Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The present invention relates to a process for obtaining
yolk lecithin, and more particularly to a process for
effectively obtaining yolk lecithin from a raw yolk by
subjecting the raw yolk to extraction with liquid dimethyl
ether and subsequently subjecting the resulting extract to
vacuum condensation so that the water content of the extract
is not more than 20 % by weight, whereby a lecithin-rich
fraction is produced as a separate phase from a neutral
lipids-rich fraction.
A raw yolk, in general, comprises water, yolk proteins
and egg lipids. The egg lipids comprises neutral lipids and
yolk lecithin, so in order to obtain yolk lecithin it is
generally necessary to selectivel~ obtain the egg lipids contain-
ing the desired yolk lecithin from an egg yolk. The
conventionally proposed methods for obtaining egg lipids
are classified into two kinds of methods, namely a scorch-
ing method and a solvent extraction method.
The scorching method comprises directly scorching a raw
yolk to selectively obtain egg lipids. The scorching method,
however, has various disadvantages. For example, the yolk
protems are lost during the couxse of scorching, and since
the yolk is unavoidably exposed to air at elevated temperatures,
the obtained egg lipids are extremely deteriorated. Further,
it is noted that a large amount of egg liplds remains
- 25 adhering to the residue. Therefore the efficiency of the
scorching method is extremely poor. For these reasons,
the scorching method has scarcely be n pract;cally employed.
On the other hand, in the solvent extraction method,
2 --
when a raw yolk as such is used as the starting material, it
has been hardly possible, by the use of a s:ingle solvent, to
effectively extract egg lipids containing the desired yolk
lecithin from the raw yolk, since in the natural state a
raw yolk is present in the form of a stable emulsion
composed, for example, of about 49.5 % by weight of water,
about 16.1 ~ by weight of yolk proteins and about 32.5 %
by weight of egg lipids, the balance being substantially
ash contents. Illustratively stated, polar solvents such as
methanol and acetone are capable of destroying the emulsion
of raw yolk to extract and remove water therefrom but these
polar solvents are extremely poor in the extraction ability
for egg lipids. Accordingly, such polar solvents are in-
capable of effectively extracting lecithin from the yolk.
Non-polar solvents such as ethyl ether, hexane and trichloro-
ethylene are hydrophobic, and therefore cannot extract
and remove water from a raw yolk. It is further to be
noted that such non-polar solvents are incapable of suf-
ficiently destroying the emulsion of raw yolk, but rather
the solvent cooperates with the raw yolk to form a one-
phase emulsion.~ Thus, with such non-polar solvents, it is
impossible to effectively~obta1n egg~lip1ds containing the
desired~yolk leai~thin from the raw yolk by extraction.
In the current method industrially practiced for solvent
:
extraction o lecithin from a yolk, there is =~ployed as
the =tarting materi=l a drled yolk obtalned by drying a raw
yolk with heated air. The dried yoIk is subjected to ex-
tr=ction with a solvent mixture of a polar solvent such as
~$~
methanol or acetone and a non-polar solvent such as chloro~
form, diethyl ether or trichloroethylene. In this method,
since the solvent mixture contains two different kinds of
component solvents, the procedures for the recovery of the
component solvents are complicated and cannot be conducted
economically. Further, the solvents used have boiling points
of 35C or more and hencel for complete removal of these
; solvents from the extract, it is required to heat the extract
at high temperatures by the use of steam or to subject the
extract to heat treatment at high temperatures for a pro-
longed period of time under reduced pressure. Yolk lecithin
is extremely susceptible to oxidation and thereforel when
the yolk lecithin is heat-treated at a temperature as high
as 60C or more under atmospheric pressure, the color of
yolk lecithin changes from yellowish orange to brown through
yellowish brown. Accordingly, the quality of the yolk
lecithin obtained through the heat treatment for the removal
of the solvents is extremely poor. The yolk lecithin produced
by such conventional solvent extraction methods has bad
smells of oxidized lipids and amines and lS colored brown.
Yolk lecithin has a wide variety of uses and~, for example,
;` it can advantageously be used as an additive for cosmetics
such as shampoos, hair dressing agents and nourishing creams,
andfoodstu~fs such as mayonnaise,and spongecake and o~er con
fectiQnary. But, such poor quality lecithin produced by
conventional methods is restricted in fiqld of use as well
as amount to be used.
As a result of researches of the present inventors, it
,
~ - 4 -
. ,
was found that liquid dimethyl ether is capable of effectively
extracting egg lipids containing the desired yolk lecithin
from a raw egg yolk.
In order to demonstrate the excellent extraction
abilities of liquid dimethyl ether for extraction of egg
lipids from a raw yolk, experiments were carried out using
methanol, ace~one, hexane and liquid dimethyl ether as
the extraction solvent. The method and results are shown
in the following Experiment 1.
Experiment 1
To 50 g of a raw yolk of hen egg (the yolk co~tained
50.3 ~ by weight of water, 31.4 % by weight of egg lipids
and 16.3 % by weight of proteins, the balance being sub-
stantially ash contents) were added 150 g of a solvent toobtain a mixture of the raw yolk and the solvent. Using
methanol, acetone, ~exane and liquid dimethyl ether as the
solvents, there were obtained four different kinds of
extraction mixtures. Each of these mixtures was charged in
a 1 liter glass autoclave having a stirrer, and extraction
was effeated, while stirring, at 20C for 30 minutes. The
extraction mixture was subjected to filtration using a
cotton filter to separate yolk proteins as the filtration
residue. From the obtained filtrate the solvent and water
were removed by evaporation using a vacuum condenser (at
.
30C and under 20 mmHg~ to obtain a dried extract of which
the water content is nearly zero. The quantity of the
dried extract was defined as "total lipid". The le~ithin
-- 5 --
~.5~
content of the dried extract ~total llpid) was measured in
accordance with ~he method as described in "Tsuchiya,Tomotaro,
Kijun Yushi Bunseki-ho, 2.2.8.3.-71 ~inshishitsu(Aseton-ho)~
Shadan-hojin Nihon Yukagaku Kyokai, 1972l' (Tomotaro Tsuchiya,
St~ndard A~ysis Method for Fats an~ Oils, Item 2.2.8.3.71phospholipid
(acetone method), published by Japan Oil Chemistry Association in 1972) in whichthe lecithin content was determined as the acetone-insoluble
matter. The value obtained by subtracting the lecithin
content from the total lipid, was defined as the content
of neutral lipids.
Results are shown in Table 1.
Table 1
Solvent Total Content of Content of
lipid, g lecithin, g neutral lipids, g
Liquid dimethyl
ether 12.0 4.0 8.3
Methanol 3.7 2.9 0.8
Acetone 7.9 1.7 6.2
Hexane 1.4 0.6 0.8
As is apparent from Table 1, the extraction abilities of
mathanol, acetone and hexane for egg lipids are extremely
i poor as compared with t~at of liquid dimethyl ether.
Further, the following Experiment 2 was conducted to
show the influences of the liquid dimethyl ether - extraction
on the qualities of the desired lecithin - containing egg
lipids.
i Experiment 2
-- - .
150 g of a raw yolk of hen egg (the yolk contained
50.3 ~ by weight of water, 31.4 ~ by weight of e~g lipids,
-- 6 --
5Z~i~
16.3 ~ by weight of proteins and 2.0 % by weight of ash)
were charged into a 1 liter autoclave having a stirrer, and
525 g of liquid dimethyl ether were introduced under pressure.
A first extraction was conducted at 30C for 15 minutes under a pressure of
5.9 kg/cm2G. The portion containing yolk proteins was separated from
the dimethyl ether solution of extract by filtration using
a cotton filter. The portion containing yolk proteins was
subjected to a second extraction with 150 g of liquid dimethyl
ether and to a filtration - separation of crude yolk proteins
in the same manner as described above, thereby to obtain a
dimethyl ether solution. The dimethyl ether solutions
obtained by the first and second extractions were combined.
From the combined dimethyl ether solution, the dimethyl ether
was removed by evaporation under atmospheric pressure to
obtain 85 g of extract. The extract was subjected to freeze-
drying to obtain 42 g of egg lipids which had a natural yolk
color (Gardner No. 11.0) and a natural yolk odor. On the
other hand, the crude yolk proteins obtained by filtration - separation
wereallowed to s~d at 20C under~20 mmHg for ~0C to evaporate the re-
malning dlmethyl ether, thus giving 60 g of yolk proteins. The resulting
; yolk proteins had a cholesterol c~ntent of 0.8 mg/g on a dry basis, and
this means that 97 ~ of the cholesterol orlginally contained
in the raw~yolk was removed.~ The obtained yolk proteins was
examined according to A.O.C.S. Of~icial Method Ba 11-65 and
~25 ~found to have a nitrogen solubility index (N.S.I.) of 78.
This ~act shows that the yolk~proteins were not denaturated
A comparison of the thus obtalned egg lipids and the egg
ipids manu~actured and sold by Viovin Corporation, U.S.A.
`,
~ - 7 -
'"' '
and commercially available in the name of "Egg Oil" was .
made, and results are summarized in Table 2.
Table 2
Egg lipids
Obtained by Manufactured and
liquid di- sold by Viovin
methyl ether Corporation,
extraction U.S.A.
Lecithin content*, %30.6 23.8
Iodine ~alue 63.9 71.7
Saponification value203.5 199.7
Peroxide valwe 0.3 9.3
Acid. val.ue 7-5 10.4
Color, Gardner No. 11.0 18.0
Odor Fresh yolk Strong odor
odor of amines
~ 15 *Measured according to the above-mentioned method as described in Tbmotaro
: :Tsuchiya, S~ard Analysis Me~ for Fats and Oils, It~m 2.2.8.3.-71 phos-
pholipid (acetone method), published by Japan Oil Chemistry Association in 1972. :
As is apparent from Table 2, by the extraction using .
liquid dimethyl ether, the egg lipids can be effectively
20 obtained without denaturation thereof. .
In the raw yolk, yolk proteins and yolk lecithin are .
bonded together by a hydrogen bond and a bond due to van
,,
der Waals' force to form a stable O/W type emulsion in which
the neutral lipids serve as nuclei. Therefore, in order
~o effectively obtain yolk lecithin from a raw yolk by a
solvent extraction method, the solvent to be used in the
extraction should have a capacity of not only cleaving these
bonds to liberate~ the lecithin but also dissolving thereinto
the liberated lecithin.
- 8 -
Dimethyl ether has a molecular weight of 46 and a
diameter across the molecule as smaller as 5 A. Though dimethyl
ether is an ether, it has a weak polarity and a mutual
solubility for water. For example, at 20C, 54 g of dimethyl
ether can be dissolved in 100 g of water and 6.3 g of water
; can be dissolved in 100 g of dimethyl ether. Because of its
small diameter and specific properties, dimethyl ether is
capable of easily permeating into the natural product sub--
stances as compared with other oryanic solven~s. Further,
it is noted that when the liquid dimethyl ether is employed
for the extraction of yolk lecithin from a raw yolk, the
bonds between the yolk lecithin and the yolk proteins are
effectively cloven due to the mutual solubility between
the liquid dimethyl ether and the water present in the raw
yolk to liberate the lecithin into the obtained extraction
mixture. Such excellent performance cannot be attained by
any other solvents or mixtures thereof. In addition, it is
noted that the extraction of a raw yolk with liquid dimethyl
ether gives, as the extraction residue, excellent quality
yolk proteins which are not only free of egg lipids and
cholesterol but also have not undergone denaturation.
Dimethyl ether has a boiling pOillt as lcw as -24.9C,
and is ga~eous under standard atmospheric conditions~ It
can be readily liquefied by cooling to below about -25~ at
atmospheric pressure or by compression to above about 5 to 6
kg/cm2G at room temperature. Therefore, after the
extraction with *he thus liquefied dimethyl ether, the
dimethyl ether can be easily remo.ed nd rocovered by
_ g _
~5Z~
evaporation at room temperature and atmospheric pressure.
The recovery and removal of the extract and dimethyl ether used
as the extractant can be easily conducted without using high
temperature conditions, so that the process can advantageously
be carried out without causing the desired yolk lecithin and
the yolk proteins to be denaturated. Even when the dimethyl
ether remains in the extract in an amountas small as a trace,
it can be easily, completely removed by elevating the
temperature slightly, e.g., to about 50C for a short period
of time or by reducing the pressure, for example by treating
the extract at 20C under a pressure of 20 mmHg for 120
minutes.
As described, when the raw yolk is subjected to ex-
traction with liquid dimethyl ether, the desired yolk lecithin
can be effectively extracted together with neutral lipids and
water, without causing denaturation of the lecithin as well
as the yolk proteins.
Based on the excellent extraction capacity of liquid
dimethyl ether for egg lipids containing the desired lecithin,
; 20 we have made extensive and intensive researches, with a view
to developing a new process for effectively obtaining high
~uality lecithin from a raw yolk by a solvent extraction method.
As a result, it has been found that when the extract contain-
~ ing lecithin, neutral lipids and water, which extract is
obtained in high yield by an extraction process comprising
contacting a raw yolk wlth liquid dimethyl ether and removing
yolk proteins from the resulting extraction mixture, followed
by removal of the liquid dimethyl ether by evaporation, is
:~ :
-- 1 0
. . .
~5~
subjected to vacuum condensation to reduce the water content
so that the water content is not more than 20 % by weight
based on the extract, the extract is caused to separate into
tw~ distinct fractions, namely a lecithin-rich fraction and a
neutral lipids-rich fraction.
It is an object of the present invention to provide a
process for effectively obtaining yolk lecithin from a raw
yolk by an extraction method using liquid dimethyl e~her.
It is another object of the present invention to provide
a process of the kind described above, in which the yoik
lecithin can be obtained in high yield without denaturation
thereof, and at the same time the yolk proteins are also
recovered without undergoing any denaturation.
It is still another object of the present invention to
provide a process of the character described, in which the
dimethyl ether can be recovered with high ef~iciency and
reused with great advantages.
It is a further object of the present invention to
provide a process as mentioned above, which can be easily,
simply carried out.
The foregoing and other objects, features and advantages
of the present invention will be apparent to those skilled
in the art from thefollowing detailed description, the appended
claims and the accompanying drawing in which:
Figure is a graph showing the relationship between the
water content of the ~act after dehydration of the extract-bui before
deh~dration o the isolated lecithin-rich fraction and the yoIk lecithin
content (on a~water-free basis) of ~e final product obtained by dehydration
of the isolated lecithin-rich fraction.
~ 11 -- .
, .
~5~
Essentially according to the present invention, there
is provided a process for obtaining yolk lecithin from a raw
yolk which comprises subjecting a raw yolk to extraction with
liquid dimethyl ether, the weight ratio of liquid dimethyl ether
to raw yolk being not less than 2 : 1, followed by separation
of the yolk proteins contained in the extraction mixture and
removal of the liquid dimethyl ether, to obtain an extract
comprising lecithin, neutral lipids and water; and dehydrating
the extract so that the water content of the extract is not
more than 20 % by weight, thereby causi.ng the extract to
separate into a lecithin-rich fraction and a neutral lipids-
rich fraction followed by isolation of the lecithin-rich fraction.
The extract obtained through the extraction with liquid
dimethyl ether is an emulsion of a three-component system
composed of yolk lecithin, neutral lipids and water, and
the content of neutral lipids is larger than that of lecithin.
In general, the weight ratio of the lecithin content to the
content of neutral lipids is about 30 : 70. According to
the process of the present invention, when the extract is
; 20 subjected to dehydration to an extent that th~ water content
o~ the extract is not more than 20 % by weight, tha extract
is surprisingly caused to separate into two distinct
fractions, namely, a lecithin-rich fraction and a neutral
lipids-rich fraction. The thus separated lecithin-rich
fraction comprises lecithin, neutral lipids and water but it is
rich in lecithin as compared with the above-mentioned extract as such,
that is, the weight ratio of the lecithin content bo the oontent of
neutral lipids is about 50 : 50 to about 85 : 15. On
the other hand, the separated neutral lipids-rich fraction
; - 12 -
.
~5Z~
comprises ~neutral lipids and very ~1 ar~unts of lecithin and water.
In another aspect of ~he present invention, the leci~hin-rich fract-
ion may further be subjec~ to a second-stage dehydration to
rer~ve water, thereby enabling the water content of the product to be
further decreased~ Only by this second-stage dehydration, the water oon-
tent of the final product can ~e reduced to an extent as low as`below 2
by weight, whereby the quality of the product can be ir~roved.
In practicing the present invention, the source of a
raw egg yolk is not critical, but from the viewpoint of
availability, there may usually be used raw yolks of hen egg,
quail egg, duck egg and the like. The raw yolk as such may
be employed. A frozen yolk and a refrigerated yolk may also
be employed.
The extraction procedures using liquid dimethyl ether
can ~e conducted, requiring no complicated operation and
apparatus. Illustratively stated, the extraction may be
conducted ~y contacting a raw yolk with liquid dimethyl
ether, using a method as ordinarily employed in the extraction
process, for example batchwise method with stirring, column
extraction method, under such conditions that the dimethyl
ether is maintained to be liquid (e.g., at room temperature
under 5 to 6 kg/cm2G, or at below -25C and atmospheric
pressure).
The amount of liquid dimethyl ether to be employed in
the extraction involved in the process of the present
invention may slightly vary depending on the temperature
employed, but may generally be such that the weight ratio
of liquid dimethyl ethex to raw yolk i5 not less than 2 : 1.
Th~ quantity of water which is extracted together with neutral
- 13 -
~5Z~
lipids and lecithin is approximately equal to the amount of
saturation solubility of water for the liquid dimethyl ether
at the temperature employed. Therefore, in order to not
only attain good extraction efficiency of egg lipids contain-
ing the desired lecithin but also to facilitate the sub-
sequent dehydrating operation, the weight ratio of liquid
dimethyl ether to raw yolk may advantageously be in the range
of 2 : 1 to 5 : 1.
After the extraction operation is completed to obtain
an extraction mixture, the dimethyl ether solution of the
extract containing neutral lipids, yolk lecithin and water
is separated from the yolk proteins produced as the extraction
residue, using a suitable means such as a filter, centri-
fugal separator, siphon or the like. If desired, the yolk
proteins produced as the extraction residue may further be
subjected to extraction ~ith liquid dimethyl ether so that
the yolk lecithin remaining unextracted can be advantageously
recovered.
From the dimethyl ether solution is removed the liquid
dimethyl ether by evaporation as described before, thereby
to obtain an extract comprising neutral lipids, yolk` lecithin
and water.
The thus obtained extract is then subjected to dehydration
so that the water content is not more than 20 % by weight.
~he content of water in the extract obtained directly
from the extraction varies depending on the amount of liquid
dimethyl ether used. For example, when the extraction is
conducted using 5 parts ky weight of liquid dimethyl ether
:
- 14 ~
per 1 part ~y weight of raw yo~c and the dimethyl ether is then
removed from the demethyl ether solution, the content of
water in the extract is 50 % by weigh~. The thus obtained
extract comprises water, neutral lipids and lecithin. As
the extract is condensed by dehydration under reduced
pressure, the emulsion constituting the extract is gradually
destroyed and the neutral lipids start to be concentrated into the
upper layer of the condensed extract, and the content of
lecithin in the lower layer o the condensed extract is caused to
increase , resulting in separation of the extract into two
distinct fractions, namely, a lecithin-rich fraction and~a neutral
lipids-rich fraction. As described above, the dehydration
in this stage may be effected by vacuum condensation. The
pressure for the vasuum condensation may be about 100 mmHg
or lower, more preferably about 10 to 30 mmHg. The temperature
may be 50C or lower, more preferably 30 to 40C. At
temperatures in this range, change of color to brown can be
completely avoided. In this stage, the dehydration of the
extract by vacuum condensation is effected to an extent that
the water content of the extract is not more than 20 % by
weight, more preferably 20 to ~ % by weight. Taking as
an example the case where in the extraction the weight ratio
of liquid dimethyl ether to raw yolk is 5, th~ amount
of water removed by this dehydration step is 60 to 80 ~ by
weight of the water contained in the extract. After the
dehydration by vacuum condensation, there is obtained a
lecithin-rich fraction (average composition: 35.~ % by weight
;
~ 15 -
of yolk lecithin, 19.2 % by weight of neutral lipids and
45.0 % by weight of water) as a separate phase from a neutral
lipids-rich fraction (average composition: 96.2 ~ by weight
of neutral lipids, 3.5 % by weight of yolk lecithin and 0.3
by weight of water~. If the content of water in the extract
- is excessively reduced, i.e~, to less than 2 % by weight
based on the extract, the lecithin tends to dissolve into
the neutral lipids, thus disadvantageously leading to
decrease in the yield of lecithin as well as reduction in
the content of lecithin in the final product.
As described, according to another aspect of the present
invention, the lecithin-rich fraction obtained by the first-
stage dehydration as mentioned above mayfurther be subjected
to a second-stage dehydration to remove water. By this
second-stage dehydration, the water content of the product
can be reduced to an extent as low as below 2 % by weight.
Thus, there can be obtained a high quality produ~t in which
the lecithin content is as high as about 50 to about 85 % by
weight on a water-fxee basis and the water content is as low
as below 2 % by weight to nearly 0 % by weight. The term
"the lecithin content on a water-free basis" as used herein
is intended to mean the lecithin content based on the total
amount o~ lecithin and neutral lipids (exclusive of water)
contained in the product. The second dehydration may be
effected by either reeze-drying or vacuum drying. The
former drying method is advantageous when the ~ater content
of the lecithin-rich fractlon is about 10 ~ by weight or
less, while the latter drying method is advantageous when
' ' .
~5~1L
the water content is more than 10 ~ by weight. In the second
dehydration step, the drying may be effected at no~ higher
than 30C under a pressure of 0.05 to 0.5 mmHg.
As is apparent from the description, according to the
present invention, the yolk lecithin can be effectively
extraction-separated from a raw yolk and there can be
obtained a product having a high lecithin content without
denaturation of the lecithin in color and odor.
This invention will be more fully illustrated by the
following examples, but they are not construed to be limiting
the scope of the present invention.
Throughout the specification including Examples, the
lecithin content is determined according to the method as
described in "Tsuchiya~Tomotaro, Kijun Yushin Bunseki-ho, 2.2.8.3.-
1 15 71 Rinshishitsu(Aseton-ho), Shadan-hojin Nihon Yukagaku Kyokai,
;¦ 1972" (Tomotaro Tsuchiya, Standard Analysis Method or Fats
; and Oils, Item 2.2.8.3.-71 phospholipid (acetone method),
published by Japan Oil Chemistry Association in 1972).
¦ Example l
100 g of a raw yolk of hen egg (the yolk contained 50-3 ~
by weight of water, 31.4 % by weight of egg lipids, 16.3 % by
weight of proteins and 2.0 ~ by weight of ash) were charged
into a l liter autoclave having a stirrer, and 500 g of liquid
~ dimethyl ether were introduced a~ room tempera-
~5 ture under pressure. Extraction was carried out at 20C under
a p~essure of 4.2 kg/cm2G for 15 minutes while stirringO
The dimethyl ether solution of the extract was separated from
the portion containing yolk proteins by filtration using a
cotton filter. From the dimethyl ether solution, the dimethyl
ether was evaporated to obtain 48 g of an extract from the
yolk. The same procedures as described above were repeated
7 times to obtain 336 g in total of the extract. 7 sample
extracts were prepared by weighing 45 g from the extract.
. , , _ _ _ , . . .
Each of the sample extracts was charged into a 500 ml separable flask
adapted for evaporation. The flask was immersed in a water
bath kept at 80C (the temperature of the extract was 30 to
40C~ and the internal pressure of the flask was reduced to
from 36 to 20 mmHg by means of an ejector attached to the
exit mouth of a service water pipe to effect dehydration of
the extract. To the 7 sample extracts, as the period for
the dehydration of the extract, were~allotted 0 minute, 15
minutesl 30 minutes, 45 minutes, 60 minutesr~80 minutes and
i 15 120 minutes, respectively. There were obtained condensed ex-
1, .
trxcts-exch comprising two distinct phasesj namely, a neutral
lipids-rich fraction and a lecithin-rich fraction. Each
,
(except that of the ~-minute dehydration) of the condensed
extracts comprising two phases, was further subjec`ted to
centrifugal separation using a precipitation type centrifugal
separator under 5,000 G for lO mlnutes to obtain a lecithin-
rich fraction. The lecithin-rich fraction was subjected to
~: : : : :
dehydration to obtain a final product containing lecithin.
Results are summarized in Table 3.
~
:~ :
,
:: : ` : :
.
~: . ;
. ~
.
- 18 -
,
.
.
Table 3
Dehydration Water.content of the extract ~olk lecithin content
period, after dehydration of the (on a water-free basis)
minutes extract but before de- of the final product
hydration of the isolated obtained by dehydra-
lecithin-rich fraction, wt % tion of the isolated
lecithin-rich fraction,
~7t %
.
0 49.8 32.1
20O0 50.0
15.2 66.5
13.6 67.5
10.1 71.5
6.3 73.9
120 2.0 61.9
; Note: * The value shows the lecithin conten~ of the
. extract as such (before separation into the
two fractions),
The yol~ lecithin contents are plotted againstthe water contents
after the first-stage dehydration of the extract to obtain a
graph shown in FIGURE of the accompanying drawing.
~; : , ,
' ' '
~; ~ 25
. .
-- 19 --
5~
Example 2
150 g of a raw yolk of hen egg (the yolk con ~ ned 50.2 %
by weight of water, 32.3 % by weight of egg lipids, 15.6 %
by weight of proteins and 1.9 % by weight of ash) were charged
into a 1 liter glass autoclave having a stirrer, and 450 g
of liquid dimethyl ether were introduced under pressure.
Extraction was carried out at 30C under 5.9 k~/cm2G for
15 minutes while stirring. The dimethyl ether solution of
the extract was separated from the egg proteins by filtration
using a cotton filter. To the egg proteins obta.ined as
the filtration residue were added 150 g of liquid dimethyl
ether and the same extraction as described above was carried
; out at 30C under 5.9 k~/cm2G for 5 minutes to extract egg
lipids remaining in the egg proteins. The dimethyl ether
solution from the second extraction was separated by
filtration using a cotton filtex, and this dimethyl ether
solution was combined with the dimethyl ether solution
obtained in the first extraction. The combined dimethyl
ether solution was charged into a 1 liter beaker, and this
beaker was i~mersed into a water bath (which was kept at
25C) to evaporate the~dimethyl ether. There were obtained
83 g of extract. The extract was subjected to vacuum con-
densation, using a rotary evaporator~ at 30C for 60 minutes
to remove 28 g of water. The resulting condensed extract
- 25 consisted of two phases and contained 18.5 % by weight of
water. The condensed extract was then subjected~to
centrifugal separation under 5,000 G for 10 minutes to obtain
25 g of a neutral lipids-rich fraction (which constituted
- 20 -
52~L
an upper layer) and 30 g of a lecith:in-rich fraction (which
constituted a lower layer). The lecithin-rich fraction was
freeze-dried to obtain 20 g of product containing lecithin.
The lecithin content of the product was 70.3 % by weight
on a water-free basis.
Example 3
155 g of a raw yolk of hen egg (the yolk had the same
composition as described in Example 2~ were charged into
a 1 liter glass autoclave having a stirrer, and 340 g of
liquid dimethyl ether were introduced under pressure.
Extraction was carried out at 35C under 7,.0 kg/cm2G for
; 5 minutes. The dimethyl ether solution obtained by the
extraction in the autoclave was filtered through a cotton
filter into another 1 liter autoclave. From the dimethyl
ether solution, dimethyl ether was evaporated at 30C under
6.0 kg/cm2G, and the evaporated dimethyl ether was recovered
by leading it into a pressure bottle cooled to 18C through
a stainless pressure tube. The quantity of dimethyl ether
recovered was 312 g.
The extract left in the autoclave was heated to 30C
~(the temperature of the autoclave was 40C` under 10 mm~g
to effect vacuum condensation to dehydrate the extract.
60 Minutes thereafter, 53.2 g of condensed extract were found
in the autoclave, and the water content of the condensed
~5 extract was 17.G ~ by weight. The condensed extract con-
sisting of two layers was poured into a suction funnel
equipped with a filter cloth and a receiver with its pressure
reduced to 400 mn~Ig, thereby to remove a neutral lipids-rich
fraction of the two layers as the filtrate. 28.4 g of
a lecithin-rich fraction were left on the filter cloth.
The lecithin-rich fraction was freeze-dried to obtain 18.5 g
of a dry product containing lecithin. The dry product was
found to have 2.0 ~ by weight of water and 67.0 % by weight
(on a water-free basis) of lecithin.
Example 4
-
85 g of a fxozen yolk of hen egg (the yolk contained
53.0 % by weight of water, 30.5 % by weight of egg lipids,
14.S ~ by weight of proteins and 2.0 ~ by weight of ash)
were charged into a 1 liter stainless autoclave, and after
the frozen yolk had molten into liquid yolk, 385 g of liquid
dimethyl ether were introduced under pressure into the
autoclave. Extraction was conducted, with stirring, at 25C
under 5.0 kg/cm2G for 5 minutes. The resulting dimethyl
ether solution of the extract was poured, under atmospheric
pressure, into a beaker through the filter cloth put on a
metal gauze. While keeping the temperature in the beaker
at 20C, the dimethyl ether was evaporated to sivq 46.6 g of
an extract. The extract was then charged into a 300 ml
- separable flask and condensed, using an evaporator, at 35C
(the external temperature o the autoclave was 60C) under
15 mmHg for 20 minutes to obtain 29 g of a condensed extract
consisting of two layers (which contained 18.8 % by weight
oE water in total~. This condensed extract was subjected to
centrifugation under 4,000 G for 30 minutes, and the neutral
lipids-rich fraction of the two layers was removed by
- 22 -
decantation to obtain 18.0 g of a lecithin-rich fraction.
The lecithin-rich fraction was freeze-dried to obtain 12.7 g
of a product containing 1.2 % by weight of water and 72.3 %
by weight (on a water-ree basis) of lecithin.
Example 5
300 g of a refrigerated yolk ~the yolk oontained 54.0 %
by weight of water, 29.8 % by weight of egg lipids, 14.2 %
by weight of proteins and 2.0 ~ by weight of ash) were
charged into a 2 liter autoclave and 750 g of liquid dimethyl
ether were introduced under pressure. Extracti~n was conducted
under 2.2 kg/cm2G while keeping the temperature in the auto-
clave at 5C and thoroughly stirring the contents for 30
minutes. The dlmethyl ether solution o the extract was
separated, and the dimethyl ether was resovered in the same
manner as described in Example 3 to obtain 134 g of an extract.
The extract was charged into a 300 ml separable flask, and
vacuum condensation was conducted, using an evaporator, at
25C under 30 mmHg for 130 minutes to remove water. The
~ 20 condensed extract consisting of two layers in the flask were
; poured into a suction funne1 e~uipped with a filter cloth
-and a receiver with its pressure reduced to 400 mmHg, thereby
to remove a neutral lipids-rich fraction of the two layers
as the filtrate. 43O9 g (which contained 11.2 % by weight
of water? of a lecithin-rich fraction were left on the filter
; cloth. The~lecithin-rich fraction was dried under vacuum to
obtain 39.8 g of a product containing 2.1 % by weight of water
~and 73.2 % by weight (on a water-free basis) of lecithin.
.
; - 23 -
Example 6
100 g of a raw yolk of hen egg (the same raw yolk as
used in Example 2) were charged into a 1 liter glass
autoclave having a stirrer, and 75 g of liquid dimethyl
ether were introduced under pressure. Extraction was
carried out by stirring the contents in the autoclave at
5C under 2.2 kg/cm2G. The dimethyl ether solut:ion of
the extract was taken into a beaker through filtration using
a cotton filter. From this dimethyl ether solution, the
dimethyl ether was evaporated to obtain 12.6 g of an extract
containing 36.0 % by weight of water.
Into the residue left in the autoclave and still con-
taining a considerable quantity of egg lipids were introduced
220 g of liquid dimethyl ether under pressure, and extraction
was conducted at 5C under 2~2 kg/cm2G for 5 minutes while
stirring. By this second extraction, 32.0 g of an extract
containing 38.0 % by weight of water were obtained. The
first and second extracts were combined and charged into
an egg plant type flask. Vacuum condensation was conducted,
using a rotary evaporator, at 31C under 15 mmHg for 17
minutes. The condensed extract (32.8 g, which contained
19.0 % by weight of water) consisting of two layers was
centrifuged at 4,200 rpm for 15 minutes, and 16.0 g of a
. , .
lecithin-rich fraction was separated. The lecithin rich
fraction was subjected to freeze-drying to obtain 11.0 g of
; a product containing 2.0 ~ by weight of water and 59.8 ~ by
weight (on a water-ree basis) o lecithin.
.
- 24 -
~ ~5Z~
Example 7
2.0 kg of a raw yolk of hen egg (the yolk contained
52.5 % by weight of water, 30.1 % by weight of egg lipids,
15.6 ~ by weight of proteins and 1.8 % by weight of ash)
were charged into a 15-liter pressure tank, and 5.5 kg of
liquid dimethyl ether were introduced under pressure.
Extraction was conducted at 28~C under 5.7 kg/cm2G for 30
minutes while stirring. The dimethyl ether solution of
the extract was separated from the proteins by filtration
using a filter vessel having thereon a filter cloth having
a diameter of 290 mm~. The dimethyl ether solution was then
charged into another pre~sure tank and was heated to 40C,
and the evaporated dimethyl ether was recovered into a
container. 787 g of an extract containing 30.1 ~ by weight
of water was obtained. 7 sample extracts were prepared by
weighing 100 ~ from the extract. The sample extracts
were subjected to vacuum condensation, using a rotary
evaporator, at 40C under 10 mmHg for 0, 10, 20, 30, 40/ 50
and 80 minutes, respectively. Each (except that of the 0~
minute dehydxation) of the condensed extracts consisting of
two layers was centrifuged at 5,000 rpm for 15 minutes to
obtain a leci~hin-rich frac~ion. The lecithin-rich fraction
was reeze-dried to obtain a final product containing lecithin.
Results are summarized in Table 4.
2~5
- 25 -
.
~s~
Table 4
Dehydration Water content of the extract Yolk lecithin content
period, after dehydration of the (on a water-free basis)
minutes extract but before de- of the final product
hydration o the isolated obtained by dehydra-
lecithin-rich fraction, tion of the isolated
wt % lecithin-rich fract-
ion, wt %
0 30.1 36.5
19.3 52.3
15.0 66.8
13.1 70 5
10.4 80.6
7.2 82.3
2.1 66.9
Note) * The value shows the lecithin content of the
extract as such (before separation into the
two fractions).
The yolk lecithin contents are plotted against the water
contents after the first-stage dehydration of the extract
to obtain a graph ~hown in FIGURE of the accompanying
drawing.
.~ .
:: : :
~ 25
:
.
26 -
