Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
ISOLATED EGG PROTEIN AND EGG LIPID MATERIALS,
AND METHODS FOR PRODUCING THE SAME
This application is being filed as a PCT International Patent application on
June 30, 2011, in the name of Rembrandt Enterprises, Inc., a U.S. national
corporation, applicant for the designation of all countries except the U.S.,
and David
Mason, a Canadian Citizen, applicant for the designation of the U.S. only, and
claims
priority to U.S. Provisional Patent Application Serial Number 61/361,197,
filed July
2, 2010; U.S. Patent Application Serial Number 12/910,780, filed October 22,
2010;
and U.S. Provisional Patent Application Serial Number 61/491,163, filed May
27,
2011.
FIELD OF THE INVENTION
The invention described herein relates to processing of eggs and, in
particular,
processes that separate proteins and fats from eggs, as well as materials
produced by
the separation processes.
BACKGROUND OF THE INVENTION
Chicken eggs are one of the most important foods in the human diet, and are
an exceptional source of proteins and fats, as well as amino acids and fatty
acids.
Every year in the United States an estimated 90 billion eggs are produced,
with three
fourths of these eggs being used for human consumption. An estimated 250 eggs
per
person are consumed annually in the United States.
Many of the eggs consumed by humans are eaten as food ingredients, rather
than directly as cooked eggs (such as boiled, fried, poached, etc.). In some
cases
whole eggs are used as food ingredients, for example as baking applications.
However, it is often desirable to use just a portion of an egg as a food
ingredient. For
example, egg yolk is an excellent emulsifier and surfactant, and is an
essential
component of mayonnaise and various other foods. The egg yolk makes up
approximately one third of the liquid weight of an egg, and is high in fats
and fatty
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acids. Important fat soluble vitamins (A, D, E, and K) are found in egg yolk,
as are
unsaturated fatty acids (e.g. oleic acid, linoleic acid, palmitoleic acid, and
linolenic
acid) and saturated fatty acids (e.g. palmitic acid, stearic acid, and
myristic acid). Egg
yolks also contain some proteins, typically on the order of 2 to 3 grams out
of about
15 to 20 grams of yolk within an egg weighing approximately 50 grams.
The egg white, known as well as the albumen, also has unique uses as a result
of having high protein content. Egg whites are used in many products, such as
to
make mousse and to enhance protein content of foods. Egg white is
approximately
two-thirds of the total weight of an egg, with approximately 90 percent of
that weight
coming from water. The remaining weight of the egg white comes primarily from
protein, along with various trace minerals, vitamins, some fats, and glucose.
A typical
large egg may contain 35 to 40 grams of egg white, of which about 4 to 5 grams
are
proteins. The most common protein in egg whites is ovalbumen, which accounts
for
over half of the proteins. Ovotransferrin and ovomucoid are additional primary
proteins, with other proteins including ovoglobulin 62, Ovoglobulin 63,
ovomucin,
lysozyme, ovoinhibitor, ovoglycoprotein, flavoprotein, ovomacroglbulin,
avidin, and
crystatin. The egg white contains no dietary cholesterol, but does contain
small
quantities of other lipids and fats.
Thus, egg yolks are very high in fats, but low in proteins; while egg whites
are
very high in proteins, but low in fats. However, egg yolks do contain some
proteins,
and egg whites do contain small quantities of fats.
Due to their different compositions and uses, it is often desirable to
separate
egg yolks and egg whites from one another. Various systems and methods have
been
developed for separation of eggs into yolks and whites. Separation of yolk and
white
from whole eggs can be done at high speeds under automated conditions, and can
very effectively separate the yolks and eggs, with relatively little mixing of
the yolk
and eggs.
Despite the uses of existing technology to separate yolks from whites, a need
exists for further separation of egg components, including components in both
the egg
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yolk and the egg white. This is true because the mere physical separation of
the egg
yolk from the egg white is not always sufficient to maximize use of the yolks
and
whites. For example, with regard to the yolk, it can desirable to also remove
the yolk
proteins from the yolk fats for at least two reasons: First, traditional uses
of the yolk
as an emulsifier improve upon reduction of the protein content. Second, the
removal
of the protein provides an isolated protein material that has further uses for
applications where high-protein materials are desired and where the specific
yolk
proteins are desired in isolated form. Similarly, with regard to the egg
white, removal
of non-protein materials creates a higher quality isolated protein. Also,
separation of
the proteins into different sizes and types can have significant benefits for
production
of specialized products.
In addition to the benefits associated with separating proteins and fats from
nearly pure egg yolks and pure egg whites, a need also exists for separation
of
proteins and fats from mixtures that contain both egg yolks and egg whites.
Such
mixtures are created, for example, as a result of incidental breakage of yolks
during
the separation of the yolk from the white during the cracking process.
Similarly,
some egg white can remain with the egg yolk during cracking. These mixtures
result
in increased levels of proteins in the separated egg yolk, and increased
levels of fats in
the separated egg whites. The ability to separate the primary constituents
(proteins
and fats) within the mixtures can have meaningful advantages in terms of
nutritional
value and performance for specific applications (such as to create
mayonnaise).
Yet another scenario for separation of fats and proteins in eggs arises due to
production of eggs at hatcheries (or other facilities) where the eggs are not
primarily
raised for human consumption. For example, sterile eggs and non-incubated eggs
from hatcheries are not produced or used for human consumption. Although these
hatchery-derived eggs are typically not provided for regular human
consumption, they
are still of value as a source of fats and proteins. Currently the hatchery-
derived eggs
are not processed so as to be separated into yolk and white components,
because they
are produced in facilities that are not served by a high speed cracker and
separator.
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Instead, the hatchery-derived eggs are often broken and run through a
separator to
remove the egg shells, a process that mixes the egg yolks and proteins. This
mixed
egg yolk and white, which is considered inedible for human consumption, is
typically
used as a combined additive for uses such as animal feed. However, a need
exists for
a means for effectively separating the fats and proteins from these mixtures
of
inedible eggs so as to gain the maximum benefit of the proteins and fats,
which is best
achieved by separating them from one another
As noted above, the most prevalent means of separating egg components is
limited to the separation of whole yolks and whites from one another. This
separation
is commonly performed at high speeds and efficiencies using automatic
equipment.
However, alternative efforts for further separation of egg components into
more
isolated components have been attempted. Unfortunately, these methods have
proven
problematic for various reasons, including because the processes are
inefficient,
impractical, or have other deficiencies.
An example of such efforts is found in U.S. patent application Serial No.
11/971,802 ("the '802 application"), assigned to Biova, Inc., and which is
directed to
a method of separating lipids from an egg mixture by using a cross-linking
reagent.
The cross-linking reagent is added to an egg mixture containing lipids and
solubilized
proteins, causing the lipids to crosslink so they can be separated from the
proteins.
Suitable crosslinking reagents include cyclobetadextran, silicon dioxide,
colloidal
silica material, fumed silica materials, and synthetic calcium silicate
hydrates. The
method of the '802 application may can include adjusting the pH level of the
egg
mixture to a pH at which the cross-linking reagent is functional so that cross-
linking
of the lipids occurs. The proteins are subsequently separated from the cross-
linked
lipids to provide a separated protein. The separated proteins may be obtained
by
subjecting the egg mixture to one or membranes or filters of various sizes to
separate
or further isolate proteins or populations of proteins of interest.
Although it may be possible to separate proteins and fats derived from eggs
using the teachings of the '802 application, significant drawbacks are
associated with
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the methods and materials it discloses. First, the inclusion of the cross-
linking reagent
is problematic if the egg components will eventually be consumed by humans, in
that
there is often opposition on the part of the public and regulatory agencies to
consume
materials that have been subject to adulteration by organic reagents, such as
cyclobetadextran, or by inorganic materials such as colloidal or fumed silica
materials. The aversion to the use of these cross-linking reagents exists, in
part,
because of the potential for undesirable modification or contamination of the
crosslinked ingredients. Although naturally occurring silica is widespread in
nature,
its use in food processing is unusual, and risks opposition by consumers even
if little
or none of the crosslinking agent remains in the separated components.
Second, the use of the crosslinking reagent necessarily adds expense to the
processing of the egg mixture, both because of the cost of the crosslinking
reagent
itself, as well as the costs associated with the additional steps of
crosslinking the fats
and subsequent removal of the crosslinking agent (such as silica) from the
fats after
separation of the fats and proteins, assuming the fats are intended for
further use.
Thus, not only does the use of a reagent result in potentially problematic
alteration
and/or contamination of the egg material with crosslinker, especially the egg
yolk
(since it is the fats that are crosslinked, and fats are primarily found in
the yolk), but
the use of the reagent adds expense and complexity to the egg processing
methods: A
step must be made to add the reagent to the egg mixture, one to induce
crosslinking of
the fats, as well as steps to reverse the crosslinking, when possible, after
separation of
the crosslinked egg fats and egg proteins. These steps all take time,
equipment, and
effort.
Yet another problem with the methods taught in the '802 application is that
the
use of the reagents creates an issue with regard to waste silica (or other
crosslinking
agent), which must be removed from the fats for most uses of the fats, and
which can
result in creation of an undesirable waste stream that must be disposed of,
even if it is
not hazardous. Today there is an increased emphasis on processes that use
limited
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resources and which produce little or no waste product, and the '802
application does
not fully satisfy this objective.
Therefore, a need exists for methods and equipment for separating egg
components into proteins and fats (or other substituents, such as amino
acids). Such
methods and equipment should include the ability to separate the components of
exclusively egg yolk materials, exclusively egg white materials, and mixtures
of
various levels of egg yolk and egg white. Preferably such methods and
equipment
can be efficient, cost effective, produced without undesirable alteration of
the egg
components (such as alteration with cross linkers), and do not create
excessive
undesirable waste streams.
SUMMARY OF THE INVENTION
The invention described herein provides a method for separating fats and
proteins from an egg mixture that includes both egg yolk and egg whites, as
well as
separation of components from pure egg white and separation of components from
pure egg yolks. The methods and systems of the present invention allow the
ready
separation of the ingredients of an egg, regardless of whether the separation
is
occurring on just a portion of an egg (such as the yolk or the white), or a
mixture of
egg yolks and egg whites.
Significantly, the present invention does not require alteration of either the
fats
or the proteins with a reagent or manipulation of pH. Thus, the present
invention
allows the integrity of the egg ingredients to be maintained so as to avoid
undesirable
alteration, such as incorporation of a crosslinker. As such the present
invention also
avoids extra production steps and does not produce a new waste stream
associated
with use of a crosslinking reagent.
The method comprises obtaining an egg mixture containing egg-derived lipids
and egg-derived proteins; and micro filtration of the egg mixture to obtain a
isolated
protein composition. An example implementation of the present invention
comprises
obtaining an egg mixture contaiing egg yolk lipids, egg yolk proteins, and egg
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albumen; and microfiltration of the egg mixture to obtain a isolated protein
composition containing yolk-derived proteins and albumen-derived proteins.
As will be more specifically described below, the microfiltration occurs under
conditions whereby the selection of the filter materials, as well as the
filter
configuration, provide improved separation of egg components while avoiding
fouling
of the filter materials.
In one embodiment, the filter incorporates hollow fiber membranes
constructed from a hydrophilic material. In example embodiments, the hollow
fiber
membrane is constructed from polysulfone (PS) or polyether sulfone (PES). In
an
alternative embodiment, hollow fiber ceramic material is used.
In an alternative embodiment, a spiral wound membrane module is used. The
membranes forming the spiral wound membrane module may be, for example, formed
of polyvinylidene fluoride (PVDF). Preferably the spiral wound membrane
modules
include spacers between membrane layers. Suitable spacing is generally greater
the
30 mils, more generally greater than 45 mils, and in some implementations
greater
than 60 mils.
In a specific implementation, a method for separating proteins and lipids from
an egg mixture is described, and the method comprises obtaining an egg mixture
containing egg yolk lipids and egg yolk proteins; and microfiltration of the
egg
mixture to separate the egg yolk lipids from the egg yolk proteins. The method
for
separating proteins from an egg mixture can include the steps of obtaining an
egg
mixture comprising egg yolk and egg albumen; maintaining the pH of the egg
yolk
and egg albumen within the natural range of egg pH; and microfiltration of the
egg
mixture to obtain a isolated protein composition containing yolk-derived
proteins and
albumen-derived proteins. In this manner superior protein recovery is obtained
over
prior art methods, because both yolk-derived proteins and albumen-derived
proteins
are isolated and obtained. Simultaneously, the remaining egg yolk is improved
by
removal of the proteins, which do not generally have primary functional
benefits for
the applications where yolk fats are desired (such as emulsifiers).
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In certain implementations the method comprises obtaining an egg mixture
comprising egg yolk and egg albumen and maintaining the lipids in a
substantially un-
crosslinked form. The mixture is microfiltered to obtain a isolated protein
composition containing yolk-derived proteins and albumen-derived proteins. The
egg
mixture initially comprises between about 40%-70 % protein by weight and
between
about 15%-45 % fat. Variations in the protein and fat compositions occur
depending
upon the source of the egg materials: Sources that are high in egg whites,
such as
from spinning of egg shells, will be high in protein; while those that have
more yolk
based material, such as whole eggs from hatcheries, will have relatively
higher fat
levels and relatively lower protein levels.
The invention is further directed to an egg powder obtained from egg yolks
and/or egg albumen. In an example embodiment the egg powder comprises at least
about 60% by dry weight protein; and less than about 2% by dry weight fat;
wherein
at least a portion of the protein is derived by filtration of a mixture of egg
yolk lipids
and egg yolk proteins.
A high gel strength egg powder can further be created, the egg powder
comprising at least about 60% by weight protein; no more than about 1% by
weight
fat; and a gel strength of at least 400, wherein at least a portion of the
protein is
derived by filtration of a mixture of egg yolk lipids and egg yolk proteins.
In some
implementations higher levels of protein are present, including at least 70%
by weight
protein, at least 75% by weight protein, at least 80% by weight protein, at
least 85%
by weight protein, or at least 90% by weight protein. Also, it is possible to
have very
low weight percents of fat in some implementations, including less than 0.5%
by
weight fat in some implementations.
The methods and apparatus of the present invention can be used for separating
components of both edible and inedible eggs, where inedible eggs include (for
example) hatchery eggs that are not fertilized or not incubated.
As discussed above, the method of the invention includes a step of
microfiltration of the egg mixture, wherein the microfiltration step includes
pumping
8
the egg mixture across a filter, optionally a hollow fiber filter. The hollow
fiber filter
will generally have a pore size of less than 0.20 microns, and more generally
less than
0.10 microns. The pore size of the filter is typically greater than 0.02
microns.
Suitable pore sizes for the filter include approximately 0.05 microns, as well
as 0.04
to 0.08 microns.
The egg mixture is generally processed in the filter at low pressures. In one
implementation the egg mixture is processed at a pressure of less than about
30 PSI.
Optionally the pressure can be less than 20 PSI in some implementations.
Higher PSI
can be used, but can result in premature fouling of the filter membrane and
also result
in rupturing the membrane in some situations. Thus, pressures of less than 40
PSI,
less than 50 PSI, and less than 100 PSI are useful in some implementations,
but
generally lower pressures are desired. A pressure range of 10 to 30 PSI can be
particularly useful.
The flux rate is typically in a range of about 40 to 80 milliliters per minute
per
square foot of membrane, with the permeate being (for example) from 3 to 5
percent
solids when the incoming material is about 10 percent solids.
The invention also provides egg powder a high gel strength egg powder,
wherein the egg powder includes less than neg/25g salmonella; at least about
65% by
dry weight protein; and no more than about 1% by dry weight fat. The egg
powders
can be produced from edible or inedible eggs. Higher protein levels can be
obtained,
including levels of 70 to 85 % by dry weight protein. The egg powder can have
a
high gel strength that is greater than 300 grams per square centimeter, more
commonly greater than 400 grams per square centimeter, and desirably 500 or
more
grams per square centimeter.
In accordance with an aspect, there is provided a method for separating
proteins from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg-derived lipids and egg-derived
proteins; and
(b) microfiltration of the egg mixture to obtain an isolated protein
composition;
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wherein no egg-lipid cross-linker is added to the egg mixture and the
microfiltration
comprises pumping the egg mixture across a membrane with a pore size of less
than
0.40 microns at a pressure of less than 60 psi.
In accordance with an aspect, there is provided a method for separating
proteins from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg yolk lipids, egg yolk proteins,
and
egg albumen; and
(b) microfiltration of the egg mixture comprising egg yolk lipids, egg yolk
proteins, and egg albumen to obtain an isolated protein composition containing
yolk-
derived proteins and albumen-derived proteins:
wherein no egg-lipid cross-linker is added to the egg mixture and wherein the
microfiltration comprises pumping the egg mixture across a membrane with a
pore
size of less than 0.5 microns at a pressure of less than 60 psi.
In accordance with an aspect, there is provided a method for separating
.. proteins and lipids from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg yolk lipids and egg yolk
proteins;
and
(b) microfiltration of the egg mixture to separate the egg yolk lipids from
the egg
yolk proteins,
wherein no egg-lipid cross-linker is added to the egg mixture and wherein the
microfiltration comprises pumping the egg mixture across a membrane with a
pore
size of less than 0.5 microns at a pressure of less than 60 psi.
In accordance with an aspect, there is provided a method for separating
proteins from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg yolk and egg albumen;
(b) maintaining the pH of the egg yolk and egg albumen within a range of
about 4
to about 8; and
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(c) microfiltration of the egg mixture comprising egg yolk lipids, egg yolk
proteins, and egg albumen to obtain an isolated protein composition containing
yolk-
derived proteins and albumen-derived proteins;
wherein no egg-lipid cross-linker is added to the egg mixture and wherein the
microfiltration comprises pumping the egg mixture across a hollow fiber filter
with a
pore size of less than 0.20 microns.
In accordance with an aspect, there is provided a method for separating
proteins from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg yolk and egg albumen; and
(b) microfiltration of the egg mixture comprising egg yolk lipids, egg yolk
proteins, and egg albumen to obtain an isolated protein composition containing
yolk-
derived proteins and albumen-derived proteins, wherein no egg-lipid cross-
linker is
added to the egg mixture.
In accordance with an aspect, there is provided a method for separating
proteins from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg-derived lipids and egg-derived
proteins; and
(b) microfiltration of the egg mixture to obtain an isolated protein
composition
wherein no egg-lipid cross-linker is added to the egg mixture and wherein the
microfiltration comprises pumping the egg mixture across a hollow fiber filter
with a
pore size of less than 0.20 microns.
In accordance with an aspect, there is provided a method for separating
proteins from an egg mixture, the method comprising:
(a) obtaining an egg mixture comprising egg yolk lipids, egg yolk proteins,
and
egg albumen; and
(b) microfiltration of the egg mixture comprising egg yolk lipids, egg yolk
proteins, and egg albumen to obtain an isolated protein composition containing
yolk-
derived proteins and albumen-derived proteins;
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wherein no egg-lipid cross-linker is added to the egg mixture and wherein the
microfiltration comprises pumping the egg mixture across a hollow fiber filter
with a
pore size of less than 0.20 microns.
This summary is an overview of some of the teachings of the present
application and is not intended to be an exclusive or exhaustive treatment of
the
present subject matter. Further details are found in the detailed
specification. Other
aspects will be apparent to persons skilled in the art upon reading and
understanding
the following detailed description and viewing the
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drawings that form a part thereof, each of which is not to be taken in a
limiting sense.
The scope of the present invention is defined by the appended claims and their
legal
equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be understood by review of the following drawings:
FIG. I is a flow chart of an egg separation process described herein,
constructed and arranged in accordance with an implementation of the
invention.
HG. 2 is a schematic of an egg separation process described herein for an egg
breaking operation, such as with eggs from a hatchery, constructed and
arranged in
accordance with an implementation of the invention.
While the invention is susceptible to various modifications and alternative
forms, specifics thereof have been shown by way of example and drawings, and
will
be described in detail. It should be understood, however, that the invention
is not
limited to the particular embodiments described. On the contrary, the
intention is to
cover modifications, equivalents, and alternatives falling within the spirit
and scope of
the invention.
DETAILED DESCRIPTION
Whole egg components generally include an eggshell, two eggshell
membranes, and an egg white and an egg yolk. The egg white makes up about two-
thirds of the liquid weight of the egg, with the egg yolk making up
approximately the
remaining one-third. Both the egg white and the egg yolk contain nutritionally
valuable components such as proteins and fats (also called lipids). The
different egg
components impart various "functional properties" to the egg. The term
"functional
properties" refers to the properties of eggs including, but not limited to,
coagulation,
foaming, emulsifying, and nutritional contribution.
The main components of the egg white (the albumen) include water (approx.
90% by weight) and solids (approx. 10% by weight) such as proteins, trace
minerals,
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fatty material (less than 0.4 %), vitamins and glucose, with protein making up
the
majority of the solids. In fact, the egg white contains approximately 40
different
proteins. The predominant proteins in albumen include: Ovalbumen,
Ovotransferrin,
Ovomucoid, Globulins, Lysozyme, Ovomucin, and Avidin.
The egg yolk includes protein, fat, water, vitamins, minerals and other trace
elements. As used herein, the term "fat" refers to lipids. The most prevalent
lipids in
egg yolk include: unsaturated fatty acids (Oleic acid, Linoleic acid,
Palmitoleic acid,
and Linolenie acid) and saturated fatty acids (Palmitie acid, Stearie acid,
and Myristic
acid). The yolk is also a source of lecithin, a common emulsifier, and
proteins,
including but not limited to immunoglobulins such as IgY and/or ovatransferin.
Each of the various egg components has utility in a variety of industries.
However, even though it is recognized that eggs contain numerous valuable
components, problems remain with respect to recovery and/or separation of such
components in efficient and cost-effective ways.
Commercially produced chicken eggs for human consumption often originate
in egg laying operations where non-fertile eggs are produced and collected.
After
being collected, transferred to a processing facility and washed, the eggs are
graded as
either edible or inedible. Eggs that have met an edible grade category are
then graded
AA, A or B. Eggs that are labeled inedible are not suitable for human
consumption
based on the USDA or other government regulations. About 98% to 99% of eggs
meet a grade category of AA, A or B. The remaining 1% or 2% are considered
inedible (i.e., not suitable for human consumption). The primary reason an egg
is
considered inedible is that the egg is malformed or contains discrete blood
spots.
Otherwise, the product is generally safe for human consumption.
After the eggs are initially graded as edible or inedible, the eggshell of the
edible eggs can be broken using an egg breaking machine. The whole egg (egg
yolk
and egg white) mixture is then strained to separate the egg yolk from the egg
white
(the yolk is retained while the white passes through the strainer). Once the
yolk is
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separated from the egg white, additional processing of the egg white and/or
the yolk
often occurs.
The broken shells from the edible eggs are typically spun via a centrifuge
system to extract the egg white that remains adhered to the broken eggshells.
The
extracted egg white is also considered inedible (e.g., not usable for human
consumption). The broken eggshells can be dried and ground up to be used as an
ingredient in animal feeds and other products, among other uses.
Another source of eggs comes from hatcheries intended to produce chicks.
Some of the eggs from hatcheries do not hatch, often because they are
infertile, are
not incubated, or are not incubated to full development. These eggs often are
handled
as inedible eggs ¨ either by choice (such as in eggs that are not incubated)
or due to
regulatory requirements (such as, for example, eggs that are not incubated to
full
development). Hatchery eggs are typically processed without separation of the
yolk
and white in a process whereby they are cracked and processed as a combination
of
yolk and whites.
Thus, three major sources of inedible egg products exist: eggs that were
produced to be edible but are graded as inedible, egg components that are
collected
from egg shells, and eggs that originated from hatcheries. Other sources also
exist,
such as eggs that are returned from food processors (such as due to passing
freshness
dates), eggs that missed the pan during cracking operations, or otherwise
deemed to
be technical (or inedible) eggs by the USDA or other regulators. These
inedible eggs
and mixtures of egg components are frequently used in animal food products.
Examples of animal food products include but are not limited to "wet" pet
foods such
as canned dog and cat food, dry pet foods, and weanling pig feed. Although
these
uses of inedible egg mixtures are desirable, the present products arc
relatively low
value because they are not modified or processed in a manner that optimizes
uses and
performance. Therefore, a need exists for improved processing of inedible egg
mixtures. This improved processing also has the potential for improved
processing of
edible egg mixtures.
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Significantly, the present invention does not require alteration of either the
fats
or the proteins with a reagent or manipulation of pH. Thus, the present
invention
allows the integrity of the egg ingredients to be maintained so as to avoid
undesirable
alteration, such as incorporation of a crosslinker. As such the present
invention also
avoids extra production steps and does not produce a new waste stream
associated
with use of a crosslinking reagent
The method comprises obtaining an egg mixture comprising egg-derived
lipids and egg-derived proteins; and microfiltration of the egg mixture to
obtain an
isolated protein composition. An example implementation of the present
invention
comprises obtaining an egg mixture comprising egg yolk lipids, egg yolk
proteins,
and egg albumen; and microfiltration of the egg mixture comprising egg yolk
lipids,
egg yolk proteins, and egg albumen to obtain a isolated protein composition
containing yolk-derived proteins and albumen-derived proteins.
As will be more specifically described below, the microfiltration occurs under
conditions whereby the selection of the filter materials, as well as the
filter
configuration, provide improved separation of egg components while avoiding
fouling
of the filter materials. In one embodiment, the filter incorporates hollow
fiber
membranes constructed from a hydrophilic material. In example embodiments, the
hollow fiber membrane is constructed from polysulfone (PS) or polyether
sulfone
(PES). In an alternative embodiment, a spiral wound membrane module is used.
The
membranes forming the spiral wound membrane module may, for example, be formed
of polyvinylidene fluoride (PVDF). Preferably the spiral wound membrane
modules
include spacers between membrane layers. Suitable spacing is generally greater
the
30 mils, more generally greater than 45 mils, and in some implementations
greater
than 60 mils.
The membrane module, however configured, should primarily allow proteins
to pass, while avoiding passing of larger lipids. Specifically, the membrane
should be
selected so as to substantially restrict the passage of lipids from the egg
mixture,
while allowing the passage of proteins from the egg mixture. Generally, the
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membrane should have pore sizes of less than 0.5 microns, more typically less
than
0.4 microns, and usually less than 0.3 microns. It will be understood that in
some
implementations the pore size will be less 0.2 microns. Optionally, the pore
size is
less than 0.1 microns. Pore size ranges of 0.1 to 0.2 microns are desirable in
some
implementations, as are pore sizes of 0.05 to 0.3 microns in some
implementations.
In some implementations, the PVDF is selected to have a nominal cutoff of
800,000 dalton, in other implementations the PVDF is selected to have a
nominal
cutoff of greater than 700,000 dalton, greater than 600,000 dalton, or greater
than
500,000 dalton. In other implementations the PVDF is selected so as to have a
nominal cutoff of greater than 800,000 dalton, greater than 900,000 dalton, or
greater
than 1,000,000 dalton. The PVDF can be selected so as to have a nominal cutoff
of
less than 900,000 dalton, less than 800,000 dalton, less than 700,000 dalton,
less than
600,000 dalton, and less than 500,000 dalton. Typically the PVDF will have a
nominal cutoff of from 600,000 to 1,000,000 dalton, or from 700,000 to 900,000
dalton.
Suitable membranes include ultra filration membranes produced by Snyder
Fitlration, located in Vacaville, California, including 0.2 and 0.1 micron
PVDF filters.
The invention described herein provides a method for processing an egg
mixture that contains egg yolk and egg albumen, or just egg yolk or egg
albumen, to
separate proteins and fats. As used herein the term protein refers to organic
compounds made of amino acids (polypeptides) and includes, but is not limited
to,
proteins such as immunoglobulins, for example, IgY. As used herein, the term
"fats"
can be used interchangeably with "lipids" and refers to water-insoluble
components
such as fatty acids, steroids, such as cholesterol, glycolipids, lipoproteins
and
phospholipids.
In one embodiment, the invention relates to processing of an edible or
inedible
egg mixture. In a more particular embodiment, the invention provides a method
of
processing an edible or inedible egg mixture to obtain an egg protein powder
(which
will be edible or inedible based upon whether the source eggs were edible or
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inedible). In a specific embodiment, the egg mixture comprises between about
40%-
70 % protein by weight and between about 15%-45 % fat. Typically this mixture
will
have the fat and protein intermixed to some degree, but the mixture is not
actually
homogenized. Indeed, it is generally desirable to maintain some separation of
the
components of the egg yolk and egg whites, and therefore lower levels of
mixing can
be desirable. Although homogenized egg products are often less desirable for
use
with the present invention, it is possible to use egg compositions that
include some
homogenized egg materials. For example, homogenized eggs that were originally
edible, but have expired due to prolonged shelf life, can be considered to be
inedible
and processed using the methods and apparatus of the invention.
The method includes a step of microfiltration of the egg mixture, wherein the
microfiltration step includes pumping the egg mixture across a filter,
optionally a
hollow fiber filter. The hollow fiber filter will generally have a pore size
of less than
0.20 microns, and more generally less than 0.10 microns. The pore size of the
filter is
typically greater than 0.02 microns. Suitable pore sizes for the filter
include
approximately 0.05 microns, as well as 0.04 to 0.08 microns.
The egg mixture is generally processed in the filter 60 at low pressures. In
one
implementation the egg mixture is processed at a pressure of less than about
30 PSI.
Optionally the pressure can be less than 20 PSI in some implementations.
Higher
pressures can be used, but can result in premature fouling of the filter
membrane.
Thus, pressures of less than 40 PSI, less than 50 PSI, and less than 100 PSI
are useful
in some implementations, but generally lower pressures are desired.
As noted above, in some implementations the egg mixture is processed using a
PVDF spiral wound membrane filter. In such implementations, multiple filter
modules may be used. In some example implementations the egg mixture is
processed at a pressure of approximately 10 psi baseline pressure plus 10 to
15 psi for
each membrane module in series in the system (often about 13 psi for each
membrane). For example, a system with two membrane modules might have an inlet
pressure of 36 psi and an outlet pressure of 10 psi.
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When using a hollow fiber membrane, the flux rate is desirably in a range of
about 40 to 80 milliliters per minute per square foot, with the permeate being
from 3
to 5 percent solids when the incoming material is about 10 percent solids. In
one
embodiment, the filter incorporates hollow fiber membranes constructed from a
hydrophilic material. The hollow fiber membrane can be constructed from, for
example, polysulfone (PS) or polyether sulfone (PES). In an alternative
embodiment,
a spiral wound membrane module is used, and has a flux rate of greater than 4
liters
per hour per square media of membrane. Preferably even higher fluxes are
achieved,
such as greater than 6 liters per hour per square meter of membrane. The
membranes
forming the spiral wound membrane mosule may be, for example, be formed of
polyvinylidene fluoride (PVDF). Preferrably the spiral wound membrane modules
include spacers between membrane layers. Suitable spacing is generally greater
the
30 mils, more generally greater than 45 mils, and in some implementations
greater
than 60 mils.
Spiral wound modules can be susceptible to fouling, and therefore it is often
desirable to design and operate a system utilizing clean in place (CIP)
processes, so
that the membranes can be cleaned without shutting down the entire system or
stopping the separation process. Such cleaning often occurs more than once per
24
hour period, in some implementations less than every 16 hours, and in certain
implementations approximately every 8 hours.
The invention also provides a non-food grade egg powder obtained from
inedible egg and a high gel strength inedible egg powder, wherein the egg
powder
includes less than neg/25g salmonella; at least about 65% by weight protein;
and no
more than about 1% by weight fat. The high gel strength inedible egg powder
can
have a high gel strength that is greater than 300 grams per square centimeter,
more
commonly greater than 400 grams per square centimeter, and desirably 500 or
more
grams per square centimeter.
Referring now to the drawings, Figure 1 depicts an example flow diagram of
an egg processing method. Eggs 20 are collected from egg barns (not shown).
The
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eggs 20 are separated into edible 22 and inedible 24 eggs. The edible eggs 22
are then
broken and the edible albumen 26 and the edible yolk 28 are transported for
further
processing for human consumption. Dried edible albumen 26 contains no yolk
protein and approximately 0.4% by weight fat. The edible yolk 28 contains
about
30% by weight protein and approximately 60 % by weight fat.
The eggshells 30 with residual albumen adhered thereto are sent down a
separate processing line where they are then centrifuged, separating the
shells 32 from
the residual albumen, which is now classified as inedible albumen 34.
The inedible eggs 24 are also broken and the shells 36 processed. The white
and yolk 38 from the inedible eggs 24 are mixed with the inedible albumen 34
extracted from the shells to form an inedible egg mixture 40. The inedible egg
mixture 40 is an uncooked and unprocessed liquid mixture containing both egg
yolk
(including yolk fat and proteins), along with the egg white (and associated
proteins).
The inedible egg mixture generally includes between about 40%-70% by dry
weight
protein and between about 40%-15% by dry weight fat.
Typically, the inedible egg mixture 40 is maintained at a temperature of less
than approximately 50 F and a pH above approximately 5.75 to 7.00, or
optionally
from about 4.0 to 8Ø Frequently caramel coloring is added into the egg
mixture 40
to identify the mixture as inedible. As such, the vessel 43 in which the
inedible egg
mixture 40 is maintained may include an agitator or paddle to mix the liquid
egg
mixture.
Figure 2 provides a schematic of a process for separating proteins and fats
from an egg mixture according to the invention from an example breaking
operation
(such as from hatchery eggs that were not incubated). According to the process
shown in Figure 2, the eggs 50 arc first broken and the liquid egg (i.e., egg
yolk and
egg whites) are removed. As noted above, the eggs are typically inedible eggs,
but
optionally can be edible eggs. The shells with residual egg adhered thereto
are
transported to a shell centrifuge 52 where centrifugal force is used to
separate the
residual liquid egg from the shell particulate matter. The processed shell
particulate
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matter can then be collected, processed and sold, for example, for use as a
calcium
supplement. The extracted residual egg liquid can be drained into a collecting
vat and
sold, for example, as animal food, stored, or subject to further processing.
In one embodiment, the liquid egg is removed from the shell centrifuge and
run through a hydrocylcone 54 to remove suspended calcium. The liquid egg
material
is collected in a tank 56. A pump, for example, a centrifugal pump 58 can be
used to
pump the liquid egg material through a microfiltration membrane 60.
The method further includes a step of microfiltration of the egg mixture,
wherein the microfiltration step includes pumping the egg mixture across a
filter,
optionally a hollow fiber filter. The combination of pressure, flux (i.e., the
tangential
flow of the liquid across the surface of the membrane) and membrane pore size
can
significantly impact filter performance. The hollow fiber filter will
generally have a
pore size of less than 0.20 microns, and more generally less than 0.10
microns. The
pore size of the filter is typically greater than 0.02 microns. Suitable pore
sizes for the
filter include approximately 0.05 microns, as well as 0.04 to 0.08 microns.
The egg mixture is generally processed at low pressures. In one
implementation the egg mixture is processed at a pressure of less than about
30 PSI.
Optionally the pressure can be less than 20 PSI in some implementations.
Higher PSI
can be used, but can result in premature fouling of the filter membrane. Thus,
pressures of less than 40 PSI, less than 50 PSI, and less than 100 PSI are
useful in
some implementations. The flux rate is desirably in a range of about 40 to 80
milliliters per minute per square foot of filter membrane, with the permeate
being
from 3 to 5 percent solids when the incoming material is about 10 percent
solids.
As noted above, in some implementations the egg mixture is processed using a
PVDF spiral wound membrane filter. In such implementations, multiple filter
modules may be used (although single membrane modules are used in some
implementations). In some example implementations the egg mixture is processed
at
a pressure of approximately 10 psi baseline pressure plus 10 to 15 psi for
each
membrane module in series in the system (often about 13 psi for each
membrane).
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For example, a system with two membrane modules might have an inlet pressure
of
36 psi and an outlet pressure of 10 psi.
The egg mixture may be processed at various temperatures, with 65 to 70
degrees Fahrenheit being desirable, as well as 60 to 75 degrees Fahrenheit. In
the
alternative, other temperature ranges may be used.
It is believed that the relatively low pressure reduce the amount of fat that
is
forced into the pores of the filter membrane. When the low pressure is
combined with
a relatively high tangential velocity of fluid across the surface of the
membrane, the
fat (retentate) is forced to flow past the membrane while allowing the protein
(the
permeate) to pass through the membrane pores. As such, the amount of fat
deposited
on the filter is significantly reduced and performance is enhanced. To further
reduce
the amount of fat deposited on and fouling the membrane, the hollow fiber
membrane
can be constructed using a hydrophilic material such as polysulfone (PS) or
polyester
sulfone (PES). Polyvinylidine fluoride (PVDF) is another suitable material for
use in
the processes of the present invention, and are typically formed into spiral
wound
membrane modules.
The liquid permeate that contains the protein can be collected in a second
batch tank 62 and the retentate, which includes the fat, residual proteins and
other
solids such as bacteria, can optionally be returned to the first batch tank.
If desired,
water can be added to the first batch tank 56 and the retentate liquid can be
again
pumped through the hollow fiber filter membrane 60 to increase yield. This
process
can be repeated until about 95 % of the protein has been recovered (i.e., has
permeated the filter) in some implementations, and up to about 85 percent in
other
implementations. This recovery rate, also referred to as yield, is generally
greater
than 60 percent. If desired, phospholipids such as phosphotidyl choline can
also be
separately extracted from the fat containing retentate.
The liquid protein solution (permeate) from the second batch tank 62 can be
further isolated, for example by pumping the liquid permeate through a
nanofilter 64
using a high pressure pump 66. In one embodiment, the protein solution is
isolated to
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a solution containing approximately 20%-35% by weight solids. A isolated
protein
solution is desirable because drying time, and hence cost, can be reduced.
Additionally, the nanofiltration step can also reduce the amount of ash
present in the
final isolated protein solution. In one embodiment, a spiral wound nanofilter
is used
to concentrate the protein solution. If desired, functional proteins such as
lysozyme or
immunoglobulins, such as IgY, can be separated from the liquid protein
solution prior
to nanofiltration. When nanofiltration is completed, the pH of the isolated
protein
solution can be adjusted and yeast added to convert sugars present in the
solution to
carbon dioxide. Next, the isolated protein solution is dried using a spray
dryer 68.
In one embodiment, the process of the invention is used to provide an egg
protein powder containing proteins that are derived from the egg yolk and the
egg
white. In another embodiment, the egg protein powder can be dissolved in water
and
cooked to form a gel that binds the water in which the powder was dissolved.
For
example, the powder can be packaged or placed in a hot humid room with a
temperature from 165 F to 175 F and humidty of 30 to 40 percent for multiple
days
(generally 10 to 20 days) to denature the protein and increase gel strength.
Protein powders with the following gel strength can be obtained by the process
described herein, and are compared to standard whole egg powder (48% protein
by
weight) which has a 150 gel strength:
(a) 65% protein by dry weight egg powder (higher egg white content ¨
200 gel strength ¨ comparable product to US wheat gluten)
(b) 80% by dry weight standard egg white powder ¨ not hot room treated ¨
250 gel strength
(c) standard edible egg white powder ¨ hot roomed for gel ¨ 400 gel
strength
(d) high gel strength inedible egg powder ¨ hot roomed for gel -500/550
gel strength.
The invention is further directed to an egg powder obtained from egg yolks
and/or egg albumen. In an example embodiment the egg powder comprises at least
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about 60% by dry weight protein; and less than about 2% by dry weight fat;
wherein
at least a portion of the protein is derived by filtration of a mixture of egg
yolk lipids
and egg yolk proteins.
A high gel strength egg powder can be created wherein the egg powder
comprising at least about 60% by weight protein; no more than about 1% by
weight
fat; and a gel strength of at least 400, wherein at least a portion of the
protein is
derived by filtration of a mixture of egg yolk lipids and egg yolk proteins.
In some
implementations higher levels of protein are present, including at least 70%
by weight
protein, at least 75% by weight protein, at least 80% by weight protein, at
least 85%
by weight protein, or at least 90% by weight protein. Also, it is possible to
have very
low weight percents of fat in some implementations, including less than 0.5%
by
weight fat in some implementations.
An example method of measuring gel strength is as follows: Weigh up 25 g of
whites into a whirl-pack bag. Add 175 ml of distilled water to the bag, and
place it in
a stomacher in continuous mode for 5 minutes, followed by removal of the bag
from
stomacher and letting it sit for 15-20 minutes. Next, pipet approximately 125
ml of
whites into a casing, and let sit another 3-5 minutes. After 3-5 minutes tap
the sides
of casing to remove air bubbles that have collected on sides. Clasp the casing
at top
end just below the top foam and twist tightly, and secure with a twist tie at
base of
twist and then fold over and secure with rest of twist tie. Next, rinse off
the casing
with deionized water and place in an 80 C water bath for 40 minutes. After 40
minutes remove the casing from the water bath, and cool down with cold running
tap
water for 5-10 minutes Lace the casing in a refrigerator overnight. The next
morning take the casing out of refrigerator for 1 hour.
Using a Rhco meter, use an 8 mm diameter ball as a plunger and set the range
switch at 200/2N for low get and at 2k/20N for high gel testing. The table
speed
should be set at 6 cm/min. Cut off end of casing and peel off, cutting the
sample into
3-4 pieces that are 30 mm long. Place a sample piece in the center of the
table and
press the table button and lift up to just under plunger. Then press the start
button,
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and after the plunger has broken through the sample, press the stop button.
Lower
table and remove sample. To read the printer, with 500 my setting, the left is
0,
middle is 250 and the right side is 500 for gel strength.
It should be noted that, as used in this specification and the appended
claims,
the singular forms "a," "an," and "the" include plural referents unless the
content
clearly dictates otherwise. It should also be noted that the term "or" is
generally
employed in its sense including "and/or" unless the content clearly dictates
otherwise.
It should also be noted that, as used in this specification and the appended
claims, the phrase "configured" describes a system, apparatus, or other
structure that
is constructed or configured to perform a particular task or adopt a
particular
configuration. The phrase "configured" can be used interchangeably with other
similar phrases such as "arranged", "arranged and configured", "constructed
and
arranged", "constructed", "manufactured and arranged", and the like.
This application is intended to cover adaptations or variations of the present
subject matter. It is to be understood that the above description is intended
to be
illustrative, and not restrictive. It should be readily apparent that any one
or more of
the design features described herein may be used in any combination with any
particular configuration. The scope of the present subject matter should be
determined
with reference to the appended claims, along with the full scope of
equivalents to
which such claims are entitled.
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