Photo bioreactor for cold pasteurization of liquid food products and the use of the reactor

Abstract

A system capable of a germicidal treatment of highly opaque liquids, featuring a filter, which prevents wavelengths above the UV-C spectrum reaching the liquid being treated, one or more spiral-shaped tubes extending from an inlet end to an outlet end creating a fluidic pathway, and one or more light sources illuminating the one or more spiral-shaped tubes, wherein the one or more light sources emit light in a wavelength range between 180-300 nm.

Claims

1. A photo bioreactor for pasteurization of liquid food products, the photo bioreactor comprising: a. one or more spiral-shaped tubes extending from an inlet end to an outlet end creating a fluidic pathway; and b. one or more light sources illuminating the one or more spiral-shaped tubes, wherein the one or more light sources emit light in a wavelength range between 180-300 nm and light above a wavelength of 300 nm; wherein the photo bioreactor further comprises one or more filters positioned between the one or more light sources and the one or more spiral-shaped tubes, wherein the one or more filters prevent the light above a wavelength of 300 nm from reaching the one or more spiral-shaped tubes.

2. The photo bioreactor according to claim 1, wherein a fluid movement through the one or more spiral-shaped tubes creates a Dean Vortex flow, laminar flow, or turbulent flow.

3. The photo bioreactor according to claim 1, wherein the one or more spiral-shaped tubes have an inner tube diameter between 1 mm and 10 mm.

4. The photo bioreactor according to claim 1, wherein the one or more spiral-shaped tubes have a pitch between 2 and 8 mm wherein the pitch is the distance from center to center of the one or more spiral-shaped tubes after one turn/coil of the one or more spiral-shaped tubes.

5. The photo bioreactor according to claim 1, wherein the one or more spiral-shaped tubes have a coil angle between 1 and 6°, wherein the coil angle is measured between the one or more spiral-shaped tubes and a straight direction compared to the inlet end to the outlet end creating the fluidic pathway.

6. The photo bioreactor according to claim 1, wherein the one or more spiral-shaped tubes have a coil diameter between 20 and 150 mm, wherein the coil diameter is a distance from outer end to outer end of the one or more spiral-shaped tubes after a half turn/coil of the one or more spiral-shaped tubes.

7. The photo bioreactor according to claim 1, wherein the one or more spiral-shaped tubes are coiled around a pillar.

8. The photo bioreactor according to claim 7, wherein the pillar is made of a reflective material.

9. The photo bioreactor according to claim 1, wherein the one or more spiral-shaped tubes are made of a polymeric or quartz glass material being ultraviolet light transparent.

10. The photo bioreactor according to claim 1, wherein the one or more light sources are coupled to one or more fibers guiding the 180-300 nm light from the one or more light sources to the one or more spiral-shaped tubes.

11. The photo bioreactor according to claim 1, further comprising a reactor housing, wherein the one or more spiral-shaped tubes, the one or more light sources, and the one or more filters are enclosed inside the reactor housing.

12. The photo bioreactor according to claim 1, wherein the photo bioreactor further comprises a cooler that air cools the one or more light sources.

13. The photo bioreactor according to claim 1, wherein the photo bioreactor further comprises a control unit and the control unit comprises electronic temperature control and flow control.

14. The photo bioreactor according to claim 1, wherein the photo bioreactor further comprises a control unit and the control unit automatically controls a lamp temperature and a flow speed of a liquid through the fluidic pathway.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an explosion view of an embodiment of the present invention, showing a reactor housing, spiral-shaped tubes comprising an inlet and an outlet, a pillar, and a filter.

(2) FIG. 2 shows a side view of an embodiment of the present invention, showing two reactor housings, two outlets, two filters, and multiple light sources.

(3) FIG. 3 shows a side view of an embodiment of the present invention, showing two reactor housings, two outlets, two filters, and multiple light sources.

(4) FIG. 4 shows a see-through side view of an embodiment of the present invention, showing two reactor housings (parts of reactor housing are see-through), two outlets, two filters (filters are see-through), and multiple light sources.

(5) FIG. 5 shows a see-through front view of an embodiment of the present invention, showing a reactor housing, a spiral-shaped tube comprising an inlet and an outlet, a pillar, and a filter.

(6) FIG. 6 shows a cut-through side view of an embodiment of the present invention, showing a reactor housing, a spiral-shaped tube comprising an inlet and an outlet (not shown), a pillar, and a filter. The cut is made down the middle of the reactor housing.

(7) FIG. 7 shows a schematic illustration of different parts and measurements of specific embodiments of the present invention.

(8) FIG. 8 shows an investigation of the amount of energy required from the light source to obtain inactivation or reduction of the biological contaminant.

(9) FIG. 9 shows an investigation of the difference in the current invention when varying the temperature from 18 degrees centigrade to 38 degrees centigrade.

(10) FIG. 10 shows an investigation of the current invention when varying the flow rate of the liquid at three different tube sizes.

(11) FIG. 11 shows a degree of damages caused by radiation in virus versus protein at different wavelengths (220-320 nm).

DETAILED DESCRIPTION OF THE EMBODIMENTS

(12) The FIGS. 1, 5, and 6 shows different views of an embodiment of a photo bioreactor for cold pasteurization of liquid food products. The photo bioreactor comprises a spiral-shaped tube 104 extending from an inlet end 106 to an outlet end 108 creating a fluidic pathway. The spiral-shaped tube 104 is coiled around a pillar 110.

(13) The photo bioreactor further comprises a reactor housing 102a, 102b, 102c, which comprises three parts; a first part 102a positioned on the top of the photo bioreactor in FIG. 1, a second part constituting the side of the housing, and a third part positioned at the lower side of the photo bioreactor.

(14) A filter 112 positioned between outside the spiral-shaped tube 104 is also shown in FIG. 1. The filter 112 prevents light above a wavelength of 300 nm from reaching the spiral-shaped tube 104.

(15) The filter 112 is shown as see-through filter in FIG. 5. In FIG. 6, the shown cut is made down the middle of the reactor housing 102a, 102b, and 102c.

(16) The photo bioreactor shown in FIGS. 1, 5 and 6 are examples of photo bioreactors where the liquid food product flows overall vertically through the one or more spiral-shaped tube 104 when observing from inlet end 106 to outlet end 108.

(17) The FIGS. 2-4 shows an alternative embodiment of the photo bioreactor for cold pasteurization of liquid food products comprising similar elements as identified and discussed in connection with FIGS. 1, 5 and 6.

(18) In the embodiment in FIGS. 2-4, multiple light sources 114 is utilized for illuminating two spiral-shaped tubes 104. The light sources 114 emit light in a wavelength range between 180-300 nm. In FIGS. 2-4, two filters 112 positioned between the light sources 114 and the two spiral-shaped tubes 104 included in the photo bioreactor.

(19) The two filters 112 are shown as see-through filters in FIG. 4. Additionally, two spiral-shaped tubes 104 comprising inlets 106 and outlets 108, and the pillars 110 are visible inside the reactor housing 102a, 102b, and 102c in FIG. 4.

(20) The photo bioreactor shown in FIGS. 2-4 are examples of photo bioreactors where the liquid food product flows overall horizontally through the one or more spiral-shaped tube 104 when observing from inlet end 106 to outlet end 108.

(21) FIG. 7 shows spiral-shaped tubes 104 with inlet 106 and outlet 108 according to the invention. The compressed length of the spiral-shaped tube 116, the extension/free length of the spiral-shaped tubes 118, the inner tube diameter 120, the pitch 122, the coil angle 124, the coil diameter 126, the outer tube diameter 128, and the wall thickness 130 are all illustrated in FIG. 7.

(22) FIG. 8 shows the investigation of the amount of energy required from the light source to obtain inactivation or reduction of the biological contaminant.

(23) FIG. 9 shows the investigation of the difference in the current invention when varying the temperature from 18 degrees centigrade to 38 degrees centigrade.

(24) FIG. 10 shows the investigation of the current invention when varying the flow rate of the liquid at three different tube sizes.

(25) FIG. 11 shows the degree of damages caused by radiation in virus versus protein at different wavelengths (220-320 nm).

EXAMPLES

(26) General Experimental Procedure

(27) The effects of tube diameter and flow rate were investigated using UHT whole milk spiked with Escherichia coli to a concentration of minimum 2.7E6 per millilitre (determined using the most probable number method).

(28) One litre UHT whole milk were transferred to a sterilized blue cap flask and added 1 ml of Escherichia coli media, achieving a desired minimum concentration of at least 2.7E6/ml. The spiked milk was circulated in the UV-reactor and samples were taken at intervals, when desired UV-C doses were achieved. The spiked milk was mixed constantly throughout the experiment using a magnetic stirrer.

(29) For each specific flowrate and tube size a new batch of 1 litre UHT whole milk spiked with Escherichia coli to a minimum concentration of 2.7E6/ml was prepared.

(30) The UV-reactor consisted of a FEP tube coiled around a 28 mm quartz glass. Within the quartz glass a 75 W germicidal lamp with a peak radiation at 253.7 nm was placed. The tested tube sizes were AWG (American wire gauge) 7, 9, and 11 and the flowrates investigated were 200, 300, 600 and 1000 ml per minute.

(31) The milk was circulated using a rotary vane pump and exposed in the UV-reactor for a period of time before samples of 20 ml were taken using sterilized pipettes and transferred to a sterilized blue cap flask. The milk was circulated in the system, with the lamp off prior to each experiment and a sample was taken to establish the start concentration. The milk temperature was 24 to 25° C. at the start of each experiment and 34 to 43° C. at the end of each experiment.

(32) After each experiment, the system went through a CIP (clean-in-place) procedure, first flushing the system using demineralised water for 10 minutes, followed by 40 minutes of circulating a 1% NaOH solution at 65° C. Followed by flushing the system for 10 minutes using demineralised water. After which a 0.5% HNO.sub.3 solution at 60° C. were circulated in the system for 40 minutes. Finally, the system was rinsed for 20 minutes using demineralised water.

(33) The samples were transferred to a sampling station in a laminar biosafety cabinet immediately after the experiment ended, where they were treated using the MPN method following Jarvis et al. [Jarvis, B. et al., Journal of Applied Microbiology, 2010, 109, 1660-1667].

(34) After two days in an incubator at 35° C. the number of positive test tubes was counted and the bacteria concentrations calculated.

Example 1

(35) Experimental example 1 investigates the amount of energy required from a pump and the light source to obtain inactivation or reduction of the biological contaminant. The tested tube size is AWG 9 and the flowrate investigated is 700 ml per minute.

(36) As can be seen in FIG. 8, by using a small amount of light energy (around 1.2 kWh per 1,000 liter liquid) a 1-Log.sub.10 reduction is obtained. When increasing the light energy used the Logo reduction is also increasing until a plateau is obtained from 10 kWh per 1,000 liter liquid with a reduction of around 5-Log.sub.10.

Example 2

(37) Experimental example 2 investigates the difference in the current invention when varying the temperature from 18 degrees centigrade to 38 degrees centigrade. The tested tube size is AWG 9 and the flowrate investigated is 700 ml per minute. As shown in FIG. 9, the difference in log.sub.10 reduction is similar around 10 kWh per 1,000 liter liquid. However, when the energy used is increased, the log.sub.10 reduction between 18 degrees centigrade and 38 degrees centigrade start to be significant. At energies of around 18 kWh per 1,000 liter liquid the log.sub.10 reduction is 5.5 for 38 degrees centigrade, while it is 6.5 for 18 degrees centigrade, which corresponds to 1-log.sub.10 reduction in difference.

Example 3

(38) Experimental example 3 investigates the current invention when varying the flow rate of the liquid at three different tube sizes. The tested tube sizes were AWG 7, 9, and 11 and the flowrates investigated were 200, 300, 600 and 1000 ml per minute.

(39) The temperature is kept between 24 and 43 degrees centigrade. As can be observed in FIG. 10, depending on the tube size, the setup is optimal at different flowrates.

(40) Using a tube size of AWG 7 there is a small difference between flowrates. However, this difference is most predominant when analyzing at high energy exposure (around 4,000 J per liter liquid) where a 1-log.sub.10 difference is observed between flowrates of 200-300 ml/min versus flowrates of 600-1,000 ml/min.

(41) Using a tube size of AWG 9 there is a large difference between flowrates. This difference is largest when analyzing at high energy exposure (around 4,500 J per liter liquid) where a 3-log.sub.10 difference is observed between flowrates of 200-300 ml/min versus flowrates of 600-1,000 ml/min.

(42) Using a tube size of AWG 11 there is a very small difference between flowrates. However, this difference is negligible when analyzing at high energy exposure (around 4,000 J per liter liquid).

REFERENCES

(43) 102a First part of reactor housing 102b Second part of reactor housing 102c Third part of reactor housing 104 Spiral-shaped tubes 106 Inlet 108 Outlet 110 Pillar 112 Filter 114 Light source 116 Compressed length 118 extension/free length 120 Inner tube diameter 122 Pitch 124 Coil angle 126 Coil diameter 128 Outer tube diameter 130 Wall thickness