Use of polymer film for packaging a culture medium

Abstract

A polymer film for packaging at least one microorganism culture medium includes at least one layer of polystyrene and at least one heat-sealing layer. The polymer film has an average water vapor permeability of between 30.0 g/m.sup.224 hours and 140.0 g/m.sup.224 hours, preferentially between 70.0 g/m.sup.224 hours and 120.0 g/m.sup.224 hours.

Claims

1. A polymer film for packaging at least one microorganism culture medium, said film comprising at least one layer of polystyrene and at least one heat-sealing layer, wherein at least one of the layers is microperforated so as to include perforations having sizes of between 10 m and 50 m and the film has an average water vapour permeability of between 30.0 g/m.sup.224 hours and 140.0 g/m.sup.224 hours.

2. The polymer film according to claim 1, wherein the film has a thickness of between 20 and 80 m.

3. A sachet containing at least one microorganism culture medium that are each deposited on a separate support, wherein the sachet is produced from the polymer film according to claim 1.

4. A process for packaging at least one microorganism culture medium, comprising: placing the culture medium or media on the heat-sealing layer of the polymer film according to claim 1; covering the culture medium or media with a portion, which has remained free, of said film or with another film, such that the heat-sealing layers are facing one another; and securing the edges of the film or of the two films, such that the culture medium or media is or are trapped in a sachet thus formed.

5. The packaging process according to claim 4, wherein the film(s) is (are) presterilized.

6. The packaging process according to claim 5, wherein the sterilization method is irradiation with radiation selected from the group consisting of gamma-rays and beta-rays.

7. The packaging process according to claim 4, wherein the securing step is a heat-sealing step at a temperature of between 100 and 170 C.

8. The packaging process according to claim 4, further comprising: placing the sachet inside a second sachet; and sealing said second sachet.

9. The packaging process according to claim 8, further comprising: placing the second sachet inside a third sachet; and sealing said third sachet.

10. The packaging process according to claim 9, wherein said second and/or third sachets are made from a material selected from the group consisting of cellophane, polyolefins and polyamides.

11. The polymer film according to claim 1, wherein the heat-sealing layer is a polyethylene, polypropylene, or polyvinyl chloride layer.

12. The packaging process according to claim 4, wherein each culture medium trapped in the sachet is deposited on a separate support.

13. A polymer film for packaging at least one microorganism culture medium, said film comprising at least one layer of polystyrene and at least one heat-sealing layer, wherein the film has a thickness of between 20 and 80 m and an average water vapour permeability of between 30.0 g/m.sup.224 hours and 140.0 g/m.sup.224 hours.

14. A sachet containing at least one microorganism culture medium that are each deposited on a separate support, wherein the sachet is produced from the polymer film according to claim 13.

15. A process for packaging at least one microorganism culture medium, comprising: placing the culture medium or media on the heat-sealing layer of the polymer film according to claim 13; covering the culture medium or media with a portion, which has remained free, of said film or with another film, such that the heat-sealing layers are facing one another; and securing the edges of the film or of the two films, such that the culture medium or media is or are trapped in a sachet thus formed.

16. The packaging process according to claim 15, wherein the film(s) is (are) presterilized.

17. The packaging process according to claim 16, wherein the sterilization method is irradiation with radiation selected from the group consisting of gamma-rays and beta-rays.

18. The packaging process according to claim 15, wherein the securing step is a heat-sealing step at a temperature of between 100 and 170 C.

19. The packaging process according to claim 15, further comprising: placing the sachet inside a second sachet; and sealing said second sachet.

20. The packaging process according to claim 19, further comprising: placing the second sachet inside a third sachet; and sealing said third sachet.

21. The packaging process according to claim 20, wherein said second and/or third sachets are made from a material selected from the group consisting of cellophane, polyolefins and polyamides.

22. The polymer film according to claim 13, wherein the heat-sealing layer is a polyethylene, polypropylene, or polyvinyl chloride layer.

23. The packaging process according to claim 15, wherein each culture medium trapped in the sachet is deposited on a separate support.

Description

(1) The objectives and advantages of the present invention will be understood more clearly on reading the following examples, which are in no way limiting, with reference to the drawing.

(2) FIG. 1 shows the measurements of the weights of the complete stacks of dishes week by week for batches BATCH 1 and BATCH 2 as a function of the storage temperatures.

EXAMPLE

(3) Various batches of Petri dishes are formed. Each of the batches contains ten agar culture media of Mac Conkey type, manufactured by the applicant.

(4) The first batch, BATCH 1, comprises three stacks of ten Petri dishes, each stack being packaged in a sachet made from a PS film comprising a layer of polystyrene, called FILM A, having a thickness of 30 m.

(5) The second batch, BATCH 2, comprises three stacks of ten Petri dishes, each stack being packaged in a sachet made from a reference film comprising a layer of cellophane, called FILM B, having a thickness of 30 m and a water vapour permeability of approximately 370 g/m.sup.224 h.

(6) The water vapour transmission coefficient of film A is determined by five measurements according to the abovementioned standard. The results are indicated in Table 1a below.

(7) TABLE-US-00001 TABLE 1a Water vapour transmission coefficient (g/m.sup.2.24 h) Standard Reference Results Mean Deviation FILM A: PS 97.3 97.3 97.2 99.4 95.7 97.4 1.3

(8) The mechanical characteristics of FILM A are indicated in table 1b below:

(9) TABLE-US-00002 TABLE 1b (MD: machine direction, TD: transverse direction). The values in this table obey a tolerance of 20%. Characteristics Methods Values Units Thickness NFT 54-101 30 m Corona treatment if necessary Density ISO 1183 1.036 Tensile strength ISO 527 MD: 34 TD: 30 Mpa Elongation at break ISO 527 MD: 6 TD: 5 % Tearing strength ISO 6383-1 MD: 20 TD: 5 N/mm Impact strength ISO 7765-1 <25 - method A g

(10) Each of the three stacks of the two batches thus formed is then stored for 11 weeks according to several temperature conditions. A first stack of each batch is thus stored at a temperature of between 2 and 8 C. A second stack of each batch is stored for 8 hours at 37 C., then at a temperature of between 2 and 8 C. A third stack of each batch is stored for 8 hours at 37 C., then for 6 days at a temperature of between 15 C. and 25 C. and finally at a temperature of between 2 and 8 C.

(11) The total weight of each stack of each batch is measured every week in order to determine the agar weight loss kinetics as a function of the storage and packaging conditions. The monitoring of the weight of the agar is an indicator for the amount of water lost by the agar.

(12) The results of these measurements are given in the table below and in relation to FIG. 1.

(13) Table 2 shows the monitoring of the weight, in grams, of the stacks of dishes, for each batch.

(14) TABLE-US-00003 TABLE 2 27 Sep. 1 Oct. 5 Oct. 16 Oct. 18 Oct. 2 Nov. 16 Nov. 30 Nov. 18 Dec. 2012 2012 2012 2012 2012 2012 2012 2012 2012 FILM B 2- 326.44 324.68 323.63 321.32 320.64 316.45 312.26 308.21 302.28 8 C. FILM B 326.49 322.38 321.28 318.60 317.82 313.29 309.04 305.84 300.46 8 h at 37 C., then 2-8 C. FILM B 321.59 314.70 309.90 306.78 306.16 301.48 297.24 293.64 288.50 8 h at 37 C., 6 days at 15- 25 C., then 2-8 C. FILM A 327.84 327.17 326.66 325.50 325.22 322.98 321.01 318.00 314.73 2-8 C. FILM A 328.14 326.16 325.73 324.52 324.25 322.34 320.78 319.06 317.26 8 h at 37 C., then 2-8 C. FILM A 328.32 324.97 322.52 321.28 321.02 318.90 317.23 315.52 313.57 8 h at 37 C., 6 days at 15- 25 C., then 2-8 C.

(15) Table 2 and FIG. 1 thus show a reduction in the agar weight loss kinetics due to the use of the films FILM A in comparison with a reference film FILM B.

(16) The results regarding the agar weight loss kinetics were obtained while maintaining an acceptable level of condensation inside the sachets using FILM A, contrary to the sachets using standard plastic films.

(17) A decrease in the agar weight loss kinetics is demonstrated whatever the storage conditions. The influence of the temperature on the agar weight loss kinetics is decreased due to the use of FILM A in comparison with the reference film FILM B used to produce the sachets. Indeed, all storage conditions taken into account, the agar weight loss is decreased for the batch using films FILM A. The stacks of batches stored at a temperature of between 2 and 8 C. in films FILM A exhibit in particular a slight decrease in weight as the weeks go by, in comparison with the stacks packaged in films FILM B. The improvement is even more notable for the stacks stored for 8 hours at 37 C., then for 6 days at a temperature of between 15 C. and 25 C. and finally at a temperature of between 2 and 8 C.

(18) Finally, better stability of the agar weight loss kinetics is also demonstrated, whatever the storage conditions, the measurements carried out on batches packaged by FILM B showing a greater variation in the agar weight loss kinetics over time.

(19) These results thus make it possible to envisage a reduction in the amount of agar able to be poured into a Petri dish, nevertheless making it possible to ensure a shelf life in keeping with current standards. Conversely, extended shelf lives can be achieved using films according to the invention by retaining a similar amount of poured agar. The use of a film according to the invention therefore allows a reduction in the manufacturing costs and/or an extension of the shelf life of the culture media.