Nonionic microemulsions containing triglucerides and fatty acid esters as lipophilic components have been studied. The phase inversion temperature (PIT) of the systems was determined by a conductometric method. Partial phase diagrams were constructed in the phase inversion temperature range. Water solubilization capacity of the nonionic surfactant systems studied was dependent on surfactant and oil types in analogy to ordinary hydrocarbon systems. The PIT:s increased with increased molecular weight for both esters and triglycerides.

The phase behavior and the structure of ionic microemulsions, stabilized by sodium oleate and different alcohol cosurfactants, containing fatty acid esters or triglycerides as lipophilic components, have been investigated. Microemulsions containing triglycerides display a smaller stability region than microemulsions containing hydrocarbons or fatty acid esters. From structural investigations, using the NMR FT pulsed gradient spin echo method for measuring self-diffusion coefficients, differences in the microstructure are revealed as well. Adding an ester (or a hydrocarbon) to a microemulsion containing sodium oleate/pentanol will at certain compositions lead to a gradual transition from a bicontinuous to an oilcontinuous system, while this behavior cannot be detected when adding a triglyceride. Instead, a phase-separation occurs, and it is suggested that the larger molecular size of the triglyceride is responsible for the diffirence.

The influence of oxygen concentration and copper on lipid oxidation in rapeseed oil during storage at 40°C was investigated. The oil was stored in air, or with 1.1%, 0.17%, or 0.04% oxygen in the headspace, and 70 or 0.07 ppm copper was added. Volatile oxidation products and oxygen consumption were monitored. Addition of 70 ppm copper to the sample in air resulted in a 70-fold higher hexanal concentration after 35 d of storage, compared to the sample without added copper. The addition of 0.07 ppm copper to the sample stored in air gave a doubled hexanal concentration, compared to the sample without copper, after 35 d of storage. For the samples with 70 ppm copper at 0.17% and 0.04% oxygen, all oxygen was consumed after 7 d of storage. The results show the importance of minimizing the oxygen available for oxidation, especially when pro-oxidants are present. In the sample with 70 ppm added copper, in air, the hexanal increase was 65 times larger than for the same sample in 0.04% oxygen. A comparison of the effect of oxygen or copper on oxidation shows that the addition of 70 ppm copper to the 0.04% oxygen sample gave the same increase in hexanal content as an oxygen increase to 0.17%.

The destabilization of foams by electrolytes with tetraalkylammonium ions has been investigated. The presence of large tetraalkylammonium ions at the oil/water interface perturbs the packing of surfactants, producing noncoherent films of low stability. A comparison between the foam destabilizing efficiency of tetraalkylammonium bromide salts with tributyl phosphate and 2-ethyl hexanol, which are used in many commercial antifoaming formulations, demonstrated that the organic salts have a potential for being useful in technical applications involving foam inhibition.

In this study we establish the use of optical non-contact profilometry combined with low vacuum scanning electron microscopy (LV SEM) for the investigation of lipid surfaces. We illustrate, by using profilometry, a methodology for investigation of chocolate surface topology as a function of time, in the same area of interest. Both qualitative and quantitative data analysis has been performed for profilometry data. Further, relating these results to LV SEM images provides complementary topological information and hence a useful toolkit for the study of the chocolate surface prior and post fat bloom formation. For the demonstration of the successful combination of these two analytical techniques, white chocolate pralines were stored at two temperature-controlled conditions (at 18 °C, and cycled between 15 and 25 °C). Surface properties were then investigated during 36 weeks of storage. The surface images and the roughness parameters indicated distinct development of surface characteristics for the two storage conditions. From the results it is suggested that some imperfections, in the form of pores or protrusions, could play a role in fat bloom development and that there may be different main mechanisms of fat migration taking place for the different storage environments. In the present work, a positive correlation of profilometry data to chocolate surface characteristics and early bloom development has been established. There are indications that early prediction of fat bloom can be possible, however further work needs to be done to quantify prediction of fat bloom.

Cis and trans isomers of fatty acid methyl esters, fatty alcohols, and triacylglycerols were analyzed with a silver-ion high-performance liquid chromatography system. Gradients of n-heptane and acetonitrile were used to elute molecules with up to nine cis double bonds. The analyses were as fast and reliable and had a resolution similar to that of the best published analyses. However, published analyses were performed with chlorinated solvents, and these solvents are carcinogenic and mutagenic. The solvents we used, heptane and acetonitrile, are less dangerous to the analyst.

Purified catalase and peroxidase were denatured by heat, acid and urea. Denaturation resulted in up to 22-fold increase in nonenzymatic lipid oxidation activity concomitant with loss of enzymatic activity. It is proposed that the increased nonenzymatic activity is due to increased exposure of the heme group. Acid-splitting of the hemoproteins into apoprotein and hemin had the greatest influence on both of the catalytic activities and recombination reversed the effect. Urea-denatured hemoprotein possessed increased nonenzymatic activity due to increased exposure of the protein-bound heme, however, peroxidase increased less than catalase which is consistent with the fact that peroxidase is the more heat stable enzyme. Nonenzymatic activity of the heat denatured hemoproteins was maximum when catalase was treated at 90 C for 2 min and peroxidase at 100 to 125 C for 5 to 30 min. © 1971 AOCS.

The surface composition of spray-dried sodium caseinate/lactose emulsions with different oil-phases were estimated by ESCA and the particle structure was studied by SEM before and after storage under humid conditions. After spray-drying, powders in which the oil phases consisted of fats with intermediate melting points like hardened coconut oil and butter fat had the highest surface coverage of fat, approx. 34 %. Powder with soy-bean oil as the oil phase had a surface coverage of fat of approx. 15 %. The high melting hardened rape-seed oil was almost completely encapsulated after spray-drying. After storage in a humid atmosphere, fat was released onto all the powder surfaces (surface fat after storage, between 50-65 %) except for those with hardened rape-seed oil in which the fat remained encapsulated. These observations are consistent with the powder structure observed by SEM. The surface composition estimated by ESCA for spray-dried sodium caseinate/lactose-containing emulsions with different amounts of soy-bean oil and a constant lactose/sodium caseinate ratio show an almost completely encapsulated oil-phase after drying. Storage of these powders in a humid atmosphere leads to a release of fat onto the powder surface even if the soy-bean oil content is low ( 1 % of the dry weight). Powders made from soy-bean oil emulsions with sodium caseinate alone exhibit a much lower degree of encapsulation than in the system where lactose is present.

Free fatty acids (FFA) are liberated in the first stages of potato granule production. In this study, the liberation of FFA was examined in model experiments. Potato slices were exposed to conditions resembling the first stages of the industrial process, which was of the "add-back type". The slices were kept at 9°C in the dark and, after various periods of time (up to two hours), the amount and composition of the FFA liberated at the surface and in the middle of the potato slices were analyzed by gas chromatography. The liberation of FFA was more pronounced at the surface of the slices than in the middle. The polyunsaturated fatty acids, linoleic acid and linolenic acid, were liberated to a greater extent than the saturated fatty acids. The experiment was repeated at 4°C and the results obtained were very similar. The lower temperature did not decrease the rate of FFA liberation. But, in thin potato strips, which have a larger total surface of damaged membranes than the potato slices, considerably more FFA were liberated. The amount and composition of FFA also were analyzed in potato slices from the industrial process for potato granule production. Before the blanching bath (76°C for 12-15 min) only minor amounts of FFA were liberated but during the blanching there was a substantial liberation of FFA at the surface of the potato slices. After the blanching bath there were no more FFA liberated at the surface of the slices but in the middle of the potato slices the liberation of FFA continued until the potato slices reached the steamcooking bath. © 1990 AOCS Press.

The formation of volatile compounds in potato slices was analyzed by means of gas Chromatographie headspace analysis. The experimental variables selected for the treatment of the potato slices were chosen to simulate the conditions during the first stages of an "add-back type" of process for production of potato granules. The potato slices (2 cm thick) were exposed to air of low temperature (4°C) and water at blanching temperature (76°C). Both the surface and the middle of each slice were analyzed for volatile compounds. Hexanal was the most abundant aldehyde formed. At the elevated temperature, in particular, there was an obvious formation of hexanal. After 15 min of blanching, the amount of hexanal was higher in the middle of the slices than at the surface. This difference in hexanal concentration was probably due both to the leakage of hexanal into the blanching water from the surfaces of the potato slices, and to the inac-tivation of lipoxygenase at the surfaces which prevented further oxidation during the subsequent chilling period. The hexanal formation indicates that lipid oxidation occurs during the process. The formation of other volatile compounds also is discussed. © 1990 American Oil Chemists' Society.

In a functional characterization, a set of data is obtained which gives information on the fields of application for a certain protein ingredient. This fingerprint can be used as a guideline in product development and restricts the amount of tests on large scale. The function of a protein in a complex food system can be better understood if a functional characterization is combined with a microstructural investigation. This may be especially important in cases where proteins act by indirect functionality, i.e., when the prescence of one protein changes the function of another component. In order to improve the efficiency of functional characterizations, methodologies need to be further developed. This is especially important for characterization of gels, emulsions, and mixtures of structures. © 1979 The American Oil Chemists' Society.

Heat-induced protein gels are of importance for the structure and properties of many food products. Gel formation is a complex process which often involves several reactions such as denaturation, dissociation-association, and aggregation. The kinetics of the reactions involved will determine the type of structure formed. Protein gels can be divided into two types: gels formed by random aggregation and gels formed by association of molecules into strands in a more ordered way. The two soy proteins glycinin and conglycinin both have the ability to form ordered structures consisting of strands 10-15 nm thick. The glycinin gel strands formed in distilled water are regular, and cross sections of strands showed a hollow cylindrical structure. In the presence of sodium chloride, glycinin forms an aggregated gel structure at 85 C, but at 95 C a regular structure similar to that found in distilled water was formed. The aggregated structure was interpreted as a transient state similar to the soluble aggregate formed on heating dilute solutions prior to dissociation into subunits. Conglycinin gels are more irregular and more cross-linked than gels of glycinin. Also, the strands of conglycinin showed a complex mode of aggregation possibly in the form of double spirals. The addition of salt does not affect the microstructure of conglycinin gels as dramatically as in the case of glycinin gels. Commercially produced soy protein isolates may behave quite differently from native soy proteins, due to processing conditions causing denaturation and various states of aggregation. © 1986 American Oil Chemists' Society.

Strength of fat crystal networks in oil increases at elevated temperature due to increased adhesion between partially melted crystal surfaces. This strong adhesion, in combination with low oil viscosity (weak hydrodynamic force), is the reason for extensive fat crystal flocculation at elevated temperatures. The crystal flocs likely sinter, dramatically increasing the thickness of semisolid fats. Crystal growth also occurs. The described temperature induced crystal changes may be suppressed by a controlled sintering process at low temperature. Emulsifiers, such as sorbitan esters of tristearate, also suppress the temperature induced changes. Fat crystals can be used as thickeners or gelling agents for triglyceride oils in various applications. It is possible to direct the thickening to a specific temperature, and control the degree of thickening, by choice of fat phase composition, additives, tempering conditions and crystallization technique.

The formation of fat crystal gels in soybean oil has been studied by sedimentation in a low concentrations region at 10-25°C. At 10°C, weak gels were formed with 1% crystals and no gels formed with concentrations 2-5%. At temperatures 15-25°C, no gels were formed with concentrations 1-5%, and samples sedimented. Stronger gels of fat crystals were formed with ~10% fat crystals at all temperatures examined. Formation of weak gels is a consequence of the fractal nature of fat crystal aggregates and sediments. At low temperature, the interaction is weak. The fractal dimension is then high and the floc size is very large for low crystal concentrations. These large flocs form a three dimensional network, acting as a weak gel withstanding gravitational force. When the temperature is increased, the fat crystal interaction is stronger, fractal dimension decreases, and floc size decreases. Smaller flocs have a higher density, pack more easily, and sediment. Similar effects are observed when the concentration of fat crystals is increased at low temperature due to a decrease in floc size.

Lecithin is a powerful emulsifier widely used in foods, feeds and pharmaceuticals, which functions mainly due to its adsorption properties. Lecithin adsorbs to fat crystals at the triglyceride oil/water interface, and makes their surface more polar (observed as an increase in the contact angle measured through the oil at the interface: fat crystal/oil/water). This adsorption process is quick (less than five minutes) for relatively polar lecithins like soybean phosphatidylcholine (PC), and results in highly polar surfaces (contact angle ≈180°). Less polar lecithins give a slow adsorption (some hours) and less polar crystals (contact angle < 90°). The adsorption of different lecithins to the oil/water interface, observed as a decrease in interfacial tension, follows the adsorption pattern to the fat crystals (the more polar the lecithin the quicker the adsorption). There is a relationship between the high polarity of fat crystals and the poor functionality of lecithin in margarine (margarines spatters during frying). There is also a relationship between a high polarity of fat crystals and a high ratio of polar to nonpolar phospholipids (SPI+PA+LPC/SPE) in lecithin. The correlations migth be via aggregation properties of lecithin in the oil, which should influence both the adsorption kinetics and the structure of adsorbed layers. A monoglyceride (monoolein) shifts the adsorption kinetics of lecithin (soybean PC) to fat crystals and the structures of adsorbed layer. The reason is probably a formation of mixed aggregates between monoolein and soybean PC.

Several foods contain semisolid fats consisting of solid crystals dispersed in a liquid oil. In oil continuous margarine, butter and chocolate, fat crystals determine properties such as consistency, stability against oiling-out and emulsion stability. Trends towards foods with less fat and/or less saturated fat create a need for understanding and controlling the properties of fat crystal dispersions. Fat crystals form a network in oil due to mutual adhesion. A source of strong adhesion is formation of solid bridges (sintering), and has been studied in this work through sedimentation and rheological experiments. Results indicate that sintering may be created by crystallization of a fat phase with a melting point between that of the oil and the crystal. Generally speaking, ß´ crystals were sintered by ß´ fat bridges favoured by rapid cooling, and ß crystals by ß fat bridges favoured by slow cooling. The necessity of the same polymorphic form of the crystal and bridge indicated that solid bridges rather than bridges formed by small crystal nuclei were formed. A maximum in sintering ability for an optimal sintering fat concentration occurred due to competition between bridge formation and other crystallization processes. Some emulsifiers influenced the sintering process. For example, monooolein made it more pronounced, while technical lecithin had the opposite effect.

The adsorption isotherms of several emulsifiers to fat and sugar crystals dispersed in oils have been determined. Further, the influence of the emulsifiers on the interactions between the crystals has been estimated in sedimention experiments, where an increased sediment volume due to adsorption corresponds to an increased adhesion between the crystals and vice versa. Most of the emulsifiers examined adsorb weakly to fat crystals and form tight monolayers, resulting in increased adhesion between the crystals at high concentrations. On the other hand, loosely packed layers are formed at low concentrations, and a decreased adhesion is observed. Unsaturated monoglycerides and phospholipids cause a decrease in adhesion for all concentrations examined. The emulsifiers adsorb more strongly to sugar crystals than to fat crystals and form tightly packed monolayers with hydrocarbon chains directed to the oil. The crystals are then stabilized sterically - the adhesion between them is weaker and the sediments are more compact. At low concentrations the opposite behaviour often occurs. Monoglycerides interact in a specific way with sugar and cause an increased adhesion between the crystals for all concentrations examined. Phospholipids reduce the adhesion between sugar crystals, resulting in much denser sediments. Saturated monoglycerides in amounts over the solubility limit, tend to precipitate as a network between fat or sugar crystals, which causes bulky sediments and results in better stability against oiling out.

The influence of food emulsifiers on the viscoelastic properties (storage modulus and yield value) of fat and sugar dispersions in vegetable oils has been investigated. It was found that almost all of the emulsifiers tested influence the rheology of the dispersions. The magnitude and the direction of the rheological changes depend on both the type and amount of emulsifier. In most cases relatively small changes occur, especially for fat crystals. Generally speaking, the largest changes are caused by lecithins and saturated monoglycerides. The magnitudes of colloidal forces and the equilibrium distances between the particles have been estimated from the rheological network model of van den Tempel and from the correlation of the yield value to the interaction energy by Gillespie et. al.. The results indicate that van der Waals forces alone can not be responsible for the interparticle interaction in fat or sugar dispersions. The formation of water bridges is discussed as a probable source of interaction in both cases. Further, the validity of the network model for the fat and sugar dispersions in oils is questionable.

The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable oils) was qualitatively estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers (monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (non triglycerides) on the interactions and on the emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also increases the surface activity of the oil soluble food emulsifiers. Minor oil components give a small increase in the adhesion between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way.

Fat crystals influence the stability of food emulsions such as margarine, butter or cream if adsorbed to oil/water interface. During the adsorption process, a new fat crystal/water interface is created while the oil/water interface is lost. The driving force for adsorption is therefore the difference between the interactions fat crystal/water and oil/water. In this work we have estimated this interaction difference and compared it to displacement energy for fat crystals from the oil/water interface to the oil. Our calculations have shown that fat crystal adsorption to the oil/water interface (expressed by contact angle Q) is determined by polar energy, excess fat crystal/water over oil/water (Isw-Iow). The interfacial tension constitutes the resistance force for crystal adsorption to the interface. Polar interaction energy fat crystal/water is stronger than polar interaction energy oil/water in all cases examined (Isw-Iow>0). The difference corresponds to about 104-106 hydrogen bonds for a hypothetical fat crystal with a diameter of 1 µm. Displacement energy for fat crystals to oil, is lower than polar energy excess in most cases examined. Thus, an additional interaction between fat crystals and oil make it easy to displace the crystals to the oil. There is also a relationship between adhesion tension (-gow·cosQ) for the crystals at oil/water interface, and the interfacial tension gow. A straight line of a slope -1 is achieved for systems with low interfacial tensions (gow) and low polar energy excess (Isw-Iow).

The influence of low concentrations (0.1-5%) of fat crystals on the stability of water-in-soybean oil emulsions was examined by light scattering and sedimentation experiments. Both initial flocculation/coalescence rate and long term stability against water separation were determined. The initial flocculation/coalescence rate increased upon addition of very small amounts of fat crystals. When the crystal concentration was increased over a critical concentration (specific to a system), a decrease in the flocculation/ coalescence rate occurred. The increased flocculation/ coalescence rate is likely the effect of bridgening of water droplets by fat crystals. Fat crystal wetting by water is an important criterion for this phenomenon to occur. Emulsion stabilization for crystal concentrations over critical is caused by a mechanical screening of water droplets. The presence of considerable amounts of crystals in oil also lowered the density difference between droplet and medium, and enhanced viscosity. The degree of increase in viscosity depended upon emulsifier. Both decrease in density difference and increase in viscosity play a role in hindering flocculation/ coalescence of droplets. In long term studies of water separation, all concentrations of fat crystals stabilized the w/o emulsions. The droplet size of these emulsions increased likewise until the critical droplet size was approached, when the screening effect of crystals on droplets stabilized the emulsions. The stabilizing effect for emulsions with monoolein was continuously improved by increasing the amount of crystals up to 5%. For lecithin stabilized emulsions, an optimal effect was achieved for fat crystal concentrations of 1-2%.

Wetting of fat crystals has been extensively examined in this work by contact angle (0) measurements of fat crystal, oil, and water in three-phase contact. Contact angle was measured in oil. The crystals were nonpolar and wetted by oil for a contact angle equal to 0°, and polar and wetted by water for an angle equal to 180°. Fat crystals are expected to contribute to the stability of margarine emulsions if they are preferentially wetted by the oil phase (0° c 0 < 90°), but result in instability if they are preferentially wetted by the water phase (90°

Nonionic, cationic and anionic surfactants, derivatives of cis-13-docosenoic acid (erucic acid) have been prepared and characterized, and their performance has been evaluated and compared with the corresponding derivatives of fatty acids with shorter alkyl chain length. Nonionic erucic acid ethoxylates give a solution behavior anticipated from the hydropholic-lipophilc balance of the molecule; however, the incresed molecular size as compared to ordinary surfactants results, eg., in higher temperature stability of the surfactants aggregates. Anomalous solution behavior was found and investigated for anionic surfactants, trithanolammonium salts of erucic acid, and some shorter homolouges. The effects are discussed in terms of the asidbase equilibra of the alkanolammonium counterion and the acid, together with effects due to the molecular size of the counterion.

An NMR technique to measure the exchange kinetics at thermal equilibrium in dispersions of moderately soluble crystalline material is presented. By monitoring the exchange of molecules between pools in solid and dissolved form one can characterize the surface specific exchange rate. Illustrative experiments were performed in a model system with b-type crystals of tripalmitin as the solid phase and tripalmitin, a fraction of it deuterated, dissolved in a medium chain triglyceride oil as the liquid phase. The concentration of deuterated tripalmitin in the solvent was followed by 2H NMR after the crystals, that initially lack deuterated tripalmitin, were immersed in the liquid. The variation of the 2H concentration in the solvent provided the surface specific exchange rate. No systematic errors, due to the slight difference in properties of the deuterated tripalmitin (2H-PPP) compared to hydrogenated tripalmitin (1H-PPP), were observed. The methodology worked well between crystal concentrations of 2 and 4-wt%.

The properties of sphingomyelin obtained from bovine milk were investigated. In particular, the properties of liposomes and emulsions prepared from the sphingomyelin, as well as the liquid crystalline behaviour, were investigated and compared to those of related phosphatidylcholine systems. Like sphingomyelins from other sources, sphingomyelin from milk contains a large fraction of long and saturated acyl groups, which results in a high (35-82°C, depending on the lipid concentration) gel-to-liquid crystal transition temperature (Tc). At high sphingomyelin concentrations, a lamellar phase forms above Tc, while below Tc, a swelling gel phase is obtained. The gel phase swells to about 20 wt% water, whereas above Tc, the swelling continues to about 40 wt% water. The limiting areas per molecule are 51 and 68 Å2 below and above Tc, respectively. Sphingomyelin from milk forms liposomes readily in the presence of cholesterol. The liposomes formed have a diameter of about 100 nm, and are stable even at 0.1 M NaCl or HCl. Materials entrapped in the liposomes are released rather slowly (typically 40 % over 5 h). A comparison shows that the sphingomyelin liposomes behave similarly to those formed by phosphatidylcholine systems. Furthermore, sphingomyelin from milk forms stable o/w emulsions with soy bean oil. The size of the emulsion droplets obtained was about 200 nm. Both the size of the emulsion droplets and its dependence on electrolyte addition correlate closely with those of emulsions formed by the corresponding phosphatidylcholine system. Therefore, it is possible to use sphingomyelin as an alternative for saturated phosphatidylcholines, which may be advantageous for oral and dermal pharmaceutical applications, as well as in cosmetics.

Oxidation was measured by oxygen consump-tion in a Warburg apparatus, modified to main-tain constant partial oxygen pressure by auto-matic electrolytic generation of oxygen with automatic recording of the oxygen consumed. The decrease in rate of oxygen consumption on the lowering of partial oxygen pressure at at-mospheric pressure was found to depend on a) the varying influence of the nonoxygen-dependent and the oxygen-dependent reactions of the prop-agation which may vary with the conditions such as the reactivity of the substrate, the tem-perature, and the pH value but which is not affected by light irradiation; b) the varying rate-limiting effect of slow oxygen diffusion, depending on the ratio between the rate of oxidation and the rate of oxygen diffusion. © 1968 American Oil Chemists' Society.

Earlier studies on lipid oxidation at low oxygen pressure were continued to cover the effect of low oxygen pressure in the presence of added metal salts. Addition of Cu2+ and Fe3+ salts was shown to exert a catalytic effect, which, on increasing metal concentration, may reach a maximum and then decrease. This so called conversion is favored at low oxygen pressure (e.g., corresponding to 1% O2 at atmospheric pressure). Under certain conditions it may result in an antioxidative effect. The phenomenon is more pronounced at pH 5 than at pH 7, and it is dependent on the anions present and the ratio between the concentration of the catalyst and that of the substrate. A tentative explanation of these effects of Cu2+ and Fe3+ salts at low oxygen pressure, which are not given by Fe2+ and Co2+ salts, is offered. © 1971 AOCS.

The TBA reactivities of several aldehydes, most of them known as ordinary products of lipid autoxidation, have been investigated systematically. Gas liquid chromatography-purified alkanals, 2-alkenals and 2,4-alkadienals were reacted with TBA in water solution. The formation of pigments with maximum absorbance at 450 and 530 nm was measured at optimum time-temperature conditions-different for readings at 450 and 530 nm- and values for absorbance per mole aldehyde were calculated. These values show that on reaction with TBA all studied aldehydes build a yellow 450 nm pigment, while only 2,4-alkadienals and, to a lesser extent, 2-alkenals produce the red 530 nm pigment. Consequently both pigments are measures of aldehydic products of lipid autoxidation: In the case of predominant unsaturated aldehyde formation, determination of the pigment with maximum absorbance at 530 nm is preferable. However, if alkanals are predominant, the determination of the yellow pigment at 450 nm is more apporpriate, as it grants higher sensitivity. © 1973 American Oil Chemists' Society.

Phosphatidylcholine containing a long chain polyunsaturated acyl group at the 2-position has been prepared by phospholipase A 2 catalyzed esterification of lysophosphatidylcholine with polyunsaturated fatty acids EPA (C20:5) or DHA (C22:6). Preliminary studies showed that the other fatty acids, such as lauric acid (C12), palmitic acid (C16), stearic acid (C18) and linoleic acid (C18:2), were also incorporated. To our knowledge, phospholipase A 2 catalyzed condensation reactions have not been reported in the literature before. The reactions were performed in sodium bis(2-ethylhexyl)-sulfosuccinate-based microemulsions containing small amounts of water. Synthesis of the same phospholipid by transesterification of phosphatidylcholine with the polyunsaturated acids in microemulsion failed; however, enzymatic hydrolysis to lysophosphatidylcholine was facile, quantitative conversion from phosphatidylcholine being attained after 16 hr reaction time. An additional observation was that, unlike enzymatic hydrolysis of phospholipids, the condensation reaction catalyzed by phospholipase A 2 was totally independent of the presence of calcium. © 1990 AOCS Press.

With the increased use of plant oils as sustainable feedstocks, industrial oilseed meal from Crambe abyssinica (crambe) and Brassica carinata (carinata) can become a potential source for oilseed meal based plastics. In this study, crambe and carinata oilseed meal plastics were produced with 10-30 % glycerol and compression molding at 100-180 C. Size exclusion HPLC was used to relate tensile properties to changes in protein solubility and molecular weight distribution. By combining glycerol and thermal processing, increased flexibility has been observed compared to previous work on unplasticized oilseed meal. Tensile results varied from a brittle crambe based material (10 % glycerol, 130 C), Young's modulus 240 MPa, strain at maximum stress of 2 %, to a soft and flexible carinata based material (30 % glycerol, 100 C), Young's modulus 6.5 MPa, strain at maximum stress of 13 %. Strength and stiffness development with increasing molding temperature is in agreement with the protein profiles obtained. Thus, the highest mechanical parameters were obtained at the protein solubility minimum at 140 C. Higher temperatures caused protein degradation, increasing the level of low molecular weight extractable proteins. In carinata based materials the strain at maximum stress decreased as the protein aggregation developed. Results presented indicate that both crambe and carinata oilseed meal based materials can have their properties modulated through thermal treatment and the addition of plasticizers.

Enzyme catalyzed esterification reaction was carried out in single phase, oil-continuous microemulsions. The lipozyme was solubilized, along with glycerol and water, in the aqueous core of water/AOT/hydrocarbon microemulsion system. Upon addition of fatty acid, mono- and diglycerides were formed due to the esterification reaction taking place at the interface of the droplets in the microemulsion. The initial rate of conversion of oleic acid increases with oil chain length of the continuous phase whereas final conversion is maximum for hexane. The percent conversion of stearic acid is 30% whereas the percent conversion of oleic acid is 70%. The percent conversions of various fatty acids under the same continuous medium increases with chain length of fatty acids. The oleic acid/glycerol ratio is an important parameter for the optimum conversion of oleic acid into glycerides. The percent yield can be increased by subsequent addition of glycerol after equilibrium is reached. Temperature has a considerable effect on the synthesis reaction. HPLC analysis of samples from microemulsions show the presence of mono- and diglycerides. Possible mechanisms for the above mentioned effects are discussed.

In the present paper lipase catalyzed synthesis - esterification of oleic acid with glycerol - i8 carried out in L2 microemulsions and in monolayers. The microemulsions were based on isooctane as nonpolar component and various water-glycerol mixtures as polar component. The substrate, oleic acid/sodium oleate, constituted the microemulsion surfactant. The lipase is known to reside mainly in the water pools. Monolayers of oleic acid/sodium oleate were formed on subsolutions of glycerol and water and the enzyme solution was injected under the compressed monolayers. Thus, the arrangement of the reactants at the oil-water interface of the microemulsion can be regarded as analogous to that at the air-water interface of the monolayer. The microemulsion structure was characterized by self-diffusion NMR. It was found that the higher the glycerol to water ratio, the lower are the water D-values. The reactions in microemulsions generally gave a low degree of oleic acid conversion. The yield increased with increasing glycerol to water ratio. Monoglycerides were the main product and no triglyceride could be detected. The monolayer experiments gave a somewhat higher degree of conversion with tri- and diglycerides being the major reaction products. The reason why triglycerides are formed in monolayer experiments but not in microemulsions is believed to be due to an unfavourable partitioning of the diglyceride in the microemulsion systems. Once formed, the diglyceride will partition into the hydrocarbon domain and become inaccessible for reaction with the enzyme-O-acyl intermediate at the oil-water interface. In addition, the interfaces in the two systems are very different. The monolayer interface is static, whereas the microemulsion interface is highly dynamic, and this difference may also influence the product pattern.

The surfactant, ethyl 6-O-decanoyl glucoside, was synthesized in microemulsion systems by lipase catalysis. The microemulsions were based on the two substrates for the reaction, ethyl glucoside and fatty acid, and either the sodium salt of the fatty acid or the glucoside ester was used as surfactant. The lipase used was component B from Candida antarctica. Reduced pressure was employed to eliminate the water of condensation. The reaction yield was good, with conversion of fatty acid and ethyl glucoside reaching 77 and 96%, respectively.

Atomic force microscopy (AFM) has been used to study the surface of chocolate as well as the progress of chocolate bloom over time. Fresh chocolate was found to be relatively smooth but with deep holes. These could be pipes leading deep down into the body of the chocolate, perhaps reaching the filling. After storage for a few weeks, we observed the growth of small drops around these holes. With increasing time, these drops became larger and more structured. After further storage, a crystalline structure and bloom were revealed. These results suggest that bloom growth in pralines is a two-phase process, with drops initially forming on the surface and then bloom crystals nucleating and growing from them. Further, we deduced pipes leading down into the center of the chocolate through which the migration of filling fats can preferentially occur.

Light muscle, dark muscle, and skin from herring (Clupea harengus) were stored separately or as intact fillets at -18°C. After 0, 2, 8, 12, and 18 wk, all tissues were analyzed for conjugated dienes (A234) and lipid hydroperoxides. In tissues stored separately, total absorbance at 268 nm (A268) and lipid-soluble fluorescent oxidation products (FP) were also monitored. Further, prior to storage these tissues were subjected to measurement of total lipids, lipid classes, fatty acid pattern, ?-tocopherol, iron, copper, selenium, and total aqueous pro-oxidative activity. When light muscle, dark muscle, and skin were stored as intact fillets, the following ranking order was seen for A234 and levels of lipid hydroperoxides at the end of the storage period: skin > dark muscle > light muscle. The corresponding ranking order for tissues stored separately was: dark muscle > skin > light muscle, whereas for A268 and FP the orders were: dark muscle > light muscle > skin and light muscle > dark muscle > skin, respectively. The compositional data obtained indicate the highest level of pro-oxidants in dark muscle and the highest level of polar lipids in light muscle. These observations reveal that pro-oxidants, to a greater extent than lipid composition, influence the increase in A234, hydroperoxides, and A268, whereas the reverse seems to be true for the increase in FP. The results also point to the strong influence from oxygen contact and tissue interactions on the progress of lipid oxidation in herring during storage.

Extremely rapid hydrogenation of fatty acid methyl esters (FAME) to fatty alcohols (FOH) occurs when the reaction is conducted in a substantially homogeneous supercritical phase, using propane as a solvent, over a solid catalyst. At these conditions, the limitations of hydrogen transport are eliminated. At temperatures above 240 °C, complete conversion of the starting material was reached at residence times of 2 to 3 s, which is several orders of magnitude shorter than reported in the literature. Furthermore, formation of by-products, i.e., hydrocarbons, could be prevented by choosing the right process settings. Hydrogen concentration turned out to be the key parameter for achieving the above two goals. As a result of the supercritical conditions, we could control the hydrogen concentration at the catalyst surface independently of the other process parameters. When methylated rapeseed oil was used as a substrate, the hydrogenation catalyst was deactivated rapidly. However, by using methylated sunflower oil, a catalyst life similar to that obtained in industrial processes was achieved. Our results showed that the hydrogenation of FAME to FOH at supercritical conditions is a much more efficient method than any other published process.