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.     

Distinction between enzymically and chemically catalyzed interesterification

The 1,3-specific lipase-catalyzed interesterified fats were distinguished from chemically catalyzed products by the fatty acids in the 2-position. The fatty acid contents in the 2-position of the 1,3-lipase-catalyzed and the original triglycerides were similar but different from that of chemically interesterified fat. Also, the saturated-to-unsaturated fatty acid ratio in the 2-monoglycerides was lower for the 1,3-specific lipase-catalyzed interesterified fats than for the corresponding chemical products.     

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.     

Physical Properties of <Emphasis Type="Italic">trans</Emphasis>-Free Bakery Shortening Produced by Lipase-Catalyzed Interesterification

Lipase-catalyzed interesterified solid fat was produced with fully hydrogenated soybean oil (FHSBO), and rapeseed oil (RSO) and palm stearin (PS) in a weight ratio of 15:20:65, 15:40:45 and 15:50:35. The interesterified fats contained palmitic (27.8–44.6%), stearic (15.6–16.2%), oleic (27.5–36.5%) and linoleic acids (8.0–13.5%). After interesterification of the blends, the physical properties of the products changed and showed lower melting points and solid fat contents, different melting and crystallization behaviors as well as the formation of more stable crystals. The produced interesterified fats (FHSBO:RSO:PS 15:20:65, 15:40:45 and 15:50:35 blends) contained desirable crystal polymorphism (β′ form) as determined by X-ray diffraction spectroscopy, a long plastic range with solid fat content of 51–63% at 10 °C to 4–12% at 40 °C, and melting points of 39 (15:50:35), 42 (15:50:45) and 45 °C (15:20:65). However, a reduction in tocopherols (α and γ) content and a reduced oxidative stability were observed in the interesterified fats. The physical properties of the interesterifed fats were influenced by the amount of PS, resulting in more hardness and higher solid fat contents for 15:20:65 than 15:40:45 and 15:50:35 blends. The present study suggested that the produced interesterified fats containing trans-free fatty acids could be used as alternatives to hydrogenated types of bakery shortenings.     

Trans‐free fats through interesterification of canola oil/palm olein or fully hydrogenated soybean oil blends

Binary blends of canola oil (CO) and palm olein (POo) or fully hydrogenated soybean oil (FHSBO) were interesterified using commercial lipase, Lypozyme TL IM, or sodium methoxide. Free fatty acids (FFA) and soap content increased and peroxide value (PV) decreased after enzymatic or chemical interesterification. No difference was observed between the PV of enzymatically and chemically interesterified blends. Enzymatically interesterified fats contained higher FFA and lower soap content than chemically prepared fats. Slip melting point (SMP) and solid‐fat content (SFC) of CO and POo blends increased, whereas those of CO and FHSBO blends decreased after chemical or enzymatic interesterification. Enzymatically interesterified CO and POo blends had lower SMP and SFC (at some temperatures) than chemically interesterified blends. The status was reverse when comparing chemically and enzymatically interesterified CO and FHSBO blends. The induction period for oxidation at 120°C of blends decreased after interesterification. However, chemically interesterified blends were more oxidatively stable than enzymatically interesterified blends. Interesterified blends of CO and POo or FHSBO displayed characteristics suited to application as trans‐free soft tub, stick, roll‐in and baker's margarine, cake shortening and vanaspati fat.     

The effect of dietary fat on the glyceride structure of rat carcass fat

Carcass fats were obtained from weanling rats fed a complete diet for 8 weeks, which consisted of 2% cottonseed oil and 10% of the following fats: (1) corn oil; (2) the fatty acids of corn oil; (3) triricinolein; (4) ricinoleic acid; (5) the hydrogenated fatty acids of castor oil ; and (6) commercial hydrogenated shortening. The fats were subjected to both pancreatic lipase and nonspecific hydrolysis ; the resulting acids converted into methyl esters by conventional methods, and subjected to gas Chromatographie analysis. From these data, the positional distri-bution of the component fatty acids, glyceride types, and isomeric forms were calculated. The results indicated a preferential placement of un-saturated acids in the 2- position of the carcass triglycerides and that the carcass fat composition in terms of unsaturated (U) and saturated (S) fatty acid composition is not greatly influenced by the S and U compositions of the dietary fat. It was found that hydroxy acids or their tri-esters are metabolized much the same as are normal triglycerides and exert no particular in-fluence upon the fat structure of the rat. Some type of relationship between the dietary U and the U₃ in the carcass fat appears to be present. The glycerides of the carcass fats examined here are essentially a random mixture of the major glyceride types, but the isomeric forms (SUS, S SU, USU and UUS) are a definite non-random mixture. Carried out at the Food Res. Div., Armour & Co., and at The Burnsides Research Laboratory under research grant No. EF 225 from the National Institutes of Health, U. S. Public Health Service, and Deparmtent of Health, Education, and Welfare.     

Fractionation of Interesterified Fats for the Preparation of Plastic Fats

Some specific directed interesterified fat products which had high slip points and had little potentiality for use as edible fats, were crystallized from acetone at different low temperatures. The appropriate fractions obtained from interesterified products of Ricebran containing Mowrah, Palm, Sal and of Sal and Cottonseed mixture (1:1, w/w), appeared to be suitable for utilization as vanaspati and margarine like fat products with high essential fatty acid content and without trans unsaturated fatty acids and also as highly stable deep frying fats and bakery fats.     

Studies on Nutritional Quality of Interesterified Fat Products

The nutritional quality of the fat products with melting range 36° to 37°C having been prepared from non-traditional oils like mowrah (Madhuca latifolia), ricebran (Oryzasativa) containing sal (Shorea robusta) and cottonseed (Gossypium hirstum) mixed with sal by interesterification (randomisation) were examined with rats and compared with that of “Vanaspati”, produced by hydrogenation of mixtures of liquid oils and used exclusively as a substitute of ghee (butter fat) in India. The average food intake, body weight gain, food efficiency ratio, weight of different organs, total lipid content of serum, liver, heart and kidney were similar in all the cases. Serum triglyceride levels were quite low in case of interesterified fats fed rats though total and free cholesterol levels were not significantly different. Serum phospholipid levels were slightly higher in case of the interesterified fats fed rats. Total and free cholesterol, phospholipid and triglyceride content of liver, kidney and heart were similar for the four dietary groups of rats. Serum lipids and liver lipids contain more polyunsaturated fatty acids when rats were raised on various interesterified fats in place of hydrogenated fat product “Vanaspati”.     

Physical analyses of gel-like behavior of binary mixtures of high- and low-melting fats

Gel-like fat mixtures of high-melting (HM) and low-melting (LM) fats were formed by means of rapid cooling and subsequent heating. No “non-fat” ingredients such as emulsifiers, water, or waxes were added to the mixtures. The gel-like fats having solid fat content (SFC) values below 2.0 wt% formed crystal networks of HM-fats that entrapped the liquid oil fraction of LM-fats. In a search for optimal fat combinations exhibiting gel-like behavior, fully hydrogenated rapeseed oil with a high amount of behenic acid (FHR-B), fully hydrogenated rapeseed oil with a high amount of stearic acid (FHR-S), tristearoylglycerol (SSS), triarachidonoyl-glycerol (AAA), and tribehenoylglycerol (BBB) were examined as the HM-fats. For LM-fats, sal fat olein (SFO), cocoa butter (CB), palm super olein (PSO), and olive oil were examined. The following results were obtained: (i) the gel-like behavior was observed in mixtures of FHR-B/SFO and FHR-B/CB with initial concentrations of FHR-B of 1.5–4.0 wt%. (ii) Rapid cooling to T _c (crystallization temperature) from 70°C and subsequent heating to T _f (final temperature) were necessary to reveal the gel-like behavior, whereas simple cooling without a cooling/heating procedure did not form the gel-like fat mixture. (iii) Optimal values of T _c and T _f were related to the m.p. of the LM-fat and HM-fat, respectively. (iv) Temperature variations of SFC as well as X-ray diffraction spectra showed that the melt-mediated transformation from α to β of the HM-fat crystals was a prerequisite to reveal the gel-like behavior. Consequently, the fat mixture revealing the gel-like behavior might be called β-fat gel.     

Storage stability of margarines produced from enzymatically interesterified fats compared to those prepared by conventional methods – Chemical properties

In this study, four margarine hardstocks were produced, two from enzymatically interesterified fats at 80 and 100% conversion, one from chemically randomized fat and one from physically mixed fat. These four hardstocks, blended with 50% sunflower oil, were mainly used for the production of table margarines in a pilot plant. Storage stability studies were carried out at storage temperatures of 5 and 25 °C for 12 wk. Margarines from the enzymatically interesterified fats were compared to the margarines produced by the conventional methods (chemical interesterification and physical blending) and to selected commercial margarines. The changes in the chemical properties of the products, including peroxide values (PV), tocopherols, free fatty acids, volatile oxidation products, and sensory evaluation, were examined during storage. It was observed that the margarine produced from the chemically interesterified fat had higher PV in weeks 4, 8 and 10 than the margarines produced from the enzymatically interesterified fats and the physically blended fat. These differences were not caused by different contents of tocopherols in the hardstocks. The differences between the processes for chemical and enzymatic interesterification, including further treatment stages, might be responsible for the development of a high PV in the margarine produced from the chemically interesterified fat. However, the contents of volatiles did not show the same tendency as observed for PV for the margarines stored at 25 °C during 12 wk. Storage at 25 °C accelerated oxidation compared to storage at 5 °C. The content of δ‐ and γ‐tocopherols decreased faster than the content of α‐ and β‐tocopherols during storage. This phenomenon was only affected by storage time, not by storage temperature. Sensory analysis did not show consistent differences between the produced margarines and commercial margarines, and no hydrolysis occurred for these four margarines during storage. The margarines produced from the enzymatically interesterified fats had low PV and a similar taste and smell compared to the margarine produced from the chemically interesterified fat.     

Physico-chemical characteristics of palm-based oil blends for the production of reduced fat spreads

The effect of blending and interesterification on the physicochemical characteristics of fat blends containing palm oil products was studied. The characteristics of the palm-based blends were tailored to resemble oil blends extracted from commercial reduced fat spreads (RFS). The commercial products were found to contain up to 20.4% trans fatty acids, whereas the palm-based blends were free of trans fatty acids. Slip melting point of the blends varied from 26.0–32.0°C for tub, and 30.0–33.0°C for block RFS. Solid fat content at 5 and 10°C (refrigeration temperature), respectively, varied from 10.9–19.7% and 8.5–17.6% for tub, and 28.2–38.6% and 20.8–33.5% for block RFS. Melting enthalpy of the tub RFS varied from 35.0–54.3 J/g and that of block RFS varied from 58.0–75.4 J/g. To produce block RFS, 65% palm oil (PO) and 18% palm kernel olein (PKOo) could be added in a ternary blend with sunflower oil (SFO), but only 47% PO and 10% PKOo are suggested for tub RFS. Higher proportion of PO, i.e., 72% for block RFS and 65% for tub RFS, could be used after the ternary blend was interesterified. Although a ternary blend of palm olein (POo)/SFO/PKOo was not suitable for RFS formulation, after interesterification as much as 90% POo and 26% PKOo could be used in the block RFS formulation. For tub RFS a maximum of 30% POo was found suitable.     

Melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils

The melting behavior of milk fat, hydrogenated coconut and cottonseed oils, and blends of these oils was examined by nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). Solid fat profiles showed that the solid fat contents (SFC) of all blends were close to the weighted averages of the oil components at temperatures below 15°C. However, from 15 to 25°C, blends of milk fat with hydrogenated coconut oils exhibited SFC lower than those of the weighted averages of the oil components by up to 10% less solid fat. Also from 25 to 35°C, in blends of milk fat with hydrogenated cottonseed oils, the SFC were lower than the weighted averages of the original fats. DSC measurements gave higher SFC values than those by NMR. DSC analysis showed that the temperatures of crystallization peaks were lower than those of melting peaks for milk fat, hydrogenated coconut oil, and their blends, indicating that there was considerable hysteresis between the melting and cooling curves. The absence of strong eutectic effects in these blends suggested that blends of milk fat with these hydrogenated vegetable oils had compatible polymorphs in their solid phases. This allowed prediction of melting behavior of milk-fat blends with the above oils by simple arithmetic when the SFC of the individual oils and their interaction effects were considered.     

Definition of a model fat for crystallization-in-emulsion studies

Numerous food products are dispersed in droplet emulsions in which fat is partially crystallized. A model fat allowing the study of crystallization in emulsion, obtained by the mixing of two fats (one solid and one liquid at room temperature) with simple triacylglycerol (TG) composition, is defined and characterized. Cocoa butter (CB), a vegetable fat mainly composed of monounsaturated long-chain fatty acids (POP, POST, StOSt, where P=palmitic, O=oleic, St=stearic), and miglyol, a synthetic oil made from capric and caprylic fatty acids, were chosen, respectively. The thermal behaviors of CB, miglyol, and their mixtures are studied using high-sensitivity differential scanning calorimetry (DSC). The CB/miglyol ratio was optimized (i) in order to make stable emulsions as a function of time, (ii) so that the mixture displays several solid phases on cooling that result from CB polymorphism, and (iii) in order to keep, even at low temperature, a liquid moiety facilitating the phase transitions. The CB 75%/miglyol 25% composition is defined as the model mixture. This mixture is characterized on cooling at 0.5°C/min by coupled X-ray diffraction as a function of temperature and DSC experiments. First and α 2L (49.3 Å) variety is formed. Then, co-crystallization of both CB and miglyol TG shows the simultaneous formation of longitudinal stackings of 44.5 and 34.5 Å with a lateral organization of β′ form. An unusual TG packing corresponding to compound formation is proposed to explain the observation of a 34.5 Å long-spacing. The crystallization behavior of the model fat mixture dispersed in emulsion droplets is also monitored in order to validate its use.     

Expansion of solidifying saturated fats

From literature it appears that simple saturated triglycerides and commercial fats contract to a considerable extent when they undergo transformation from liquid to solid state and from an instable to a more stable crystalline form. In spite of these facts, the simple saturated even triglycerides and some fully hydrogenated fats exhibit violent solidification expansion by voluntary cooling. Solidification experiments carried out with several saturated even triglycerides and fats under various solidification conditions have shown that the solidification expansion tendency depends upon the chemical composition of the fat, as well as on the solidification conditions. The solidification expansion tendency is increased by various more or less independent factors, namely decreasing iodine value, increasing fatty acid and triglyceride uniformity, increasing triglyceride symmetry, increasing tendency to rapid formation of the stable β crystals, seeding with β crystals, voluntary cooling, moderate cooling velocity, and increasing bulk amount of fat. All the expanded solidified fats ended up being in the β crystalline form, whereas the nonexpanded fats ended up with the β’ form. The solidification expansion is avoidable by careful control of the cooling procedure.     

Effect of chemical interesterification on triacylglycerol and solid fat contents of palm stearin,sunflower oil and palm kernel olein blends

Palm stearin (POs) with an iodine value of 41.4, sunflower oil (SFO) and palm kernel olein (PKOo) were blended in various ratios according to a three‐component mixture design and subjected to chemical interesterification (CIE). Triacylglycerol (TAG) and solid fat content (SFC) profiles of the chemically interesterified (CIEed) blends were analyzed and compared with those of the corresponding non‐CIEed blends. Upon CIE, extensive rearrangement of fatty acids (FA) among TAG was evident. The concentrations of several TAG were increased, some decreased and several new TAG might also have been formed. The changes in the TAG profiles were reflected in the SFC profiles of the blends. The SFC of the CIEed blends, except the binary blends of POs/PKOo which experienced an increase in SFC following CIE, revealed that they were softer than their respective starting blends. Randomization of FA distribution within and among TAG molecules of POs and PKOo led to a modification in TAG composition of the POs/PKOo blends and improved miscibility between the two fats, and consequently diminished the eutectic interaction that occurred between POs and PKOo.     

Dilatometric investigations of fats II. Dilatometric behavior of some plastic fats between 0° C. and their melting points

Summary 1. Dilatometric curves between 0°C. and their melting points have been obtained for the following fats: lard, butterfat, cottonseed oil, peanut oil, a commercial margarine oil, a commercial all-hydrogenated vegetable shortening, three samples of soybean oil hydrogenated to different degrees, a hard butter fractionally crystallized from hydrogenated peanut oil, a mixture of tristearin and soybean oil, and a synthetic fat containing equal molar proportions of stearic and oleic acids. 2. The dilatometric curves, of volume change in the fat against temperature, were in every case composed of a series of straight lines, separated by sharp breaks or transition points. 3. The number of linear sections in the dilatometric curves corresponded in a general way with the known degree of complexity in the glycerides of the fats, and varied from two in the case of the relatively simple stearic-oleic glyceride mixture, to at least seven in the case of the all-hydrogenated shortening. Since each break in the curve must correspond to the disappearance of a distinct class of solid glycerides or glyceride complexes, the application of dilatometry to the qualitative and quantitative determination of glyceride composition in fats is suggested. 4. Only two of the fats examined, the mixture of tristearin and soybean oil, and the synthetic stearicoleic glyceride mixture, exhibited polymorphism, even after rapid solidification in ice water. Presented before the American Oil Chemists’ Society Meeting, New Orleans, Louisiana, May 10 to 12, 1944. This is one of four regional research laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Spectrophotometric determination of small amounts of 1-monoglycerides in fats

A method is described for the determination of small amounts of 1-monoglycerides in fats. The method consists of a periodic acid oxidation, the resulting glycol aldehyde fatty acid ester then being converted to the 2,4-dinitrophenylhydrazone derivative, which is determined spectrophotometrically. The colored solutions are stable and follow Beer’s law in the range 0.0–1.0% 1-monoglycerides with a standard deviation of ±0.024%. Glycerol does not interfere.     

Modification of selected indian vegetable fats into cocoa butter substitutes by lipase-catalyzed ester interchange

A few solid and semi-solid fats of tree origin in India, namely sal (Shorea robusta), kokum(Garcinia indica), mahua (Madhuca latifolia), dhupa (Vateria indica) and mango (Mangifera indica), were chosen for modification into cocoa butter substitutes by lipase-catalyzed ester interchange with methyl palmitate and/or stearate. Hexane solutions of mixtures of fat and methyl ester(s) in various molar proportions were passed through a column of Lipozyme™, a lipase fromMucor miehei immobilized on a macroparticulate ion-exchange resin. The interesterified fats were purified by extraction with 95% ethanol followed by silica column chromatography. Interesterified dhupa, kokum and sal fats compared well with cocoa butter in the total fatty acid composition and the 2-position of triacylglycerols, as well as glyceride composition. In particular, interesterified kokum fat resembled cocoa butter well in solid fat content and peak melting temperature as determined by differential scanning calorimetry. IICT Communication No. 2743.     

Determination of fat composition

A revolution has taken place in the analysis of fats. Physical methods, both rapid and accurate, have replaced laborious chemical procedures. The timehonored saponification equivalents and iodine values now are calculated from Chromatographic and nuclear magnetic resonance spectroscopic data. Differential migration processes such as countercurrent distribution, liquid-liquid chromatography, and gas chromatography have supplanted the classical distillation and crystallization procedures for analysis and preparation. What have been referred to as “gadgets” are now the stock-in-trade of the analytical lipid chemist. Mass, infrared, ultraviolet, and nuclear magnetic resonance spectrometers are the accepted tools for organic characterization. Recording detectors and computer processing of data reduce the labor of analysis and improve its quantitation. Today’s methodology stands at the verge of specifying fatty acid composition of even so complex lipids as hydrogenated fats in terms of the amounts, the positions, and geometric configurations of its individual component fatty acids. Presented at the AOCS Short Course, East Lansing, Mich., Aug. 29-Sept. 1, 1966. No. Utiliz. Bes. Dev. Div., ARS, USDA.     

Random interesterification of fat blends with alkali catalysts

Random interestification of fat blends, composed from vegetable oil and fully hydrogenated vegetable oil, catalyzed by sodium hydroxide and sodium methoxide, has been investigated. Sodium methoxide was used as a reference catalyst to evaluate the influence and the catalytic efficiency of NaOH on interesterification. Sodium hydroxide was found to be a suitable catalyst for this purpose. The choice of methods suitable for the investigation of interesterification reactions and characterization of the initial fat blends and their interesterified products is described. The randomization was followed by the changes in the triacylglycerol (TAG) composition of the fat blends determined by HPLC and high temperature GLC. This triacylglycerol composition of the original blends and the randomized products with the physical properties such as melting behaviour, crystallization and solid fat content were compared. The results show that the randomization of vegetable oil - fully hydrogenated vegetable oil fat blends in various ratios can be used to produce fats with desired physical and nutritional properties.