Bleaching of edible fats and oils

Almost all fats and oils are subjected to so‐called bleaching during processing. Originally bleaching was only used to reduce the colour. Today, however, the bleaching step is used mainly to remove or convert undesired by‐products to harmless ones from fats and oils. This will guarantee that such compounds do not interfere with the processing and that the requirements for human food are being met.     

The solubility of water in edible oils and fats

The solubilities of water in rapeseed oil, coconut oil, and a palm-coconut oil mixture were determined at temperatures of 60C, 80C, and 100C. Oil samples were equilibrated with water vapor under conditions of constant temperature and humidity. The equilibrium water content was determined by means of the Karl Fischer titration method. The solubility was found to be independent of the type of oil when expressed in terms of the mole fraction. An equation relating solubility and temperature is given.     

Fractionation and winterization of edible fats and oils

Processes for fractionation and winterization are reviewed. Properties of solid and liquid fractions from various fats and oils are discussed. In view of the current interest in palm oil, the operation and economics of a small palm oil processing plant including fractionation are described.     

Spectrophotometric determination of BHA in edible fats and oils

A method is described for the analysis of 2- and 3-tert-butyl-4-hydroxyanisole (BHA) in edible fats and oils. The method is based on measurement of a specific color developed from the reaction of BHA with NN-dimethyl-p-phenylenediamine in the presence of a mild oxidizing agent in alkaline solution. The purple-violet color developed is extracted in carbon tetrachloride, and the absorbance is measured at 550 nm. The presence of other antioxidants also was examined, and the method was applied to various foodstuffs (e.g. olive oil, lard and butter). It gave satisfactory results. The detection limit was 0.4 ppm of BHA.     

Estimation of conjugated octadecatrienes in edible fats and oils

Interest in conjugated-diene fatty acids in foods has recently been increased by discovery of their antioxidant and anticarcinogenic properties. Conjugated octadecatrienes (COTs), members of another group of fatty acids, are also present in foods. COTs are formed during the processing of vegetable oils as the result of the dehydration of secondary oxidation products of linoleic acid. Little information is available concerning the occurrence and nutritional properties of COTs in edible oils. Levels of COTs, determined in 27 vegetable oils by ultraviolet (UV) spectroscopy, ranged from not detected (<0.001) to 0.2%. Determination of COTs by gas chromatography of the methyl esters, obtained by transesterification at room temperature with sodium methoxide/methanol, gave lower levels (not detected, 0.051%) than did determination by UV spectroscopy. Methylation with boron trifluoride produced COTs from naturally occurring moieties in the oils and, therefore, is not recommended.     

Refining and degumming systems for edible fats and oils

Crude edible fats and oils contain variable amounts of nonglyceride impurities, such as free fatty acids, non-fatty materials generally classified as “gums”, and color pigments. Most of these impurities are detrimental to end product fresh and aged quality characteristics, hence must be eliminated by a purification process before the finished fats and oils are suitable for human consumption. The object of this process is to remove these objectionable impurities with the least possible loss of neutral oil and tocopherals. Key theoretical and practical factors for degumming and refining crude edible oils are discussed with particular reference to processes, flow charts, control systems and analytical testing requirements. In addition to typical large volume oils, such as soya and cotton, techniques are also reviewed for smaller volume oils, including palm, lauric and corm.     

The solubility of water in edible oils and fats above 100 C

The solubilities of water in rapeseed and coconut oils have been determined at temperatures between 90 and 160 C. Oil samples were equilibrated with water vapor under conditions of constant temperature and humidity. The equilibrium water content was determined by means of the Karl Fischer titration method. Solubility was found to be independent of the type of oil when expressed in terms of the mole fraction, in agreement with previous work at temperatures below 100 C. An equation is given relating solubility and temperature between 0–250 C.     

Stability of edible oils and fats to fluorescent light irradiation

Butter, butterfat, and corn, coconut, rapeseed, and soybean oils were exposed to 500 ft-c of fluorescent light at varying time-temperature conditions. Oxidation rates were measured by the peroxide values. Vitamin A and β-carotene content of butterfat were estimated. The effect of wavelength on the relative rates of oxidation was determined. The light transmitting properties of the samples at 15 and 30 C over a spectral range of 380–750 nm were measured. It was observed that there was no increase in oxidation rate when the light was switched off. The stability of the oils as shown by the oxidation rates did not correlate well with the ratios of C18:2 to C18:1 or C18:3 to C18:2 nor with the degree of unsaturation. Increase in temperature alone had minimal effect; however, in the presence of light the rate of oxidation increased considerably with a corresponding decrease in the content of Vitamin A and β-carotene. β-Carotene provided strong protective properties. After the photobleaching of β-carotene in butterfat, there was a rapid increase in peroxide values. With coconut oil, the oxidation rate was greater at 15 C than at 30 C due to greater light absorption at 15 C over the entire spectrum. The rate of oxidation decreased at higher wavelengths, and this effect was more pronounced in the vegetable oils than in butterfat, where the β-carotene was considered to serve as a filter for light of low wavelength. Presented at the AOCS meeting, Dallas, April 1975.     

Metal analysis of edible fats and oils by atomic absorption spectrophotometry

Enrichment procedures for trace metal analysis by atomic absorption spectrophotometry have been investigated. The detection limits are primarily determined by the enrichment factor and the accuracies have been found to be roughly the same within the same absorption ranges independent of the method used. One of 28 papers presented at the Symposium, “Metal-Catalyzed Lipid Oxidation,” ISF-AOCS World Congress, Chicago, September 1970.     

废弃食用油脂运用活性凹凸棒土脱色的试验研究

因为废弃食用油脂直接采用超临界法制备生物柴油的外观品质很差,所以本文选用活性凹凸棒土对废弃食用油脂进行预处理脱色研究,对影响废弃食用油脂脱色率的因素进行了讨论。得出活性凹凸棒土对废弃食用油脂脱色的最佳条件:活性凹凸棒土质量分数15%,初始脱色温度60℃,终止脱色温度110℃,脱色时间20m in,凹凸棒土投放次数为1次,搅拌速度350 r/m in。     

Determination of BHA,BHT and TBHQ in edible fats and oils

A method is described for the rapid analysis of the phenolic antioxidants BHA, BHT and TBHQ in edible fats and oils. The procedure is based on gel permeation chromatography with UV detection, and requires no preliminary isolation of the antioxidants from the matrix. Detection limits with the instrumentation used in this study were<1 ppm for BHA and BHT, and ca. 20 ppm for TBHQ.     

Characterization of semisolid fats and edible oils by Fourier transform infrared photoacoustic spectroscopy

The potential of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) for the analysis of semisolid fat and edible oil was demonstrated with butter, soybean oil, and lard as representative materials. Results of Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy analysis was compared with FTIR-PAS results. The PAS technique is simple and requires no sample preparation unlike ATR. Optimal PAS instrumental parameters for obtaining quality spectra are a scanning speed of 5 kHz, number of scans of 256 scans/sample, and a resolution of 4 cm⁻¹. The PAS spectra of soybean oil and lard are similar because they have similar functional groups. Results for soybean oil compare well with those available in the literature. The ATR spectra of butter were better than those from its PAS counterpart. Functional groups corresponding to vibration mode and intensity are provided for soybean oil and lard.