂肪酸平均含量分别为1.64%、2.20%、1.75%、2.58%。结论 德阳市市售植物油中普遍存在反式脂肪酸且含量各不相同。     

Effect of hydrogenated fat on the plasma cholesterol and triglyceride levels of man.

A group of 33 adult males was fed for 21 days a formula diet that supplied 38 per cent of their calories as fat. The fatty acid composition of the diet was 25 per cent saturates, 16 per cent polyunsaturates and 58 per cent monounsaturates. All of the unsaturated acids were in the cis configuration. The subjects were then divided into two groups. One group of 17 men continued on the same diet. In the diet of the remaining subjects, 80 per cent of the dietary fat was replaced with a hydrogenated fat. Over 60 per cent of the monounstaurated acids and approximately one-half of the polyunsaturated acids of the diet of this latter group were in the trans configuration. Except for the presence or absence of trans acids, the fatty acid intakes of the two groups were the same. Over the 4-week period that the two diets were consumed, the group receiving the hydrogenated fat showed no change in plasma cholesterol or triglyceride levels relative to the subjects consuming the unhydrogenated fat. It is concluded that the effect of a hydrogenated fat on blood lipid level is determined by its fatty acid composition and this effect is not altered by the isomeric form of the unsaturated acids.     

New and existing oils and fats used in products with reduced trans-fatty acid content

The US Food and Drug Administration's final ruling on trans-fatty acid labeling issued in 2003 has caused a rapid transformation in the fat and oil industries. Novel ingredients and improved technologies are emerging to replace partially hydrogenated fats in foods. We present an overview of the structure and formation of trans fatty acids in foods, and a comprehensive review of the newly formulated products and current procedures practiced by the edible oil industry to reduce or eliminate trans fatty acids in response to the Food and Drug Administration's regulations mandating trans fat labeling of foods.     

Palm oil versus hydrogenated soybean oil: effects on serum lipids and plasma haemostatic variables

The purpose of this study was to test if replacement of trans fatty acids by palmitic acid in an experimental margarine results in unfavourable effects on serum lipids and haemostatic factors. We have compared the effects of three different margarines, one based on palm oil (PALM-margarine), one based on partially hydrogenated soybean oil (TRANS- margarine) and one with a high content of polyunsaturated fatty acids (PUFA-margarine), on serum lipids in 27 young women. In nine of the participants fasting levels and diurnal postprandial levels of haemostatic variables on the 3 diets were compared. The sum of 12:0, 14:0, 16:0 provided 11% of energy (E%) in the PALM diet, the same as the sum of 12:0, 14:0, 16:0 and trans fatty acids in the TRANS-diet. Oleic acid provided 10-11E% in all three diets, while PUFA provided 5.7, 5.5 and 10.2 E%, respectively. Total fat provided 30-31% and the test margarines 26% of total energy in all three diets. Each of the diets was consumed for 17 days in a crossover design. There were no significant differences in total cholesterol, LDL-cholesterol and apoB between the TRANS- and the PALM-diet. HDL-cholesterol and apoA-I were significantly higher on the PALM-diet compared to the TRANS-diet while the ratio of LDL- to HDL-cholesterol was lower, although not significantly (P = 0.077) on the PALM-diet. Total cholesterol, LDL-cholesterol and apoB were significantly lower on the PUFA-diet compared to the two other diets. HDL-cholesterol was not different on the PALM- and the PUFA-diet while it was significantly lower on the TRANS-diet compared to the PUFA-diet. Triglycerides and Lp(a) were not different among the three diets. The diurnal postprandial state level of tissue plasminogen activator (t-PA) activity was significantly decreased on the TRANS-diet compared to the PALM-diet. t-PA activity was also decreased on the PUFA-diet compared to PALM-diet although not significantly (P=0.07). There were no significant differences in neither fasting levels or in circadian variation of t-PA antigen, PAI-1 activity, PAI-1 antigen, factor VII coagulant activity or fibrinogen between the three diets. Our results suggest that dietary palm oil may have a more favourable effect on the fibrinolytic system compared to partially hydrogenated soybean oil. We conclude that from a nutritional point of view, palmitic acid from palm oil may be a reasonable alternative to trans fatty acids from partially hydrogenated soybean oil in margarine if the aim is to avoid trans fatty acids. A palm oil based margarine is, however, less favourable than one based on a more polyunsaturated vegetable oil.     

Fatty acids and retinyl esters of rat milk: effects of diet and duration of lactation

This study was initiated to explore the quantitative and qualitative differences in milk total fatty acids and milk retinyl esters when either hydrogenated or nonhydrogenated fat is fed during pregnancy and lactation. Rats were fed diets containing 10% by weight of corn oil or partially hydrogenated corn oil. Milk was collected on d 1, 8 and 14 of lactation and analyzed for protein, total fatty acids, fatty acid pattern, and retinyl ester pattern. Whereas diet produced no quantitative differences in milk protein or total fatty acids, the pattern of milk fatty acids varied significantly. Rats fed corn oil produced milk having more medium-chain saturated fatty acids, less long-chain monoenoic fatty acids, and more polyunsaturated fatty acids compared to those fed hydrogenated corn oil. Rats fed hydrogenated corn oil produced milk fat having 21-26% of the trans fatty acid, elaidic acid. Significant differences were also observed with duration of lactation: medium-chain fatty acids increased three to fourfold between d 1 and 8, where cis-monoenes and polyunsaturated fatty acids declined. The pattern of milk retinyl esters strongly reflected, but was not identical to, that of total milk fat. Comparing d 14 milk from rats fed corn oil with that from rats fed hydrogenated corn oil, medium-chain esters of retinol constituted 24 and 11% of total retinyl esters, whereas saturated long-chain fatty acid esters constituted 52 and 44%, respectively. trans Fatty acid esters of retinol comprised 24% of vitamin A esters in milk of rats fed hydrogenated fat. These data provide evidence that the composition of milk retinyl esters, as well as that of total milk fat, is determined both by the type of fatty acids from diet and from diet-related differences in de novo synthesis of fatty acids within the mammary gland and other tissues.     

Acute postprandial effect of hydrogenated fish oil, palm oil and lard on plasma cholesterol, triacylglycerol and non-esterified fatty acid metabolism in normocholesterolaemic males

The majority of research has focused on the association between trans unsaturated fatty acids (TUFA) from hydrogenated vegetable oils and heart disease even though TUFA are also produced from hydrogenated fish oil. We compared the acute effect of three solid fats on postprandial cholesterol, triacylglycerol (TAG) and NEFA concentrations in normocholesterolaemic males. Eight healthy male volunteers consumed each of the three 40 g fat meals (partially hydrogenated fish oil (PHFO), palm oil and lard) in random order and blood samples were drawn at 2, 4, 6 and 8 h thereafter for lipid analysis. The postprandial response in plasma TAG, TAG-rich lipoprotein-TAG (TRL-TAG), total cholesterol and plasma NEFA, measured as the area under the postprandial curve, was not significantly different between the three meals (P>0.05), which varied in MUFA, PUFA and TUFA content. There was no marked elevation of longer-chain fatty acids (C20-22, cis or trans isomers) into the TRL-TAG fraction following the PHFO meal even though they provided 40 % of the total fatty acids in the PHFO meal. The postprandial TRL-TAG response to PHFO was expected to be higher, as it is higher in TUFA, lower in PUFA and similar in saturated fatty acid composition compared with the lard and palm oil test meals. The absence of a higher postprandial response following ingestion of PHFO could be as a result of reduced absorption and increased oxidation of long-chain fatty acids (both cis and trans isomers).     

Mutagenic activity of heated potato/oil systems

Mutagens detected with Salmonella typhimurium strain TA 98 in the presence of liver S9 mix were extracted from potato slices, but not pure potato starch, after frying in oil. No mutagenic activity was detected using strain TA 100, in the presence or absence of S9 mix with either fried potato slices or potato starch. Mutagenic activity was detected at frying temperatures of 140°C and above. The mutagenic activity was limited to the outer portion of the fried potato slices and increased with frying time and temperature. Mutagenic activity ratios for extraction with both (NH4)2SO4/ NH4 OH and Na2 SO4 /NaOH were similar.