FOOD PACKAGING RESISTANT TO PERFORATION BY INSECTS

Abstract: The food-product packaging resistant to perforation by insects according to the invention comprises a container made of sheet packaging material compatible with the product to be packed or wrapped and with use thereof, the surface of the material facing the exterior of the packed container presenting a uniform distribution of rough portions having small dimensions and totally covering the surface and made of synthetic material not eatable by insects, preferably forming a down. It has been found that the down effectively withstands efforts of insects to penetrate containers constructed of material according to the invention.

Description: The invention relates to material for packaging food products and resistant to perforation by insects. Protection of packaged goods is a particularly important aspect of the problem of preservation thereof. Packaging is important not only for food products sold at the end of the processing cycle but also for products which are stored between processing steps, often for very long periods, in containers such as bags or cardboard boxes or the like. In order to prevent the packaged goods from being damaged by infesting insects, it would be desirable to reduce the storage periods to a minimum, but even when this is possible, sometimes a few days or even a few hours are sufficient for some insects which feed on the goods to eat their way through apparently insuperable barriers. In many cases, furthermore, goods are stored for weeks or months in depots exposed to attack by numerous species of insects. Since these products are to be used as food, the problem is to protect them without subsequent chemical disinfestation, which would replace one form of food contamination by another. Storage places can be disinfected by fumigation, but in most cases these places cannot remain sealed. This is the case e.g. in supermarkets where boxes, packets and bags are practically uncovered, on display to the public. Under these conditions, only sealed packaging of glass or metal of sufficient thickness would be capable of protecting the goods from insects, but these materials are bulky, expensive and often inconvenient to use. The food industries generally use packaging consisting of films of synthetic material such as polyethylene, polyvinyl chloride (PVC) and the like, and also in various combinations, but the resistance to insects of all these materials is partial and temporary and it is not always acceptable for them to be in contact with substances for use as food. Non-biodegradable synthetic substances are also undesirable as packaging material, particularly for food and products in wide use, owing to the effect on the environment when they are thrown away. Paper is suitable for this purpose since it does not leave toxic molecules in food, but is extremely weak as a barrier against insects. The problem of perforation of food packaging by insects is particularly important in temperate or subtropical countries, where insects have their greatest reproductive power, with serious consequences on the preservation of food. The object of the invention therefore is to provide a material for wrapping and packaging food products which is compatible with the use of the packed substances as food and is resistant to penetration by insects and is inexpensive and easy to use. These results are obtained by the invention, which provides food-product packaging resistant to perforation by insects, comprising a container made of sheet packaging material compatible with the product to be packed or wrapped and with use thereof, the surface of the material facing the exterior of the packed container presenting a uniform distribution of rough portions having minute dimensions and covering the total surface and made of synthetic material not eatable by insects. More particularly, the rough portions have dimensions substantially less than 50 µm. In a preferred embodiment of the invention, the uniform distribution of rough portions having minute dimensions is in the form of a down of synthetic material firmly adhering to the surface. Preferably, the down is made up of spun synthetic fibre between 5 and 20 µm in diameter and having a length between 20 and 100 times the fibre diameter, bonded to the sheet of packaging material by an adhesive and having a sufficient density, relative to the size of fibre, to at least completely cover the surface. Advantageously, the down has a fibre density between 10 and 100 g/m². Optionally, the sheet of packaging material is of paper having mechanical characteristics adapted to to the material for insertion into the container and to the size thereof. Alternatively the sheet can be of cellophane or the like or of any other packaging material. In a preferred embodiment the down is made up of 1.5 denier polyamide resin fibres (about 12 µm in diameter) and 0.6 mm long, the density of fibres on the surface being between 50 and 80 g/m² and the fibres being bonded to the sheet of packaging material by an acetovinyl adhesive. In an alternative embodiment of the invention, the surface rough portions are made up of unevenness, scales, projections and the like, adapted to constitute obstacles to gripping by limbs of insects on the surface. Optionally, the material forming the surface roughness is applied to a surface of the sheet packaging material before packaging the container, so that the coated surface faces the exterior of the packaged container. Alternatively, the material forming the surface roughness is applied to the outer surface of the container after packaging, depending also on the method of manufacturing the container and the geometrical characteristics thereof. Materials in sheet form having a downy surface can be obtained by depositing coats of fibres of constant length, electrostatically charged, on to a sheet the surface of which is covered with adhesive and underneath which a magnetic means is disposed. Under these conditions the coats are all disposed substantially vertically on the surface of the sheet and remain bonded thereto by the adhesive, thus producing a velvet-like material also called "flock". The method can be applied to sheet material before packaging or to the container after packaging; the choice between the two possibilities will depend on the geometrical shape of the container. When the method is applied after packaging, the container must be such that the coat can be deposited over its entire surface without leaving even the smallest parts uncovered, since they would be attacked and perforated. In the case where a sheet is used for packaging after the down has already been formed, the packaging must have a shape such as to ensure complete closing without the surface of the down interfering with the adhesion between the closing edges. Cellulose materials such as paper or cellophane are advantageous, particularly for ecological reasons, for forming the packaging sheet which has to be given a downy surface. These materials are economic and compatible with food products. From the ecological viewpoint, after the biodegradable supporting layer has disintegrated, the down bonded thereto breaks up without substantially polluting the environment. In general, the resistance of "flock" material to insects depend on the material and thickness of the supporting sheet and on the material forming the surface down. The resistant of packaging according to the invention to the action of insects is due to the fact that the down prevents the limbs of insects from coming in contact with the surface of the material and gripping it so as to exert the force necessary for perforating it. To this end, the coverage of the material by down must be total, preferably so that the coats overlap so that there is no space between adjacent coats through which the tapering ends of insect limbs could make contact with the supporting sheet. One possible embodiment of the invention is illustrated in the following examples, which should not be regarded as in any way limiting the scope of the invention, which is defined in the claims. From the experimental viewpoint, note that paper by itself has very little resistance to the perforating activity of insects, and therefore more clearly shows the advantage of applying the down according to the invention. Examples 1) Preparation of the packaging Packaging was prepared from the following starting materials: Supporting sheet: Paper made from recycled cellular fibre 100 µm thick and weighing 75 g/m²; Adhesive: Acetovinyl adhesive; Down: 1.5 denier polyamide fibre (diameter about 12 µm) and 0.6 mm high; the surface density of the applied fibre was between 55 and 75 g/m². These materials were used to prepare a sheet which was then cut into strips of material 7 cm wide and 24 cm long. Bags were made by folding the strips in two and welding them on three sides. Some bags had down facing the exterior and some had down facing the interior. The bags were welded with tape adhesive on both sides and about 1 cm wide, and were reinforced with metal tacks. Three tacks were used on each long side and two on the short side for closing. Other bags of identical size were made in the same manner from the supporting sheet by itself, without down. 2) Tests of resistance to perforation About 20 g of "Superfino Arborio" type rice were placed in all the bags manufactured as in Section 1). The bags with down on the outside were intended for testing the resistance of the material according to the invention, whereas the paper bags without down were for use as controls. Finally, the bags made with down on the internal surface provided a control for imponderable factors such as any insect-repelling properties of the adhesive substance or the like. Tests were made on three species of insect noted for their very high perforation capacity and tendency to penetrate food packaging, as follows: Rhyzopertha dominica (F) (Coleoptera, Bostrychidae); Tribolium confusum du Val (Coleoptera, Tenebrionidae); Ephestia kühniella (Zeller) (Lepidoptera, Phycitidae). Each species was present in five vessels, each containing a single species. The five vessels holding Tribolium confusum contained the following respectively at the beginning of the test: 201 adults and 208 larvae; 206 adults and 200 larvae; 200 adults and 199 larvae; 201 adults and 200 larvae; 200 adults and 200 larvae. 100 g of wheat flour serving as a food substrate were placed in each vessel. The five vessels containing Ephestia kühniella each initially contained 16 larvae aged III and IV and 30 g of wheat flour was placed in each vessel. 300 g of wheat and maize flour, mixed in equal parts and taken from Rhyzopertha dominica breeding establishments were placed in each of the five vessels holding Rhyzopertha dominica. Since this substrate was massively infested, it was impossible to determine the number of insects in various stages of development present, but in any case there were hundreds of individuals. Three bags manufactured as in Item 1) (one of each type) were placed vertically in each vessel. The vessels were kept at 25°C and at 75 per cent relative humidity. The photoperiod (ratio of light to darkness) was 14 : 10. The bags were checked weekly for about 4 months and monthly during the subsequent 8 months. 3) Results The variation in perforations in bags subjected to activity of various insects is shown in the graphs reproduced in the accompanying drawings, in which: Fig. 1 is a graph in which the ordinate shows the number, with respect to time, of bags of the aforementioned three different kinds, i.e. external down, internal down and without down, which were perforated by Rhyzopertha dominica ; Fig. 2 is a graph in which the ordinate shows the number, with respect to time, of bags of the three different kinds described (with external down, with internal down and without down) perforated by Tribolium confusum ; and Fig. 3 is a graph in which the ordinate shows the number, in dependence on time, of bags of the three different kinds described (external down, internal down and without down) perforated by Ephestia kühniella . In the three drawings, the continuous line shows the increase in perforation of bags with external down; the chain-dotted line shows the increase in the perforation of bags with down facing the interior, and the chain line shows the increase in perforation of bags of paper without down. The abscissae show the dates when the state of preservation of the bags was checked. In the test with Tribolium confusum it was found that, three months after the beginning of the test, 8 of the control bags (paper or with internal down) had been perforated whereas only two bags with external down had a few minute cracks, presumably due to the mechanical thrust exerted by the rice in combination with moisture absorbed by the paper. The test with Ephestia kühniella showed that five months after the beginning, all the paper bags were perforated whereas none of the bags with external down were perforated. The first paper bag was perforated after seven days whereas the first bag with external down according to the invention was perforated after six months. The test with Rhyzopertha dominica showed that after 15 days, all five paper bags had been perforated. After a month, the papers with internal down had also been perforated by insects. The first bag with external down was perforated after 3 months, whereas it took a year before all five bags had been perforated. Since the material according to the invention can be used for wrapping or containers suitable for prolonged preservation of goods and food inserted therein, the supporting sheet must be able to withstand this period of storage without deterioration. The material used for this purpose can be either paper or cellophane or other materials compatible with the packed product and the storage conditions. It has been found, however, that any packaging material, whether in sheet or other form, can be used as a support for down and as a result is made more resistant to attack by insects. The down material is advantageously a synthetic fibre. Vegetable fibres such as cotton are unsuitable for the purpose since insects may attack and demolish them and thus uncover the supporting sheet, which will then be exposed unprotected to further attack by the insects. Polyamide resin fibre (commercially known as "Nylon") has been found suitable, since it is not attacked by insects and it efficiently protects the supporting sheet.

Claims: Food-product packaging resistant to perforation by insects, characterised in that it comprises a container made of sheet packaging material compatible with the product to be packed or wrapped and with use thereof, the surface of the material facing the exterior of the packaged container presenting a uniform distribution of rough portions having minute dimensions and covering the total surface and made of synthetic material not eatable by insects. Food-product packaging resistant to perforation by insects according to claim 1, characterised in that the rough portions have dimensions substantially less than 50 µm. Food-product packaging resistant to perforation by insects according to claims 1 and 2, characterised in that the uniform distribution of rough portions having minute dimensions is in the form of a down of synthetic material firmly adhering to the surface. Food-product packaging resistant to perforation by insects according to claim 3, characterised in that the down is made up of spun synthetic fibre between 5 and 20 µm in diameter and having a length between 20 and 100 times the fibre diameter, bonded to the sheet of packaging material by an adhesive and having a sufficient density, relative to the size of fibre, to at least completely cover the surface. Food-product packaging resistant to perforation by insects according to claim 4, characterised in that the down has a fibre density between 10 and 100 g/m². Food-product packaging resistant to perforation by insects according to claim 1, characterised in that the sheet of packaging material is of paper having mechanical characteristics adapted to to the material for insertion into the container and to the size thereof. Food-product packaging resistant to perforation by insects according to claim 1, characterised in that the sheet of packaging material is of cellophane. Food-product packaging resistant to perforation by insects according to claim 3, characterised in that the down is made up of polyamide resin fibres. Food-product packaging resistant to perforation by insects according to claim 8, characterised in that the down is made up of 1.5 denier polyamide resin fibres (about 12 µm in diameter) and 0.6 mm long, the density of fibres on the surface being between 50 and 80 g/m and the fibres being bonded to the sheet of packaging material by an acetovinyl adhesive. Food-product packaging resistant to perforation by insects according to claims 1 and 3, characterised in that the surface rough portions are made up of unevenness, scales, projections and the like, adapted to constitute obstacles to gripping by limbs of insects on the surface. Food-product packaging resistant to perforation by insects according to claim 1, characterised in that the material forming the surface roughness is applied to a surface of the sheet packaging material before packaging the container, so that the coated surface faces the exterior of the packaged container. Food-product packaging resistant to perforation by insects according to claim 1, characterised in that the material forming the surface roughness is applied to the outer surface of the container after packaging.

Inventors: DOMENICHINI, GIORGIO, PAGANI, MARCO
Applicants: CONSIGLIO NAZIONALE DELLE RICERCHE
Application year: 1988
Main classification: B65D81
IPC codes: B65D65, B32B5, B65D81, A23L3