Interesterification of edible fats

Journal of the American Oil Chemists' Society -     

Improvement of keeping quality of edible fats by some commercially available tannins

Summary The literature on the use of tannins as antioxidants for fats is reviewed. A process is described for the improvement of the keeping quality of edible fats by treatment with tannin in which the tannin and/or tannin compound is removed by filtration. Data are presented for various types of animal and vegetable fats and oils which were treated with U.S.P. tannic acid by the process described. The process is particularly effective on lard and beef fats. Data are presented which show the effects of varying the temperature at which the treatment is made. A method for testing the effectiveness of removal of the tannin is described. The improvement value I_v, is introduced and is defined as the increase in keeping quality of a fat attributable to a process. It is analogous to the I_A value which is defined as the increase in induction period of a fat due to the addition of an antioxidant. A paper presented at the A.O.C.S. Fall Convention at Chicago, Nov. 7–9, 1945. Part of the data were presented at the Conference on Problems Related to Fat Deterioration in Foods under the auspices of Committee of Food Research, Research and Development Branch, Military Training Division, Office of the Quartermaster General in Washington in June 1945.     

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.     

Production of specialty edible fats

Journal of the American Oil Chemists' Society -     

The purification of edible oils and fats

Originally, oils were not refined but with the introduction of solvent extraction, refining became necessary. Crude cottonseed oil was refined by treating the oil with caustic soda and the same process was used for all other oils that needed refining. The subsequent introduction of centrifugal separators converted the original batch process into a continuous process. Degumming was introduced to obtain lecithin but limited to soya bean oil. Physical refining was introduced for high acidity oils like palm oil after the oil had been degummed to low residual phosphorus levels in the dry degumming process, in which the oil is first of all treated with an acid and then with bleaching earth. In Europe, further degumming processes were developed that allowed seed oil to be physically refined and later phospholipase enzymes were introduced to reduce oil retention by the gums and improve oil yield. Given these various oil purification processes, the refiner must decide which process to use for which oil in which circumstances. The paper provides a survey of what to do and when. It also discusses several topics that require further investigation and development.     

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.     

Stabilization of edible animal fats during rendering

Summary Studies have shown that lard and edible beef fats can be stabilized effectively with phenolic antioxidants during pressure steam-rendering. Best results were obtained for a given stabilizer level with the individual phenolics butylated hydroxyanisole and butylated hydroxytoluene. Poorer results were obtained with the mixtures in propylene glycol.     

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.     

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.     

Composition and thermal properties of cattle fats

The physical‐chemical properties, fatty acid composition and thermal properties of cattle subcutaneous, tallow and intestinal fats were determined. Subcutaneous fat differed from the other fat types with respect to its lower melting point (29.0 °C) and higher saponification (211.4 mg KOH/g) and iodine (50.55) values. The cattle fat types contained palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1n‐9) and linoleic acid (18:2n‐6) as the major components of fatty acid composition (24.58–25.90%, 10.21–33.33%, 28.18–46.05%, 1.54–1.73%, respectively). A differential scanning calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major peaks (T_peak) of tallow and intestinal fats were similar and determined as 24.10–27.71 °C and 2.16–4.75 °C, respectively, for crystallization peaks and 7.09–9.39 °C and 43.28–46.49 °C, respectively, for melting peaks in DSC curves; however, those of subcutaneous fat (12.48 °C and –6.79 °C for crystallization peaks and 3.56 °C and 23.55 °C for melting peaks) differed remarkably from those of the other fat types.