Effect of physical refining on selected minor components in vegetable oils

The final quality of vegetable oils is largely determined by the deodorization process. From an organoleptic point of view, oils should be light in color with a bland taste and a good cold and/or oxidative stability. Today, however, more and more attention is paid to the real nutritional quality. Oils should contain low trans fatty acid levels, low polymeric triglycerides, and secondary oxidation products and at the same time being rich in natural antioxidants. In order to comply to these new quality requirements, the deodorization technology has been modified substantially. Mathematical models were established describing the influence of different process parameters (time, temperature, steam, and pressure) on trans fatty acid formation, tocopherol stripping, and production of oxidized and polymeric triacylglycerides during physical refining of soybean oil. Trans fatty acid (TFA) formation was influenced only by time and temperature. No significant influence of pressure or sparging steam could be observed. Models expressing the relative degree of cis/trans-isomerization of linoleic (DI_18:2) and α-linolenic acid (DI_18:3) could be extrapolated to other oils and deodorizer designs. Tocopherol removal was mainly influenced by process temperature and sparging steam. Additionally, tocopherol retention seemed to be dependent on the deodorizer design (steam injection geometry and sparging steam distribution). During physical refining, oxidized and polymerized triacylglycerols were not significantly influenced by any of the investigated process parameters. Industrially, process conditions are adapted to minimize trans fatty acid formation and maximize tocopherol retention. These goals can be achieved in a so-called DUAL TEMP^copy; deodorizer.     

Determination of sorbitan tristearate in vegetable oils and fats

A new method for analysis of Sorbitan Tristearate (STS) in vegetable oils and fats has been developed. The method is based on isolation and hydrolysis of STS compounds in a silica cartridge. The polyalcohols are eluted from the silica cartridge and the final separation and quantitation are done by high-performance liquid chromatography and refractive index detection. Linearity, precision, and recovery satisfy general demands on quantitative methods. The detection limit and the quantitation limit are well below the concentrations normally used to attain functional effects of STS in vegetable oils and fats.     

动植物油生产清洁燃料和低碳烯烃的替代加工工艺

Since the production cost of biodiesel is now the main hurdle limiting their applicability in some areas, catalytic cracking reactions represent an alternative route to utilization of vegetable oils and animal fats. Hence, catalytic transformation of oils and fats was carried out in a laboratory-scale two-stage riser fluid catalytic cracking （TSRFCC） unit in this work. The results show that oils and fats can be used as FCC feed singly or co-feeding with vacuum gas oil （VGO）, which can give high yield （by mass）of liquefied petroleum gas （LPG）, C2-C4 oletms, tor example 45% LPG, 47% C2-C4 olefins, and 77.6% total liquid yield produced with palm oil cracking. Co-feeding with VGO gives a high yield of LPG （39.1%） and propylene （18.1%）. And oxygen element content is very low （about 0.5%） in liquid products, hence, oxygen is removed in the form of H2O, CO and CO2. At the same time, high concentration of aromatics （C7-C9 aromatics predominantly） in the gasoline fraction is obtained after TSRFCC reaction of palm oil, as a result of large amount of hydrogen-transfer, cyclization and aromatization reactions, Additionally, most of properties of produced gasoline and diesel oil fuel meet the requirements of national standards, containing little sulfur. So TSRFCC technology is thought to be an alternative processing technology leading to production of clean fuels and light olefins.     

A study of the caustic refining of vegetable oils

Summary In the caustic refining of vegetable oils using liquid-mixing the concentration of caustic solution required, the amount of excess caustic used, the length of time of mixing the oil-soapstock mixture in the cold, and the oil content of the soapstock are governed by the amount and kinds of phosphatides present in the oil. In the mist-mixing process of refining vegetable oils using caustic, the mixing time is kept constant, the concentration of the caustic is kept constant for a particular kind or type of oil, the excess caustic is kept constant for a particular kind or type of oil, and the oil content of the soapstock is governed by the amount and kinds of phosphatides present in the oil, and by the use of sodium silicate.     

Determination of ultratrace metals in hydrogenated vegetable oils and fats

Ultratrace levels of nickel, chromium, copper and iron occurring in hydrogenated vegetable oil products were estimated by dispersion of the samples in 4 methyl-2-pentanone and atomic absorption analysis by the graphite furnace technique. The principal goals in establishing the analytical methods were improved sensitivity to metals at low levels and applicability to limited amounts of products. Using reproducibility and linearity of response as criteria, optimum oil concentration in solvent and instrument parameters were established. For a series of commercial products, the method of standard addi-tions was adopted to correct for matrix differences between the products and salad oil-based standards. The range for the metals was determined in five cooking oils: Ni, 29–207 ppb; Cr, 1–5 ppb; Cu, 13–37 ppb; and Fe, 138–301 ppb; in recovered oils from five margarines: Ni, 34–70 ppb; Cr, 2–12 ppb; Cu, 26–58 ppb; and Fe, 239–540 ppb; and in five solid shortenings: Ni, 592–2772 ppb; Cr, 8–35 ppb; Cu, 26–108 ppb.     

Optical activity of lactones from animal and vegetable fats

The isolation of optically active lactones from animal and vegetable fats is described. As the optical activity of lactones isolated from butterfat is ascribed to their biological origin, special attention was paid to the optical purity of the lactones. Lactone mixtures from butterfat, goat milk fat and coconut oil were found to be dextrorotatory, those from babassu oil levorotatory. The total lactone mixtures of two out of three samples of palm-kernel oil were slightly dextro-, whereas that of the third one was levorotatory. After isolation of the individual lactones from the mixtures, levo- and dextrorotatory lactones were demonstrated side by side in palm-kernel oil and in coconut oil. The δ-lactones of palmkernel oil were levo-, the γ-isomers dextrorotatory. In coconut oil only the δ-C₁₂ lactone was levorotatory, whereas the other components of the δ-series were dextrorotatory. The specific rotation [a] _d of the chemically pure lactones was considerably lower than that of model lactones, this being an indication of their optical impurity. As it was evident from model experiments that no racemization of the lactones occurred during isolation, it follows that both optical antipodes are formed in the fats in unequal amounts, via different pathways.     

Pretreatment of edible oils for physical refining

Physical refining of edible oils is briefly reviewed. Recent developments regarding the pretreatment of oils and fats are described in detail and methods are critically evaluated with special emphasis on their effectiveness in removing undesired minor components, their cost of operation and their effect on the environment.     

Chemical and physical effects of processing fats and oils

Soybean oil is processed for a variety of food uses, salad/cooking oil, margarine and shortening. Crude soybean oil is composed mainly of triglycerides but also contains measurable amounts of minor constituents that may have beneficial or detrimental effects on oil characteristics. The nature of these minor constituents, the role they play in oil stability or deterioration and their fate during processing are subjects of this review. Iodine value, fatty acid composition, solid fat index and congeal point are chemical and physical characteristics of oil that are affected by the hydrogenation process. Techniques and effects of degumming, alkali refining, bleaching, hydrogenation, winterization and deodorization are discussed. Utilization or disposal of by-products or wastes from each processing step is reviewed. Presented at Northeast Section, AOCS, Symposium, Newark, N.J., November 5–6, 1979.     

Determination of the glyceride structure of fats; analysis of 14 animal and vegetable fats

The glyceride compositions of seven animals and seven vegetable fats have been determined by GLC analysis of the oxidized esterified glycerides as described in an earlier paper in this series. The compositions determined are compared with those calculated from lipase hydrolysis data according to the method of VanderWal. Good agreement was found between the calculated and determined compositions for the majority of the 14 fats. The exceptions were human fat and the more satu-rated vegetable fats, palm oil and cocoa butter, where some discrepancies occurred. Issued as NRC No. 8052. National Research Council of Canada Postdoctorate Fellow.     

Catalytic chemistry of preparation of hydrocarbon fuels from vegetable oils and fats

The problem of preparing engine fuels from renewable feedstocks via the catalytic processing of inedible vegetable oils and fats is considered. Different types of inedible feedstocks are described, including algae, inedible plants, wood processing products, and waste fats and oils. Catalytic processes are considered for preparing the second generation biodiesel through the hydrodeoxygenation and deoxygenation of triglycerides and fatty acids, and of their derivatives. Brief information on catalysts for the deoxygenation of fatty acids is given. Special attention is given to analyzing the mechanism and kinetics of the deoxygenation reaction. Based on conducted kinetic and quantum-chemical investigations and using the literature data, a deoxygenation mechanism is proposed by the authors that explains the observed dependences of decarboxylation and decarbonylation contributions on the reaction conditions (the stearic acid, water, and catalyst concentrations, the hydrogen and CO pressures, and the temperature). Examples of the application of hydrocarbon biodiesel in transport are presented.     

A study of the antioxidant effectiveness of several compounds on vegetable fats and oils

Summary 1. A number of compounds and combinations of compounds have been examined for antioxidant properties. 2. The most effective single compound was gallic acid, although NDGA, ascorbic acid and ascorbyl palmitate each about doubled the keeping time of any given vegetable fat or oil. 3. Amino acids were negative with the exception of methionine. 4. NDGA in combination with either citric acid or phosphoric acid showed marked synergism. These combinations were very effective antioxidants. The work described in this paper was carried out under a contract, recommended by the Committee on Medical Research, between the Office of Scientific Research and Development and the University of Pittsburgh. Contribution No. 519 from the Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania.     

The specific and latent heats of fusion of some vegetable fats and oils

Summary The specific heats of several vegetable oils have been determined by a more exact procedure than those which seem to have been used heretofore. Values slightly higher than the literature figures were obtained, that is, an average value of 0.53 was determined as compared to reported results of 0.50. The specific heat of cottonseed oil with respect to temperature increases slightly with elevating temperatures. The specific heats at different temperatures were not determined on the other oils, but likewise, these probably show no significant variation in specific heat with respect to temperature in the range 21° to 100°C. The specific heats of completely solid vegetable fats are believed to be reported for the first time. These values are about the same for such different stocks as completely hardened palm and sunflower oils, and their values are approximately one-half that of the liquid, that is, 0.28 as compared to 0.53. The latent heats of fusion of a number of fats have also been determined by what is thought to be a satisfactory procedure. Theoretical aspects and empirical results are given to show that the latent heat of fusion varies with the temperature when two phases are present, and that for this reason, any references to the latent heat of fusion should be accompanied by temperature limitations. This is not so important, however, when the specimen is completely solid at the temperature in question. The data and graphs presented show the general variation in latent heat of hardened cottonseed oil at one temperature with respect to iodine value.     

Use of the multistage countercurrent contactor for degumming and refining of vegetable oils

Conclusions Duozon centrifugal contactors seem to have the following advantages in the refining of glyceride oils: decreased losses and increased yields of products; large capacity in a single machine resulting in low first cost, reduced requirement for floor space, and simple flow and installation; because of comparatively low speed, low maintenance cost and low power requirement; practically automatic operation; continuous operation unhampered by particles of meal in the charge; and an entirely enclosed system, allowing no oxidation of hot oil. Presented before the American Oil Chemists’ Society, Houston, Tex., April 23, 1956.     

Detection of refined animal and vegetable fats in adulteration of pure milkfat

The objective of this research was to evaluate the presence of dehydroxylated sterols in samples of butter adulterated with exogenous refined fat of both animal and vegetable origin. The 3,5-cholestadiene, derived from the refining treatment, was found to be an index for the addition of refined beef tallow to butter. Moreover, several dehydroxylated phytosterols could be detected in butter adulterated with vegetable oil. The proposed method seemed to be a suitable criterion for detecting adulteration of pure butter with other fats.