CA1053497A - Food film wrap - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A packaging film wrap useful in preserving food substances containing oils, fats and chromoproteins is dis-closed having a synergistic preserving mixture on the film surface wherein the mixture is contained in a carrier substance and consists of at least one antioxidant and an antimicrobial agent. The antioxidant is preferably ascorbic acid or isoascor-bic acid and the antimicrobial agent is preferably a mixture of methyl and propyl esters of parahydroxybenzoic acid, wherein the weight ratio of the antimicrobial agent to the antioxidant is within the range of 1:1 to 5:1.

Description

~ ` 10534~7 , .
;~ ABSTRACT OF THE DISCLOSURE

A packaging film wrap useful in preserving food substances containing oils, fats and chromoproteins is dis-closed having a synergistic preserving mixture on the film surface wherein the mixture is contained in a carrier substance and consists of at least one antioxidant and an antimicrobial ., ,~ agent. The antioxidant is preferably ascorbic acid or isoascor-'~ bic acid and the antimicrobial agent is preferably a mixture .`
of methyl and propyl esters of parahydroxybenzoic acid, wherein the weight ratio of the antimicrobial agent to the antioxidant ; is within the range of 1:1 to 5:1.

BACKGROUND OF THE INVENTION

~ During recent years there has been a great deal of ,~ development in the art of packaging such food items as meats, :
` poultries, vegetables and dairy products for the purpose of ,; attractively displaying and additionally preserving such food ~.
items while on display at various food stores.
~ It has been known to use such antioxidant agents -,~ as ascorbic acid or isoascorbic acid in the specific preser-vation of the color of food products. For example, U.S. Patent No. 2,906,646 to Smith et al discloses the use of ascorbic acid as an antioxidant useful in preserving such food substances.
It is also disclosed that benzoic acid esters can be used in combination with such antioxidant substances on food wrapping materials. U.S. Patent No. 2,979,410 to Parlour discloses the use of isoascorbic acid as a fungicidal agent as well as an antioxidant on food film wrappings for preserving meats.
Additionally, U.S. Patent No. 2,858,225 to Gooding et al discloses a package treating process in which the wrapper material is impregnated with a fungistat of low-volatility : ` 1053497 to render the package wrapper useful in preventing spoilage of various food products due to the growth of molds on the surface of such products. A specific fungicidal agent mentioned is -` parahydroxybenzoic acid. Also, U.S. Patent No. 3,134,687 to Luck discloses a preservative packaging material having calcium sorbate incorporated into a polyvinyl alcohol carrier substance.
Disclosure of various antioxidants useful in food preservation are provided in U.S. Patent Nos. 2,709,657 to Campbell, 2,843,497 ;

to Stuckey et al and 3,052,553 to McKillip et al.
It is to be noted that two separate mechanisms for spoilage of food substances containing oils, fats and chromo-~` proteins can occur either simultaneously or separately. In one . case, spoilage can occur due to the growth of microbiological contaminants such as bacteria, fungi, molds, mildew, etc. In ~ the other case, spoilage can additionally occur due to oxida-`` tion which causes certain chemical changes in the oily substances ~ .
` of the food product rendering them rancid or less desirable due to color change (e.g. the loss of red color in meats or meat products).

~;~ 20 SUMMARY OF THE INVENTION
':
` In an attempt to overcome such problems with respect to packaging food products, Applicant has surprisingly dis-covered that combinations of specific antioxidants and anti-microbial agents contained on a flexible packaging material are more effective as a food preserving composition than ` either of the ingredients taken separately. Specifically, a packaging film useful in preserving food substances containing oils, fats and chromoproteins is herein disclosed comprising a flexible substrate material having thereon a surface coating consisting essentially of 0.18-0.22 pounds per 1000 square feet of film surface area of a synergistic preserving mixture ~`
~- contained in a polyvinyl alcohol dispersion, said mixture ` consisting of:
;"
(a) at least one antioxidant seIected from the group consisting of ascorbic acid and isoascorbic acid;
and (b) an antimicrobial agent consisting of a blend of equal parts by weight of the methyl and propyl esters of parahydroxybenzoic acid, the weight ratio of said antimicrobial agent to said antioxidant ;; 10 falling within the range of about 1:1 to 5:1.
Preferably, the coating contains per 1000 square feet of sur-face area, 0.18 pounds of a mixture containing equal parts by weight of the methyl and propyl esters of parahydroxybenzoic acid and 0.04 pounds of ascorbic acid. Also, the substrate material is either polyethylene or polypropylene.

DETAILED DESCRIPTION OF THE INVENTION
Insofar as the particular types of antioxidant substances which have been found to be most useful, ascorbic acid and isoascorbic acid are preferred. Additionally, it has been found that the methyl and propyl esters of parahydroxy-benzoic acid are preferred as antimicrobial agents. Based upon experimental work conducted in using coatings of these ` materials in various combinations on flexible food packaging ; films, it has additionally been found that surprisingly effec-tive preserving mixtures are obtained wherein a concentration of 0.18 to 0.22 pounds per 1000 square feet of film surface area are used and the weight ratio of antimicrobial to anti-oxidant falls within the range of about 1:1 to 5:1.

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` 1053497 Since these parahydroxybenzoic acid esters are re-latively water insoluble, it has been found necessary to dis-perse them in combination with the relatively water-soluble ascorbic or isoascorbic acid in a carrier material which is water soluble and can act as a vehicle for transfer of the pre-serving mixture from the film wrap surface and ontothe food product surface which has a residual moisture content and is in :
contact therewith.
Although polyvinyl alcohol is the preferred car-rier material for the active preserving ingredients, other water-sensitive materials could be used, so long as they are capable of solubilizing the antimicrobials and additionally either sol-uble in water or exhibit some degree of sensitivity on contact ~`
- with water (e.g. is capable of becoming moistened or swellable).
~ ~.
Examples of other such water-sensitive materials are carboxy-methylcellulose, polyvinylmethyl ether, algins, alginates, cellulose gum, gelatin, gum arabic, gum acacia and the like.
Although there is no critical concentration for the carrier, it is inherently necessary that enough be present to effectively form on the film surface a coating dispersion containing the active preserving ingredients (i.e. the anti-oxidant and the antimicrobial agents).
Also, although polyethylene and polypropylene are preferred as the food wrapping materials or substrates, other useful flexible substrate materials can include regenerated cellulose, saran, rubber hydrochloride films, vinyl films, polystyrene, cellulose acetate, "Mylar" (polyethylene tereph-thalate produced by DuPont), trifluoroethylene films, cello-phane and various blends of polyvinyl chloride.

* Trade Mark - . ,, ~

` 1053497 Generally, the carrier and active preserving agents are initially dissolved in a solvent mixture to form a coating .~ .
material for application to the flexible substrate in pre-paring the packaging film. The coating can be applied by any of the conventional methods such as by dipping the substrate ~ in the coating composition in which case both sides of the ; film are coated. Another method for applying the coating to the `~A film is by spraying it on to a moving web of film. In this method, either one or both sides of the film are coated.
After application of the coating to the film, the solvents are evaporated by drying the coated film. Such drying may be effected by conventional means including heating or infra-; red radiation. After such drying, the film contains the carrier having dispersed therein the anti-oxidant and the anti-microbial agents. There is no criticality to the choice or . .,:
proportion of solvents so long as they aid in solubilizing the ~- carrier to promote the formation of the dry dispersion of ` the actives in the carrier when applied as a coating on a film.
. Typical solvents might include ethanol, and larger chain O ethers, p-glycol ethers, acetone, ethyl ether, propylene ,~ glycol, glycerol, water and mixtures thereof.
The following examples are provided to illustrate ? the present invention and should not be deemed as limiting the ` scope of which is defined by the appended claims. Generally, the coating composition can be applied at a rate which can : vary from about 0.1-4 pounds per 1000 square feet of film surface. Preferably, about 1 pound per 1000 square feet of film surface i6 used.

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~- A typical coating formulation is exemplified by the following:
Weight %
Deionized water (solvent)49.00 Polyvinyl alcohol (carrier)20.00 ~- Methyl ester of parahydroxy-(antimicrobial) 7.50 ; benzoic acid Propyl ester of parahydroxy- (antimicrobial) 7.50 benzoic acid Ascorbic acid (antioxidant) 3.00 . Ethanol (solvent)7.75 Propylene glycol (solvent)5.25 100. 00 `r`` Seven coated polypropylene films (Groups 1-7 below) were prepared using coating compositions having the following - weight percent of active ingredients in the coating composi-tion just prior to application to the films:
~ Weight % of 50/50 blend of .. 20 methyl and propyl esters of Weight %
Group parahydroxybenzoic acid Ascorbic Acid

2 22 0 ::;
' 18 `` 4 0 22 : 5 15 3 '`

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` 1053497 he eighth group represents uncoated polypropylene film. The ~ coating compositions were applied at the rate of 1 pound of '~ composition per 1000 square feet of film surface area, and after appropriate drying to remove solvents, there remained coatings on the eight film surfaces containing the initial concentrations of active ingredients contained in a polyvinyl alcohol dispersion.
Ten slices of boneless beef roast were individually wrapped using Group 1 coated film, refrigerated at 40F, and observed during a 14-day period while at room temperature (25C). None of the slices were opened until the final day of the test. The spoiled areas were determined by visual inspec-tion for color change, change due to putrification, darkening of the meat and slime formation. The individual slices were examined daily and at the first sign of any spoilage (denoted as any visual defect that would render the meat unfit for sale) on a particular piece, it was classified as spoiled. The meat ` slices had a relatively high initial bacteria count of 208,000 bacteria per square inch of meat surface. The same observa-tions were made for coated film Groups 2 7 and uncoated film :
` (Group 8), each group being used to wrap 10 slices of boneless beef roast having the same initial bacteria count. The results ` are given in Table 1 below.

Days of Stability Synergism2 Total Spoilage3 % of Area Spoiled4 Group at 25C (in days) (days) at 25C After lQ ~a~s~- 14 d;ays ; 1 5 3 9 36 83--

3 1 - 7 100%
spoilage after 9 days .; .

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r;: Stability Synergism2 Total Spoilage3 % of Area Spoiled4 `; Group at 25C (in days) (days)-at 25C After ~'. 10 days 14 days

4 1 - 7 100%
spoilage ~,: after 9 days , 4 2.5 9 54 88 "``~ 10 6 2 - 8 slices 25 43 spoiled after 10 days ~ 7 1 - 7 slices 33 49 :j spoiled .j~ 15 after 8 days :, .~- 8 1 - 4 100~ -(control) spoilage after ; 7 days ~20 Notes: 1- "Days of Stability" means number of days after p test begun when any meat slice showed any sign of ,.~.
spoilage within a group.
2- "Synergism" (S) is defined as S = A -1/2(B+C) wherein A is the stability of the wrapped meat where the film wrap coating contains the combina-`~ tion of the 50/50 blend of methyl and propyl esters .~
of parahydroxybenzoic acid and ascorbic acid; B
: is the stability of the wrapped meat where the .: film wrap coating contains only the 50/50 blend of esters in quantities equal to that of "A"; and C
represents the stability of the wrapped meat where the film wrap coating contains only the ascorbic acid in quantities equal to "A". - :
: 3- "Total Spoilage" means number of days after test :~
begun when all slices in a group showed any signs of spoilage.
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:, _.. 9.. _ . -4- "% of Area Spoiled" means percentage of total area of all meat slices in a group observed to be spoiled after indicated days.
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. EXAMPLE 2 The procedure of Example 1 was repeated except that six .
.: slices of meat were used per group and there were only 4 . groups having the following weight percent of active ingre-. dients in the coating composition just prior to application to the films:
: 10 Weight % of 50/50 blend of ` methyl and propyl esters of Weight ~
~: Group parahydroxybenzoic acid Ascorbic Acid 1 18 :0 , ~ .
.. 15 3 18 4 ~ 4 20 , .~ 5(Control) 0 '; The fifth group represents uncoated polypropylene film. Also, `: the initial bacteria count on the meat slices was approximately '.` 20 half that for Example 1. The results are given in Table 2 , below with the terms having the same meaning as previously ~: defined.
' TABLE 2 .:
Days of ~; 25 Stability Total Spoilage % of Area Spoiled :~ Group at 25C(days? at 25C After 10 days 14 days ` 1 5 13 48 75 ?'," ~ ~
?~; 2 6 9 36 73 .,:
` 3 8 14 5 48 .~ 30 4 4 10 72 98 :

: 5 1 4 92 100%
'-!- (Control) spoila~e -r after 11 days .~ .
'' ~ -- 1 0 --~?
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` 105349'7 It should be noted that the predominant mechanism for spoilage depicted in the results for Table 1 was probably due to bac-terial action rather than oxidation in view of the re~atively high initial bacteria count on the meat slices. Whereas, the ` S results in Table 2 reflected both oxidative spoilage of many of the beef slices (fading from red to a gray pork color) as well as bacterial spoilage, in view of the lower initial bac-teria count which was about one half that for Example 1. The films in Table 1 coated with both antimicrobial and antioxi-dant agents (e.g. Groups 1 and 5) did not appear to be quite as effective as those films containing only an antimicrobial (e.g. Groups 6 and 7), insofar as average percent of total area of meat slices spoiled over an extended period of time. How-ever, the films in Table 2 coated with an antimicrobial and antioxidant (e.g. Groups 2 and 3) were somewhat more effective regarding this aspect than those films containing only the anti-microbials (e.g. Groups 1 and 4) where spoilage was attribut-able to two mechanisms (i.e. bacterial action and oxidation).

Nine coated polypropylene films (Groups 1-9 below) were prepared using coating compositions having the following weight percent of active ingredients in the coating composition just prior to application to the films:
Weight % of 50/50 blend of methyl and propyl esters of Weight ~
Group parahydroxybenzoic acidAscorbic Acid ` 2 3 15 -- 1 1 -- , ... . . .. . . . . .

,. ~ . - , 10534!~7 `~- Weight % of 50/50 blend of methyl and propyl esters of Weight %
Groupparahydroxybenzoic acid Ascorbic Acid ~; 5 7 18 0 ,:

v 10 (COntrol) O
~; The tenth group represents uncoated polypropylene film. The coating compositions were applied at the rate of l pound of ;-;
~ composition per 1000 square feet of film surface area, and after ~
.. .
appropriate drying to remove solvents, there remained coatings :`
-~ on the n-ine film surfaces containing the initial concentrations of active ingredients contained in a polyvinyl alcohol disper- -f 15 sion.
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Six slices of meat were wrapped with the film for each of the ten groups and maintained at 40F during the test period.
On the seventh day and again on the twelfth day, 2 slices were . ~ .
randomly removed from each group for bacterial observations at :,; .
room temperature (25C). Thus, average spoilage ratings for ` each group were based on 6 slices up to and including the seventh day, 4 slices for the eighth day up to and including ~:~
the eleventh day, and 2 slices for the twelfth day to four-teenth day. The following spoilage scale was used for average : i ~ 25 evaluations:
;``:
Spoilage Rating ~` 100% sp~ilage of total area of slices - 0 ~r 75% spoilage of total area of slices - 1 50~ spoilage of total area of slices - 2 , . .
3025~ spoilage of total area of slices - 3 ~` 5~ spoilage of total area of slices - 4 .. .
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. - ~053497 The results are given in Table 3 below:

Average Spoilage Ratings After ~- Group 7 days11 days 14 days 1 4.16 2.25 1.0 2 3.24 1.25 1.0 ` 3 5.00 4.00 3.0 . ~.
4 5,00 4.80 2.0 - ~ 5 4.84 4.25 2.0 6 5.00 4.75 4.0 :.
7 4.67 4.50 3.5 8 4.50 1.50 1.0 - 9 5.00 4.50 2.0 lO(Control)2.84 1.00 0.5 ` 15 A definition for synergism similar to that for Table 1 is used, namely, S = A-1/2 (B+C), where A is the spoilage rating of the ` wrapped meat where the film wrap coating contains the combina-tion of the 50/50 blend of methyl and propyl esters of parahy-droxybenzoic acid and isoascorbic acid; B is the spoilage rating :
of the wrapped meatwhere the film wrap coating contains only :"
the 50/50 blend of esters in quantities equal to that of "A";

and C represents the spoilage rating of the wrapped meat where ,. . .
~ the film wrap coating contains only the isoascorbic acid in *~ quantities equal to "A`".
~`~ 25 With this definition in mind, the combined average spoilage ratings of the individual active ingredients, i.e. 1/2 (B+C), r~`; is given below for 7, 11 and 14 days where B represents the ; spoilage ratings in Table 3 for Groupll containing only anti-microbials and C represents the spoilage ratings in Table 3 for Group 2 containing only antioxidant.

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~ lOS3497 Rating Period Combined Average Ratings for Groups 1 and 2 ~:j 7 days 4.41 11 days 3.37 14 days 2.25 It is observed that the ratings given in Table 3 for Groups 3 and 6 are greater for each Rating Period compared to the combined ratings given above indicating synergism. The .- ratings for Groups 4 and 5 are greater than the combined ratings for 7 and 11 days, but slightly lower for 14 days, i 10 again indicating synergism.
. EXAMPLE 4 :. Polypropylene films are coated using coating compositions having specific concentrations of active ingredients in the , coating composition just prior to application to the films and .~ 15 resulting in the following spoilage ratings given in Table 4 ~ below: -.~,............... TABLE 4 % I~oascorbic .% p-hydroxybenzoic acid esters Spoilage Rating Acid(50% methyl, 50% propyl? After lO~Days .~ ~
~ 20 5 0 5 : `
.t,`; 3.8 0 5 - 2.5 0 4 1.25 0 3 5

5.0 18 2.5 ,. 25 3.8 18 ; 2.5 18 `~ 1.25 18 2 ~ 2.5 18 O(after 6th day) ...,. ~
.. O 10 3(after 6th day) 0 (Control) 0 5(after 6th day) ,:
:.

~053497 The coating compositions were applied at the rate of 1 pound of composition per 1000 square feet of film surface area, and after appropriate drying to remove solvents, there remained coatings on the 10 film surfaces containing the initial con-centrations of active ingredients contained in a polyvinylalcohol dispersion. The spoilage rating system used is that "O" means excellent (i.e. negligible spoilage) and "5" means very poor ~i.e. substantial spoilage).

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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A packaging film useful in preserving food substances containing oils, fats, and chromoproteins, comprising a flexible substrate material having thereon a surface coating consisting essentially of 0.18-0.22 pounds per 1000 square feet of film surface area of a synergistic preserving mix-ture contained in a polyvinyl alcohol dispersion, said mix-ture consisting of:
(a) at least one antioxidant selected from the group consisting of ascorbic acid and isoascorbic acid;
and (b) an antimicrobial agent consisting of a blend of equal parts by weight of the methyl and propyl esters of parahydroxybenzoic acid, the weight ratio of said antimicrobial agent to said antioxidant falling within the range of about 1:1 to 5:1.

2. The film of Claim 1 wherein said coating contains per 1000 square feet of surface area 0.18 pounds of a mixture contain-ing equal parts by weight of the methyl and propyl esters of parahydroxybenzoic acid and 0.04 pounds of ascorbic acid.

3. The film of Claim 1 wherein said substrate material is polypropylene or polyethylene.