GB1568936A

GB1568936A - Packaging material resistant to insect infestation

Info

Publication number: GB1568936A
Application number: GB487478A
Authority: GB
Original assignee: EXTHENE Pty Ltd
Current assignee: EXTHENE Pty Ltd
Priority date: 1978-02-07
Filing date: 1978-02-07
Publication date: 1980-06-11

Description

(54) PACKAGING MATERIAL RESISTANT TO INSECT INFESTATION (71) We, EXTHENE PTY. LTD., a company incorporated under the laws of the State of Victoria, Australia, of 45 Levanswell Road, Moorabbin, in the State of Victoria, Australia, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the control and prevention of infestation of packaged food products.

Infestations of packaged foods can occur during all stages of storage from the warehouse to the housewife's pantry, in both tropical and temperate climates. Various techniques have been developed to prevent infestation but such techniques cannot deal with all types of infestation and some are generally expensive in their application.

Jute sacks have traditionally been used for the storage and transportation of foodstuffs but because of easy penetration by insects and insect larvae these have generally been replaced by multi-wall paper sacks. With these sacks it was found that insects and larvae could still penetrate the sack through the stitched seams. One proposal to overcome this problem was to tape the stitching with an adhesive tape incorporating an insecticide in the adhesive layer.

In order to prevent insect and larvae infestation in boxed products it has been proposed to coat the box materials with a varnish layer incorporating a general insecticide. However, although this treatment prevented insects boring through the box wall they were still able to penetrate the seams and closures. Barrier films although a partial solution do not prevent insects boring through the plastic film.

The present invention provides a sealed package comprising products subject to insecticidal or pesticidal infestation enclosed with a flexible polymeric film material which has an insecticide or pesticidal agent incorporated therein the said agent having been incorporated in the material from which the film was formed. Insets are repelled from boring through the film due to the presence of the insecticide. The sealed plastic film package of this invention thus provides a simple means for packaging food products. The package can contain a large conventional container or a group of conventional containers with the plastic film and the film heat sealed to provide an effective enclosure.

One insecticidal chemical currently approved for use on food packages by the Food and Drug Administration of the U.S.A. is pyrethrins e.g. pyrethrum or a combination of pyrethrins with the synergist piperonyl butoxide. Pyrethrins have been used in paper coatings for food products packaged in paper or cardboard containers. However it has never been proposed to incorporate pyrethrins or pyrethrins and synergists into a plastic film.

The present invention is not limited to using pyrethrins, and other insecticides can be used particularly where avoidance of contamination of the contents of the packages with the insecticide is not essential. Suitable insecticides include: (i) Bioresmethrin (ii) Dichlorvas (iii) Methylbromide (iv) D.M.P. (Dimethyl Phthalate) (v) Ethylene Dibromide (vi) Ethylene Dichloride (vii) Chloropicrin (Trichoronitromethane) (viii) Sulfuryl Fluoride (ix)Malathion The incorporation of an insecticide into the packaging film ensures that insects cannot penetrate through the film. Thus, if the package is then carefully sealed insects cannot enter through the seal or through the film itself. Prior art attempts to solve the problem of infestation could not provide a complete solution in the manner that the present invention does.

The sealing of the package is preferably by heat sealing but any other means of sealing which prevents ready access to insects is acceptable. For example, where the film is formed into an open ended bag, the open end is folded about itself and stapled together the insects will need to pass between a large area of closely overlapping film and this will be almost as effective a seal as heat sealing.

Numerous conditions have to be met for the development of a commercially successful protective material for packaging materials.

1. The pesticidal agent must be highly effective against all insects considered as insect pests, but must be harmless to humans and domestic animals at the level of concentration used.

2. The application technique should be such that only tolerable levels of the impregnant will appear in the food stuff and the impregnant must have no deleterious effect on the packaging material or any printing.

3. The material of the package should be preferably be sufficient to protect the foodstuff for the duration of its life prior to consumption.

4. Cost per unit must be minimal without, however reducing the efficiency.

Previous proposals of impregnation have been successful in complying with the above requirements but have not been successful in preventing infestation because the packaging system as a whole has not prevented penetration by insects.

In a further aspect of this invention there is provided a method of incorporating insecticides into packaging film and forming a package comprising mixing the active insecticidal composition with the extrudable plastic mix and then extruding the combined mix to form a plastic wrapping film and incorporating the film into a package of the invention.

The films used in the present invention can be either air permeable or air impermeable.

Where the film is air permeable the active insecticide is more likely to migrate from the film into the surrounding atmosphere or the product.

Where low contamination of the pack contents is desirable a laminated film can be used.

Such a laminate can include a comparatively air impermeable film as the inner layer and an air permeable film in the outer layer. The presence of the insecticide in the outer air permeable layer will ensure that external infestation cannot penetrate the pack. Any infestation within the pack will be unable to spread from the pack because the presence of the insecticide in the outer layer of the laminate will prevent the insects within the pack from boring through the film. A preferred laminate for use in this invention is thus a laminate of polyvinylidene chloride (PVDC) and polyethylene in which the polyethylene film incorporates the preferred insecticide namely synergized pyrethrins. Other suitable laminates which may include the active insecticide in either one or both films are regenerated cellulose/low density polyethylene (LDPE) Nylon/LDPE, PVDC control Nylon/LDPE and PVDC/polyethylene-vinyl acetate.

The preferred insecticidal agents are pyrethrins which have low solubility in water and are generally available as oil solutions the solvent generally comprising isoparaffins. Care must be taken to ensure that the pyrethrins are retained within the film and are homogenously distributed within the film. By ensuring this, compliance with the conditions set out above can be ensured.

Difficulty can be encountered in obtaining homogenous retention of the pyrethrins in the film and a technique which is effective is to premix the pyrethins with polymer granules and then to work the mixture in the screw compounder of the extruder followed by extrusion.

Preferably low temperature adiabatic extruders are used to maintain a short, low heat history for the material to prevent degradation of the pyrethrins.

Example In one practical example of this invention the following master batch was prepared.

10 kg low density polyethylene (LDPE) granules 250gm pyrethrum (50%w/w) 500 gms piperonyl butoxide (synergist) stabilizer for film.

This master batch comprises approximately 6.25% by weight of active ingredient. By mixing one part of this master batch with 50 parts of LDPE granules and extruding under low temperature adiabatic conditions a polyethylene packaging film is obtained containing 0.125toof pyrethrum synergized insecticide.

Four pyrethrum containing films according to this invention were prePared, using the above procedure, containing the following content of pyrethrum (PYR) and piperonyl butoxide (PBO).

(i) 0.1%PYR and 0.4%PBO; film treatment 1 (ii) 0.2 PYR and 0.8%PBO; film treatment 1 (iii) 0.1 %PYR and 1.0% PBO; film treatment 3 (iv) 0.2% PYR and 2.0% PBO; film treatment 4 These four films were subiected to a series of tests as outlined below.

FILM REPELLANCY TENT A trial was set up to test repellancy of the various film treatments. Insects were placed on a watch glass covered with treated film, a control film or 50% control and treated film.

However it appears from first results (see Table 1) that the film treatment levels are so high that nearly 100% knock down and even significant kill of the insects was achieved. Obvi ously the effect of the active insecticides in the enclosed space above the films, even for the divided films, was sufficiently high to confuse the insects and prevent a determination of repellancy. Results of mortality and kill counts are recorded in table 1.

TABLE 1. FILM REPELLANCY TEST . . AFTER 28 HOURS FILM SAMPLE % KNOCKDOWN % KILL ST LGB* RW ST LGB RW 1. Film traetment 1. 100 80 20 8 0 2. Film treatment 2. 100 100 8 20 12 3. Film treatment 3. 100 100 0 12 4 4. Film treatment 4. 100 100 96 50 96 5. Control 0 - 0 0 8 0 6. Control/film 1 100 80 8 - 4 7. Control/film 2 100 100 88 68 36 8. Control/film 3 100 92 64 32 16 9. Control/film 4 100 100 16 32 24 S.T. Sawtoothed grain beetle L.G.B. Lesser grain borer R.W. Rice Weevil It was not possible to determine effective knockdown of the lesser grain borer on film samples, as they are very unstable insects on smooth flat surfaces.

A. EXTERNAL SOURCE OFINFESTATION Two packs each of Infest guard film, control film, and control film containing rice treated with 2 ppm pyrethrum in the form of "Pybuthrin" (PYB) (1:10 Pyr:P.B.O.) were made up containing 80g of brown rice. The 6 packs were placed standing end on in jars containing 200 insects of a particular species. The insects were placed below a cardboard platform which supported the six packs.

The packs were inspected for insect penetration after 13 days storage at 30"C and 70% RH. The following results were obtained: TABLE 2(a) JARS CONTAINING INSECT SPECIES IN JAR S.T. LG.B. R.W.

Film treatment 1. Insects very Active Active active. All All packs All packs packs intact. intact. intact.

Film treatment 2. Very active Partial knock- Active All packs down. All All packs intact. packs intact. intact.

Film treatment 3. Active Majority of Same knock All packs borers knock down. All intact. ed down. packs intact.

Pack contain ing Pyb treated rice chewed into.

Film treatment 4. Active though Majority of Many weevils some insects borers appear dead at base knocked down. knocked down, of treated All packs All packs packs. All intact, intact. packs intact.

Inspection after 37 days storage TABLE 2Kb) JARS CONTAINING INSECT SPECIES IN JAR.

S.T. l-G.B. RW.

Film treatment 1 Partial Complete Complete knockdown/ knockdown/ knockdown/ kill. All kill of kill. All packs intact. insects at packs base of jar. intact.

One control pack pene trated.

Film treatment 2 Complete Majority Complete knockdown/kill. knockdown/ knockdown/ All packs kill. All kill. Packs intact. packs intact. intact.

Film treatment 3 Partial Majority Majority knockdown/ knockdown/ knockdown kill. kill. Pack and appar Remaining containing ently dead. insects PYB treat- All packs active. ment pene- intact. trated, with healthy insects inside.

Film treatment 4 Generally Total Total knock total knockdown/ down/kill. knockdown/ kill. All All packs kill except packs intact. for 1 pack intact. containing PYB rice with faulty seal. Saw tooths inside pack active.

Following 50 days storage, insect counts were carried out for all storage jars. Packs infested during the storage period were also opened for insect counts. Following counting, all sound packs were returned to the jars and a further 200 adult insects and a teaspoon of brown rice feed added to the jars.

TABLE 2(c) JARS CONTAINING INSECT SPECIES IN JAR LG.B. KW. S.T.

Film treatment 1 165 dead, 5 180 dead 0 212 dead 17 alive. alive alive Control pack All packs All packs infested sound sound with 100 alive, 6 dead and breeding.

Remaining packs sound.

Film treatment 2 186 dead, 0 230 dead, 0 210 dead, 7 alive alive alive All packs All packs All packs sound sound sound Film treatment 3 163 dead, 1 215 dead, 0 224 dead, 7 alive alive alive Pybuthrin All packs All packs pack infested sound sound with 18 alive 15 dead and breeding.

Remaining packs sound.

Film treatment 4 200 dead, 1 200 dead, 0 167 dead, 28 alive alive alive All packs All packs Pybuthrin sound sound pack with faulty seal infested with 38 alive, 8 dead and breeding.

Remaining packs sound.

B. INTERNAL SOURCE OFINFESTATION One pack of each film treatment and the control film was made up containing 400 g of brown rice seeded with 50 of each insect species. A second control film pack was made up with 400 g of pyrethrin treated brown rice and 50 of each insect species. The treated rice is directly sprayed with a pyrethrin solution which results in a content of 2ppm pyrethrin in the rice. The packs, placed in ventilated screw top jars, were inspected after 12 days storage at 30"C and 70%RH. The following points were noted: TABLE 3(a) PACK INSECT/PACK CONDITION Control film Insects active. Control film chewed through Control film . Majority of insects knocked down. containing treated rice. Some active.

(2ppm pyr.) Film treatment 1. No visible effect on insects. Film intact.

Film treatment 2. Majority of insects knocked down.

Some active.

Film intact.

Film treatment 3. As for film treatment 2.

Film treatment 4. Total insect knockdown - many of the insects appear dead.

Inspection after 36 days storage TABLE 3Kb) PACK INSECT/PACK CONDITION Control film Insects very active. Considerable damage to rice. Pack chewed through.

Control film Pack chewed through. Live sawtooths containing 2 ppm and weevils and two dead borers outside Pyr. Treated rice. the pack.

Film treatment 1 Complete knockdown/kill of all visible insects.

Pack sound.

Film treatment 2 Complete knockdown/kill of borers.

Some sawtooths and weevils active.

Pack sound.

Film treatment 3 As for 2.

Film treatment 4 Only one sawtooth visibly alive, otherwise complete knockdown/kill. Pack sound.

Following 49 days storage, all packs were opened and insects counted. The following results were obtained.

TABLE 3(c) PACK No. of insect Insect L.G.B. R.W. S.T. holes in pack Location Alive Dead Alive Dead Alive Dead Control 154 outside 3 2 18 1 156 30 inside 1268 4 212 16 960 36 Total 1271 6 230 17 1116 66 Pyb. treated 16 outside 0 1 20 0 30 9 rice inside 20 32 227 43 358 34 Total 20 33 247 43 388 43 Film Treatment 1 Nil inside 62 51 0 52 0 54 Film Treatment 2 Nil inside 204 48 2 60 0 53 Film Treatment 3 Nil inside 322 40 2 57 1 44 Film Treatment 4 Nil inside 297 48 0 45 0 55 Note: 1. Refers to the number of insects either inside or outside of the rice pack.

2. Both Film treatments 1 and 4 exhibited a tight "vacuum pack" effect throughout the storage trial.

Following counting of insects in Film Treatment packs 1-4, rice and live insects were returned to the packs and the packs resealed.

SIMULATION OF RENTAL STORAGE CONDITIONS SUBJECT TO HEAVY INFESTATION PRESSURE 500 gram packs of milled and brown rice were made up in sound (sealed) and unsound (unsealed) packs. The packs are stored randomly on shelves in infested with lesser Gram borers and to a lesser extent with Rice weevils and Saw tooth beetles.

The results of a count of dead insects around each group of brown rice packs is tabulated below. The count was carried out after 15 days.

TABLE4 FILM PACK CONDITION INSECT MORTALITY LG.B. R.W. S.T.

Control Sound 0 0 0 Unsound 2 0 0 Control-Pyb Sound 2 0 0 Unsound 2 1 0 Film Treatment 1 Sound 34 1 0 Unsound 45 1 0 " " 2 Sound 48 0 0 Unsound 47 1 2 3 3 Sound 40 0 0 Unsound 33 0 0 " 4 Sound 130 0 3 Unsound 65 0 3 Control = Pyb is control film containing pyrethrin sprayed rice containing 2ppm pyrethrins with synergist.

After 31 days the packs for each group of sound and unsound packs of milled and brown rice were checked for infestation. The results are shown in Tables 5 to 8.

TABLE 5 - Thirtyone days Pack Condition: Unsound Rice: Milled PACK No. Insects Present LG.B. RW. S.T. TOTAL Alive Dead Alive Dead Alive Dead Alive Dead Control 224 664 42 8 42 714 42 212 636 40 4 40 680 40 211 592 48 8 88 6XX 48 Total 1892 130 20 0 170 0 2082 130 Ave. 630 43 7 0 57 0 694 43 PYB. 543 816 52 0 28 844 52 Treated Rice 244 122 13 0 12 134 13 232 156 34 0 28 184 34 Total 1094 99 0 0 68 0 1162 99 Ave. 364 33 0 0 33 0 387 33 Film 22 0 0 1 1 Treatment 25 0 0 4 4 1 21 0 0 0 0 Total O 0 0 0 5 0 5 0 Ave. O 0 0 0 2 0 2 0 Film 92 0 0 6 6 Treatment 88 0 0 0 0 100 0 0 0 1 0 Total O 0 0 0 6 1 6 Ave. O 0 0 0 2 0 2 0 Film 124 0 0 5 5 Treatment 125 40 2 7 3 35 82 5 123 0 | 5 6 Total 40 2 8 3 45 0 93 5 Ave. 13 1 3 1 15 0 31 2 TABLE 6 - Thirtyone days Pack Condition: Unsound Rice: Brown PACK No. Insects Present L.G.B. R.W. S.T. 101A| Alive Dead Alive Dead Alive Dead Alive Dead Control 377 504 24 12 0 60 0 576 24 337 89 9 2 0 22 0 113 9 357 151 11 3 13 167 II Total 744 44 17 0 95 0 856 44 Ave. 248 15 6 0 31 0 285 15 PYB. 309 167 31 1 0 17 1 185 Treated 311 54 1 1 10 74 rice 325 222 18 0 14 236 18 Total 443 50 2 0 50 1 495 51 Ave. 148 17 1 0 16 0 165 17 Film 421 1 1 5 1 Treatment 414 01 7 7 1 425 0 1 2 1 2 2 Total I 0 2 3 13 1 16 4 Ave. 0 0 1 i 4 0 5 1 Film 445 0 0 0 0 3 1 3 Treatment 427 1 @ @ @ 5 @ 450 0 1 7 2 Total I 0 2 1 12 5 15 5 Ave. 0 0 I 04 2 5 2 Film 524 0 0 0 1 6 0 6 I Treatment 513 0 0 9 9 0 525 0 | 3 3 4 3 Total 0 0 1 1 18 3 19 4 Ave. 0 0 0 0 6 1 6 Film 530 0 0 0 0 0 0 0 0 Treat meat 4 Total 0 0 0 0 0 0 0 0 Ave. 0 0 0 0 0 0 0 0 TABLE 7 - Thirtyone days Pack Condition: Sound Rice: Milled PACK Item Insects Present No. LC.B. R.W. ST. TOTAL Alive Dead Alive Dead Alive Dead Alive Dead Control 180 360 8 0 12 372 R 181 414 28 0 22 436 28 182 554 8 56 46 656 8 Total 1328 44 56 0 80 0 1464 44 Ave. 443 15 18 0 27 0 48X 15 PYB. 261 27 1 0 0 3 0 30 1 Treated 358 106 6 0 6 202 6 Race 275 8 1 0 0 8 1 Total 231 8 0 0 9 0 240 8 Ave. 77 3 0 0 3 0 80 3 Film Treatment Total Ave. O 0 0 0 0 0 0 0 Film Treatment Total Ave. O 0 0 0 0 0 0 0 Film 477* 44 2 0 9 53 Treatment 0 0 0 0 Total 44 2 0 0 9 0 53 2 Ave. 15 1 0 0 3 0 18 I * 4 Holes chewed through pack TABLE 8 - Thirtyone days Pack Condition: Sound Rice: Brown PACK No. Insects Present L.G.B. R.W. S.T. TOTAL Alive Dead Alive Dead Alive Dead Alive Dead Control 357 130 10 0 10 0 140 1(1 354 274 32 6 2 54 334 34 372 45 1 0 3 48 Total 449 43 6 2 67 0 522 45 Ave. 150 14 2 1 22 0 174 15 PYB. 290 216 22 6 32 254 22 Treated 292 166 6 0 30 196 6 Rice 298 19 1 0 5 24 1 Total 401 29 6 0 67 0 474 29 Ave. 134 10 2 0 22 0 158 10 Film Treatment Total O 0 0 0 0 0 0 0 Ave. O 0 0 0 0 0 0 0 Filni Treatment Total O 0 0 0 0 0 0 0 Ave. O 0 0 0 0 0 0 0 Film 494* 0 3 59 5 62 5 Treatment 3 Total O 0 0 3 0 59 5 62 5 Ave. O 0 1 0 20 2 21 2 Film Treatment 4 Total O 0 0 0 0 0 0 0 Ave. O 0 0 0 0 0 0 0 * Pack Punctured The results of Tables 1 to 8 shows that the impregnated films are a superior form of pest control to direct insecticide spraying of the product to be packaged which to date has been the most successful conventional method of controlling infestation.

Further tests have been carried out using low concentrations of insecticide in the film.

As for the other tests the impregnated films were compared with a control and packs containing brown rice directly sprayed with insecticide.

The films were polyethylene made into bags containing 500 g of rice and containing 1) 0.015% pyrethrin 2) 0.030% 3) 0.060% 4) 0.1 % film treatment 1 is equivalent to a direct rice treatment of lppm film treatment 2 is equivalent to a direct rice treatment of 2ppm film treatment 3 is equivalent to a direct rice treatment of 4ppm film treatment 4 is equivalent to a direct rice treatment of 6.66ppm.

Tables 9 and 10 set out the results.

LOWER FILM TREATMENT LEVELS AFTER 60 DAYS Pack Condition: Unsound TABLE 9 9 Rice: Brown PACK No. Insects Present L.G.B. R.W. S.T. TOTAL Alive Dead Alive Dead Alive Dead Alive Dead Control 77 12 12 28 2 72 28 112 42 86 0 0 1 0 10 0 II 0 83 0 0 1 0 12 1 1 Total 12 12 30 2 94 29 136 43 - Ave. 4 4 10 1 31 10 45 14 PYB. 6 0 0 1 0 103 8 104 8 (2ppm. Rice 14 0 0 0 0 58 2 58 2 Treatment 4 24 12 60 12 36 16 120 40 Total 24 12 61 12 197 26 28' 50 Ave. 8 4 20 4 66 9 94 17 0#015% 104 2 2 1 1 46 0 49 3 PYR = 1ppm) 116 0 0 0 0 5 0 5 0 114 0 0 4 0 , 59 0 63 0 Total 2 2 5 1 110 0 117 3 Ave 1 1 2 0 37 0 39 (0#03% 190 0 0 0 0 0 0 0 0 PYR = 2ppm) 196 0 0 0 0 2 0 2 0 200 103 2 103 2 Total 0 0 0 0 105 2 105 2 Ave. 0 0 0 0 35 1 35 (0#065% 206 0 0 1 0 47 0 4R 0 PYR= 4ppm) 221 0 0 0 0 0 0 0 0 217 0 0 0 0 1 0 1 0 Total 0 0 .1 0 48 0 49 0 Ave. 0 0 0 0 16 0 16 0 (0#10% 278 0 0 0 0 23 0 23 0 PYR) 297 0 0 0 0 67 1 67 1 281 37 37 0 Total 0 0 0 0 127 1 127 Ave. 0 0 0 0 42 0 42 0 TABLE 10. LOWER FOLM LEVELS AFTER 60 DAY Pack Condition: Sound Rice: Brown PACK No. Insects Presents L.G.B. R.W. S.T. TOTAL Alive Dtld Alive Dead Alive Dead Alive Dead Control 64 10 16 12 4 324 24 346 44 53 11 16 4 152 4 167 20 69 0 0 5 0 209 2 214 2 Total 21 32 21 4 685 30 727 66 Ave. 7 11 7 1 228 10 242 22 PYB 31 6 4 4 0 41 6 (2ppm Rice Treatment) Total 6 4 4 0 41 6 51 10 Ave. 2 1 1 0 14 2 17 3 (0.1015% 41 2 0 61 1 63 1 PYR = 1ppm) Total 0 0 2 0 61 1 63 1 Ave. - - 1 - 20 - 21 (0#03% PYR = 1ppm) Total Ave. 0 (0#055% 249 0 0 0 0 185 2 185 2 PYR = 2ppm 250 4 4 1 0 47 1 52 5 227 7 0 5 0 31 0 38 0 Total 6 4 6 0 263 3 275 7 Ave. 2 1 2 0 88 1 92 2 (0.10% PYR 262 0 0 0 0 8 0 Total O 0 0 0 8 0 8 Ave. 3 3 These figures again show the superiority of sealed packs of impregnated film in preventing infestation.

The packaging film of this invention when used as an outer heat sealed wrapping or bag for food packages not only prevents insects from boring into or entering the plastic film envelope but also prevents any insect infestation from spreading should larvae or eggs be present in the food product prior to wrapping. The cost of providing such a film is only higher than that of existing film by the cost of incorporating the pyrethrins and thus is less costly and more effective than conventional methods which require an additional manufacturing step and are not totally effective.

Claims

WHAT WE CLAIM IS:

1. A sealed package comprising products subject to insecticidal or pesticidal infestation enclosed with a flexible polymeric film material which has an insecticide or pesticidal agent incorporated therein, the said agent having been incorporated in the materials from which the film was formed.

2. A sealed package as claimed in claim 1 wherein there is incorporated in the film as a pesticidal agent a pyrethrin compound or synergized pyrethrin compound.

3. A sealed package as claimed in claim 1 and substantially as hereinbefore described.

4. A sealed package as claimed in claim 1 wherein the film is as described above as any one of "film treatments" 1 to 4 in the Example.

5. A method of preparing products subject to insecticidal or pesticidal infestation for storage which comprises enclosing said products within a sealed flexible polymeric film to form a package as claimed in any preceding claim.