U.S. patent application number 10/319080 was filed with the patent office on 2003-06-12 for bleached bran and bran products and methods of preparation.
This patent application is currently assigned to General Mills, Inc.. Invention is credited to Metzger, Lloyd E., Monsalve-Gonzalez, Adelmo, Prakash, Aruna, Roufs, John G., Valanju, Mayur Subhash.
Application Number | 20030108652 10/319080 |
Document ID | / |
Family ID | 24663744 |
Filed Date | 2003-06-12 |
United States Patent
Application |
20030108652 |
Kind Code |
A1 |
Monsalve-Gonzalez, Adelmo ;
et al. |
June 12, 2003 |
Bleached bran and bran products and methods of preparation
Abstract
A method of bleaching bran, comprising treating bran with a
hydrogen peroxide solution to produce lightened bran having fewer
native flavor components is disclosed. In one embodiment, a
bleached bran product suitable for admixing with whole wheat flour
to produce white whole wheat flour having an "L" value on the
Hunter scale of at least about 75 is disclosed. In one embodiment,
cleaned bran is treated with a solution of chelating agents to
remove or inactivate transition metals. Thereafter, exposure to
oxidant substances, such as hydrogen peroxide, ozone, and so forth,
in the presence of an alkaline compound produces bleached bran,
which can be washed and dried for use in products such as flours,
pastas, and so forth.
Inventors: |
Monsalve-Gonzalez, Adelmo;
(Plymouth, MN) ; Metzger, Lloyd E.; (Champlin,
MN) ; Prakash, Aruna; (Plymouth, MN) ;
Valanju, Mayur Subhash; (Brookfield, WI) ; Roufs,
John G.; (Maple Grove, MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
General Mills, Inc.
|
Family ID: |
24663744 |
Appl. No.: |
10/319080 |
Filed: |
December 12, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10319080 |
Dec 12, 2002 |
|
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09663914 |
Sep 18, 2000 |
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Current U.S.
Class: |
426/615 |
Current CPC
Class: |
A21D 2/04 20130101; A23L
7/115 20160801; A23L 5/49 20160801 |
Class at
Publication: |
426/615 |
International
Class: |
A23K 001/00 |
Claims
What is claimed is:
1. A method of bleaching bran, comprising: treating bran with a
hydrogen peroxide solution to produce lightened bran having fewer
native flavor components, the bran derived from a cereal grain.
2. The method of claim 1 wherein the hydrogen peroxide solution has
a pH of about 6 to 7, further including adding an aqueous alkaline
solution to raise the pH of the bran and hydrogen peroxide solution
to about 9 to 9.5 wherein the aqueous alkaline solution is added in
amounts of about 10 to 15 parts (dry weight) of alkaline material
per 100 parts grain.
3. The method of claim 2 wherein the hydrogen peroxide solution is
an aqueous solution having a concentration of between about 6 and
40%, further wherein the hydrogen peroxide is added in amounts of
about 1 to 20 parts of hydrogen peroxide to about 100 parts of
bran.
4. The method of claim 3 wherein the hydrogen peroxide solution and
alkaline solution are heated together with the bran at a
temperature of about 80 to 90.degree. C. for about 20 to 60
minutes.
5. The method of claim 3 wherein the hydrogen peroxide solution and
alkaline solution are heated together with the bran under a
pressure of about 103.4 to 138 kPA (15 to 20 psi) and a temperature
of about 120 to 130.degree. C. for about one (1) to five (5)
minutes.
6. The method of claim 2 wherein the cereal grain is selected from
the group consisting of wheat, rice, barley, corn (maize), oats,
triticale, amaranth, soybeans and mixtures thereof.
7. The method of claim 6 wherein the cereal grain is red wheat or
white wheat.
8. The method of claim 7 wherein the cereal grain is a soft winter
white wheat that is milled to produce a light bran.
9. The method of claim 1 wherein the bran each have a particle size
of at least about 100 microns.
10. The method of claim 1 further comprising: prior to bleaching,
treating the bran with a chelating agent to remove transition
metals to produce treated bran; and blanching the treated bran to
inactivate catalase and peroxidase enzymatic systems to produce
blanched bran.
11. The method of claim 10 wherein the bran are treated with the
chelating agent for about one (1) to 15 minutes at a temperature of
about 70 to 90.degree. C.
12. The method of claim 10 wherein the chelating agent is selected
from the group consisting of orthophosphate, metaphosphate,
pyrophosphate, polyphosphate, calcium EDTA and sodium EDTA.
13. The method of claim 12 wherein the chelating agent is calcium
EDTA or sodium EDTA in a concentration of between about 0.02 and
0.1%.
14. The method of claim 10 wherein the blanching step is performed
at a temperature of between about 75 to 85.degree. C. for about
three (3) to ten (10) minutes, further wherein residual enzyme
activity is below about 10 CIU/g bran following the blanching
step.
15. The method of claim 10 further comprising: washing and rinsing
the bran to produce wet bran; filtering the wet bran to produce
filtered wet bran; treating the filtered wet bran with catalase to
remove residual hydrogen peroxide to produce treated filtered wet
bran; and drying the treated filtered wet bran to produce dried
bleached bran having an L value on the Hunter scale of between
about 82 and 93.
16. The method of claim 15 wherein there are at least two washing
and rinsing steps, each followed by a filtering step, prior to the
bleaching step and at least one washing and rinsing step followed
by at least one filtering step after the bleaching step.
17. The method of claim 15 wherein between about 0.1 and 0.4% of
catalase, by weight, of bran is added to the filtered bran at a
temperature of about 60.degree. C., further wherein the hydrogen
peroxide concentration is reduced to less than about five (5) PPM
following catalase treatment.
18. A method for bleaching bran comprising treating wet bran with
an oxidant in the presence of heat, the oxidant selected from the
group consisting of hydrogen peroxide, ozone and peracetic
acid.
19. The method of claim 18 wherein a combination of hydrogen
peroxide and ozone bleaching is used.
20. A method of bleaching cereal grains, comprising: treating bran
with 0.02 to 0.1% EDTA to produce treated bran; washing, rinsing
and filtering the treated bran to produce filtered and treated
bran; blanching the filtered and treated bran at 75 to 85.degree.
C. for about three (3) to 10 minutes to produce blanched bran;
washing, rinsing and filtering the blanched bran to produce
filtered and blanched bran; adding a one (1) to 10% alkaline
solution and 30 to 35% hydrogen peroxide solution to the filtered
and blanched bran at a temperature of about 80 to 85.degree. C. for
about 4 to 5 minutes to produce bleached bran; washing, rinsing and
filtering the bleached bran to produce filtered and bleached bran;
adding about 0.14 to 0.4% of catalase, obtain from a fungi called
Aspergillus nigers at a temperature of between about 55 to
65.degree. C. to the filtered and bleached bran to produce
re-catalased bleached bran; and drying the re-catalased bleached
bran in a drum dryer to produce dried bleached bran having about
five (5) to 13 g of water per 100 g of dry bran and an L value of
at least about 75.
21. A bleached bran product suitable for admixing with whole wheat
flour to produce white whole wheat flour having an L value on the
Hunter scale of at least about 82.
22. The product of claim 21 wherein about five (5)% bran, by
weight, is added to the whole wheat flour.
23. The product of claim 21 having an L value of between about 82
and 93.
24. The product of claim 21 having a water absorption value about
six times higher than native bran.
25. The product of claim 21 wherein native flavor components are
reduced or deactivated.
26. The product of claim 21 having an antioxidant activity about 15
to 35% higher than native bran.
27. The product of claim 26 wherein the antioxidant activity is
increased due to increased availability of ferulic acid.
28. A product prepared according to the process of claim 1.
29. A product prepared according to the process of claim 18.
30. A product prepared according to the process of claim 20.
31. A whole wheat flour prepared from peroxide-bleached bran, the
whole wheat flour having an L value on the Hunter scale of about
and a dietary fiber content of about 10 to 12%.
32. The whole wheat flour of claim 31 substantially free of
hydrogen peroxide.
33. The whole wheat flour of claim 32 prepared from soft white
wheat or hard white wheat.
34. The whole wheat flour of claim 33 prepared from light bran.
35. The whole wheat flour of claim 33 having a pH of about 6.3 to
6.7.
36. A finished baked good prepared from the whole wheat flour of
claim 31.
37. The whole wheat flour of claim 31 admixed with sugar, salt, and
leavening.
38. A bleached bran product suitable for use as an additive in
foods.
39. The bleached bran product of claim 37 wherein the product is
added to foods selected from the group consisting of dry mixes,
ready-to-eat cereals and soy.
40. A refrigerated uncooked or bakeable dough product comprising
bleached bran.
41. A ready-to-eat cereal comprising bleached bran.
42. A cooked cereal dough comprising bleached bran.
Description
RELATED APPLICATION
[0001] The present application is a divisional of U.S. patent
application Ser. No. 09/663,914, filed Sep. 18, 2000, which is
incorporated herein by reference.
FIELD
[0002] The present invention relates to bleached grains and in
particular to bleached brans.
BACKGROUND
[0003] Whole grain products are known to be rich in dietary fiber
and other nutrients. Although there are many health benefits
associated with the consumption of whole grain products, many
consumers avoid such products due to the relatively poor taste and
color associated with whole wheat flours. This is especially true
of children, who can be particularly selective in food choices.
[0004] Attempts to overcome these problems include use of ground-up
white wheat rather than red wheat in an attempt to mask or reduce
the bitter taste of the bran. However, the flour produced with
these methods still has a bitter flavor and yields a baked product
with a dark color.
[0005] It is generally believed that the presence of bran is a
major cause of the taste and color problems associated with whole
wheat flours. Bran contains phenolic compounds, which may be
responsible for the bitter and astringent taste. Certain phenolic
compounds, such as tannins, can impart a brown or even grayish
color to flour, particularly flours made from red wheat. Thus,
conventional processes used to produce non-whole wheat or white
products attempt to remove as much bran as possible during milling,
although this is also removing a key nutritional component of the
kernel. Specifically, bran not only contains fiber, but other
healthy components that are known to be useful in preventing
cancer, such as colon cancer.
[0006] Thus, there is a continuing need for whole wheat flours that
can be used to provide finished whole wheat products that look and
taste as good as those made with "regular" white flour. Also, there
is a continuing need for bran products that are useful for addition
to regular white or patent flour for the purpose of providing whole
grain flours that are comparable to patent or white flours in
taste, appearance and baking qualities, notwithstanding the
presence of added bran in the flours.
SUMMARY
[0007] A method of bleaching bran, comprising treating bran with a
hydrogen peroxide (H.sub.2O.sub.2) solution to produce lightened
bran having fewer native flavor components is disclosed. In one
embodiment, a bleached bran product suitable for admixing with
wheat flour to produce white whole wheat flour having an "L" value
on the Hunter scale of at least about 75 is disclosed.
[0008] The present invention provides a chemical lightening
treatment or wetting process, or wet bleaching process that
bleaches the bran portion of wheat kernels after cleaning and
milling to produce a bleached bran without the bitter aftertaste
normally associated with whole grain products. This is unlike
conventional white grain processes that seek removal of bran in
order to provide a product without a bitter taste. Bleaching only
the bran portion of the wheat instead of the entire kernel also
eliminates any potentially negative effects on flour functionality
caused by bleaching an intact kernel.
[0009] In one embodiment, the present invention provides an
intermediate bleached bran product. In another embodiment, a white
whole grain flour having a high fiber content (10 to 12%) and other
nutritional advantages of a whole grain flour that nonetheless has
a white color and bland flavor comparable to conventional white
flour is provided. The white whole grain flour comprises a
conventional flour and fortifying amounts of the intermediate
bleached bran product.
[0010] In one embodiment, cleaned bran is treated with a solution
of chelating agents to remove or inactivate transition metals. This
is followed by a blanching or heat treatment step to inactivate
indigenous catalase enzymes. Thereafter, exposure to oxidant
substances, such as hydrogen peroxide, ozone, and so forth, in the
presence of an alkaline compound produces bleached bran, which can
be washed and dried for use in products such as flours, pastas,
cereals, cereal bars, functional foods, and so forth.
[0011] In a specific embodiment, bran is heated with a 600 PPM EDTA
solution at a temperature of about 70 to 90.degree. C. for about
five (5) minutes and then washed with deionized water. About 18 ml
of about 30% hydrogen peroxide is added for every 50 grams of bran.
A sufficient amount of sodium hydroxide is added to raise the pH to
about 9-9.5 so that the hydrogen peroxide can bleach the bran. In
one embodiment, the blanched bran is bleached at about 122.degree.
C. at a pressure of about 103.4 kilopascal (kPA) or one (1) atm
(i.e., about 15 psi) for approximately two (2) minutes. In another
variation, the blanched bran is processed at atmospheric pressure
at about 80.degree. C. for about 40 to 60 minutes. The resulting
product is washed thoroughly with water and then filtered. The
bleached wet bran is then dried, such as in a rotating drum, at
about 276 kPA (40 psi). The final product still contains a
sufficient amount of water so as to be utilized in any number of
end products, such as flours, pasta, and so forth.
[0012] Flours comprising this bran exhibit minimal or no enzyme
activity, such as polyphenoloxidase and lipoxygenase activity,
which helps to increase flour stability, particularly as it relates
to rancidity during storage. Another benefit is the white
appearance of composite flours utilizing the bleached bran, as the
"L" value on the Hunter scale can be in excess of 90. The water
absorption of the bleached bran is also increased by up to six
times in comparison to unbleached bran, which provides baking
advantages known in the art. The antioxidant activity in the
bleached bran is also increased by at least 15 to 20%, up to 30-35%
or more, as compared with unbleached bran, which is thought to have
significant health benefits.
[0013] These and other features, aspects and advantages of the
present invention will become better understood with regard to the
following description, appended claims and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The FIGURE is a flow diagram showing a process for bleaching
bran in one embodiment of the present invention.
DETAILED DESCRIPTION OF INVENTION
[0015] In the following detailed description, reference is made to
the accompanying drawings that form a part hereof, and in which is
shown by way of illustration, specific embodiments in which the
invention may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention, and it is to be understood that other embodiments
may be utilized. It is also to be understood that mechanical,
procedural and system changes may be made without departing from
the spirit and scope of the present invention. The following
detailed description is, therefore, not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims and their equivalents.
[0016] Bleached bran, bran products, improved flours fortified with
the bran products herein and methods of preparation are disclosed.
A brief background on wheat and milling is given first, followed by
a description of various methods of producing bleached bran as well
as a description of the resulting bleached bran and bran
products.
[0017] Wheat and Milling Background
[0018] The principle species of wheat are Triticum aestivum or
bread wheat; T. durum which has extra hard kernels used primarily
for macaroni and related pasta products; and T. compactum or club
wheat, which has very soft kernels. Numerous varieties and
cultivars within each species are known.
[0019] In the United States, wheat is classified according to
whether it is hard or soft, white or red, and winter or spring. As
a result there are eight possible designations including: hard
white spring, hard red spring, hard white winter, hard red winter,
soft white spring, soft red spring, soft white winter, and soft red
winter.
[0020] The white or red designation refers to the color of the
wheat kernel. Currently, red wheat is more readily available in the
United States than white wheat. As noted above, red wheat has a
distinctive taste due to the presence of high levels of catechin
and catechin tannins in the bran.
[0021] The hard or soft designation refers to protein strength and
content of the wheat kernel. Tannin content is also known to be
lower in soft wheat than hard wheat.
[0022] The winter or spring designation refers to the growth
habitat of the wheat. Winter wheat is planted in the fall and
harvested in the spring, whereas spring wheat is planted in the
spring and harvested later that same crop year.
[0023] Wheat comprises a major starchy endosperm, a smaller germ or
sprouting section of the seed and a surrounding bran or husk layer.
The "endosperm" is the portion typically referred to, upon milling,
as "flour" and generally makes up about 81-85% of the wheat kernel.
Bran makes up about 11-15% of the kernel, with about one (1) to
3.5% being the germ portion. Bran with or without the germ is
sometimes referred to as "mill feed." Mill feed is a low value
commodity typically used for animal feed.
[0024] Wheat milling is a mechanical method of breaking open the
wheat kernel to remove as much endosperm as possible from the bran
and to grind or reduce the endosperm into flour. The process
substantially separates the major components of the wheat.
Conventional whole wheat flour is produced by grounding "sound"
wheat, i.e., wheat that is substantially free of disease or other
defects, other than durum. The proportion of natural constituents,
other than moisture, remain similar to the intact wheat kernel.
Conventional white flour is produced when most of the bran is also
separated from the endosperm. The germ fraction is usually
separated from the rest of the kernel because its fat content
limits the shelf life of the flour. However, some special purpose
whole grain flours include not only the bran but also the germ
fraction. The yield of flour or endosperm from milling is typically
about 70-80%, with the remaining endosperm still present in the
bran.
[0025] The bran portion can vary considerably in starch and fiber
content. "Light" bran contains 10 to 20% starch and has a fiber
content of about 38 to 48%. "Heavy" bran contains more than 20%, up
to 30% starch, and has a fiber content of between about 25 to 35%.
"Native" bran refers to non-treated bran, i.e., bran that has not
been subjected to any chemical or physical treatment that may
affect its dietary fiber content.
[0026] Wheat color is measured using a colorimeter that uses either
the CIE system or the triestimulus Hunter system. The Hunter value
"L" denotes lightness; the "a" value denotes redness or greenness
and the "b" value yellowness or blueness. A perfect white in the
triestimulus scale has the following values: L=100, a=0 and b=0.
Light bran obtained from winter soft wheat has an approximate
triestimulus value range of L=70-74, a=4-5 and b=18-22. The latter
parameters depend on crop year, location and growing conditions.
Further discussion of the various types of wheats is found in the
Application entitled, "Bleached Grain and Grain Products and
Methods of Preparation," Ser. No. 09/392,699, filed Sep. 9, 2000,
commonly assigned, which is hereby incorporated by reference in its
entirety.
[0027] Flour milling is a low margin commodity operation. As a
result, even small increases in the extraction or mill feed
ingredients can dramatically and disproportionately affect the
profitability of a milling operation.
[0028] Bleached Bran Processes
[0029] The starting material can be any type of wheat, although a
whiter final product is obtained with a whiter starting material,
such as a white wheat. For this reason, white wheat brain is the
preferred starting material. In one embodiment, a soft white wheat
is used as the starting material. In another embodiment, red wheat
is used as the starting material. The wheat is cleaned and milled
in any suitable manner known in the art to produce wheat bran. In
one embodiment, "light" bran from winter soft white wheat is
produced and used in the process. As noted above, milling does not
completely separate the components. As a result, the wheat bran can
contain wheat germ in amounts up to about 20 percent or more, and
the starchy endosperm content can be about 15 to 30%, depending on
type. Generally, higher amounts of starch require more reagents for
removal, thus increasing costs.
[0030] The bran can be any suitable particle size, such as 100
microns or more. Although bran with a smaller particle size can be
used, there is a tendency towards clumping during the process when
the bran particle size is less than about 100 microns. In one
embodiment, the bran is ground prior to the bleaching process to
produce a ground bran having a particle size ranging from about one
(1) to 40 microns. In another embodiment, the bran is ground during
or at the end of the bleaching process. In yet another embodiment,
the bran is not further ground after milling.
[0031] In the embodiment shown in the FIGURE, the bran-bleaching
process 100 begins when unbleached bran 101 is treated 102 with a
chelating agent in order to substantially inactivate or remove
transition metals present in the bran. Such metals include, but are
not limited to, manganese, copper and iron. This is important
because active transition metals can decompose bleaching agents,
such as hydrogen peroxide. Since milling is a commodity process,
small increases in the efficiency of peroxide utilization are
important to obtaining commercially practical methods.
[0032] The chelating agent needs to be present for a sufficient
time and at a sufficiently high temperature in order to minimize
the effect of the transition metals. In one embodiment, the
chelating process is relatively rapid, taking only about one (1) to
15 minutes at a temperature of about 70 to 90.degree. C. In another
embodiment, the process takes less than about one (1) minute. In
yet another embodiment, the process takes between about one (1) to
two (2) minutes to complete at a temperature of about 80.degree.
C.
[0033] Any suitable type of transition metal sequestering
components, i.e., chelating agents, can be used. This includes, but
is not limited to, any orthophosphate, metaphosphate, pyrophosphate
(e.g., tetra sodium pyrophosphate), polyphosphate, 1,2,
diaminoethane, ethylenediaminetetraacedic acid (EDTA), and so
forth. The EDTA can be in the form of calcium EDTA or sodium EDTA.
With the exception of EDTA, the chelating agent can be present in
any suitable concentration, such as between about one (1) to two
(2)%. Generally, higher concentrations of chelating agents remove
more metals, although the upper level is generally limited by good
manufacturing practices. However, since end-product levels of EDTA
are mandated by the U.S. government, EDTA is typically added at
much lower concentrations, such as between about 0.02 to 0.1% (200
to 1000 PPM) in solution with water.
[0034] In one embodiment, the mixture of bran and chelating agent
solution contains about 30% solids and about 70% liquids, by
weight. In a specific embodiment, about 45.4 kg (100 lbs) of bran
is mixed at ambient temperature with a liquid solution of 0.06%
EDTA weighing about 106 kg (233 lbs).
[0035] The treated bran is then washed and rinsed in a first
washing and rinsing step 104 as shown in the FIGURE. In this step,
water is used to partially rinse away the chelate transition metal
that has combined with the chelating agent. Preferably, the water
is soft water with low levels of iron (less than about five (5)
PPM), manganese (less than about 0.02 PPM) and copper (less than
about 0.02 PPM). (Soft water is generally defined as water having
less than about two (2) grains of hardness (calcium and magnesium)
per gallon). In one embodiment, distilled or deionized water is
used. Washing can be accomplished with a suitable amount of
agitation. Rinsing can also be accomplished by any suitable means,
such as with a combination of agitation and spraying. The resulting
washed bran is filtered or dewatered in a first filtering step 106
by any suitable means, such as with centrifugation mechanical
pressing or low-pressure extrusion. The water (waste or recycle)
stream 108 containing the chelating agent can be recycled for use
again in the process or discarded, as desired. In one embodiment,
there is no first washing and rinsing step 104 or first filtration
step 106, although empirically, it is believed that washing also
serves to remove some of the soluble bitter-flavor components.
[0036] The washed bran is then blanched or heat-treated in a
blanching step 110 to inactivate indigenous catalase and peroxidase
enzymatic systems (known as hydroperoxidases) that can otherwise
detrimentally affect the activity of the hydrogen peroxide by
decomposing it into hydrogen and oxygen, which can cause foaming.
Peroxidase is a heat stable indicator enzyme, i.e., once the
peroxidase is inactivated, most other enzymes have also been
inactivated. In one embodiment, the blanching step 108 is performed
at a temperature of about 75 to 85.degree. C. for three (3) to ten
(10) minutes, although the invention is not so limited.
[0037] Residual catalase enzymatic activity can be measured by any
suitable method. In one embodiment, a qualitative method is used in
which a small amount of hydrogen peroxide solution is added and a
visual determination is made as to the formation of bubbles. The
presence of bubbles indicate that oxygen is being evolved, i.e.,
peroxide decomposition. If no bubbles are present, the process
proceeds to the bleaching step 118 described below.
[0038] In one embodiment, about 99% of the enzyme activity is
destroyed in the blanching step 110. In another embodiment,
residual enzyme activity is below about ten (10) CIU/g bran
(catalase international units). CIU refers to the amount of enzyme
in grams that catalyses the decomposition of one (1) micromole of
hydrogen peroxide per minute.
[0039] The washed and blanched bran is then washed in a second
washing and rinsing step 112 as shown in the FIGURE, which can be
followed by a second filtering step 114 that has an associated
waste or recycling stream 116. Preferably, water having a low metal
content is used for the second washing and rinsing step 112. In one
embodiment, soft water, as described above, is used. These steps,
114 and 116, also help to reduce the transition metals that still
may be present. In one embodiment there is no second washing and
rinsing step 112 or second filtering step 114, although again, it
is thought that by providing one or more washing, rinsing and
filtering steps at some point in the process, an added benefit can
be achieved, i.e., removal of certain undesirable soluble bitter
flavor components.
[0040] At this point, between about 40 to 60% of the manganese,
about 50% of the copper, and about 10 to 20% of the iron have been
removed or inactivated. In another embodiment, more than 60% of the
manganese, more than 50% of the copper, more than 20% of the iron,
as well as amounts of other transition metals, have been removed or
inactivated. In a specific embodiment, the resulting material has
less than about six (6) PPM copper, less than about one (1) PPM of
manganese, and less than about ten (10) PPM of iron. As a
consequence of the washing steps 104 and 112, starch is also
removed. In one embodiment, the amount of starch is reduced after
two washing steps from about 19-20% to less than about three (3)%,
by weight.
[0041] The FIGURE further indicates that the present process 100
also essentially comprises a step 118 of bleaching the washed and
blanched bran. In the bleaching step 118, the wet bran is treated
with an oxidant substance, such as hydrogen peroxide, ozone, and/or
peracetic acid in the presence of heat. In one embodiment,
concentrated hydrogen peroxide, such as about six (6) to 40%
hydrogen peroxide, is added to the wet bran. Since concentrated
peroxide is less stable at elevated temperatures, it is preferably
stored as cold liquid at a temperature of about -25 to 5.degree. C.
and then added to the bran at a temperature no higher than room
temperature to avoid increased spontaneous decomposition. More
dilute peroxide can also be used, although such a process is less
efficient.
[0042] The amount of oxidant employed depends upon a variety of
processing parameters and desired level of bleaching. In order to
keep costs down, the minimum amount required to accomplish the
desired level of bleaching is generally used. In one embodiment,
about one (1) to 20 parts of hydrogen peroxide to about 100 parts
of bran (dry basis) is used. In preferred embodiments, the peroxide
utilization rates range from about 1 to 5 parts of hydrogen
peroxide per 100 parts bran.
[0043] Since the pH of hydrogen peroxide is about 6 to 6.7, it does
not react readily with the bran. As a result, it is necessary to
add an alkaline substance, such as sodium hydroxide, potassium
hydroxide or alkaline salts, i.e., sodium carbonate or
polyphosphates, i.e., trisodium phosphate, to increase the initial
pH for the bleaching reaction to about 9 to 9.5 (at room
temperature). The alkaline solution can have a concentration in
excess of about one (1)% up to about ten (10)% or more. In one
embodiment, an aqueous alkaline solution is added in amounts of
about 10 to 15 parts (dry weight) of alkaline material per 100
parts bran. In one embodiment, the bran is treated with the
alkaline and oxidant solution simultaneously. In another
embodiment, the solutions are added sequentially. In yet another
embodiment, no alkaline solution is added. Further optimization of
the process can be achieved by measuring pH changes throughout the
bleaching process. In this way, pH values can be corrected based on
known dependence of pH on temperature.
[0044] The bleaching step 118 is carried out at elevated
temperatures. In one embodiment, the bran is bleached by "heating"
it with a concentrated hydrogen peroxide solution, together with
sodium hydroxide at atmospheric pressure and a temperature of
between about 80-90.degree. C. for about 20 to 60 minutes. In
another embodiment, the bleached bran is subjected to a
high-pressure treatment at a pressure of about 83 to 124 kPA (12 to
18 psi) for about one (1) to five (5) minutes at a temperature of
120-130.degree. C. In a specific embodiment, the bran is bleached
for about two minutes at a pressure of approximately 103.4 kPA (15
psi) and temperature of about 122.degree. C. However, operating the
process at elevated pressure requires a special pressurized vessel
with suitable relief valves to avoid build-up of excess pressure.
In one embodiment, about three (3) to 10% pure hydrogen peroxide
per 100 g of dry gram of dry bran is used. In a specific
embodiment, a mixture of about 10% peroxide solution and one (1)%
alkaline solution is heated together with the bran to about
85.degree. C. for about four (4) to five (5) minutes under
atmospheric conditions. Use of peroxide in the bleaching process is
advantageous in that it degrades into harmless oxygen and water. In
contrast, other types of bleaching techniques such as those that
employ chlorine or benzoyl peroxide, can result in either
undesirable modification of the functional properties of a finished
flour in which the bleached bran is used or undesirably high
concentrations of residual bleaching agents or both.
[0045] The peroxide can be sprayed onto the bran or the bran can be
soaked in a heated bath of peroxide. In one embodiment, a peroxide
stabilizing agent, such as about one (1)% sodium silicate and/or
magnesium sulfate (about 0.1%) is used.
[0046] The bleached mixture can then be subjected to a third
washing and rinsing step 124, followed by a third filtering step
126 with its associated waste or recycling stream 128 shown in FIG.
1. Any suitable type of water can be used to wash and rinse the
bran, such as "soft" water as described above. These latter steps
remove most of the oxidant, although some residual oxidant does
remain. For example, if 10% hydrogen peroxide is used, the residual
after bleaching can be as high as two (2) to three (3) percent. By
providing a washing and rinsing step 124 followed by a filtering
step 126 at this point in the process, it is possible to reduce the
concentration of hydrogen peroxide to less than about 0.5%. It may
be possible to omit the step of washing, rinsing and filtering the
bleached bran in those embodiments where residual hydrogen peroxide
is relatively low, such as less than about one (1)% by weight.
However, higher residual concentrations of hydrogen peroxide can
result in foaming, which can cause a number of problems, such as,
overflow in the system, development of excessively-high pressure,
and so forth. Providing at least one washing step is generally
recommended in the process of the present invention, as it appears
to provide the side benefit of removing certain soluble bitter
flavor components.
[0047] The resulting bleached bran product is treated 130 with a
suitable amount of catalase in order to destroy any remaining
oxidant, such as the hydrogen peroxide. In one embodiment, a
commercial preparation of catalase, such as the one obtained from
the fungi Aspergillus nigers, is used. In a particular embodiment,
between about 0.1 and 0.4% of catalase, by weight, of bran, is
added at an operating temperature of about 55 to 65.degree. C. In
one embodiment, the operating temperature is about 60.degree. C. In
this step, the oxidizing compound can be reduced to less than about
five (5) PPM such that the bleached bran is substantially free of
hydrogen peroxide.
[0048] The catalased bran can be dried 132 at this point or first
treated with ozone 134 as shown in the FIGURE. Treatment with ozone
further whitens the bran, and offers a low cost option to further
treat the bleached bran, if desired. However, in most instances,
the bran is bleached sufficiently for use in most desired
applications. In one embodiment, whiteness of the bleached bran is
improved by treating the bran with 0.1% to two (2)% ozone, by
weight, at pH 4-5. In this embodiment, ozone is generated in an
ozone generator and the bran is treated in an enclosed system or
vessel that keeps the ozone and the low-pH bran in intimate
contact. The consistency of the bran can vary from about 20 to 40%,
depending on water retention. Mixing of the ozone and bran can be
accomplished by any means known in the art, such as by mechanical
means (e.g., tumbling device, rotary device with mixing blades,
etc). In one embodiment, the reaction of ozone and bran is in the
range of about 90 to 95%, e.g., for about 100 g of incoming ozone,
only about ten (10) g of ozone exits the reaction vessel or
system.
[0049] Any suitable type of drying method can be used, such as high
pressure drying, air drying, freeze drying and so forth. The final
product, i.e., (dried) bleached bran 134, is preferably dried
sufficiently so that there are about five (5) to 13 grams of water
per 100 grams of dry bran. In one embodiment, the bran is ground
from a particle size of about 500 microns to a particle size of
less than about 100 microns, such as about 40 to 50 microns. For
embodiments in which EDTA has been used as the chelating agent, the
residual EDTA level in the bleached bran is less than about 100
PPM, and may be much lower. In one embodiment, the treated bran has
a pH of between about six (6) and seven (7), such as about 6.7.
[0050] By treating the bran and germ separately from the rest of
the wheat kernel as described herein, an increase in flour
functionality, particularly baking functionality, is obtained at a
reduced cost. Further, since gluten-forming proteins are not
present in the bran, the bleaching process can occur at higher
temperatures as compared with the whole kernel bleaching as
described in application Ser. No. 09/392,699, noted above. This is
advantageous as bleaching action is facilitated by heat, although
temperatures in excess of 85 to 90.degree. C. are generally not
used since competing reactions, such as browning can begin to occur
at higher temperatures.
[0051] In an alternative embodiment, many of the corresponding
process steps as described in Application (Ser. No. 09/392,699),
can be applied to clean bran, with modifications where appropriate,
due to the differences between utilizing bran versus whole
kernels.
[0052] Those skilled in the art will recognize that the equipment
used in the above-described process can be any conventional
equipment typically utilized for the particular steps. In one
embodiment, a drum dryer operating at about 207 to 345 kPA (30 to
50 psi), such as about 276 kPA (40 psi), is used in the drying step
132. Drum drying provides a quick and economic method for drying
the bran.
[0053] In another embodiment an extruder is used for the bleaching
and catalase addition steps, 118 and 130, respectively, together
with an additional cool-down step. The third washing and rinsing
step 124 as well as the third filtering step 126 is performed
outside of the extruder in this embodiment. Use of an extruder
allows the process to be run in a continuous manner rather than as
a batch process. Further, there is more control over temperature
and pressure, since excess steam can easily be vacuumed off.
[0054] Bleached Bran and Bleached Bran Products
[0055] The resulting bleached bran can vary from a light red to a
yellow color, but is visibly lighter than untreated or unbleached
bran. The final bran color is controlled by a combination of
factors, including, but not limited to, the proportion of oxidant
in the suspension, processing temperature, pH of suspension,
processing pressure and processing time. For example, if the pH and
temperature are too high, too much browning may occur. High
temperatures may also promote the development of off-flavors.
However, if the temperature is too low, the efficiency of the
bleaching process decreases. Use of increased amounts of oxidant
produces a whiter product, but increases the costs as well. There
is also typically an optimum amount of time for the bleaching step
(118) to operate, depending on the pressure conditions as noted
above. Exceeding this time can be detrimental to the dietary fiber
content of the end product.
[0056] Unbleached bran made from white wheat typically has an L
value on the Hunter scale of about 72 to 73. The bleached bran of
the present invention has a higher L value than unbleached native
bran. In one embodiment, the L value is greater than about 75. In
another embodiment, the L value of the bleached bran is between
about 82 and 93. In a particular embodiment, about five (5)%
bleached bran, by weight, having an L value of about 84 is added to
an all-purpose whole wheat flour having an L value of about 93.3.
The resulting composite flour in this instance has an L value of
about 92.4. In other embodiments, the composite flour can have an L
value of between about 82 and 93.
[0057] In comparison, a typical whole wheat flour produced by
conventional methods that contains native or unbleached bran can
have an L value of about 80 to 84. In one embodiment, flour
combined with "drum-dried" bleached bran produced according to one
of the processes of the present invention has an L value of about
85.2. In another embodiment, flour combined with "freeze-dried"
bleached bran produced according to one of the processes of the
present invention has an L value of about 92.5. This compares
favorably with typical all-purpose white flour, which has an L
value of about 93.
[0058] It should be noted that typical white flour is usually
"bleached" using a combination of chlorine, benzoyl peroxide and/or
azodicarbonamide. These oxidants exert their action by oxidizing
the carotenoid pigments that give the yellow color to flour.
However, conventional bleaching processes do not easily oxidize the
components in bran that are responsible for the brown coloring,
e.g., such as lignin and other polyphenols. As such, oxidants such
as chlorine, benzyl peroxide and azodicarbonamide would not be
suitable oxidants in the processes of this invention. Furthermore,
chlorine bleached white flour is undesirable in many countries and
not used. As a result, most baked goods outside the United States
do not have as light a texture, i.e., they are much denser. Ongoing
attempts to improve functionality in these products include use of
unbleached white flour, heat-treated white flour, bleached white
flour and/or mixtures thereof.
[0059] In addition, the anti-oxidant activity of the bleached bran
is increased significantly by the alkaline treatment with hydrogen
peroxide. Specifically, the bran contains an aleurone layer that is
relatively high in phenolic compounds, including ferulic acid.
While not wishing to be bound by the proposed theory, it is
speculated herein that bleaching with oxidants at a high pH, i.e.,
in excess of about 9, causes the lignin portion of the cell wall to
degrade. This degradation causes the ferulic acid (which may be
present in reduced amounts as compared with native bran) to become
more available, i.e., the anti-oxidant activity is increased. In
one embodiment, the antioxidant activity in the bleached bran is
increased by at least 15 to 20%, up to 30-35% or more, as compared
with unbleached bran, depending on bleaching conditions. This
increase in activity occurs even though other antioxidant
components, such as vanillic acids and certain other phenolic
acids, such as caffeic acid, are oxidized and no longer available.
The increase in activity of the ferulic acid, however, is
sufficient to offset this loss, causing the net increase in
anti-oxidant activity as noted above.
[0060] The increased anti-oxidant activity carries over into the
blended product, i.e., such as a composite flour. The activity does
decrease over time, depending on storage conditions, such as
temperature, etc. However, any increased antioxidant activity may
have a beneficial or modulating effect on consumer health. Some
medical studies suggest that whole wheat flour may have a
modulating effect in preventing certain health conditions such as
colon cancer.
[0061] The water absorption of the bleached bran is also improved,
as it is increased by up to six times in comparison to unbleached
bran. Specifically, the bleaching treatment removes part of the
lignocellulosic and hemicellulose material of the cell walls. As a
result, the cell wall structure is disrupted with a concomitant
increase in the water holding capacity of the treated material.
Increased water absorption in the bran improves water absorption in
any composite flour using the bran, which provides increased
consistency and predictability in baked goods, as well as
increasing yield. When added to regular or white flour, the whole
wheat or bleached bran enriched flour also beneficially exhibits
improvements in water absorption. Such increased water absorption
of the flour is a great benefit in baking applications involving
variations in water addition due to equipment or operator
error.
[0062] The moisture content of the bleached bran, on a "fresh" or
"as is" basis, is between about four (4) to 12%. On a dry basis,
the range is about 4.2 to 13.6%.
[0063] The resulting bran also has an improved taste as compared
with untreated bran. The improvement in taste is significant enough
to be noticeable by most consumers. In one embodiment, a consumer
panel rated a bread product containing bleached bran made according
to the present invention, i.e., a "white" whole wheat product, at
least 50% improved in taste as compared with conventional whole
wheat bread. This taste improvement is likely because the flavor
components, including phenolic compounds, such as caffeic acid,
tannins, coumaric acid, and so forth, as well as other polyphenolic
compounds have been sufficiently removed or modified so as to
reduce the associated bitter tastes to acceptable levels. By using
the bleaching processes of the present invention, the bitter flavor
components present in the native bran are reduced, although the
precise percentage of reduction associated with the noticeable
flavor improvement has not yet been determined.
[0064] Although the use of bleached bran may have some detrimental
effects on dough mixing and stability characteristics as compared
with unbleached bran, such effects can be overcome through various
recipe modifications. For example, the mixing process can be
altered by increasing the water added to the dough, such as by
about two (2) to 10 percent and/or increasing the mixing time until
the gluten network is optimized, as is understood by those skilled
in the art. Alternately, or in addition, various additives, such as
vital gluten, emulsifiers, and so forth, can be used to yield baked
products similar in performance to those manufactured with white
wheat.
[0065] The bleached bran product of the present invention is an
intermediate product that can be recombined with flours to produce
an essentially "white" whole wheat flour having a fiber content
comparable to conventional whole wheat flours, i.e., about 10 to
12%. Essentially, the white appearance and flavor identity of the
resulting composite flour is not altered by addition of the
bleached bran. In one embodiment, the flour is a "whole grain"
flour, such that the fiber content is at least about 5.5 g of
dietary fiber per 100 g of flour. The fat content of the composite
flour can vary from about one (1) to three (3)%. However, the fat
content can be adjusted, as needed, such as with the addition of
germ to the fiber. In one embodiment, the fat content of the
composite flour is about two (2)%.
[0066] The flours can be of various types, such as bread flour
(e.g., from hard wheat), all-purpose flour used in a variety of
baked goods, including breads, cakes, muffins, and so forth, pastry
flour (soft wheat) or durum flour. In one embodiment, the bran is
recombined with durum flour, to produce pasta. In this embodiment,
the yellow color of the pasta, considered an attribute of quality,
can also be increased, if desired, by blending it with semolina.
Yellowing can also be controlled by temperature and pH, i.e.,
higher pH produces a more yellow product.
[0067] In one embodiment, the bran is sold as a bran ingredient,
put into dry mixes, added to ready-to-eat cereals, refrigerated
uncooked or bakeable doughs, cooked cereal dough, and so forth. Use
of bran in ready-to-eat cereals increases the dietary fiber content
and the antioxidant activity of the cereal. In one embodiment, the
bran is admixed with sugar, leavening agents (e.g., baking soda,
baking powder, etc.) and salt. In another embodiment, the bran is
combined with soy to produce various soy products, such as
meat-substitute products. In one embodiment, the invention
comprises any of the above named end products.
[0068] In one embodiment, the bran is sold as a bran ingredient,
put into dry mixes, added to ready-to-eat cereals, refrigerated
uncooked or bakeable doughs, cooked cereal dough, and so forth. Use
of bran in ready-to-eat cereals increases the dietary fiber content
and the antioxidant activity of the cereal. In one embodiment, the
bran is admixed with sugar, leavening agents (e.g., baking soda,
baking powder, etc.) and salt. In another embodiment, the bran is
combined with soy to produce various soy products, such as
meat-substitute products. In one embodiment, the invention
comprises any of the above named end products.
[0069] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement that is calculated to achieve the
same purpose may be substituted for the specific embodiments shown.
This application is intended to cover any adaptations or variations
of the invention. It is intended that this invention be limited
only by the following claims, and the full scope of equivalents
thereof.
* * * * *