U.S. patent application number 14/747948 was filed with the patent office on 2015-10-15 for oil composition and method of producing the same.
This patent application is currently assigned to Poet Research, Inc.. The applicant listed for this patent is Poet Research, Inc.. Invention is credited to Jason Bootsma.
Application Number | 20150291923 14/747948 |
Document ID | / |
Family ID | 44653588 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150291923 |
Kind Code |
A1 |
Bootsma; Jason |
October 15, 2015 |
OIL COMPOSITION AND METHOD OF PRODUCING THE SAME
Abstract
This invention relates to a corn oil composition comprising
unrefined corn oil having a free fatty acid content of less than
about 5 weight percent, and methods for producing the same.
Inventors: |
Bootsma; Jason; (Sioux
Falls, SD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Poet Research, Inc. |
Sioux Falls |
SD |
US |
|
|
Assignee: |
Poet Research, Inc.
Sioux Falls
SD
|
Family ID: |
44653588 |
Appl. No.: |
14/747948 |
Filed: |
June 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12877987 |
Sep 8, 2010 |
9061987 |
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14747948 |
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12208127 |
Sep 10, 2008 |
8702819 |
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12877987 |
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61241874 |
Sep 12, 2009 |
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Current U.S.
Class: |
426/624 |
Current CPC
Class: |
C07C 57/12 20130101;
C11C 1/005 20130101; C11B 5/0092 20130101; C11B 13/00 20130101;
C11B 5/0007 20130101; C11C 1/08 20130101; Y02W 30/74 20150501; A23D
9/02 20130101; C11C 1/045 20130101; Y02E 50/10 20130101; C07C 53/00
20130101; C10L 1/026 20130101; A23D 9/00 20130101; C11C 3/00
20130101; A23K 10/38 20160501; C12F 3/10 20130101; A23D 9/007
20130101 |
International
Class: |
C12F 3/10 20060101
C12F003/10; A23K 1/06 20060101 A23K001/06 |
Claims
1-34. (canceled)
35. A distillers dried grain comprising about 5% or less fat.
36. The distillers dried grain of claim 35, further comprising
about 30% protein.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application claims priority to U.S. Provisional
Application Ser. No. 61/241,874, filed Sep. 12, 2009, and is a
continuation-in-part of U.S. patent application Ser. No.
12/208,127, filed Sep. 10, 2008, both of which are incorporated
herein by reference in their entirety.
FIELD
[0002] This invention relates to corn oil compositions and, in
particular, corn oil compositions containing a free fatty acid
content of less than 5 weight percent as well as to methods for
producing the same.
BACKGROUND
[0003] Ethanol can be produced from grain-based feedstocks (e.g.,
corn, sorghum/milo, barley, wheat, soybeans, etc.), from sugar
(e.g., sugar cane, sugar beets, etc.), or from biomass (e.g.,
lignocellulosic feedstocks, such as switchgrass, corn cobs and
stover, wood, or other plant material).
[0004] In a conventional ethanol plant, corn is used as a feedstock
and ethanol is produced from starch contained within the corn. Corn
kernels are cleaned and milled to prepare starch-containing
material for processing. Corn kernels can also be fractionated to
separate the starch-containing material (e.g., endosperm) from
other matter (such as fiber and germ). The starch-containing
material is slurried with water and liquefied to facilitate
saccharification, where the starch is converted into sugar (e.g.,
glucose), and fermentation, where the sugar is converted by an
ethanologen (e.g., yeast) into ethanol. The fermentation product is
beer, which comprises a liquid component, including ethanol, water,
and soluble components, and a solids component, including
unfermented particulate matter (among other things). The
fermentation product is sent to a distillation system where the
fermentation product is distilled and dehydrated into ethanol. The
residual matter (e.g., whole stillage) comprises water, soluble
components, oil, and unfermented solids (e.g., the solids component
of the beer with substantially all ethanol removed, which can be
dried into dried distillers grains (DDG) and sold, for example, as
an animal feed product). Other co-products (e.g., syrup and oil
contained in the syrup), can also be recovered from the whole
stillage. Water removed from the fermentation product in
distillation can be treated for re-use at the plant.
[0005] Various processes for recovering oil from a fermentation
product are currently known in the art. Such processes, however,
can be expensive, inefficient or even dangerous. For example, some
process, such as that set forth in WO 2008/039859, utilize a
solvent extraction technique that, in turn, requires the use of
volatile organic compounds such as hexane. Other processes, such as
that set forth in U.S. Application Publication No. 2007/0238891,
utilize high amounts of heat. Still other conventional processes,
such as that set forth in U.S. Application Publication No.
2006/0041152 and 2006/0041153, simply apply a centrifugal force to
a fermented product in an attempt to separate an oil product.
[0006] Conventional processes for recovering oil from a
fermentation product can sacrifice oil quality such that the oil
contains a high level of free fatty acids. The presence of a high
level of free fatty acids can hamper the production of end products
such as, for example, the yield and quality of any bio-diesel
eventually produced with the oil as a feedstock. Processes for
producing ethanol, such as the process set forth in WO 2004/081193,
produce fermentation byproducts which contain increased levels of
oils while maintaining a low level of free fatty acids. However,
upon application of a centrifugal force to the fermented product,
an emulsion can form which effectively locks the valuable oil
within the emulsion. Thus, a problem exists in that both
conventional and novel processes, alike, cannot effectively,
efficiently or safely separate or "break" quality oil from a
fermented product.
SUMMARY OF THE INVENTION
[0007] This invention relates to a corn oil composition comprising
unrefined corn oil having a free fatty acid content of less than
about 5 weight percent; a moisture content of from about 0.2 to
about 1 weight percent; and an alkali metal ion and/or alkaline
metal ion content of greater than 10 ppm.
[0008] This invention also relates to a method for providing a corn
oil composition from a corn fermentation residue comprising the
steps of a) separating the corn fermentation residue to provide an
emulsion layer and a first aqueous layer; b) adjusting the pH of
the emulsion layer to provide a corn oil layer and a second aqueous
layer; and c) separating the corn oil layer from the second aqueous
layer to provide the corn oil composition. This invention further
relates to a distillers dried grain comprising about 4% or less
fat.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1A is a perspective view of a biorefinery comprising a
cellulosic ethanol production facility.
[0010] FIG. 1B is a perspective view of a biorefinery comprising a
cellulosic ethanol production facility and a corn-based ethanol
production facility.
[0011] FIG. 2 is a schematic block flow diagram of a process for
producing ethanol from corn.
[0012] FIG. 3 is a schematic flow diagram of a process for
producing ethanol from corn.
[0013] FIG. 4A shows the removed components (e.g., whole stillage),
which comprise water, soluble components, oil and unfermented
solids (e.g., the solids component of the beer with substantially
all ethanol removed), can be dried into distillers dried grains
(DDG) and sold as an animal feed product.
[0014] FIG. 4B shows the treatment system which may comprise a
separation (to produce thin stillage and wet grains), a second
treatment system and a dryer, and produces an oil composition and
distillers dried grains plus solubles.
[0015] FIGS. 5A and 5B show the second treatment system (i.e. the
oil separation system).
[0016] FIGS. 6A and 6B show the treatment system.
[0017] FIG. 7 shows the effect of pH on the fatty acid content of
the oil composition.
[0018] FIG. 8 shows the effect of pH on the oil separation from the
emulsion.
[0019] FIG. 9A shows the fatty acid content of the oil samples
[0020] FIG. 9B shows the insolubles content of the oil samples
[0021] FIG. 9C shows the moisture content of the oil samples
[0022] FIG. 9D shows the phospholipids content of the oil
samples
[0023] FIG. 10 show the peroxide value of oils stored at 40.degree.
C. in the dark.
[0024] FIG. 11 show the hexanal content of oils stored at
40.degree. C. in the dark.
[0025] FIG. 12 show the peroxide value of CS-2 oil during storage
at 20.degree. C.
[0026] FIG. 13 shows an exemplary process flow diagram.
[0027] FIGS. 14A, 14B, 14C, 14D and 14E show various flow diagrams
for providing the oil composition and the distillers dried grains
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] This invention relates to a corn oil composition and a
method for producing the same.
[0029] It is to be understood that this invention is not limited to
particular embodiments described, as such may, of course, vary. It
is also to be understood that the terminology used herein is for
the purpose of describing particular embodiments only, and is not
intended to be limiting, since the scope of this invention will be
limited only by the appended claims.
[0030] It must be noted that as used herein and in the appended
claims, the singular forms "a", "an", and "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "an alkali metal ion" includes a plurality of
alkali metal ions.
1. Definitions
[0031] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. As used
herein the following terms have the following meanings.
[0032] As used herein, the term "comprising" or "comprises" is
intended to mean that the compositions and methods include the
recited elements, but not excluding others. "Consisting essentially
of" when used to define compositions and methods, shall mean
excluding other elements of any essential significance to the
combination for the stated purpose. Thus, a composition consisting
essentially of the elements as defined herein would not exclude
other materials or steps that do not materially affect the basic
and novel characteristic(s) of the claimed invention. "Consisting
of" shall mean excluding more than trace elements of other
ingredients and substantial method steps. Embodiments defined by
each of these transition terms are within the scope of this
invention.
[0033] As used herein, the term "about" when used before a
numerical designation, e.g., temperature, time, amount, and
concentration, including range, indicates approximations which may
vary by (+) or (-) 10%, 5% or 1%.
[0034] As used herein, the term "unrefined corn oil" refers to corn
oil which has not been subjected to a refining process, such as
alkali refining or physical refining (i.e., distillation,
deodorization, bleaching, etc.).
[0035] As used herein, the term "free fatty acid" refers to an
unesterified fatty acid, or more specifically, a fatty acid having
a carboxylic acid head and a saturated or unsaturated unbranched
aliphatic tail (group) of from 4 to 28 carbons. The term
"aliphatic" has it generally recognized meaning and refers to a
group containing only carbon and hydrogen atoms which is straight
chain, branched chain, cyclic, saturated or unsaturated but not
aromatic.
[0036] As used herein, the term "moisture content" refers to the
amount of water and other soluble components in the oil
composition. The moisture in the corn oil composition contains the
alkali and/or alkaline metal, and may contain other soluble
components, such as volatile material including hexane, ethanol,
methanol, and the like.
[0037] As used herein, the term "an alkali metal ion" refers to one
or more metal ion of Group 1 of the periodic table (e.g. lithium
(Li.sup.+), sodium (Na.sup.+), potassium (K.sup.+), etc.).
[0038] As used herein, the term "an alkaline metal ion" refers to a
metal ion of Group 2 of the periodic table (e.g. magnesium
(Mg.sup.2+), calcium (Ca.sup.2-), etc.).
[0039] As used herein, the term "insoluble" refers to material in
the oil which is not solvated by the aqueous portion, the oil or
the moisture content within the oil.
[0040] As used herein, the term "unsaponifiables" refers to
components of the oil that do not form soaps when blended with a
base, and includes any variety of possible non-triglyceride
materials. This material can act as contaminants during biodiesel
production. Unsaponifiable material can significantly reduce the
end product yields of the oil composition and can, in turn, reduce
end product yields of the methods disclosed herein.
[0041] As used herein, the term "peroxide value" refers to the
amount of peroxide oxygen (in millimoles) per 1 kilogram of fat or
oil and is a test of the oxidation of the double bonds of the oils.
The peroxide value is determined by measuring the amount of iodine
(I.sup.-) via colorimetry which is formed by the reaction of
peroxides (ROOH) formed in the oil with iodide via the following
equation: 2 I.sup.-+H.sub.2O+ROOH.fwdarw.ROH+20H.sup.-+I.sub.2.
[0042] As used herein, the term "oxidative stability index value"
refers to the length of time the oil resists oxidation at a given
temperature. Typically, the oxidation of oil is slow, until the
natural resistance (due to the degree of saturation, natural or
added antioxidants, etc.) is overcome, at which point oxidation
accelerates and becomes very rapid. The measurement of this time is
the oxidative stability index value.
[0043] As used herein, the term "corn fermentation residue" refers
to the residual components of a corn fermentation process after the
ethanol has been recovered, typically via distillation. Typically,
the corn fermentation residue comprises water, any residual starch,
enzymes, etc.
[0044] As used herein, the term "syrup" refers to the viscous
composition which is provided by the evaporation of the thin
stillage.
[0045] As used herein, the term "base" refers to a compound or
composition which raises the pH of an aqueous solution. Suitable
bases for use in this invention include, but are not limited to,
sodium hydroxide, potassium hydroxide, calcium hydroxide, or spent
alkali wash solution.
[0046] As used herein, the term "alkali wash solution" refers to
the basic solution which is used to disinfect the fermentor after
the fermentation process has been completed. The alkali wash
solution typically comprises sodium hydroxide.
2. Embodiments
[0047] This invention generally relates to oil compositions
recovered from a fermentation byproduct. The oil compositions
contain low levels of free fatty acids making them valuable for use
in bio-diesel, edible and nutraceutical applications. This
invention also relates to methods of recovering such oil
compositions from a fermentation process.
[0048] The corn oil of this invention is provided by the
fermentation of corn in the production of ethanol. Referring to
FIGS. 2 and 3, in a typical exemplary ethanol production process,
corn can be prepared for further treatment in a preparation system.
As seen in FIG. 3, the preparation system may comprise a cleaning
or screening step to remove foreign material, such as rocks, dirt,
sand, pieces of corn cobs and stalk, and other unfermentable
material. After cleaning/screening, the particle size of corn can
be reduced by milling to facilitate further processing. The corn
kernels may also be fractionated into starch-containing endosperm
and fiber and germ. The milled corn or endosperm is then slurried
with water, enzymes and agents to facilitate the conversion of
starch into sugar (e.g. glucose). The sugar can then be converted
into ethanol by an ethanologen (e.g. yeast) in a fermentation
system. In one embodiment, the fermentation is carried out without
creating a hot slurry (i.e., without cooking). In such an
embodiment, the fermentation includes the step of saccharifying the
starch composition with an enzyme composition to form a
saccharified composition (e.g., without cooking). In one embodiment
the starch composition comprises water and from 5% to 60% dried
solids granular starch, based on the total weight of the starch
composition. In another embodiment, the starch composition
comprises 10% to 50% dried solids granular starch, or 15% to 40%
dried solids granular starch, or 20% to 25% dried solids granular
starch, based on the total weight of the starch composition.
[0049] The fermentation product is beer, which comprises ethanol,
water, oil, additional soluble components, unfermented particulate
matter, etc. The fermentation product can then be distilled to
provide ethanol, leaving the remaining components as whole
stillage. The whole stillage can then be separated to provide a
liquid component (i.e. thin stillage) and a solid component. The
solid component can be dried to provide the distillers dried grain
of this invention, whereas the thin stillage can be taken on to
provide the oil compositions of this invention.
Corn Oil Compositions
[0050] One aspect of this invention provides an unrefined corn oil
composition comprising having a free fatty acid content of less
than about 5 weight percent; a moisture content of from about 0.2
to about 1 weight percent; and an alkali metal ion and/or alkaline
metal ion content of greater than 10 ppm. The unrefined corn oil of
this invention has not been subjected to a refining process. Such
refining processes include alkali refining and/or physical refining
(i.e., distillation, deodorization, bleaching, etc.), and are used
to lower the free fatty acid content, the moisture content, the
insoluble content and/or the unsaponifiables content.
[0051] The free fatty acid content of the present unrefined corn
oil composition is less than about 5 weight percent. The oil
composition described herein has a free fatty acid content level
that can reduce the amount of front-end refining or processing for
use in bio-diesel production. The fuel properties of bio-diesel are
determined by the amounts of each fatty acid in the feedstock used
to produce the fatty acid methyl esters. In some embodiments, the
free fatty acid content comprises at least one fatty acid selected
from the group consisting of C.sub.16 palmitic, C.sub.18 stearic,
C.sub.18-1 oleic, C.sub.18-2 linoleic, and C.sub.18-3 linolenic
(where the number after the "-" reflects the number of sites of
unsaturation). In some embodiments, the free fatty acid content is
less than 5 weight percent. For example, in some embodiments, the
free fatty acid content is less than about 4 weight percent, or
alternatively, less than about 3 weight percent, or alternatively,
less than about 2 weight percent, or alternatively, less than about
1 weight percent.
[0052] Maintaining low levels of moisture is advantageous as
moisture can result in the formation of free fatty acids. The
unrefined corn oil composition of this invention has a moisture
content of less than about 1 weight percent. The moisture in the
present corn oil composition can comprise water along with other
soluble components, such as one or more alkali and/or alkaline
metal, and may further contain other soluble components, such as
volatile material including hexane, ethanol, methanol, and the
like. The pH of the water that makes up the moisture content is, in
general, alkaline (i.e., >7) and comprises the one or more
alkali and/or alkaline metals. In some embodiments, the moisture
content of the unrefined corn oil composition is from about 0.2 to
about 1 weight percent, or alternatively, about or less than about
0.8 weight percent, or alternatively, about or less than about 0.6
weight percent, or alternatively, about or less than about 0.4
weight percent, or alternatively, about 0.2 weight percent. In
certain embodiments, the metal ion concentration of the moisture
content is about 2,000 ppm. Accordingly, an unrefined corn oil
composition having from about 0.2 to about 1 weight percent would
have a metal ion concentration of from about 4 ppm to about 20 ppm.
Typically, the moisture content of the unrefined corn oil
composition is about 0.5 weight percent having a metal ion
concentration of about 2000 ppm, resulting in an ion concentration
in the oil composition of about 10 ppm. In some embodiments, the
unrefined corn oil composition has a metal ion concentration of
greater than about 0.4 ppm, or greater than about 0.5 ppm, or
greater than about 0.6 ppm, or greater than about 0.7 ppm, or
greater than about 0.8 ppm, or 20 ppm.
[0053] As is stated above, the moisture content is, in general,
alkaline (i.e., >7). Accordingly, the water content in the oil
comprises an alkali metal ion and/or alkaline metal ion content of
or greater than about 10 ppm. The alkali metal ion present in the
composition can be any alkali metal ion and/or any alkaline metal
ion, and is in some embodiments, any combination of lithium
(Li.sup.+), sodium (Na.sup.+), magnesium (Mg.sup.2+), potassium
(K.sup.+) and/or calcium (Ca.sup.2+).
[0054] In some embodiments, the alkaline moisture content can
comprise an organic base, such as ammonia and/or ammonium ions.
Accordingly, in one embodiment, this invention is directed to an
unrefined corn oil composition comprising having a free fatty acid
content of less than about 5 weight percent; a moisture content of
from about 0.2 to about 1 weight percent; and an ammonia and/or
ammonium ion content of greater than about 10 ppm, or from about 4
ppm to about 20 ppm.
[0055] In some embodiments, the unrefined corn oil has an insoluble
content of less than about 1 weight percent. The insoluble content
is not solvated by the aqueous portion, the oil or the moisture
within the oil, and can include material such as residual solid
(e.g. corn fiber).
[0056] In some embodiments, the unrefined corn oil has an
unsaponifiables content less than about 3 weight percent, or less
than about 2 weight percent, or less than about 1 weight percent.
Unsaponifiable matter can significantly reduce the end product
yields of the oil composition and can, in turn, reduce end product
yields of the methods disclosed herein. The unsaponifiables content
of the oil does not form soaps when blended with a base, and
includes any variety of possible non-triglyceride materials that
act as contaminants during biodiesel production.
[0057] The unrefined corn oil of this invention can further
comprise various other oil soluble components. It is contemplated
that the amount of such components would not be so much that the
unrefined corn oil composition would require refining prior to
being used as a biodiesel, for example. Such components can
include, for example, one or more of lutein, cis-lutein,
zeaxanthin, alpha-cryptoxanthin, beta-cryptoxanthin,
alpha-carotene, beta-carotene, cis-beta-carotene, alpha-tocopherol,
beta-tocopherol, delta-tocopherol, or gamma-tocopherol,
alpha-tocotrienol, beta-tocotrienol, gamma-tocotrienol, and/or
delta-tocotrienol. In some embodiments, the unrefined corn oil
composition has a tocopherol content less than about 1 mg/g. In
some embodiments, the unrefined corn oil composition has a
tocotrienol content less than about 1.3 mg/g. In some embodiments,
the unrefined corn oil composition has a beta-carotene content
greater than about 2 .mu.g/g. Such components are known
antioxidants and can thus provide an oxidative stability to the
unrefined corn oil composition.
[0058] The unrefined corn oil composition of this invention
exhibits a high level of oxidative stability than corn oils
prepared via conventional methods. This can be due to any
combination of factors, such as, the degree of saturation of the
oil, the natural antioxidants, and the like, and can easily be
determined using methods well known in the art. In some
embodiments, the oxidative stability of the unrefined corn oil
composition is greater than about 4 hours at a temperature of about
110.degree. C. (See Example 4). Further, the oxidative stability
can be assessed using its peroxide value. In some embodiments, the
unrefined corn oil composition exhibits a peroxide value of less
than about 2 parts per million, or less than 1 part per
million.
Methods
[0059] One aspect of this invention is directed to a method for
providing a corn oil composition from a corn fermentation residue
comprising the steps of: [0060] b) adjusting the pH of the corn
fermentation residue to provide a corn oil layer and an aqueous
layer; and [0061] c) separating the corn oil layer from the aqueous
layer to provide the corn oil composition.
[0062] One aspect of this invention is directed to a method for
providing a corn oil composition from a corn fermentation residue
comprising the steps of: [0063] a) separating the corn fermentation
residue to provide an emulsion layer and a first aqueous layer;
[0064] b) adjusting the pH of the emulsion layer to provide a corn
oil layer and a second aqueous layer; and [0065] c) separating the
corn oil layer from the second aqueous layer to provide the corn
oil composition.
[0066] In some embodiments, the corn fermentation residue of this
invention comprises whole stillage. In a fermentation process, the
whole stillage is the remaining components of the fermentor after
the ethanol has been distilled. The whole stillage comprises a
solid component and a liquid component. The liquid component of the
whole stillage is referred to herein as thin stillage (FIG. 4A). In
one embodiment, the whole stillage can be subjected to further
processing steps to produce thin stillage. Thin stillage can be
recovered from the solid component of the whole stillage by natural
phase separation and decanting, or can be accelerated using methods
such as centrifugation. In one embodiment, the solid component of
the whole stillage can be subjected to drying to provide distillers
dried grain and sold as an animal feed product. In some
embodiments, the corn fermentation residue comprises thin stillage.
In one embodiment, moisture can be removed from the thin stillage
to create a concentrated fermented product, herein referred to as
syrup. Moisture can be removed in a variety of ways such as, for
example, through evaporation under vacuum which, in turn, can
prevent fouling. Accordingly, in some embodiments, the corn
fermentation residue comprises syrup. In some embodiments, the corn
fermentation residue has a moisture content of between about 95%
and about 60% weight percent. In some embodiments, the corn
fermentation residue has a moisture content of about 95%, or about
90%, or about 85%, or about 80%, or about 75%, or about 70%, or
about 65%, or about 60% weight percent.
[0067] The method of this invention optionally comprises the step
of separating the corn fermentation residue (whole stillage, thin
stillage, or syrup) to provide an emulsion layer and a first
aqueous layer. The step of separating can be accomplished by simply
allowing the phase separation to occur over time and the oil layer
decanted or by utilizing centrifuge or a combination thereof,
including, but not limited to, for example, a press, extruder, a
decanter centrifuge, a disk stack centrifuge, a screen centrifuge
or a combination thereof. In some embodiments, the separating does
not comprise heating. In one embodiment, a continuous flow at about
4000 g is maintained. One of ordinary skill in the art will
appreciate that the speed or amount of centrifugal force applied
will depend on various factors such as sample size and may be
adjusted appropriately depending on such factors. Suitable
separators and centrifuges are available from various manufacturers
such as, for example, Seital of Vicenza, Italy, Westfalia of Oelde,
Germany or Alfa Laval of Lund, Sweden.
[0068] In one embodiment, the resulting emulsion layer contains
from about 20% w/w to about 70% w/w oil. In another embodiment, the
emulsion layer contains from about 30% w/w to about 60% w/w oil. In
yet another embodiment, the emulsion layer contains from about 40%
w/w to about 50% w/w oil. The oil fraction may also comprise
varying amounts of the overall fermentation residue volume. In one
embodiment, the emulsion layer comprises about 20% w/w of the
initial fermented product volume.
[0069] In one embodiment, the step of separating the corn
fermentation residue is performed soon after initial production of
the ethanol in order to maintain oil composition quality and
prevent exposure to heat and oxygen, which are contributors to the
formation of free fatty acids. The emulsion layer, which comprises
the oil composition of this invention, is preferably separated from
the first aqueous layer. All or a fraction of the first aqueous
layer may be further processed or applied to solids such as, for
example, distillers dried grain.
[0070] In a preferred embodiment, once separated from the first
aqueous layer, the pH of the emulsion layer is adjusted such that
the emulsion is sufficiently broken, thus providing the oil
composition of this invention and a second aqueous layer. The pH
adjustment allows selective separation of higher quality oil while
leaving the free fatty acids in an aqueous fraction by saponifying
the fatty acids thus making them more water soluble. Thus, a
portion of the free fatty acid is removed resulting in oil that
contains low levels of free fatty acid. The age of the fermented
product and the organic acid content of the fermented product can
affect the optimum pH for separation, however, the oil fraction is
treated with the highest pH possible to reduce the overall free
fatty acid content in the separated oil without sacrificing oil
quality. Typically, suitable pH's range from about 7.5 to about 10.
The mixture of the free oil composition and oil fraction can be
removed for further processing.
[0071] In another embodiment, the first aqueous layer is not
removed from the emulsion layer but rather is subjected to base
treatment to form the oil layer and the second aqueous layer which
comprises both the first aqueous layer and water resulting from
breakage of the emulsion. The oil layer is then separated from the
second aqueous layer. Accordingly, in some embodiments, the method
comprises the steps of a) adjusting the pH of the corn fermentation
residue to provide a corn oil layer and a second aqueous layer; and
b) separating the corn oil layer from the second aqueous layer to
provide the corn oil composition. In some embodiments, the
separating steps do not comprise heating.
[0072] In some embodiments, the pH of the emulsion layer is lowered
by adding an acid. In one such embodiment, the pH can be adjusted
downward by about 1 pH unit, or about 2 pH units, or about 3 pH
units. It is contemplated that any inorganic or mineral acid can be
used for adjusting the pH of the emulsion layer.
[0073] In some embodiments, the pH of the emulsion layer is raised
by adding base. In one such embodiment, the pH can be adjusted
upward by about 1 pH unit, or about 2 pH units, or about 3 pH
units, or about 4 pH units, or about 5 pH units, or about 6 pH
units. In some embodiments, the pH of the emulsion layer is less
than about 4, or about 3.5, prior to the step of adjusting the pH
of the emulsion layer. It is contemplated that any inorganic or
mineral base can be used for adjusting the pH of the emulsion
layer. Suitable bases include, but are not limited to, a base
selected from the group consisting of sodium hydroxide, sodium
methoxide, potassium hydroxide, calcium hydroxide, or spent alkali
wash solution. In some embodiments, the base can be organic base,
such as ammonia. Efficient phase separation of the emulsion layer
can be achieved by adjusting the pH of the emulsion layer to about
7.5 to about 10, or from about 8 to about 9, or to a pH of about
8.2.
[0074] Once the emulsion has sufficiently broken, a corn oil layer
and a second aqueous layer are provided (FIGS. 5A and 5B). The corn
oil layer comprises the unrefined corn oil as disclosed herein.
[0075] In some cases, it may be that an interface layer is present
between the oil layer and the aqueous layer, which is known in the
art as a rag layer. The interface layer can comprise oil, water,
phospholipids, free fatty acids, solids, etc. In some embodiments,
the interface layer is substantially removed from the oil layer
with the aqueous layer. However, since the interface layer can
comprise a significant amount of oil, it may be advantageous to
extract the oil from the interface layer. Accordingly, in some
embodiments, the interface layer is kept with the oil layer and
subjected to the pH adjustment step. The volume of the interface
layer can be decreased by about 50% or more by using a greater
volume of aqueous solution compared to the volume of the oil layer.
Therefore, it may be advantageous to use a greater volume of
aqueous solution by adding water and/or using spent alkali wash
solution. Such methods may provide an oil having a lower
phospholipid concentration.
[0076] Accordingly, the unrefined corn oil as disclosed herein can
be provided by separating the corn oil layer from the second
aqueous layer. The step of separating the corn oil layer from the
second aqueous layer can be accomplished by simply allowing the
phase separation to occur over time and the oil layer decanted or
by utilizing centrifuge or a combination thereof, including, but
not limited to, for example, a press, extruder, a decanter
centrifuge, a disk stack centrifuge, a screen centrifuge or a
combination thereof (FIGS. 6A and 6B). In some embodiments, the
separating does not comprise heating. In one embodiment, a
continuous flow at about 4000 g is maintained. One of ordinary
skill in the art will appreciate that the speed or amount of
centrifugal force applied will depend on various factors such as
sample size and may be adjusted appropriately depending on such
factors. Suitable separators and centrifuges are available from
various manufacturers such as, for example, Seital of Vicenza,
Italy, Westfalia of Oelde, Germany or Alfa Laval of Lund,
Sweden.
[0077] In one embodiment, the second aqueous portion comprises 60%
to 80% moisture, based on the total weight of the second aqueous
portion. In one embodiment, the second aqueous portion comprises
10% to 40% protein, based on the total weight of the second aqueous
portion. In one embodiment, the second aqueous portion comprises up
to 50% oil, based on the total weight of the second aqueous
portion. The remainder of the second aqueous portion typically
comprises starch, neutral detergent fiber, and the like. The second
aqueous portion can be used to treat distillers dried grain or
other solids where an increased level of these components is
desirable.
Distillers Dried Grains
[0078] A shown in FIG. 4B, the treatment system may comprise a
separation (which produces thin stillage and wet grains), a second
treatment system and a dryer, and produces an oil composition and
distillers dried grains. The removed aqueous components from the
first and/or the second separation steps may be added onto the wet
grains in the dryer and dried to provide distillers dried grains
with solubles. Accordingly, in one embodiment, this invention
provides a distillers dried grain comprising about 4% or less fat,
or about 3% or less fat, or about 2% or less fat. In some
embodiments, the distillers dried grain further comprises about 20%
protein, or about 25% protein, or about 30% protein, about 35%
protein, or about 40% protein.
Uses
[0079] The oil composition of this invention can be used in a wide
variety of applications. Such exemplary applications include the
areas of oleochemicals, feed (e.g., animal feed) as well as oils
suitable for human consumption, and/or bio-diesel. Accordingly, one
embodiment of this invention is a bio-diesel comprising the
unrefined corn oil composition as described herein.
[0080] Oleochemicals include feedstock chemicals that are suitable
for bio-diesel production (fatty acid methyl esters). Industrial
oleochemicals are useful in the production of soaps, detergents,
wire insulation, industrial lubricants, leather treatments, cutting
oils, mining agents for oil well drilling, ink removal, plastic
stabilizers, ink and in rubber production. Other industrial
applications include waxes, shampoos, personal hygiene and food
emulsifier or additive products.
[0081] One embodiment of this invention is directed to a distillers
dried grain comprising about 4% or less fat. In some embodiments,
the distillers dried grain further comprises about 30% protein.
[0082] The corn oil of this invention can also be used for human
consumption. Products for human consumption include edible oils
that meet GRAS crude oil standards, as well as carriers for drug
molecules in pharmaceutical preparations. These products fits for
human consumption further include nutraceutical applications. The
oil compositions described herein contain higher than average
levels of various nutraceuticals such as, for example, tocopherols,
tocotrienols and phytosterols. In one embodiment and while not
intending to be bound to one particular theory, the oil
composition's higher than average levels of various nutraceuticals
can be attributable to the removal of corn oil directly from the
whole kernel as opposed to simply the corn germ itself. The
nutraceuticals in the present oil composition may be further
processed for inclusion in various applications such as health
foods, dietary supplements, food supplements, and food
fortification products.
EXAMPLES
[0083] A series of examples were conducted according to an
exemplary embodiment of the system (as shown in the Figures) in an
effort to determine suitable apparatus and operating conditions for
the separation of pre-treated biomass.
Example 1
[0084] The pH level capable of providing an oil composition
containing a low level of free fatty acid was determined (FIG. 7).
First, an oil fraction in the form of an emulsion separated from
fermented product was adjusted to the pH levels of 7.7, 7.9, 8.0,
8.1, 8.2, and 8.3. The samples were then centrifuged to separate
the oil composition and the oil composition was analyzed for free
fatty acid content. This experiment was conducted twice. The
results of each experiment, Experiment 1 and Experiment 2, are
shown in Table 1.
[0085] In summary, those samples tested at lower pH (i.e., below
8.0) exhibited free fatty acid contents above 3.5% w/w while those
tested at a pH above 8.1 exhibited a free fatty acid content of
below 2% w/w.
TABLE-US-00001 TABLE 1 pH 7.7 7.9 8.0 8.1 8.2 8.3 Free Fatty Acids
(percent) 3.5 2.2 2.0 2.2 2.0 1.8 Experiment 1 Free Fatty Acids
(percent) 4.8 3.5 3.1 2.2 2.0 1.8 Experiment 2
Example 2
[0086] Experiments were conducted to determine the amount of free
oil present upon adjustment of the oil fraction to various pH
levels (FIG. 8). A series of oil fractions, in the form of
emulsions samples previously separated by a first application of a
centrifugal force were treated with NaOH to adjust the pH to
various levels as shown in Table 2. Each sample contained the same
amount of oil before adjusting the pH. After adjusting the pH to
the targeted value, the volume of free oil was measured.
[0087] In summary, the optimum pH was obtained at about 8.2 as
evidence by the highest value of free oil volume. The volume of
free oil was shown to increase up to this value and then
deteriorate thereafter. Thus, an optimum pH for separation exists
for each oil fraction sample.
TABLE-US-00002 TABLE 2 pH 7.0 7.4 7.8 8.0 8.2 8.4 8.8 9.2 10.0 Free
Fatty Acids (percent) 1.0 30 42 45 60 48 50 45 43 Experiment 1
Example 3
[0088] Experiments were conducted to demonstrate that the
combination of adjusting the pH and applying a centrifugal force
resulted in (a) higher quality corn oil compositions and (b) higher
corn oil composition yield compared to those oil compositions
obtained upon application of a centrifugal force alone (FIGS. 9A,
9B, 9C and 9D). T he free fatty acid content was shown to be
reduced by up to 3% by adjusting the pH in combination with
centrifugal force as opposed to centrifugal force alone. The yield
of separated oil composition was increased by 140%. The experiment
was run for about 30 days, and includes 3 daily samples.
[0089] A compositional analysis of the products obtained from one
embodiment of the system was performed. The results are summarized
in Table 3. The syrup fraction obtained from the ethanol production
process was centrifuged to separate into a light fraction
(emulsified oil) and a heavy fraction (stickwater). The syrup
obtained was mostly free of oil. The heavy fraction was returned to
the normal process to be further evaporated and added to wet cake
and dried.
[0090] The pH of the light fraction was raised to approximately 8.2
from a pH of approximately 3.5. The pH adjusted emulsified material
was fed to a second centrifuge step. The heavy fraction (soapstock)
from the second centrifuge step was high in soaps and proteins and
was mixed with the stickwater and added to the wet cake and dried.
The light fraction from the second centrifuge was oil. The oil
exhibited a high quality and low free fatty acid content (see FIG.
9A), insolubles (see FIG. 9B), moisture (see FIG. 9C),
phospholipids (see FIG. 9D) and unsaponifiables. The oil provided
an excellent feedstock for biodiesel production and could be used
in food applications with further refining. The distiller's dried
grains composition projected to result from the combination of wet
cake, soapstock, and low fat syrup exhibited lower fat and higher
protein than typical for distillers dried grain.
TABLE-US-00003 TABLE 3 Fat Protein Moisture Other (percent)
(percent) (percent) (percent)*** Starting Material* 5.4 4.1 80 10
First Light 35 3.6 55 6.8 Fraction (Emulsified Oil)* First Heavy
3.5 4.2 83 10 Fraction (Stickwater)* Second Light 98 0.0 0.8 1.6
Fraction (Oil Composition)* Second Heavy 5.5 5.9 77 11 Fraction
(Soapstock)* Low Fat DDGS** 4.0 30 8.7 57 *Sampled, **Projected,
***Includes fiber, ash, starch, etc.
Example 4
[0091] In a conventional dry-grind ethanol process, whole corn is
ground to a flour, mixed with water and cooked at a high
temperature to gelatinize the starch and to make it more available
for subsequent liquefaction and saccharification by enzymes. The
cooked mash is then cooled to facilitate fermentation of the sugars
into ethanol. The resulting beer includes soluble and insoluble
components, such as proteins, oil, fiber, residual starch and
glycerol. The beer is separated into ethanol and whole stillage in
distillation. The whole stillage can be dewatered to produce wet
cake by removing a thin stillage component by centrifugation. The
oil partitions fairly equally, by weight, between thin stillage and
the wet cake. Thin stillage is typically further evaporated into
syrup, which can be added back onto the wet cake during a drying
process that produces distillers dried grains with solubles (i.e.
DDGS). Corn oil can be recovered from the syrup by a simple
centrifuging step, as described for example in a U.S. patent to GS
Cleantech Corporation (patent serial number U.S. Pat. No.
7,601,858).
[0092] Some dry-grind ethanol processing facilities utilize a
modified dry grind process known as raw starch ethanol production.
In these facilities, the corn is ground to fine flour, mixed with
water and enzymes, and fermented to ethanol-containing beer in a
simultaneous saccharification and fermentation reaction. The rest
of the raw starch process is similar to the conventional process.
However, in the raw starch process the oil cannot be separated from
the syrup by a simple centrifugation step, but requires an
additional treatment step (pH adjustment) and a second
centrifugation step to recover the oil. Overall, raw starch ethanol
production requires less energy and cooling water.
[0093] Oil extracted from corn DDGS using solvents, and oil
extracted centrifugally from thin stillage have been characterized.
These oils have similar, or slightly lower concentrations of
tocopherols than corn germ oil, but have higher concentrations of
phytosterols, tocotrienols, and steryl ferulates, than corn germ
oil. However, the oils also tend to have high free fatty acid
composition, which is detrimental to biodiesel production as well
as to oxidative stability. The ethanol plants supplying the
distillers grains for oil extraction in the aforementioned studies
were all running the conventional dry-grind ethanol process. To our
knowledge, oil extracted from distillers grains from the raw starch
ethanol process hasn't been characterized. The oxidative stability
of post-fermentation corn oil has not been studied either.
[0094] The present example provides the following: 1. To compare
the fatty acid and phytochemical composition of oils extracted from
corn germ, thin stillage, and DDGS; 2. Evaluate and compare the
oxidative stability of these oils; and 3. Determine the oxidative
stability of oil extracted from thin stillage at room
temperature.
Materials and Methods:
Chemicals
[0095] Dry chemicals (ACS grade or better) were obtained from
Sigma-Supelco (St. Louis, Mo.) unless otherwise noted in referenced
methods. Solvents were HPLC grade and were obtained from Fisher
(Fairlawn, N.J.).
Oils
[0096] The five oils that were characterized included hexane
Soxhlet extracts of corn germ (CG) and DDGS (DDGS), and three oils
that were centrifugally extracted from dry grind ethanol production
facilities (CS-1, CS-2, CS-3). The corn germ was obtained from an
ethanol production facility that operates a dry fractionation
process where the corn kernels are separated into germ, fiber, and
endosperm fractions prior to fermentation. Corn DDGS was obtained
from a raw starch ethanol production facility operated by POET, LLC
(Sioux Falls, S.D.). CG and DDGS were extracted overnight (-20 hr)
by Soxhlet extraction using hexane. Four parallel Soxhlet
extractors with .about.100 g/thimble were used several days in a
row and the extracts were combined to obtain enough oil from the
germ and DDGS for analyses and storage studies. Hexane was removed
by rotary evaporation at 40.degree. C., oil was then stirred for 4
hr under a high vacuum to remove any excess hexane, after which the
oil was put into several amber bottles, topped with argon to
prevent lipid oxidation, and frozen at -20.degree. C. until used
for analyses. CS-1 was obtained from a conventional dry grind
ethanol plant. CS-2 and CS-3 were obtained from two different
production runs from a raw starch ethanol production facility
operated by POET. CS-1, CS-2, and CS-3 were shipped overnight, on
dry ice, to the research location, and immediately transferred to
glass bottles, topped with argon, and frozen (-20.degree. C.) until
used for analyses.
Oil Analysis
Acid Value
[0097] Acid Value was determined by titration using AOCS official
method Cd 3d-63 (AOCS, 1998). The acid value was used to calculate
the percent free fatty acids (FFA) as percent oleic acid by
dividing the acid value by 1.99 as stated in the method. Each oil
was analyzed in triplicate for Acid Value and the mean is
reported.
Fatty Acid Composition and Iodine Value
[0098] Oil triacylglycerols were transesterified using the method
described by Ichihara (1996). Fatty acid methyl esters were
analyzed in triplicate by GC as previously described (Winkler and
Warner, 2008). The Iodine Values were calculated based on the fatty
acid composition according to the AOCS Method Cd 1c-85 (AOCS,
1998).
Tocopherols, Phytosterols, and Steryl Ferulate Analysis
[0099] The contents of tocopherols, tocotrienols, and steryl
ferulates were analyzed in triplicate in the crude oils by HPLC
with a combination of UV and fluorescence detection as previously
described (Winkler et al., 2007). In order to analyze total
phytosterol content and composition, the oils were saponified, and
the phytosterols were extracted and derivatized as previously
described (Winkler et al., 2007). Phytosterols were quantitated by
GC as described by Winkler and Vaughn (2009). The identity of
phytosterol peaks was confirmed by GC-MS analysis performed on an
Agilent (Santa Clara, Calif., USA) 6890 GC-MS equipped with a
HP-5MS capillary column (30 m 9 0.25 mm 9 0.25 lm), a 5973 mass
selective detector, and an 7683 autosampler. The transfer line from
GC to the MSD was set to 280.degree. C. The injector and oven
temperature programs were the same as described above for the
GC-FID instrument. MSD parameters were as follows: scan mode,
50-600 amu, ionizing voltage, 70 eV, and EM voltage, 1,823 V. Mass
spectral identification was performed using the Wiley MS database
combined with comparison to literature values for relative RT
(compared to .beta.-sitosterol) and mass spectra (Beveridge et al.,
2002).
Carotenoid Analysis
[0100] Carotenoid analysis and quantitation were conducted by HPLC
as described by Winkler and Vaughn (2009).
Oxidative Stability Index
[0101] The OSI at 110.degree. C. was determined in triplicate
following the AOCS Official Method Cd 12b-92 (AOCS, 1998). A
Metrohm (Herisau, Switzerland) 743 Rancimat with software control
automatically controlled air flow and temperature and calculated
the OSI values based on induction time.
Accelerated Storage Study
[0102] The study protocol followed AOCS Recommended Practice Cg
5-97 (AOCS, 1998). Oil samples (5 g) were weighed into 40-ml amber
glass vials which were loosely capped. For each treatment and day,
triplicate vials were prepared. Vials were stored in completely
randomized order in a dark oven held at 40.+-.1.degree. C. For each
oil, three vials were removed on days one through six and on day
eight. CG oil samples were also removed on days 10 and 12. However,
as the study progressed, it was determined that the DDGS and CS-2
oils were oxidizing more slowly than the CG oil, so samples were
removed on days 12 and 14 order to extend their storage by two more
days. Upon removal from the oven, vials were immediately topped
with argon, tightly capped, and frozen (-20.degree. C.) until
analysis. Analyses were conducted either on the same day or within
2 days of removal from the oven. Peroxide values were determined
using the method described by Shantha and Decker (1994). Each oil
replicate from the storage studies was analyzed in duplicate.
Hexanal in the oil headspace of each replicate was quantified in
duplicate by solid-phase microextraction (SPME) and GC analysis as
described by Winkler and Vaughn (2009).
Room Temperature Storage Study
[0103] CS-2 oil was placed into three, 4 L amber bottles. Each
bottle was filled to the same volume level of 3.4 L. The amount of
headspace above the oil samples amounted to 0.9 L. Bottles were
tightly capped and stored in the dark at 20.degree. C..+-.3.degree.
C., the temperature was monitored daily and the high and low
temperature was recorded. Samples were taken once a week for 13
weeks. To sample, bottles were first gently shaken for 30 s to mix
the contents. Then a glass pipet was inserted into the center of
the bottle and 5 ml oil was taken and placed into a screw cap vial,
covered with argon, and frozen (-20.degree. C.) until analysis.
Peroxide value and headspace analysis of hexanal were performed on
the oil samples as described above, and were typically run on the
same day or within 1-2 days of sampling.
Results
Fatty Acid Composition and Free Fatty Acids
[0104] The fatty acid compositions (Table 4) of all five oils were
typical for corn oil. The Iodine Values ranged from 122.4 to 124.3.
These results concur with other reports that the fatty acid
composition of oil extracted from DDGS and thin stillage are
similar to corn oil. The two oils (CS-1 and CS-2) that were
centrifugally extracted from syrup from the raw starch ethanol
production facilities had the lowest % FFA (2.03% and 2.48%,
respectively). The oil recovered by centrifugation of syrup from
the traditional dry grind ethanol production plant had the highest
Acid Value, with 10.1% FFA. Other studies have reported FFA content
of oil recovered by centrifugation of thin stillage ranging from
11.2-16.4%. These results indicate that the elimination of the
cooking step in the raw starch process reduces the production of
FFA. The oil extracted from DDGS using hexane had the second
highest acid value (7.42% FFA). Winkler-Moser and Vaughn (J. Am.
Oil Chem. Soc., 2009, 86, 1073-1082) reported FFA content of 6.8%
(w/w) in hexane Soxhlet extracted DDGS oil, while Moreau et al. (J.
Am. Oil Chem. Soc., 2010b, In Press) reported FFA content ranging
from 8-12% in DDGS that was extracted with hexane using accelerated
solvent extraction. FFA content of DDGS extracts has been shown to
vary widely depending on the extraction method and conditions and
on the solvent used. The DDGS used in this study also came from a
raw starch ethanol plant, so it might be expected to have lower
FFA. However, high temperatures used to dry the wet grains may have
contributed to the increase in FFA. In one experiment, Moreau et
al. (J. Am. Oil Chem. Soc., 2010b, In Press) demonstrated that oil
extracted from thin stillage and distillers dried grains (prior to
mixing the grains with the syrup) had high FFA content that carried
through to the DDGS. The FFA content of hexane extracted corn germ
was 3.8%, which is slightly higher than the average of 2.5% FFA
typically found in crude corn germ oil. For biodiesel production,
oil with an Acid Value greater than one requires pretreatment
because the free fatty acids form soaps during base-catalyzed
esterification, which interfere with the separation of the glycerol
from the fatty acid methyl esters. Thus, crude oils with lower free
fatty acids will have lower oil loss due to the pre-treatment. Free
fatty acids decrease the oxidative stability of oils and can also
precipitate at ambient temperatures, both of which could negatively
impact fuel performance.
TABLE-US-00004 TABLE 4 Acid value, fatty acid composition, and
calculated Iodine Value of oils extracted from corn germ (CG),
distillers dried grains with soluble (DDGS), and centrifugally
extracted thin stillage syrup (CS-1, CS-2, CS-3) CG DDGS CS-1 CS-2
CS-3 Acid Value (mg KOH/g) 10.7 .+-. 0.07 20.8 .+-. 0.36 28.3 .+-.
0.32 5.70 .+-. 0.13 6.88 .+-. 0.09 FFA (% oleic acid) 3.80 .+-.
0.03 7.42 .+-. 0.13 10.1 .+-. 0.11 2.03 .+-. 0.05 2.48 .+-. 0.05
Fatty Acid Composition (%) 16:0 13.1 12.9 11.5 12.2 12.9 16:1 0.0
0.1 0.1 0.1 0.1 18:0 1.5 1.8 1.7 1.8 1.5 18:1 29.2 28.1 29.3 28.3
27.5 18:2 55.0 55.5 55.6 55.3 55.9 20:0 0.2 0.3 0.3 0.4 0.3 18:3
1.0 1.2 1.17 1.2 1.2 20:1 0.0 0.0 0.2 0.3 0.2 Calculated Iodine
Value 122.4 123.1 124.3 123.7 124.1
Content and Composition of Tocopherols, Tocotrienols, and
Carotenoids
[0105] Tocopherols are common in vegetable oils and are the primary
antioxidants protecting most oils. With corn and other plants, the
tocopherol and tocotrienol content will vary based upon factors
including hybrid, growth conditions, post-harvesting and processing
conditions, as well as the type of solvent used for extraction.
Therefore, in this study little can be inferred about how
processing practices affected tocopherol levels since each
production facility and even each production run will have started
with different batches of whole corn. Gamma- and alpha-tocopherol
were the most prominent homologues detected in all five oils (Table
5), along with a small amount of delta-tocopherol, which is the
typical tocopherol profile for corn oil. CG oil had the highest
total concentration of tocopherols (1433.6 .mu.g/g oil) followed by
the hexane extracted DDGS (1104.2). The levels in the DDGS oil are
similar to what was previously reported in hexane extracted DDGS
from a conventional dry grind production facility. Tocopherols in
corn are localized in the germ portion of the kernel, so the rest
of the corn kernel contributes little to the tocopherol content.
CS-1, CS-2, and CS-3 were all lower in alpha-tocopherol compared to
CG and DDGS oils, but were similar to levels reported in oil
extracted centrifugally from thin stillage (Moreau et al., J. Am.
Oil Chem. Soc., 2010a, In Press).
TABLE-US-00005 TABLE 5 Content of tocols and carotenoids, and the
oxidative stability index (OSI) at 110.degree. C., for oils
extracted from corn germ (CG), distillers dried grains with
solubles (DDGS), and centrifugally extracted thin stillage syrup
(CS-1, CS-2, CS-3) CG DDGS CS-1 CS-2 CS-3 Total Tocopherols
(.mu.g/g) 1433.6 1104.2 1056.9 931.3 783.4 Alpha-tocopherol 213.8
295.6 164.5 160.4 123.2 Gamma-tocopherol 1185.4 760.8 852.7 742.0
640.0 Delta-tocopherol 34.3 47.8 39.7 28.8 20.2 Total Tocotrienols
(.mu.g/g) 235.6 1762.3 1419.6 1224.4 1175.2 Alpha-tocotrienol 21.9
471.9 328.5 243.6 269.4 Gamma-tocotrienol 165.6 1210.0 1063.6 963.4
880 Delta-tocotrienol 48.1 80.3 27.5 17.3 25.8 Total Carotenoids
(.mu.g/g) 1.33 75.02 129.48 61.1 85.0 Lutein 0.37 46.69 75.69 38.13
53.7 Zeaxanthin 0.4 24.16 45.58 16.78 23.7 Beta-cryptoxanthin 0.56
3.31 7.35 4.12 5.1 Beta-carotene ND.sup.a 0.86 0.86 2.07 2.5 OSI
(hr) 3.91 6.62 4.45 4.52 5.27 .sup.aNot detected
[0106] Tocotrienols are common in rice bran oil and palm oil, but
are not abundant in most commercial vegetable oils. Their
antioxidant activity is similar to tocopherols in bulk oil systems,
but they also appear to have hypocholesterolemic, anti-cancer, and
neuroprotective properties. The post-fermentation corn oils (DDGS,
CS-1, CS-2, and CS-3) were higher in tocotrienol concentration
compared to CG oil, because tocotrienols are found in the endosperm
fractions, which are mostly removed during the fractionation of
corn germ. Thus, despite having lower tocopherol concentration, all
of the post-fermentation oils were higher in total tocol
concentration compared to the CG oil.
[0107] The post-fermentation corn oils were much higher in
carotenoids than the extracted corn germ oil as well. However, the
concentration of carotenoids was substantially lower than the
tocols in five oils (Table 5). As with tocotrienols, carotenoids
are localized to the endosperm fraction of corn kernels. The main
carotenoids in the oils were lutein and zeaxanthin, as well as
lower quantities of beta-cryptoxanthin and beta-carotene.
Carotenoid content and composition were similar to amounts found in
DDGS oil in a previous study, however, Moreau et al. (J. Am. Oil
Chem. Soc., 2010a, In Press) reported carotenoid content in
centrifugally extracted thin stillage oil ranging from 295 to 405
.mu.g/g oil. Carotenoids are substantially affected by corn hybrid,
which may explain the discrepancy. Beta-carotene and
beta-cryptoxanthin are both precursors to Vitamin A, while lutein
and zeaxanthin are both protective against age-related macular
degeneration and cataracts. Carotenoids have also been shown to
have a number of beneficial physiological actions other than
Vitamin A activity, including antioxidant activity, enhanced immune
response, and chemoprotective activity against several types of
cancer.
Content and Composition of Phytosterols
[0108] The content of total phytosterols in the three oils ranged
from 1.5-2.0% (w/w) (Table 6). The post-fermentation corn oils were
higher in total phytosterols compared to the CG oil because they
include phytosterols and ferulate phytosterol esters from the bran
and pericarp, in addition to the phytosterols from the germ portion
of the corn kernel. The phytosterol composition is also different
between CG oil and the post-fermentation corn oils. DDGS and CS-1,
CS-2, and CS-3 oils had similar concentrations of the common
phytosterols campesterol, stigmasterol, and sitosterol compared to
CG oil. However, they had a much higher concentration of the two
saturated phytosterols (phytostanols), campestanol and sitostanol.
The high content of these phytostanols is due to their preferential
esterification, in corn, to steryl ferulates, the contents of which
are also shown in Table 6. Steryl ferulates are found in the inner
pericarp of corn and other grains. The presence of a small amount
of these compounds in the corn germ oil indicates that there may
have been some contamination of the germ by some inner pericarp
tissue, as it has been established that these compounds are unique
to the aleurone layer of the pericarp. Phytosterols are highly
valued as ingredients in functional foods due to their ability to
lower blood cholesterol by blocking re-adsorption of cholesterol
from the gut. Steryl ferulates have been shown to retain the
cholesterol lowering ability of phytosterols, and also have
antioxidant activity due to the ferulic acid moiety.
TABLE-US-00006 TABLE 6 Content and composition of phytosterols in
oils extracted from corn germ (CG), distillers dried grains with
solubles (DDGS), and centrifugally extracted thin stillage syrup
(CS-1, CS-2, CS-3). CG DDGS CS-1 CS-2 CS-3 mg/g %.sup.a mg/g % mg/g
% mg/g % mg/g % Total Phytosterols 14.9 21.7 18.7 20.1 20.2
Campesterol 3.08 20.7 2.97 13.7 2.74 14.7 2.74 13.6 3.0 14.7
Campestanol 0.25 1.7 1.35 6.2 1.40 7.5 1.30 6.5 1.4 6.7
Stigmasterol 0.98 6.6 1.10 5.1 0.76 4.1 0.91 4.5 0.89 4.4
Sitosterol 9.04 60.9 10.3 47.5 8.77 46.9 9.36 46.5 9.3 46.1
Sitostanol 0.66 4.4 3.72 17.2 3.59 19.2 3.45 17.2 3.2 16.0
Avenasterol 0.54 3.7 0.93 4.3 0.86 4.6 0.94 4.7 1.0 5.2
Cycloartenol 0.28 1.9 0.71 3.2 0.59 3.2 0.74 3.7 0.73 3.6
24-methylene ND.sup.b 0 0.30 1.4 ND 0 0.34 1.7 0.30 1.5
cycloartanol Citrostadienol ND.sup. 0 0.31 1.4 ND 0 0.31 1.6 0.36
1.8 Steryl Ferulates 0.58 3.9 3.42 15.7 3.15 16.8 3.38 16.8 3.35
16.6 (mg/g) .sup.aThe weight percentage of total phytosterols
.sup.bNot detected
Oxidative Stability Index (OSI)
[0109] The oxidative stability of oils are affected by many
factors, including fatty acid composition, concentration and
stability of antioxidants in the oil, and the presence of
prooxidant compounds, such as free fatty acids, lipid peroxides, or
prooxidant metals. The Rancimat is an accelerated test (taking
several hours to a day, depending on the oil and test temperature)
used to establish the relative oxidative stability of oils, as
measured by the induction time (called the oxidative stability
index, OSI) for an oil to begin oxidizing under controlled
temperature and air flow conditions. The OSI of the CG oil was
lowest, while DDGS oil had the highest stability (Table 5), which
corresponds to the lowest and the highest concentration of
antioxidant tocopherols. CS-1 had a slightly lower OSI than CS-2
and CS-3 despite having a higher concentration of tocols; this may
be explained by its higher content of FFA and higher initial
peroxide value.
Accelerated Storage Study
[0110] While the OSI is a quick method for determining relative
stability of various oils, it is often recommended that oil
stability be measured at lower temperatures as well, since
oxidation mechanisms change at higher temperatures. Peroxide value
is an indicator of the primary stage of lipid oxidation where lipid
radicals are attacked by oxygen to form lipid hydroperoxides. At
temperatures lower than 100.degree. C., lipid peroxides accumulate
until they begin to break down to form secondary oxidation products
including volatile aldehydes (e.g., hexanal), ketones, and esters.
The CG oil showed the highest rate of increase in peroxides when
stored at 40.degree. C., indicating that it was the most
susceptible to oxidation (FIG. 10). CS-1 and CS-2 were more stable
than the CG oil, but CS-2 was slightly more stable than CS-1. As a
point of comparison, it took CG 2-3 days to reach a peroxide value
of 10 mEq/Kg, 5 days for CS-1, and between 6-8 days for CS-2. The
hexane extracted DDGS oil was most stable, and did not show any
increase in peroxide value for the first 8 days of storage, after
which it increased at a slow rate and did not even reach a value of
5 mEq/kg by the end of the study. The trends in relative oxidative
stability were the same as predicted by the OSI values, however,
the OSI values did not demonstrate as clearly the differences in
stability of the four oils as seen in this evaluation at a lower
temperature.
[0111] As lipid hydroperoxides break down, they form volatile
compounds that can be measured in the headspace as indicators of
secondary lipid oxidation. Hexanal is produced from the
13-hydroperoxide of linoleic acid, and is therefore often used as a
reliable indicator of secondary lipid oxidation in oils that are
high in linoleic acid. At day 0 of the study, the CG and DDGS oils
had very low hexanal content, while CS-1 and CS-2 had about 1-1.4
.mu.g/g hexanal in the oil (FIG. 11). Since the CG and DDGS oils
were treated by rotary evaporation to remove hexane after
extraction, there may have been residual levels of hexanal (and
other volatile compounds) in these oils as well that were removed
by the rotoevaporation. The hexanal content increased to 4 .mu.g/g
in CG, but leveled off after day 8. In CS-1 and CS-2, hexanal
contents increased to 3 .mu.g/g and 4 .mu.g/g, respectively, and
also leveled off around 6 days of storage. Hexanal increased at a
slower rate in the DDGS oil, to a final level of 3 .mu.g/g. The
total hexanal content remained relatively low in all of the oils
throughout the storage study, indicating perhaps, that the hexanal
that formed during this time period was from the breakdown of
residual lipid peroxides already present in the three oils, and
that the process of accelerated peroxide breakdown and aldehyde
formation had not yet taken place. This is supported by the fact
that the peroxide values had not yet leveled off or decreased, as
is often seen in storage studies where oil is in the secondary
stages of lipid oxidation.
Room Temperature Storage Study
[0112] While the OSI and accelerated storage studies are useful for
determining the relative stability of oils with differing fatty
acid compositions or antioxidant levels, they still cannot be used
to predict shelf stability under real life conditions. Accelerated
storage studies would need to be performed over at least three
different temperatures and the induction periods would have to be
plotted in order to predict the induction period at a given
temperature. In order for oil derived from the ethanol production
process to be used in applications such as biodiesel production, it
is of interest to predict its stability during storage. Larger
volumes of CS-2 oil were stored in the dark at room temperature and
determined PV and hexanal content weekly to determine the induction
time under these conditions. There was not enough of the other oils
to include them in this portion of the study. The peroxide value
remained in a lag stage for 6 weeks, after which time it started to
slowly increase (FIG. 12). However, by 13 weeks of storage, it was
still below a peroxide value of 2.0 mEq/kg oil. Hexanal content in
the headspace was also measured weekly, but content remained the
same throughout the study indicating that the oil was still in the
primary stages of lipid oxidation by the end of the study.
Regression analysis of the oil PV based on the rate of increase
after the lag phase ended (weeks 7 through 13) predicted that it
would reach a PV of 10 mEq/Kg after approximately 58 weeks of
storage under these same conditions. This study could not be used
to predict the stability of the oil in commercial production
conditions where factors such as the surface area to volume ratio,
the use of inert gas in the headspace, and temperature fluctuations
would all impact the rate of lipid oxidation. However, the results
indicate that under ideal conditions of a low surface area to
volume ratio, room temperature, and limited light exposure, crude
thin stillage oil would likely remain oxidatively stable for
several months or more. This is an important issue for storage and
transport of the crude thin stillage oil prior to further
processing for biodiesel or other uses.
Conclusions
[0113] This Example compared the composition and oxidative
stability of oils extracted from corn germ, corn distillers dried
grains, and from thin stillage from a conventional dry grind
ethanol production facility as well as from a raw starch ethanol
production facility. The fatty acid compositions of all five oils
were typical for corn oil. Oil extracted from thin stillage in a
raw starch production facility has lower FFA than from thin
stillage from a conventional dry grind ethanol production facility.
This is likely due to lower processing temperatures used in the raw
starch process where the cooking stage is eliminated. All of the
post-fermentation oils had higher concentrations of tocotrienols,
carotenoids, phytosterols, and ferulate phytosterol esters compared
to the corn germ oil. The increased concentrations of the
antioxidant tocotrienols carotenoids, and steryl ferulates are
likely responsible for their increased stability compared to corn
germ oil.
[0114] Soybean oil is the most common feedstock for biodiesel, but
this study indicates that from the standpoint of fatty acid
composition and oxidative stability, oil extracted from thin
stillage would be an economical alternative. Considering that over
25 million metric tons of DDGS with roughly 10% oil are produced
from the ethanol industry each year, enough oil could be recovered
to offset a substantial amount of the soybean oil that is directed
to biodiesel production. This would result in two fuels, ethanol
and biodiesel, produced from a single feedstock.
[0115] The embodiments as disclosed and described in the
application (including the FIGURES and Examples) are intended to be
illustrative and explanatory of this invention. Modifications and
variations of the disclosed embodiments, for example, of the
apparatus and processes employed (or to be employed) as well as of
the compositions and treatments used (or to be used), are possible;
all such modifications and variations are intended to be within the
scope of this invention.
* * * * *