Effect of lecithins partly replacing rumen‐protected fat on fatty acid digestion and composition of cow milk

The effects on fatty acid digestibility and milk fat composition of calcium soaps of palm oil fatty acids and of a 25% replacement of the Ca soaps by four different lecithins (raw, deoiled and deoiled/partially hydrolysed soy lecithin, raw canola lecithin) and soybean oil were investigated in six lactating cows each. The complete diets contained the lipid supplements at proportions of 30 g fatty acids/kg dry matter. Partial replacement of Ca soaps by soy or canola lecithins and soybean oil had small but significant effects on fatty acid digestion and utilisation, as well as the fatty acid profile in milk. Relative to Ca soaps alone, C 16:0 digestibility was slightly higher with lecithins, and percentage of conjugated linoleic acid and trans C 18:1 in milk fat increased while proportion of C 16:0 decreased. Deoiling of lecithins slightly reduced the effects on C 16:0 digestibility and excretion with milk. The influence of lecithin processing was higher than the differences between raw soy and raw canola lecithin. Nevertheless, most of the few effects observed may be related to the fatty acids supplied with the lecithins but, regarding C 18:1 trans‐11 and odd chain fatty acids, there is some evidence that lecithins impair rumen microbial activity less than soybean oil.     

Fatty acid and conjugated linoleic acid isomer profiles in human milk fat

The fatty acid composition of 39 mature human milk samples from four Spanish women collected between 2 and 18 weeks during lactation was studied by gas chromatography. The conjugated linoleic acid (CLA) isomer profile was also determined by silver‐ion HPLC (Ag⁺‐HPLC) with three columns in series. The major fatty acid fraction in milk lipids throughout lactation was represented by the monounsaturated fatty acids, with oleic acid being the predominant compound (36–49% of total fatty acids). The saturated fatty acid fraction represented more than 35% of the total fatty acids, and polyunsaturated fatty acids ranged on average between 10 and 13%. Mean values of total CLA varied from 0.12 to 0.15% of total fatty acids. The complex mixture of CLA isomers was separated by Ag⁺‐HPLC. Rumenic acid (RA, cis‐9 trans‐11 C18:2) was the major isomer, representing more than 60% of total CLA. Trans‐9 trans‐11 and 7‐9 (cis‐trans + trans‐cis) C18:2 were the main CLA isomers after RA. Very small amounts of 8‐10 and 10‐12 C18:2 (cis‐trans + trans‐cis) isomers were detected, as were different proportions of cis‐11 trans‐13 and trans‐11 cis‐13 C18:2. Although most of the isomers were present in all samples, their concentrations varied considerably.     

The fatty acid composition of small and large naturally occurring milk fat globules

Native milk fat globules of various mean diameters, ranging from d₄₃ = 1.5 to 7.3 μm, were obtained using microfiltration of raw whole milk acquired in winter and spring. After total lipid extraction, fatty acid composition was characterized by methyl and butyl ester analysis using gas chromatography. The oleic and linoleic acid content of milk obtained in winter increased with fat globule size, whereas myristic and palmitic acid decreased. There was significantly more lauric, myristic and palmitoleic acid, and less stearic acid in small fat globules compared to large fat globules in milk obtained in both winter and spring. The relative content of oleic and linoleic acids were found to depend on fat globule size and season. Results are interpreted on the basis of the relative content of milk fat globule membrane depending on fat globule size, and on consequences of compositional variations on milk fat globule melting behavior.     

Differently sized native milk fat globules separated by microfiltration: fatty acid composition of the milk fat globule membrane and triglyceride core

The aim of this study was to characterize the fatty acid composition of the core and membrane of differently sized milk fat globules separated by microfiltration, which can now be used to manufacture dairy products. Native milk fat globules of various mean diameters, ranging from d₄₃ = 2.3 µm to 8.0 µm, were obtained using microfiltration of raw whole milk. After milk fat globule washing, the milk fat globule membrane (MFGM) and the triglyceride core (TC) were separated by manual churning. After total lipid extraction from each fraction, their fatty acid composition was characterized using methyl ester analysis by gas chromatography. Regardless of season, no significant differences were observed in the fatty acid composition of the MFGM phospholipids. Conversely, significant differences were found in the fatty acid composition of TC; particularly, small fat globule TC contained more medium‐chain fatty acids and less stearic acid than large fat globule TC. These results show that the previously observed differences in total fatty acid composition among differently sized milk fat globules are due to their triglyceride composition and MFGM amount rather than to the composition of the MFGM.     

Triglyceride composition of ewe,cow, and goat milk fat

The separation and identification of the components in milk fat, which are mainly triglycerides, is a challenge due to its complex composition. A reverse-phase high-performance liquid chromatography (HPLC) method with gradient elution and light-scattering detection is described in this paper for the triglyceride analysis in ewes’ milk fat. Triglyceride identification was carried out by combining HPLC, gas-liquid chromatography (GLC), and the calculated equivalent carbon numbers of several triglyceride standards. Quantitation of partially resolved peaks in the HPLC chromatogram was accomplished by applying a peak deconvolution program. Forty-four fatty acids were identified by GLC analysis, but only 19 were used for the following prediction of triglyceride molecular species; 181 triglycerides were identified, some of which were grouped at the same peak and needed application of the deconvolution program. Consequently, coefficients of variation were close to or lower than 5%. Moreover, the triglyceride composition of ewe, cow, and goat milk fat were compared by using these methods. These results show that ewe milk fat is richer in short- and medium-chain triglycerides, and cow milk fat is richer in long-chain and unsaturated triglycerides.     

Dietary trans α‐linolenic acid does not inhibit Δ5‐ and Δ6‐desaturation of linoleic acid in man

Dietary trans monoenes have been associated with an increased risk of heart disease in some studies and this has caused much concern. Trans polyenes are also present in the diet, for example, trans α‐linolenic acid is formed during the deodorisation of α‐linolenic acid‐rich oils such as rapeseed oil. One would expect the intake of trans α‐linolenic acid to be on the increase since the consumption of rapeseed oil in the western diet is increasing. There are no data on trans α‐linolenic acid consumption and its effects. We therefore carried out a comprehensive study to examine whether trans isomers of this polyunsaturated fatty acid increased the risk of coronary heart disease. Since inhibition of Δ6‐desaturase had also been linked to heart disease, the effect of trans α‐linolenic acid on the conversion of [U‐¹³C]‐labelled linoleic acid to dihomo‐γ‐linolenic and arachidonic acid was studied in 7 healthy men recruited from the staff and students of the University of Edinburgh. Thirty percent of the habitual fat was replaced using a trans ‘free’‐ or ‘high’ trans α‐linolenic acid fat. After at least 6 weeks on the experimental diets, the men received 3‐oleyl, 1,2‐[U‐¹³C]‐linoleyl glycerol (15 mg twice daily for ten days). The fatty acid composition of plasma phospholipids and the incorporation of ¹³C‐label into n‐6 fatty acids were determined at day 8, 9 and 10 and after a 6‐week washout period by gas chromatography‐combustion‐isotope ratio mass spectrometry. Trans α‐linolenic acid of plasma phospholipids increased from 0.04 ? 0.01 to 0.17 ? 0.02 and cis ? ‐linolenic acid decreased from 0.42 ? 0.07 to 0.29 ? 0.08 g/100 g of fatty acids on the high trans diet. The composition of the other plasma phospholipid fatty acids did not change. The enrichment of phosphatidyl ¹³C‐linoleic acid reached a plateau at day 10 and the average of the last 3 days did not differ between the low and high trans period. Both dihomo‐γ‐linolenic and arachidonic acid in phospholipids were enriched in ¹³C, both in absolute and relative terms (with respect to ¹³C‐linoleic acid). The enrichment was slightly and significantly higher during the high trans period (P<0.05). Our data suggest that a diet rich in trans α‐linolenic acid (0.6% of energy) does not inhibit the conversion of linoleic acid to dihomo‐γ‐linolenic and arachidonic acid in healthy middle‐aged men consuming a diet rich in linoleic acid.     

The fatty acid composition of lipids from muscle and adipose tissues of pigs fed various oil mixtures differing in their ratio between oleic acid and linoleic acid

High concentrations of polyunsaturated fatty acids (PUFA) in meat have detrimental effects on its technical properties. The present study was carried out to investigate whether PUFA levels in pork can be reduced by increasing the concentrations of oleic acid in pig diets. To this end a bifactorial experiment was carried out with 48 female growing finishing pigs. Six different diets were used with two different concentrations of linoleic acid (12 vs. 24 g/kg) and three different concentrations of oleic acid (12 vs. 18 vs. 24 g/kg). The experiment started at a body weight (BW) of 58 kg and continued until 115 kg BW. The fatty acid composition of total lipids of backfat, perirenal fat and musculus (m.) longissimus dorsi was analysed. Concentrations of linoleic acid and total PUFA in backfat and perirenal fat were affected only by the dietary linoleic acid content but not at all by the dietary oleic acid content. Increasing the dietary concentration of oleic acid raised the level of oleic acid in those tissues at the expense of saturated fatty acids, suggesting competition between monounsaturated fatty acids and saturated fatty acids for incorporation into triglycerides. At the low dietary linoleic acid concentration, the percentages of linoleic acid and total PUFA in total lipids of m. longissimus dorsi were also unaffected by the dietary oleic acid content. In contrast, at the high dietary linoleic acid concentration, percentages of linoleic acid and total PUFA of the m. longissimus dorsi were reduced by increasing the dietary concentration of oleic acid, suggesting that oleic acid and linoleic acid compete for incorporation into muscle lipids. Thus, at high dietary linoleic acid levels the fatty acid composition of the m. longissimus dorsi was favourably affected by high dietary oleic acid concentrations; in backfat and perirenal fat, however, no beneficial effect of high dietary oleic acid levels was seen.     

Thermal analysis of palm mid-fraction,cocoa butter and milk fat blends by differential scanning calorimetry

Commercial samples of anhydrous milk fat (AMF), Ivory Coast cocoa butter (CB) and palm mid-fraction (PMF) were blended in a ternary system. The melting characteristics of the blends were studied by differential scanning calorimetry (DSC). Results suggest that in the studies of interaction involving more than two fats, partial area (A_i) under the melting peak should be converted to partial enthalpy (ΔH_i) rather than to solid fat index. The ΔH values of the blends decreased as the amount of AMF was increased and increased as the amount of CB was increased. In general, the effect of PMF was less pronounced compared to the effect of the other two fats. Eutectic effects within the ternary system could be detected by measuring the deviation of melting enthalpy by DSC, and from the corresponding values that were calculated for the thermodynamically ideal blends. The deviation reached a maximum when the amount of AMF was about 33%. On the binary line of CB/PMF, the eutectic effect was maximum at about 50–75% PMF. The interaction effect in the system was more noticeable at 30 and 20°C than at lower temperatures. Evaluation at 30°C was preferred because both the effect of AMF in the ternary system and the effect of PMF on the binary line were more readily observed.     

Effects of milk fat replacement by PUFA enriched fats on n‐3 fatty acids,conjugated dienes and volatile compounds of fermented milks

A study was carried out to determine the profiles of fatty acids in fermented milks and dairy derivatives made with milk fat substituted by polyunsaturated fatty acid (PUFA)‐enriched fat. In order to improve the organoleptic properties of those products, whey protein concentrates (WPC) were added during the manufacturing process. Interest was focused during manufacturing and storage period on the contents of “healthy” fatty acids, mainly conjugated linoleic acid and n‐3 PUFA. Contents of these fatty acids were not affected by the manufacture practices and neither did addition of WPC during manufacturing nor cold storage cause their decrease. Percentages of total n‐3 fatty acids in fat from dairy derivatives enriched in PUFA after 21 d of storage (1.45%) were very close to those obtained before processing (1.39%). Contents did not differ either substantially when WPC were added during manufacturing (1.46%). The increase of volatile compounds was also examined. Although a slight decrease in the total volatile content was observed, percentages of different compounds were not modified when milk fat was substituted by PUFA enriched fat.     

Determination of milk fat in chocolates by gas-liquid chromatography of triglycerides and fatty acids

The combination of two routine methods is proposed to determine the content of milk fat (MF) in chocolates, which is applicable even in the presence of lauric fats or others. The content of MF is obtained from the sum of C₄₀, C₄₂, and C₄₄ medium-chain triglycerides, determined by capillary gas-liquid chromatography (GLC). A new method, based on methyl esters of lauric acid and on minor acids situated between myristic and palmitic, is proposed. It enables detection and estimation of potential lauric fats, as well as the determination of the actual content of MF. The influence of other vegetable and animal fats is discussed. We analyzed 45 MF samples extracted from industrial milk powders and from pure or fractionated MF for chocolate manufacturing or pastry by GLC of triglycerides. We also analyzed by capillary GLC the methyl esters from 22 of those fats. Mixtures of these 22 MF samples with a cocoa butter also were used for chromatographic analyses of methyl esters and triglyceride. Results from the various analytical methods have been presented.     

Effects of conjugated linoleic acids on protein to fat proportions,fatty acids,and plasma lipids in broilers

In a performance trial, broiler chickens received 29 g per kg feed of a preparation containing 70% linoleic acid (LA) in the control treatment and another preparation containing approximately the same amount of conjugated linoleic acids (CLA) in the experimental treatment. Diets of CLA treatment contained 18 g CLA per kg feed. The CLA preparation contained the isomers cis‐9,trans‐11 and trans‐10,cis‐12 at a proportion 1:1, other CLA isomers were quantitively negligible. Performance parameters (weight gain and feed conversion ratio over a 42 day period) were not significantly influenced by CLA intake. However, fat content of liver, breast, and leg muscles was reduced and protein contents in liver and leg muscles were elevated significantly. Fat to protein ratios in the main edible parts were shifted in favour of protein in CLA treated animals. In all analysed tissue lipids the content of saturated fatty acids was increased and that of monounsaturated fatty acids was decreased significantly. At the same time CLA was incorporated in tissue lipids effectively reaching more than 10 g per 100 g of total fatty acids. With regard to isomers the cis‐9,trans‐11 isomer was found in higher concentrations in tissue lipid fractions compared to the trans‐10,cis‐12 isomer. It was concluded that nutrient repartitioning due to CLA intake described for other species is also valid for broilers. Using appropriate feeding strategies it is possible to produce CLA enriched food from broilers.     

Analysis of conjugated linoleic acid isomers and content in french cheeses

Conjugated linoleic acid (CLA) occurs in food as a result of microbial enzymatic reactions, free radical-type oxidation, and heat treatment. CLA is found in animal products, such as meat and dairy products, especially in cheeses. The CLA composition of 12 different French cheeses was determined by a combination of different analytical methods: reversed-phase high-performance liquid chromatography (RP-HPLC), gas chromatography-mass spectrometry (GC-MS), GC-Fourier transform infrared (GC-FTIR), and silver nitrate thin-layer chromatography (AgNO₃-TLC). New isomers (Δ8,10- and Δ11,13-octadecadienoic acids with all possible cis and trans configurations) that co-eluted with previously identified isomers (Δ9c,11t-; Δ9t,11c-; Δ10c,12t-; Δ10t,12c-; Δ11c,13c-; Δ9c,11c-; Δ10c,12c-; Δ9t,11t-; Δ10t12t-octadecadienoic acids) were detected. Δ9c,11t-Octadecadienoic acid was the major CLA isomer in these cheeses. All isomers were present in each product, whatever the production process. However, CLA content in the cheeses varied from 5.3 to 15.80 mg/g of cheese fat, which depended primarily on the origin of the milk (season, geography) and somewhat on the production process.     

Effects of minor lipids on crystallization of milk fat-cocoa butter blends and bloom formation in chocolate

Minor lipids, such as diacylglycerols, monoacylglycerols, cholesterol, and phospholipids play a key role in crystallization of fats. In this study, the effects of minor lipid components on crystallization of blends of cocoa butter (CB) with 10% milk fat or milk-fat fractions, and on bloom formation of chocolate were investigated. Both removing the minor lipids from milk fat and doubling the level of minor lipids from milk fat resulted in longer nucleation onset time, slower crystallization rate, and rapid bloom development in chocolate. Removal of minor lipids resulted in the formation of irregular primary and secondary crystals with inclusions of liquid fat, whereas the crystals were spherical and uniform in shape in the presence of minor lipids. Minor lipids from milk fat, even at the low concentrations typically found in nature, affected the crystallization of milk fat-CB blends, impacted the chocolate microstructure, and affected bloom development in chocolate.     

Effect of grass vs. concentrate feeding on the fatty acid profile of different fat depots in lambs

The aim of this study was to produce high‐quality meat from lambs under different feeding conditions, as measured by the accumulation of n‐3 fatty acids and conjugated linoleic acids (CLA) in muscle and subcutaneous fat. In total, 13 male crossbred lambs (Black Head×Gotland), each at 24 kg live weight, were divided into two feeding groups. Lambs were kept either on pasture (pasture grazing, n = 6) or in the stable (concentrate feeding, n = 7). The linolenic acid (C18:3n‐3) contained in the grass was absorbed and deposited into the different lipid classes of muscle and subcutaneous fat. The proportion of total n‐3 fatty acids in the different lipids of grazing lambs was significantly (p = 0.05) higher compared to that in concentrate‐fed lambs. The n‐6/n‐3 ratio (mean ± SEM) in muscle of grazing lambs was 1.2 ± 0.09 in contrast to 2.3 ± 0.09 (p = 0.05) of the animals kept in the stable. In subcutaneous fat, this ratio was 0.9 ± 0.2 in lambs kept on pasture versus 3.5 ± 0.2 (p = 0.05) after indoor keeping. The relative concentration of C18:1trans‐11 in total muscle lipids, phospholipids, triacylglycerols and subcutaneous fat was significantly increased by grass feeding compared to concentrate feeding. Significant influences of feeding were shown for saturated fatty acids. In concentrate‐fed lambs, a lower content of saturated fatty acids was detected. The proportion of CLAcis‐9,trans‐11 (1.9 ± 0.2% vs. 1.1 ± 0.1% in muscle, 2.5 ± 0.2% vs. 1.4 ± 0.2% in subcutaneous fat, 0.7 ± 0.04% vs. 0.4 ± 0.04% in phospholipids) in lambs was significantly (p = 0.05) higher after grazing than after concentrate feeding, respectively.     

Melting and solidification characteristics of confectionery fats: Anhydrous milk fat,cocoa butter and palm kernel stearin blends

Differential scanning calorimetry measurements of crystallization and melting characteristics of commercial samples of anhydrous milk fat (AMF), cocoa butter (CB) and hydrogenated palm kernel stearin (PKS) in ternary blends were studied. Results showed that stabilization at 26°C (either for 40 h or 7 d) did not greatly affect the melting thermogram trace of PKS. However, the effect of stabilization became prominent as CB was added into the system. Deviation of measured enthalpy from the corresponding values, calculated for thermodynamically ideal blends, showed clear interaction between all three fats. At 20°C, the strongest deviation occurred at about the AMF/CB/PKS (1∶1∶1) blend, whereas at 30°C the deviation moved toward the CB/MF (1∶1) blend. The presence of 25% AMF in PKS had little effect on its solidification capability, but solidification was adversely affected with inclusion of CB.     

N‐3 fatty acids and conjugated linoleic acids of longissimus muscle in beef cattle

The objective of the experiment with cattle was to produce high quality beef under different feeding conditions and to increase the concentration of essential fatty acids in muscle. In total 10 German Simmental (GS) bulls and 9 German Holstein (GH) steers were kept either on pasture (grass feeding) or in stable (concentrate feeding). Despite biohydrogenation in the rumen, linolenic acid (C18:3n‐3) contained in grass was absorbed and deposited into the lipids of muscle. This led to a significantly (p ≤ 0.05) higher content of n‐3 fatty acids in the muscle lipids of grazing cattle. The relative amount of total n‐3 fatty acids increased from 1.4 g/100 g fatty acid methyl ester (%FAME) in the intensively fed Simmental bulls to 5.5 %FAME in grass fed cattle. The n‐6/n‐3 ratio of pasture grazing GS bulls was 1.3 in contrast to 13.7 of the animals kept in the byre. The total n‐3 fatty acid concentration in beef muscle increased from 24.6 mg (concentrate) to 108.6 mg/100 g wet weight (grazing). In GH steers the total n‐3 fatty acid concentration was significantly (p ≤ 0.05) increased up to 86.3 mg/100 g wet weight in pasture grazing steers compared to 28.8 mg/100 g wet weight in animals fed the concentrate. The relative content (%FAME) of CLAcis‐9, trans‐11 (0.6 vs 0.56 %FAME in GS; 0.55 vs 0.52 %FAME in GH) in muscle was not significantly increased by grazing on pasture in comparison to concentrate feeding neither in GS bulls nor in GH steers, respectively.     

The impact of fatty acid profile on the physicochemical properties of commercial margarines in Brazil

This study aimed to evaluate how lipid profiles affect the physicochemical properties, fatty acid profiles, and nutritional qualities of Brazilian margarines. We analyzed the texture profiles of 13 margarine samples and characterized their fatty acid composition, solid fat content, crystallization kinetics by NMR and thermal behavior by differential scanning calorimetry. The samples had total fat content ranging from 20% to 82% and low trans fatty acid (TFA) levels, except for two samples (5–7% elaidic acid). The fatty acid compositions of all samples showed a predominance of linoleic (23%–46%), oleic (20%–46%), and palmitic acids (7%–14%), indicating that they were formulated with soybean and palm oils. Saturated fat content ranged from 23% to 31%. Compared to the other evaluated samples, those with higher content of lipid and saturated fatty acids (SFAs) exhibited increased hardness and stickiness but reduced spreadability and adhesiveness. The presence of TFAs resulted in increased plasticity of the samples. Reformulation resulted in products with greater SFA levels, which had a negative impact as it increased the atherogenic index (AI: 0.22–0.48). The HF55 sample contained canola oil-based fat and presented the best nutritional and physical properties. This study is the first to report a complete evaluation of representative margarines, with essential information in reformulating to achieve lower SFA.     

Geometrical isomerisation of double bonds in acid‐catalysed preparation of fatty acid methyl esters

Acid‐catalysed methylation is frequently applied for the preparation of fatty acid methyl esters used for gas chromatographic analysis of fatty acids. A series of artefacts were observed in hydrochloric acid‐catalysed direct methylation of herring (Clupea harengus L.) muscle. The artefacts were identified as trans isomers of eicosapentaenoic and docosahexaenoic acid, and their levels increased with reaction time. The isomers were not found after methylation of a lipid extract of the herring muscle, even after extreme reaction times. In general, the trans isomers are only observed after methylation of certain marine tissues, indicating catalytic activity in these samples. Based on these results, it is recommended that direct methylation procedures are thoroughly validated with each matrix type analysed, and that reaction times should not be longer than necessary to complete the methylation.     

Long‐term conjugated linoleic acid supplementation in humans – effects on body composition and safety

In our contemporary adipogenic environment even modest improvements in body fat mass could be of relevance. In the last years animal and human studies have investigated the potential benefit of CLA on body composition. However, inconclusive results are often derived from short‐term studies. Long‐term intervention trials with supplemental CLA on body composition have not been reviewed exclusively up to now. Therefore, the objective of this study was to review the evidence of prolonged CLA supplementation as well as its influence on body composition in humans, and to summarize results from safety assessments of CLA intake. A literature search was performed to find intervention trials with CLA supplementation and its effects on body composition, as well as on insulin sensitivity. Only prolonged (≥12 wk) studies on body composition were included. The investigated studies indicate a modest reduction and/or prevention of regain of body fat in overweight/obese subjects. Results on the influence of CLA on insulin sensitivity are inconsistent, with newer data rather adding to the safety of CLA. Impaired insulin sensitivity by CLA remains a safety concern, yet is seemingly restricted to diabetic subjects and single‐isomer application. A meta‐a2 lysis of extended studies only is warranted to quantitatively evaluate the effects of CLA on body composition. Future research may elucidate if CLA should be considered as a marginal missing, semi‐essential nutrient in our present diet.