U.S. patent application number 13/019724 was filed with the patent office on 2011-05-26 for water-based edible inks for ink-jet printing on confectionery.
This patent application is currently assigned to Mars Incorporated. Invention is credited to Pamela K. Gesford, Diane C. Kunkle, Arun V. Shastry.
Application Number | 20110123696 13/019724 |
Document ID | / |
Family ID | 32990726 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110123696 |
Kind Code |
A1 |
Shastry; Arun V. ; et
al. |
May 26, 2011 |
WATER-BASED EDIBLE INKS FOR INK-JET PRINTING ON CONFECTIONERY
Abstract
Non-pigmented, water-based inks are disclosed which are
compatible with industrial piezojet printheads and which can be
used to form high resolution images on edible substrates, including
sugar shell confectionery polished with a hydrophobic wax polish.
The ink comprises a hydrolyzable polysaccharide adhesive agent,
such as tapioca dextrin or gum arabic, which enhances the
compatibility of the ink for hydrophobic surfaces.
Inventors: |
Shastry; Arun V.; (Neshanic
Station, NJ) ; Gesford; Pamela K.; (Harleysville,
PA) ; Kunkle; Diane C.; (Coopersburg, PA) |
Assignee: |
Mars Incorporated
McLean
VA
BPSI Holdings, Inc.
Wilmington
DE
|
Family ID: |
32990726 |
Appl. No.: |
13/019724 |
Filed: |
February 2, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10795107 |
Mar 5, 2004 |
7906167 |
|
|
13019724 |
|
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|
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60453116 |
Mar 7, 2003 |
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Current U.S.
Class: |
426/383 ;
426/540 |
Current CPC
Class: |
A23G 3/54 20130101; A23G
3/0097 20130101; C09D 11/30 20130101; A21D 13/47 20170101 |
Class at
Publication: |
426/383 ;
426/540 |
International
Class: |
A23L 1/27 20060101
A23L001/27; A23G 3/54 20060101 A23G003/54 |
Claims
1. A non-pigmented water-based ink-jettable edible ink comprising:
(a) 50.0 to 85.0 wt. % water; (b) 7.0 to 35.0 wt. % organic solvent
selected from the group consisting of a C1 to C6 alcohol, propylene
glycol, and mixtures thereof; (c) 0.5 to 15.0 wt. % of a
non-pigmented edible colorant selected from the group consisting of
FD&C dyes, natural colorants, and synthetic colorants, wherein
the colorant is soluble in water or water-alcohol mixtures; (d) 2.0
to 40.0 wt. % binder; and (e) 1.5 to 8.0 wt. % of a dextrin or gum
adhesive agent, wherein the ink is substantially free of
conductivity-enhancing salts and has a conductivity lower than 700
micro Siemens, a viscosity of 5 to 20 centipoise, and a surface
tension of less than 50 dynes per centimeter when applied to an
edible substrate.
2. An edible ink of claim 1 which is ink-jettable with a piezojet
drop-on-demand ink-jet printer to form an image having a resolution
greater than 150 dots per inch.
3. An edible ink of claim 1 comprising 50.0 to 75.0 wt. %
water.
4. An edible ink of claim 1 comprising 10.0 to 30.0 wt. % organic
solvent.
5. An edible ink of claim 1 in which the organic solvent is
ethanol, isopropanol, butanol, propylene glycol, or mixtures
thereof.
6. An edible ink of claim 1 comprising 2.0 to 6.0 wt. % dextrin or
gum adhesive agent.
7. An edible ink of claim 1 in which the dextrin is tapioca dextrin
or the gum is gum arabic.
8. An edible ink of claim 1 in which the binder is a shellac-based
film former, polyvinylpyrrolidone, or a mixture thereof.
9. An edible ink of claim 8 comprising 8.0 to 25.0 wt. %
shellac-based film former and 1.5 to 12.0 wt. %
polyvinylpyrrolidone.
10. An edible ink of claim 1, comprising: (a) 50.0 to 75.0 wt. %
water; (b) 10.0 to 30.0 wt. % organic solvent; (c) 0.5 to 15.0 wt.
% of a non-pigmented edible colorant selected from the group
consisting of FD&C dyes, natural colorants, and synthetic
colorants, wherein the colorant is soluble in water or
water-alcohol mixtures; (d) 2.0 to 40.0 wt. % binder comprising,
with respect to the ink, 8.0 to 25 wt. % shellac-based film former
and 1.5 to 12.0 wt. % polyvinylpyrrolidone; and (e) 2.0 to 6.0 wt.
% dextrin or gum adhesive agent.
11. An edible ink of claim 1 having an intrinsic viscosity of 23 to
30 cubic centimeters per gram.
12. A method for ink-jet printing images on confectionery pieces,
comprising: (a) positioning a confectionery piece having a
hydrophobic surface proximate to a print station comprising a
piezojet drop-on-demand ink-jet printhead having at least one ink
reservoir; (b) supplying to the ink reservoir a non-pigmented
water-based ink-jettable edible ink comprising: (i) 50.0 to 85.0
wt. % water; (ii) 7.0 to 35.0 wt. % organic solvent selected from
the group consisting of a C1 to C6 alcohol, propylene glycol, and
mixtures thereof; (iii) 0.5 to 15.0 wt. % of a non-pigmented edible
colorant selected from the group consisting of FD&C dyes,
natural colorants, and synthetic colorants, wherein the colorant is
soluble in water or water-alcohol mixtures; (iv) 2.0 to 40.0 wt. %
binder; and (v) 1.5 to 8.0 wt. % of a dextrin or gum adhesive
agent, wherein the ink is substantially free of
conductivity-enhancing salts and has a conductivity lower than 700
micro Siemens; and (c) printing an image having a resolution
greater than 150 dots per inch on the hydrophobic surface with the
printhead.
13. A method according to claim 12, in which positioning the
confectionery piece comprises serially conveying a plurality of
confectionery pieces on a conveyor past the printhead.
14. A method according to claim 12, in which the printhead has
multiple reservoirs, and the method further comprises: (a)
supplying a pigmented edible white ink to one of the multiple
reservoirs; and (b) supplying the non-pigmented water-based
ink-jettable edible ink to another reservoir.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 10/795,107, filed Mar. 5, 2004, and claims the benefit of
priority of U.S. Provisional Application No. 60/453,116, filed Mar.
7, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention is directed to water-based inks for ink-jet
printing on edibles, to methods of ink-jet printing on edibles
using the inks, and to edible products made by such methods. The
inks and methods described herein may be employed for forming
printed edible products as diverse as pharmaceutical pills and
tablets to sausage casings. However, the invention has particular
utility for printing on confectionery, including, without
limitation, chocolate bars and tableted products, jelly beans,
toffees and chewing gums, and particularly for printing high
resolution and high definition images on non-planar, non-porous
hydrophobic surfaces of polished sugar shell confectionery, such as
the surfaces of M&M's.RTM. Milk Chocolate and Peanut Chocolate
Candies.
[0004] 2. Description of the Related Art
[0005] It is known to print identifying or decorative images on
edibles. The present technology for printing on M&M's.RTM. Milk
Chocolate and Peanut Chocolate Candies is by a contact printing
process utilizing an offset roller, in what is referred to herein
as rotogravure printing. The rotogravure system is limited in the
number of colors that can be applied to a substrate. Traditionally,
one color is printed, and with modifications two or three colors
may be applied, but full color printing on edibles is not possible.
The rotogravure roller is also limited in the surface area of a non
planar piece that it can print. As with other contact methods of
printing, there is a danger of the rotogravure roller crushing the
edible articles being printed. Print designs cannot be changed or
modified easily using the rotogravure method, because each new
design must be engraved on a roller. If a non-contact printing
method such as ink-jet printing could be used, there would be
distinct advantages.
[0006] The ink systems used in rotogravure printing, generally
comprise shellac, ethyl alcohol and pigments, to which may be added
dyes, plasticizers, additional solvents and other ingredients to
modify the characteristics of the ink. Such inks have a relatively
high viscosity such that they sit on the non-porous surface until
dry, and they are not ink-jettable. Thus, the inks conventionally
utilized for printing on small pieces of confectionery or on
pharmaceutical tablets and the like by the rotogravure method
cannot be adapted to ink-jet processes.
[0007] Another popular method for printing on edibles, particularly
on cakes and other large substrates, involves using an edible
transfer sheet which can be handled in a printer and which are
relatively porous and hydrophilic and therefore can readily accept
an image from a water-based ink, including an ink-jetted image.
Various methods are then used to transfer the image from the sheet
to an edible substrate. An exemplary ink for use with this type of
system is disclosed in U.S. Patent Application Publication US
2002/0008751 and comprises water, isopropyl alcohol, sodium lauryl
sulphate and FD&C colorant. In the transfer sheet technology,
printing is not performed directly on the surface of an edible
conveyed past a printhead. Using a transfer sheet requires a
component of the substrate to partly dissolve the sheet or to allow
the sheet to adhere to the substrate. Thus, the transfer sheet
technology is not readily adapted to the high speed production of
images on non-planar surfaces of confectionery pieces. The
water-based inks adapted for use with transfer sheets do not
perform properly for ink-jet printing on non-planar, non-porous and
hydrophobic surfaces, as they adhere poorly, dry too slowly and
lack opacity.
[0008] Ink-jet printing on edibles, particularly on sugar shell
confectionery pieces, if the technology could be perfected, would
be attractive from many vantage points: it would eliminate the need
to contact the edible substrate with a contact member such as a
roller. Further, since ink-jet printing is a non-contact printing
system, slight variations in the size of edibles would not
negatively impact upon printing quality, as typically occurs with
pad or roller based systems. Also, an ink-jet printer image is
stored as data, and not fixed on a contact member. Thus, if an
ink-jet printer could be effectively used, images could be
selected, altered, transmitted, and the like, more easily than in
contact printing, permitting faster changeover of designs. Use of
ink-jet technology would also permit full color printing using
multicolor printheads.
[0009] Ink-jet printing systems are broadly divided into continuous
jet, and drop-on-demand (also called "impulse") systems in which
droplets are generated as needed for ejection to the substrate
surface for image formation. Methods of ink-jet printing on edible
substrates using continuous jet technology have been disclosed.
Most of these are directed to labelling and similar applications
which do not require high resolution.
[0010] In continuous jet systems, ink is emitted in a continuous
stream under pressure through at least one nozzle. The stream is
broken up into droplets at a fixed distance from the orifice,
typically by a piezoelectric crystal, which is vibrated at
controlled frequency adjacent to the ink stream. The function of
the piezoelectric crystal is different in a continuous jet system
than in a piezojet drop-on-demand system. In a continuous jet
system, the ink stream is generated under pressure in the
reservoir, and the crystal serves simply to break up the droplets.
To control the flow of ink droplets, the inks are electrostatically
charged (by addition of salts and other conductive agents) and the
droplets are passed through an electrostatic field, which adjusts
the trajectory of the droplets, in accordance with digital data
signals. The conductance requirements for continuous jet inks
therefore range from 700 to 2000 micro Siemens, which generally
requires that the ink contains a conductivity enhancing salt. The
droplets are either directed back to a gutter for recirculation or
to a specific location on the substrate to create the desired
character matrix. A typical resolution for a continuous jet printer
image in an industrial setting, using a single printhead and a
single pass printing is about 75-100 dots per inch (dpi).
[0011] Most of the inks developed for continuous jet systems are
based on the solvent methyl ethyl ketone (MEK) and are therefore
not suitable for use in an edible ink. The inks that have been
developed for continuous jet printing on edibles, or on surfaces
which may contact edibles, have been pigmented, or based on
solvents associated with other drawbacks.
[0012] U.S. Pat. No. 5,453,122, for example, discloses an ink which
it is said can be applied directly to a foodstuff, or to packaging
closely associated with a foodstuff, and which avoids the use of
methyl ethyl ketone. The ink is also said to be suitable for use in
a piezojet printhead. However the ink relies on the presence of
substantial amounts of acetone solvent. If such an ink is less
toxic than an MEK-based ink, the substantial amounts of acetone in
such an ink limit its use for printing on edibles. Inks having
substantial amounts of acetone are less desirable to work with in
this area.
[0013] U.S. Pat. No. 5,800,601 discloses pigment-based inks said to
be suitable for printing on edibles, including glazed candies,
using a continuous jet system. Specifically, the disclosure is
directed to modification of pigment particle surface
characteristics to improve the drying time and adhesion of the
inks. These inks are also characterized by the presence of
conductivity enhancing salts.
[0014] U.S. Pat. No. 5,637,139 discloses non-aqueous inks, also for
continuous jet systems, and focused on applications for labelling
fruit and the like substrates with citrus # 2 dye.
[0015] Continuous jet inks also have a very narrow range of
acceptable viscosity. Inks having a viscosity above about 10
centipoise (cp) at low shear rates cause the pumps in the printhead
to cavitate during use. Below a viscosity of about 2 to about 3 cp,
the jets are not stable. Thus most, if not all, continuous jet ink
jet inks have a viscosity of about 2.8 to about 6 cp.
[0016] Commercially available continuous jet inks have not been
developed for printing on hydrophobic edible substrates. The
presence of conductivity enhancing salts required in these inks
would also be likely to affect taste.
[0017] Of the drop-on-demand systems, the most economically
important today are piezojet and bubblejet (sometimes referred to
as thermal ink-jet) systems. In bubblejet systems, a bubble is
formed by a resistance heater in an ink reservoir. The resulting
pressure wave from the bubble forces ink through the orifice plate,
and as the heat is removed, the bubble begins to collapse and a
droplet is ejected. Bubblejet printheads dominate the home and
office ink-jet printer markets and they are capable of very high
resolution. However, several considerations limit their use for
printing on edibles in an industrial setting.
[0018] This viscosity of bubblejet inks is very low, on the order
of 1.5 cp, necessary so that a bubble can form quickly upon
application of minimal voltage to the resistance heater. The known
bubblejet printers cannot readily handle the presence of binders or
polymeric additives. Moreover, the ink must be capable of
withstanding the temperature cycling encountered inside the
printhead. For these reasons, the number of inks which could be
developed for printing on edibles with a bubblejet printer is
extremely limited. The thermal jet printheads are also associated
with ink drying on the surface of the jet channels. It would be
preferable if piezojet systems could be developed for printing on
edibles, as piezojet printheads do not require large temperature
oscillations. Bubblejet printers are also much too slow to permit
high speed printing directly on edible substrates. Thermal jet
printheads (or bubble jet printheads, as they are also known) are
used for transfer sheet applications, because the transfer sheets
are porous and hydrophilic enough to be used with the known
inks.
[0019] Water-based edible inks known to be thermal jet compatible
are disclosed in co-pending U.S. application Ser. No. 10/211,592.
However, it has been demonstrated that these inks are incompatible
with hydrophobic surfaces.
[0020] A method of ink-jet printing on edibles is described in
co-pending U.S. patent application Ser. No. 09/587,108. The ink
described therein is a pigmented white ink which has found utility
for printing on chocolate.
[0021] Pigmented ink compositions, including non-white colored
pigmented inks, have been disclosed in the prior art, including the
aforesaid U.S. Pat. No. 5,800,601. However, pigmented inks are less
preferred for drop-on-demand ink-jet systems, because the pigments
can influence the rheology of the ink causing poor jettability.
Also, the presence of pigment particles may require additional
maintenance of the printhead. Once printed, the pigment particles
tend to sit on the substrate surface, flaking off easily, or
requiring the use of additional binders and/or resulting in poor
image adhesion.
[0022] Piezojet printheads are characterized by a piezoelectric
device which causes ejection of ink from a reservoir, such as by a
piezoelectric crystal deforming the wall of the reservoir in
accordance with data signals. Heretofore, edible inks have not been
developed for these systems. Piezojet printheads have larger
channels than bubblejet printheads which affords a greater range of
acceptable ink ingredients.
[0023] The food colorants approved for human consumption by the
United States Food and Drug Administration, and natural colorants
which generally do not require such approval, are water soluble,
and consequently food grade inks made from such colorants are
water-based. These water-based colorants tend to be poorly
compatible with hydrophobic surfaces of M&M's.RTM. Milk
Chocolate and Peanut Chocolate Candies, which are finished with
carnauba wax.
[0024] In summary, the rotogravure technology is not capable of
printing in full color on edibles and prohibits rapid changeover of
print designs, while continuous jet printing is not capable of
achieving high resolution. It would be desirable to print on
edibles with piezojet ink-jet systems to achieve these objectives.
However, water-based, non-pigmented inks suitable for piezojet
printheads, particularly inks having compatibility with hydrophobic
or waxy surfaces, have not heretofore been available. There is also
a need to print higher resolution, full color images on
confectionery, which rotogravure techniques are not capable of
delivering. Rotogravure techniques, because they rely on contacting
the substrate, can only print on a limited surface area of the
substrate. The contact printing systems, including rotogravure,
cannot accommodate irregularities in the size and shape of an
edible printing substrate, such are found, for example, on
M&M's.RTM. Milk Chocolate and Peanut Chocolate Candies.
[0025] Thus, there continues to be a need in the industry for
edible ink-jet compatible inks, particularly piezojet compatible
inks, which can be used to print high resolution images directly on
edible substrates, particularly those edible substrates that are
difficult to print on using conventional technology, such as those
having a sugar shell surface with a wax or fat polish coating.
SUMMARY OF THE INVENTION
[0026] In one aspect the invention is a pigment-free water-based
ink-jettable edible ink, which can form a high resolution image on
a hydrophobic edible substrate. The ink comprises water, an edible
colorant, and a hydrolyzable polysaccharide adhesive agent which
enhances the compatibility of the ink for a hydrophobic
surface.
[0027] In another aspect, the invention is a method for ink-jet
printing images on confectionery pieces in which confectionery
pieces having a hydrophobic surface are positioned proximate a
print station comprising a piezojet ink-jet printhead with at least
one ink reservoir containing an edible, water-based ink,
substantially free of conductivity enhancing salts, with a
hydrolyzable polysaccharide adhesive agent to enhance adhesion of
the ink to the hydrophobic surface. A high resolution image
composed of individual dried ink droplets is printed on the
confectionery by ejecting the ink from the piezojet ink-jet
printhead to the hydrophobic surface in accordance with image data
provided to the printhead.
[0028] In yet another aspect, the invention is the piece of
confectionery itself, having a hydrophobic surface (such as a sugar
shell polished with wax) with an image comprised of individual
dried ink droplets printed in a non-pigmented water-based ink
having an edible colorant and a hydrolyzable polysaccharide
adhesive agent to enhance the compatibility of the ink for the
surface. The image has a dpi resolution preferably greater than
about 100 dpi resolution and most preferably greater than about 300
dpi resolution.
[0029] In yet another aspect, the invention is an edible ink
comprising a colorant, an aqueous carrier for the colorant and an
image setting system. The image setting system is selected to
optimize the physical properties of the ink for piezojet ink-jet
printing on edible substrates, particularly hydrophobic substrates,
such that the ink sets properly and quickly on the surface. The
inks therefore have a viscosity in a range of about 5 centipoise to
about 20 centipoise and a surface tension below about 50 dynes/cm.
In the most preferred embodiments, the inks include an image
setting system containing an organic solvent, an adhesive agent and
a binder, each selected such that the inks have a viscosity in a
range of about 7 to about 15 centipoise and surface tension in a
range of about 30-45 dynes/cm.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The present invention is concerned with the industrial
adaptation of piezojet drop-on-demand systems, which heretofore
have not been used for printing high resolution images on edible
substrates. The characteristics of the printheads determine which
edible ingredients may or may not be used. Although the designs of
the printheads differ, they are all characterized by a
piezoelectric device which causes ejection of ink from a reservoir,
such as by a piezoelectric crystal deforming the wall of the
reservoir in accordance with data signals. The preferred piezojet
printhead for use with the invention is manufactured by Xaar
Technology Limited, located in Cambridge, United Kingdom. The
piezojet systems are readily distinguishable to those of ordinary
skill in the art from continuous jet or bubble jet systems. Thus,
"ink-jettable," as used herein, means an ink which can be ejected
reliably from a piezojet printhead, without requiring excessive
modification of the printhead or maintenance issues.
[0031] "Substantially free of conductivity enhancing salts" means
that salts are not added specifically to increase the conductivity
of the ink composition to a level, which the ink composition would
not have in the absence of such salts, such that droplets of the
ink can have their trajectory controlled in the electrostatic field
of a continuous jet printer. In addition to not being required in a
drop-on-demand system, these salts can have deleterious effects on
the printhead components, such as corrosion. In preferred
embodiments, the inks according to the invention have a
conductivity below about 1500 micro Siemens, preferably lower than
about 700 micro Siemens. An ink that is substantially free of
conductivity enhancing salts may referred to as a "non-conductive"
ink.
[0032] The ink systems according to the invention contain
ingredients that make them compatible with the inkjet printhead, so
that the inks will not damage the printhead components or cause
inconsistent firing of jets. The ink must also be compatible with
the surface of the edible substrate, providing a high resolution
image which does not rub off easily once it has been cured on the
surface. "Cured" in this context means that solvents have been
evaporated, and the image is well-adhered, hardened and dried on
the substrate.
[0033] Inks used in accordance with the present invention are
edible as used and preferably meet regulatory standards for use in
foods. This is of paramount importance in the area of printing on
confectionery. Whereas pharmaceutical tablets must meet certain
safety requirements, the fact that confectionery products are often
eaten in larger quantities than pharmaceuticals imposes additional
constraints on the ingredients that may be used in the inks.
[0034] All of the inks described herein are water-based. As used
herein "aqueous" is synonymous with "water-based" and refers to a
composition having greater than 50.0 percent by weight water. The
water-based inks generally contain water in a range of about 50.0
percent by weight to about 85.0 percent by weight. Preferably
deionized water is used. In the preferred embodiments, the inks
contain 50.0 percent by weight to 80.0 percent by weight water,
more preferably 50 percent by weight to about 75.0 percent by
weight water, and most preferably 55.0 percent by weight to about
75.0 percent by weight of the ink is water.
[0035] The carrier ordinarily contains at least one lower
(C.sub.1-C.sub.6) alcohol, propylene glycol or other organic
solvent in an amount effective to reduce or control the drying time
of the ink. As the surface tension of water is high (about 72 dynes
per centimeter), it is necessary to add a component to the image
setting system of the water-based inks to lower the surface tension
to below about 50 dynes/cm and preferably to a range of about 25 to
about 45 dynes/cm to permit efficient printing on an edible
substrate with a piezojet printhead. The surface tension of the ink
is important from the vantage point of compatibility with the
edible substrate surface, and for droplet formation in the
printhead.
[0036] A convenient measure of the compatibility of an ink with a
non-porous substrate is the contact angle that the droplets make
with the substrate surface. The ingredients of the ink are selected
so that the contact angle is less than 50 degrees, in a range of
about 10 degrees to about 50 degrees, preferably in a range of
about 20 degrees to about 45 degrees, and more preferably in a
range of about 30 to about 40 degrees. Of course, this
consideration is relevant primarily to relatively non-porous
surfaces.
[0037] The lower alcohol, propylene glycol or other organic solvent
is present in a range of about 7.0 percent by weight to about 35.0
percent by weight, preferably about 7.0 percent by weight to about
30.0 percent by weight and most preferably in a range from about
10.0 percent by weight to about 30.0 percent by weight. "Organic
solvents" includes all known solvents mostly miscible with the
water and the other ingredients of the ink. However in connection
with the water-based inks according to the invention, the preferred
organic solvent consists of ethyl alcohol, isopropyl alcohol, butyl
alcohol, propylene glycol or a mixture of them. Most preferably
about 10.0 to about 20.0 percent by weight of the ink is ethanol,
isopropyl alcohol, butanol, propylene glycol or a mixture of
them.
[0038] As used herein, "solvent-based" means a composition
containing more than about 35 percent by weight organic solvents.
Generally, the ink compositions according to the invention are free
of solvents such as acetates, lactates or solvents containing
benzyl groups. In preferred embodiments, glycerol and esters are
completely excluded from the composition.
[0039] Suitable edible colorants include: the food dyes approved
for human consumption under the Food, Drug and Cosmetic Act
administered by the U.S. Food and Drug Administration (FDA),
referred to herein as "FD&C dyes"; natural colorants derived
from natural (usually vegetable) sources which are generally
assumed to be safe for human consumption; colorants derived from
natural sources which are FDA-approved; and synthetic colorants
approved for use in non-U.S. jurisdictions. All of the edible
colorants which can be used with the invention must be soluble in
water or water-alcohol mixtures.
[0040] FD&C dyes that may be used include Red No. 3
(Erythrosine), Red No. 40 (Allura Red), Yellow No. 6 (Sunset Yel.
FCF), Yellow No. 5 (Tartrazine), Green No. 3 (Fast Green FCF), Blue
No. 1 (Brilliant Blue FCF), Blue No. 2 (Indigotine), and mixtures
thereof. Natural colorants which may be used include: anthocyanins,
betalins, carotenoids, and the like and mixtures thereof. Any of
the foregoing colorants may be used in ink formulations according
to the invention provided that the formulation as a whole is
compatible with the printhead and provides sufficient adhesion to
the surface of the edible substrate. In the most preferred
embodiments, the foregoing colorants are completely solvated in the
ink formulation such that there are substantially no colorant
solids in the ink. The substantial absence of colorant solids in
this context means less than about 5.0 percent by weight solids,
preferably less than about 1.0 percent by weight solids. Even more
preferably, the ink contain less than 0.1 percent by weight
solids.
[0041] Edible colorant is present in the ink in an amount of about
0.5 percent by weight to about 15.0 percent by weight. Preferably,
the ink contains about 0.5 percent by weight to about 10.0 percent
by weight edible colorant; more preferably about 0.5 percent by
weight to about 8.0 percent by weight; and most preferably about
0.5 percent by weight to about 6.0 percent by weight. The optimal
amount of colorant in the ink appears to range from about 0.5
percent by weight to about 4.0 percent by weight. It has been found
that, within the above ranges, some edible colorants (such as blue)
require somewhat lower concentration to supply the same level of
color saturation as it appears on the surface of the product, while
other edible colorants (such as yellow) require somewhat more.
[0042] The ink composition also contains a hydrolyzable
polysaccharide adhesive agent. Preferably the polysaccharide
adhesive agent is present in the ink in a range of about 0.1
percent by weight to about 15.0 percent by weight, preferably in a
range of about 0.5 percent by weight to about 12.0 percent by
weight, more preferably in a range of about 1.0 percent by weight
to about 10.0 percent by weight, and most preferably in a range of
about 1.5 percent by weight to about 8.0 percent by weight of the
ink composition. The optimal range for the hydrolyzable
polysaccharide adhesive agent appears to be about 2.0 percent by
weight to about 6.0 percent by weight of the ink composition.
[0043] The hydrolyzable polysaccharide preferably is a dextrin,
cyclodextrin, or a gum, a carageenan, an alginate or calcium
alginate, or a combination of such polysaccharides. The most
preferred dextrin is tapioca dextrin. The most preferred gum is gum
arabic.
[0044] It is also possible to substitute other adhesive agents,
which when cured undergo crosslinking to enhance adhesion of the
image to the edible substrate. In this context, proteinaceous
materials, including gelatin, or cellulosic materials and/or
hydrolyzed starch may be used.
[0045] Ink formulations according to the invention preferably
contain a binder. A "binder" is understood to refer to an
ingredient which forms a film between the components of the ink
after all the solvent is removed and the image cured on the
substrate. Thus, a binder can be easily distinguished both in terms
of function and composition from the adhesive agent which is added
to improve the compatibility of the ink for a particular surface.
Known binders include shellac (which is usually combined with
ammonia to raise the pH to about 9 to solubilize the shellac in
water). Shellac may be diluted with water, or with ethyl alcohol or
a like solvent. A shellac-based film former is available under the
trade name Mantrolac.RTM. from Mantrose-Haeuer Co., Inc., Westport,
Conn. As used herein, "shellac" is used interchangeably with
"shellac-based film former" and percentages by weight refer to the
percentage by weight of a shellac-based film former.
[0046] Polyvinylpyrrolidone (also referred to as
polyvinylpyrrolidinone, povidone or PVP) may also be used in the
edible binder system. The preferred binder for use in the
water-based, non-pigmented inks according to the invention is a
combination of polyvinylpyrrolidone and shellac, which has been
shown to have unexpectedly improved impact on drying time and image
quality over compositions which do not contain this
combination.
[0047] The composition contains a binder in a range of about 2.0
percent by weight to about 40.0 percent by weight. A shellac-based
film former may be present in an amount of about 2.0 percent by
weight to about 40.0 percent by weight of the ink. Preferably,
shellac is present in a range of about 4.0 percent by weight to
about 35.0 percent by weight, more preferably in a range of about
5.0 percent by weight to about 30.0 percent by weight and most
preferably in a range of about 8.0 to about 25.0 percent by weight
with respect to the ink composition. The optimal amount of shellac
is believed to be in a range of about 10.0 to about 20.0 percent by
weight of the ink composition.
[0048] Polyvinylpyrrolidone may be present in an amount of about
0.01 percent by weight to about 20.0 percent by weight of the ink.
Preferably, polyvinylpyrrolidone is present in a range of about 0.5
percent by weight to about 18.0 percent by weight, more preferably
in a range of about 1.0 percent by weight to about 15.0 percent by
weight and most preferably in a range of about 1.5 to about 12.0
percent by weight with respect to the ink composition. The optimal
amount of polyvinylpyrrolidone is believed to be in a range of
about 1.5 to about 10.0 percent of the ink composition.
[0049] The organic solvent (which is preferably a lower alcohol),
the adhesive agent (which is preferably starch, a dextrin or a
gum), and the binder system (which is most preferably a combination
of shellac and polyvinylpyrrolidone) may be considered together as
an "image setting system." These are the ingredients added to the
aqueous carrier and the colorant to reduce drying time and surface
tension of the ink, and to enhance compatibility of the ink with
the edible substrate such that a durable adherent image is formed
upon curing.
[0050] Other functional ingredients may be added to the composition
to improve the performance of the ink. For example, a
preservative/antimicrobial such as Polysorbate 80 may be added,
preferably in an amount less than about 1 percent by weight.
Antifoam agents, such as simethicone emulsion may be added, again
preferably in an amount less than about 1 percent by weight.
[0051] Preservatives, flavorants, aromatics, micro-nutrients and
vitamins may all be added in customary amounts to improve the
attributes of the finished confectionery.
[0052] The foregoing ingredients are preferably selected such that
the viscosity is in a range of about 5 centipoise to about 20
centipoise, more preferably in a range of about 7 to about 15
centipoise, measured at a shear rate of 200 s.sup.-1 and 20.degree.
C. If the viscosity of the ink is much below 5 centipoise,
satellite ink droplets tend to form around the main droplet forming
the ink-jetted image, resulting in decreased image resolution. If
the viscosity is too high, it becomes difficult to achieve
sufficient pressure in the reservoir using a piezoelectric crystal.
As a general rule, and as known in the art outside the field of
printing with edible inks, ingredients should be selected to avoid
the presence of dissolved gases in the ink, which can cause
cavitation in the printhead.
Ink Composition Examples
[0053] The following compositions contain tapioca dextrin:
TABLE-US-00001 TABLE 1 1 2 3 4 5 6 Water 65-67 73.40 68.40 68.34
73.4 60.40 Organic 13.2 12.00 17.00 17.07 12.00 25.00 Solvent***
Colorant 1.9-2.5 3.98 4.0 4.0 4.0 4.0 Shellac 10 (Aq.) -- -- -- --
-- Povidone 5.00 5.00 5.00 5.00 5.00 5.00 Ammonia 0.5 -- -- -- --
-- (Aq.) Dextrin 2.5 5.0 5.0 5.0 5.0 5.0 Additives** 0.60 0.60 0.60
0.60 0.60 0.60 **Antifoam agent and preservative ***Combinations of
propylene glycol, isopropyl alcohol and butanol
Ink Composition Comparative Examples
[0054] The following compositions contain a shellac/povidone binder
system, without the hydrolyzable polysaccharide adhesive agent.
TABLE-US-00002 TABLE 2 7 8 9 10 11 12 Water 70.60 52.90 52.90 67.90
56.60 67-68 Organic 11.94 17.00 17.00 12.00 25.00 13.2 Solvent***
Colorant 3.96 4.00 4.00 4.00 2.50 2-3 Shellac 9.95 20.00 10 (Aq.)
10 10.00 10.00 10 (Aq.) (EtOH) Povidone 2.50 5.00 5.00 5.00 5.00
5.00 Ammonia 0.50 0.50 0.50 0.50 0.30 0.5 (Aq.) Dextrin -- -- -- --
-- -- Additives** 0.60 0.60 0.60 0.60 0.60 0.60 **Antifoam agent
and preservatives ***Combinations of propylene glycol, isopropyl
alcohol and butanol
[0055] A composition according to Example 1 is prepared except that
the dextrin is replaced with 2.5 grams of gum arabic, yielding
another embodiment in accordance with the invention. A composition
having the composition of Example 2 is prepared, except that 5.0
grams carageenan is substituted for the dextrin. The resulting ink
is within the scope of the invention. A composition according to
Example 12 is prepared, and 5.0 grams of a cyclodextrin is added to
produce another composition within the scope of the invention.
Ink and Ink Image Properties
[0056] An important parameter useful in characterizing the ink
systems for printing on edibles is the intrinsic viscosity, defined
as the limiting value of the ratio of specific viscosity to
concentration at infinite dilution.
[ .eta. ] = lim c .fwdarw. 0 ( .eta. i / c ) = lim c .fwdarw. 0
.eta. inh ##EQU00001##
[0057] wherein [.eta.] is the intrinsic viscosity, [.eta..sub.i] is
the specific viscosity (also equal to .eta..sub.r-1, where
.eta..sub.r=solution viscosity/solvent viscosity), c is
concentration, and .eta..sub.inh is the inherent viscosity (also
equal to 1n.eta..sub.r/c).
[0058] Intrinsic viscosity is usually used to characterize the
viscous effect of a polymer in a particular solvent. In the context
of the present invention, the binder and adhesive agent are
considered the "polymer" and the remainder of the ingredients in
the inks is considered the "solvent" to determine the intrinsic
viscosity. Intrinsic viscosity has units of inverse concentration.
It has surprisingly been found that intrinsic viscosity correlates
with the compatibility of an ink for a given edible substrate
surface. Higher intrinsic viscosities correlate with better
adhesion.
[0059] To obtain an intrinsic viscosity for the binders/adhesive
agents in the ink, a Canon-Fenske (Ostwaald-type) viscometer was
used. The viscometer was calibrated with deionized water at
20.degree. C., which has a known viscosity. The viscometer was then
filled with the ink to be tested and the viscosity measured. The
ink was diluted by 50 percent by volume with deionized water and
the viscosity measured again. The process was repeated at
successive dilutions and the resulting plot extrapolated to zero
concentration.
[0060] Table 3 shows the intrinsic viscosity of an exemplary ink
according to the invention and a Comparative Example, measured at
20.degree. C. in a Canon-Fenske viscometer. Preferred inks
according to the invention have an intrinsic viscosity in a range
of about 23 to about 30 cc/gram.
TABLE-US-00003 TABLE 3 Comparative Example 12 Example 1 intrinsic
viscosity 21.4 23.6
[0061] Compatibility with a surface may be determined by a variety
of methods. For example, when the surface of the edible substrate
is non-porous and hydrophobic, a smaller contact angle made by the
ink droplet on the surface is consistent with better compatibility
and adhesion of the ink for the substrate, as well as with reduced
drying time.
[0062] Contact angle measurements were made of ink droplets
according to the invention on a surface of a confectionery piece
having a carnauba wax polish coating similar to a surface found on
M&M'S.RTM. Milk Chocolate Candies. A comparison of the contact
angle (left and right side of the droplet) with a similar
measurement made for a droplet of deionized water shows the
substantial reduction in contact angle brought about by the image
setting system.
TABLE-US-00004 TABLE 4 (CONTACT ANGLE) Example 6 Deionized water
Left Right Left Right 32 38 74 72 40 34 72 68 38 34 76 74 34 37 74
66
[0063] In preferred embodiments, methods according to the invention
involve printing of multicolor images utilizing multicolor
printheads. In preferred embodiments, a standard ink jet printhead
is modified by installing a white ink reservoir and print engine
where the black ink reservoir and print engine are found in a
standard printhead configuration and providing a white pigmented
ink to that reservoir. The remaining print engines may be provided
with water-based inks in the customary colors (cyan, magenta, and
yellow), in the ordinary configuration. The standard KCMY
arrangement can be used, where the letters KCMY are understood to
refer to white, cyan, magenta and yellow print engines, arranged in
that order in the direction of print travel. It is contemplated
that printheads with more than 4 colors could be used. It is also
known to print without a white print engine, using a separate black
print engine or a combination of cyan, magenta and yellow to make
black. Any of the foregoing configurations could be used without
departing from the scope of the invention.
[0064] It is contemplated that almost any edible surface can be
printed using these inks. These foods include, without limitation,
baked goods, biscuits and cakes, cookies, nuts, chocolates,
cheeses, crackers and chips, and pastries, puddings and mousses,
ice creams and creams, petfood and pet treats, main meal snacks,
cereals, sausage casings and pharmaceutical tablets. In
particularly preferred embodiments, images are printed onto sugar
shelled confections having a hydrophobic wax coating, such as
M&M's.RTM. Peanut and Milk Chocolate Candies.
[0065] Resolution for an ink-jet printer may be defined by the
density of pixels making up an image. Continuous jet systems are
typically capable of achieving resolution of about 75 to about 100
dpi. In the context of the present invention, less than about 100
dpi is considered low resolution and greater than about 100 dpi is
defined as high resolution. Among the printheads capable of
producing high resolution images, low end piezojet systems are
typically capable of resolution in the range of about 100 dpi to
about 150 dpi, which is defined herein as moderately high
resolution. More advanced piezojet systems, such as those available
from Xaar Technology Limited (Cambridge, United Kingdom) or
Spectra, Incorporated, (Lebanon, N.H. U.S.A.) are capable of
printing at 150 dpi to 300 dpi, herein defined as very high
resolution which affords very good line art images, clip art
images, cartoon-type images as well as text and schematic images.
By optimizing printing techniques, resolution of 300 dpi to 800 dpi
can be achieved, which may be termed near-photographic or
photographic high resolution. Bubblejet ink-jet technology,
predominantly found in the home and office printer markets, can
produce images up to 1600 dpi in some cases. However, the bubblejet
printheads are slow, have very small channels and require extremely
low viscosity inks, which makes them unsuitable for commercial
printing on edibles with a wide range of inks. The ingredients
needed to improve image adhesion with a hydrophobic surface would
likely create fouling issues if used with a thermal jet system due
to the high temperatures encountered in those printheads. An
advantage of the methods according to the present invention is that
they make possible confectionery products bearing images having a
resolution greater than about 100 dpi, preferably greater than
about 150 dpi and even more preferably greater than about 300 dpi,
using a wide variety of inks. Using the technology described
herein, the inventors have formed ink-jet photographic likeness of
individuals on M&M's.RTM. Milk Chocolate and Peanut Chocolate
Candies.
[0066] Techniques are known in the art for increasing the
dots-per-inch resolution of an ink-jet printed image. These include
what is known as "stitching" or "interlacing" the printheads.
Another technique involves positioning the printheads at an angle
with respect to the traveling direction of the substrate. Both of
these methods result in more droplets impinging on a given printing
area. While these techniques can be used with the present
invention, it is the performance of the inks on the substrates in
question that permits the techniques to be used in the first place.
Performance of the ink includes the ability of each droplet to
maintain its integrity and not to mingle with other droplets before
drying. Thus, it must be emphasized that resolution is not simply a
function of the equipment used, but of the performance of the ink
on a given edible substrate.
[0067] Another measure of image quality is referred to herein as
adhesion. To determine the image adhesion, an aluminum block was
designed with a cavity to hold a confectionery piece. The piece was
a white M&M's.RTM. Milk Chocolate Candies piece, having a sugar
shell with a carnauba wax coating. The piece was placed with the
image facing upwards. An 8.5'' (21.6 cm) long paper piece was
placed on top of the candy piece such that the paper sat directly
on top of the printed image. The paper used was Xerox.RTM. brand
4024 type copier paper. Another block with a groove to follow the
curvature of the candy piece was placed on top of the candy piece,
and aligned with the bottom block by two pins. A weight of 1 lb
(454 g) was placed on top of the upper metal block, and the paper
piece was pulled across the "image" portion of the candy piece. The
length of the paper that was moved across the candy piece was 7.5''
(19.05 cm) under the 1 lb (454 g) weight.
[0068] The image was a large "m" printed with red ink, 1 cm wide by
0.6 cm high with a line thickness of 0.15 cm. In each case, the
image was analyzed for overall brightness using a Minolta CM-3500d
spectrophotometer. The medium aperture sample holder was used for
the analysis. As the candy pieces were all white, a higher
brightness value means that the some of the image was lost during
the abrasion of the paper under the weight. A brightness measure
"L" was made before and after the test described above. A high
difference in brightness before and after the test (".DELTA.L")
corresponds to poor image adhesion.
[0069] The following results were observed for Examples 1 and 6 and
Comparative Example 10:
TABLE-US-00005 TABLE 5 Example .DELTA.L Std. Deviation 1 1.2 1.2 6
1.6 1.4 10 (Comparative) 4.2 0.4
[0070] At least qualitatively, the presence of dextrin is observed
to result in an increase in adhesion, and the combination of
povidone, shellac and dextrin yields still better adhesion results.
It is preferred to use inks resulting in an image adhesion value
(".DELTA.L") less than 4, more preferably less than 3, and most
preferably less than 2.
[0071] In printing baked goods, such as cookies, the edible
substrates are conveyed in any manner conventionally practiced in
the art, such as a belt conveyor. The edible substrates are
conveyed past a stationery piezoelectric printhead, such as a type
commercially available from Xaar Technology Limited, Cambridge,
United Kingdom. Water based inks according to the invention, as
described above are provided to the printhead. The standard
configuration provides for reservoirs of cyan, magenta and yellow
ink. A fourth reservoir (conventionally provided with black ink),
may be provided with an edible black ink, or more preferably with
an edible white pigmented ink. Ink is ejected from the printhead in
accordance with image data and the ejected droplets cure on the
surface to form dried ink droplets on the substrate in an image
having a resolution of greater than 100 dpi.
[0072] In printing relatively small confectionery pieces such as
M&M's.RTM. Milk Chocolate and Peanut Chocolate Candies, it is
preferable to convey the pieces on a conveyor and hold them in
place as they pass a stationery printhead, which may have the same
configuration described above. Generally a pocket shaped to hold
the piece is sufficient to hold the pieces in place, although if
necessary, a trapping mechanism or vacuum may be utilized to keep
the pieces immobile during the printing process to ensure the best
resolution. The conveyor may be a drum with pockets or an endless
belt with carrier bars. Methods and apparatus for conveying small
edible pieces are described in co-pending application Ser. No.
09/479,549. Other approaches are also possible, for example
transporting the pieces directly on a belt.
[0073] While the present invention has been described with respect
to what are presently considered to be the preferred embodiments,
the invention is not to be limited to the disclosed embodiments.
Rather, the present invention encompasses various modifications and
equivalents included within the spirit and scope of the appended
claims. The scope of the appended claims is to be accorded the
broadest interpretation so as to encompass all such modifications
and equivalent materials and functions.
* * * * *