U.S. patent application number 12/042503 was filed with the patent office on 2008-07-31 for film having a liquid absorbed therein.
This patent application is currently assigned to VECTOR USE INC.. Invention is credited to Brian R. Samuels.
Application Number | 20080182035 12/042503 |
Document ID | / |
Family ID | 33032673 |
Filed Date | 2008-07-31 |
United States Patent
Application |
20080182035 |
Kind Code |
A1 |
Samuels; Brian R. |
July 31, 2008 |
Film Having a Liquid Absorbed Therein
Abstract
The present invention relates to a film having a liquid at least
partially absorbed therein, wherein the liquid has been applied to
a surface of the film and prior to application of the liquid to the
surface, the surface has been subjected to a surface activation
treatment such that the surface has a surface energy of at least
about 50 dynes.
Inventors: |
Samuels; Brian R.;
(Frankfort, IL) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 S. WACKER DRIVE, SUITE 6300, SEARS TOWER
CHICAGO
IL
60606
US
|
Assignee: |
VECTOR USE INC.
Oak Brook
IL
|
Family ID: |
33032673 |
Appl. No.: |
12/042503 |
Filed: |
March 5, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10798462 |
Mar 11, 2004 |
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12042503 |
|
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60501339 |
Sep 8, 2003 |
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60454444 |
Mar 13, 2003 |
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Current U.S.
Class: |
427/540 ;
427/322; 427/551; 427/553 |
Current CPC
Class: |
Y10T 428/1359 20150115;
Y10T 428/3175 20150401; A22C 13/00 20130101; B29C 59/08 20130101;
C08J 2323/12 20130101; Y10T 428/3188 20150401; Y10T 428/1355
20150115; C08J 7/048 20200101; B29L 2023/002 20130101; Y10T
428/1303 20150115; Y10T 428/139 20150115; A22C 2013/0046 20130101;
Y10T 428/1352 20150115; B29C 59/085 20130101; C08J 2477/00
20130101; B29C 59/00 20130101; B29C 59/165 20130101; B29C 2035/0827
20130101; B29C 2035/085 20130101; Y10T 428/31971 20150401; Y10T
428/13 20150115; B29C 59/142 20130101; A22C 13/0013 20130101; Y10T
428/1324 20150115; C08J 7/043 20200101; B29C 59/103 20130101; Y10T
428/31855 20150401; Y10T 428/1393 20150115; B29C 59/10 20130101;
B29C 2035/0877 20130101; B29C 59/16 20130101; C08J 7/056 20200101;
B29C 59/14 20130101 |
Class at
Publication: |
427/540 ;
427/322; 427/553; 427/551 |
International
Class: |
B05D 3/06 20060101
B05D003/06 |
Claims
1. (canceled)
2. The method of claim 18 wherein the surface activation treatment
is selected from the group consisting of plasma treatment, flame
treatment, corona discharge, UV irradiation, electron beam
irradiation, and gamma irradiation.
3. (canceled)
4. (canceled)
5. (canceled)
6. The method of claim 18 wherein the liquid has been applied to
the surface in an amount of between about 0.4 to about 10
mg/cm.sup.2.
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. A method of preparing a nylon film having a liquid at least
partially absorbed therein comprising subjecting a surface of the
nylon film to a surface activation treatment such that the surface
has a surface energy of at least about 70 dynes, then applying a
liquid to the surface such that the liquid is at least partially
absorbed into the film, wherein an amount of liquid able to be
absorbed by the nylon film after said surface activation is greater
than an amount of liquid able to be absorbed before said
activation.
19. The method of claim 18, wherein the surface activation
treatment is corona discharge.
20. The method of claim 19, wherein the corona discharge has been
conducted at a power level of between about 50 and 1000
W-m/M.sup.2.
21. The method of claim 20, wherein the power level is between
about 100 to about 600 W-m/M.sup.2.
22. The method of claim 18, wherein the film is in the form of a
food packaging film, whereby in use the surface is an inner surface
of the film.
23. (canceled)
24. The method of claim 18, wherein the nylon film comprises a
nylon and a crosslinked polyvinylpyrrolidone.
25. The method of claim 24 wherein the film is a monolayer.
26. The method of claim 22 wherein the food packaging film has at
least two layers, a first layer comprising the a nylon and an
optional crosslinked polyvinylpyrrolidone, and a second layer
comprising a layer of a polyolefin material, whereby in use, the
first nylon layer is an inner layer and the second polyolefin layer
is an outer layer thereof.
27. The method of claim 22, wherein the film is in the form of a
tubular casing.
28. The method of claim 27, wherein after the liquid is applied to
the surface, the casing is shirred.
29. The method of claim 22 wherein the liquid consists essentially
of water.
30. The method of claim 22, wherein the liquid is a composition
comprising at least one additive for transfer to a packaged food
article packaged in the food packaging film.
31. The method of claim 30, wherein the additive is selected from
the group consisting of a coloring agent, a flavoring agent, and a
coloring and flavoring agent.
32. The method of claim 30, wherein the additive comprises a
Maillard reagent.
33. The method of claim 18, wherein after the liquid has been
applied to the surface, the film is passed between a pair of nip
rolls and a spacing between the nip rolls is set at a distance less
than the thickness of the film.
34. (canceled)
35. (canceled)
36. (canceled)
37. (canceled)
38. (canceled)
39. (canceled)
40. (canceled)
41. (canceled)
42. The method of claim 18 wherein the nylon film consists of
(a)(i) one or more aliphatic primary diamine and one or more
aliphatic dicarboxylic acid, (ii) an omega-aminocarboxylic acid,
(iii) an omega-aminocarboxylic lactam, or (iv) a mixture of two or
three of (i), (ii), and (iii), and optionally, (b) a crosslinked
polyvinylpyrrolidone.
43. The method of claim 18 wherein the nylon is nylon 6.
44. The method of claim 26 wherein the food packaging film has a
third nylon layer over the polyolefin layer.
45. The method of claim 44 wherein the third layer comprises nylon
66.
46. The method of claim 18, wherein the liquid is absorbed to a
depth of up to about one-half of a thickness of the nylon surface
layer.
47. The method of claim 18, wherein the liquid is absorbed to a
depth of up to about 5 microns of a thickness of the nylon surface
layer.
48. The method of claim 18, wherein the surface of the film
receives energy of a watt density of at least 50 W-min/m.sup.2.
49. A method of preparing a nylon film having a liquid at least
partially absorbed therein comprising subjecting a surface of the
nylon film to a surface activation treatment by an application of
energy such that the surface receives energy of a watt density of
at least about 75 W-min/m.sup.2, then applying a liquid to the
surface such that the liquid is at least partially absorbed into
the film, wherein an amount of liquid able to be absorbed by the
nylon film after said surface activation is greater than an amount
of liquid able to be absorbed before said activation.
50. The method of claim 49, wherein the surface of the nylon film
receives energy of a watt density of up to about 500
W-min/m.sup.2.
51. The method of claim 49, wherein the liquid is absorbed up to
about one-half of a thickness of the nylon film.
52. The method of claim 49, wherein the liquid is absorbed to a
depth of up to about 5 microns of a thickness of the nylon surface
layer.
53. The method of claim 49, wherein the liquid has been applied to
the surface, the film is passed between a pair of nip rolls and a
spacing between the nip rolls is set at a distance less than the
thickness of the film.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 60/501,339, filed Sep. 8, 2003, and
U.S. provisional patent application Ser. No. 60/454,444, filed 13
Mar. 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to a film having a surface
with a liquid at least partially absorbed therein. In particular,
the present invention relates to a film for use as a packaging for
a food product and especially relates to a tubular food casing for
food, which is to be cooked or otherwise heated within the
casing.
BACKGROUND OF THE INVENTION
[0003] The present invention will be described with particular
reference to a film for use in packaging food. However, it will be
appreciated that the film of the present invention may have
applications and uses other than in the food industry and no
limitation is intended thereby.
[0004] There are a number of applications for articles having a
material with a liquid absorbed onto a surface thereof. Such
applications include "patches" as used for slow release topical
administration of therapeutic agents and food casings for release
of a flavouring and/or colouring agent into the food encased
therein. However, the types of materials which can be used to form
such articles are strictly limited to those having suitable
absorption or permeability properties for the desired liquid.
[0005] In practice, this has severely restricted the types of
materials which may be used. Generally for hydrophilic liquids, the
materials used are cellulosic materials and derivatives or
modifications of water soluble polymers such as polyacrylamide,
polyvinyl alcohol, polyvinylpyrolidone and the like. These
materials are typically modified such that the articles formed
therefrom are no longer water soluble but are able to absorb at
least some water. The polymers may be crosslinked and/or blended or
copolymerised with less hydrophilic and/or hydrophobic polymers or
monomers. A particular application of a film having a liquid
absorbed therein are cellulosic food casings having a smoke
flavouring agent known as "liquid smoke" absorbed therein. Such
casings have been developed to be able to apply a smoke flavour
and/or colour to a food product as an alternative to the
traditional smoking process.
[0006] The traditional smoking process involves stuffing a food to
be smoked, such as a sausage, into a smoke permeable casing and
hanging the stuffed food product in a smoke house in which wood was
burned at low temperature to generate smoke. Smoking by such
traditional techniques is labour intensive, time consuming (with
smoking times being up to a number of days) and the level of smoke
generated often conflicts with pollution laws.
[0007] In order to provide the benefits of a smoked product but
without the drawbacks of conventional smoking techniques, liquid
smoke was developed some 65 years ago. Liquid smoke is the aqueous
condensate of natural wood smoke, which contains aldehydes that
react with proteins in the meat resulting in browning of the meat
surface. This browning can give the appearance of a naturally
smoked product
[0008] Liquid smoke was originally sprayed onto meat products
encased in porous natural gut or cellulose casings prior to cooking
by placing in an oven. The porosity of the casings allowed the
liquid smoke to penetrate the casing and into the meat. In
practice, however, it has been found that with this spraying
process it is difficult to provide a uniform coating to the
product. Further, the liquid smoke spray tended to run down the
sides of the stuffed casing and gather at the lower end thereof.
This uneven coating of liquid smoke resulted in a product having an
undesirable blotchy appearance.
[0009] In the light of these difficulties, much work has been
conducted with a view to providing a substantially uniform
distribution of liquid smoke onto the surface. Some attempts have
been made to incorporate liquid smoke into the meat product itself.
However, this provides either an insufficient amount of agent on
the surface to provide the desired colour, or imparts an
excessively smoky flavour to the product.
[0010] A more successful approach has been to incorporate liquid
smoke into a cellulose casing or absorb liquid smoke onto the
surface of a cellulose casing. Techniques for absorbing liquid
smoke onto a cellulose casing include dipping or spraying the
cellulose casing with a liquid smoke solution so that the liquid
smoke permeates to the interior surface for eventual transfer to an
encased product. Such external treatment can present difficulties
with further processing of the cellulose casings and in particular,
may interfere with shirring. Despite these difficulties, there are
a number of liquid smoke treated cellulose casings on the
market.
[0011] The permeability and porosity of cellulose casings which on
the one hand, makes them compatible for use with liquid smoke, on
the other hand introduces serious and widely recognized
disadvantages. First, cellulose products are highly permeable to
water vapour. This allows moisture loss during cooking and a
corresponding decrease in overall weight of the product. This
results in a reduced yield of product, which is disadvantageous for
commercial reasons. Further, cellulose casings are also oxygen
permeable which leads to spoiling and/or discolouration of the food
product. As a result of this latter difficulty, food products
cooked in cellulose casings must either by consumed shortly after
cooking, or be removed from the casings and wrapped a second time
as quickly as possible after production with an oxygen impermeable
barrier casing. This rewrapping step provides an opportunity for
contamination or infection of the food product that represents a
loss in quality and shortening of shelf life. Further, the
additional steps add to costs.
[0012] To address the disadvantages of permeable cellulose casings,
water and oxygen impermeable thermoplastic casings were developed.
When using casing of this type, there is negligible loss in weight
during the production process or during storage and shipping.
Further, the product can remain sterile provided the casings remain
intact. However, as a result of the impermability of the casing,
smoke in either gaseous or liquid form cannot penetrate the casing.
Further, impregnation of thermoplastic casings with liquid smoke or
other colouring additives has not been successful since the
plastics used cannot adequately absorb and store impregnating
agents. In order to impart a smoke colour to plastic encased
products, it is necessary to remove the casings and apply smoke by
techniques such as spraying or dipping liquid smoke or atomizing
and the product repackaged. These additional steps not only
increase cost but increase the risk of contamination.
[0013] Another approach has been to provide a cellulose/plastic
laminate, the inner cellulose layer having a coloring agent
absorbed therein and the plastic intended to provide an oxygen
barrier layer. In practice however, when meats are cooked in
packages formed from this material, juices collect between the meat
and package. Such a condition is known as "cook-out" or purge .
This is undesirable from a consumer acceptance point of view.
Further, it has been observed that there is a tendency for flaking
or chipping of the cooked meat surface during slicing.
[0014] There is a recognized need in the industry to provide a gas
and moisture impermeable casing having a food additive such as
liquid smoke absorbed therein. However, to date all attempts to
solve this problem and provide a commercially acceptable product
have failed for one reason or another. One approach has been to
blend a liquid smoke with a resin used for the inner layer of a
plastic casing. This has been unsuccessful for a number of reasons
including reaction and volatilization of the liquid smoke at
extrusion temperatures and delamination induced by the presence of
the additive.
[0015] Another approach has been to incorporate an absorbent
additive into an impermeable plastic casing material. However, such
a product has yet to be adopted commercially and in tests conducted
by the present inventor on one such material, have shown that there
is still insufficient absorption of liquid into the film and excess
liquid remains on the surface of the film.
[0016] If this excess liquid is not removed, the colour and flavour
additives do not remain evenly dispersed on the film surface during
subsequent processing such as shirring and stuffing. The result is
non uniform transfer of colour and flavour to the surface of the
product.
[0017] If the excess liquid is removed by wiping, very little of
the colour and flavour additives remain absorbed in the film
structure and little or no colour and flavour is transferred to the
product surface.
[0018] If the casing is in the form of a flat sheet the excess
liquid may be removed by applying heat to dry off the moisture
leaving the colour and flavour additives as a coating on the film
surface. However, heating may be difficult or not possible if the
film is a heat shrink film. The casing can then be formed into a
tube to encase the food product. A delicate balance is required to
have the coating adhere sufficiently to the casing surface to
withstand shirring and stuffing operations and yet release to the
surface of the food product during processing.
[0019] If the casing is in the form of a tube, the liquid
containing colour and flavour solution can be added to the inside
of the tube by well known techniques known as slugging but there is
no practical method to remove the excess liquid. Therefore
sufficient flavour and colour cannot be added without non-uniform
transfer to the product surface.
[0020] It will be appreciated that in other applications unrelated
to the food industry, it may also be desirable to provide an
alternative to those materials currently used in applications where
it is desirable to have a liquid at least partially absorbed
therein. It is therefore an object of the present invention to
provide a film having a liquid at least partially absorbed therein
and a method for producing such a film that may at least partially
overcome the above disadvantages, or provide the public with a
useful or commercial choice.
DESCRIPTION OF THE INVENTION
[0021] In a first aspect of the present invention, there is
provided a film having a surface with a liquid at least partially
absorbed therein, whereby prior to the liquid being applied to the
surface, the surface has been subjected to a surface activation
treatment such that the surface has a surface activity of at least
about 50 dynes.
[0022] The present invention relates to the surprising and
unexpected discovery that by subjecting a surface of a film to a
surface activation treatment, the surface may be coated with a
layer of a liquid such that the liquid solution is at least
partially absorbed into the film.
[0023] At least partially absorbed in to the surface is to be
understood to mean that there is at least some impregnation of the
liquid into the surface as opposed to a coating which remains on
the surface.
[0024] According to a further aspect of the present invention,
there is provided a method of preparing a film having a liquid at
least partially absorbed therein, the method including the steps of
subjecting a surface of the film to a surface activation treatment
such that the surface has a surface energy of at least about 50
dynes, applying a liquid to the surface such that the liquid is at
least partially absorbed into the film.
[0025] The film of the present invention may be any suitable film
for the desired end use. Preferably, the film is for packaging a
food product. More preferably, the film is a cook-in film. The film
is formed from one or more polymeric materials, present in one or
more layers. The polymeric material may be any suitable material
which may be processed as a film in either mono-layer or
multi-layer configuration. The polymeric material may be a
synthetic or non-synthetic polymer or a mixture or blend thereof.
Suitable materials for use in multi-layer films for food packaging
applications include a food contact layer and one or more other
layers selected from sealant layers, abuse layers, bulk layers,
oxygen barrier layers, moisture barrier layers, tie layers and the
like. The nature of these additional layers forms no part of the
present invention. Those of ordinary skill in the art are aware of
suitable polymers and blends thereof for use in the construction of
food packaging films. Typical materials are known in the art and
include polyolefin materials such as low density polyethylene,
linear low density polyethylene, high density polyethylene, and
higher alpha olefins such as polypropylene, polybutylene; ionomer
resins, olefin copolymers with vinyl monomers such as ethylene
vinyl acetate, ethylene acrylic acid or blends thereof; polyvinyl
chloride, polyvinylidene chloride, polystyrene and blends and/or
copolymers thereof.
[0026] An especially preferred material for the surface activation
treatment is a hydrophilic material such as a polyamide material.
Suitable polyamides are known in the food packaging art and include
aliphatic polyamides such as homopolycondensates of aliphatic
primary diamines having, in particular, 4 to 8 carbon atoms and
aliphatic dicarboxylic acids having, in particular, 4 to 10 carbon
atoms and blends or mixtures thereof. The aliphatic copolyamide may
be the same homopolycondensate or homopolymer, and may be a polymer
based on one or more aliphatic diamines and one or more aliphatic
dicarboxylic acids and/or one or more omega-aminocarboxylic acids
or omega-aminocarboxylic lactams. Examples of suitable dicarboxylic
acids include adipic acid, azelaic acid, sebacic acid and dodecane
dicarboxylic acid. The film may also include an additive to
facilitate adherence or absorption of the liquid. Suitable
additives may include water soluble or water swellable materials
such as starches, celluloses including alpha cellulose, poly
ethylene oxides, poly vinyl alcohol, polycyclic acid, crosslinked
polyvinylpyrrolidone (PVPP) and polyvinylpyrollidone (PVP)
copolymers, mixtures and blends thereof. A preferred material is
PVP or PVPP.
[0027] The surface of the film may also be treated to increase the
surface area thereof. Such methods of surface treatment are known
and include ablation and etching. Alternatively, the surface may be
roughened during extrusion by a number of methods including
extruding through a roughened die, or setting the melt and die
temperatures so as to create a non-uniform or turbulent flow.
Alternatively, the polymer may be blended with additives that can
promote melt fracture or modify flow. On the other hand, in some
cases, processing aids are added to control melt fracture. The
levels of these aids may be reduced or modified to give the desired
effect.
[0028] For some applications such as food packaging, the film is
heat shrinkable such that it may conform tightly to the food
product. The film may be a cook-in film in which case it shrinks
during cooking. Alternatively, the film may be shrunk prior to
packaging the food product by placing the package in a heated
environment.
[0029] Typically, for food packaging purposes, the film is in the
form of a seamless tubular casing. Such casings may be prepared by
methods known in the art. Alternately, the film may be formed as a
single sheet, surface activated, coated and then formed into a tube
by sealing the edges together. The process to form a single sheet
into a tube by sealing is well known in the art and is known as
back seaming. It is used on form and fill machines.
[0030] The surface activation treatment may be any suitable
treatment method such as plasma, flame, corona discharge, UV
irradiation, electron beam irradiation, gamma irradiation and the
like. The surface may also be treated chemically by subjecting the
surface to oxidizing or etching agents. A preferred treatment is
corona discharge.
[0031] It is known to treat a polyolefin material by corona
discharge so as to improve the wettabilty of the surface so as to
facilitate printing. Typically the polyolefin is treated to
increase the surface energy from about 30-32 dynes up to about
37-40 dynes. The power levels required to provide such increases in
dyne level depend to some extent on the nature of the material to
be treated and any additives therein. Different materials may react
differently. For example, polyesters are known to require
relatively low power levels of from about 8 to 11 W-m/M.sup.2,
whereas polypropylene requires relatively "high" levels of about 22
to about 27 W-m/M.sup.2. Higher corona treatment levels are
considered to be undesirable as it is believed there is a breakdown
of the polymer surface and release of low molecular weight products
which actually reduces the ability of the surface to bond to an ink
or the like.
[0032] Treatment of a polyolefin layer that forms an interior
surface of a tubular food casing by corona discharge is also known.
The purpose of such treatment is to improve the meat adherence
properties of the surface. Typically polyethylene is treated such
that the surface energy of the film is increased to between about
40 to 50 dynes. A certain degree of adhesion to meat is desirable
to avoid purge. However, excessive adhesion is also undesirable as
the film does not release cleanly from the meat surface and part of
the meat is pulled away from the film. This results in a scarred
and unsightly appearance. Excessive adhesion is typically observed
where the surface activity of the film exceeds about 50 dynes.
Corona treatment of the interior surface of a tubular casing has
been described in U.S. Pat. No. 5,296,170. Polyamide casing
materials which have a surface energy in the order of up to about
45 dynes generally have sufficient meat adherent properties and
corona treatment is not required. It is believed that if a
polyamide was corona treated, the resulting film would adhere
excessively to a meat surface, causing the above-mentioned
problems.
[0033] Surprisingly it was discovered that when the corona
treatment level was increased well above known commercial use, a
liquid could be absorbed into the film. Further where the film was
a cook-in food packaging article, the film did not unduly adhere to
the meat surface.
[0034] It will be appreciated that the level of surface treatment
to which a surface is subjected will vary depending upon the nature
of the substrate and the surface activation treatment and the
amount of the liquid to be absorbed. The necessary level of
treatment for a particular substrate may be determined by a person
of skill in the art. Typically, the surface is treated so as to
provide a coating absorbed level of at least about 0.40 and up to
about 10 mg/cm.sup.2, preferably at least about 1.0-3.0
mg/cm.sup.2. Where the surface is treated by corona treatment, the
surface is typically treated at a Waft density of between about 50
to about 1000 watt/min/m.sup.2, most preferably from about 100 to
about 600 watt/min/m.sup.2. The film may be treated with one or
more sets of electrodes in series. The total watt density may be
split as desired between the electrodes.
[0035] The liquid may be any suitable liquid depending upon the
desired end use. It will be appreciated that the term liquid refers
to any flowable material and includes pure liquids, aqueous or
non-aqueous mixtures, suspensions, emulsions, solutions and
compositions which may or may not contain solids such as suspended
particulate materials.
[0036] Typically, the liquid includes additives which may either
modify the properties of the film and/or be transferred to an
article in contact with the film. For example, in therapeutic
applications, the additive may be a therapeutic agent such as a
drug, vitamin, conditioning agent or the like.
[0037] Where the film is for use in food packaging, the liquid
typically comprises a colouring and/or flavouring agent with
optional additives such as binders, gelling or thickening agents,
surfactants and the like. Preferably, for cook-in purposes, the
colouring agent is of the type that reacts with proteins in food by
the Maillard reaction, which produces a brown colour characteristic
of smoked meat. The Maillard reaction may also imparts a smoky
flavour to a food. Maillard reagents may be considered to be both a
coloring and a flavoring agent. Compounds that react with proteins
in this manner are active carbonyl compounds such as
hydroxyacetaldehdye and reducing sugars such as fructose, glucose,
ribose, lactose, xylose and the like. In the present specification,
the general term "Maillard Reagent" will be used to refer to any
one or more of such compounds. Preferred Maillard type colouring
agents are liquid smoke or colouring agents available under the
tradename Maillose as available from Red Arrow. The Maillose agents
are formed from pyrolysis of sugars and starches. Liquid smoke is a
collection of condensable products from pyrolysis of wood or
cellulose. Liquid smoke includes active carbonyl compounds with
hydroxyacetaldehdye typically being the major carbonyl product.
Especially preferred colouring agents are those that comprise a
relatively concentrated amount of a Maillard reagent. Especially
preferred is a colouring agent comprising between about 20 wt % to
about 40 wt %, most preferably between about 30 wt % to about 35 wt
% hydroxyacetaldehyde.
[0038] Other colouring agents may be used instead of, or in
addition to, the Maillose type colouring agents. Such further
colouring agents are well known in the art and include caramel,
beet extract, malt and bioxin.
[0039] Especially preferred compositions are currently under
development by Red Arrow. Such compositions include at least one
viscosity modifying agent, a surfactant and a Maillard type
coloring agent. Viscosity modifying agents suitable for use in
contact with food are well know in the art and include materials
such as cellulose, methyl cellulose, hydroxypropyl cellulose,
starch, chitin, carrageenan, konjac, guar gum, xanthan, alginic
acid and derivatives thereof, agar, pectin, gelatine and the like.
Preferred viscosity modifying agents are water-soluble cellulose
ethers such as, methylcellulose, hydroxypropyl methylcellulose,
hydroxypropylcellulose, ethyl methylcellulose,
hydroxyethylcellulose, ethyl hydroxyethylcellulose and preferably
the anionic water-soluble cellulose ethers such as,
carboxymethylcellulose and carboxymethyl hydroxyethylcellulose.
Mixtures of water-soluble cellulose ethers may also be employed.
Particularly preferred cellulose ethers are the methyl cellulose
ethers under the trade name Methocel. Typically, the composition
includes up to about 2.0 wt %, preferably up to about 1.0 wt % of a
viscosity modifying agent.
[0040] A preferred composition includes between about 0.05 to about
0.5%, most preferably between about 0.125 and 0.25 wt % of a
viscosity modifying agent.
[0041] Typically, the composition includes one or more surfactants.
Suitable surfactants include calcium stearoyl lactylate,
diglycerides, dioctyl sodium slilfosuccinate, hydroxypropyl
cellulose, lecithin, monoglycerides, polysorbate 60, 65, and 80, a
glycol such as propylene glycol, sodium hexametaphosphate, sodium
lauryl sulfate, sodium stearoyl lactylate, sorbitan monostearate,
or mixtures thereof.
[0042] An especially preferred composition includes a Maillard type
colouring agent in combination with a methylcellulose and a glycol
such as propylene glycol, preferably up to about 10 wt %, more
preferably up to about 5 wt % glycol.
[0043] The composition may also include optionally other additives
such as anti-oxidants and stabilizers.
[0044] It will be appreciated that the type of and amount of the
components of the liquid composition may be selected according to
the nature of the surface and also the food to be packaged therein.
Consideration may be given to a desirable colour or flavour profile
of different meat products with a view to consumer acceptance.
[0045] Alternatively, or in addition to the colouring or flavouring
agents, the liquid may also include an antimicrobial agent, an
antibacterial agent, a fungicide and/or an antiviral agent. It will
be appreciated that incorporation of such agents need not be
limited to use in food packaging and may have other
applications.
[0046] The liquid may also consist essentially of water. The
present inventor has surprisingly observed that when films which
are typically quite stiff are treated according to the method of
the present invention, the amount of water which may be absorbed is
sufficient to alter the physical properties of the film such that
the film is soft and pliable. An application of a softer film is in
the food packaging industry where food products are stuffed into a
tubular casing prior to being placed in a metal mould, which is
typically of a square or rectangular cross section. Foods packaged
and cooked in this way are referred to as moulded products. The
flexibility of the film allows the film to conform to the shape of
the mould. On the other hand, for some applications such as
stuffing (where a food product is injected into a tubular casing
and cooked to provide a product of circular cross section) a film
having less flexibility may be desired.
[0047] The degree of flexibility may be controlled or modified by
controlling the amount of liquid absorbed and/or formulating the
film to provide at least two layers, a first layer into which the
liquid is to be absorbed and a second water impermeable or barrier
layer. It will be appreciated that such films may also include
other layers. An example of such an arrangement is a film for use
as a food packaging film having an inner layer of a hydrophilic
material such as a polyamide material and a layer of a polyolefin
material such as polypropylene, polyethylene or LLDPE.
[0048] The liquid may be applied to the surface by any suitable
technique such as soaking or spraying. A suitable process for
tubular casings is known in the art as slugging. Slugging is
described in U.S. Pat. No. 3,378,379 and is used to apply a coating
to absorbent cellulose casings. The conventional slugging method
for coating the inside of a casing involves filling a portion of
the casing with the coating material, so that a "slug" of material
generally resides at the bottom of a "U" shape formed by the casing
and then moving a continuous indefinite length of casing so that
the slug of coating material remains confined within the casing,
while the casing moves past the slug and is coated on its inside
wall by the coating material contained within the slug. The film
then passes between a pair of cog rollers.
[0049] Preferably, a modified slugging process is used to apply the
liquid to the surface in which the slug is trapped between an upper
and lower pair of nip rolls. The upper set of rolls preferably
includes a chrome plated roller and a rubber roller. The rubber
roller typically has a hardness of between about 60 to about 120,
typically between about 70 to about 100 durometer. As the tube
passes between the two sets of rolls, liquid is carried with the
tube and the upper set of rolls act as metering rolls. In the
embodiment of the invention, where the liquid consists essentially
of water, it is preferred that the water include a viscosity
increasing agent. Increasing the viscosity facilitates passage of
the liquid towards the upper set of rolls.
[0050] Preferably the gap between the roller is set at less than
the thickness of the tube, typically at about 50%. This is in
contrast to conventional coating techniques where the gap is set
equal to the tube thickness plus the desired thickness of the
coating layer. Whilst not wishing to be bound by theory, it is
believed that the pressure created as the tube passes between the
rollers assists in forcing the liquid into the walls of the film.
Typical levels of absorption are in the order of 20 to 35% by
weight.
[0051] Food casings composed of the film of the present invention
may be provided in any of the forms known in the art, such as in
the form of shirred casing sticks, discrete short segments of
flattened casings, continuous lengths of flattened casing on a reel
and the like.
[0052] Where the film is in the form of a tubular casing, the tube
is typically shirred after application of the liquid. Shirring may
be accomplished by conventional shirring techniques as well known
to those of skill in the art.
[0053] According to a further aspect of the invention, there is
provided a shirred tubular food casing having an inner food contact
surface coated with a liquid composition comprising at least one
food additive for transfer to a food product encased therein,
whereby prior to application of the composition to the surface, the
surface has been subjected to a surface activation treatment.
[0054] After application of the liquid, the film may be used to
package a food product by any suitable means. Where the package is
in the form of a tubular casing or a shirred casing, the casing may
be stuffed by pushing a meat product through a stuffing horn into
the inside of the tubular casing.
[0055] A food product packaged within the film of the invention may
be cooked by any suitable method such as boiling, heated by steam,
or placed in an oven. Preferably, the packaged food is cooked as
soon as possible after packaging. Alternatively, the packaged food
product may be subjected to a pre-heating step so as to fix the
colour prior to cooking. For example, the packaged product may be
pre-heated to a temperature of between about 150.degree. F. and
about 200.degree. F. for a period of up to about 6 minutes. During
cooking, the food colouring additive can impart a colour to the
surface of the food.
[0056] According to a further form of the invention, there is
provided a method of processing a food product, the method
including packaging the food product within a film of the first
aspect of the invention which includes a colouring agent and
heating the packaged article to a temperature at which colour from
the colouring agent is transferred to the surface of the food
product.
BRIEF DESCRIPTION OF THE FIGURES
[0057] FIG. 1 shows a photograph of a ham packaged in a film of the
invention as compared to a control ham;
[0058] FIG. 2 shows a photograph of a turkey product packaged in a
film of the invention as compared to a control turkey;
[0059] FIG. 3 shows a SEM of a film designated DC-1 AD-1;
[0060] FIG. 4 shows a SEM of the film of FIG. 3 impregnated with a
colouring composition, FIG. 5 shows a SEM of the film of FIG. 3
after methanol extraction; and
[0061] FIG. 6 is an SEM of the film of FIG. 4 after methanol
extraction.
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLE 1
Coating Formulations
[0062] Coating formulations were prepared by Red Arrow according to
Table 1.
TABLE-US-00001 TABLE 1 Coating Coating Composition Code component
wt % C/C.sub.3/02/ Maillose 45 .sub.1. 94.63 C.sub.1/03 Propylene
Glycol 5.00 Dioctyl Sulfosuccinate 0.25 Xanthan Gum 0.12 C.sub.x
Liquid smoke .sub.3. 100.0 C.sub.7 Maillose 45 94.875 Propylene
Glycol 5.00 Methocel .sup.2. SGA16M 0.125 C.sub.9 Liquid smoke
94.875 Propylene Glycol 5.00 Methocel SGA16M 0.125 C.sub.20
Maillose45 98.4 Propylene Glycol 1.4 Methocel K 100M 0.2 C.sub.21
Liquid smoke 98.4 Propylene Glycol 1.4 Methocel K 100M 0.2 .sub.1.
Maillose 45 contains 27 wt % hydroxy acetaldehyde, is a colourant
available from Arrow Products Co. LLC, Manitowoc, WI and formed by
the pyrolysis of sugars. .sup.2. Methocel is methyl cellulose
available from Dow. .sub.3. Liquid Smoke is a concentrated liquid
smoke product having hydroxy acetaldehyde content of between about
30 to about 35 wt % and is available from Red Arrow Products Co.
LLC, Manitowoc, WI.
EXAMPLE 2
Corona Treatment of a Polyamide Film
[0063] The following trials were conducted with a three layer heat
shrinkable tubular film having an outer polyamide layer, an
intermediate polypropylene copolymer layer and an inner polyamide
layer. The inner layer is a blend of nylon 6 and about 16% PVPP.
This film will be referred to hereinafter as DC-1.
[0064] The tubular film was internally corona treated at 600 W
using an electrode arrangement similar to that as described in U.S.
Pat. No. 5,296,170 in which one of a pair of electrodes is placed
in contact with one side of an inflated tube. In this way, a corona
discharge is generated in the air space within the tube. However, a
significant difference between the method as described in U.S. Pat.
No. 5,296,170 is that in the present case, much higher power levels
are used. Although U.S. Pat. No. 5,296,170 does not describe the
power level in watt density, the examples show an increase in dyne
level of a polyethylene film from 31 dyne to 42 and 41 dyne.
However, it may be estimated from this change in dyne level that a
power of between about 18 and 23 watt was used. After corona
treatment, the interior surface of the film was coated by slugging
as described below:
[0065] 1. The tube is slit open and an amount or "slug" of the
liquid is added.
[0066] 2. Air is injected to form the tube into a cylindrical shape
and the slit is sealed with a tape.
[0067] 3. The tube is advanced through and partially collapsed
through a set of coating rolls. The rolls include a 72 durometer
rubber roll and a chrome plated roll. The spacing between the
coating rolls is adjustable such that the rolls are not totally
closed and the gap is about 50% of the tube width. As the film with
the liquid passes through the rolls, most of the liquid is squeezed
out.
[0068] 4. The film with the film absorbed on the inside surface is
then wound into reels.
[0069] The level of surface activation was estimated by measuring
the surface energy in dynes. The results are summarized in Table
2.
TABLE-US-00002 TABLE 2 Corona Dyne Watt- Add-on* Delta Add-on
Treatment level min/m2 Mg/cm.sup.2 mg/cm2 Increase % None 52 0 0.40
0 0 Yes 55** ca76 0.46 0.06 15 Yes 66-70 228 0.67 0.27 67.5 *The
amount of coating retained was measured by weighing the film before
and after coating. **A film treated to this level is referred to as
DC1-AD1 hereafter. This film had been corona treated by a
conventional corona treater used to treat tubular casings (as
described in U.S. Pat. No. 5296170) to the maximum power available.
It is estimated from the measured dyne level that the watt density
was in the order of 75 Watt-min/M.sup.2.
[0070] The coating used was Coating C1, the components of which are
provided in Table 1.
[0071] The results in Table 2 show a 67% increase in the amount of
solution that can be absorbed into the inner layer. and that the
amount of coating that can be absorbed into the inner surface of
the film was directly related to the level of corona treatment.
[0072] In the experiments it was observed that the surface
activation was so high, that the dyne level was outside of the
usual dyne measurement techniques. For this reason in future tests
the level of surface activation was estimated in terms of watt
density.
[0073] Waft density is calculated according to the following
formula:
Watt density = power supply ( watts ) Width of tube ( M ) .times.
line speed ( min / M ) ##EQU00001##
[0074] It may also be appreciated by a person of skill in the art
that the above dyne levels are well in excess of that achieved by
corona treatment as used to facilitate meat adhesion. It is
generally accepted that level of between 40 to 50 dynes provide
acceptable meat adhesion. It is also generally accepted in the
field that if films are treated to a dyne level above about 50 dyne
that the film unduly adheres to the meat surface. In the present
instance it was surprisingly observed that despite these high
levels of surface activation and contrary to expectations the meat
film released cleanly from the meat surface without meat
scarring.
[0075] To further demonstrate that the amount of liquid that can be
absorbed into a polyamide film is a function of the corona
treatment the film used in the tests of table 1 was treated to two
different corona levels. Moisture was then applied to the film and
the amount of moisture absorbed was determined per ASTM 570. This
test requires specimens to be conditioned in an oven for 24 hours
at 50.degree. C. cooled in a desiccator, then immediately weighed
to the nearest 0.001 g. After conditioning, the test specimens were
immersed in distilled water that was maintained at room temperature
(23+-1 C) for 72 hours. After the end of the test, the specimens
were removed from the water, all surface water was wiped off with a
dry cloth, and then weighed immediately to the nearest 0.0001
g.
[0076] To calculate the percentage increase in weight during
immersion, the following equation was used:
Increase in weight , % = ( Wet weight - Initial weight ) Initial
weight .times. 100 ##EQU00002##
[0077] Table 3 show the results of the test.
TABLE-US-00003 TABLE 3 Test Casing Type % Weight Gain W-m/M.sup.2 1
DC-1 (no corona) 12.9 -- 2 DC1-AD-1 14.7 About 75 3*** DC1-AD-1
18.7 189.3 ***For test 3 the film of DC1-AD-1 the inner surface was
further treated to the level indicated. It is estimated that the
dyne level is 70 or higher at the watt density indicated but at
these levels the dyne test cannot be used with any reliability.
[0078] results indicate that corona treatment increases the amount
of moisture that is absorbed as the corona level is increased.
[0079] To demonstrate that a solution that contains smoke colour is
also absorbed when applied to the inner surface of the film the
following test was devised:
[0080] Film samples were cut to fit circular hoops similar to those
used to hold cloth when doing needle point. The inner surface of
the film was placed in the hoop so that the rim of the hoop and the
film formed a container. Before the film was clamped into the
hoop.
[0081] The film specimens were clamped into the hoops. A solution
that contains Maillose (C20) was added to the inner surface of a
film of the structure polyamideltie/polyamide. (This film will be
referred to hereinafter as V9). The solution was added to just
cover the surface of the film. This method insures that only the
inner surface of the film has solution applied and closer simulates
the slugging process. The specimen was left in contact with the
solution for 72 hours.
[0082] The excess solution was poured from the hoop, the specimens
were removed from the hoop and, all surface solution was wiped off
with a dry cloth. The specimens were heated to 250 F for 30 minutes
and then weighed to the nearest 0.0001 g.
Table 4 summarizes the results obtained for this test.
TABLE-US-00004 TABLE 4 Material Treatmentw-min/m2 Absorption %
V9-control 0 23.9% V9-50 50 28.6% V9-100 100 30.4% V9-150 150 37.0%
V9-200 200 33.1% V9-250 250 32.2% V9-300 300 30.6% V9-400 400 30.1%
V9-500 500 31.4%
[0083] The results indicate that as the internal coronal level was
increased the amount of solution that was absorbed also
increased.
EXAMPLE 3
Shirring Stuffing and Processing
[0084] Films were activated and compositions applied thereto in a
manner as described in Example 2. The films, after allowing time
for the coating to attach and/or be absorbed onto the rolls were
shirred into "sticks". Shirred tubular casings may be prepared by
conventional shirring machines as known in the art.
[0085] Ham or turkey meat products were then pushed through a
stuffing horn into the shirred casings.
[0086] The encased food products were then cooked by heating in an
oven, with steam or hot water set for a length of time for the
product to reach an internal temperature of 160 F. The oven was
maintained at 100% relative humidity and a temperature of 185 F.
The steam and hot water temperatures are noted in Table 3. Cooking
was conducted as soon as practicable and at various times after
stuffing as noted.
[0087] Controls were conducted in the absence of corona treatment
and impregnation.
[0088] The results are summarized in Table 5.
TABLE-US-00005 TABLE 5 Product Composition Treatment Add On %
increase in Colorimetric Type Code Colourant Film Type Inner Layer
W-M/m2 mg/cm2 weight of film* L Value Comments Bologna C.sub.20
Maillose DC-1 AD-1 Nylon + PVPP 318 0.67 26.35 53.21 Uniform dry
golden mahogany Bologna C.sub.21 Liquid Smoke DC-1 AD-1 Nylon +
PVPP 309 0.76 29.99 54.48 Uniform dry golden brown Bologna None
None DC-1 AD-1 Nylon + PVPP None 0 0 65.57 Uniform dry pale tan.
Ham C.sub.9 Liquid Smoke DC-1 AD-1 Nylon + PVPP 102.6 1 39.33 56.62
Moulded 165.degree. F. Water Ham C.sub.9 Liquid Smoke DC-1 AD-1
Nylon + PVPP 102.6 1 39.33 53.18 Moulded 195.degree. F. Water Ham
None None V-1 Control LLDPE None 0 0 65.13 Moulded 165.degree. F.
Water Turkey C.sub.3/02 Maillose DC1 AD-1 Nylon + PVPP 300 0.42
16.62 67.4 Uniform, light colour Turkey None None V-1 Control LLDPE
None 0 0 75.1 Uniform, light colour Turkey C.sub.7 Maillose DC1
AD-1 Nylon + PVPP 216.2 0.84 33.04 61.56 Processed immediately
185.degree. Steam Turkey C.sub.7 Maillose DC1 AD1 Nylon + PVPP
216.2 0.84 33.04 69.78 Held 4 hours 185.degree. Steam Turkey
C.sub.1/03 Maillose DC1 AD1 Nylon + PVPP 289 0.82 33.04 67.99 1
Minute Hot Water Held 4 hours 185.degree. Steam Turkey C.sub.1/03
Maillose DC1 AD1 Nylon + PVPP 289 0.82 33.04 62.3 3 Minute Hot
Water Held 4 hours 185.degree. Steam Turkey C.sub.1/03 Maillose DC1
AD1 Nylon + PVPP 289 0.82 61.8 6 Minute Hot Water Held 4 hours
185.degree. Steam Turkey None None V-1 Control LLDPE None 0 0 75.47
Turkey Cx Liquid smoke DC1 AD1 Nylon + PVPP 256 1.4 64.19 Turkey C9
Liquid Smoke DC-1 AD-1 Nylon + PVPP 102.6 1 39.33 65.6 Moulded
165.degree. F. Water Turkey C9 Liquid Smoke DC-1 AD-1 Nylon + PVPP
102.6 1 39.33 63.38 Moulded 195.degree. F. Water Turkey None None
V-1 Control LLDPE None 0 0 75.94 Moulded 165.degree. F. Water Ham
C9 Liquid smoke V-1 control LLDPE 0 0 0 64.99 Ham C9 Liquid smoke
Visflex Nylon 616.0 0.85 57.61 Ham C9 Liquid Smoke V9-2 Nylon 616.0
0.80 56.37 Ham C9 Liquid Smoke AD-1 Nylon + PVP 200.00 0.80 31.36
55.89 Ham Sun products Absorbent None None 52.79 Moulded Fibrous
165F. cellulose water Ham C9 Liquid Smoke AD-2 Nylon 308 0.93 51.40
L value-The lower the number, the greater the Colour density *The %
weight increase of the film was calculated from the add on
according to the formula: % weight increase = add on .times. 100 wt
1 cm 2 ( 2.5423 mg ) ##EQU00003##
[0089] Visflex is a commercially available film from Viskase and
has the structure: nylon/EVA/nylon.
[0090] V9-2 is a commercially available film from Vector and has
the structure: nylon/tie/nylon.
[0091] V1 is a commercially available film from Vector and has the
structure: nylon/tie/LLDPE.
[0092] Sun Products is a commercially available absorbent
plastic/cellulose laminate casing having a colorant solution
absorbed therein.
[0093] It was discovered that the final colour transferred to the
product is affected by the time between stuffing and processing. It
is believed that this is because the heat of processing sets the
colour on the product surface. If held before processing the colour
compounds are absorbed into the meat product.
[0094] It was also observed that when the process was run without
surface treatment that excessive pooling occurred above the upper
coating rolls and liquid collected at low points of the tube.
Further, the coated surface was wet to the touch and it was
possible to wipe liquid from the surface. Although there was some
add on and some color was transferred to the meat product, in
practice the color transfer was streaky and quiet unacceptable
indicating a non-uniform coating onto the surface. This non-uniform
coating was insufficiently absorbed so as to be resistant to the
subsequent shirring and stuffing operations. On the other hand,
when the tube was corona treated, no pooling was observed. Also the
inner surface of the tube did not feel wet, nor was it possible to
wipe off any liquid from the treated surface. It is believed that
these observations support the belief that the liquid is at least
partially absorbed into the surface and not present as a discrete
coating.
[0095] FIG. 1 shows a photograph of a ham packaged in a film of the
invention as compared to a control ham.
[0096] FIG. 2 shows a photograph of a turkey product packaged in a
film of the invention as compared to a control turkey.
[0097] These figures show that both the ham and turkey products
cooked in the film of the invention have a uniform smoked brown
colour. Uniformity of colour indicates that the composition can not
only be uniformly absorbed into the surface but this uniformity is
resistant to disruption by the shirring and stuffing procedures.
The absorbed liquid also has exhibited the flexibility to stretch
during stuffing and shrink during heat shrinkage of the film. Still
further, there is no evidence of purge, or cook-out, or an
unacceptable adherence of the film to the meat product.
EXAMPLE 4
SEM Studies
[0098] In order to further investigate the absorption
characteristics of a treated film scanning electron microscope
studies were conducted on DC1, and DC1-AD-1 which had been treated
to a power level of about 300 W-min/M.sup.2 and composition C7
applied to the treated surface. Initial results showed that the
principal difference between untreated and absorbed film was that a
10 micron thick porous inner layer with irregular surface
morphology was changed into a 5 micron thick porous layer and a 5
micron thick nonporous innermost layer with irregular surface
morphology. This indicated that the composition had absorbed into
the inner film layer and impregnated the inner layer to a depth of
about Y2 the original thickness.
[0099] To confirm this, further SEM analysis was conducted on water
and methanol extracted DC-1 AD-1 before and after liquid
application to the inner surface. The results of the water and
methanol extracted impregnated samples showed that extraction with
water and methanol left physical demarcations on morphologies of
impregnated film layers at approximately half the depth of their
original cross sectional thickness. Exemplary SEM micrographs taken
at 1000.times. magnification are shown in FIGS. 3,4,5 and 6 which
show unimpregnated, impregnated, methanol extracted unimpregnated
and methanol extracted impregnated films respectively.
[0100] It can be seen that the film and method described above, can
provide a film saving a significant amount of a liquid absorbed
therein. The tubular casing of the preferred embodiment is able to
have a liquid applied evenly thereto. Further the tubular casing is
able to undergo shirring, stuffing and cooking operations so as to
provide an even transfer of additive to a food surface.
[0101] It will be appreciated that various changes and
modifications may be made to the invention described herein without
departing from the spirit and scope thereof.
* * * * *