CA1117134A - Oilseed processing - Google Patents

Abstract

ABSTRACT
A process for producing high quality crude oil and a high pro-tein low-fibre meal from thioglucoside-containing oilseeds in which the oilseed is dried at a seed temperature below about 70°C to a moisture content in the range 1-3% prior to solvent extraction of the oil. Prefer-ably, the oilseed is dehulled before the drying and oil extraction steps and dehulling is facilitated by a preliminary drying step at a seed temperature below about 70°C, to a moisture content below about 6%.

Description

3~

Thl~ in~entlorl Jela~es tu a proce~s for the production of high qu.llLty oll from tl~loglllcoslde-containing ollseeds. As used herein the term l~thioglucoside-collta:Lnlrlg~ oilseeds means those oilseeds of the ~assica type (rapeseed and mustard~ or Cral~e.
As Ls well known~ certain oilseeds, such QS rapeseed (Genus Brasslca~ which is one of the fi-ve mos~ wldely produced oilseeds in the t~orld, contain thioglucosides (glucosinolates~ which, by means oE endogenlc enzymes, myrosinase~, are spli~ into the deleterious ~ubstances isothio-cyanates and/or oxazolidinethiones, ~nd glucose and bisulphate. Other objectionable substances present in the seed, from the point o~ view of their use as animal or human feeds, include tannins, sinapine and phytic acid, all of which have negative nutritional effects. It is also known that thioglucosides can be removed from crushed oilseed by aqueous extract-ion (Canadian Patent 999,186 issued 11 February 1976 to An~ou et al and Canadian Patent 891,437 lssued 25 January 1972 to Tape et al) followlng a myrosinase lnactivating water treatment which is usually accomplished by soaking the seeds in hot water at 185F or more for several minutes to half an hour or re. The hot water treatment also has the advantage that it assists in the loosening of the seed coat. Following deactivation, aqueous extraction, crushing and drying, the seeds are flaked, air classi-fied into two fractions --a hullfraction containing some pulverized seed meat material and a seed meat fraction-- and the oil is extracted from the seed meat Eraction by pressing and solvent extraction, yielding an oil and a protein-rich white bland non-toxic defatted flour suitable for human or animal consumption.
The prlor art processes are 7 however, not without their disad-vantages, Firstly, the cooklng or hot water heat treatment over a period of time, although deactivating the myrosinase, is sufficient to cause some enzymic degradation of glucosinolates to form isothiocyanates which are - 1 - dg~

.

.34 fat soluble and are sub~e~ elltly ~x~Rcted wLth t~l~ o:ll to yi~ld sulpllur containlllg oils. Secondly, the moi~ture presen~ ls sufflc~ent ~o per~nit some solubLllzatioll oE ~W~9, mucllages and phosphollp:Lds ln the extractlon solvent, thus permitting Eurther contamlnatlon of the oll by these sub-stances. l~llrdly, chlorophyll exlsts in the se~d as a chlorophyll~proteln complex and as such Ls not solu~le ln hexane. However, heat treatment of the seed during the cooking process leacls to hydrolysls of thls coTnplex and the release of chlorophyll Wtll.Ctl iS soluble in the oil extractLon solvent.
The chlorophyll is also partly degraded by heat to chlorophyllides and related compounds also soluble in the oll and solvent. rrhus, the quallty of crude rapeseed oLl avallable for alkali and physlcal reflning is not as hlgh as ls deslred and the purlflcation and refinLng thereof is more diffi--cult. Fourthly, high temperature treatment ln the presence of water denatures the protein thereby renderlng it of low water solubility. Rape-seed oil processing is not, therefore, as commerclally attractive as the processing of other available vegetable oils such as soya?~peanut and sun flower oils, with which it must compete in the market place. Rapeseed is, however, an attractive crop in areas of the world, including the Canadian Prair$e provinces, which do not have a sufficiently benign climate to support soybean or other similar oilseed culture, and efforts are necessary to improve the processing thereof.
Although some success has been achieved in the development of rapeseed varieties with much reduced glucosinolate content, from which the sulphur originates, little can be done, in existing plants, to reduce solubilization of gums, mucilages and phospholipids in hexane in the presence of moisture. Marked reduction of chlorophyll in extracted rape-seed oil can be achieved by crushing well~ripened rapeseed in which there is very little or no chlorophyll. However, this is very difficult in countries, such as Canada~ where the growing season ~or rapeseed is short 3~
alld the colTIplc~e ~peni~ ee~ nfxe~l~ently achleyed due L~ p~emature ~ros~ cooL temper~ure-; or early dehydTatlon of the seed beore the chLorophyll has dis~ppeared from the seed.
It has alSQ been Eound that commerc:Lal rapeseed meal h~s a high fibre content1 derived Erom the high proportion o seed coat present in the seed? which may amount to as ~much as one third by weight of the oil extract-ed seed. The resultant meal has a relatlvely low ene*gy content and thus has only limLted value as a protein and energy source ln feed for poultry and pigs. If the seed coat ~hull) i8 removed from the seed, a light coloured, clean, defatted meal having a protein content oE at least 50%
and a fibre content of 5% or less can be achieved, which is a highly de~lr-able feed component of hlgh nutritive value for poultry cmd pigs. Hereto-fore there has been no commercially acceptable method to separate the seed coat from the meal.
Thus, it is an object of the present invention to overcome the disadvantagss of the prior art and provide a process for the production of a high qualiey crude rapeseed oil7 substantially free from contaminants?
which is suitable for alkali and physical refining.
Another object of the present invention is to provide a process for the production of a high-protein low-fibre meal from a Brassica or Crambe type oilseed having high nutritive value as a feed for livestock.
Thus by one aspect of this invention there is provided a process for treatlng thioglucoside-containing oil~seed which comprises the step of drying the oilseed at a seed temperature below about 70C to a moisture content in the range of about 1-3% prior to recovery of oil from said oilseed.
By another aspect there is provided a process wherein the oil~
seed is predried at a seed temperature below about 70C to a moisture content of about 6% prior to dehulling and drying.

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By ye~ anoth~r ~spe~t thexe ls prl~yided ~ llght col~ured~ clean, cle~atte(l thioglucoslde~contat.nln~ oilseed meal or flour~ contalnlng the orlginal thloglllcosicles Ln ~u~stantlally unaltered form, havlng a proteln content oE at least 50% arld a fibre content below 5~.
Andl by a stLlL further aspect the~e i8 provlded an organic solvent-extracted thiogLucoside-contalning ollseed crude oil, substanti.llly free of sulphur compouns, gums, mucllages, phosphollpLds and chlorophyll.
Unless otherwlse stated, all percentages descrlbed hereln are percentages by weight.
The inventioll will be described ln detall hereinafter with reference to the drawing ln whLch:
F:lgure 1 is a schematlc flow diagr~m of a preferred process accordlng to the present invention.
We have found that processlng conditlonæ for the e~traction of oll from the selected thioglucoslde-containing oilseed can be selected such that the gums, mucilages and phospholipids are not solubillzed by the extraction solvent, the glucosinolates are not hydrolysed to release iso-thiocyanates and tlle chlorophyll-protein complex is retained intact so that chlorophyll is not removed with the oil. We have found that lt is essential to avoid cooking the flaked seed in the presence of seed moisture levels existing in the seed. Thus, we have found that rather than proceed-ing by way of the conventional flaking and cooking treatment, followed by flaking~ solvent extraction of a low grade oil and recovering of a high fibre content meal; superior products are obtained by, with reference to Figure 1, cracking (2) clean seed (1~, following an optional but preferred drying step (3), described in more detail hereinafter, dehulling to separate ~4~ the hulls and any pulverized fine seed meat from the hulled seed, and drying C5~ the dehulled oil-containing seed fraction (and optionally the pulverized fines~ at a seed temperature below about 70C

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~o a mo.lsLu~e conLen~. .Ln tile ~ng~ 1-3~ pxee~aol.y ln a ~luidized hed dryer. AL~er dryill~ (5) ~he dr1.ed cracked seeds are subjec:ted to solverlt extractlon (6~ uslng any su:l.table alld conventlonal org~lic ~olven~, suctl as hexane or other so:lvent acceptable for .eood product use lhe so1vent extraction may be carried out ln one or more stages and the solvent 1nay, for obvious economic reasons, be recycl.ed. The sol-~ent i8 remoYed from the oi]. fraction by evaporatlon ~7) to produce a hlgh quality crude o:Ll (8). The solvellt.extracted seed or meal :Ls desolvent:lzad either wlth superhelted solvent (9) or steam (lO) dependirlg on lts final proposed use.
Desolventization in the absence oE moisture retalns protein solubllity in the meal and yields a product su:Ltable for urther processing to protein products su:Ltable Eor hu~ln consumption. Desolventization in the presence of moisture will inactivate the en yme systems and other factors capable oE exerting anti-nutritional effects.
As noted hereinabove rapeseed treated according to the process of : the present invention is preferably subjected to a drying step (3) prior to dehulling and drying (5) to a moisture content of 1-3%. We have found that by drying the whole seed, preferably by passage through a fluid bed dryer in which the temperature of the exit air does not exceed 70C, so that the moisture content of the seed is reduced to 2-5%, some of the moisture held in the capilliary structures of the seed coat is removed and this appears to facilitate the loosening of the seed coat from the seed. The dried whole seeds are then subjected to cracking or coarse ~illing, preferably : by passage through conventional equipment such as a MIAG ~ Strato Mill, so that the hulls of the seeds are split and fractured into portions : representing one quarter to one half of their original d:~mension so as to release the cotyledons enclosed essentially intact, but with not more than 7% of the original seed weight reduced to a particle size not held on a 30 Mesh (Tyler) screen (def:lning the fines fraction~. Tile mixture ', , , ' ' ~ ~ .

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0~ huLls and COtyledOllB C~lll be sep~ratcd :into llu:l.l, cotyle~on and flnes ~ractiolls on the baslH oE th~lr d:Lfferent densi.t:Lefl by passage through a c~nvent.Lonal cla~sl.~ r sucl-l as a K:lpp Ke.lly ~ Alr Flotatlon Stoner, yleld-ing a hull ~ractlon general:Ly character:L~ed by an o:ll colltent in the range about 12-20% (air dry basis), and a proteln content ln the range of about 12-16%, a cotyledon fracLi.on generally characterlæed by an oll content in the range about 45-55%, a protein content in the range about 20-2S% and a crude f:Lbre content in the range about 3-5%; and a fi.nes fraction ~enerally characterlzed by an oil contcnt in the range about 40 46%, a proteln con-tent in the range about 18~23~ and a crude Ei.bre content in the range about 5-10%.
Exam~le l C:Lean Tower rapeseed equal to Canada No. 1 Grade~ free of weeds and plant fragments, was dried in a Calmic Fluid Bed Dryer at an alr lnlet temperature of 100C for a perlod not ln excess of 15 minutes and such that the seed temperature di.d not exceed 65C.
The seed was allowed to cool to room temperature and then fractured in an 8 inch Bauer Disc Mi].l fitted wlth discs with splines about 1 mm wide and wlth a variable speed drive. l`he speed of the ro~ating disc and the ~0 space between the stationary and revolving disc were adJusted so that when the seed was fed into the mill at a slow pace, the seed was fragmented into coarse particles without pulverisation or build-up of powdered seed on the discq and so ~hat no seeds passed the discs without being fragmented. A
space of 0.073 inch ~etween the discs and a speed setting of 3.5 was found suitable for the seed lot used.
The seed fragments were separated into two fractions, dehulled seed and hulls plus fines, in a FRI laboratory classifier capable of handl-ing 10 pounds at a time (Food Research Institute Classifier, vide Canadian ;~ Institute of Food Sciences and Technology Journal, Vol. 6, No. 4, 1973, .
' page 298). By selec~ive control of the ~ir ~low throug~ the fluldized bed and by :Intro(luc.l.ng steam lnto thls ~ir Elow, ~o overcome ~tati.c effects on tlle w~lls of the fluicl bed ch~mber, the hulls and flnes were carrl~d over lnto the cyclone and col:Lected. The dehulled seed, belng denser, remained in the fluidized bed bucket and were recovered.
The hulls pllls fines fractloll was further separated by returning it to the fluid bed bucket and reclassifying in the laboratory c].assiEler with finer control of the alr flow through the fluidlæed bed, thus first removing the fines fraction and small hllll fragments and collecting from the cyclone, and leaving the larger hull fragments and "hypocotyls~ in the fluid bed bucket. These two separated fraction~ were then sèparated on Tyler sieves of 20 and 30 mesh when four fractions originat:Lng from the hulls plus f:Lnes were obtained as follows - hulls ~20 mesh, small hulls -20 to -~30 mesh, fines -30 mesh and "hypocotyls" -20 mesh, In thiæ manner 464 pounds of seed fragmented in the manner described yielded, after separation, 366 pounds dehulled seed, 58 pounds hulls, 13 pounds small : hulls, 24 pounds fines and 3.0 pounds "hypocotyls". About 1 pound samples, representative of each fraction, were pulverised, without heating, in a Retsch Laboratory Mill. The pulverised material was anal~sed according to methods described in the AOAC Handbook of Official Methods of Analysis (12th edition 1975), Association of Official Agricultural Chemists, Washington, D.C.
The dry matter composition of each fraction is given in Table I.

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'. ': ' ' : ' ' : , :, ' . : , , It is evldent that the fat 19 concentrated in the dehulled seed, Elnes and ~hypocotyls" whereas the crude fl'bre ls Eound in the hull and hull-rich fractions, the dehullPd seed fraction being substantially free oE hull fragments.
About one half pound samples, representative of each fraction, were homogenized, with the aid of a Polytron Model PT35 homogenizer, in hexane to remove the fat. After homogenizing for about 5 minutes, the homogenate was filtered on a Buchner funnel under vacuum. The solvent-poor solid was further extracted twlce with fresh hexane and filtered so as to yield a product virtually free oE fat. The residue was freed of he~ane by spreading in a thin layer in a shallow tray in a fume cupboard for one or two days. l'he resulting flour wa~ analysed as described above.
The composition of the fractions with the fat removed as described is gi~en in Table II.

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The an~lyses LLlucltrate the co~centratlon of proteinaceous matter ln the dehulled seed, "hypocotyls" ancl E:Lnes eractions whereas the crude fibre appears in tilose Eractions where the hulls are concentrated. Thus Lt Is evldent that a fractlonatlon of rapeseed itl the manner described yields protein rlch and crude fibre r:lch fractions compared to rapeseed without fractionating as described.
Example 2 A series of tests were conducted uslng Tower rapeseed of the kind used, drled and cracked In Example 1. The coarse cracked seed was separated into three fractions: dehulled seed, hulls and fine.s~ with the aid of a Kipp Kelly Alr Flotation Stoner Model S-30. By careful selection of table type, amplitude of vibrat:lon7 tllt and air flows an effective separation of the coarse fragmented seed into the two most desirable fractions of dehulled seed and hulls was achieved. The dehulled seed moved up the inclined vibrating table whilst the hulls move in the opposite direction and whereby the fines were aspirated in the air flow and collected by the cyclone. The dehulled seed and hulls were collected at the "reJect" and "product"ends of the table respective~
ly. 100 Parts by weight of cracked seed yielded approximately 82 parts dehulled seed, approximately 16 parts hull and 2 parts of fines with densities of 34, 19 and 23 pounds per cubic foot respectively. Analyses representative of each fraction as described in Example 1 gave the composition given in Table III.

TABLE :tLI
Prox:lmate Compositi~n of Tower Rapeseed and Fract:Lon Derlved There~rom, Separated By the Kipp Kelly Alr Flotatlon Stoller. (Dry Matter Basis) WholeDeh~llled Seed Seed Hulls Flnes % weight in Fractlon lO0.0 81.7 16.4 1.9 Density lbs./cu.ft.26 34 19 23 Composltion ~) Fat 48.0 56.1 18.7 39.5 Protein (N x 6.25)20.6 22.2 16.2 20.2 Fibre 7.6 2.9 21.8 9.6 Ash 3-7 3-9 4-3 4-5 Nitrogen Free Extract 20.1 14.9 39.0 26.2 (N.F.E.) The same samples when extracted with hexane as described in Example 1 gave products of the composition listed in Table IY. The : composition of a typical commercial rapeseed meal, derived from Tower seed, is also illustrated in Table IV and exhibits reduced protein content and higher fibre content.
TABLE IV
Proximate Composition of Hexane Extracted Tower Rapeseed and Fractions Therefrom Separated By the Kipp Kelly Air Flotation Stoner (Dry Matter Basis) Whole Dehulled Commercial Seed Seed Hulls Fines Tower Meal Composition (~
Fat 3.6 5.7 7.0 2 2 2.2 Protein (N x 6.25~40.4 48.3 18.4 33.3 41.6 Fibre 10.9 4.6 25.1 15.3 10.6 Ash 7.8 8.4 5.4 7.1 7.4 Nitrogen Free Extract 37.3 33.0 44.1 42.1 38.2 (N.F.E.) ' ~:~1.17~

From Tables [ antl II of X.xan~)le 1 ~nd Tables IIL and IV of Example 2 it will be observed that the Kipp Kelly Air Flota~ion Stoner separatlon result~ ln ~I slightly higher yield of dellulled seed and ~ffects a solllewhat more complete separation of hulls from dehulled seed with less degradation of the seed meat. Clearly, dehu:Lling prlor to hexane extrac-tion oE the fat ensures a more protelnaceous meal wlth a signiflcantly lower fibre content.
Example 3 Dehulled Tower Rapeseed~ prepared in a manner similar to that descrlbed in Example 1, was dried in a Calmic Fluid Bed Dryer in such a way that the seed temperature did not exceed 65C and Eor a time perlod such that the seed moisture content was reduced to l.S~ by weight.
100 Pounds of the dehulled, dried rapeseed was extracted with hexane in a QVF extractor, for approximately 60 hours of continuous extraction, until the hexane passing through the seed mass and drainlng into the boiler was water clear. Hexane was drained from the extracted, dehulled seed and residual hexane therein removed under vacuum. The meal was removed, placed in shallow trays and exposed to air for three days, and then pin milled to reduce the meal to a f~our tc pass a lO0 mesh Tyler.
55 Pounds of mealwere recovered ~ith the following dry matter composition (%) - Fat 6.2, Protein 50.9, Fibre 4.1, Ash 7.3, N.F.E. 30.7.
The solvent containing the oil ~miscella) was distilled to remove the hexane. The oil thus recovered was desolventized in a vacuum kettle with a steam jacket using 40 p.s.i. steam, and vacuum to remove the last traces of hexane. The resulting oil had a bright yellow colour with no discernable green colour. The oil was evaluated by the process control laboratory of a commercial vegetable oil refinery. The results~of the oil evaluation are given in Table V. Quality values typical of commerc:ial crude rapeseed oil are also illustrated.

IABLE V

Q~lality Char~cceristlcs oE Oll ~xtracted ~rom Tower Rapeseed by Prior Dehulling, Dryln~ and Direct Solvent Extractlon and of Com0~rcial Crude Rapeseed Oll Tower 011 Commerclal Crude Metal Content:
Fe 0.19 ppm Cu 0.02 ppm Peroxide Value 1.2 m.eq./kg. 0.5-2,5 m.eq.tkg.
Anisidine Value 2.1 Free Fatty Acids 0.2% 0 6 %
Phosphorus 13 ppm ~250 ppm Sulphur 1 ppm 15-20 ppm Chlorophyll 3.2 ppm ~5.0 ppm It i9 believed evident that the crude oil produced by the process of the present invention is superior in quality to tha~ customarily avail-able and, in particular, possesses low values for free fatty acids, phosphorus, sulphur and chlorophyll. An appreciable saving in refining time and cost, as compared to traditional crude rapeseed oil~ can there~
fore be anticipated. It has also been found that the refined oil produced from the improved crude oil possesses superior stability on storage, as compared to traditional refined rapeseed oil.
Example 4 A series of dehulled rapeseed, mustard and Crambe seed samples were solvent extracted~according to the procedures described in Example 3 and the meals recovered and pin milled. The resulting flours were analyæed and gave (on a dry matter basis~ the results set forth in Table Yl.

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Althougtl not all oE the flour prep~rations were exhaustlyely extracted wlth he.xane~ to reduce the res:ldual oll content therein to 2%
or less, it ls evident that, w:Lth effectlve extraction of the o:Ll, the resulting meals produced contain at le~lst 50% proteln and a crude fibre content below 5% and are therefore much improved product~ as compared to those presently commercial].y produced.

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for treating thioglucoside-containing oilseed which comprises the step of drying the oilseed at a seed temperature below about 70°C to a moisture content in the range 1-3% prior to recovery of oil from said oilseed.

2. A process as claimed in claim 1 wherein said oilseed is dehulled prior to said drying step.

3. A process as claimed in claim 2 wherein said oilseed is pre-dried at a temperature below about 70°C to a moisture content in the range below about 6% prior to said dehulling.

4. A process as claimed in claim 1, 2 or 3 wherein said dried oil-seed is flaked and subjected to solvent extraction.

5. A process as claimed in claim 2 or 3 wherein said dehulled dried oilseed is flaked and subjected to a hexane solvent extraction step.

6. A process as claimed in claim 1, 2 or 3 wherein said oilseed is selected from the group comprising Brassica genus and Crambe,

7. A process as claimed in claim 1, 2 or 3 wherein said oilseed is rapeseed.

8. A process as claimed in claim 1, comprising the steps of:
(a) drying said oilseed to a moisture content below about 6%;
(b) cracking said dried oilseed;
(c) separating hulls from said cracked dried oilseed;
(d) drying the dehulled oilseed from step (c) at a seed temperature below about 70°C to a moisture content in the range 1-3%;

(e) solvent extracting said dried dehulled oilseed; and (f) recovering a high quality crude oil and a dehulled solvent extracted meal.

9. A process as claimed in claim 8 wherein said oilseed is rapeseed.

10. A light coloured, clean, defatted thioglucoside-containing oil-seed meal or flour, containing the original thioglucosides in substantially unaltered form, having a protein content of at least 50% and a fibre content below 5% when produced by the process of claim 8 or its obvious chemical equivalent.

11. A light coloured, clean, defatted thioglucoside-containing oil-seed meal or flour, containing the original thioglucosides in substantially unaltered form, having a protein content of at least 50% and a fibre content below 5% when produced by the process of claim 9 or its obvious chemical equivalent.

12. An organic solvent-extracted thioglucoside-containing oilseed crude oil, substantially free of sulphur compounds, gums, mucilages, phospholipids and chlorophyll when produced by the process of claim 8 or its obvious chemical equivalent.

13. An organic solvent-extracted thioglucoside-containing oilseed crude oil, substantially free of sulphur compounds, gums, mucilages, phospholipids and chlorophyll when produced by the process of claim 9 or its obvious chemical equivalent.