Note: Descriptions are shown in the official language in which they were submitted.
CA 02559380 2006-09-11
APPLICATION FOR PATENT
INVENTORS: J. KIRK JORDAN
TITLE: READY-TO-EAT DRY FRUIT PRODUCTS AND PROCESS
SPECIFICATION
FIELD
The invention relates to food products and food processing. More specifically,
the invention relates to high fruit content ready-to-eat foods and a process
of
manufacture.
BACKGROUND
Since Adam and Eve, fruit has been universally recognized as a highly
desirable
food. Further, the need for consuming significant quantities of fruit for
nutritional
purposes is well documented. One reason the public does not consume the
recommended
quantities of fresh fruit is spoilage; fruit is highly perishable. Thus, the
fruit is typically
processed to extend its life by canning, freezing or by various evaporative
approaches
such as sun drying (raisins), hot air drying (dried fruit), freeze drying
(blueberries for dry
cereal), frying (sliced bananas), spray drying (fruit powders) and dehydration
to very low
moistures (for dry cereals). Each of these processes has its strengths and
weaknesses:
Sun drying in the desert works well in California apricots but not in
Washington
apples, Michigan cherries or Florida tomatoes;
Hot-air drying makes soft fruit lacking the crispness of fresh fruit and can
yield to
mold and yeast spoilage over time;
Freeze drying is an elegant way to dry fruit, but it is very expensive (an
order of
magnitude greater than fresh fruit weight-for-weight), limiting it to high-
margin products
or small percentages in foods;
Frying imparts fat, offsetting the nutritional value and flavor of fruit;
Spray drying of fruit, limited mostly to pulp-free juices, requires a carrier,
such as
maltodextrin, that limits the fruit content.
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Dehydration to moisture less than 3% depletes volatile flavors and makes a
crispy
but hygroscopic fruit that rapidly absorbs humidity and can become tough and
hard.
The potential for providing other types of fruit products is limited by the
processing difficulties associated with fruit compared to other food products.
For
example, extrusion technology is employed extensively throughout the grain
processing
industry (but not in fruit processing) to cook grain-based and soy foods
because the
process is energy efficient, reliable, and sanitary. Major industry segments
utilizing
extrusion cooking include ready-to-eat cereals, snacks, pet foods, industrial
pre-gelled
flours, and many others.
A cooking extruder is typically a screw machine that accepts free-flowing
grain
meal or flour as in-feed material into a progressively reducing, spiral-screw
cavity. As
the material progresses along the screw or multiple screws of the extruder,
the in-feed
material is hydrated by water injection (for example, from a 10 - 12% in-feed
moisture to
a 15 - 30% dough moisture), and the moistened material is compressed and
heated by
friction to "pressure cook" the extrusion dough with the moisture encapsulated
as steam.
Typically, extrusion in-feed materials must be uniformly free flowing and
finely granular,
both hallmarks of milled grains such as corn meal, wheat and rice flours, etc.
By
contrast, fruit products (i) are not as free flowing, causing stoppage of the
in-feed
material (except in forms too liquid for extrusion cooking), (ii) are often
heterogeneous in
particle size or granulation, and (iii) are hygroscopic when dried. These
characteristics
during the 55-year history of food extrusion processing have virtually
eliminated
extrusion cooking from consideration when processing fruit.
Starches, flours and meals milled from grain have traditionally been used by
those
skilled in the art of extrusion to manipulate texture and density of cereal
foods, such as
ready-to-eat breakfast cereals; snacks, such as corn puffs and onion rings;
pet foods, such
as kibbled dog foods; and many other foods. Starches are long-chain
carbohydrates that,
when gelatinized by extrusion cooking, form films capable of trapping gas (air
and
steam) in thin-walled, honey-comb-like structures, aerating the product
("puffing") and
reducing the density. In traditional practice, fruit powders have been added
in low
percentages (for example, Kellogg's Apple Jacks ) to impart fruit flavor,
color or
marketing sizzle to starch-based puffed foods.
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Some limited attempts to use extrusion technology for fruit have met with
mixed
results. Typically, the fruit content is severely limited, and in some cases
eliminated, so
that the technology is virtually identical to the extrusion cooking of grain
without fruit.
In such cases, the principal ingredients are starches, sugars, gels, gums,
flavors and
colors, with a small percent of dried or powdered fruit.
The technology for producing high fruit content food products by extrusion is
limited. For example, a recent application of extrusion technology to fruit
processing has
copied starch and grain-based extrusion practices associated with the in-feed
material
metered into the extruder. U.S. Pat. No. 6,027,758 describes a traditional use
of starches
that are added as gelling agents to control density and texture of extruded
foods,
including those composed largely of fruit, the apparent focus of this
reference. In a
number of pre-extrusion steps, this reference first drum dries the starting
material, fruit
puree, down to 6% moisture, creating fruit flakes or coarse granules; then
grinds the dried
fruit solids to a powder form intended for homogeneous, steady metering into
the feed
section of an extruder; and finally adds water or other liquids back into the
barrel of the
extruder to facilitate cooking and to prevent mechanical seizure of the
extrusion screw.
The approach applies traditional grain extrusion practices (drying the in-feed
to low
moisture, grinding to uniform granulation, and then rehydrating in the
extrusion barrel) to
a fruit starting material, fruit puree.
In one portion, the reference describes an effect of heat on gelatinization
that is
well known in extrusion technology and in most other food processing
applications in
which carbohydrates are cooked. Starch gelatinization occurs under conditions
combining water with a temperature of at least 160 F, usually with moderate
shear.
When processing below the gelatinization temperature, the starch in the
reference's fruit
product is predictably ungelatinized and the product is dense. As the fruit
product exits
the extruder, the texture is soft and chewy, like the gels of the reference
having a water
activity level of at least 0.58. At higher temperatures, gelatinization of the
starch occurs
by the well-known mechanism, forming a film capable of trapping air and steam.
Further, the reference makes no mention of drying technology or equipment to
achieve
low moisture levels after extrusion, and the reference presents data
describing finished
products in the moisture range of 19-25%, over three times the upper range for
crisp
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starch products. The products of the reference are high or intermediate
moisture gels
similar to those used in popular breakfast bars such as Pop Tarts and the like
or those
with starch content to produce different textures.
A problem with this reference that may preclude it offering a commercially
viable
approach is that, unlike grain flours or meals, the dried-and-ground fruit
powder is
hygroscopic, such that it remains free flowing and non-tacky only for a short
while, and
tends over time to build up on the sidewalls of the handling equipment, most
notably in
the moist feed section of the extruder, inhibiting sanitary and efficient
processing. Such
hygroscopic in-feed materials require specialized handling in a commercial
production
setting and are avoided when possible. To illustrate how industry deals with
the
hygroscopic nature of fruit powders, they are typically packed only in small
quantities in
multilayer laminate film pouches that include aluminum foil or Mylar or some
other
absolute vapor barrier that prevents atmospheric humidity from creating
hygroscopic
caking of the fruit powder prior to use. Thus, the simple application of a
starch and
grain-based extrusion technology to the manufacture of products with a high
fruit
percentage is not readily suitable for commercial production.
In another example of extrusion technology, U.S. Pat. Application No.
20040022901 admixes specially processed crisped rice that has been
manufactured in a
traditional application of extrusion technology for the cooking of rice flour
with a non-
extruded fruit product. In this case, only the grain fraction, i.e., the rice
flour, is extrusion
processed, while the fruit is simply admixed with the extruded crisped rice.
These problems and the attempted solutions using starch and grain-based
extrusion principles illustrate the need for a new product, system, and
process for high
percentage fruit processing with extrusion technology that significantly
departs from
prior teachings. Thus, there remains a need for high-fruit-content foods
produced by
extrusion technology from commercially available fruit ingredients that can be
handled
practically in typical food plant equipment.
SUMMARY OF THE INVENTION
The present disclosure provides ready-to-eat (RTE), shelf-stable processed
foods
composed of up to 100% fruit and the system and process for their manufacture.
The
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product, system, and process use dried fruit in some form as an in-feed
material, having a
higher moisture content than heretofore has been suitable for extruder in-feed
ingredients,
thus retaining at least a portion of the natural juices that contribute to
taste and aromas.
Further, the dried fruit is extruded and dried into crispy, crunchy, chewy, or
hard particles
or pieces high in fruit content than heretofore have been unavailable, and the
products
and process can be independent of starch and grain based prior technology. The
products
of the present disclosure can be eaten as healthy snacks or used as high-fruit-
content
additions in RTE cereals, baking mixes, toppings, and other food products. The
process
provides a high degree of efficiency and reduced costs to make a significant
improvement
in the art.
The disclosure generally provides, in at least one embodiment, a process for
producing a ready-to-eat (RTE) food product, comprising: cutter-milling dried
fruit into
milled pieces smaller than the dried fruit prior to the milling; feeding the
milled dried
fruit pieces as an in-feed material into an extruder; compressing the dried
fruit to generate
heat; and extruding the fruit material to a fruit extrudate.
The disclosure can also provide a process for producing a ready-to-eat (RTE)
food
product, comprising: obtaining an in-feed material comprising dried fruit
grinds and
having a moisture content of 13-30%; feeding the in-feed material into an
extruder;
compressing the dried fruit to generate heat; and extruding the fruit material
to a fruit
extrudate.
The disclosure can further provide a ready-to-eat (RTE) food product,
comprising
a crispy extruded fruit product of 100% fruit using a food extruder and having
a lower
density after extrusion compared to a fruit dough internal to the extruder.
The disclosure
can further provide a ready-to-eat (RTE) food product, comprising an extruded
fruit
product using dried fruit as an in-feed material with a moisture content of 13-
30%
provided to a food processing extruder.
The disclosure also provides, in at least one embodiment, a system for
preparing a
ready-to-eat (RTE) food product, comprising: a dried fruit supply; a cutter
mill coupled
to the dried fruit supply; and a food processing extruder coupled to the
cutter mill.
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BRIEF DESCRIPTION OF THE DRAWINGS
A more particular description, briefly summarized above, may be had by
reference to the embodiments illustrated in the appended drawings, forming
part of the
present specification and described herein. It is to be noted, however, that
the appended
drawings illustrate only some embodiments described herein and are therefore
not to be
considered limiting of the disclosure's scope, in that there can be other
equally effective
embodiments.
Figures 1 A-D illustrates four non-limiting forms of high fruit content food
products that can be produced according to the present disclosure.
Figure 2 is a schematic diagram of an exemplary embodiment of a system to
produce the high fruit content food products.
Figure 2A is a schematic diagram of an alternative of the system shown in
Figure
2.
Figure 3 is a cross-sectional schematic diagram of an exemplary food
processing
extruder.
DETAILED DESCRIPTION
The present disclosure provides a solution to heretofore conflicting interests
of
providing a high percentage of fruit in-feed material for a food extruder
while avoiding
the hygroscopic in-feed fruit materials of prior efforts. The present
disclosure avoids the
hygroscopic challenges by providing a "wetter" in-feed fruit material more
suitable to an
extrusion process, while still providing the fruit materials in a form that is
appropriate to
the extrusion process. The product and process advantageously circumvent the
requirements of drying, grinding to powder, and rehydrating a fruit in-feed
material prior
to extrusion, while alleviating the special handling problems associated with
a
hygroscopic fruit in-feed, typified in dried fruit powder.
The disclosure includes a product, system, and process. More broadly, the
disclosure comprises a family of nutritious fruit foods and a manufacturing
system and
process composed of a series of specific processing steps necessary to make
the fruit
foods. The fruit foods may be composed 100% of a single fruit ingredient; or
the fruit
foods may be composed 100% of a combination of several fruit ingredients; or
the fruit
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CA 02559380 2006-09-11
foods may be composed of fruit ingredients co-processed with other non-fruit
food
ingredients, such that fruit ingredients comprise at least one-third (33%) by
weight of all
the ingredients, advantageously at least 75%, and more advantageously at least
90%. The
manufacturing process is a series of sequential steps in which dried fruit or
dried fruit
with other ingredients are mixed, homogenized, extruded, dried, sized, and
packaged.
The disclosure includes (1) a new category of fruit foods; and (2) a practical
system and method of manufacturing these processed fruit foods. The disclosure
provides, first, a new category of unique food products composed mostly of
fruit (up to
100%) and other food ingredients and fashioned in various dry or semi-moist
physical
forms; and second, a system and process to manufacture the various fruit
products by
orderly execution of the processing steps that transform the dried fruit and
other starting
ingredients into the finished processed fruit food. The products of the
invention can be
variously described as a crispy, crunchy, chewy or hard RTE, shelf-stable
foods
composed totally or mostly of fruit. The process of the invention can be
described as a
series of sequential processing events, including a steady presentation of the
homogeneous ingredient(s) to a high pressure/high temperature extrusion
processor,
followed by drying with heat, milling and sifting for sizing, and packaging in
a vapor
barrier to prevent the hygroscopic absorption of moisture from the ambient air
into the
food product.
For the purpose of the present disclosure, the following terms and their
meanings
can assist in understanding the disclosure. The term "product moisture"
includes the
weight of water in the product relative to the weight of dry material,
expressed as a
percent. The moisture content is usually determined by weighing a sample, then
desiccating it under vacuum and heat, and re-weighing the sample to ascertain
the
moisture loss in accordance with a standardized procedure by the Association
of Official
Analytical Chemist (AOAC) 934.06 for dried fruit. The term "water activity"
("Aw") is
related directly but non-linearly to moisture and can be practically thought
of as the
relative humidity inside a product. "Aw" measures the vapor pressure of the
moisture in
a hygroscopic material at a specific temperature, expressed as follows:
Aw = p/ps and % humidity = 100 (Aw) where:
p = the partial pressure of water vapor of the product, and
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ps = the partial pressure (saturation) of water vapor of pure water.
In foods, water activity is most often used as an expression of the moisture
available to
support microbiological growth. Most bacteria require an Aw of at least 0.91
and most
molds require at least 0.80, although a few osmophilic microorganisms can live
as low as
0.60.
The term "hygroscopic" characterizes dry materials that tend to absorb water,
usually from air. Desiccants are hygroscopic materials intended to absorb
moisture from
a product in a confined space, thus keeping the product dry while raising the
moisture
level of the desiccant. Foods that are hygroscopic tend to absorb humidity
from air or to
redistribute moisture in heterogeneous foods, e.g., sun-dried raisins
transferring moisture
to hygroscopic bran flakes, resulting in hard raisins and stale bran flakes.
A "gel" is a semi-rigid solid mass, a colloidal suspension composed of a
liquid
phase and a solid phase in which the liquid molecules have been absorbed in
the solid
molecules.
Figures IA-D illustrate four non-limiting forms of high-fruit-content food
products that can be produced according to the present disclosure and will be
described in
conjunction with each other. The shapes, textures, and physical properties can
vary and
the following is merely exemplary. For example, a fruit product I OA can be
formed of
the present invention as a chip or flake with a crunchy or crispy texture.
Heretofore, a
disk or slice of fruit in this shape would be leathery and hard to chew,
giving less
pleasure and motivation to ingest. A second exemplary fruit product 10B can be
a
granular food product of various granulations: from fine granules, such as a
granular
sweetener composed of sweet fruit, such as Fuji apples, sprinkled on other
foods; to
larger granules, such as a breakfast nuggets served in a bowl with milk,
mimicking the
appearance and texture of Post brand Grape-Nuts cereal (which, despite its
name, is
composed of barley and not grapes); to larger amorphous lumps, as would be
suitable for
a hand snack or finger food. The texture can vary and in general the high
fruit product
can be crispy or crunchy to add to its appeal as a food, although in some
embodiments it
could be soft and chewy or hard like candy. The term "crispy" is exemplified
by
Cheetos cheese puffs, potato chips, and crisped rice, and defined as firm but
easily
broken or crumbled. For the purposes herein, the term "crunchy" is exemplified
by foods
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such as Post brand Grape-Nuts cereal, granola clusters, and croutons. The
term "hard"
is exemplified by hard candy, such as LifeSavers candies, peanut brittle, and
crushed
ice. The term "chewy" is exemplified by taffy candy, Nabisco Fig Newtons E,
and
Tootsie Roll brand chocolate candy.
A third exemplary fruit product 10C could be a puffed fruit product similar to
shape and size of Cheetos cheese puffs. The shape could vary from spherical to
cylindrical. A fourth exemplary fruit product 10D could be a donut-shaped
product of
various sizes from a dime-size or smaller to a larger donut-sized disk or
other sizes as
could be suitable to the marketplace.
Fruit products of the disclosure that are composed of 100% fruit may be
formulated from a single fruit (e.g., dried apple); or from blends combining a
single fruit
with a fruit fraction of that same fruit (e.g., dried apple and dried apple
pulp); or from one
or more fruits combined with fractions of a different fruit (e.g., dried
apricot and dried
apple and optionally combined with a dried fruit pulp). In addition to
formulations
processed entirely from dried fruit pieces (e.g., dried apple pieces) or
entirely from dried
fruit grinds (e.g., dried apple grinds), or from a combination of dried fruit
pieces and
dried fruit grinds, other formulations that include edible fruit fractions
(e.g., dried apple
pulp or dried apple juice powder or dried apple puree powder) may be created
to make a
processed food product that is 100% fruit. These combinations of dried fruits
and dried
fruit fractions may be incorporated into a formulation to achieve certain
functional
properties, such as enhanced fruit fiber content, enhanced flavor or color
levels, cost
containment, and so forth. In at least one embodiment, a fruit food product
can be made
from 100% fruit composed of a single dried fruit or of blends of various dried
fruits or of
blends of dried fruits and dried fruit fractions in their various physical
forms.
The term "dried fruit grinds" as a subset of dried fruit is intended to
include the
homogenized fruit tissue from dried fruit, with or without the fruit peel and
tiny seeds
depending on the fruit, and minus the stems, pits and large seeds to the
extent
technologically possible. The term "dried fruit pulp" is intended to indicate
the fruit
fraction remaining after fruit juice is pressed from the fruit, and the
residual fruit solids
are dried to a powder with a moisture content of approximately 5%. The term
"dried fruit
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powder" is intended to include the dried fruit solids derived from fruit puree
or fruit juice
ground and sifted to a fine powder with moisture less than 3.5%.
Other fruit products of the invention may contain less than 100% fruit, i.e.,
formulations composed of (1) dried fruit or combinations of various kinds of
dried fruit
or dried fruit fractions in their various physical forms as the primary in-
feed ingredient(s),
and of (2) one or more non-fruit ingredients. The various non-fruit
ingredients may be
dry blended with the dried fruit prior to extrusion and processed as a
homogeneous fruit-
and-non-fruit mixture to achieve certain product characteristics, such as
sweetness levels,
textural effects, color intensities, aromas, and other features. A partial
list_of these
functional non-fruit ingredients includes: dry or liquid sweeteners (e.g.,
fine granular
sugar), texture stabilizers (e.g., wheat starch or rice flour), nutrition
enhancers (e.g.,
proteins, vitamins, minerals), colors, flavors, and other food-grade
ingredients and food
additives. For example, a fruit food product can be composed of (1) fruit
and/or fruit
fractions in sufficient quantity that the sum of the fruit components equals
at least one-
third of the fruit product.
In this disclosure, one starting material is food-grade dried pieces of intact
fruit
tissue known as "dried fruit" or "evaporated fruit", such as, for example,
dried apple or
dried apricot. Dried fruit is an industrial and retail ingredient readily
available in various
physical forms and specifications in the world market place. The fruit is
dried after
harvest to a moisture level consistent with preservation for at least a year
when stored in a
dry warehouse at temperate or cool storage temperatures. The actual moisture
level in
dried fruit depends on the individual fruit, the level of soluble solids in
the fruit, the
presence or absence of added chemical or osmotic preservatives, and other
factors.
However, in general, dried fruit has a moisture range between 13 and 30%. Post-
harvest
fruit dehydration functions as a physical preservative to strongly inhibit
further ripening
and degradative growth of microorganisms, especially yeasts and molds. In the
market
place, dried fruit is variously offered with or without sulfur dioxide (SO2),
a food additive
that assures flavor and color retention in the dried fruit and that is largely
dissipated by
the processing of this invention. Such dissipation through the processing of
this
disclosure is important because some people can experience allergic
respiratory distress
when exposed to sulfur dioxide levels above their symptomatic threshold. In
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CA 02559380 2006-09-11
manufacture of these processed products made from up to 100% fruit, the dried
fruit is
fed directly into the extrusion processor, either into the feed section of the
extruder or
into a conditioning cylinder before the feed section or into other upstream
equipment. In
contrast to the prior art, the use of dried fruit eliminates (1) the required
extra steps of
drying, grinding and sifting of drum-dried fruit puree before extrusion
processing, (2) the
attendant loss of volatile flavor components associated with drying and
grinding, (3) the
sanitation and equipment processing challenges associated with handling a
highly
hygroscopic food ingredient, and (4) the rehydration of the dried puree inside
the extruder
with added water or other liquids not native to the original fruit.
In at least one embodiment, the dried fruit is finely chopped and divided into
a
generally continuous homogeneous in-feed material. This step is accomplished
by
passing the dried fruit through an UrschelTM mill, grinder having a cutter, or
other cutter
mill. A "cutter mill" and the contextual term "mill" (and corresponding method
"cutter-
milling") is defined broadly to include any device that can shear and degrade
the cellular
structure of the dried fruit pieces into finely divided fruit, thus helping
insure the
extrusion of a homogeneous, fine in-feed material and resulting in a
homogeneous output
material (extrudate) at the extrusion die. Because some extruders in the
extrusion process
are inefficient mills, the insertion of a cutter mill to create a homogenized,
milled dried
fruit as the in-feed material is preferable to feeding evaporated fruit dices
or similar small
pieces of intact fruit tissue into the extruder in-feed. An additional
advantage is that dried
fruit of any size or configuration (whole, sliced, or diced) may be used. Use
of a cutter
mill to feed the extruder yields a homogeneous extrudate which, when dried to
a very low
moisture, makes a crispy, crunchy, or hard piece, lump or granule of fruit. By
contrast,
the direct extrusion without comminution of dried fruit pieces, such as dried
fruit dices
with their cellular matrix intact, can lead to a heterogeneous extrudate
containing intact
pieces of dried fruit buried in a matrix of partially ground fruit. Such
intact pieces of
fruit, when dried, produce a tough, resilient or hard piece of fruit having a
texture
significantly different from that of the crispy, crunchy, or hard fruit matrix
of the present
disclosure.
Alternatively, it is possible to configure the tooling, such as screws of an
extruder
with a cutting section to function as a cutter mill, to homogenize the soft
structure of
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dried fruit pieces to create a substantially homogeneous fruit mass inside the
initial
segments of a long barrel extruder. The cutting section would generally be
located in the
early stages or barrels of the extruder between the feed screw and the
extrusion stages.
Thus, the cutter mill becomes integral to the extruder. Such an extruder
configuration
allows feeding dried fruit dices or pieces directly into a feed throat of the
extruder
without first passing the dried fruit pieces through a comminuting step prior
to entering
the extruder. The comminuted fruit mass thus created in the initial extrusion
barrels
proceeds though the pressurizing and heating segments of the extruder in an
extrusion
process and through an extrusion die, extruding a puffed or slightly expanded
porous fruit
product substantially free of intact, distinct, dried-fruit fragments.
Another practical starting material of the invention is industrial dried fruit
grinds.
In commercially available fruit, such as apple, grinds are manufactured by (1)
cleaning,
peeling and coring the fruit; (2) drying fruit pieces to a moisture adequately
low
(approximately 24% moisture for apples) to preserve the fruit in a shelf-
stable mode at
cool temperatures; and (3) extruding the dehydrated pieces through an orifice
(die) in a
machine similar to a meat grinder, disrupting the cellular structure of the
fruit and
creating a somewhat sticky homogeneous fruit pieces. In some fruit grinds such
as
apricot, the fruit is pitted but not peeled. In other fruit grinds such as
raisin, the skin and
tiny seeds can be included. Commercial fruit grinds take numerous physical
forms,
including spaghetti-like strings or fruit paste or fruit paste with finely
divided particles
(e.g., skin or tiny seeds). In this disclosure, extrusion of 100% fruit grinds
results in a
uniform, homogenized extrudate that is then dried to a crispy or crunchy RTE
fruit food,
such as an amorphous lump fruit snack; or fruit granules for admixing into dry
foods,
such as RTE cereals or granola bars; or fine fruit granules or powders used as
fruit
sprinkle toppings or fruit flavorings. Utilizing fruit grinds as the starting
material avoids:
(1) the requirement in prior art of extra drying, grinding, sifting and
rehydration of fruit
puree to extrude 100% fruit foods, and (2) the requirement to pass the dried
fruit starting
material through any milling step prior to extrusion.
Still another practical starting material is fruit infused with sweetener,
such as
sucrose or corn syrups. Some fruits, such as blueberries or cranberries, are
available in
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the market place in the infused form rather than or in addition to the
uninfused, dried fruit
form.
In some cases, the use of dried pieces of intact fruit tissue (dried fruit) is
preferable to fruit grinds as a starting material because fruit pieces are
free flowing and
are less likely to stick in production equipment. However, dried fruit pieces,
with their
cellular structure largely intact, require additional comminuting before
extrusion to
disrupt the cellular structure and to minimize the quantity of individual
fruit particles that
tend to survive the extrusion process and to exit the die as intact dried
fruit particles
imbedded in the extrudate matrix. The insertion of a mill into the process
line to
comminute the dried fruit into finely divided fruit pieces ahead of the
extrusion step
allows the direct use of dried fruit as a starting ingredient. Especially in
the case of fruit
products composed 100% of fruit tissue, the advantage of finely divided dried
fruit over
dried fruit grinds is that the former is free flowing and easier to handle in
industrial
equipment.
In other cases in which the dried fruit is admixed with other dried fruit
ingredients, e.g., apple pieces mixed with apple pulp, the use of apple grinds
may be
preferable because the grinds become coated with the other dry ingredients in
the
blending step, making the grinds free flowing in the feeding step while
eliminating the
need for direct cutter milling.
Figure 2 is a schematic diagram of an exemplary embodiment of a system and
process to produce the high fruit content food products. Figure 2A is a
schematic
diagram of an alternative of the system shown in Figure 2 and will be
described in
conjunction with Figure 2. As described herein, different pieces of equipment
can be
used depending on the starting point of the materials and the desired shape of
the finished
product. Thus, the exemplary embodiment can be varied and the illustration is
not
intended to limit alternatives.
The exemplary system 2 represents a production line and includes a fruit
supply,
an optional non-fruit supply, a mixer depending on the materials, a cutter
mill depending
on the type of fruit supplied, a surge hopper, an extruder, a drier, a roller
mill depending
on the shape of the product desired, a sifter depending on the product
desired, and an
optional packer. Each piece of equipment will be described below.
13
CA 02559380 2006-09-11
The fruit supply 12 can include a supply of fruit products as described
herein. In
at least one embodiment the fruit supply can include dried fruit pieces in
various sizes. In
some embodiments, the fruit supply 12 can represent a plurality of fruit
supplies of
different fruit, different sized and shaped pieces, and different types of
fruit forms such as
fruit grinds and fruit fiber.
The fruit supply 12 can be coupled to a mixer 16. The term "coupled,"
"coupling," and like terms are used broadly herein and can include any method
or device
for communicating, attaching, joining, inserting therein, forming thereon or
therein,
securing, binding, bonding, fastening, or otherwise associating, for example,
mechanically, magnetically, electrically, chemically, directly or indirectly
with
intermediate elements, one or more pieces of members together and can further
include
integrally forming one functional member with another.
The mixer 16 can be useful if other materials besides a single fruit source
are to
be used in producing the product. Alternatively, a fruit source that does not
need mixer
can bypass the mixer and perhaps the surge hopper 18, and proceed to the mill
20,
described below. Such other materials can be different fruits or fruit forms,
such as
grinds or fiber, from the fruit supply 12, or non-fruit materials from a non-
fruit supply 14.
The mixer 16 can be used to blend the in-feed material to provide a relatively
homogeneous mixture in those embodiments where multiple in-feed products
(products
with a plurality of fruits or products with fruit and non-fruit portions) are
used. Without
limitation, any general food-grade ribbon blender, paddle mixer, V-blender or
other
design producing a homogeneous mixture may be employed. In some embodiments,
the
non-fruit supply 14 can supply materials to be blended with the fruit in the
mixer 16. As
discussed herein, such non-fruit materials can assist in achieving certain
product
characteristics, such as sweetness levels, textural effects, color
intensities, and so forth.
In at least one embodiment, it can be advantageous to include a surge hopper
18
that can be coupled to the mixer 16, if used. The surge hopper 18 can receive
the
materials from the mixer to provide a buffer in the production line, so that
the mill, if
used, and the extruder can receive a substantially continuous flow of
material.
The surge hopper 18 can be coupled to the mill 20. In at least one embodiment,
the mill 20 can include an UrschelTM mill or similar cutter mill to degrade
the cellular
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CA 02559380 2006-09-11
structure of the dried fruit pieces into finely divided fruit, thus insuring
the extrusion of a
homogeneous, fine in-feed material. While the term "mill" is broadly used in
the food
processing industry and generally includes several types of processing, the
type of mill
used for processing the in-feed dried fruit in this disclosure is used more
distinctly to
refer to a cutter mill, as opposed to a grinder or roller mill. A grinder mill
used in prior
art to mill grain into flour or to reduce very low moisture fruit flakes and
granules down
to fruit powder would not be suitable for the relatively high moisture content
of the dried
fruit. The use of a cutter mill for the food processing of fruit has not been
provided prior
to the present invention to prepare the in-feed material for extruder
processing. Urschel
mills as exemplary cutter mills are typically used to slice, dice, or
homogenize fresh fruit
and vegetables, cheeses, meats, nuts and peanuts, and other soft or wet foods
that tend to
stick to and foul roller, attrition or hammer mills. The various cutting heads
of a cutter
mill can be selected to produce different size pieces, as desired. The
insertion of a cutter
mill to create a homogenized, milled dried fruit as the in-feed material is
preferable to
feeding evaporated fruit dices or similar small pieces of intact fruit tissue
into the
extruder in-feed because in general extruders are designed to receive rather
than to
generate homogeneous material for processing. An additional advantage is that
dried
fruit of any customary size or configuration (whole, sliced, or diced) can be
used to feed
the mill. Use of a cutter mill to feed the extruder generally yields a
substantially
homogeneous extrudate.
Alternatively, if a fruit supply, such as fruit grinds, does not require
milling, then
the mill can be bypassed or removed from the system and a fruit supply 12A can
provide
the fruit to the mixer, if other materials are to be added to the fruit as in-
feed material to
the extruder. Further, if the fruit supply does not need milling, such as
fruit grinds, and is
otherwise a homogeneous supply, for example, composed of a single fruit, then
the mill
and mixer can be bypassed or removed from the system and a fruit supply 12B
can
provide the fruit for the in-feed material to the extruder.
The present disclosure starkly contrasts to traditional extrusion processing.
To
extrude fruit, traditional thinking starts with fruit powder fed into the
extruder to create a
homogeneous dough. So technologists have desiccated fruit puree to a powder by
various drying, milling and sifting technologies, and then added water into
the extruder to
CA 02559380 2006-09-11
create a homogeneous dough. The typical approach has adopted traditional
extrusion
technology in which field grain, e.g., corn, is dried, ground into meal,
sifted, and hydrated
into a dough inside the extruder. Traditional food extruders have been fed by
finely
granulated dry flowable starch sources, such as grain flours and meals. The
typical
approach has adopted such grain-based technology to fruit extrusions by
supplying dry
fruit powder to an extruder, not large pieces of wet or intermediate moisture
ingredients
existent in "dried fruits" having a moisture content greater than the fruit
powders. This
typical approach applied to fruit has been followed even though (1) fruit
desiccation to
approximately 5% moisture or less as in-feed fruit powder material before
extrusion
dissipates volatile flavors and aromas and wastes energy; and (2) fruit
powders are so
hygroscopic that their use as food ingredients is problematic and impractical
under
typical extrusion processing conditions. Thus, without the current disclosure,
innovation
in fruit extrusion continues to be anchored in the traditional grain-based
approach of
drying, grinding to a powder, sifting, supplying to the extruder, and re-
hydrating in the
extruder. Perhaps the use of dried fruit pieces has been avoided because the
extrusion
process is generally very ineffective at milling, inefficient at reducing
fruit pieces to a
homogenous fruit dough, and the resulting heterogeneous extrudate dries to an
unpalatable leathery texture similar to that of fruit pieces desiccated to 5%
moisture or
less without the texturizing benefits of extrusion processing.
In at least one embodiment, this disclosure provides for the relatively "wet"
slicing and milling of dried fruit pieces. Cutter-milling is important to
break down the
fruit pulp to allow formation of a homogeneous extrusion fruit dough. Dried
fruit pieces
of any size may be metered into the cutter mill equipped with an appropriate
fine cutting
head, then continuously discharged into the processing line or directly into
the feed
section of an extruder. Compared to fruit powder, dried fruit pieces receive
less drying
and milling, thus conserving aroma and flavor volatiles. Dried fruit is easy
to handle in
processing equipment and is only slightly hygroscopic because its moisture
content (13 -
30%) is much higher than fruit powder at 5% or less.
The mill 20 can be coupled to the extruder 22 to provide the materials
therefrom.
The extruder 22 is generally a continuous high-temperature/short-time pressure
cooker in
which, in the presence of moisture, an Archimedes screw mixes and compresses
raw
16
CA 02559380 2006-09-11
material into a fruit dough and generates frictional heat, shear, and pressure
to cook the
fruit dough. The extruder then can extrude the fruit dough through a
restrictive orifice
back to atmospheric pressure to form an extrudate with a porous structure.
As described above, the cutter mill 20 and extruder 22 can be combined into an
integrated unit 21, such as a long barrel extruder. The cutting section would
generally be
located in the early barrels of the extruder between the feed screw and the
extrusion
stages. Such an extruder configuration allows feeding dried fruit dices or
pieces directly
into a feed throat of the extruder without first passing the dried fruit
pieces through a
comminuting step prior to entering the extruder. The later stages of the
extruder are used
in the extrusion process to extrude the fruit mass as described herein.
Referring briefly to Figure 3, a cross-sectional schematic diagram of an
exemplary food processing extruder is shown. An extruder 14 can be a single
screw
extruder (as illustrated) or a multiple (such as twin) screw extruder.
Depending on the
application, size, shape, and amount, each type has advantages and
disadvantages.
Generally, twin-screw technology is more versatile, whereas single screw
technology is
less expensive. The extruder 14 can have a variable number of sections 33
(also known
as "barrels" or "heads") through which an extruder screw 32 rotates. The
extruder screw
32 generally has various diameters, pitch, flight depth, and other design
criteria to process
the in-feed material from the inlet through the outlet. Regardless of the
number of heads,
in general, the extruder 14 includes an inlet 28 in which the material to be
processed is
loaded. A first barrel section is termed a "feed" section 34 that accepts the
in-feed
material into the processing portion of the extruder in conjunction with the
extruder
screw. The feed section is generally at ambient temperature and pressure. The
next
section is termed a transition section 36 because the granular or particulate
in-feed
material is converted to a homogeneous molten fruit dough. The in-feed
material is
compressed through a change in the screw pitch, diameter, or other design
criteria. The
transition section 36 operates with an elevated temperature of approximately
30-70 C
(85 - 160 F). A next section is termed a cooking section 38 that creates
frictional heat,
shear, and compression elevating the material to approximately 70 - 130 C
(160 - 260
F). The material is extruded as an extrudate through an outlet 40 and
generally through a
die 42 to shape the extrudate and cut through a cutter 44 into desired pieces.
17
CA 02559380 2006-09-11
To maintain a constant cook, food extruders operate under steady-state
conditions,
with the quantity of raw material input equal to the product output at any
given moment.
Consequently, smooth flowability of the raw material, that is, a steady in-
feed rate into
the grooves of the extruder feed screw, is required for optimum performance.
Hygroscopic in-feed materials can create stoppages and inhibit uniform
flowability by
building up on equipment surfaces, creating breakaway, high-moisture lumps
that
destabilize or eventually blind the extrusion in-feed.
The solution offered by the present disclosure provides a high percentage of
fruit
in-feed material while avoiding the hygroscopic in-feed fruit materials of
prior efforts.
The present disclosure provides a "wetter" in-feed fruit material more
suitable for fruit
dough formation in an extruder process, while still providing the fruit
materials in a form
that is appropriate to the extrusion process.
The process offers the following advantages over current technology:
1. 100% fruit or fruit blended with other ingredients may be fed directly into
the extruder, greatly simplifying the current technology that requires (a)
drying of fruit
puree on a flaking roll to 5% moisture level or less (b) grinding and sifting
the resulting
dried fruit flakes or pieces, reducing them to powder form, and (c) re-
hydrating the
powder in the extruder.
2. Directly feeding the dried fruit into the extruder via an Urschel mill or
the
like, or directly feeding fruit grinds greatly simplifies the handling of the
fruit because the
dried fruit is only slightly hygroscopic, whereas the fruit powder (5%
moisture or less) is
very hygroscopic, necessitating dehumidified plant air or limited exposure to
atmospheric
air or special equipment to deal with chronic caking, sloughing and blockage
problems
associated with hygroscopic ingredients.
3. Dried fruit pieces retain much more of the native fruit juice (13 to 30%)
with its flavor and aroma components than dried fruit powder (5%). For
processing,
dried fruit powder must be re-hydrated in the extruder with water or some
other liquid,
whereas dried fruit can be extrusion processed using the native fruit juice
alone.
Alternatively, as shown in Figure 2A, the non-fruit supply 14 can provide the
non-fruit ingredients, such as flour and sugar, to the mixer 16 for blending.
The blended
materials can be stored in the surge hopper 18, and metered into an extruder
pre-
18
CA 02559380 2006-09-11
conditioner of the extruder 22. Still further, the non-fruit supply can be
directly supplied
to the surge hopper 18, for example, if the mixer 16 was unnecessary, or can
be fed even
directly to the extruder 22. Similarly, the fruit can be fed into a surge
hopper 18A, then
to the mill 20, and to the extruder 22 from the mill 20.
Returning to Figure 2, after the extruder 22, the extrudate can be dried to a
selected level in a drier 24, such as a hot-air drier, as a prefinished food
product. The
product exiting the drier can have a moisture content of less than about 10%
and
advantageously less than about 6%. The water activity can be less than about
0.55 and
advantageously less than about 0.3.
In at least one embodiment, the extrudate is hot from the extrusion die and
can be
distributed evenly onto the belt of a hot-air drier. Another drier that can be
used is a
fluidized bed drier that passes a gas (usually air) through a product layer
under controlled
velocity conditions to create a fluidized state of the product and increase
exposure to the
gas. Yet another drier can be use of a freeze drier with an increased
efficiency over
conventional freeze-drying of fruit due to the expanded nature and low density
of the
herein disclosed food product. The product can be discharged from the drier at
the
desired moisture by varying the temperature and residence time in the drier.
Generally,
the product texture will be specified to be hard (like hard candy) or crunchy
(like Post
brand Grape-Nuts cereal) or crispy (like corn flakes) or chewy (like taffy),
in contrast to
higher moisture gelled fruit products that are not dried.
For some products, a mill 26, such as a roller mill or other appropriate
milling
technology (generally not a cutter mill that shears the products before the
extrusion
process as referenced above), can be used after the drier to reduce the
particle size of the
extrudate to the desired range. A sifter 28 can be used to screen the
extrudate to certain
sizes for ultimate packaging. A packer 30 can package the product in a variety
of soft
and hard containers, including weather resistant packaging and can further
include
vacuum or controlled atmosphere processing.
The following process is described as at least an exemplary, non-limiting
embodiment, as the disclosure provides for multiple variations and others
known to those
with ordinary skill in the art, given the disclosure herein: An in-feed
material of 100%
fruit from single ingredient, dried fruit pieces, is fed into an UrschelTM
brand mill fitted
19
CA 02559380 2006-09-11
with a cutting head fine enough to reduce the dried fruit pieces to comminuted
dried fruit
pieces, thereby partially disrupting the physical structure of the fruit. The
feed rate into
the mill is set at a constant speed equal to the output rate of the production
line. The mill
discharges comminuted dried fruit pieces directly into the feed section of the
extrusion
processor, which is operated under conditions to create a slight aeration or
puffing of the
extrudate. The extrudate is continuously fed into a drier, where moisture is
reduced as
desired below a water activity less than 0.55, and the finished product is
sized and
packaged.
Alternatively, to manufacture a product of the invention containing 100% fruit
composed of more than one dried fruit ingredient, a blending step is inserted
before the
cutter mill to create a uniform in-feed.
Further, to manufacture a product of the invention containing less than 100%
fruit, the ingredients can be blended prior to the extrusion in-feed step.
Dried fruit grinds
can be used for blends in which the grinds represent 80% or more of the
blended
formulation because ingredient stratification or segregation by size (density)
is not
problematic in this range. With dried fruit concentrations between one-third
and 80%,
blending techniques well known in the art are employed to maintain a
homogeneous
mixture. Although the percentage of dried fruit can vary in the finished
product
depending on the desired market, it is contemplated that the product will
contain at least
one-third fruit, generally at least 40%, advantageously at least 75%, and in
some
embodiments 100% fruit.
The fruit food product is extruded at elevated pressures (generally 100 to
1500
pounds per square inch at the die) and elevated temperatures (generally from
70 to 130
C (160 - 260 F) at the die) to lower the product density (i.e., to puff the
extrudate) below
that of the fruit dough material inside the extruder and to greatly increase
the total
product surface area (both internally and externally) by creating a porous,
fine, honey-
comb-like internal structure and an expanded overall product volume. This
honey-comb
structure accomplishes several physical functions, including: (1) facilitating
the drying of
the extrudate by greatly expanding the product surface area internally and
externally,
allowing increased hot air contact with the product; (2) creating a honey-comb-
like
CA 02559380 2006-09-11
structure having a multitude of thin walls, making the texture of the dried
product lighter
and crispier to the bite; (3) increasing the product volume for heightened
visual impact.
In formulations with less than 100% fruit in which starches or flours are
admixed
with fruit prior to extrusion, the extrusion processor cooks (gelatinizes) the
raw starches,
creating a carbohydrate film (matrix) that facilitates the entrapment of steam
and air
inside the extrudate, thus facilitating greater volume expansion and ultimate
textural
tenderness of the dried finished fruit product.
An additional advantage of extrusion processing of the input food ingredients
(the
dried fruit and the non-fruit ingredients) at these elevated pressures and
temperatures is
high temperature/short time (HTST) pasteurization, which occurs as the fruit
food
traverses the extruder and exits the die, greatly reducing the microbiologic
flora to very
low levels for enhanced food safety and storage stability. This food safety
margin is
especially significant in RTE foods that are consumed directly without an
intervening
cooking step at the consumer level.
EXAMPLES
The technology disclosed herein is applicable to many different categories of
existing or potential fruit products. In general, any application in which a
crunchy or
crispy fruit texture and flavor are desirable, either standing alone or as an
incorporated
ingredient, can be manufactured with the disclosed technology. Some typical
broad
applications include: confectionary, ready-to-eat dry breakfast foods, snacks,
bakery
applications, sprinkle toppings, and others. Without limitation, below are
some
examples.
Example 1: Crunchy Apple Candy, 100% apple
Commercially available sweet-apple dices (approximately 29% natural sugars,
Fuji variety) were fed at a continuous rate into an Urschel 1700 Comitrol mill
equipped
with a fine M-style cutting head to reduce the dices to finely divided apple
pulp pieces.
These flowed down a chute directly into the feed throat of a 5-head single
screw extruder
equipped with high-pressure screws, a pressure plate and restrictive die
openings to
21
CA 02559380 2006-09-11
increase the extrusion backpressure. No liquids were added; the native apple
juice in the
dried apples having 26% residual moisture provided adequate moisture for
extrusion
processing. From in-feed to exit die, the temperatures in the extrusion heads
steadily
increased from room temperature in the feed section to 130 C (266 F) at the
die. The
extrudate was sliced at the die face into amorphous lumps approximately 1 cm
diameter
and was conveyed to a forced-air, continuous-tray drier at 82 C (180 F) for
60 min.
Drying to 3% moisture concentrated the native fruit sugars to approximately
75% sucrose
equivalent, creating crunchy candy pieces with a natural, intensely sweet
apple flavor
made from 100% apple. The water activity was 0.30. The apple candy morsels
were
packaged immediately in polyester film to prevent moisture pickup from the
air.
Example 2: Granular Apple Breakfast Food, 100% apple
Three commercial apple sources: dried Granny Smith variety sour apple dices,
Fuji variety sweet apple slices, and granular apple fiber, can be mixed in a
ribbon blender
for 2 minutes at proportions of 50%, 45% and 5%, respectively. The mix was
metered
into an Urschel 1700 Comitrol mill with a fine M-style cutting head, then
directly into the
feed section of a single screw extruder described in Example 1. The mix can be
processed under the same extrusion conditions and the same drying conditions
as in
Example 1. The dried product exiting from the drier can be roller-milled and
sifted, and
the fraction falling through a U.S. #4 Standard Sieve but remaining above a
U.S. #8
Standard Sieve retained for finished product packaging. The coarse particles
staying on
top of the #4 sieve can be recycled to the roller mill for regrinding, and the
fines falling
through the #8 sieve can be returned to the mixer and reprocessed. The
moisture content
is expected to be 5% with an Aw of 0.29. The resulting golden-brown crunchy
apple
granules will resemble Post Grape-Nuts cereal in appearance and texture, and
can be
served in a bowl with reduced-fat milk as part of a light, healthy breakfast.
A one-ounce
serving equals the apple solids in a medium-size (4-5 oz.) apple.
Example 3: Cranberry Puff-Ball Snack
Commercially available dried cranberry dices (advantageously not sugar
infused)
can be metered into an Urschel mill equipped with a fine M-style cutting head
and fed
22
CA 02559380 2012-02-14
directly into the pre-conditioner of a single screw extruder. Simultaneously,
rice flour
can be added at 20% of the cranberry rate, and the two ingredients mixed in
the extruder
pre-conditioner and fed directly into the feed throat of a single screw
extruder, with water
added into the first barrel (feed section) to moisten the rice flour, creating
inside the
extruder a homogeneous fruit dough composed of fruit and rice flour. The
extrudate can
be cut into approximate spherical puffed extrudate and dried in a forced-air,
continuous-
tray drier at 82 C (180 F) for 20 min to a moisture of 5% maximum. The half-
inch
diameter spheres are expected to exhibit a crunchy texture having a expected
density of
about 14 pounds per cubic foot, and a natural light red color and sweet, tart
cranberry
flavor. In the finished puffed product, the fresh fruit equivalent content is
expected to be
about 48%.
Example 4: Blueberry Puff
Commercially available dried blueberries (advantageously not sugar infused)
can
be processed as in Example 3. However, they can be cut into crispy, crunchy,
hard
puffed sphere extrudate approximately 3/16 inch in diameter for use in bakery
mixes for
muffins, breads, and doughnuts in place of expensive freeze-dried blueberries
or to
replace artificial blueberry pellets with a real fruit product.
Example 5: Apple Sprinkle Topping
Apple grinds (90%) were mixed with rice flour and/or apple fiber (10%) to coat
the apple grinds with the flour or fiber and improve their flowability and to
lower the
density of the finished product. The mix was processed as described in Example
1,
except that the fruit exiting the drier at 5% moisture was milled and sifted
through a U.S.
#10 sieve. The crunchy apple granules were packaged in a closable shaker
canister and
sprinkled over salads, meats, ice cream, and other foods.
23
CA 02559380 2012-02-14
The various methods and embodiments of the invention can be included in
combination with each other to produce variations of the disclosed methods and
embodiments, as would be understood by those with ordinary skill in the art,
given the
understanding provided herein. Also, various aspects of the embodiments could
be used
in conjunction with each other to accomplish the understood goals of the
invention. Also,
the directions such as "top," "bottom," "left," "right," "upper," "lower," and
other
directions and orientations are described herein for clarity in reference to
the figures and
are not to be limiting of the actual device or system or use of the device or
system.
Unless the context requires otherwise, the word "comprise" or variations such
as
"comprises" or "comprising", should be understood to imply the inclusion of at
least the
stated element or step or group of elements or steps or equivalents thereof,
and not the
exclusion of a greater numerical quantity or any other element or step or
group of
elements or steps or equivalents thereof. The device or system may be used in
a number
of directions and orientations. Further, the order of steps can occur in a
variety of
sequences unless otherwise specifically limited. The various steps described
herein can
be combined with other steps, interlineated with the stated steps, and/or
split into multiple
steps. Additionally, the headings herein are for the convenience of the reader
and are not
intended to limit the scope of the invention.
24
