Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1097~L3~1L
This invention relates to the control and prevention
o~ infestation of packaged food products.
Infestation 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 technique
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by insects and insect larvae these have generally been replaced
by multi-wall paper sacks~ With these sacks it was found that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
stiched 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.
`- It is an object o~ this invention to provide a means
which can be generally applied to prevent insect infestation
in packaged food products. To this end there is provided a
plastic wrapping film incorporating an insecticidal agent as
a component of the film. Such a film can be used to fully
envelop conventional food packages and by sealing the
- 2 -
~1 :
: . :,:: :: :: : :: :: . . : :
. ; :: . :. -, : : -.
. ` 1097~31
seams an airtight package is ~ormed which provides no access
for insects to penetrate the plastic envelope. Insects are
repelled from boring through the film due to the presence of
the insecticide. The sealable plastic film of this invention
thus provides a simple means, for packaging food products.
Large conventional containers or a ~roup of conventional
containers can be wrapped within this plastic film and the
film heat sealed to provid an effective preventive covering.
: One insecticidal chemical currently approved for
use on food packages by the Food and Drug Administration of
the U.S.A. is pyrethrins or a combination of pyrethrums with
the s~lergist piperonyl butoxide. Pyrethrins have been used
in paper coatings for food products packaged in paper or card-
board containers. However it has never been proposed to
incorporate pyrethrins or pyrethrums and synergists into a
plastic film.
~he present invention is not limited to using pyreth~
rins, and other insecticides can be used particularly where
avoidance of contamination of the contents o~ the packages
with the insecticide is not essential. Suitable insecticides
include:
(i) Bioresmethrin
(ii) Dichlorvas
- (iii) Methylbromide
(iv) D.M.P.
(v) Ethelyne Dibromide
(vi) Ethelyne Dichloride
(vii) Chlorophictrin
(viii) Sulfuryl Fluoride
- 30 (ix) Malathion
..
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~L09713~
The incorporation of an insecticide into the pack-
aging 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 .
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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 effec~tive a seal as heat sealing.
Numerous conditions have to be met for the develop-
ment of an impregnation suitable for packaging materials.
1. The impregnant 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 impregnation 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 packing
material or any printing.
3. The impregnation should be preferably be sufficient
to protect the foodstuf~ for the duration of its life prior
to consumption.
4. Cost per unit must be minimal without, however,
reducing the efficiency.
Previous proposals of :impregnantion have been
successful in complying with the above requirements but have
not been successul 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 packag-
ing film comprising mixing the active insecticidal composit-
ion with the extrudable plastic mix and then extruding the
combined mix to form a plastic wrapping film of this invention.
The films of the present invention can be either air
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~0~7~l31
permeable or air impermeable. Where the film is air
B dCf~
permeable the ~ct-we-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. ~ny infestation within the pack will be unable to
spread from the pack because the presence oE the insecticide
in the outer layer of the laminate will prevent the insects
within the pack from boring through the filrn. A preferred
laminate ,according to this invention is thus a laminate of
~2 p/~ yl~c~en e
inyldlcn~ chloride and polyethylene in which the poly-
ethylene film incorporates the preferred insecticide impreg-
nant namely synergized pyrethrins. Other suitable laminates
which may include the active insecticide in either one'or both
films are cellophane/LDPE, Nylon/LDPE, PVDC control Nylon/
LDPE and PVDC/EVA.
The preferred insecticidal agents are pyrethrins
which have low solubility in water and are generally available
as oil solutions the solvent generally cornprising 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, comp]iance with the conditions se-t
out above can be ensured.
Difficulty can be encountered in obtaining homogen-
ous retention of the pyrethrins in the film and the technique
which is e~fective is to premix the pyrethrins with polymer
. ~ ,- ... ...
,
. 1~9~L3~L
granules and then to work the mixture in the screw compounder
of the extruder followed by extrusion. Preferably low
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temperature a~iabatic extruders are used to maintain a short,
low heat history for the material to prevent degradation of
the pyrethrins.
In one practical example of this invention the
following master batch was prepared.
10 kg low density polyethylene (LDPE) granules
250 gm pyrethrum (50% w/w)
500 gms piperonyl butoxide (synergist)
stabilizer for film.
This master batch comprises approximately 6.25% by
weight of active ingredient. ~y 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 0.125% of pyrethrum
synergized insecticide.
Four pyrethrum containing films according to this
inventio~ were prepared, using the above procedure, containing
the following content of pyrethrins (PYR) and piperonyl
butoxide (PB0).
20(i) 0.1% PYR and 0.4% PB0 ; film treatment 1
(ii) 0.2% PYR and 0.8% PB0 ; " " 2
(iii) 0.1% PYR and 1.0% PB0 ; " " 3
(iv) O.2% PYR and 2.0% PB0 ; " " 4
These four films were subjected to a series of tests
as outlined below.
FILM REPELLANCY TEST.
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
- 30 film. However it appears from first results (see Table 1)
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10~7~31
that the film treatment levels are so high that nearly 100%
knock down and even significant kill of the insects was achieved.
Obviously the effect of the actives 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* RWST LBG RW
1. Film treatment 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 knowndown
oE the lesser grain borer on file samples, as they
are very unstable insects on smooth flat surfaces.
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~ 973L3~
.
A. EXTERNAL SOURCE OF INFESTATION.
Two packs each of Infest guard film control film
and control film containing rice treated with 2 ppm pyrethrins
(1:10 Pyr:P.B.O.) were rnade 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 30C and 70% RH. The following
results were obtained:
TABLE 2(a)
_ . _ _ _
JARS CONTAINING INSECT SPECIES IN JAR
_ _ _S.T. _ L.G.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
2Q intact. packs lntact. 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.
. _ _ . _ . _ . .. . _ . . _ .. _
F~lm 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.
.... _ . . . _ . _ _ .
. ~
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.
7~31
Inspection after 37 days storage
TABLE 2(b).
JARS CONTAINING INSECT SPECIES IN JAR -
S.T. L.G.B. R.W.
Film treatment 1 Partial Complete Complete
knockdown/ knockdown/ knockdown/
kill. All kill of kill. All
packs intact. insects at packs intact.
base of jar.
One control
pack penetrated.
Film treatment ~ Complete Majority Complete
~nockdown/ knockdown/ knockdown/
kill. All kill. All kill. Packs
packs intact. packs intact. intact.
Film treatment 3 Partial Majority Majority
knockdown/ knockdown/kill. knockdown and
kill. Remain- Pack containing apparently
ing insects PYB treatment dead. All
active. penetrated,with packs intact.
healthy insects
inside.
Film treatment 4 Generally Total Total knock-
total knock- knockdown/kill. down/kill.
down/kill All Packs All packs
except for 1 intact. intact.
pack contain-
ing PYB rice
with faulty
seal. Saw-
tooths inside
pack active.
Following 50_~ys 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.
_~ ... .
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~)97~3 a
TABLE 2(c).
JARS CONTAINING INSECT SPECIES IN JAR
L.G.B. R.W. S.T.
Film treatment 1 165 dead, 5 180 dead 0 212 dead 17
alive. Control alive. All alive~ All
pack infested packs sound. packs sound.
with 100 alive,
6 dead and
breeding.
Remaining
packs sound.
Film treatment 2 186 dead, 0 230 dead, 0 210 dead, 7
alive. All Alive. All alive. All
packs sound. packs sound. packs sound.
Film treatment 3 163 dead, 1 215 dead, 0 224 dead, 7
alive. Pybuthrin alive. All alive. All
pack infested packs sound. packs sound.
with 18 alive,
15 dead and
breeding.
Remaining
packs sound.
Film treatment 4 200 dead, 1 200 dead, 0 167 dead, 28
alive. All alive. A11 alive. Pybu-
packs sound. packs sound. thrin pack
with faulty
seal invested
with 38 alive,
8 dead and
breeding.
Remaining
packs sound.
B. INTERNAL SOURCE OF INFESTATION.
One pack of each film treatment and the control film
was made up containing 400 g of brown rice seeded wi-th 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 rise 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 ~ars,
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1~97~3~
were inspected after 12 days storage at 30C and 70~ RH. The
following points were noted:
TABL _3(a).
. . _ . . . _ . . _ _ .
PACK INSECT/PACK CONDITION
. ._ ... _ _ , _ ~
Control film Insects active. Control film chewed
through.
. . _ . . _ _ .
; Control film con- Majority of insects knocked down. Some
taining treated Active.
rice. (2ppm pyr.) Majority of insects knocked down. Some
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 3(b).
PACK INSECT/PACK CONDITION
. _
Control film Insects very active. Considerable damage
to rice. Pack chewed through.
. _
Control fiIm con- Pack chewed through. Live sawtooths and
taining 2 ppm Pyr. weevils and two dead borers outside the
treated rice. pack.
_ _
Film treatment 1 Complete knockdown/kill of all visible
insects. Pack sound.
~ .
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~9713i
... . _ . . :
ilm treatment 2 Complete knockdown/kill of borers. Some
sawthooths and weevils active. Pack sound.
ilm treatment 3 As for 2.
ilm treatment 4 Only one sawtooth visibly alive, otherwise
complete knockdown/kill. Pack sound.
_ _ _ . _ _ ................... . _ _
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~097:~L3~
SIMULATION OF RETAIL STORAGE CONDITIONS
SUBJECT TO HEAVY INFESTATION PRESSURE.
500 gram packs of milled and brown rice were made
up in so~md (sealed) and unsound (unsealed) packs. The
packs are stored randomly o~ shelves in infested with Lesser
Gram borers and to a lesser extent with Rice weevils and Saw
tooth bee-tles.
The results of a count of dead insects around each
group of brown-rice packets is tabulated below. The co~mt
was carried out after 15 days.
TABLE 4
FILM PACK CONDITION INSECT MORTALITY
L.G.B. R.W. S.T.
. _ _ . . ~ _ . . _ _ _ . _
Control Sound O O O
" 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 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 ~roup of sound and
unsound packs of milled and brown rice were checked for
infestation. The results are shown in Tables 5 to 8.
.. . . . . ~ . .. ... ~ .. ..... .... .. . . . . .. . . . , .. ~ . .. . . . . ..
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~97131
TABLE 5 - Thirtyone days
Pack Condition: Unsound
Rice: Milled
_ _ ,
PACK No. Insects Present
L.G.B. RoW. S.T. TOTAL
Alive Dead Alive Dead Alive Dead Alive Dead
Control 224664 42 8 42 714 42
212636 40 4 40 680 40
211592 49 8 88 688 _ _
Total189213020 0170 0 2082 130
Ave.630 43 7 0 57 0 694 43
_ .
PYB. 543816 52 0 28 844 52
Treated
Rice 244122 13 0 12 134 13
232156 34 0 _ 28 _ 18q 34
Total109499 0 0 68 0 1162 99
Ave~364 33 0 0 33 0 387 33
. _
Film 22 0 0 1 1
Treatment
` 1 25 0 0 4 4
21 0 0 _ 0 _ ~
Total0 0 0 0 5 0 5 0
Ave. 0 0 0 0 2 0 2 0
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~0~7~L31
TABLE 5 - Thirtyone days, cont'd
Film 92 0 _ 0 6 6
Treatment
2 88 0 0 0 0
100 O _O O 1 O
Total 0 0 0 0 6 1 6
Ave. 0 0 0 0 2 0 2 0
. _ _. _
Film 124 0 0 5 5
Treatment
3 ~ __ _ ~ 7 ~ 3 ~ 35
Total 40 2 8 3 45 0 93
. Age. 13 1 3 1 lS 0 31 2
TABLE 6 - Thirtyone days
Pack Condition: Unsound
Ri:ce: Brown
PACK No. Insects Present
: L.G.B. R.W. S.T. TOTAL
Alive Dead Alive Dead Alive Dead Alive Dead
Control 377 504 24 12 0 60 0 576 24
337 89 9 2 1 0 22 0 113 9
:~ 357 151 11 3 ! 13 167 11
l ~ ~
Total744 44 17 0 95 0 856 44
: Ave. 248 15 6 0 31 0 285 15
16
" ` ' : ' . '' ' . : .
7~L31
TABLE 6 - Thirtyone days, cont'd
PYB. 309 167 31 1 O17 1185 32
Treated .
rice 311 54 1 1 19 74
325 222 18 O _ 14 236 18
; Total443 50 2 O50 1495 51
. Ave.148 17 1 O16 O165 17
_ _ _
: Film 421 1 1 5 1 7
Treatment
1 414 O 17 7
425 O 1 21 2 2
_
Total 1 O 2 313 116 4 . .
Ave. O O 1 . 1 4 O 5
. _
Film 445 O O OO 3 1 3
Treatment
2 427 1 2 2 2 5 2
450 O 17 2 7 3
_ _ .
Total 1 O 2 112 515 6
Ave. O O 1 O 4 2 5 2
__
Film 524 O O O 1 6 O 6
Treatment
: 3 513 O O .9 9 O
525 O 1 3 3 4 3
~__ _ _ _
Total O O 1 1 18 319 4
Ave. O O O O 6 1 6
Film 530 O O O O O OO O
Treatment _ ~
Total O O O O O O . O O
__ Ave O O O O O O O
17
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97~3~
TABLE 7 - Thirtyone days
Pack Condition: Sound
Rice: Milled
PACK Item Insects Present
No. L.G.B. R.W. S.T.TOTAL
Alive Dead Alive Dead Alive Dead Alive Dead
_
Control 180 360 8 0 12 372 8
181 414 28 0 22 436 2g
182 554 8 56 46 656 8
Total 1328 44 56 0 80 01464 44
Ave. 443 15 18 0 27 0488 15
. _
PYB. 261 27 1 0 0 3 0 30
Treated
Rice 258 196 6 0 6 202 6
275 8 1 0 0 8
Total 231 8 0 0 9 0240 8
Ave. 77 3 0 0 3 0 80 3
Pilm _ ~ ~ _
Treatment
.
Total !
Ave. 0 0 0 0 0 0 0 0
Film _
Treatment
-~ Avtal 0 0 0 0 0 ~ 0 ~ 0
. ~ ~ ,~
~ 18 ~
. .
-
:~97~3~
TABLE 7 - Thirtyone days, cont'd
. _ ..
Film 477* 44 2 0 9 53 2
3rea~enl ~ ~ 1~L~
Total 44 2 0 0 9 0 53 2
Ave. 15 1 0 0 3 0 18
_
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 10
354 274 32 6 2 54 334 34
372 45 1 0 3 48
Total 449 43 6 2 67 0 552 45
Ave. 150 14 2 1 22 0 174 15
:
Treated 290 216 22 6 32 254 22
Rice 292 166 6 0 30 196 6
298 19 1 ~ 5 24
Total 40] 29 6 ¦0 67 0 474 29
Ave. 134 10 2 j 0 22 0 158 10
_
* 4 Holes chewed through pack
19
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71:~3~
TABLE 8 - Thirtyone days, cont'd
Treatmen~ ~ ~ ~ I ~ r
Total 0 0 0 0 0 0 0 0
Film ~ve 0 0 0 0 0 0 0 0
Treatment
Total 0 0 0 0 0 0 0 0
Ave. 0 0 0 0 0 0 0 0
Film 494* 0 3 59 5 62 5
Treatment
__
Total 0 0 3 0 59 5 62 5
Ave. 0 0 l 0 20 2 21 2
Film _ _
Treatment _ _
Total 0 0 0 0 0 0 0 0
Ave. 0 0 ~ 0 0 0 n 0
The results of the Tables 1 to 8 shows that the
impregnated fllms 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
investation.
* Pack Punctured
- 20-
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3t7~3~
Further tests have been carried out using low concen-
trations 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 6.6ppm.
Tables 9 and 10 set out the results.
TABLE 9 - LOWER FILM TREATMENT LEVELS AFTER 60 DAYS
Pack Condition: Unsound
R _e: 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
'. g6 O O 1 O 10 O 11 O
83 0 0 1 0 12 1 1
Total 12 12 30 2 9429 136 43
Ave. 4 4 10 1 3110 45 14
~ 21 ~
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. . : . .. :-
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97~L31
TABLE 9 - Lower Film Treatment Levels After 60 Days, cont'd
PYB. 6 0 0 I 0103 8 104 8
(2ppm.Rice
Treatment 14 0 0 0 0 58 2 58 2
4 24 12 60 12 36 16 120 40
_ _
Total 24 12 61 12197 26 282 50
Ave. 8 4 20 4 66 _ 94 17
(01015% 104 2 2 1 1 46 0 49 3
PYR_lppm)
116 0 0 0 0 5 0 5 0
114 0 0 4 0 59 0 63 0
Total 2 2 5 1110 0 117 3
Ave. 1 1 2 0 37 O 39
_
(o2,o3% 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 0105 2 lG5 2
Ave. 0 0 0 0 35 1 1 L
(o3065% 206 0 0 1 0 q7 O 48 O
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
.
- 2~ -
.- ... . ..
~097~3~
TABLE 9 - Lower Film Treatment Levels A~ter 60 Days, cont'd
278 0 0 0 0 23 0 23 0
2g7 0 0 0 067 1 67
281 37 _ 37 0
Total 0 0 0 0127 1 127
Ave. 0 0 O 042 0 42 0
TABLE 10 - LOWER FILM LEVELS AFTER 60 DAYS
Pack Condition: Sound
Rice: Brown
PACK No. Insects Present
L.G.B. R.W. S.T. TOTAL
Alive Dead Alive Dead Alive¦Dead AlivelDead
.. I ......
Control 64 10 16 12 4324 24 346¦ 44
53 11 16 4 152 4 167 20
` 69 0 0 5 0209 2 214 2
Total 21 32 21 4685 30 7271 66
Ave. 7 11 7 1228 10 242¦ 22
PYB 31 6 4 4 041 6
(2pFm Rice
Treatment) _
Total ~6 4 4 041 6 51 10
Ave. 12 1 1 014 2 17 3
~ _ I _ _
(0.015% 41 ; 2 0 61 1 63
` PYR_lppm)
,
Total 0 0 2 061 1 63
Ave. _ _ 1 _20 _ 21
.
_ 23 -
-, .. ::
, . ~ ~ :. ,:. : i :.. ..
'~`, ,:, ,' : ' ~ :
3~
TABLE 10 - Lower Film Levels After 60 Days, cont'd
PYR 2ppm) ; ~ _
_ .. ... _
(0.3055% 249 0 0 0 0 185 2 185 2
PYR-4ppm)
250 4 4 1 047 1 52 5
227 7 0 5 031 0 38 0
.
Total 6 4 6 0263 3 275 7
PYR) ¦Ave. l 2 ~ 1
2620 0 0 08 0 8
Total0 0 0 08 0 8 0
_ 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 incorporatin~ the pyrethrins
and thus is less costly and more effective than conventional
methods which require an additional manufacturing step and are
not totally effective.
- 24 -
: -. .
: . ...... . .
- : . , : . . :
