U.S. patent application number 15/732357 was filed with the patent office on 2018-05-10 for pulse combustion drying of proteins.
The applicant listed for this patent is Pulse Holdings, LLC. Invention is credited to David A. MIRKO, James A. REHKOPF.
Application Number | 20180127458 15/732357 |
Document ID | / |
Family ID | 53520768 |
Filed Date | 2018-05-10 |
United States Patent
Application |
20180127458 |
Kind Code |
A1 |
REHKOPF; James A. ; et
al. |
May 10, 2018 |
Pulse combustion drying of proteins
Abstract
Methods for pulse combustion spray drying of heat-sensitive
protein compositions using high temperature pulsating jets to
atomize and dry the feed simultaneously are described herein.
Methods and compositions described herein provide dried
protein-containing compositions with low protein denaturation and
other useful functional properties at high operational
efficiencies.
Inventors: |
REHKOPF; James A.; (San
Rafael, CA) ; MIRKO; David A.; (Payson, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pulse Holdings, LLC |
Payson |
AZ |
US |
|
|
Family ID: |
53520768 |
Appl. No.: |
15/732357 |
Filed: |
October 30, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14596996 |
Jan 14, 2015 |
9809619 |
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15732357 |
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61927068 |
Jan 14, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 428/2982 20150115;
C07K 1/14 20130101; C07K 14/415 20130101; C07K 14/78 20130101 |
International
Class: |
C07K 1/14 20060101
C07K001/14; C07K 14/415 20060101 C07K014/415; C07K 14/78 20060101
C07K014/78 |
Claims
1-13. (canceled)
14. A dried, heat-sensitive protein composition, the composition
comprising: solid particles including one or more proteins forming
a protein fraction, wherein less than about 10% of the protein
fraction includes denatured proteins; and a total water content of
less than 10% by weight.
15. The dried, heat-sensitive protein composition of claim 14,
wherein the solid particles comprise a hollow morphology.
16. The dried, heat-sensitive protein composition of claim 14,
wherein the solid particles have a mean diameter of about 5
micrometers to about 100 micrometers.
17. The dried, heat-sensitive protein composition of claim 14,
wherein the solid particles have a relative span factor of less
than about 3.4.
18. The dried, heat-sensitive protein composition of claim 14,
further comprising an ash content of less than about 10% by
weight.
19. The dried, heat-sensitive protein composition of claim 14,
wherein the protein fraction is derived from one or more of dried
egg whites, dried milk, dried gelatins, dried casein, dried whey,
dried soy, or dried gluten.
20. (canceled)
Description
BACKGROUND
[0001] Heat-sensitive protein compositions (HSPC) are widely
applicable in food and nutraceutical industries. For example, egg
white is qualified as a multi-purpose ingredient due to its high
nutritional qualities and excellent foaming and gelling properties.
Many HSPCs are commercialized under liquid solution forms but dried
particulate forms can be preferable as they offer longer shelf
lives and enhanced ease of transport, storage, and use. In drying
HSPCs, energy efficiency and product quality are the primary
concerns yet achieving one concern often frustrates the purpose of
the other. High-temperature drying processes can achieve the
highest drying efficiencies, but can have a detrimental effect on
the functional properties of heat-sensitive proteins. For example,
liquid egg whites comprise about 80% to 95% water, and the energy
imparted to evaporate the water can induce protein denaturation
which reduces functional properties of the egg white such as
foaming and gelling properties. Similarly, high temperature drying
of milk can degrade bio-activity of constituent enzymes and overall
product taste.
[0002] Many HSPCs are traditionally dried by spray drying methods,
which include spraying an HSPC feed via rotary atomizers or nozzles
into a hot drying medium to remove moisture and provide a dried
particulate form. In order to operate efficiently, spray drying
must be conducted at HSPC-damaging temperatures, for example
temperatures above a denaturation temperature of one or more
proteins. Most spray dryers operate at temperature below
denaturation temperatures, but process efficiency suffers as a
result. Further, spray dryer rotary atomizers and nozzles clog
easily when conveying higher viscosity or particulate-containing
feeds. Spray dryers also suffer from technical difficulties,
particularly due to wear on rotary atomizers and nozzles which over
time reduce feed flow rate conveying accuracy and increase
maintenance costs and unit down-time.
SUMMARY
[0003] In general, this disclosure describes techniques for drying
heat sensitive protein compositions (HSPD) using high temperature
pulsed air streams. In some Embodiments, the technique includes
using pulsating jets to atomize and dry the feed simultaneously.
The techniques described herein provide high energy efficiency per
unit water evaporated, and provides low-moisture compositions
having superior physical and functional properties.
[0004] In some embodiments, a method for producing a dried
protein-containing composition can include introducing a
heat-sensitive protein composition into a drying chamber, wherein
the heat-sensitive protein composition comprises water and one or
more proteins; drying the heat-sensitive protein composition by
contacting the heat-sensitive protein composition with a pulsed gas
stream of a pulse combustion dryer; controlling the drying chamber
outlet temperature such that it does not substantially exceed a
denaturation temperature of one or more proteins in the
heat-sensitive protein composition; and recovering a dried
protein-containing composition.
[0005] In some embodiments, a dried, heat-sensitive protein
composition can comprise solid particles including one or more
proteins forming a protein fraction, wherein less than about 10% of
the protein fraction includes denatured proteins. In some other
embodiments the dried, heat-sensitive protein composition can
further comprise a total water content of less than 10% by
weight.
[0006] Some embodiments comprise a dried, heat-sensitive protein
composition prepared by a process comprising the steps of:
introducing a heat-sensitive protein composition into a drying
chamber, wherein the heat-sensitive protein composition comprises
water and one or more proteins; drying the heat-sensitive protein
composition by contacting the heat-sensitive protein composition
with a pulsed gas stream of a pulse combustion dryer; controlling
the drying chamber outlet temperature such that it does not
substantially exceed a denaturation temperature of one or more
proteins in the heat-sensitive protein composition; and recovering
a dried protein-containing composition.
[0007] Techniques described herein provide dried egg whites with
superior physical characteristics and properties as compared to egg
whites dried by other traditional drying methods such as spray
drying.
[0008] The details of one or more examples are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages will be apparent from the description and
drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A-F illustrate the operation of a Hemholtz-type pulse
combustor with flapper valves, according to an embodiment of this
disclosure.
[0010] FIG. 2 illustrates a schematic view of a pulse combustor and
atomizer, according to an embodiment of this disclosure.
[0011] FIG. 3A illustrates a schematic of a pulse combustion spray
drying system, according to one or more techniques of this
disclosure.
[0012] FIGS. 3B-C illustrate flow diagrams for pulse combustion
drying methods of heat-sensitive protein compositions, according to
one or more embodiments of this disclosure.
[0013] FIG. 4A illustrates egg white powders dried using pulse
combustion spray dryers, according to an embodiment of this
disclosure.
[0014] FIG. 4B illustrates egg Kangde.TM. white powders dried using
traditional spray drying, according to an embodiment of this
disclosure.
[0015] FIG. 5 illustrates a graph of the size distributions of
pulse combustion spray dried egg whites and Kangde.TM. SD egg white
powders, according to an embodiment of this disclosure.
[0016] FIG. 6A illustrates an SEM image of pulse combustion spray
dried egg white powders, according to an embodiment of this
disclosure.
[0017] FIG. 6B illustrates an SEM image of Kangde.TM. egg white
powders dried using traditional spray drying techniques, according
to an embodiment of this disclosure.
[0018] FIG. 7 illustrates a graph of the differential scanning
calorimetry curves for the pulse combustion spray dried powders and
the LHAD sample powders, according to an embodiment of this
disclosure.
[0019] FIG. 8 illustrates a graph of differential scanning
calorimetry curves for various egg white drying methods, according
to an embodiment of this disclosure.
DETAILED DESCRIPTION
[0020] The energy efficiency and product quality contradiction
described above may be solved by a novel spray drying
technique-pulse combustion spray drying (PCSD). Unlike traditional
spray drying where liquid atomization and drying are separated, the
PCSD technique uses pulse combustion technology to produce high
temperature and high velocity pulsating jets, which are used to
atomize and dry the liquid simultaneously. Since PCSD dryers use
"gas dynamic" atomization and no mechanical atomizers/nozzles are
needed, they can handle liquids with high viscosity and/or high
solid content which are normally problematic for traditional spray
drying. More importantly, PCSD dryers can provide an advantageous
superposition of unsteady gas flow and high-intensity sound waves.
Such a combination increases the momentum and heat/mass transfer
rates in industrial drying processes and thus improves the dryers'
energy efficiency. PCSD dyers have other merits including low
pressure in the liquid feed system, lower maintenance costs, and
enhanced operational control.
[0021] Examples of PCSD apparatus and methods are described in
co-owned U.S. Pat. Nos. 8,517,723 B2, 7,937,850 B2, 8,697,156 B2,
8,037,620 B2, and 8,490,292 B2, and U.S. Application Publication
No.: 2012/0291396 A1, which are herein incorporated in their
entirety.
[0022] As described herein, PCSD techniques have numerous novel
applications for drying of food and nutraceutical materials,
particularly heat-sensitive protein compositions (HSPC). HSPCs can
comprise one or more proteins. In some embodiments, HSPCs can
further comprise water. In other embodiments, HSPCs can further
comprise additional components such as fats and carbohydrates.
Additional components are often common components of a HSPC. For
example, an HSPC such as egg white can contain numerous proteins,
water, fats, and carbohydrates.
[0023] Heat-sensitive protein compositions (HSPC) are compositions
comprising a protein fraction susceptible to degradation by heat.
An example HSPC is egg white, which can include about 80% to about
95% water and a dry matter fraction comprising over about 80%
heat-sensitive proteins. Egg white powders are a desirable
ingredient for many foods such as bakery products, meringues and
meat products, as they have excellent foaming and gelling
properties. Additionally or alternatively HSPCs can include
gelatins, casein, milk proteins, soy proteins, whey proteins,
gluten, or any other composition including proteins susceptible to
degradation by heat. Degradation can include a diminishment of
useful properties, such as physical or functional properties.
[0024] Physical and/or functional properties can include protein
denaturation, protein oxidation, enzymatic activity, foaming
ability, foam stability, gel hardness, gel springiness, particle
morphology, particle size, and color. An application of heat to a
protein can cause denaturation, or an alteration of a protein's
native structure. For example, and alteration can include a protein
losing its native quaternary, tertiary, or secondary structure.
Such an alteration can result in communal aggregation, loss of
solubility, and a change of functional properties such as foaming
and gelling abilities, and bioactivity. In general, the
denaturation temperature of proteins is about 75.about.90.degree.
C., making proteins very susceptible to denaturation in high
temperature drying processes such as traditional spray drying. For
example, up to 70% whey protein isolate can be denatured during
spray drying. The denaturation temperature for a HSPC can include
the denaturation temperature of the most prevalent protein, a
weighted average of the denaturation temperature of the one or more
protein components, or an average of the denaturation temperature
of the one or more protein components. The denaturation temperature
for a HSPC can also be the temperature at which an appreciable
denaturation effect is observed on the proteins of an HSPC.
[0025] Pulse combustion originates from the intermittent (pulse)
combustion the solid, liquid, or gaseous fuel in contrast to the
continuous combustion in conventional burner. Such periodic
combustion generates intensive pressure, velocity, and, to a
certain extent, temperature waves propagated from the combustion
chamber via a tailpipe to the process volume (applicator) such as a
drying chamber. Due to the oscillatory nature of the momentum
transfer, pulse combustion intensifies the rates of heat and mass
transfer and accelerates drying rates.
[0026] FIGS. 1A-F show the operating stages of a Helmholtz-type
pulse combustor 110 with flapper valves 113, which in some
embodiments comprises a component of a PSCD system. Those of skill
in the art will recognize that combustors capable of providing the
operating conditions described herein to be similarly suitable. The
controlling mechanism behind the operation of a pulse combustor is
a complex interaction between an oscillatory combustion process and
acoustic waves that are propagated from the combustor. The major
function of the pulse combustor in a drying system is to supply
heat for moisture evaporation and to generate large-amplitude, high
frequency pressure pulsations within a drying chamber, which can
each separately or in combination enhance drying rates. The strong
oscillating hot flue gas jet generated by the pulse combustor can
also promote dispersion of the feed.
[0027] As shown in FIGS. 1A-F, pulse combustion starts when fuel
121 and combustion air 122 are drawn into the combustion chamber
114 and mixed to form a mixture 120. The mixture 120 is ignited 130
by an ignitor 111, such as a spark plug, and combusts 140 the
mixture 120 explosively, resulting in a rapid pressure rise. At
this moment, the rising pressure closes 171 the valves 113, sealing
the air and fuel inlet ports 112 and forcing the combustion
products 141 to flow out through the tailpipe 115. As the hot flue
gases 141 flow out, the resulting outward momentum causes the
pressure in the combustion chamber 114 to drop to the minimum so
the valves 113 open, which admits fresh fuel 121 and air 122 into
the combustion chamber 114. This new charge ignites itself 160 due
to contact with remnants of hot flue gases 151 left in the tailpipe
from the preceding cycle which reenter the combustion 114 chamber
during the minimum pressure period 150. These combustion cycles
repeat at a natural frequency depending on the geometry of the
combustion chamber and characteristics of the tailpipe-applicator
system. The expelled combustion products 141 are directed into a
drying chamber (not pictured) where they contact a drying
substrate, such as a HSPC.
[0028] FIG. 2 shows how a pulse combustor can be used to atomize
and/or dry a liquid feed. In this and other embodiments, the term
"liquid" can refer to liquids, fluids, fluidized powders, slurries,
suspensions, dispersions, emulsions, and the like. Air 201 is
pumped into the pulse combustor 210 outer shell at a low pressure
where it flows through the unidirectional air valve 212; the air
enters a tuned combustion chamber 214 where fuel 221 is added; the
air valve 212 closes; the fuel-air mixture is ignited by a pilot
211 and combusts or explodes creating hot air which can be
pressurized to, for example, about 2 kPa above the combustion fan
pressure; the hot gases rush down the tailpipe 215 toward the
atomizer 270; the air valve 212 reopens and allows the next air
charge to enter; the fuel valve admits fuel 221; and the mixture
explodes in the hot chamber. This cycle is controllable from about
50 Hz to about 200 Hz, or in some embodiments from about 80 Hz to
110 Hz. Just above the atomizer 270, quench air is blended in to
achieve desired product contact temperature; the exclusive PCS
atomizer releases the liquid feed 219 into a carefully balanced gas
flow, which dynamically controls atomization, drying, and particle
trajectory; the atomized liquid enters a conventional tall-form
drying chamber 280; downstream, the suspended powder is retrieved
using any commercially acceptable means, such as a cyclone and/or
bag house.
[0029] Typically, a pulse combustor may operate at frequencies that
vary from 20 to 200 Hz. Pressure oscillations in the combustion
chamber of the order of .+-.10 kPa produce velocity oscillations of
about .+-.100 meters per second and the velocity of the gas jet
exiting the tailpipe varies from about 0 meters per second to about
200 meters per second. The input power ranges from about 20 kW to
about 1000 kW for commercially available pulse combustors, although
other input power ranges are practicable.
[0030] FIG. 3A shows an example of a pulse combustion spray drying
system 300 which can be used for the techniques described herein.
The system 300 comprises, among other things, a pulse combustion
burner 310 and air supply 322 in fluid communication with drying
chamber 314. Feed 319 is directed into the drying chamber 314 via a
feed conveyer 320. The feed conveyer 320 can comprise a
low-pressure, open pipe feed system, which provides the ability to
process feeds having higher solids contents. This obviates the need
to dilute the feed material in order to atomize it, yielding higher
powder production rates and much lower processing costs per
finished pound. Feed 319 contacts the pulse combustor combustion
air 341 in zone 330. Zone 330 can in some embodiments be referred
to as the high heat zone, wherein feed 319 is exposed to peak
combustion air 341 temperatures. After the feed 319 contacts the
combustion air 341, it travels out of the drying chamber 314 via a
pipe or duct 340. A section of piping after the drying chamber 314,
for example, piping section 341 can be cooled, to maintain the
dried product 315 at a desired temperature. Similarly, a piping
section 321 can be cooled such that feed 319 is not prematurely
exposed to heat, or elevated above a desired initial temperature.
Dried feed 315 can be processed in one or more of a cyclone 350 and
bag house 360, each of which can yield final product 329. Exhaust
air 332 can be expelled at the end of the system line.
[0031] As shown in FIG. 3C, methods for producing a dried
protein-containing composition can comprise drying a HSPC by
contacting 371 the HSPC with a pulsed gas stream of a pulse
combustion dryer. In some embodiments, methods further comprise
introducing 370 a HSPC into a drying chamber. In other embodiments,
methods can further comprise controlling 372 the drying chamber
outlet temperature such that it does not substantially exceed a
denaturation temperature of one or more proteins in the
heat-sensitive protein composition. In some other embodiments,
methods further comprise recovering a dried protein-containing
composition
[0032] Energy-efficient PCSD drying methods can effectively yield
dried HSPC with low denaturation levels, even while utilizing
drying gas having initial contact temperatures exceeding
denaturation temperatures of proteins by 50.degree. C., by
100.degree. C., by 150.degree. C., by 200.degree. C., by
250.degree. C., or by equal to or over 350.degree. C. This is due
to a number of factors, including short residence time of HSPCs
within one or more of the high heat zone and within the PCSD drying
chamber, and high oscillation of HSPCs within a drying chamber.
Under such conditions, an HSPC is dried without raising the HSPC
temperature above its protein denaturation temperature. Drying an
HSPC without raising the HSPC temperature above its protein
denaturation temperature can be achieved in some embodiments by
manipulating one or more of the pulsed gas stream temperature, a
residence time of the heat-sensitive protein composition within the
drying chamber, pulsed gas stream pulse frequency, pulsed gas
stream exit temperature, or feed flow rate. In some embodiments, an
HSPC can be dried using PCSD wherein the HSPC is heated above a
denaturation temperature. However, due to the extremely short
residence times, the HSPC experiences only minimal
denaturation.
[0033] Residence times can include less than about 10 seconds, less
than about 9 seconds, less than about 8 seconds, less than about 7
seconds, less than about 6 seconds, less than about 5 seconds, less
than about 4 seconds, less than about 3 seconds, less than about 2
seconds, less than about 1 second, or less than about 0.5 seconds.
Residence time describes the time that a given feed particle spends
in a drying chamber. In many embodiments, a PCSD drying chamber has
a high heat zone in which a HSPC is only exposed to a maximum
drying gas temperature for a fraction of the total residence time
within the drying chamber. For example, an HSPC can be present in a
high heat zone for less than about 50% of the residence time, less
than about 40% of the residence time, less than about 30% of the
residence time, less than about 20% of the residence time, less
than about 10% of the residence time, less than about 8% of the
residence time, less than about 5% of the residence time, less than
about 4% of the residence time, less than about 3% of the residence
time, less than about 2% of the residence time, or less than about
1% of the residence time.
[0034] Drying methods can further comprise subsequent
low-temperature, long-duration (LTLD) heating of an HSPC after
PCSD. For example, heating of egg white powders at 75-80.degree. C.
for 10-15 days is widely used in industry to offset functional
property losses resulting from traditional spray-drying process. In
some embodiments, LTLD heat treatment comprises heating a
composition to a temperature below a denaturation temperature. In
the same and other embodiments, LTLD heat treatment further
comprises heating a composition for longer than 1 hour, longer than
6 hours, longer than 12 hours, longer than 24 hours, longer than 5
days, or longer than 10 days.
[0035] Drying methods can additionally or alternatively comprise
pasteurization. Pasteurization can include heating a dried HSPC for
an amount of time to a minimum temperature. Minimum times and
temperatures can be determined based on government regulations, for
example. Pasteurization allows an HSPC to be used safely in food
and beverage products without prior heating, cooking, or
baking.
[0036] Drying efficiency of the methods described herein can be
measured using the latent heat of evaporation of water compared to
the actual energy consumption of a drying technique per unit of
dried moisture. Drying efficiency can be measured in total, or for
discrete drying steps. For example, the efficiency of a drying
method which includes PCSD or SD and subsequent LTLD drying can
describe the combined drying efficiency for the entire process, or
individually for the PCSD phase and the subsequent LTLD drying
phase. Similarly, efficiency can be provided for a percent moisture
reduction. For example, efficiency can described the drying
efficiency of one or more drying stages that bring an HSPC from 80%
water to 10% water. PCSD methods are desirable as they provide high
drying efficiencies in drying HSPCs to low moisture contents
without compromising the beneficial attributes of the HSPCs. In
some embodiments, PCSD methods are at least 25% more efficient than
conventional spray drying. PCSD methods can be up to 50% more
efficient than conventional spray drying.
[0037] In particular, PCSD techniques may be applied to drying
heat-sensitive materials, such as HSPC, and biomaterials to achieve
both high product quality and process energy efficiency as compared
to heat-sensitive materials dried by conventional techniques such
as spray drying. Drying can include removing moisture, or the
presence of liquids. In some embodiments moisture includes
water.
[0038] In many embodiments, a pre-dried HSPC can comprise one or
more of water, one or more protein, one or more carbohydrates, one
or more fats, and one or more oils. A dried HSPC can comprise less
than about 30% water, less than about 20% water, less than about
10% water, less than about 8% water, less than about 5% water, less
than about 1% water. Dried HSPCs provided herein comprise low
amounts of ash, particularly as compared to HSPCs dried by
traditional spray drying. A dried HSPC can comprise less than about
10% ash, less than about 7% ash, less than about 5% ash, less than
about 4% ash, less than about 3% ash, less than about 2% ash, or
less than about 1% ash. Dried HSPCs provided herein further have
low protein denaturation, particularly as compared to HSPCs dried
by commercially viable methods, in particular traditional spray
drying. The protein fraction of a dried HSPC can have a percent
protein denaturation less than about 10%, less than about 8%, less
than about 6%, less than about 4%, less than about 2%, less than
about 1.5%, less than about 1%, or less than about 0.5%.
[0039] PCSD techniques can be applied to drying HSPCs to yield
compositions with superior color characteristics. Because of the
short residence times of a material in PCSD, lower dryer outlet
temperatures, and reduced oxygen concentration in the flue gas as
compared to traditional spray drying, HSPC materials dried by PCSD
exhibit superior color quality. A color change observed in an HSPC
after drying can indicate heat damage, oxidation, and/or protein
denaturation during the drying process. Similarly, the color of a
dried HSPC can be used to compare physical properties with another
dried HSPC or to determine if a particular dried HSPC meets a
physical specification, such as percent protein denaturation.
[0040] In some embodiments, color quality of a dried HSPC can be
measured, in part, by whiteness, or a reduced diminishment of
whiteness. In other embodiments, color quality of a dried HSPC can
be measured, in part, by a reduced darkening of a dried HSPC. Color
quality measurements can be made in comparison to a reference
material, such as a commercial product or a material dried by
traditional spray drying. Color quality measurements can be made
using the CIE 1976 L/a/b/ colour space system, wherein L represents
color lightness (black is defined as L=0, and diffuse white is
defined as L=100), "a" represents the green-magenta scale (negative
a values denote green, and positive a values denote magenta, and
"b" represents a yellow-blue scale (negative b values denote blue,
and positive b values denote yellow).
[0041] For many commercial products, for example dried egg whites,
a desirable whiter color is achieved by adding additives and/or
colorants such as TiO.sub.2. The PCSD drying process described
herein is capable of providing whiter products, such as dried egg
whites and powdered milk, which advantageously reduce or eliminate
the need for additives. Accordingly, an HSPC dried by PCSD can
comprise little to no additives while still having a desirable
white color.
[0042] Embodiments herein provide for one or more of smaller
particle size and more consistent particle size of a HSPC dried by
PCSD. A smaller particle diameter creates a higher surface area to
volume ratio of a composition, which increases contact surface with
the drying gas and subsequently drying rate and efficiency.
Additionally, embodiments herein provide for dried HSPCs which have
a hollow morphology. Both smaller particle size and hollow
morphology are desirable qualities, which, in some instances, allow
for easier and/or more rapid reconstitution of the dried HSPC.
Reconstitution can include combining an HSPC with a liquid, such as
water.
[0043] Consistent particle size can be advantageous for packaging
and product aesthetic purposes. Further, larger and/or irregular
particle sizes can indicate one or more of a higher degree of
protein agglomeration caused by denaturation, and inconsistent
atomization within a dryer. HSPCs dried by PCSDs have higher
particle size consistency as compared to HSPCs dried by traditional
spray drying methods. This is because PCSD utilize low pressure
feed conveyers to meter feed into a drying chamber, rather than
nozzles or rotary disk atomizers which wear out over time and cause
inconsistent feed conveying and atomization. Inconsistent feed
conveying and atomization further leads to less control over the
temperature differential between the drying gas and feed, and, in
some cases, a higher degree of protein denaturation. In some
embodiments, a HSPC dried by PCSD can have a relative span factor
(RSF) of less than about 3.4, less than about 3.2, less than about
3.0, less than about 2.8, or less than about 2.6. (RSF) indicates
uniformity of size distribution and is calculated according to the
equation RSF=(D90-D10)/D50, where D10, D50, D90 are particle sizes
for 10%, 50% and 90% cumulative mass respectively. An RSF closer to
1 indicates a more uniform size distribution. In other embodiments,
a HSPC dried by PCSD can have a mean particle diameter of about 5
.mu.m to about 100 .mu.m, about 10 .mu.m to about 80 .mu.m, about
20 .mu.m to about 60 .mu.m, about 30 .mu.m to about 40 .mu.m, or
about 35 .mu.m.
[0044] Conventional drying processes such as traditional spray
drying can diminish useful physical properties of HSPC. In
particular, the foaming ability, foam stability, gel hardness, and
gel springiness of an HSPC can be diminished.
[0045] The compositions and methods herein provide dried HSPCs
having superior foaming abilities as compared to HSPCs dried by
conventional methods. Further, HSPCs can have adequate or superior
foaming ability, foam stability, gel hardness, and gel springiness
without the addition of additives such as soaps. In some
embodiments dried HSPCs can further comprise additional additives
to enhance physical properties, such as foaming ability, foam
stability, gel hardness, and gel springiness. In some embodiments,
dried HSPCs can further comprise sodium lauryl sulfate and/or
soaps. In many embodiments, additives are chosen such that they are
suitable for consumption by humans and/or animals.
[0046] The compositions and methods herein also provide dried HSPCs
having superior gelling abilities as compared to to HSPCs dried by
conventional methods. Dried HSPCs provided herein can further
comprise additional additives which may enhance foaming
ability.
Example One: Egg White Drying by PCSD Techniques
[0047] Production of the egg white powder was conducted on a PCSD
pilot installation as shown in FIG. 3. The process parameters were
monitored and their values were used to calculate the energy
efficiency of the PCSD drying process. The physical, chemical and
functional properties of PCSD dried egg white powders compared with
the properties of a commercial product obtained by traditional
spray drying, and an experimental control dried by low heat hot air
drying.
[0048] The pulse combustion spray drying pilot testing installation
was developed by Pulse Holdings LLC, USA, and consisted of a pulse
combustor, a tall-form drying chamber, a cyclone and a bag house.
The installation was designed to have a heat release of 29.3 kW and
evaporative capacity of 40 kg water/hour. The pulse combustor
operated on the gaseous fuel-propane and the tall-form drying
chamber had a diameter of 1.3 m, height of 3 m and volume of 4
m.sup.3. A-low pressure, open pipe feed system was used supply the
liquid.
[0049] The raw material, GREAT VALUE.TM. 100% liquid egg white, was
purchased from local Wal-Mart store in Payson, Ariz., USA. The
material comprised 10.87% protein, almost 0.0% total fat, 2.17%
total carbohydrate, 86.96% water, according to the product label.
Feed solid was therefore 13.04%. 25 kg of liquid egg white was
purchased and mixed in the feed tank. At the beginning of the
experiment, the PC dryer was ignited and then warmed up in the
first 30 minutes without liquid feed. During warming up, the PC
dryer setup was being adjusted to an optimum drying condition for
the liquid egg whites: the heat release was set to be 83.000 BTU/hr
(24.32 kW) and taking the heat value of propane as 2200 BTU/m.sup.3
(2321 kJ/m.sup.3), the fuel flow rate was calculated to be 0.63
m.sup.3/min. The combustion gas temperature at the atomizer was
adjusted to be 326.6.degree. C.
[0050] After the warming up of the PC dryer, liquid egg white was
fed into the dryer at a speed of 0.6 kg/min. The egg whites were
atomized and dried simultaneously by the high velocity, oscillating
combustion gas exiting the pulse combustor and entering the drying
chamber. The gas temperature in the chamber bottom was measured to
be 76.6.degree. C. and ambient air temperature was 25.degree. C.
The whole egg white drying process lasted about 28 minutes. The
dried egg white powders were collected from the cyclone, baghouse,
and the blow-down of the wall deposit on the drying chamber. All
the powders were mixed together and stored in a tightly closed bag
for sequent properties testing. Table 1 summarizes the operation
data obtained for the PCSD process of egg white:
TABLE-US-00001 TABLE 1 Operation data for the PC spray drying
process of egg white: Feed rate of the liquid egg white 0.6 kg/min
Initial moisture content 86.96% Heat release of PC combustor 24.32
kw Gas temperature at the feeding point 326.6.degree. C. Gas
temperature at the drying chamber 76.6.degree. C. outlet Ambient
air temperature 25.0.degree. C. Running time 28 min Dry solids fed
during run 2.19 kg Powders from cyclone 1.32 kg (60.28%) Powders
from chamber wall blowdown 0.29 kg (13.24%) Powders from chamber
wall brushdown -- Powder from baghouse -- Total yield 73.52% Final
moisture content of powders 8.11% Water evaporation rate 33.62 kg
water/hr Volume evaporation rate 8.41 kg water/hr m.sup.3 Energy
consumption 2604 kJ/kg water evaporated
[0051] From Table 1, it can been seen that when the PC dryer
operated in a heat load of 24.32 kw (80% of its design capability),
the dryer can reduce the moisture content of the egg white from its
initial 86.96% to the final 8.11% in a feeding rate of 0.6 kg/min.
In this condition, the evaporation rate of the PC spray dryer was
calculated to be 33.62 kg water/hr (84% of its designed capability)
and the produce capability was 36 kg liquid egg white/hr. The
energy consumption was calculated to be 2604 kJ/kg water
evaporated, which is slightly higher than the water evaporation
latent heat of 2258 kJ/kg. Compared with the traditional spray
dryers with energy consumptions of 4500-11500 kJ/kg, the PCSD dyer
has a very low energy consumption and high energy efficiency. The
drying gas temperature in the PC dryer reached 326.6.degree. C.
compared to traditional spray dryers which use a drying gas
temperature of 110-150.degree. C. for heat sensitive food
materials. Using the latent heat of evaporation as a benchmark for
efficiency, the PCSD operated with an 86.7% efficiency, as compared
to traditional spray dryers which operate with a 19.6% to 50.2%
efficiency.
[0052] Table 1 shows that 60.28% dry solid feed was collected from
the cyclone and 13.24% dry solid was collected from the drying
chamber wall blowdown at the end of the pilot test. The total yield
of the egg white dry solid feed is about 73.52%. It was observed
that the egg white powders deposited on the chamber wall can be
easily blown down using the compressed air. The fact means that the
wall deposit of egg white powders was minor in the PC spray dryer.
The about 26.48% dry solid feed was lost largely due to the
multi-purpose cyclone of the pilot dryer which was not optimized
for egg white powder collection.
[0053] The measurement of product colors were repeated four times
and three samples were analyzed for other product properties. The
data were processed to obtain the maximum, minimum, mean value,
standard deviation, and range as shown in Tables 2-4. The physical,
chemical and functional properties of the egg white powders
obtained by the PCSD technique were measured and compared with the
ones of a commercial egg white powder product obtained using
traditional SD technique from Kangde Company, Nantong City,
China.
[0054] The major components of the initial egg white include water,
protein, fat and carbohydrate. The water content, M.sub.w, was
measured using the traditional drying oven method. The mass
fraction of total protein, M.sub.p, was measured using the Kjeldahl
determination method according to the Chinese national standard
(GB/T5009.5-2010). The mass fraction of the total fat, Mf, was
measured using Soxhlet extraction method according to the Chinese
national standard (GB/T 1477.2-2008). The concentration of
carbohydrate, M.sub.c, was calculated by the equation (1):
M.sub.c=1-(M.sub.w+M.sub.p+M.sub.f) (1)
[0055] The initial liquid egg white comprised 10.87% protein,
almost 0.0% total fat, 2.17% total carbohydrate, 86.96% water. The
PCSD powders comprised 8.11.+-.0.13% water, 73.97.+-.1.45% protein,
0.18.+-.0.03% total fat, 13.17% total carbohydrate and 4.57%
ash.
[0056] The color of the PCSD and SD egg white powders was measured
using the DC-P3 colorimeter (Beijing Xingguang Color Measurement
Instrument Co., Ltd, Beijing, China). The color was measured using
an absolute measuring mode following the manufacturer's instruction
and calculated automatically using the CIE 1976 L/a/b/ colour space
system (International Commission on Illumination, 2008). Table 2
shows color parameters for the PCSD dried egg white, and the
Kangde.TM. spray dried egg white:
TABLE-US-00002 TABLE 2 Statistics of the Color Parameters for PCSD
and Kangde .TM. Spray Dried Egg White: Standard Items Maximum
minimum Mean Deviation Range PCSD powders L 79.90 79.86 79.88 0.02
0.04 a -4.98 -4.94 -4.96 0.02 0.04 b 8.62 8.60 8.61 0.01 0.02 SD
powders L 77.92 77.91 77.91 0.01 0.01 a -6.23 -6.20 -6.21 0.01 0.03
b 10.42 10.31 10.35 0.05 0.11
[0057] As shown Table 2, the PCSD dried egg white powders have a
smaller mean particle diameter than the traditional SD dried egg
white powders. FIGS. 4A and 4B show the pulse combustion spray
dried and traditional spray dried egg white powders, respectively.
The PCSD powders have a white color while the SD powders have a
pale yellow color. When measured using the DC-P3 colorimeter, the
PCSD powders had an L value of 79.87, an a value of -4.96 and a b
value of 8.60. While the SD powders had an L value of 77.91, an A
value of -6.21 and a B value of 10.33. The whiter color of the PCSD
powders indicates a lower degree of protein denaturation as
compared to the SD powders, among other things.
[0058] The particle size distribution of PCD egg white powders were
measured using the laser diffraction method on a LS-C(III) Laser
Particle Size Analyzer (OMEC, Zhouhai, China) with a size range of
0.1-1000 .mu.m. Each sample was measured three times and the size
distribution curves were plotted in FIG. 5 in comparison with spray
dried egg whites. The differential distribution in FIG. 5 is the
percentage of particles from the total are within a specified size
range. The cumulative distribution is the sum of the differential
distribution. The distribution width expressed as the relative span
factor (RSF) was calculated according to the equation
RSF=(D90-D10)/D50, where D10, 50, D90 were particle sizes for 10%,
50% and 90% cumulative mass respectively.
[0059] The D50 diameter of the PCSD powders was 20.15 .mu.m while
the SD powders had a D50 diameter of 54.74 .mu.m. The RSF
parameters, which are used to express the particle size uniformity,
are 2.71 for the PCSD powders and 3.42 for the SD powders
respectively, showing the PCSD powders had a more consistent
particle size. As shown in FIG. 5, the PCSD dried egg white powders
have a smaller mean particle diameter and tighter size distribution
than the traditional SD dried ones. A smaller particle diameter
creates a larger surface area to volume ratio of the egg white that
increases drying rate.
[0060] Morphologies of the PCSD and SD egg white powders were
analyzed using the SU-1510 Scanning Electron Microscopy (Hitachi,
Japan). Samples were prepared on the aluminum SEM stubs. The
mounted powders were sputter-coated with gold-palladium, achieving
a coating thickness of approximately 15 nm. The electron
micrographs were produced by the SEM in secondary electron mode
with an operating voltage of 5 keV. A range of 50 to 1500
magnification was used in the images.
[0061] FIGS. 6A and 6B show the SEM images of PCSD and SD egg white
powders, respectively. From FIGS. 6A and 6B, it can be seen that
the PCSD powders had a superior particle surface characteristics.
The SEM images showed that most PCSD powders were single and
disperse, with a sphere shape and smooth surface. By contrast, the
SD powders easily aggregated to form bigger particles that had
various shapes and coarse surface. Also, the PCSD powders had a
hollow structure while SD powders had a dense solid structure. This
hollow structure may be caused by fast drying rate and short
residence time of the egg white in the PC dryer, which does not
allow droplets to shrink fully. In contrast, the moderate drying
rate and low temperatures of traditional spray drying allow egg
white droplets to fully shrink and create a denser, solid
structure.
[0062] The protein denaturation level of the egg white powders was
determined using a differential scanning calorimetry (DSC) method
on a DSC204 FI differential scanning calorimeter (Netzsch, German).
Samples of 8.7 mg egg white powders were loaded in hermetically
sealed aluminum pans using a pipette. An empty pan was used as
reference. Samples were first equilibrated at 30.degree. C. for 5
minutes and then, the temperature was raised to 150.degree. C. at a
speed of 5.degree. C./min. FIG. 7 shows the DSC curves for the PCSD
powders and LHAD sample. Total denaturation enthalpies were
calculated from the DSC curves, and the degree of denaturation in
percentage relative to the low temperature hot air dried (LHAD)
sample was calculated. The LHAD sample was obtained by drying the
initial liquid egg white to a dry solid with final moisture of 8%
in a hot air convective drying oven using a drying air temperature
of 40.degree. C. The low drying heat of the LHAD method as compared
to the egg white protein denaturation temperature (89.degree. C.)
allows a 0% protein denaturation to be assumed.
[0063] From FIG. 7, it can be seen that the egg white protein
denaturation temperature was about 89.degree. C. The protein
denaturation degree of the PCSD powder relative to the LHAD sample
was 98.4%, indicating that little protein denaturation occurs in
the PC drying process (e.g., 1.6% protein denaturation). This is
supported by Table 1, which shows a drying chamber gas outlet
temperature (76.6.degree. C.) below the egg denaturing
temperature.
[0064] Foaming ability (FA) and foam stability (FS) of egg white
powders were measured by mixing dried egg white powders with
distilled water to form a 40% mass fraction egg white solution.
Next, the pH of a 25 ml egg white solution was adjusted to 8. The
solution was then homogenized using an emulsification machine at
the speed 14000 min.sup.-1 for 2 minutes and a post-emulsification
volume, V.sub.0, was measured. After standing for 30 minutes, the
new volume, V.sub.30, was measured. The FA and FS were calculated
using the following equations (2) and (3) respectively.
FA = V 0 - V int V int .times. 100 % ( 2 ) FS = V 30 - V int V 0 -
V int .times. 100 % ( 3 ) ##EQU00001##
where V.sub.int is the initial volume of the solution, 25 ml. Table
3 shows the measured foaming properties of the PCSD, Kangde.TM. SD
and LHAD egg white powders:
TABLE-US-00003 TABLE 3 Statistics of the foaming properties for
PCSD, Kangde .TM. SD egg white powders and LHAD sample: Standard
Items Maximum minimum Mean Deviation Range Foaming ability (%) PCSD
28.0 24.8 26.3 1.3 3.2 SD 38.0 37.2 37.7 0.4 0.8 LHAD 38.0 32.0
36.0 2.8 6 Foam stability (%) PCSD 96.9 88.7 92.8 3.4 8.2 SD 96.8
95.8 96.5 0.5 1 LHAD 84.2 73.7 79.7 4.4 10.5
[0065] In Table 3, it can be seen that the Kangde.TM. SD powders
had the best mean foaming ability of 37.73% and foam stability of
96.46%, which is likely attributed to soap additives not present in
the PCSD sample. The LHAD sample had a similar mean foaming ability
with the SD powders, but its mean foam stability was low (79.56%)
as compared to the PCSD sample (92.8%). The additive-free PCSD
powders exhibited comparable foam stability to the SD powders.
[0066] Gelling properties of egg white powders were measured by
mixing dried egg white powders with distilled water to form a 40%
mass fraction egg white solution. Next, the pH of a 25 ml egg white
solution was adjusted to 8. Egg white gels were prepared by heating
300 mL of the egg white solution with a 19% protein concentration
in plastic tubes in a water bath at 80.degree. C. for 1 hour, and
subsequently cooled at room temperature for at least 4 hours. After
removing the tubes, cylindrical samples (3 cm diameter, 2 cm high)
were cut using two parallel metal wires. The texture of the gel
samples was measured using a TA-XT2 texture analyzer (Stable Micro
System Ltd, UK). A 20 mm diameter plate probe was used a texture
profile analysis (TPA) in a double compression test to penetrate to
50% depth at a penetration speed of 2 mm/s. The gel hardness and
springiness were calculated from the TPA system. Table 4 shows the
measured gelling properties of the PCSD, Kangde.TM. spray dried,
and LHAD egg white powders:
TABLE-US-00004 TABLE 4 Statistics of the gelling properties for
PCSD, Kangde .TM. SD egg white powders and LHAD sample: Standard
Items Maximum minimum Mean Deviation Range Hardness (g) PCSD 1082.3
900.0 957.6 88.3 182.3 SD 520.7 450.6 486.5 28.7 70.1 LHAD 1120.4
984.6 1080.4 68.1 135.8 Springiness (%) PCSD 96.1 91.5 94.1 1.9 4.6
SD 90.3 83.7 85.1 3.8 6.6 LHAD 92.4 82.8 88.3 4.1 9.6
[0067] In Table 4, the LHAD sample has the best gelling properties
with a hardness of 1100 g. Compared with the LHAD sample, there is
a slight reduction of 11.3% for the PCSD powder but a drastic
reduction of 55% in hardness for the Kangde.TM. SD powders. From
Table 4, it can be concluded that egg whites powders dried by PCSD
techniques have superior gelling properties than egg white powders
dried by traditional SD operations.
Example Two: Differential Scanning Calorimetry (DSC) Analysis of
Various Egg White Drying Techniques
[0068] Egg whites were dried using hot air drying, vacuum freeze
drying, traditional spray drying (SD) and PCSD, and heat release
was measured using DSC. DSC was performed using an SDT-Q600
Synchronism Thermal Analyzer (TA instrument, USA). Measurement
conditions included a temperature range of 20-150.degree. C., a
temperature increase rate of 5.degree. C./min, and sample weights
of 15-20 g. Hot air drying was conducted by drying egg whites in a
hot air drying oven at 45.degree. C. Vacuum freeze drying was
conducted by freezing egg whites to -80.degree. C., and
subsequently drying in a vacuum freeze dryer. Traditional SD and PC
spray drying of egg whites was conducted using respective methods
as described above.
[0069] DSC results are shown in FIG. 8. While hot air drying and
vacuum freeze drying methods offer the highest heat release at
lower temperatures, these methods are not commercially viable. Hot
air drying yields high quality dried products, but is too
inefficient to warrant use outside of a laboratory environment.
Freeze drying is similarly slow, but also expensive and cumbersome.
Among the two commercially viable drying methods, it can be seen
that PC spray drying methods have significantly higher heat release
than traditional SD methods at lower temperatures (i.e., below
about 80.degree. C.). High heat release below protein denaturation
temperatures allows for efficient drying without degradation to a
dried sample, such as a HSPC.
* * * * *