IL47044A - Method and apparatus for automatic aseptic filling and packaging of foodstuffs - Google Patents

Abstract

1460134 Sterile packaging ALUMINIUMWERKE AG and BBC BROWN BOVERI & CO Ltd 12 March 1975 [10 April 1974] 10297/75 Heading B8C Packaging material is disinfected by high intensity ultra-violet radiation generated by high current, low pressure mercury discharge with a discharge current density of >1 A/cm.<SP>2</SP> and a mercury pressure of 5 Î 10<SP>-3</SP> to 5 Î 10<SP>-1</SP> Torr, the spectral radiation intensity on the material being at least 0À05 W/cm.<SP>2</SP> and exposure being for at least 1 second. The material may be heated before exposure. In one application for filling cups 1 with, e.g. cream, the cups are sterilized by exposure to infra-red radiation and then to ultra-violet radiation emanating from a housing 6 prior to filling by a unit F and closure by a web 2 which is similarly sterilized by apparatus in housings 7, 8. In an alternative application, a web is sterilized by ultra-violet radiation before being formed into a tube about a filling nozzle, the tube being transversely sealed to form discrete packages, Fig. 2 (not shown). [GB1460134A]

Description

7110 »3 50 w &»*»Β0Κ1 Method and ap ajp tiia for automatic aseptic filling and packaging o foodstuffs AluciinTiiiiwe^ke A a* and BBC B^tm I veri & CJompany Limi¾ed C. 44652 The invention concerns a method and apparatus for the automatic low-bacteria to aseptic filling and packing of foodstuffs which are previously disinfected or sterilised and then passed to the filling and packing plant, the packaging material being disinfected by means of high-intensity ultraviolet radiation.

The automatic aseptic filling and packing of foodstuffs is being used on an increasingly wide scale. To date, the aseptic packing of pre-sterilised (uperised) milk in packs made of a paper composite material has particularly wide acceptance. (The uperisation of milk is described, for example, in Industr,. alim. agr. 1956, p. 635 - 640.) The packs are predominantly tetrahedral or rectangular in shape and are made up by applying transverse seals to a tube of packaging material formed from a strip of packaging material drawn from a roll (cf. TARA 271 , February 1 9 »^ page 1 θ ) .

In general, "aseptic packing" can also be defined as the placing of a cold, commercially sterile foodstuff into a pre—sterilised container under sterile conditions, the container (if appropriate with a pre—sterilised lid) being closed in a sterile environment so as to produce an airtight package (Food Technology, August 1 72 , page 70 ) .

Another technique which has become very important is the low—bacteria packing of portions in, for example, deep—drawn prefabricated beakers which are then hot—sealed with refined aluminium foil. Common applications include the packing of yoghourt, soured milk, cream, and so on.

An essential feature of the known techniques is that there is no sterilisation of the contents by heating in the already sealed package, as is the case with canning and preserving techniques. The tedious heating process is thus eliminated without having to take into account deleterious changes in the contents as regards flavour or composition. Furthermore, the packages can be made of materials, in particular plastics, which cannot withstand elevated temperatures.

A particularly critical aspect of the known technologies is thaj^^ the packaging material must be so free from bacteria as to provide the greatest possible safeguard against infection of the previously sterilised or disinfected contents by bacteria, moulds and/or yeasts which could cause spoiling. Here it is pertinent to note that in the case of uperised milk, for example, a single bacterium in the pack can cause the milk to spoil.

A large number of methods and apparatus for disinfecting packaging materials have therefore been proposed and applied in practice. These are reviewed, for example, in "Verpackungs~Rundscb.au" 7 ( 1 970 ) pages 51 - * · Other references in the literature include Food Technology, September 1 973 , page 9 (disinfection with alcohol and ultraviolet radiation) and Food Technology, August 1 72 , pages 70 - 7^+ (e.g. disinfection with wet and high-temperature steam, the so-called "James Dole process").

In particular, a method is known from "Verpackungs-Rundschau" 7 ( 1 9 0 ) page 52/ 53 whereby packaging material is disinfected by means of high-intensity ultraviolet radiation. It is stated there that the ultraviolet wavelength of 25¾ nm has proved especially effect against all relevant micro-organisms. However, differ as regards their sensitivity to ultraviolet 3 radiation. Thorough destruction of all micro-orjanisras present can be achieved only with a very heavy radiation dose. On page 5 , op. cit. , it is mentioned that the high measured destruction rates are valid only when the distance from the light source is - k - very short, and that it is not known whether or how packages could be sterilised on the required scale and at a sufficient speed matched to the filling plant.

The object of the invention is, while clarifying the open questions stated above, to specify a method wherehy packaging material can be disinfected on an industrial scale by means of ultraviolet radiation on filling and packing machines.

This object is achieved in that with the method of the invention as described above, the ultraviolet radiation is generated by a high—current low-pressure mercury discharge with a discharge 2 current density of more than 1 A/cm and a mercury pressure of 5 x 10-3 to 5 x 10-1 Torr, the spectral radiation intensity of the 253· 7 nm line of the ultraviolet radiation on the packaging 2 material is set to at least 0.05 W/cm , and the packaging material is exposed to the ultraviolet radiation for at least 1 second.

A mercury discharge of the kind described above produces ultraviolet radiation having a spectrum which causes destruction of the relevant micro-organisms in a surprisingly effective manner. Although control of the radiation intensity is aimed basically at the 253.7 nm line, it is important that the ultraviolet spectrum should also contain significant proportions of the 18^.9 and 19k .2 nm lines. If the stated minimum radiation intensity and minimum time of exposure of the packaging materials to the ultraviolet are observed, the packaging material is surprising- ly disinfected to an extent which, in contrast to previous geryi eral expectations, makes difnfection by means of ultraviolet radiation practicable on an industrial scale.

Other features and details of the invention are explained below with reference to the drawings, in which: Figure 1 shows a filling and packing plant for the low-bacteria packaging of portion-size packs, Figure 2 shows a filling and packing plant for the aseptic packaging of a pre-sterilised liquid, such as uperised milk, Figure 3 shows in schematic form the arrangement of a folded discharge tube over a feed line of packing material, Figure k illustrates discharge tubes in a reflector over a feed line of packing material, and Figure 5 is a diagram showing the destruction rate K of various relevant micro—organisms in relation to the exposure t time of the packing material to the ultraviolet radia- 2 tion, for a radiation intensity of 0.3 V/cm .

In Fig. 1 the packing material 1 in the form of preshaped containers, e.g. deep-drawn beakers, is taken from a stack and conveyed in direction M. The packing material 1 is first exposed to infrared radiation IR and then to ultraviolet radiation UV from the discharge paths 5 of discharge tubes k located in a housing 6, 7» 8 which acts as a reflector. The reflector housing containing the UV radiation source is also termed the UV Under the filling station F the portion—size beakers are filled with the previously disinfected contents, e.g. yoghourt or cream.

Packing material 2, a sealing foil of aluminium 50 - 100 μπα thick, for example, running off a roll R1 , is first, like materi 1 , passed through an infrared channel and an ultraviolet channel and is then fed via a guide roll to the stamping and sealing station 10. Here, lids are stamped from the sealing foil and attached to the filled beakers by heat to give an airtight seal.

The completed portion-szj.'e packs then leave the machine on the right.

To keep the plant generally aseptic, sterile air St is blown in from above. This air could also be introduced horizontally from the side.

In Fig. 2, packing material 3, e.g. a paper composite laminated with plastic-coated aluminium foil, runs from roll R2 in direction M into a UV channel comprising two reflector housings 6, 7, 8 with discharge tubes k arranged on either side of the packing material 3· The packing material 3 is then shaped in a device (not shown) into a tube T, tranversely sealed at Q, and then ejected as a finished pack P. The liquid contents of the pack are fed in at F, a pipe which is introduced into the shaped tube.

As in Fig. 1 , the apparatus in Fig. 2 can also be provided with an IR channel before the UV channel.

The discharge tubes 4 are provided so that the packing material 1, 2, 3, in whatever form it occurs, is exposed to radiation of the correct intensity and with the wavelength spectrum specified by the invention. The tubes are conveniently of the form described in Swiss Patent specification No. 570,040, to which reference is made as appropriate. The desired ultraviolet radiation is emitted from the part of the discharge tube 4 denoted "discharge path 5".

Fig. 3 shows a folded discharge tube k over a feed line of pack ing material 1 , 2, 3. Each part of the discharge tube k extend ing over the full width of the packing material 1 , 2, 3 is to be considered as a discharge path 5, and thus the folded discharge tube k shown has four discharge paths 5 arranged in series and extending over the whole width of the packing material 1 , 2, 3.

The procedure of disinfection by means of ultraviolet radiation is as follows: The discharge tubes k are operated for example at 10 A/cm with o — a mercury temperature of 72 C, corresponding to about 6 x 10 " Torr. In this manner, intense ultraviolet radiation of wavelength 253· nm is generated with an efficiency of more than 20 whereby the spectrum also includes substantial proportions of the lines 184.9 and 1 .2 run. r Under such radiation, as will be described more fully below, all sporogenetxc and non-sporogeiEtic bacteria are killed at the required rate within a few seconds, while mould spores, particularly aspergillus niger, are more resistant.

It is often not necessary to kill all the mould spores present, as these are neither toxic nor pathogenic and, in sealed packs of milk for example, are also virtually incapable of multiplying.

If destruction of the mould spores is desirable, however, this is achieved in accordance with another important aspect of the invention by heating the packing material 1 , 2, 3 in the sterile part of the filling and packing plant to more than 60 C , e.g. to 80 - 90°C. It is known that mould spores are destroyed completely at such temperature within a few seasnds .

The packing material 1 , 2 is heated as shown in Fig. 1 by means of infrared radiation IR before the packing material is subjected to the ultraviolet radiation UV. The infrared radiation section can be kept short because the temperature created by the infrared radiation is retained in the UV channel owing to the dissipation of UV power, and even rises a few degrees, and thus the packing material is held for a sufficiently long time at the temperature necessary to kill the mould spores.

A UV radiation dose tested in practice (c . DIN 5031 Sheet 1 , / August I97O, para. 7) on packing materials is 1.5 Ws/cm , although measurement relates only to the 253· 7 nm line. Vith account taken of technically and industrially reasonable feed rates for the packing material, irradiation of the packing mater-ial with an intensity on the 253.7 nm line of 0.3 V/cm , and exposure of the material to the UV radiation of 5 seconds, has proved advantageous.

So that the discharge tubes h can emit not only on the 253· 7 nm line, but also on the lines 183·9 nm and 19^· 2 nm, their discharge paths 5 are provided with substances which do not absorb these lines. Such a substance is high-purity quartz, e.g. synthetic quartz. This not only makes available the ultraviolet spectrum important for killing micro-organisms, but also causes a ozone to be generated in considerable quantities from the atmospheric oxygen, and this has an added sterilising effect on the packing material and the surroundings.

It is very important that the feed line of packing material, regardless of its form (containers, flat strip), is irradiated uniformly and homogeneously. Achieving this has hitherto presented a serious practical problem. But here, too, the invention offers an effective remedy.

Homogeneous irradiation transverse to the direction of movement M of the packing material 1 , 2, 3 s obtained by arranging the straight sections of the discharge tubes k , i.e. the discharge paths 5» so that they extend across the full width of the line in s ries „ xe/in a plane E parallel to the plane of the irradiated line of packing. Arranging the discharge paths 5 in series transverse to direction M has the further advantage that any unequal ageing of the discharge paths is compensated more effectively.

Homogeneous distribution over a defined distance in the direction of movement M is achieved by means of a reflector. This is highly reflective for the short-wave ultraviolet and consists of highly polished anodised aluminium, for example. Its reflectivity is better than 0.75· The reflector comprises an upper portion 6 and two side pieces 7» 8· These extend from the upper portion 6, preferably vertically, towards the feed line of packing material 1, 2, 3· Side piece 7 is at the entrance to the XJV channel, and side piece 8 at the exit.

This arrangement of the reflector not only creates a defined radiation section, but also produces highly homogeneous and diffuse radiation on the packing material in a manner not immediately predictable. One reason for this at first surprising result is that the high-current low-pressure mercury discharge as operated with the parameters of the invention is optically narrow, i.e. the radiation comes uniformly from the whole volume of the discharge, and no absorption takes place. The optical laws for point, line and area sources cannot, therefore, be applied to / a reflector of this kind.

The discharge paths 5 and the reflector 6, 7, 8 are advantageously arranged in a housing having openings to the outside which are as small as possible and forming a seal as tight as possible at the entry and exit of the packing material 1 , 2, 3· This housing screens the surroundings from the UV radiation and also prevents dissipation of the ozone produced by the radiation, particularly in the direction of the filling station F. The housing can also consist of the reflector itself 6, 7, 8, as shown in Fig. 1 and 2.

The housing or the reflector can be equipped with an exhaust device for the ozone formed. The electrode spaces of the discharge tubes k are conveniently outside the housing or reflector, located side by side in a special lamp enclosure.

The reflector must be of a suitable shape and size so that the UV radiation at the packing material is as homogeneous and diffuse as possible. Determining such dimensions is described with reference to Fig. 4: So that the radiation intensity I on the packing material fluc~ tuates by less than 10 i.e.4 I/I = 10 the condition: a/d ^ 0.5 must be observed when using a reflector of reli'ec t ivi ty R ^ 0.75· Here, a is the vertical distance between the axis of a discharge path 5 and the packing material 1 , 2, 3.

The vertical distance c of plane E in which the discharge paths liois itself of secondary importance, but it should be as small as possible, and in particular smaller than the distance d between the axes of two discharge paths. Edge effects can then be more effectively avoided.

Also to minimise edge effects, e should be as small as possible, and b as large as possible. Here, e is the shortest distance between the axis of the outermost discharge path 5' and the neighbouring side piece 7» 8, and b is the length of a side piece 7> S from plane E towards the packing material. If, in particular, e < 1.5 D (where D = diameter of discharge path 5) and a-b = f 10 mm, then Δΐ/I ^ 10 $ over the entire line of packing material 1, 2, 3 from inlet side piece 7 to outlet side piece 8.

Homogeneous and diffuse ultraviolet radiation as described above has the following advantages, among others: - The interior of preformed containers is uniformly irradiated, in particular without shadows. Surprisingly, the interior of beakers 3 cm deep and 6 cm wide is disinfected at all points just as quickly as a flat strip (with the same discharge tubes and the same reflector).

- The discharge tubes k do not have to be matched to a certain feed rhythm, i.e. it is immaterial at which point of the radiated area a pre armed container stops between feed movements.

Fig. 5 shows the result of microbiological disinfection tests.

A low-pressure high-current mercury discharge of 10 A/cm" and _2 6 10 Torr was used, with a radiation intensity on the 253· 7 2 run line of 0.3 V/cm at the test substrate.

Refined spore cultures of the tested bacteria and moulds were applied to defined surfaces in defined dilutions in the range 3 8 10 - 10 per smear, and partly dried. The cultures were then exposed for different times to the ultraviolet radiation, and afterwards washed off and incubated. The reduction of microorganisms was then determined with the aid of absolute sterility tests.

Tests were performed for the following organisms: Bacillus subtilis (spores) Bacillus stearothermophilus (spores) Escherichia coli Mucor mucedo Aspergillus Niger Penicillium chrysogenum Escherichia coli and Mucor mucedo were reduced in 2 to 3 seconds g at a rate K of more than 10 . The results for the other micro-o¾sanisms tested can be seen in Fig. 5· In summary : Ϊ With a spectral (253.7 nm) radiation intensity of 0.3 W/cm , the effect of the total short-wave UV radiation is such that - all sporogenetic bacteria with a radiation time of 5 sesmds undergo a reduction rate > 1 (Subtilis and Stearo thermophilus most resistant) with initial counts of up to 10 on areas ί 1 cm , - with a radiation time of 5 seconds all non-sporogenetic bacteria undergo even much high reduction rates, and - in the case of mould spores, radiation times of up to 0 seconds are necessary (Aspergillus Niger most resistant) to achieve high reduction rates (½ 10^).

In accordance with the invention, the combined infrared/ultraviolet technique as described above is used to avoid the possibly-long times necessary to destroy mould spores.

For the sake of completeness it may also be mentioned that it would be perfectly practicable to irradiate packing matjerials 1 and 2 of Fig. 1 on both sides, i.e. not only on the contents side, but also on the outside. This would eliminate the danger of the sterile space becoming infected by the packing material.

The method of the invention, together with the apparatus for implementing it,, is used with particular success for filling and packing liquids or pastes in soft or semi-rigid containers, and thus especially for packing uperised milk in continuous—tub/^ type containers, or for putting yoghourt, soured milk, cream, etc. in portion-size packs. Hitherto, disinfection with steam or hydrogen peroxide H^C^ has been mainly used in these cases. But steam disinfection presents serious mechanical problems because the steam is highly corrosive. Disinfection with H 0 presents a further problem in that there must be adequate safeguards to keep the chemical away from the food so that the method can be at all legally acceptable.

None of these problems arise with the method and apparatus of the invention.

Since with portion-size packs the foil cover is coloured and printed, and is particularly susceptible to distortion, the use of UV disinfection according to the invention for the foil cover is of very special significance. It is also possible to employ a classical method of disinfection, e.g. the H 0

Claims (1)

WHAT WE CLAIM IS: £ 1. A method for the automatic low—bacteria to aseptic illing and packing of foodstuffs which are previously disinfected or sterilised and then passed to the filling and packing plant, the packaging material being disinfected by means of high—intensity ultraviolet radiation, in which the ultraviolet radiation (UV) is generated by a high—current low— ressure mercury discharge \tfith 2 a discharge current density of more than 1 A/cm and a mercury -3 -1 pressure of 5 x 1 0 to 5 x 1 0 Torr, the spectral radiation intensity of the 253 . 7 run line of the ultraviolet radiation (UV) on the packaging material/is set to at least 0 . 05 W/cm , and the packaging material —3 , -^L) is exposed to the ultraviolet radiation (UV") f r at least 1 second. 2 . A method as claimed in Claim 1 , in which the packaging material — 2 i ) is heated to more than 60°C in the filling and packing plant before being exposed to the ultraviolet radiation (uv). 3 . A method as claimed in Claim 1 , in which the packaging material (•1 » .2 . 3 ) is heated by means of infrared radiation (IK) . k . A method as claimed in Claim 1 , in which the packaging material -T —3-j — 3-) is exposed to the 253 · 7 nm line with a spec tral / 2 radiation of at least 1 . 5 Ws/cin . 5. A method as claimed in Claim 4 , in which the spectral radia-j 3* tion intensity of the 253 · 7 nm line on the packing material -i-p—3 3 ) is set to at least 0. 3 W/cra*" and the packing material — — 3-)· remains in the ultraviolet radiation (UV) for at least 5 seconds . 6. A method as claimed in Claims ¾ or 5 i in which the packing material -(4-?—*τ— 3 s heated to 80 - 9 °C immediately before exposure to the ultraviolet radiation (UV) . 7. Apparatus for implementing the method as claimed in Claim 1 , comprising at least one discharge tube (^f) , the mate rial surround ing the discharge path J^i of which is transparent at least for the wavebands 184.9 nm, 1 . 2 nm and 253 . 7 nm. 8. Apparatus as claimed in Claim 7 > i which at least two discharge paths are provided, arranged one behind the other with respect to the direction of movement (*W of the line of packing material ( 1 >—3-;— 3" an<* extending across the whole width of the packing material —3-?— 3-^ , the .discharge paths i^) lying in a plane parallel to the plane of the irradiated portion of the line of packing material (+- — — 3-)-. 9· Apparatus as claimed in Claim 8, in which the discharge paths (^) are enclosed by a reflector comprising an upper part {&] above, and parallel to, the plane of the discharge paths , and two side pieces ^ f-,—8— which extend from the upper part to the line of packing material (-4-,—3-,—3-) at those ' points at which the ultraviolet radiation begins and ends, respectively. 10. Apparatus as claimed in Claim f in which the discharge paths ^) are located in a housing enclosing the space between the discharge paths { ) and the line of packing material (4-,—3-;—3-). 11. Apparatus as claimed in Claim 10, in which the housing is provided with a device for extracting ozone (0 ). 12. Apparatus as claimed in Claim 9» in which the reflectivity of the reflector material is better than 0.75 and the two side pieces ^f-;—8-)· are approximately perpendicular to the upper- part 13· Apparatus as claimed in Claim 1 , in which the ratio of the vertical distanceQ etween the plane (JE?) of the discharge paths and the line of packing material (4-,— —3- to the dxstanc etween two adjacent discharge paths J^) is at least 0.5, and/or the vertical distance (c) between the plane (E) of the discharge path $) the upper part i^f) of the reflector is smaller than the distance (-fo*j between two adjacent discharge paths (^) , and/or the shortest distance between the two outer discharge paths [^f) and the adjacent side .piece — is smaller than twice the diameter (f) of one discharge path (jif) , and the shortest distance ^) between the side pieces ?-, 8ή and the line of acking material {Δ-,—2-,—2_- is less than 10 mm.

1. . Application of the method as claimed in Claim 1 for illin^i^ and packing liquids or pastes in soft or semi-rigid containers. 1 5. Application of the method as claimed in Claim 1 '+ for filling and packing uperised milk. 1 6 . Application of the method as claimed in Claim 1 k for filling and packing containers comprising a composite packing material formed from a longitudinally and transversely sealed tube of packing material. 1 7. Application of the method as claimed in Claim 1 4 for filling and packing preformed containers which after filling are sealed with a foil cover. 1 8 . Application as claimed in Claim 1 7 » whereby- only the foil cover is disinfected by means of ultraviolet radiation, whereas the containers are disinfected by another method.