Quantitativer Nachweis von Milchfett in Schokoladenmischungen I: Bestimmung von Milchfettanteilen in Kakaobutter

Quantitative Detection of Milk Fat in Chocolate Mixtures I: Determination of Milk Fat in Cocoa Butter New methods for the quantitative determination of milk fat proportions in cocoa butter samples based on gas chromatographic analysis of fatty acids and triglycerides are described. 45 different cocoa butter types from 25 countries and 755 milk fat samples were analyzed by taking different feeding conditions into account. By means of triglyceride measurements mean relative deviations of approximately 5% from the 2–10% milk fat additions were established for known cocoa butter- and unknown milk fat composition. With completely unknown initial fats a mean relative deviation of approximately 6% was measured using fatty acid analysis.     

Extraktion von Milchfett mit überkritischem Kohlendioxid

Extraction of Milk Fat with Supercritical Carbon Dioxide In parallel with fractionation based on crystallization, studies have been made in recent years on milk fat fractionation with supercritical carbon dioxide. This means that the fat is chiefly extracted on the basis of molecular size. The extraction experiments were carried out using a pilot plant extraction apparatus. The milk fat was extracted in 4 or 2 stages. The melting properties of extracts are explained by the compositions of fatty acids and triacylglycerols. The percentages of short chain fatty acids C4–C10 becomes smaller as the extractio proceeds. The percentage of palmitic acid remains virtually unchanged at all stages of the extraction. The percentages of C 18 fatty acids, stearic and oleic acids increase as the extraction proceeds. Cholesterol and aroma compounds of milk fat were clearly enriched in the first extract. Supercritical extraction opens up some new potential for milk fat technology and for the food industry using milk fat. At this stage it wold seem especially interesting to study the possible uses of extracts rich in aroma.     

Effects of protected cyclopropene fatty acids on the composition of ruminant milk fat

Unsaturated fatty acids can be protected from ruminal hydrogenation, and, when fed to lactating ruminants, the constituent acids are incorporated into milk triacylglycerols. By this means, it has been possible to reduce the melting point of milk triglycerides and to make softer butter fat. This report shows that, by feeding small amounts of protected cyclopropene fatty acids, one is also able to make harder butter fat.Sterculia foetida seed oil, a rich source of cyclopropene fatty acids, was emulsified with casein and spray dried to yield a free flowing dry powder. When this material was treated with formaldehyde and fed to lactating goats (ca. 1 g cyclopropene fatty acids per day), there were substantial increases in the proportions of stearic acid and decreases in the proportions of oleic acid in milk fat. Similar results were obtained when the formaldehyde-treated supplements were fed to lactating cows (ca. 3 g cyclopropene fatty acids per day). The effect was considerably less apparent when theS. foetida seed oilcasein supplement was not treated with formaldehyde, suggesting that cyclopropene fatty acids are hydrogenated in the rumen as are other unsaturated fatty acids. The effect of feeding protected cyclopropene fatty acids on the stearic: oleic ratio in milk fat is probably due to cyclopropene-mediated inhibition of the mammary desaturase enzymes.     

Der Nährwert verschiedener Milchfett-Fraktionen

Nutritional Value of Various Fractions of Milk Fat Milk fat was fractionated in four fractions having different melting ranges. The liquid fractions contained predominantly short chain saturated and unsaturated fatty acids whereas the solid fractions contained mainly palmitic and stearic acids. Vitamins were mostly enriched in the liquid fractions. Experiments in which albino rats were fed with the milk-fat-fractions revealed that the iodine values and the fatty acid composition of the depot fats of these animals were dependent on the feed. Histopathological examination of the heart, kidney and liver showed no alterations caused by feeding.     

Milk fat globules: Fatty acid composition,size and in vivo regulation of fat liquidity

Populations of large and small milk fat globules were isolated and analyzed to determine differences in fatty acid composition. Globule samples were obtained by centrifugation from milks of a herd and of individual animals produced under both pasture and barn feeding. Triacylglycerols of total globule lipids were prepared by thin layer chromatography and analyzed for fatty acid composition by gas chromatography. Using content of the acids in large globules as 100%, small globules contained fewer short-chain acids, −5.9%, less stearic acid, −22.7%, and more oleic acids, +4.6%, mean values for five trials. These differences are consistent with alternative use of short-chain acids or oleic acid converted from stearic acid to maintain liquidity at body temperature of milk fat globules and their precursors, intracellular lipid droplets. Stearyl-CoA desaturase (EC 1.14.99.5), which maintains fluidity of cellular endoplasmic reticulum membrane, is suggested to play a key role in regulating globule fat liquidity. Possible origins of differences between individual globules in fatty acid composition of their triacylglycerols are discussed.     

Quantitativer Nachweis von Milchfett in Schokoladenmischungen II: Bestimmung von Milchfettanteilen in Schokolade

Quantitative Detection of Milk Fat in Chocolate Mixtures II: Determination of Milk Fat in Chocolate Using gas chromatographic fatty acid analysis proportions of 4–12% milk fat additions varying in composition were quantitatively detected in different chocolate fats. Independent of the type of chocolate best recovery with mean absolute deviations of 0.64 and 0.68% was obtained using the fatty acid C4 and the combination C4–C6. Compared to milk chocolate most precise detection was achieved for milk fat additions to bitter chocolate. Here differences of 0.39%, on average, were observed between experimentally added and theoretically computed proportions. Unlike hazelnut or almond oil, coconut or palm kernel oil present in chocolate fats can hamper the measurements. Capillary column gas chromatography of the triglycerides allows sensitive indications of the presence of such vegetable fats in a chocolate mixture to be obtained.     

Über die physikalischen und chemischen Eigenschaften der Milchfettfraktionen

Physical and Chemical Characteristics of Milk Fat Fraction Milk fat is a mixture of many different triglycerides, and its crystallization characteristics offer good possibilities for fat fractionation. In principle, this can be done in several differnt ways. In our studies milk fat was mostly divided into two or more fractions through crystallization and separation as the temperature was gradually lowered. Fractionation was carried out without solvents or additives. The solidification and melting characteristics of the fractions obtained, as well as their fatty acid and triglyceride composition, differed considerably from each other and from the corresponding characteristics of the original milk fat. By combining different milk fat fractions, the melting characteristics of fat can be led in the desired direction, making it possible to created fat mixtures suitable for a variety of special applications. Is 1987 we have carried out soem experiments for the fractionation of milk fat using the supercritical carbon dioxide extraction. This extraction may offer new possibilities for additional uses of milk fat.     

Triglyceride structure of milk fats

The enantiomeric nature of the triglycerides of bovine milk fat was reinvestigated by determining the stereospecific distribution of fatty acids in rearranged butterfat, following partial hydrolysis with pancreatic lipase, and in certain molecular distillates of native butterfat, following Grignard degradation. The results with rearranged butterfat confirmed the validity of pancreatic lipase hydrolysis as a means of generating representative diglycerides from milk fat triglycerides. The Grignard degradation and lipolysis gave identical distributions for fatty acids when included as part of the assay system in the stereospecific analysis. Characteristically, butyric acid and the other short chain acids occupied the 3 position in the native butterfat, while in the rearranged oil they were distributed more or less randomly. Gas chromatographic analysis of the short chain glycerides on polyester columns allowed an effective resolution of butyryl, caproyl and caprylyl glycerides of identical numbers of total acyl carbons and double bonds. The method was especially well suited for resolution of the 2,3-diglycerides, which were recovered either as the more polar fraction from thin layer chromatography of the X-1,2-diacylglycerols, or by acetolysis of the residual phenolphosphatides resulting from phospholipase A digestion. It was shown that butyric acid in the 3 position was preferentially paired with myristic, palmitic and oleic acid in the 2 position, and palmitic and oleic acid in the 1 position, which was also characteristic of the other short chain acids. One of eight papers presented in the symposium “Milk Lipids,” AOCS Meeting, Ottawa, September 1972.     

Vergleich des Triglyceridmusters von Humanmilch und Säuglingsnahrungen

Comparison between the triglyceride Patterns of Human Milk and Infant Milk Formulae Human milk contains less triglycerides with saturated fatty acids than the three infant milk formulae analysed but has a higher content of triglycerides with two unsaturated fatty acids. The patterns of the major triglycerides are compared. In human milk, palmitic acid is preferably located in position 2 favourable to digestability, whereas in the infant milk formulae it is mostly distributed over positions 1 and 3.     

Über trans-Lipoide: Die Lipoide des Hühnerei-Dotters

Trans Lipids: The Egg Yolk Lipids of the Hen The feeding of hens with a trans-containing edible fat resulted in an increase in the trans fatty acids of the egg yolk lipids to the extent of 10%, which completely disappeared within 14 days after stopping the trans-containing feed. The fatty acids in the triglyceride fractions contained in each case more trans unsaturated fatty acids than those in the corresponding phosphatide fractions. The gas chromatographic analysis of the fatty acid methyl esters showed that the triglycerides contained more oleic acid than the phosphatide fatty acids whereas stearic as well as polyunsaturated components were concentrated predominently in the phosphatides. The analysis of the fatty acid methyl esters from triglyceride and phosphatide fractions after feeding of trans-containing fat showed distinct changes in both the groups, thus for example a reduction of oleic acid in the neutral fat analogous to that in the total lipids as against its increase in phosphatides. The amount of linoleic acid in the phosphatide fatty acids increased while it remained constant in triglyceride fatty acids.     

Individuelle Unterschiede im Fettsäure-Spektrum des Milchfettes bei gleicher Umwelt und Fütterung

Individual Differences in the Fatty Acid Spectrum of Milk Fat with Same Surroundings and Feed From 9 cows, which were kept in the same surroundings and the same feed, for a period of one year, about 500 individual milk samples were collected. From these, the fatty acid spectrum was determined with the help of gas-chromatography and the amount of milk and fat content was also ascertained. The statistical analysis of the results showed individual differences in the ease of some fatty acids. The fatty acid spectrum remained characteristic for individual animals during the whole period of experiment. The individual differences were very pronounced in case of particular acids. In the proportion of fatty acid to fatty acid also, the characteristic individual differences were detected.     

Intramolecular fatty acid distribution in milk fat triglycerides of monkeys

Pancreatic lipase hydrolysis was used to determine the distribution of fatty acids in the milk triglycerides of four species of monkeys and of human milk. The patterns of the major fatty acids were generally similar in all species examined, but there were some differences in the relative concentrations of individual fatty acids esterified at either the 2 or 1,3 positions. Caprylic, stearic, oleic, and linoleic acids were found predominantly at the 1,3 positions; in contrast, lauric, myristic, palmitic, and palmitoleic were concentrated at the 2 position. Monkey milk fats had greater proportions of these acids at the respective positions than did bovine milk fat. Also, the monkey fats were relatively uniform both in total unsaturated fatty acids (41–48%) and in the proportion of these esterified at the 2 position (19–26%). In general, both the fatty acid composition and the specific distribution of fatty acids in the monkey milk fats more closely resembled the patterns in human milk fat than did those in ruminant milk fats.     

Vergleich von Milchfetten aus der Kristallisationsfraktionierung und einem kontinuierlichen Fraktionierungsverfahren mittels überkritischem Kohlendioxid

Comparison of Milk Fat Fractions Obtained by Crystallization with those Obtained in a Continuous Fractionation Process Using Supercritical Carbon Dioxide Several milk fat fractions obtained by crystallization from molten fat as well as milk fat fractions obtained in a new continuous fractionation process using supercritical carbon dioxide have been investigated by GC, HPLC und DSC. The influence of its fatty acid and triglyceride compositions on the crystallization and melting behaviour is discussed. The milk fat fractions obtained by crystallisation tend to crystallize in two distinct main triglyceride group. A separation even into three fractions is shown in the melting thermograms. The milk fat fractions obtained by the fractionation using supercritical carbon dioxide have much less tendency to separate into triglyceride groups. Obviously, this continuous fractionation process using supercritical carbon dioxide can be improved. Therefore, it seems to be possible to obtain milk fat fractions with different triglyceride compositions and better physical properties.     

Zusammensetzung und Aufbau der Triglyceride von Muttermilch und einiger Rohstoffe für Säuglingsnahrung

Composition and Structures of Triglycerides of Human Milk and Some Base Components for Infant Milk Formulas Following HPLC separation of human milk triglycerides with a silver-loaded ion exchange and an RP-18-phase column, the 50 substantial fractions obtained were characterized by gas chromatography of triglycerides and fatty acid methyl esters as well as by the analysis of intramolecular distribution on a reduced scale using ethyl magnesium bromide. Exploitation of all data available resulted in the detailed structures of 106 triglycerides, representing 81 g/100 g human milk fat. A substitute for producing infant milk formulas should be adapted to the composition and fatty acid distribution of those 14 substantial triglycerides which are present in human milk fat with more than 1 g/100 g, amounting to a total of 42 g/100 g. Among several fats and oils analyzed, only lard and a recent product were found to contain palmitic acid also predominantly in the 2-position. Therefore, other base components would require a directed fractionation and/or interesterification to be best adapted to human milk fat.     

Fractionation of anhydrous milk fat by short-path distillation

Anhydrous milk fat was fractionated by short-path distillation into four fractions at temperatures of 245 and 265 C and pressures of 220 and 100 μm Hg. Two fractions (LF1 and LF2) were liquid, one fraction (IF) was semi-solid and one fraction (SF) was solid at room temperature. The fractions were characterized by melting temperature profile, solid fat index and triglyceride and fatty acid compositions. The peak melting temperature progressively increased (8.8 to 38.7 C) from liquid to solid fractions. The solid fat content ranged from 0 to 27.5% at 20 C, while native milk fat was 15.4%. The short chain (C24–C34) triglycerides were enriched in the LF1 fraction, long chain (C42–C54) triglycerides were concentrated in the SF fraction, and medium chain (C36–C40) triglycerides in the IF fraction; in the LF2 fraction, though, both short and medium chain triglycerides were enriched. Short chain (C4–C8) fatty acids gradually decreased from liquid to solid fractions and the trend was reverse for long chain (C14–C18) fatty acids, both saturated and unsaturated. The weight average molecular weights and geometric mean-carbon number of milk fat fractions were in the range of 590.7–782.8 and 31.9–46.3, respectively, compared to 729.3 and 41.0, respectively, for native milk fat, suggesting short-path distillation effects a very high degree of molecular weight separation.     

Triglyceride composition of bovine milk fat with elevated levels of linoleic acid

The effect of increasing the linoleic acid (18∶2) content of milk fat on the composition and structure of the triglycerides (TG) was investigated. Protected sunflower seed supplement was added to the diet of a cow grazing on pasture, and the structure and composition of the milk fat compared with the milk fat from its monozygous twin which had been fed a control diet. The relative proportions of TG fractions of high, medium, and low molecular weight in the milk fat with elevated levels of 18∶2 (15.5% 18∶2) were 43.0, 19.5, and 37.5 moles %, respectively, compared with 36.1, 19.7, and 44.2 moles %, respectively, in the milk fat from the cow fed the control diet. Separation of these three TG fractions of each milk fat into TG classes with different levels of unsaturation showed that the milk fat with elevated levels of 18∶2 contained higher proportions of diene, triene, and tetraene TG and correspondingly lower proportions of saturated and, to a lesser extent, monoene TG. The saturated and monoene TG from the two milk fats had similar fatty acid compositions. However, the diene TG of the 18∶2-rich milk fat included high proportions of the combination of 18∶2 with two saturated fatty acids (FA) which are minor constituents of normal milk fats. Likewise, the triene TG reflected the presence of 18∶2 in combination with 18∶1 and a saturated FA.     

Mammary Uptake of Fatty Acids Supplied by Intravenous Triacylglycerol Infusion to Lactating Dairy Cows

Supplementing dairy cows with n-3 fatty acid-rich feeds does not easily increase quantities in milk fat. Previous results demonstrated very long-chain n-3 fatty acids are primarily transported in the PL fraction of blood, making them largely unavailable to the mammary gland for enrichment of milk fat. Our objective was to compare mammary uptake of fatty acids of increasing chain length and unsaturation delivered intravenously as TAG emulsions. Late lactation dairy cows were assigned to a completely randomized block design. Treatments were intravenous TAG emulsions enriched with oleic acid (OLA), linoleic acid (LNA), alpha-linolenic acid (ALA), or docosahexaenoic acid (DHA) and were delivered continuously at 16 mL/h for 72 h. Each treatment supplied 30 g/day of the target fatty acid. Treatment did not affect feed intake, milk yield, or milk composition, but all treatments reduced intake and yield. The proportion of DHA increased in plasma FFA, TAG, and PL with infusion. Increases of n-3 fatty acids, ALA, EPA, and DHA, were evident in the plasma PL fraction, suggesting re-esterification in the liver. Transfer efficiencies were 37.8 ± 4.1, 27.6 ± 5.4, and 10.9 ± 4.1 %, and day 3 total milk fatty acyl yields were 37.0 ± 3.4, 10.8 ± 0.4, and 3.3 ± 0.3 g for LNA, ALA, and DHA. Variation in oleic acyl yield prevented calculation of OLA transfer efficiency. Mammary uptake of fatty acids was reduced with increased chain length and unsaturation. Both liver and mammary mechanisms may regulate transfer of long-chain polyunsaturates.     

Improving Plasticity of Milk Fat for Use in Baking by Fractionation

Milk fat is soft with a low solids content at all temperatures up to 37 °C, which makes its usage limited. To extend its usage, the fat was fractionated to obtain stearin (St) with a 50–55% yield by dry fractionation. The stearin was found to contain an increased solids content at all temperatures and to have improved plasticity compared to its native fat. The physical properties of St were found to be similar to those of commercial bakery shortenings or vanaspati. The melting profiles and the solidification properties of milk fat St are similar to those of commercial bakery shortening. Also, St does not require extended stabilization or tempering, as it transferred to the most stable form quickly like commercial bakery fat. Milk fat St showed higher proportions of saturated fatty acids including those with short chains, compared to commercial vanaspati, the later having a high trans fatty acid content (15%). The olein obtained could also be used as a cooking medium or as a salad oil since it contains a lower solids content at ambient temperatures compared to its parent milk fat.     

Fettzusammensetzung von Lammfleisch

Fat composition of lamb . The effect of different feeding systems (extensive on pasture and intensive penned) on fatty acid composition of lamb muscle in relation to final product quality was investigated in three feeding trials. Lambs feeding on grass the muscle fat contained more n-3 fatty acids in comparison to penned sheep. The relative quantities of C18:3; C20:5 and C22:6 were markedly higher in grass finished lambs.     

Origin of the milk fat globule

Milk fat globules originate as fat droplets within the lactating mammary cell. These droplets are composed largely (>98%) of glycerides. Their constituent fatty acids are derived by lipolysis of very low density lipoproteins and chylomicrons of the blood and by the novo synthesis within the cell. Evidence of two principal routes for the synthesis of milk fat triglycerides has been presented: the so-called glycerolphosphate and monoglyceride pathways. Recent findings on these pathways are discussed. The nature of the milk triglycerides with their unique compliment and distribution of short chain fatty acids appears to depend upon a closely regulated relation between the soluble multienzyme complex that synthesizes the fatty acids and the glyceride synthetase that is bound to the endoplasmic reticulum. The resulting triglycerides appear to self-assemble into droplets from the surface of the endoplasmic reticulum. No special ultrastructures (transport particles, vesicles, etc.) have been detected in relation to this process. Milk fat droplets at the time of secretion average several microns in diameter, there being species variations. The basic secretion mechanism involves envelopment of the droplet in plasma membrane and expulsion of it from the cell. As a consequence there are at least two pools of polar lipids (cholesterol and phospholipids) associated with secreted milk fat globules, i.e., one from the plasma membrane and one entrained earlier from the endoplasmic reticulum at the time of triglyceride synthesis and accumulation. In all, the polar lipids do not make up more than 1–2% of the total lipids in milk and a substantial fraction of them has been identified recently with plasma membrane fragments occurring in the skim milk phase. Radiotracer and ultrastructural studies show that this membrane material does not result simply by shedding of surface from milk fat globules. This dispersed material and the lining around milk fat globules constitute valuable sources for the study of cell membranes. One of eight papers presented in the symposium “Milk Lipids,” AOCS Meeting, Ottawa, September 1972.