The modification and analysis of vegetable oil for cheese making

Objectives of this study were (i) to incorporate short-chain fatty acids (SCFA) in vegetable oils to obtain a bland product that could be used as a milk fat substitute in cheese making and (ii) to improve the methods for fatty acid analysis of vegetable oils modified with SCFA. Short-chain triglycerides (SCTG) were synthesized by esterifying SCFA with glycerol, and using a toluene azeotrope to remove the water of esterification. SCFA from two sources were used: (i) commercial acids and (ii) acids isolated by double distillation of milk fat methyl esters. The SCTG had a bitter, unacceptable flavor, but after interesterification with high-oleic sunflower oil (HOSO) and deodorization, the flavor was quite acceptable. SCTG were incorporated into HOSO at 100 and 120% of the levels found in the milk fat, by sodium methoxide-catalyzed interesterification. For fatty acid analysis, milk fat and simulated milk fat were converted to their decyl ester derivatives and analyzed by gas chromatography without further purification. The method was accurate and rapid for fatty acid analysis of fats containing a wide range of fatty acid chain lengths. All modified HOSO gave bland and acceptable flavors and had a SCFA composition close to that of milk fat. Results from using the modified HOSO in cheese making are reported in a later paper.     

Modifications of butter stearin by blending and interesterification for better utilization in edible fat products

This work primarily aims to further modify the stearin fractions, obtained from anhydrous milk fat, after fractionation by dry process and by solvent process using isopropanol, for extending their scope of utilization in edible fat products. Butter stearin fractions, on blending with liquid oils like sunflower oil and soybean oil in different proportions, offer nutritionally important fat products with enriched content of essential fatty acids like C_18∶2 and C_18∶3. The butter stearin fraction from isopropanol fractionation, when interesterified with individual liquid oils by Mucor miehei lipase as a catalyst, yields fat products having desirable properties in making melange spread fat products with reasonable content of polyunsaturated fatty acids and almost zero trans fatty acid content.     

Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat

In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C₁₀−C₁₈ fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C₄−C₁₈ fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.     

Utilization of high-melting palm stearin in lipase-catalyzed interesterification with liquid oils

Palm stearin with a melting point (m.p.) of 49.8°C was fractionated from acetone to produce a low-melting palm stearin (m.p.=35°C) and a higher-melting palm stearin (HMPS, m.p.=58°C) fraction. HMPS was modified by interesterification with 60% (by weight) of individual liquid oils from sunflower, soybean, and rice bran by means of Mucor miehei lipase. The interesterified products were evaluated for m.p., solid fat content, and carbon number glyceride composition. When HMPS was interesterified individually with sunflower, soybean or rice bran at the 60% level, the m.p. of the interesterified products were 37.5, 38.9, and 39.6°C, respectively. The solid fat content of the interesterified products were 30–35 at 10°C, 17–19 at 20°C, and 6–10 at 30°C, respectively. The carbon number glyceride compositions also changed significantly. C₄₈ and C₅₄ glycerides decreased remarkably with a corresponding increase of the C₅₀ and C₅₂ glycerides. All these interesterified products were suitable for use as trans acid-free and polyunsaturated fatty acid-rich shortening and margarine fat bases.     

Phase equilibrium and crystallization behavior of mixed lipid systems

As complex lipid systems, the phase and crystallization behavior of mixtures of a high-melting milk fat fraction with a low-melting milk fat fraction or canola oil was studied. A turbidity technique was developed to estimate solubility and metastability conditions of these lipid mixtures. Both solubility and metastability of the high-melting milk fat fraction in liquid lipids increased exponentially with temperature. At a given equilibration temperature, liquid phases and solid fractions with nearly identical melting profiles and TAG compositions were obtained regardless of the original concentration of the lipid mixture. The maximum melting temperature (MMT), as measured by DSC, of the liquid phase increased dramatically in the equilibrium temperature range of 27.5–35.0°C but did not change at temperatures below and above this range (down to 25.0°C and up to 40°C in this study). The content of long-chain TAG (C₄₆−C₅₂) increased and short-chain TAG (C₃₆−C₄₀) decreased in the liquid phases as the equilibrium temperature increased. A plot of the TAG group ratio (i.e, long-short-chain TAG) vs. equilibrium temperature was generated to illustrate the phase behavior of the complex lipid system and to represent a solubility curve, from which the supersaturation level for crystallization kinetics was determined. Higher supersaturation and lower temperature resulted in higher nucleation and crystallization rates. Compared to the system with a low-melting milk fat fraction, mixtures of the high-melting milk fat fraction with canola oil had higher nucleation and crystallization rates due to the lower solubility found for this system.     

Specific distribution of fatty acids in the milk fat triglycerides of goat and sheep

The triglycerides of the fat globules of sheep and goat milk were isolated and separated into short and long chain lengths by silicic acid column chromatography. The short chain lengths comprised major triglycerides with 34–44 acyl carbon atoms and accounted for nearly 50% of the total milk fat. The long chain lengths contained major triglycerides with 40–54 acyl carbons. Stereospecific analyses of the short chain triglyceride fraction showed that of the 20–23 moles per cent of C₄−C₈ fatty acids present, at least 95% were specifically attached to the glycerol molecule in the position corresponding to carbon 3 ofsn-glycerol. The distribution of the other fatty acids (C₁₀ or greater) did not show such marked specificity for either the 1 or the 2 position. Although individual triglycerides were not identified, the specific placement of the fatty acids could best the accounted for by assuming a common pool of long chain 1,2-diglycerides which served as precursors of the bulk of both short and long chain triglycerides during milk fat synthesis. Presented in part at the AOCS Meeting, New York, October 1968.     

Contribution of triglycerides from cocoa butter to the physical properties of milkfat fractions

Milkfat was separated into major chainlength fractions by solid-phase extraction. The effect on thermal behavior and texture of replacing both saturated and monounsaturated long-chain triglycerides from milkfat by long-chain monounsaturated triglycerides with an unsaturated fatty acid in thesn-2 position is reported. Increasing proportions of cocoa butter were added to fractions of short-to medium-chain triglycerides (C₂₂−C₄₄) and medium- to long-chain triglycerides (C₃₆−C₄₈) isolated from milkfat. Thermal behavior and texture of the mixtures were measured. Results indicated that long-chain monounsaturated triglycerides from cocoa butter enhanced co-crystallization and co-operative melting and did not induce polymorphic transitions upon crystallization and melting of the fractions. At 4°C, they acted as texture builder if present in proportions of more than 30%, whereas below this level, they acted as texture softeners. The effect of the long-chain monounsaturated triglycerides on the texture of fractions that melt at low temperature could not be predicted from the proportion of solid fat at that temperature. Presented at the 1995 AOCS Annual Meeting & Expo, San Antonio, Texas, May 1995.     

Trans-free margarine from highly saturated soybean oil

Highly saturated (HS) soybean oil (SBO), which contained 23.3% palmitic acid (C_16:0) and 20.0% stearic acid (C_18:0), was interesterified at 70°C in preparation for the processing of a trans-free margarine. High-performance liquid chromatography analysis of the triacylglycerides and analysis of the sn-2 fatty acid composition showed no further change after 10 min of interesterification. The interesterified HS SBO had a slip melting point of 34.5°C, compared with 9.5°C in the non-interesterified HS SBO, and increased melting and crystallization temperatures were found using differential scanning calorimetry. Analysis of solid-fat content by nuclear magnetic resonance revealed the presence of only a small amount of solids above 33°C. A 50:50 blend of interesterified HS SBO and SBO with a typical fatty acid composition was used to make the margarine. Compared to commercial soft-tub margarine, the maximal peak force on the texture analyzer of this blended margarine was about 2.3 times greater, the hardness about 2.6 times greater, and adhesiveness about 1.5 times greater. There were small but statistically significant differences (α=0.05) in the sensory properties of spreadability, graininess, and waxiness between the commercial and blended margarines at 4.5°C and, except for graininess, at 11.5°C. These very small differences suggest a potential use for HS SBO in margarine products.     

Milk fat structure of a patient with type 1 hyperlipidemia

Structural analyses were performed on milk fat samples obtained 3–10 days postpartum from a lactating patient with primary Type 1 hyperlipidemia. The milk triacylglycerols contained 3–7% C₁₀, 14–21% C₁₂, 20–30% C₁₄, 22–26% C₁₆ and 20–30% C₁₈ (largely oleic) acids. Gas liquid chromatographic (GLC) analyses of the X-1,3- and X-1,2-diacylglycerols on polar siloxane columns showed a markedly non-random association of acyl chains. Stereospecific analyses indicated that the short chain length fatty acids were confined essentially to the sn-3-position of the triacylglycerol molecule. Furthermore, these acids were largely absent from the phosphatidylcholines and the endogenous sn-1,2-diacylglycerols of the milk fat. It is concluded that the short chain fatty acids are incorporated into the milk triacylglycerols during the final stage of biosynthesis via the phosphatidic acid pathway, and that the overall fatty acid distribution is consistent with the 1-random 2-random 3-random hypothesis.     

Enzymatic Interesterification of Coconut and High Oleic Sunflower Oils for Edible Film Application

Blends [60:40, 70:30, and 80:20 (w/w)] of coconut oil (CO) and high oleic sunflower oil (HOSO) were interesterified using immobilized enzyme, Lipozyme^® TL IM (Novozymes North America Inc., Franklinton, NC, USA). The structured lipids (SLs), referred to as interesterified products (IPs) IP60:40, IP70:30, and IP80:20, were compared to CO and HOSO for application in edible films. IPs were compared based on fatty acid profile, TAG molecular species, melting profile, moisture vapor permeability, mechanical properties, film transparency, density, and thickness. Interesterification increased oleic acid content at the sn-2 position of IPs. CO had 5.50 ± 1.67 mol% oleic acid at the sn-2 position, and when interesterified with HOSO (92.81 ± 1.10 mol% oleic acid) the amount of oleic acid significantly increased (p < 0.05) at the sn-2 position for IP60:40, IP70:30, and IP80:20 (33.86 ± 1.55, 27.34 ± 1.20, 20.61 ± 1.50 mol%), respectively. There was no significant difference between SLs, HOSO, and CO for water vapor permeability and density when applied to emulsion edible films. The HOSO film was significantly different (1.43 ± 0.27 AUmm^?1) from the rest of the SLs and CO for film transparency. IP60:40 (2.20 ± 0.22 AUmm^?1) decreased the opacity and was significantly different from HOSO and IP80:20 (2.88 ± 0.08 AUmm^?1). Tensile strength of IP60:40 was 0.39 ± 0.17 MPa which was significantly different from IP70:30, IP80:20, and HOSO. The elongation at break was significantly different for HOSO and IP60:40. IP60:40 could be used to further investigate the use of SL in edible film for sports nutrition products.     

Docosahexaenoic acid in developing brain and retina of piglets fed high or low α-linolenate formula with and without fish oil

Docosahexaenoic acid (22∶6n−3) can be synthesized in the liver and/or brain from α-linolenic acid (18∶3n−3) and is required in large amounts in structural membranes of developing brain and retina. The adequacy and efficacy of formulas containing 18∶3n−3 and/or fish oil in providing 22∶6n−3 for deposition was investigated in piglets fed formula from birth to 15 days. The test formulas contained high (HL) or low (LL) 18∶3n−3 (3.9 or 0.7% of the total formula fatty acids, respectively), or low 18∶3n−3 plus fish oil (LL+FO) to provide C₂₀ and C₂₂ n−3 polyunsaturated fatty acids (0.8% of total fatty acids). Fatty acid analyses of synaptic plasma membrane and retina ethanolamine phospholipids (EPL), which are especially enriched in 22∶6n−3, were compared to those of 15-day-old piglets fed sow milk (SM). Feeding LL resulted in lower 22∶6n−3 in synaptic plasma membrane. Fatty acid levels in HL and LL+FO piglets were equivalent to SM, with the exception of lower 22∶5n−3 in the synaptic plasma membrane of LL+FO and in the retina of HL and LL+FO-fed piglets. Levels of 22∶4n−6 were also lower in the retina of the LL+FO group. The results suggest formula 18∶3n−3 is at least 24% as effective as C₂₀ and C₂₂ n−3 fatty acids as a source of membrane 22∶6n−3. This study shows dietary 18∶3n−3, as the only n−3 fatty acid, can support deposition of comparable percentage of 22∶6n−3 to natural milk. Fish oil also supported tissue levels of 22∶6n−3 similar to natural milk; however, lower 22∶4n−6 may indicate possible inhibitory effects on n−6 metabolism. Recipient of the 1967 Science and Engineering Scholarship, Natural Sciences & Engineering Research Council of Canada.     

Physical and chemical properties of trans-free fats produced by chemical interesterification of vegetable oil blends

Fat blends, formulated by mixing a highly saturated fat (palm stearin or fully hydrogenated soybean oil) with a native vegetable oil (soybean oil) in different ratios from 10:90 to 75:25 (wt%), were subjected to chemical interesterification reactions on laboratory scale (0.2% sodium methoxide catalyst, time=90 min, temperature=90°C). Starting and interesterified blends were investigated for triglyceride composition, solid fat content, free fatty acid content, and trans fatty acid (TFA) levels. Obtained values were compared to those of low- and high-trans commercial food fats. The interesterified blends with 30–50% of hard stock had plasticity curves in the range of commercial shortenings and stick-type margarines, while interesterified blends with 20% hard stock were suitable for use in soft tubtype margarines. Confectionery fat basestocks could be prepared from interesterified fat blends with 40% palm stearin or 25% fully hydrogenated soybean oil. TFA levels of interesterified blends were low (0.1%) compared to 1.3–12.1% in commercial food fats. Presented at the 88th AOCS Annual Meeting and Expo, May 11–14, 1997, Seattle, Washington.     

Characterization of skin-surface lipids from the monkey (Macaca fascicularis)

Skin-surface lipids from the monkeyMacaca fascicularis are composed of sterol esters (38%), cholesterol (4%) and two types of wax diesters, identified as Type II (IIa and IIb, 17% and 40%, respectively). Type IIa contained diesters of 1,2-alkanediols esterified with two molecules of long-chain (C₁₄−C₃₄) fatty acids having straight and branched chains. In the diesters IIa, fatty acids shorter than C₁₉ predominated in position 1, and fatty acids longer than C₂₀ predominated in position 2. Type IIb contained diesters of 1,2-alkanediols esterified with C₄ and C₅ branched-chain fatty acids (predominantly isovaleric acid) at position 1 and long-chain (C₁₄−C₂₇) acids, having straight and branched chains, at position 2. The shortchain acids were converted to 2-nitrophenylhydrazides and analyzed by high-performance liquid chromatography (HPLC). Ammonia chemical ionization (CI)-gas chromatography (GC)-mass spectrometry (MS) resolved the intact diesters IIb into 12 peaks corresponding to molecular weights ranging from 597 to 748, and showed that the molecular species, such as C₂₁−C₁₆−C₅ (diol, fatty acid in position 2, fatty acid in position 1), C₂₂−C₁₆−C₅ and C₂₃−C₁₆−C₅, were prevalent. The fatty acids from both diesters were mostly (>98%) saturated. The 1,2-alkanediols from both diesters consisted of C₁₆−C₂₆ saturated straight- and branched-chain components. The acyl groups of sterol esters contained 86% C₁₄−C₃₄ branched-chain acids. The unsaturated fatty acids (5.4%) belonged to a straight-chain monoenoic series having extremely long chains (C₁₈−C₃₄). The branched-chain structures in the fatty acids and diols were iso and anteiso. These results show the species-specific profile for the skin-surface lipid synthesis.     

A cross-species comparison of neutral lipid composition of milk fat of prosimian primates

The fatty acid composition of milk fat is known to be affected by dietary and genetic differences, while the milk triacylglycerol structure is believed to be attuned to the needs of the subsequent lipolysis during gastrointestinal passage. The availability of milk samples from eight species of prosimian primates, whose milk triacylglycerol structure had not been analyzed, offered an opportunity to further assess these ideas. The milk samples were collected by manual expression and the lipids extracted with chloroform/methanol (2∶1, vol/vol). The lipid classes were resolved by thin-layer chromatography, and the neutral lipids subjected to detailed analyses by capillary gas-liquid chromatography of fatty acids and molecular species of triacylglycerols using nonpolar and polarizable liquid phases. The milk samples were found to differ greatly in total fat content (4–73%) and in the composition of the neutral liqid classes and molecular species. The concentration of triacylglycerols ranged from 88–95%, free fatty acids from 0.5–10%, alkyldiacylglycerols from 0.5–5.0%, and diacylglycerols, monoacylglycerols and free and esterified cholesterol made up the remainder. The fatty acid chain length ranged from C₈−C₂₄, with palmitic (16–31%) and oleic (13–40%) acids being the major components in most of the species. In all instances, the molecular association of the fatty acids differed from random distribution by a higher proportion of the monoacid (trioleoyl) and diacid (dipalmitoyloleoyl) glycerols. The phylogenetic influences on neutral milk lipid composition, however, remained unclear, as some of the differences between closely related species were greater than those between more distantly related ones. Triacylglycerol structures are abbreviated by listing their three constituent fatty acids in sequence, e.g., PPP, LaOL.     

Detection of interesterified fats in hydrogenated fats

Interesterification of fats is being used increasingly as an alternative to hydrogenation in preparing shortening and margarine bases. The detection of interesterified fats in vanaspati (a hydrogenated fat) is relevant because of possible adulteration problems. Either palmitic acid-rich or stearic acid-rich interesterified fats were blended with 13 market samples of hydrogenated fat (vanaspati) and examined by on-plate lipase hydrolysis of glycerides, gas chromatographic determination of fatty acids of the isolated 2-monoglycerides and calculation of two emperical indices. These were R₁, the ratio of the amounts of palmitic acid present in the 2-position to that in the total glyceride, and R₂, the ratio of saturated acid present in the 2-position to total saturated fatty acid in the fat. The vanaspati, R₁ was always below 10 and R₂ was always below 20. The presence of 5–10% interesterified fat raised both figures and offered a suitable basis for the detection of interesterified fats in hydrogenated fats.     

Ceramide structure of sphingomyelin from human milk fat globule membrane

Sphingomyelin was purified from human milk fat globule membrane and submitted to phospholipase C to yield ceramide. The structure of this ceramide was investigated by gas liquid chromatographic analyses of its components, fatty acids and sphingoid bases. The structure of the native ceramide was confirmed by direct-inlet mass spectrometry. It was shown to contain a major base C₁₈-sphingosine associated with a high proportion (60%) of C₂₀, C₂₂, C₂₄ and C_24∶1 nonhydroxylated fatty acids. As these very long-chain fatty acids might be of nutritive importance, the concentration of sphingomyelin in human milk and its distribution in cream and skim milk were established.     

Influence of lipase-catalyzed interesterification on the oxidative stability of melon seed oil triacylglycerols

Melon seeds are rich in oil. However, the stability of melon seed oil (MSO) is low because of its high content of the essential fatty acid, linoleic acid (18:2n-6). MSO was physically blended or enzymatically interesterified with higholeic sunflower oil (HOSO). The fatty acid composition of MSO was remarkably changed after interesterification. Palmitic (16:0), stearic (18:0), and oleic (18:1n-9) acid contents increased at the sn-2 position of triacylglycerols, whereas 18:2n-6 decreased due to interesterification. The oxidative stability of the physical and Pseudomonas sp. (PS30) lipase-interesterified blends was assessed with the Oxidative Stability Instrument, peroxide value, and conjugated diene methods. The stability of MSO increased with increased proportions of HOSO, which was the source of 18:1n-9 in the blends. The ratio of 18:1n-9/18:2n-6 improved from 0.18 in MSO to 1.47 in the enzymatically interesterified blend. Calculated oxidizability and the results of oxidation tests of the blends confirmed the improvement in MSO stability by both physical blending and enzymatic interesterification.     

Influence of lipase-catalyzed interesterification on the oxidative stability of melon seed oil triacylglycerols

Melon seeds are rich in oil. However, the stability of melon seed oil (MSO) is low because of its high content of the essential fatty acid, linoleic acid (18:2n-6). MSO was physically blended or enzymatically interesterified with higholeic sunflower oil (HOSO). The fatty acid composition of MSO was remarkably changed after interesterification. Palmitic (16:0), stearic (18:0), and oleic (18:1n-9) acid contents increased at the sn-2 position of triacylglycerols, whereas 18:2n-6 decreased due to interesterification. The oxidative stability of the physical and Pseudomonas sp. (PS30) lipase-interesterified blends was assessed with the Oxidative Stability Instrument, peroxide value, and conjugated diene methods. The stability of MSO increased with increased proportions of HOSO, which was the source of 18:1n-9 in the blends. The ratio of 18:1n-9/18:2n-6 improved from 0.18 in MSO to 1.47 in the enzymatically interesterified blend. Calculated oxidizability and the results of oxidation tests of the blends confirmed the improvement in MSO stability by both physical blending and enzymatic interesterification.     

Distinctive medium chain wax esters,triglycerides, and diacyl glyceryl ethers in the head fats of the pacific beaked whale,Berardius bairdi

Lipids were extracted from the mandibular fat body (jaw), the fatty forehead (melon), and the dorsal blubber of a Pacific beaked whale (Berardius bairdi) and separated into lipid classes by preparative thin layer chromatography. The head fats were mixtures of wax esters and triglycerides with a very small amount of diacyl glyceryl ether. The blubber fat contained 97% was ester and 3% triglyceride. Gas liquid chromatography (GLC) of the intact lipid classes indicated an unusually low C₂₆–C₃₀ range for most of the jaw and melon wax esters compared to the more normal C₃₂–C₄₀ molecules found in the blubber. Distinctive lower molecular weight C₂₄–C₄₀ triglycerides occurred in the head fats vs. the usual C₄₄–C₅₈ range in the blubber. Most diacyl glyceryl ethers were in the C₃₅–C₄₆ range, below the molecular weight of hexadecyldipalmitoyl glyceryl ether (C₄₈). GLC of the derived fatty acid methyl esters showed that the lower molecular weight neutral lipids in the head fats were due to high levels of iso-10∶0, n−10∶0, iso-11∶0, iso-12∶0, n−12∶0, and iso-13∶0 acids. The wax ester fatty alcohols and the alkoxy chains of the glyceryl ethers were mostly the C₁₄–C₂₀ chain lengths commonly observed in marine organisms. The distinctive medium chain neutral lipids in the jaw and melon fats of this whale may be related to the postulated acoustical role of these tissues in echolocation.     

Structure of bovine milk fat triglycerides: II. Long chain lengths

The long chain triglycerides of bovine milk fat were isolated by thin layer chromatography, and their chemical structure determined by combined thin layer and gas liquid chromatography, and a stereospecific analysis of a molecular distillate of butteroil of comparable composition. The milk fat fraction (39% of total) contained C₈–C₂₀ fatty acids which were distributed among the glycerides of 40–56 acyl carbon atoms in a manner not unlike that found for the same acids in the short chain triglycerides. Although individual triglycerides were not identified, the specific distribution of the fatty acids could best be accounted for by assuming a common pool of long chain 1,2-diglyceride precursors from which the bulk of both short and long chain triglycerides are synthesized by a stereospecific introduction of C₄–C₁₈ fatty acids in position 3 of sn-glycerol. This hypothesis is compatible with the results of stereospecific analyses of the short and long chain fractions and of the total butteroil. It is supported by the nonrandom distributions demonstrated for the molecular weights of the milk fat triglycerides of different degrees of saturation. Presented in part at the AOCS meeting, Philadelphia, October, 1966.