Laboratory Deodorizer for Fats and Oils J
A. E. BAILEY AND R. 0. FEUGE Southern Regional Research Laboratory, Bureau of Agricultural Chemistry and Engineering, New Orleans, La.
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TEAM deodorization is one of the fundamental processes in edible oil and fat technology and is practiced commercially on a very wide scale. It is, however, a relatively troublesome operation to conduct in the laboratory. The operation involves blowing a heated batch of oil with steam under reduced pressure. Because the pressure required for the best operation is somewhat below the vapor pressure of water at ordinary temperatures, it is somewhat difficult to maintain vacuum upon the system. Multiplestage steam ejectors such as are used commercially are not practicable for laboratory use. Mechanical oil-sealed vacuum pumps are not generally used because of the difficulties involved in completely condensing and trapping relatively large amounts of water vapor. Water ejectors operating on ice water or cooled brine are effective, but considerable auxiliary equipment is required for the constant delivery of large quantities of a cold liquid a t high pressure.
During the deodorizing operation, steam must be delivered to the apparatus at a constant and easily controllable rate. The generation and delivery of the steam also present some difficulty and require the use of a steam generator of special and usually rather elaborate design. The laboratory deodorizer described here is greatly simplified, in comparison with the conventional apparatus. It should be of particular interest to oil and fat laboratories which have only limited or occasional use for such equipment, and consequently have hesitated to devote space and funds to the usual deodorization setup. The entire apparatus, including the steam generator, is made of Pyrex, and may be fabricated by a glassblower of average ability. Vacuum for the apparatus is supplied by an ordinary rotary oil-sealed Pump. The aistinctive feature of the apparatus, and the one which makes possible its simple design, is the relatively high
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FIGURE 1 . DIAGRAM OF APPARATUS 280
SPHERICAL JOINT
April 15, 1943
ANALYTICAL EDITION
vacuum under which it operates-namely, about 1 mm. of mercury, instead of the usual 5 to 10 mm. under which most installations operate. Since steam requirements in deodorization are directly proportional to the total pressure ( I ) , the amount of steam which must be generated and condensed is extremely small. This condition permits the use of a steam generator of novel design, and makes i t feasible t o condense all vapors in simple dry ice traps. All volatile substances removed from the oil are quantitatively recovered in the condensers. The apparatus is useful for certain high-vacuum steam-distillation work other than deodorization and has been successfully used t o reduce the free fatty acid content of crude vegetable oils, to strip out unreacted glycerol or free fatty acids after re-esterification reactions, and to separate degradation products from heattreated oils. The apparatus is illustrated in Figure 1. It is composed entirely of small Pyrex units equipped with standard groundglass joints which permit the use of duplicate units in the original assembly. Spherical joints at certain points lend flexibility and make the apparatus easy to assemble. The round joints may be lubricated with the oil or fat which is to be jeodorized. The steam generator, G, consists of two bulbs connected by capillary tubing. One bulb serves as a water reservoir. The other bulb is partially filled with asbestos, the top layer of which is covered with a film of carbon black, to enhance the absorption of heat. The carbon coating is conveniently applied to the asbestos by suspending a quantity of carbon in water and dropping the suspension on the asbestos surface from a pipet, while maintaining suction on the opposite end of the system. The rate a t which water is admitted from the reservoir and a t which steam is generated is easily controlled by the grooved stopcock between the two bulbs. Heat necessary to generate the steam by evaporation from the surface of the asbestos is supplied by a 250-watt infrared lamp, H . For critical work the water in the reservoir may be boiled to remove dissolved oxygen and then kept in an oxygen-free atmosphere by means of a hydrogen- or nitrogenfilled expansion bulb connected to the reservoir outlet. The steam delivery tube, D, is provided with a fritted-glass tip to distribute the steam flow. The flask, F , which contains the oil to be deodorized, is fabricated from a Claisen-type distilling flask, and may be of any desired capacity within the range of about 1 to 3 liters. The flask is preferably heated by means of an oil bath, B, with the
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thermometer, T,indicating the temperature of the bath. A good deodorization rate is attained a t temperatures of 425" to 475" F. (218" to 246" C.). If the ap aratus is to be used for any urpose where it is important to [now the exact temperature orthe contents of the flask, a thermometer or thermocouple well should be inserted through a ground-glass joint directly into the body of the flask. The spray trap, A , may be insulated or provided with an electrical resistance heater to prevent excessive reflux when stripping large quantities of fatty acids or other volatile constituents from the oil. Pressure on the system is indicated by the manometer, M , which is connected to the spray trap by means of heavy rubber tubing. It is essential that all vapor passages be made large, as indicated in Figure 1, to avoid an appreciable pressure gradient through the apparatus. Condensers C and C' are cooled with a dry ice-acetone mixture or with powdered dry ice. Single-hole rubber stoppers serve to keep warm air away from the interior of the condensers and permit the escape of gaseous carbon dioxide. A single charge of dry ice will generally suffice for a deodorization. The dry ice is well insulated from the warm air of the room by the evacuated space surrounding the inner shell of each condenser. It will be found that practically all vapors from the flask will be retained in the first condenser. The second condenser functions largely as a safety device, to protect the pump in the case of accidental failure of the first condenser. The proper sequence of operations in starting the deodorization operation is more or less obvious. After the apparatus is charged with oil, water, and dry ice, the vacuum pump is started, the heating lamp is turned on, the stopcock of the steam generator is gradually opened until the desired rate of steam generation is attained, and the oil bath is then heated to the operating temperature. After deodorization is completed (usually 30 to 60 minutes), the hot oil bath is removed. The flask is then cooled by cold oil, a current of cool air, or other means, until the deodorized oil has reached a temperature of 100" to 150' F. (38" to 66" C,). The stopcocks leading to the manometer and the water reservoir are then closed, the manometer is disconnected, the vacuum pump is stopped, and vacuum on the system is broken by cautiously and simultaneously opening the stopcocks leading to A and D. This procedure avoids drawing oil back into the steam generator or blowing excessive quantities of air through the deodorized oil.
Literature Cited (1) Bailey, A. E., IRD. ENG.CHEM.,33, 404-8 (1941).
Mayonnaise and Salad Dressing Yolk Content FRANK J. CAHN AND ALBERT K. EPSTEIN, The Emulsol Corporation, Chicago, Ill.
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HE circulation in commerce of liquid and frozen egg
yolk products varying in egg yolk solids content, and, more particularly, the recent promulgation of a definition and standard of identity for "egg yolk" by the Food and Drug Administration ( 2 ) , call for a reconsideration of the analysis for "egg yolk" of such food products as mayonnaise and salad dressing. The Association of Official Agricultural Chemists (1) gives an equation which expresses the per cent of yolk in t h e sample as a function of the per cent of nitrogen and the per cent of phosphorus pentoxide. 70 yolk = 75.69 P - 1.802 N (1) when P equals per cent of total phosphorus pentoxide and N equals per cent of total nitrogen. The per cent of egg yolk calculated from this equation is in terms of egg yolk having a total solids content of 50.5 per cent. Such a yolk can be prepared in t h e laboratory only and has been called "theoretical" yolk. Commercially produced egg yolk material contains various proportions of adhering egg white and has, therefore, a total solids content substantially below 50.5
per cent. The equation and other directions of the Aasociation of Official Agricultural Chemists (1) do not give sufficient data t o enable one to express the analytical results in terms of commercial yolk, and do not indicate t h a t t h e percentage of yolk content calculated by the equation is the percentage of yolk of 50.5 per cent solids content. How much egg white is admixed with the 50.5 per cent yolk in a commercial yolk depends on the definition of the commercial yolk; as defined by the provisions and regulations of the Federal Food, Drug and Cosmetic Act of 1938 (2), commercial yolk contains 43 per cent total solids. This 43 per cent commercial yolk can be considered t o be a mixture of 80.42 parts of yolk of 50.5 per cent solids content and 19.58parts of white of 12.2 per cent solids content. I n this discussion, as \\-ell as in the publications of the Association of Official Agricultural Chemists, i t is assumed that all nitrogen and phosphorus pentoxide determined by an analysis of the mayonnaise or salad dressing are derived from egg yolk and egg white only (5). Because of the need for determining the content of commercial yolk in salad dressing or other food products, the
