GB2541044A

GB2541044A - Disinfection of foodstuffs

Info

Publication number: GB2541044A
Application number: GB1604145.1A
Authority: GB
Inventors: Robert Snowball Malcolm
Original assignee: Ultra Biotecs Ltd
Current assignee: Ultra Biotecs Ltd
Priority date: 2015-03-10
Filing date: 2016-03-10
Publication date: 2017-02-08
Also published as: GB201604145D0; GB201504087D0

Abstract

An apparatus for disinfecting foodstuffs comprises a liquid tank 1, a conveyor 8 for conveying foodstuff 13 into, through, and out of the liquid tank, and at least one ultrasonic transducer 6 for producing ultrasonic waves through the liquid and into the foodstuff 13 being conveyed through the tank. Means (not shown) may be provided for causing liquid to flow in a direction opposite to the conveying direction. Conditioning means 15 may be provided for cleaning or sanitising the liquid, and may comprise filtration means, heating means, and/or means for applying ultraviolet light of a germicidal wavelength. The heating means may be provided vertically above the ultrasonic transducer such that any bubbles emitted by the heating means do not interfere with passage of the ultrasonic waves. The conditioning means may apply a surfactant to the liquid. The foodstuff 13 may be conveyed in baskets 12, and may follow a serpentine or convoluted path through the tank. A second tank having an ultrasonic transducer may be provided (see figure 4). A method for disinfecting foodstuffs by conveying them through a liquid tank subject to ultrasonic waves is also claimed. The foodstuff is preferably meat.

Description

DISINFECTION OF FOODSTUFFS Background of the invention

This invention relates a method and apparatus for the sterilisation or disinfection of foodstuffs and in particular but not solely to meat.

The shelf life of food is substantially shortened due to the presence of micro- organisms in the food, which can cause the food to deteriorate. Not only does shelf life affect the economic viability of food producers but it has a direct effect on public health, since the presence of certain micro-organisms in food can be hazardous if the food is ingested. These problems can be exacerbated if the food is not kept sufficiently refrigerated or undercooked, since the micro-organisms in the food can multiply rapidly.

In order to overcome the above-mentioned problems, it has been proposed to pasteurise food. However, a disadvantage of pasteurisation is that the process is lengthy and can only be used on certain types of food. Furthermore, the pasteurisation process affects the taste of the food and is costly to perform, since it uses a substantial amount of energy, a great deal of which is discharged into the working environment.

In one known method, the food is packaged in an atmosphere which inhibits the fast reproduction of micro-organisms. One such an approach is to package the food product within a carbon dioxide atmosphere. This has proved to be difficult to control, environmentally unfriendly and expensive to run. It also does not kill pathogenic microorganisms merely slows down their reproduction rate.

Tests carried out by the inventor have shown that the new process is particularly good at disinfecting the surface of meat without imparting any taste, change of texture or change of colour.

The micro-organisms which infect meat are particularly difficult to disinfect without changing the organoleptic qualities of the meat, Campylobacter on chicken and Ecoli 0157 on beef being particularly difficult to eradicate.

Another feature of meat is that its surface is covered with micro-cracks, fissures and pores which provide protection for the micro-organisms and prevent easy access to disinfectants.

Thermal disinfection processes such as steam or water scalding seriously degrade the product and are not acceptable to either the food manufacturers or the retailers.

Strong chemicals and biocides are not acceptable because they impart objectionable tastes and or smells. UV disinfection although being efficient and fast in killing micro-organisms is unable to thoroughly disinfect meat as it can only kill micro-organisms that are exposed to the UV light; unfortunately a high proportion of the micro-organisms are not exposed but hidden from the UV light.

Drawings

Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a side view of an ultrasonic tank with support gantry, deep narrow tank; Figure 2 shows a part sectional side view of ultrasonic tank with submergible UV disinfector, deep narrow tank;

Figure 3 shows a plan view of ultrasonic tank with submergible UV disinfector, shallow wide tank;

Figure 4 shows a side view of two processed in series.

Summary of the invention

Aspects of the invention are as set out in the appended claims. It will be appreciated from the discussion above that the embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. In the context of the present disclosure other examples and variations of the apparatus and methods described herein will be apparent to a person of skill in the art. A solution to the problem of disinfecting foodstuffs such as meat is a process which removes the micro-organisms from the surface and pores of the meat without changing its organoleptic qualities into a medium (like water) such that they can then be exposed to some form of disinfection and be deactivated or killed.

With reference to Figure 1, an aspect of the present disclosure provides an apparatus for disinfecting foodstuffs, comprising a tank 1 for holding a volume of liquid, a conveyor 8 configured to convey a foodstuff 13 into the volume of liquid, through the volume of liquid in a conveying direction transverse to a depth of the tank 1, and out of the volume of liquid, to disinfect the foodstuff 13, and at least one ultrasonic transducer 6 configured to produce ultrasonic waves through the volume of liquid and into a foodstuff 13 being conveyed through the volume of liquid. The liquid may be water.

The depth of the tank 1 may correspond to the length of one of the short sides 9, 11 of the tank 1 from the base of the tank 1 to the water level 7, for example as shown in Figure 1. The conveying direction may be, for example, in a direction from one short side 9 of the tank to the other short side 11 of the tank.

The apparatus may further comprise a flow provider for flowing the volume of liquid in a fluid flow direction opposite to the conveying direction. For example, the flow provider may circulate the volume of fluid in the tank 1. The apparatus may also comprise a conditioner 15 for conditioning the volume of liquid to perform at least one of: treating the volume of liquid to remove oil, fat and general debris from the volume of liquid; and disinfecting the volume of liquid. For example, the conditioner 15 may comprise a filter, a heater such as a heating element, and/or a UV source such as a UV lamp. The conditioner 15 may be configured to provide a surfactant in the volume of liquid to lower the surface tension of the volume of liquid relative to its normal surface tension at standard ambient temperature and pressure. The conditioner 15 may be configured to heat the volume of liquid to a selected temperature range, such as 55 to 90 °C

In some examples the at least one ultrasonic transducer 6 is arranged to provide acoustic energy to the volume of liquid in the tank 1 at a first depth, and the conditioner 15 comprises at least one heater arranged to provide heat energy to the volume of liquid at a second depth above the first depth. For example, the tank 1 comprises the at least one ultrasonic transducer 6 arranged at a depth in and/or coupled to the tank 1, and wherein the conditioner 15 comprises at least one heater in and/or coupled to the tank 1 to heat the volume of liquid to a selected temperature range. The at least one heater may be arranged in the tank 1 at a depth above that of the at least one ultrasonic transducer 6. The heater and ultrasonic transducer 6 may be arranged so that any bubbles created by the heater do not float past the ultrasonic transducer 6 and thereby do not interfere with the passage of ultrasonic pressure waves from the ultrasonic transducer 6, through the volume of liquid, and to the foodstuff 13.

In some examples, the apparatus may comprise a second tank 1 for holding a volume of liquid as shown in Figure 4. The second tank 1 may comprise a second ultrasonic transducer 6 configured to produce ultrasonic waves through the liquid and into a foodstuff 13 being conveyed through the quantity of liquid in the second tank 1, wherein the conveyor 8 is configured to convey the foodstuff 13 into, through, and out of the volume of liquid in the first tank 1 and then convey the foodstuff 13 into, through, and out of the volume of liquid in the second tank 1.

Another aspect of the disclosure provides a method for disinfecting foodstuffs 13, the method comprising conveying a foodstuff 13 into a volume of liquid in a tank 1, through a volume of liquid in a conveying direction transverse to a depth direction of the tank 1, and out of a volume of liquid in the tank 1; and while the foodstuff 13 is being conveyed through the volume of liquid, exposing the foodstuff to ultrasonic pressure waves.

Tests carried out by the inventor has shown that there is not a single process which satisfactorily disinfects the product rather it has been shown that two synergistic processes working together gives a good disinfection result (4-5 log micro-organism reduction).

The process comprises a Pre-conditioning process and a Disinfection process. Pre-conditioning Process

In a first embodiment and with reference to Fig 1 - A rectangular tank 1 supported by a support structure 2 under its flange 3 via a resilient pad 4 attached to one end of the support structure 2 and the other end of the support structure rigidly attached to a base plate 5. The base of the tank 1 has rigidly attached to its base an ultrasonic transducer 6 which in turn is rigidly attached to the base plate 5. If the tank 1 is filled with a fluid e.g. water up to the water level 7 and the ultrasonic transducer 6 is driven by an ultrasonic oscillator (not shown) then ultrasonic waves are generated from the ultrasonic transducer 6 which vibrate the fluid at the ultrasonic frequency in the range 20 kHz to 100 kHz; preferably the ultrasonic transducer 6 is of the magnetostriction type capable of developing powers greater than 100 Watts. Preferably greater than 200 Watts. A conveyor 8 is positioned such that it travels over the inlet end 9 of the tank 1 and via a plurality of cogs 10 supported by a plurality of shafts in turn supported by a frame cantilevered over the side of the bath 1 (for the purpose of greater clarity not shown) and down inside the tank 1 and then proceeds via the cogs 10 in a serpentine route inside the tank 1 and out at the exit end 11 of the tank 1. Attached to the conveyor 8 are pluralities of baskets 12 which hang below the conveyor 8 and hold the product 13 to be processed.

With the tank 1 filled to the correct water level 7, the baskets 12 filled with the product 13 and the ultrasonic transducer 6 energised then microbiological contaminations on the product 13 are forced off the product due to the ultrasonic vibrations causing a microscopic scrubbing effect on the surface of the product 13. The micro-organisms are forced into the water from the surface as well as any micro-cracks, fissures and pores on the product 13.

Testing has shown that the process as described from in embodiment 1 with chicken breasts contaminated with Campylobacter produces a 1-2 log kill (90% - 99%) and this reduction is curtailed by a serious back contamination problem whereby the microorganisms in the water re-contaminate the product 13 particularly as the product 13 leaves the tank 1. The magnitude of this back contamination is 1-2 logs.

Further testing done with food grade surfactants on chicken breasts have shown that significantly more micro-organisms can be released into the water (1-2 logs more) by using a surfactant to keep the surface tension of the water to a minimum together with its synergistic effect with ultrasonic transducers.

Effective food grade surfactants are Cetypyridinium Chloride (CPC), Biosoft D-40, Alkanomide and Stepanol work well with this process in concentrations up to 50 parts per million.

For good micro-organism kill rates in excess of 3 log kill it is vital that the back contamination problem is solved. To do this requires that whatever means of disinfection is used must not affect the organoleptic qualities and that it kills the micro-organisms quickly to minimize the back contamination.

Disinfection process

It is well documented that UV lamps of the germicidal type emit light at wavelengths in the UVC range (280 nm to 220 nm) and in particular 254 nm. This wavelength is lethal to micro-organisms especially when exposed to it in water.

In a second embodiment and with reference to Fig 2 the apparatus as described in embodiment 1 has an ultraviolet light disinfection process added to it to provide the disinfection stage. Ultra violet light imparts no taste or smell to the product nor does it change the texture or structure of the product but it kills any micro-organisms that get into the water very quickly.

The tank 1 is rectangular with two long sides and two short sides the conveyor 8 enters the tank 1 on one of its short sides 9 and exits out of its other short side 11. A plurality of quartz sleeves 14 are suspended over the one long edge of the tank 1 protruding into the tank 1. Preferably the quartz sleeves 14 are sealed at one end so that they are water tight. The quartz tubes are held in a frame 16 and are positioned vertically along one of the long sides in the tank and supported through a hole 22 in the top of a rectangular, square section frame 16 and are further supported by a corresponding hole 23 in the top of the square section frame 16 and are further positioned by a smaller hole 24 in the bottom of the square section frame 16. The quartz sleeves 14 are rigidly secured to the frame 16 by a resilient seal 17. A second plurality of quartz sleeves 14 and the supporting frame 16 are suspended over the opposite long edge of the tank 1 protruding into the tank 1 to complete the disinfection process. Both frames 16 are suspended into the tank 1 by gantry frame 18 & 19 cantilevered over the top of the tank and secured at their bases to the base plate 5. Supported inside the vertical quartz tubes are UV lamps 15. Preferably the lamps 15 are of the mercury arc type. Preferably the lamps 15 are of the medium pressure type. Preferably the lamps 15 are of the low pressure type. Preferably the lamps 15 are of the low pressure amalgam type. Preferably the lamps 15 are of the pulsed xenon type. Preferably the lamps 15 are an array of solid state LED type.

When the UV lamps are illuminated and the tank 1 is filled with water to its water level 7 and with the product 13 is moving through the tank 1 the whole tank 1 and product 13 is flooded with UV light of a germicidal wavelength and substantially all of the microorganisms in the water or on the surface of the product 12 are either killed or deactivated. Preferably the germicidal wavelength is 254 nm.

By using the ultrasonic vibrations to get the micro-organisms into the water and using the UV disinfection to kill or deactivate the micro-organisms substantial reductions in microbial count can be achieved. Tests carried out on chicken breast contaminated with Campylobacter showed reductions of 3-4 log kills for a 2 minute treatment.

This time was reduced by 50% by the use of a suitable surfactant.

The number of UV lamps and their position in the tank are such that at the end of the lamp life they produce a UV dose at the germicidal wavelength (254 nm) of a minimum of 60mJ/cm2; at the farthest position from the UV lamps in the tank for an exposure time of 10 seconds.

The first 2 embodiments utilize narrow deep tanks but if required a wide shallow tank can be employed such as described below.

In a third embodiment and with reference to Fig 3 the apparatus has a conveyor 8 positioned such that it travels over the inlet end 9 of the tank 1 and via a plurality of cogs 10 supported by a plurality of shafts in turn supported by a frame cantilevered over the side of the bath 1 (for the purpose of greater clarity not shown) down inside the tank 1 and then proceeds via the cogs 10 in a serpentine route inside the tank 1 and out at the exit end 11 of the tank 1. Attached to the conveyor 8 are pluralities of baskets 12 which hang below the conveyor 8 and hold the product 13 to be processed.

With the tank 1 filled to the correct water level 7, the baskets 12 filled with the product 13 and the ultrasonic transducer 6 is energised so that microbiological contaminations on the product 13 are forced off the surface of the product due to the ultrasonic vibrations causing a microscopic scrubbing effect on the surface of the product 13. The microorganisms are forced into the water from the surface as well as any micro-cracks, fissures and pores on the product 13.

To complete the disinfection process a UV disinfection process is added to the ultrasonic tank 1 to provide the disinfection stage.

The shallow tank 1 is rectangular with two long sides and two short sides the conveyor 8 enters the tank 1 on one of its short sides 9 and exits out of its other short side 11. A plurality of quartz sleeves 14 are suspended over the one long edge of the tank 1 protruding into the tank 1. Preferably the quartz sleeves 14 are sealed at one end so that they are water tight. Each quartz tube is held in a vertical frame 16 and are positioned horizontally in-between the serpentine lengths of the conveyor 8 and supported through a hole 22 in one end of a rectangular section frame 16 and are further supported by a corresponding hole 23 in the other end of the rectangular section frame 16. The quartz sleeves 14 are rigidly secured to the frame 16 by a resilient seal 17. The frames 16 are suspended into the tank 1 by gantry frame 18 & 19 cantilevered over the top of the tank and secured at their bases to the base plate (not shown for greater clarity). Supported inside the horizontal quartz tubes are UV lamps 15. Preferably the lamps 15 are of the mercury arc type. Preferably the lamps 15 are of the medium pressure type. Preferably the lamps 15 are of the low pressure type. Preferably the lamps 15 are of the low pressure amalgam type. Preferably the lamps 15 are of the pulsed xenon type.

Preferably the lamps 15 are an array of solid state LED type.

When the UV lamps are illuminated and the tank 1 is filled with water to its water level and with the product 13 is moving through the tank 1 the whole tank 1 and product 13 is flooded with UV light of a germicidal wavelength and substantially all of the microorganisms in the water or on the surface of the product 12 are either killed or deactivated.

The whole process can be speeded up if higher quantities of surfactant can be used but this causes problems with taste. The high levels of surfactant leave a residual on the product which manifests itself as an undesirable taste imparted to the product. A solution to this problem requires positioning the apparatus and process described in embodiment 2 in series with the apparatus and process described in embodiment 1 whereby the ultrasonic and UV disinfector process together with the higher quantities of surfactant remove the micro-biological contamination from the produce and kill or deactivate it and the second ultrasonic tank operating with only ultrasonic vibrations and water removes the excess surfactant.

Such a process and apparatus is shown In a fourth embodiment and with reference to Fig 4 the apparatus and process described in embodiment 2 is placed in series with the apparatus and process described in embodiment 1. The product is disinfected as described in embodiment 2 the baskets 12 containing the product 13 exit this first process (ultrasonic + UV disinfector) at position 11 over the short wall of the first tankl and enter the second tank 1 (ultrasonic + water) over the short wall at position 9. It proceeds through the second tank as described in embodiment 1 to have any traces of residual surfactant removed by the ultrasonic vibrations.

Preferably a water treatment process is added to the tanks to remove oil, fat and general debris from the water to keep it clear. Several products are commercially available for this purpose and those skilled in the art of water treatment will be able to provide suitable schemes.

When using high levels of surfactant it is preferable to use sulfates of alcohols or sulfosuccinates based surfactants as they are low absorbers of the UVC wavelengths as opposed to oil based surfactants which are significant absorbers of the UVC wavelengths. Therefore using the sulfates of alcohols or sulfosuccinates based surfactant allows the UV process to operate at maximum efficiency.

Claims

CLAIMS:

1. An apparatus for disinfecting foodstuffs, comprising: a tank for holding a volume of liquid; a conveyor configured to convey a foodstuff into the volume of liquid, through the volume of liquid in a conveying direction transverse to a depth of the tank, and out of the volume of liquid, to disinfect the foodstuff; and at least one ultrasonic transducer configured to produce ultrasonic waves through the volume of liquid and into a foodstuff being conveyed through the volume of liquid.

2. The apparatus of claim 1 further comprising a flow provider for flowing the volume of liquid in a fluid flow direction opposite to the conveying direction.

3 The apparatus of claim 1 or 2 comprising a conditioner for at least one of: treating the volume of liquid to remove oil, fat and general debris from the volume of liquid; and disinfecting the volume of liquid.

4. The apparatus of claim 3 as dependent on claim 2, wherein the flow provider is configured to pass the volume of liquid through a filter to treat the volume of liquid.

5. The apparatus of claim 3 or 4 wherein the conditioner is configured to provide a surfactant in the volume of liquid to lower the surface tension of the volume of liquid relative to its normal surface tension at standard ambient temperature and pressure.

6. The apparatus of claim 3, 4 or 5 wherein the conditioner is configured to heat the volume of liquid to a selected temperature range.

7. The apparatus of claim 6 wherein the selected temperature range is 55 to 90 °C.

8. The apparatus of claim 6 or 7 wherein the at least one ultrasonic transducer is arranged to provide acoustic energy to the volume of liquid in the tank at a first depth, and wherein the conditioner comprises at least one heater arranged to provide heat energy to the volume of liquid at a second depth above the first depth.

9. The apparatus of claim 8 wherein the heater and ultrasonic transducer are arranged so that any bubbles created by the heater do not float past the ultrasonic transducer.

10. The apparatus of any of the previous claims wherein the tank comprises the at least one ultrasonic transducer arranged at a depth in the tank, and wherein the conveyor is configured to convey the foodstuff through the volume of liquid in the conveying direction at the depth of the at least one ultrasonic transducer.

11. The apparatus of claim 3, or any claim dependent thereon, wherein the conditioner is configured to apply UV radiation of a germicidal wavelength to the volume of liquid.

12. The apparatus of claim 11 wherein the conditioner comprises a tube configured to apply UV radiation to the volume of liquid and arranged parallel to a direction of motion of foodstuff through the tank.

13. The apparatus of claim 11 or 12 wherein the conditioner is configured to apply UV radiation having a wavelength in the range of 220 to 280 nm.

14. The apparatus of claim 11, 12 or 13 wherein the UV radiation has a wavelength of 254 nm.

15. The apparatus of any of claims 2 to 14 wherein the conditioner is configured to be submerged in the volume of liquid.

16. The apparatus of any of the previous claims wherein the conveyor comprises baskets for carrying a selected quantity of foodstuff.

17. The apparatus of any of the previous claims wherein the ultrasonic transducer is configured to provide ultrasonic waves in a frequency range of 20 to 100 kHz.

18. The apparatus of any of the previous claims wherein the ultrasonic transducer is configured to provide at least 10 w/L of acoustic energy to the volume of liquid, for example at least 20 w/L, for example at least 30 w/L.

19. The apparatus of any of the previous claims further comprising a controller configured to operate the ultrasonic transducer and the conveyor, wherein the controller comprises a power electronic control unit configured to provide power to the ultrasonic transducers.

20. The apparatus of any of the previous claims wherein the conveyor is configured to convey the foodstuff in a serpentine pattern through the volume of liquid.

21. The apparatus of any of the previous claims wherein the volume of liquid comprises water.

22. The apparatus of any of the previous claims further comprising a second tank for holding a volume of liquid, and a second ultrasonic transducer configured to produce ultrasonic waves through the liquid and into a foodstuff being conveyed through the quantity of liquid in the second tank, wherein the conveyor is configured to convey the foodstuff into, through, and out of the volume of liquid in the first tank and then convey the foodstuff into, through, and out of the volume of liquid in the second tank.

23. A method for disinfecting foodstuffs, the method comprising: conveying a foodstuff into a volume of liquid in a tank, through a volume of liquid in a conveying direction transverse to a depth direction of the tank, and out of a volume of liquid in the tank; and while the foodstuff is being conveyed through the volume of liquid, exposing the foodstuff to ultrasonic pressure waves.

24. The method of claim 23 further comprising flowing the volume of liquid in a fluid flow direction opposite to the conveying direction.

25. The method of claim 23 or 24 comprising conditioning the volume of to at least one of: treat the volume of liquid to remove oil, fat and general debris from the volume of liquid; and disinfect the volume of liquid.

26. The method of claim 25 comprising passing the volume of liquid through a filter to treat the volume of liquid.

27. The method of claim 25 or 26 wherein conditioning the volume of liquid comprises providing a surfactant in the volume of liquid.

28. The method of claim 25, 26 or 27 wherein conditioning the volume of liquid comprises heating the volume of liquid to a selected temperature range.

29. The method of claim 28 wherein the selected temperature range is 55 to 90 °C.

30. The method of claim 28 or 29 comprising exposing the volume of liquid to ultrasonic pressure waves at a first depth in the tank, and heating the volume of liquid at a second depth in the tank, wherein the first depth is deeper than the second depth.

31. The method of claim 28, 29 or 30 comprising heating the volume of liquid in the tank at a depth so that any bubbles created by the heating do not interfere with the passage of ultrasonic pressure waves to the foodstuff.

32. The method of any of claims 23 to 31 comprising conveying the foodstuff through the tank at a depth at which ultrasonic waves are exposed to the tank.

33. The method of claim 26, or any claim dependent thereon, wherein conditioning the volume of liquid comprises applying UV radiation of a germicidal wavelength to the volume of liquid.

34. The method of claim 33 wherein applying UV radiation of a germicidal wavelength comprises applying UV radiation having a wavelength in the range of 220 to 280 nm.

35. The method of claim 33 or 34 wherein applying UV radiation of a germicidal wavelength comprises applying UV radiation having a wavelength of 254 nm.

36. The method of any of claims 23 to 35 wherein the ultrasonic pressure waves are in a frequency range of 20 to 100 kHz.

37. The method of any of claims 23 to 36 wherein exposing the foodstuff to ultrasonic pressure waves comprises providing ultrasonic pressure waves to the volume of liquid with an energy of at least 10 w/L, for example at least 20 w/L, for example at least 30 w/L.

38. The method of any of claims 23 to 37 wherein the foodstuff is conveyed through the volume of liquid in a serpentine pattern.

39. The method of any of claims 23 to 38 further comprising conveying a foodstuff into, through and out of a second volume of liquid; and while the foodstuff is being conveyed through the second volume of liquid, exposing the foodstuff to ultrasonic pressure waves.

40. An apparatus substantially as described herein, with reference to the drawings.