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
  • C11B3/10—Refining fats or fatty oils by adsorption

Definitions

• the field of the invention is the refining of fat, particularly but non-exclusively the refining of vegetable butters.
• fats require purification in a refining process, to remove impurities and improve both the appearance and performance of the fat.
• taste also is improved by refining.
• the invention is particularly concerned with a class of fats known generally as vegetable butters from their relatively high melting characteristics, compared with the majority of fats from vegetable sources which are generally liquid at ambient temperatures and are usually described as vegetable oils.
• Oils and fats may be classified into two distinct groups differing markedly both in their properties and stability and require very different approaches in detail to refining processes applied to them.
• Those high in polyunsaturation, including linoleic and more highly unsaturated fatty acids, and prized accordingly for their dietetic value, may contain 40% or more of these acids in their glycerides, they are liquid at ambient temperature and are susceptible to the development of reversionary flavours after refining, owing to their susceptibility to oxidation arising from their high degree of unsaturation.
• high PUFA vegetable oils examples include soyabean containing 52% polyunsaturated fatty acids, cottonseed (53%), groundnut (32%), linseed (65% including no less than 53% of triunsaturated fatty acid), safflower (77%) and sunflower (64%). Marine oils are also notable for their high PUFA content.
• Examples of vegetable butters include cocobutter itself with only 4% linoleic acid, shea (10%), sal (2.8%) mango kernel (5%) and mowrah (up to 18%), with palm oil (10%). Although olive oil contains less combined saturated fatty acid, it is also less unsaturated than many vegetable oils.
• a miscella is made of the fat or oil in a suitable organic solvent, usually a hydrocarbon such as hexane, and the solution brought into contact with an appropriate adsorbent material of suitable particle size.
• a suitable organic solvent usually a hydrocarbon such as hexane
• the process necessitates removal of the solvent from the raffinate solution and is therefore expensive to operate.
• the cost of the process may also be prohibitively high if the effective life of the adsorbent is short.
• the removal of the small quantities of polar compounds present may have a dramatic effect, particularly on the melting characteristics of vegetable butters and is not readily achieved by alternative methods.
• the invention is particularly useful therefore in reducing the cost of achieving high quality fats for edible purposes such as chocolate manufacture and also for pharmaceutical application by enhancing the effective life of adsorbents used for producing such fats.
• USP 2,976,156 discloses a method of refining liquid vegetable oils by contact with alumina adsorbent in which it is recommended that bleaching treatment can be omitted.
• USP 3,955,004 discloses a similar process to that of USP 2,976,156 and in addition discloses as adsorbent mixtures of silica and alumina.
• the oils which include coconut, palm kernel and palm oil, are dissolved in a suitable solvent. After contact with the adsorbent, the refined oil is separated from the solvent and bleached.
• French Patent 990704 discloses bleaching a solution of glyceride oil and subjecting the solution to silica treatment. None of these references reveals the necessity for combining the application of adsorption and bleaching steps with regeneration as provided for by the present invention and applied to vegetable butters to be fractionated.
• USP 2,589,097 describes the removal of reversionary flavours from soyabean and similar highly unsaturated oils, which may first be bleached, using column adsorption treatment.
• European Patent Application 53016 published 2nd June 1982 describes refining sal fat by contact with a specially prepared particulate adsorbent in a column.
• This invention relates to fat refining, particularly but not exclusively to refining vegetable butters.
• Fats may be refined by contact, in a solution or miscella of a non-polar solvent, with an adsorption agent, usually packed in a column and based on silica and/or alumina activated by heat treatment.
• the adsorption agent selectively retains polar impurities, for example partial glycerides and colouring matter, and oxidised compounds which are highly polar, whereas the triglycerides constituting the principal components of the fats remain unabsorbed in a raffinate from which the purified fat is recovered by removing the solvent.
• the absorption agents become less effective with prolonged and/or repeated use, as polar compounds accumulate on them. Desorption of these polar compounds by treatment with polar solvents is incompletely effective with the more tenacious polar compounds absorbed from vegetable butters such as shea, sal and others.
• regeneration is facilitated by subjecting the fat or the fat miscella to pretreatment by contact with bleaching earth and/or active carbon, to adsorb the more highly polar compounds before treatment with the adsorption agent, preferably packed in a column through which the miscella is percolated.
• the less highly polar compounds, e.g. diglycerides, adsorbed by the adsorption agent may then be readily removed in a subsequent desorption step, e.g.
• the refined fat may be separated from the raffinate, for example by distilling off the non-polar solvent, or by fractional crystallisation, preferably to recover a fat fraction having a slip melting point of at least 35°C.
• lauric fats e.g. palm kernel and coconut oil
• triglycerides of the fats with which the invention is chiefly concerned are symmetrical, disaturated C,6/C,,3 triglycerides. Generally they contain less than 20% linoleic acid and, for the most part, not more than 10% and are low in polyunsaturated fatty acids generally.
• Such fats are usually expelled or extracted from tropical or sub-tropical fruit, either the fruit seeds or whole fruit. Although sometimes cultivated in plantations, as for palm oil, usually the fruit grows wild and is collected at irregular intervals in the forests after having fallen. Due to the prevailing elevated temperature and the moisture content of the earth, extensive enzymic reaction can occur, converting the natural triglycerides of the fats contained in the fruit seeds or in the pericarp by hydrolysis to mono- and diglycerides and free fatty acids. Other common reactions encountered in the fruit are hydroperoxidation, epoxidation and hydroxylation of the unsaturated fatty acid radicals contained in the triglycerides of the fat.
• the solvent in the fat miscella is preferably hexane or other inert aliphatic hydrocarbon compositions, preferably with a boiling point below 100°C to facilitate evaporation from the miscella without exposing the fat to excessively ' high temperatures.
• the fat in the miscella may be in crude form or undergo some preliminary refining beforehand, preferably neutralisation.
• Regeneration comprises desorption and reactivation, preferably effected in two steps.
• a polar organic solvent which preferably comprises a monohydric fatty alcohol containing up to 6 carbon atoms and particularly methanol, ethanol and isopropanol, and alcohol-hydrocarbon mixtures, preferably aliphatic, which may be miscible or immiscible, preferably azeotropic mixtures to facilitate removal from the regenerated adsorbent by evaporation.
• residual polar solvent e.g.
• methanol used for the desorption operation is driven out of the column by heating and preferably a volatile aliphatic hydrocarbon, e.g. hexane either in the vapour phase or as a superheated liquid.
• a volatile aliphatic hydrocarbon e.g. hexane either in the vapour phase or as a superheated liquid.
• the formation of azeotropic mixtures is also helpful in this case.
• the first step is called “desorption” and the second step “reactivation”.
• adsorption and desorption are preferably carried out at temperatures from 15 to 75°C, more preferably not in excesss of 60°C, but pretreatment in particular may be carried out at temperatures from 30 to 110°C and adsorption and desorption at 40 to 80°C.
• Adsorption is preferably effected in particular at 30 to 60°C, particularly approximately between 20 and 50%.
• Reactivation is preferably carried out between 50 to 170°C.
• Substantially less bleaching aid or active carbon is used in. the pre-treatment step than adsorption agent, from 0.5 to 5% by weight of the fat being adequate for the former, but with preferably a fat:adsorbent ratio from 10:1 to 1:1 by weight of the fat.
• both the pretreatment and adsorption steps are applied to the same solution of fat.
• Suitable bleaching earths for use in the invention include activated Fuller's earth, for example Tonsil and Fulmont, Lucilite, Kieselklare of Degussa. Granulated or non-granulated active carbon, e.g. Norit, may alternatively or in addition be used.
• Bleaching earths are usually acid-activated natural earths of structures typified by Montmorillonit and Bentonit. Acid treatment increases their propensity for adsorption of highly polar organic compounds including highly polar pigments, e.g. chlorophyll.
• These earths are not suitable for the adsorption of bulk amounts of diglycerides etc, but very useful in the preliminary treatment step for the removal of small amounts of highly polar organic compounds prior to the treatment of the fat with adsorbents like silica gel or AI 2 0 3 .
• These highly polar compounds otherwise prevent the regeneration of the adsorbents like silica gel and make their reuse difficult, if not impossible.
• Active carbon also adsorbs highly polar compounds both by surface adsorption (e.g. pigments etc) and also by X -electron interaction (e.g. aromatic compounds, polyene compounds, etc). All active carbons, both granulated and non-granulated, are suitable for this purpose and may be used in conjunction with bleaching earths.
• the adsorption agent may comprise silica gel, alumina or mixtures thereof including co-precipitates.
• aluminas include gibbsite and bayerite and among proprietary examples include Aluminiumoxid 504C.
• Suitable silica gels include Sorbsil of Messrs J Crosfield & Sons Limited, Warrington, England and Kieselgel-M of Messrs Herrmann, Cologne, Germany.
• adsorption is effected by percolating the miscella through a column packed with the adsorbent and with a length:diameter ratio of 5:1 to 1:2, particularly approximately equal diameter and length, with a residence time in the column of 5 to 30 minutes, especially 15 minutes.
• Adsorbents suitable for use in the process of the invention preferably exhibit a specific surface area of 300 to 500 m 2 /g, a pore volume of 0.7 to 1.5 mls/g, an average pore diameter of 30 to 2000 x 10-'°m, preferably 60 to 180 A, a weight:volume ratio of 0.2:0.5 g/ml and pH of 6.5 to 7.5.
• silica gel adsorbent used in this invention contains more than 95% Si0 2 with not more than approximately 4to 8% of volatiles removed at 140°C after 4 hours.
• Particle size by sieve analysis should preferably include not more than approximately 5% of 0.3 mm and not more than 25% of 0.2 mm.
• the silica was regenerated by washing in the column with isopropanol/hexane 20/80 mixture, removed from the column and dried at 160°C for 16 hours and reused as before, adopting the same quantity of fat each cycle.
• Particulars of the gel are as follows:-Specific surface area 450 m 2 /g, pore volume 0.73 mls/g, average pore diameter 60 x 10 -10 m weight:volume ratio 0.43 g/ml, pH 7.2, Si0 2 99.0%, volatiles as above 2.4%, sieve analysis 2% of 0.2 mm, 75% of 0.1 mm, 18% of 0.063 mm and 4.5% of 0.05 mm and 0.5% of 0.04 mm.
• the same fat and the same gel was used for a similar series of experiments in which the miscella pretreatment with bleaching earth and active carbon was omitted. After 5 regeneration cycles the eluate fats and the used silica gels were compared with each other.
• a solution in hexane of neutral illip6 fat was pretreated with bleaching earth and carbon as described in Example 1 and passed down a column 0.85 m in diameter, packed to a depth of 0.85 m with silica gel of the type "Sorbsil” from Messrs J Crosfield & Sons Ltd, Warrington, England, the weight of silica gel being the same weight as the fat.
• the spent silica column was then washed down at 80°C under pressure with an azeotrope mixture of isopropanol and hexane in a weight ratio of 22:78, to desorb and remove the material adsorbed on the silica.
• the column was then reactivated for reuse by passing down hexane at 180°C and 13-bar.
• the reactivated silica column was used again to refine a fresh batch of neutralised illipe, pre-treated as described, the whole cycle of refining, desorption and reactivation being repeated 15 times.
• Such a regenerated silica gel can be reused for satisfactory diglyceride removal from the illicher fat. Omission of the pre-treatment eventually renders the spent silica non-regenerable, as evidenced by total failure to adsorb diglycerides after limited reuse.
• the spent silica was desorbed in the column by washing with a mixture of 85 vol % hexane and 15 vol % methanol at 50°C and reactivated by passing hexane vapour under pressure at 90°C inlet temperature through the column, until methanol was completely driven out.
• the column was reactivated and reused 5 times, the diglyceride content being determined of the fat recovered after each use.

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• 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)
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• 1982
  • 1982-11-16 JP JP57503555A patent/JPS58501950A/ja active Granted
  • 1982-11-16 AT AT82306102T patent/ATE17746T1/de not_active IP Right Cessation
  • 1982-11-16 DE DE8282306102T patent/DE3268894D1/de not_active Expired
  • 1982-11-16 AU AU10123/83A patent/AU556001B2/en not_active Ceased
  • 1982-11-16 EP EP82306102A patent/EP0079799B1/en not_active Expired
  • 1982-11-16 WO PCT/GB1982/000327 patent/WO1983001782A1/en active Application Filing
  • 1982-11-17 CA CA000415779A patent/CA1188707A/en not_active Expired
• 1983
  • 1983-06-29 FI FI832371A patent/FI832371L/fi not_active Application Discontinuation
  • 1983-07-14 DK DK325683A patent/DK158839C/da not_active IP Right Cessation

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