Note: Descriptions are shown in the official language in which they were submitted.
CA 02715072 2010-09-22
OIL COMPOSITION AND METHOD FOR PRODUCING THE SAME
FIELD
[0001] 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
[0002] 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).
[0003] 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.
[0004] 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.
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CA 02715072 2010-09-22
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.
[0005] 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
[0006] 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.
[0007] 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
[0008] FIGURE I A is a perspective view of a biorefinery comprising a
cellulosic
ethanol production facility.
[0009] FIGURE 1B is a perspective view of a biorefinery comprising a
cellulosic ethanol
production facility and a corn-based ethanol production facility.
[0010] FIGURE 2 is a schematic block flow diagram of a process for producing
ethanol
from corn.
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[0011] FIGURE 3 is a schematic flow diagram of a process for producing ethanol
from
corn.
[0012] FIGURE 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.
[0013] FIGURE 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.
[0014] FIGURES 5A and 5B show the second treatment system (i.e. the oil
separation
system).
[0015] FIGURES 6A and 6B show the treatment system.
[0016] FIGURE 7 shows the effect of pH on the fatty acid content of the oil
composition.
[0017] FIGURE 8 shows the effect of pH on the oil separation from the
emulsion.
[0018] FIGURE 9A shows the fatty acid content of the oil samples
[0019] FIGURE 9B shows the insolubles content of the oil samples
[0020] FIGURE 9C shows the moisture content of the oil samples
[0021] FIGURE 9D shows the phospholipids content of the oil samples
[0022] FIGURE 10 show the peroxide value of oils stored at 40 C in the dark.
[0023] FIGURE 11 show the hexanal content of oils stored at 40 C in the dark.
[0024] FIGURE 12 show the peroxide value of CS-2 oil during storage at 20 C.
[0025] FIGURE 13 shows an exemplary process flow diagram.
[0026] FIGURES 14A, 14B, 14C, 14D and 14E show various flow diagrams for
providing the oil composition and the distillers dried grains of the
invention.
DETAILED DECRIPTION OF THE INVENTION
[0027] This invention relates to a corn oil composition and a method for
producing the
same.
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[0028] 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.
[0029] 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
[0030] 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.
[0031] 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.
[0032] 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%orl %.
[0033] 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.).
[0034] 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
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atoms which is straight chain, branched chain, cyclic, saturated or
unsaturated but not
aromatic.
[0035] 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.
[0036] 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+), sodium (Na+), potassium
(K), etc.).
[0037] As used herein, the term "an alkaline metal ion" refers to a metal ion
of Group 2
of the periodic table (e.g. magnesium (Mg2+), calcium (Ca 2), etc.).
[0038] 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.
[0039] 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.
[0040] 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 (F)
via colorimetry which is formed by the reaction of peroxides (ROOH) formed in
the oil with
iodide via the following equation: 2 F + H2O + ROOH -> ROH + 20H- + 12-
[00411 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.
[0042] 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.
CA 02715072 2010-09-22
[0043] As used herein, the term "syrup" refers to the viscous composition
which is
provided by the evaporation of the thin stillage.
[0044] 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.
[0045] 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
[0046] 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.
[0047] The corn oil of this invention is provided by the fermentation of corn
in the
production of ethanol. Referring to FIGURES 2 and 3, in a typical exemplary
ethanol
production process, corn can be prepared for further treatment in a
preparation system. As
seen in FIGURE 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.
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[00481 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
[0049] 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.
[00501 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 C16 palmitic, C18 stearic, C18.1 oleic, C18_2 linoleic,
and C18.3 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.
[00511 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
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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.
[0052] 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+), sodium (Na+), magnesium (Mg2+), potassium (K)
and/or
calcium (Ca2+).
[0053] 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.
[0054] 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).
[0055] 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
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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.
[0056] 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 g/g. Such components are known
antioxidants
and can thus provide an oxidative stability to the unrefined corn oil
composition.
[0057] 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 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 I
part per million.
Methods
[0058] 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:
b) adjusting the pH of the corn fermentation residue to provide a corn oil
layer and an
aqueous layer; and
c) separating the corn oil layer from the aqueous layer to provide the corn
oil composition.
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[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:
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.
[0060] 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 (FIGURE 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.
[0061] 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
CA 02715072 2010-09-22
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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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
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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.
[0066] 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.
[0067] 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.
[0068] Once the emulsion has sufficiently broken, a corn oil layer and a
second aqueous
layer are provided (FIGURES 5A and 5B). The corn oil layer comprises the
unrefined corn
oil as disclosed herein.
[0069] 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.
12
CA 02715072 2010-09-22
[0070] 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 (FIGURES
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.
[0071] 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
[0072] A shown in FIGURE 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
13
CA 02715072 2010-09-22
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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
[0077] 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
[0078] The pH level capable of providing an oil composition containing a low
level of
free fatty acid was determined (FIGURE 7). First, an oil fraction in the form
of an emulsion
14
CA 02715072 2010-09-22
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.
[0079] 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 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 I
Free Fatty Acids (percent) 4.8 3.5 3.1 2.2 2.0 1.8
Experiment 2
Example 2
[0080] Experiments were conducted to determine the amount of free oil present
upon
adjustment of the oil fraction to various pH levels (FIGURE 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.
[0081] 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 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
CA 02715072 2010-09-22
Example 3
[0082] 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 (FIGURES 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.
[0083] 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.
[0084] 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 FIGURE 9A), insolubles (see FIGURE 9B), moisture (see
FIGURE
9C), phospholipids (see FIGURE 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.
16
CA 02715072 2010-09-22
TABLE 3
Fat Protein Moisture Other
(percent) (percent) (percent) (percent)***
Starting Material* 5.4 4.1 80 10
First Light Fraction 35 3.6 55 6.8
(Emulsified Oil)*
First Heavy Fraction 3.5 4.2 83 10
(Stickwater)*
Second Light Fraction 98 0.0 0.8 1.6
(Oil Composition)*
Second Heavy Fraction 5.5 5.9 77 11
(Soapstock)*
Low Fat DDGS** 4.0 30 8.7 57
* = Sampled, ** = Projected, ""* = Includes fiber, ash, starch, etc.
Example 4
[0085] 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
US
7,601,858).
[0086] 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
17
CA 02715072 2010-09-22
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.
[0087] 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.
[0088] 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
[0089] 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, NJ).
Oils
[0090] 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,
SD). CG and DDGS were extracted overnight (-20 hr) by Soxhlet extraction using
hexane.
Four parallel Soxhlet extractors with -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
18
CA 02715072 2010-09-22
storage studies. Hexane was removed by rotary evaporation at 40 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
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 C) until used for analyses.
Oil Analysis
Acid Value
[0091] 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
[0092] Oil triacy I glycerol s 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 lc-85 (AOCS, 1998).
Tocopherols, Phytosterols, and Steryl Ferulate Analysis
[0093] 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 at., 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, CA, USA) 6890 GC-MS equipped
with a HP-
5MS capillary column (30 in 9 0.25 mm 9 0.25 Im), a 5973 mass selective
detector, and an
7683 autosampler. The transfer line from GC to the MSD was set to 280 T. 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
19
CA 02715072 2010-09-22
combined with comparison to literature values for relative RT (compared to (3-
sitosterol) and
mass spectra (Beveridge et al., 2002).
Carotenoid Analysis
[0094] Carotenoid analysis and quantitation were conducted by HPLC as
described by
Winkler and Vaughn (2009).
Oxidative Stability Index
[0095] The OSI at 110 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
[0096] 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 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 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
[0097] CS-2 oil was placed into three, 4L 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 C 3 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
CA 02715072 2010-09-22
into a screw cap vial, covered with argon, and frozen (-20 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
10098] 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., 201Ob, 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.
21
CA 02715072 2010-09-22
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
0.0'
FFA (% oleic acid) 3.80 0.03 7.42 0.13 10.1 0.11 2.03 0.05 2.48 0Ø
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
[0099] 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 .tg/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).
22
CA 02715072 2010-09-22
Table 5. Content of tocols and carotenoids, and the oxidative stability index
(OSI) at 110 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
Total Tocopherols ( g/g) 1433.6 1104.2 1056.9 931.3 783
Alpha-tocopherol 213.8 295.6 164.5 160.4 123
Gamma-tocopherol 1185.4 760.8 852.7 742.0 640
Delta-tocopherol 34.3 47.8 39.7 28.8 20
Total Tocotrienols ( g/g) 235.6 1762.3 1419.6 1224.4 1175
Alpha-tocotrienol 21.9 471.9 328.5 243.6 269
Gamma-tocotrienol 165.6 1210.0 1063.6 963.4 8l
Delta-tocotrienol 48.1 80.3 27.5 17.3 25
Total Carotenoids ( g/g) 1.33 75.02 129.48 61.1 85
Lutein 0.37 46.69 75.69 38.13 53
Zeaxanthin 0.4 24.16 45.58 16.78 23
Beta-cryptoxanthin 0.56 3.31 7.35 4.12 5
Beta-carotene NDa 0.86 0.86 2.07 2
OSI (hr) 3.91 6.62 4.45 4.52 5.:
aNot detected
[00100] 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.
[00101] 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
23
CA 02715072 2010-09-22
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 pg/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 ofphytosterols
[00102] 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 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
24
CA 02715072 2010-09-22
mg/g %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 NDb 0 0.30 1.4 ND 0 0.34 1.7 0.30 1.5
cycloartanol
Citrostadienol ND 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)
'The weight percentage of total phytosterols
bNot detected
Oxidative Stability Index (OSI)
[00103] 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-I 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
[00104] 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
CA 02715072 2010-09-22
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 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 C, indicating that it was the most susceptible to oxidation
(Figure 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.
[00105] 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 g/g
hexanal in the oil (Figure 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 pg/g in CG, but leveled
off after day 8.
In CS-I and CS-2, hexanal contents increased to 3 pg/g and 4 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 pg/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.
26
CA 02715072 2010-09-22
Room temperature storage study
[00106] 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
(Figure 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
[00107] 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,
27
CA 02715072 2010-09-22
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.
[00108] 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.
[00109] 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.
28
