Sensor for high pressure processing of articles
View Patent ↗A pressure sensor device and its use for confirming achievement of a selected pressure in a high pressure process (HPP) for sanitizing food is disclosed. The device includes at least a base and a sheet, each of which is substantially impermeable to the working fluid of the HPP and is deformable at the selected pressure. Microcapsules interposed between flat overlapping portions of the base and sheet contain a color former and burst upon pressurization of the environment surrounding the device. Release of the color former is detected to confirm that the pressurization occurred. The device can be associated with one or more foodstuffs (e.g., a packaged food product or a group of such packages) and remain associated therewith to continuously indicate that the foodstuff(s) have been subjected to the selected pressure and are therefore sanitized.
1. An assembly for indicating achievement of a selected ambient pressure in a high pressure process for treating a foodstuff using a working fluid, the assembly comprising the foodstuff reliably associated with a pressure sensor device that comprises a base, a sheet, and a plurality of microcapsules,
each of the base and the sheet being substantially impermeable to the working fluid, being deformable at the selected ambient pressure, and bearing a substantially flat portion;
the substantially flat portions of the base and sheet being disposed in a substantially parallel, opposed conformation defining an overlapping region having lateral dimensions and an average separation distance,
the plurality of microcapsules being interposed between the base and the sheet in the overlapping region;
the microcapsules containing a color former and having a compressive bursting strength less than the selected ambient pressure; and
at least one of the base and the sheet having a viewing portion adapted to permit detection of color former released from the microcapsules by external visual observation of the device,
whereby when the assembly is subjected to the selected ambient pressure, at least some microcapsules in the overlapping region burst, the color former is released from the microcapsules, and release of the color former can be detected by external visual observation of the device.
2. The assembly of claim 1 , wherein at least a fraction of the microcapsules are disposed within a portion of the overlapping region that contains a compressible fluid.
3. The assembly of claim 2 , wherein the fluid is air.
4. The assembly of claim 1 , wherein the base has the form of a second sheet.
5. The assembly of claim 4 , wherein each of the base and the sheet is a polyester film having a thickness of about 2 to 10 mils and at least one of the base and the sheet is transparent.
6. The assembly of claim 1 , wherein the microcapsules are bound to the base.
7. The assembly of claim 1 , wherein the microcapsules are bound to the sheet.
8. The assembly of claim 1 , wherein the compressive bursting strength of the microcapsules is not more than 200 megaPascals (MPa).
9. The assembly of claim 1 , wherein one of the base and the sheet bears the microcapsules and the other bears a color developer that reacts with the color former to generate a colored product.
10. The assembly of claim 1 , wherein one of the base and the sheet bears the microcapsules and the other is transparent and bears an absorbent material for absorbing the color former when it is released from the microcapsules.
11. The assembly of claim 1 , wherein the average separation distance is at least 100 times smaller than the minimum lateral dimension of the overlapping region.
12. The assembly of claim 1 , wherein the device is reliably associated with a plurality of foodstuffs.
13. The assembly of claim 12 , wherein the device is reliably associated with a rack that holds the plurality of foodstuffs.
14. The assembly of claim 13 , wherein the foodstuffs cannot be removed from the rack without displacing the device from the rack.
15. The assembly of claim 1 , wherein the device is reliably associated with a package that contains the foodstuff.
16. The assembly of claim 15 , wherein the package is selected from the group consisting of a flexible bottle and a flexible pouch.
17. The assembly of claim 1 , wherein the device is sealed within a sheath that is substantially impermeable to the working fluid.
18. The assembly of claim 17 , wherein the sheath is substantially evacuated.
19. A method of confirming achievement of a selected ambient pressure in a high pressure process for treating a foodstuff using a working fluid, the method comprising reliably associating the foodstuff with a pressure sensor device that comprises a base, a sheet, and a plurality of microcapsules,
each of the base and the sheet being substantially impermeable to the working fluid, being deformable at the selected ambient pressure, and bearing a substantially flat portion;
the substantially flat portions of the base and sheet being disposed in a substantially parallel, opposed conformation relative to one another to define an overlapping region having lateral dimensions and an average separation distance,
the plurality of microcapsules being interposed between the base and the sheet in the overlapping region;
the microcapsules containing a color former and having a compressive bursting strength less than the selected ambient pressure; and
at least one of the base and the sheet having a viewing portion adapted to permit detection of color former released from the microcapsules by external visual observation of the device,
subjecting the foodstuff to the process, and
visually observing the viewing portion of the device, whereby visual detection of color former at the viewing portion confirms that the selected ambient pressure was achieved.
20. The method of claim 19 , wherein at least a fraction of the microcapsules are disposed within a portion of the overlapping region that contains a compressible fluid.
21. The method of claim 20 , wherein the fluid is air.
22. The method of claim 19 , wherein the base has the form of a second sheet.
23. The method of claim 22 , wherein each of the base and the sheet is a polyester film having a thickness of about 2 to 10 mils and at least one of the base and the sheet is transparent.
24. The method of claim 19 , wherein the microcapsules are bound to the base.
25. The method of claim 19 , wherein the microcapsules are bound to the sheet.
26. The method of claim 19 , wherein the compressive bursting strength of the microcapsules is not more than 200 megaPascals (MPa).
27. The method of claim 19 , wherein one of the base and the sheet bears the microcapsules and the other bears a color developer that reacts with the color former to generate a colored product.
28. The method of claim 19 , wherein one of the base and the sheet bears the microcapsules and the other is transparent and bears an absorbent material for absorbing the color former when it is released from the microcapsules.
29. The method of claim 19 , wherein the average separation distance is at least 100 times smaller than the minimum lateral dimension of the overlapping region.
30. The method of claim 19 , wherein the device is reliably associated with a plurality of foodstuffs.
31. The method of claim 30 , wherein the device is reliably associated with a rack that holds the plurality of foodstuffs,
32. The method of claim 31 , wherein the foodstuffs cannot be removed from the rack without displacing the device from the rack.
33. The method of claim 19 , wherein the device is reliably associated with a package that contains the foodstuff.
34. The method of claim 33 , wherein the package is selected from the group consisting of a flexible bottle and a flexible pouch.
35. The method of claim 19 , wherein the device is sealed within a sheath that is substantially impermeable to the working fluid.
36. The method of claim 35 , wherein the sheath is substantially evacuated.
37. In a high pressure process for treating a foodstuff using a working fluid, the improvement comprising reliably associating the foodstuff with a pressure sensor device that comprises a base, a sheet, and a plurality of microcapsules,
each of the base and the sheet being substantially impermeable to the working fluid, being deformable at the selected ambient pressure, and bearing a substantially flat portion;
the substantially flat portions of the base and sheet being disposed in a substantially parallel, opposed conformation relative to one another to define an overlapping region having lateral dimensions and an average separation distance,
the plurality of microcapsules being interposed between the base and the sheet in the overlapping region;
the microcapsules containing a color former and having a compressive bursting strength less than the selected ambient pressure; and
at least one of the base and the sheet having a viewing portion adapted to permit detection of color former released from the microcapsules by external visual observation of the device, and
visually observing the viewing portion of the device after subjecting the foodstuff to the process, whereby visual detection of color former at the viewing portion confirms that the selected ambient pressure was achieved.
38. The improvement of claim 37 , wherein at least a fraction of the microcapsules are disposed within a portion of the overlapping region that contains a compressible fluid.
39. The improvement of claim 38 , wherein the fluid is air.
40. The improvement of claim 37 , wherein the base has the form of a second sheet.
41. The improvement of claim 40 , wherein each of the base and the sheet is a polyester film having a thickness of about 2 to 10 mils and at least one of the base and the sheet is transparent.
42. The improvement of claim 37 , wherein the microcapsules are bound to the base.
43. The improvement of claim 37 , wherein the microcapsules are bound to the sheet.
44. The improvement of claim 37 , wherein the compressive bursting strength of the microcapsules is not more than 200 megaPascals (MPa).
45. The improvement of claim 37 , wherein one of the base and the sheet bears the microcapsules and the other bears a color developer that reacts with the color former to generate a colored product.
46. The improvement of claim 37 , wherein one of the base and the sheet bears the microcapsules and the other is transparent and bears an absorbent material for absorbing the color former when it is released from the microcapsules.
47. The improvement of claim 37 , wherein the average separation distance is at least 100 times smaller than the minimum lateral dimension of the overlapping region.
48. The improvement of claim 37 , wherein the device is reliably associated with a plurality of foodstuffs.
49. The improvement of claim 48 , wherein the device is reliably associated with a rack that holds the plurality of foodstuffs,
50. The improvement of claim 49 , wherein the foodstuffs cannot be removed from the rack without displacing the device from the rack.
51. The improvement of claim 37 , wherein the device is reliably associated with a package that contains the foodstuff.
52. The improvement of claim 51 , wherein the package is selected from the group consisting of a flexible bottle and a flexible pouch.
53. The improvement of claim 37 , wherein the device is sealed within a sheath that is substantially impermeable to the working fluid.
54. The improvement of claim 53 , wherein the sheath is substantially evacuated.