Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/001—Refining fats or fatty oils by a combination of two or more of the means hereafter
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/12—Refining fats or fatty oils by distillation
  • C11B3/14—Refining fats or fatty oils by distillation with the use of indifferent gases or vapours, e.g. steam

Definitions

• the invention relates to a process for deodorizing oils and fats.
• oil has a wide meaning and includes any fatty liquids of vegetal or animal origin.
• the deodorizing stage is one of the most important in the process of refining oils, because it has the greatest impact on the quality of the oil or fat substance being refined and it gives the products the desired organoleptic characteristics. Since deodorizing is part of the refining process, it is proper to refer to said process in this description.
• oils are natural products of vegetal origin (seeds and oily fruits) or animal origin (fatty tissues, organs, etc.) that present a complex nature.
• oils are formed by glycerides, that is, glycerine esters with fatty acids (acids with a straight chain and between 12 and 24 carbon atoms, except for a few cases). Because the esterification is a revers­ible reaction, the oils contain not only triglycerides but also mono- and diglycerides formed by the action of certain enzymes, oxidizing processes, etc. that produce the hydroly­sis of these triglycerides. This results in the formation of mono- and diglycerides, as well as free fatty acids.
• the oils contain a number of other components.
• Some of these components such as the tocoferols, sterols, carotenes, etc., due to their antioxidizing, provitaminic, etc., prop­erties, are beneficial while others, such as the free fatty acids, phospholipids, trace metals, humidity, etc., are harmful and must be eliminated.
• Refining is a necessary process in order to reduce to a minimum all the oil contaminants which adversely affect its final quality and negatively impact on the efficiency of the operations - some of them necessary - of fraction­ing, transesterification and hydrogenation.
• the refining also makes the oil capable of being used as a food or for other industrial applications.
• the refining process can be accomplished by a number of systems, although most of them are no longer in use. Practically, only the so-called traditional or chemical refining and the physical refining processes are used. Hereinafter there is a schematic diagram identifying the differences between both types.
• the main purpose of neutralization is to separate the free fatty acids naturally present in the crude oils.
• neutralization systems There are various neutralization systems, although the most com severelymonly used are the neutralization with caustic alkalies and the neutralizing distillation.
• the object of scouring is to remove the traces of soap that might have dissolved in the oil. It allows the separation of all alkaline substances (excess soaps and caustic soda) present in the oil, as well as trace metals, phospholipids and other impurities.
• the water used for scouring should be at a temperature of approximately 90oC and is used in a ratio that varies from 10 to 15%.
• the object of the deodorization stage is to eliminate the substances that give bad odor and taste to the oils. Some of these substances have been identified as ketones, aldehydes, carbohydrates, terpenes, alcohols of very different molecular weight and volatility (most of them come from the oxidation and degradation of the fatty acids), etc.
• the main difference between the traditional or chemical refining process and the physical refining process is that, in the former, the fatty acids are eliminated as soaps or pastes by means of an alkali during the neutralization stage, carrying with them other compounds or impurities such as phosphatides, trace metals, pigments, etc. and requiring less drastic decoloration conditions.
• the pretreatment stages prior to the neutralizing deodorization stage must be performed under more energetic conditions.
• the process consists of the following stages: degumming, decoloration and neutralizing deodorization.
• This process is analogous to that performed during the traditional refining of the oils, with the exception that, in this case, it is a very long and energetic process in order to reduce the phospholipids content to a value of less than 0.2%.
• the decoloration is performed in a similar manner as for chemical refining.
• the only difference is a greater consumption of decoloring earths due to the more energetic pretreatment required by the oil before undergoing the neutralizing deodorization process.
• the physical refining process in itself, consists of a distillation using steam to entrain the free fatty acids, as well as all those volatile substances that accompany oils and give them their typical odor and taste and to destroy the thermolabile pigments.
• the oil once degummed and decolored, passes to an aerator.
• the oil previously heated, is then introduced in the deodorizer where it is subject to an injected countercurrent of steam and remains under vacuum conditions and at an approximate temperature of 275oC.
• both refining processes include a deodorization stage, where the substances that give the oils bad odor and taste are removed.
• the removal of these substances is accomplished by the action of a countercurrent of dry steam under vacuum conditions and at a high temperature.
• the deodorization is possible under these conditions due to the large volatility difference between the triglycerides and the substances that give the oils the odor and taste.
• the vapour pressure of these compounds is so extremely low that a very high temperature would be required in order to remove them under atmospheric pressure conditions.
• the deodorization is accomplished more efficiently by combining the vacuum with steam entrainment.
• the distillation starts when the sum of the partial pressures of the vapour and of the volatile compounds reaches the pressure that exists on the oil surface. This occurs at a temperature lower than without the steam.
• the steam In order to obtain the maximum efficiency of the deodorization process, the steam must be injected in the oil in such a manner that a large number of small bubbles are formed with a very large surface in relation to their weight. In experiments, it has been observed that the saturation of the steam bubbles is so fast that it can be considered as complete at absolute pressures of ap­proximately 8 mbars.
• a deodorizing station consists of the following unit: -Deodorizing device -Oil heating system -Vacuum system -Steam generator for producing the necessary steam flow. -Condenser for volatile products -Oil coolers
• deodorizing facilities There is a wide variety of deodorizing facilities, which may be classified as discontinuous, semicontinuous and continuous. No greater details thereof will be given here.
• the oils undergo a partial decoloration due to the loss of color of certain pigments at high temperature.
• the degree of decoloration depends on the previous bleaching pretreatment and the nature of the oil.
• oils lose the natural antioxidizers during their deodorization, which increase their tendency to become oxidized.
• the purpose of this invention is to provide an oil deodorization process that will eliminate the above mentioned drawbacks.
• the deodorization is achieved through a process characterized in that the oil to be deodorized is subjected to the action of an inert gas flow, preferably nitrogen, which will carry away the substances that impart bad odor and taste to the oil.
• an inert gas flow preferably nitrogen
• the process takes place under vacuum conditions with pressures between 1 and 8 mbars, and at temperatures between 60oC and 270oC.
• the oil to be deodorized has been subjected to a prior degumming, decoloration, neu­tralization and/or deaeration process.
• the inert gas is dispersed within the oil being deodorized, which results in a very good diffusion or distribution of the nitrogen throughout the oil mass.
• the optimum inert gas flow value is preferably between 0.8 and 3 Nm3/hour per tonne of oil.
• the process is also applicable to installations for continuous flow.
• the raw material was olive oil, neutralized with caustic soda and decolored with Gador C earth. Its content of unsaponifiable compounds was 1.24%.
• the steam generated in a container by the heat of a hot plate is injected in a deodorizing flask.
• the nitrogen from a pressurized vessel is used as the carrier fluid in this process, with the effective diffusion being regulated by a porous device and a flow control valve with its corresponding flowmeter.
• the control for the different tests was the amount of unsaponifiables in the oil and the organoleptic properties of the corresponding refined oils. Table I shows the average data for three such tests.
• the purification was accomplished heating the oil to 70oC and adding to it a solution of 2/1000 of phosphoric acid and 4/1000 of water. The oil was stirred during 20 minutes and was then allowed to decant. The precipitate thus formed was then separated. A sample of the oil was taken and its acidity determined to proceed with the neu­tralization of both the free fatty acids and the residual mineral acid.
• the oil was heated again to 70oC and the amount of 18o Bé caustic soda required to neutralize the acidity, plus an excess of 10% was added to the oil.
• the oil was then stirred during 20 minutes, the pastes were separated by decantation and the oil was scoured with hot water. These scouring operations were repeated until the wash waters did not show any alkaline reaction.
• Oil No 1 produced a refined product with acceptable almondlike organoleptic characteristics, both with steam and with nitrogen processes.
• Oil No 2 produced in both cases (with steam and with nitrogen) an acceptable refined product with a very slight taste reminiscent of "Pickled olive” oils.
• the content of polar compounds was determined for the refined oils. It was observed that the percentages of altered triglycerides, dimers and oxidized compounds were lower than when nitrogen was used, except in the tests at 270oC where there were similar percentages of altered triglycerides and dimers due to the high temperature. The amount of diglycerides was always lower when nitrogen was used.
• Example 1 The method described for Example 1 was applied to a sunflower oil under the following conditions: Pressure: 4 mbars; Time: 3 hours; Steam or nitrogen flowrate: 30 ml/min.; Temperature: 180o and 220oC. All the tests produced refined oils with the quality and characteristics of refined seed oils.
• Soy bean oil was used which, as the sunflower oil, is more sensitive to the refining conditions because of its higher content of unsaturated fats.
• the conditions were the same as for the previous example and the results were similar to those obtained with sunflower oil.
• the deodorised oil exhibited a significant decoloration.
• the oil was heated to 35-40°C, with nitrogen gas flowing from the beginning of the test. Phosphoric acid was then added with stirring in a ratio of 2:1000. The stirring was maintained until the mixture reached a temperature of 60oC. A 4% volume of an aqueous 5% sodium chloride solution was added and the stirring was suspended. A 6% volume of water was added, the solution was stirred and the oil was separated from the aqueous phase by decanting. All these operations were performed in a nitrogen atmosphere.
• the oil was heated to 60oC and a soda solution of 24o Bé was added in sufficient quantity (with a 20% excess) to neutralize the acidity of the oil plus the remaining mineral acidity from the phosphoric acid that was previously added.
• the mixture was maintained with stirring under a nitrogen atmosphere at 60oC during 30 minutes. After this time, the stirring was stopped and a 25% volume of hot water was added; the mixture was stirred again during 10 minutes. After this time, the stirring was stopped and the solution was allowed to rest until it could be properly de­canted (usually from 15 to 20 minutes). The aqueous phase was then separated.
• the oil was dried to eliminate any humidity remaining from the washing operations. For this purpose, the oil was heated to 60oC, under vacuum and a flow of nitrogen gas. Once the oil was dry, 1.5% of decoloring earth (Gador Type C) was added, as well as 0.2% of activated carbon (Ceca Type AG). The oil was held 60oC under stirring during 20 minutes and then filtered.
• decoloring earth Gador Type C
• activated carbon Ceca Type AG
• the oil once decolored, had a very good appearance but it still had the characteristic smell of fish oils. To solve this problem, the oil was subjected to a gentle deodorization. Given the tendency of these oils to polymerize at high temperatures, and since this tendency is more marked in the most important fatty acids (eicosapen­tanoic and docosahexanoic), the conditions of time and temperature were studied with more attention. Temperature steps between 60oC and 110oC were evaluated (because higher temperatures would produce polymerization), and time intervals between 60 and 240 minutes. The control of the tests was based on the iodine numbers and the organoleptic characteristics. From the results thus obtained, the conclusion was reached that it was possible to achieve acceptable products, without eliminating the characteristic odor and taste of fish oils, by using temperatures between 80oC and 90oC and a time period of 2 hours. Polymers would appear if the conditions were more extreme.
• the refined oils had the characteristic almondlike taste of refined olive oils of quite good quality, both for the steam and the nitrogen tests.
• the tests at 180oC it was noted for both cases (steam and nitrogen) that not enough deodorization time had been allowed.
• Another test was per­formed at this temperature but with a time period of 4 hours. This test produced a good quality refined oil.
• Example 5 Using the same conditions as for Example 5 and degummed, neutralized and decolored sunflower oils, two tests were performed at 180oC and 210oC. Excellent results were obtained, with both steam and nitrogen.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Microbiology (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Fats And Perfumes (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=8262802

Family Applications (1)

Country Status (8)

Cited By (12)

Families Citing this family (1)

Family Cites Families (5)

• 1989
  • 1989-06-29 ES ES8902284A patent/ES2013206A6/es not_active Expired - Lifetime
• 1990
  • 1990-05-16 IT IT20317A patent/IT1241140B/it active IP Right Grant
  • 1990-05-16 PT PT94056A patent/PT94056A/pt unknown
  • 1990-06-27 CA CA002019916A patent/CA2019916A1/fr not_active Abandoned
  • 1990-06-29 EP EP19900112499 patent/EP0405601A3/en not_active Withdrawn
  • 1990-06-29 BR BR909003055A patent/BR9003055A/pt not_active Application Discontinuation
  • 1990-06-29 IE IE236390A patent/IE902363A1/en unknown
  • 1990-06-29 JP JP2172555A patent/JPH03263498A/ja active Pending

Also Published As

Similar Documents

Legal Events