CA1159705A

CA1159705A - Apparatus for sterilizing flowable food products by electro-magnetic radiations

Info

Publication number: CA1159705A
Application number: CA000402994A
Authority: CA
Inventors: Rene A. Marinoza
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-14
Filing date: 1982-05-14
Publication date: 1984-01-03

Abstract

ABSTRACT OF THE DISCLOSURE

There are disclosed a process and an apparatus for pasteurizing and/or sterilizing food products by exposing the latter to electro-magnetic radiations, namely: infra-red radiation for pasteurization and ultra-violet radiations for sterilization. The apparatus enables continuous treatment of the food products.

Description

1 1597i)5 The present invention relates to the treatment of flowable food product~ fnr at lea~t partially sterili~ing o~ the same.

Conventionalpagteurizin9 method uses plate h~at exchangers, where the transmission of heat is carried out through a surface that is haatsd to a temp~rature far abov~ the temperature required to obtain the proper heat treatmènt. Oeside being snergetically very inHfficient, this method is cauaing many problems to the user3, such as off-flavour, browning, cooked flavour snd burnt deposits on the heating surfaces. ~van though pastsurization is considered a~ the most efficient means to control bacteria con-tamination, heat-resisting bacturia are not destray~d by the pasteurizing temperatures and proce~sing times practical for this type of method. Ir sterilization is required for long-time conservation, one must add chemical preservatives.
û~JECTS OF THE IN~ENTION
It is the general obJect Or the present lnvention to provide a process and spparatus for at lesst partially sterilizing ~lowable food products, which obviate the above-noted disadvantages in that heat is ~nstantaneously transmitted through the mass of the rood product to thereby eliminate ofr-flavour, browning, caramelization, cooked flavour and burnt dèposits on the heatlng surface of the con~entional heat-treating system.
It I9 another object of the present invention to provide a heat-treating procegs which is applicable to various flowable rood products and, more particularly, milk and cream.
It is another object Or the invention to provide an apparatus for hot-treating rood products, which is compact, requires about 40%
less energy than the conventional pasteurization apparatus; does not require a boiler~ 8team and condensate piping and other appliances, such as de-aerators, steam valves, piping insulation; and which does not require maintenance, such as sdjusting and retrotitting Or oil burners and re-tubing Or the boiler~
.

- 2 -1 15~7~)5 Another object of the in~ention is to provide an apparatus of th~ character described~ which is of simple and inexpensive construction and operation, and which can treat ~ood producta in a continuous flow.
SU~ARY OF ~HE INVENTION
The process in accordance with the invention consists of continuously flowing a flowable food product as a relatively thin layer, while exposed to a source of electro-magnetic radiation~. For pastsurizing th~ food productg,the source of electro-magnetic radiations ig An infra-red gource~ while for ~terilizing the product, ultra-violet radiations are used.
The apparatus in accordance with the invention comprises a treatment cell, o~ tubular shape, including an elongated radiation-emitting element spacedly surrounded by a tuJular ~acket completely traneparent to the electro-magnetic radiations and in turn spacedly surrounded by an outer tube,~orming with the ~acket, an annular passage for the flow of the food products to be treated.
In accordance with ths pre~nt invention, the apparatue further comprises a holding chamber to complete pasteurization and heat exchangers to pre-heat the food products and to recuperate the heat thsre~rom a~ter treatment.
The foregoing will become more apparent during the following discloeure and by referring to the drewings, in whichs BRIEF DESCRIPTION OF THE DRAWINGS
_ Figure 1 i~ an elevation of a typical apparatus in ac-cordance with the invention;
Figure 2 i~ a longitudinal section of an infra-red heating cell;
Figure 3 is a longitudinal section of a holding chamber;
figure 4 is a longitudinal ssction of an ultra-violet sterilizing cell;

figure 5 i8 a cross-section of a multi-tube ultra-violet sterllizing call;
Figure 6 is a longitudinal section of a heat-exchanger

- 3 -1 15g7V5 module;
figure 7 is a flow diagram of a pesteurizing-sterili2ing unlt;
Figure O i8 8 flow diagram of a pasteurizing unit;
Figure 9 i8 a flow diagram of a pasteurizing-sterllizing unit fittod with pre-cooling or pre-heating and cooling system; and Figure 10 i9 a tlow diagram of a pasteuri2ing unit fitted with a pre-heat~ng section.
DTAIL~D ~ESCRIPTION OF THE INVENTION
Figure 1 showa an apparatus for pasteurizing and sterill2ing a food product, such a8 milk. The tlow diagram of the apparatus shown ln Figure 1 i~ illustrated in Figure 7. The epparatu~ comprl~e~
one or more infra-red heeting cell~ 1, a holding chember 2~ heat exchen-gers 3 and 3', an ultre-violet sterilizing cell 4, a control module 5, a uolumetric pump 6 wlth its electric motor, a turbine ~low meter 7,a receiving tank 8 and eulteble piplng with three-way valves 89 end 89~.
~he untreated food product enters st 88 and exits at 86.
In normal operatlon, the tood product is circulated through pump 6 through one pass o~ heat exchanger 3' and 3, through the infra-red heating cell 1, through the holding tank 2, through the other pass o~ the ~û heat exchanger 3, through the ultra-violst sterilizlng cell 4, through the other pass o~ the heat exchanger 3' and, rinally, to be dischsrged et B6 where it may be further cooled down by the coollng unit 87.
To etart the paeteurizing and sterilizing operetlon~ the ~ood product i8 circulated for a few minutes in a closed loop through the ~yStem until the product~has been heated sufriciently by the infra-red hHating cell 1. for thi~ purpose, once the system is filled wlth a product, the three-way values 89 are operated 80 that the product will recircul~te through the receiving tank 8 and back through the pump 6.
A8 shown in Flgure 7, a cooling unit 87 may be added to the outlet 86 if the liqùid is not eutficiently oooled.
A three-w~y valve 89~, wlth a discharge to a draln, may be added at th~ oytlet of th~ holding chamber 2 to dra~n th$s part Or

- 4 --I 15g7~
the 5y~ t~m.
One of the infr~,-rnd cell~ i9 BhOWn in Figure 2. It comprl~es an nlongated infre-rod emitting element 11 spacedly surroùnded by a tubular jacket 17~ made of quartz or other material, whlch i8 com-plettlly tran~parent to infra-red radiations. The jacket 12 is ln turn spacedly surrounded by an outer tube 13, m~de of metal, the interior surface of which i9 polished, ~o e~ to be reflect~ue to the radiations.
Two similar end cell bodies 14 hold the above-descrlbed assembly. One end cell body defines inlet chamber 15 in communlc~tlon wlth an inlet port ?2 and with the annular space 27~while the ether end cell body l~ define8 a oimllar outlet chamb~r 24 with an outlet port 25 and in communication with the annular space 27~ End cell bodies 14 hold the ~nfra-red element 11 by means of holding plates 17 and a support element 26. The in~ra-red element 11 ~8 connected to an electrical power source by electrical socket 19 and electrical wlre 21. The socket 19 i~ enclosed ln 8 chamber rormed by one end cell body 14 and closed by a screwed cap 16. The cap carries a screwlng head 20 for the passage of electrlcal wire 21. The~jecket 12 is ~ealed to both nd cell bod~es 14 by means of a gasket 16 held ln place by a threaded compres~ion disc 23.
The llquid or s~ml-liquid tood product to be treated lows through the annular gpsce 27 eg a relatlvely thin layer, while bein4 irradiated by the lntra-red element 11. The tood product i~ heated to the required pasteurization temperature without being exposed to heated sur~ace, slnce the ~acket 12~ being made Or quartz, doe~ not become hot.
Flgure 3 is a longitudinal ~e¢tion of the holdlng chamber 2 which cha~ber consists ot an inner shell 31 spacedly surrounded by an outer shell 32 with the interpo~itlon~of lnsulating materlal 34.
The ends of the two shells are fitted on end shell rings 33, which support an end caslng 35. One end casing has an outlet port 36, while the end casing has an inlet port 37. The outer shell 32 i9 - preferably pro~lded with expansion rlbs 35. The inside diameter ot

- 5 -' .
," , - - - , ~ 15~7~)5 inn~?r sl~flll is of larger cross-sectional area than the cross-cectional area of the annular space 27 of the infra-red cell 1~ 80 that the food product will ~low down ln the holding chamber 2 for suFficient time to allow complstion of pasteurizatlon, thu food product being then at the pa~teuri-~ing temperature as obtained by exposure in the infra-red cell.
Fl~ure 4 illustrates the ultra-violet cull 4. This cell includes an ultra-violet radlation-emitting tube 41 spacedly aurroùnded by a quartz tubing, nr ~acket 4~, completely tranaparent to ultra-violet radiations. The ~acket 42 ig in turn gurrounded by an outer tube43, which deflnee with the jacket 42 an annular space 46. The jacket 42 and tube 43, together with the ultra-violet tube 41, are held in end cell bodies 44, of similar con~truction and of a construction similar to the end cell bodies 14 of the infra-red cell 1. Ons end cell body 44 defines inlet chamber 45 provided with an inlet port 54, while the other body 44 derines outlst chamber 55 and outlet port 5S.
One end of the ultra-vlolet tube 41 is supported by a tube socket 51 and socket bearing plate 47. The tube is connected to electrlcal w$re 50 ~ which extends through a screwing head 49 attached to the screwed ca~ 4~. The other end of the ultra-violet tube 41 is supported by a tube support ~ and a tube socket 58 sscursd to the socket bearing plate ~?. The quartz ~acket 4~ is sealed to the respective end cell body 44 by msans o~ a watertight gasket 53 held ln place by a threaded compression disc 52. Here again, the food to be treated whlch enters inlet port 54 into inlet chamber 45 will flow as a relatively thln layer through the annular space 46 to exit at 55. Since the quert2 Jacket 42 i8 completely transparent to the ultra-violet variations~ lt will not heat up and sterilization will be effscted wlthout substan-tially increasing the temperature o~ the ~ood product. Sterilizatlon is snhanced since the outer tube 43, which is mads Or metal, has an interior polish to reflect the ultra-violut radiations.

For increas~d capacity, the ultra-violet cell can take the form shown in figure S, wherein 8 multi-tube cell is shown in cross-section.

I 15~705 Each ultra-violet tube 41 is partly ~urrounded by a tr~n~versely-curved reflector 62, fDr ingtanco mede of polished aluminum. The reflectors 62 are joine~ two by two by a non-~cratch edge protector 63 engaging the insidR surfac~ of the quartz 3acket 64, which i8 in turn gpacedly surrounded by the outer tube 66, again made of metal with an interior surface polish. Obviously, the ~umber of tubeg and agsociated reflectors may vary to meet treatment requirements.
Figure 6 shows ~ typlcal heat exchanger 3 which comprises an inner met~l tube 71 surrounded by an outer metal tube 72 defining an annular space therebetween. The two tubes 71 and 72 are gupported at their endg by two similar end cell bodies 73. One body 73 defines an inlet chamber 74 with its inlet port 75, while the other body 73 defines an outlet chamber 78 with its outlet port 79. The inner tube 71 is held in ~ealing engagement with the cell bodiss 75 by means of watertight gaskets 76 held in place by screwed compression ring 77. The inner tube 71 protrudes ~rom the end cell bodie8 73 and is provided at its two end~ with a coupling 80 for coupling to the piping of the apparatus.
One path of the ~ood product i- through the inner tube 71, while the other path is through the snnular space between the inner and outer tubea 71 and 72.
In the arrangement of Figure 1, there are four series-connected heat-exchange~ modules ~ corresponding to each of the exchanger 3 and 3~
of Figure 7. There are two series-connected infra-red heating cells 1 and two series-connected ultra-vlolet sterilizing cells 4. There is one holding chamber 2.
The control center S serves to control the op~ration of the three-way valves 89~ the pump 6 at the required rate of flow qs measured by the flow meter 7. Also, temperature sensors are provided and a warning light is in~talled to indicste whether or not the sterilizer cells 4 are 3D in operation.
Infra-red radiations wlll heat rapidly the food product throughout its mass without overheating the tube walls in contact with the flowable food product.

-~ - 7 -~ ~ .

1 1S97~)5 Ultra-violet radiation~ are u~ed to destroy the thermo-phyl1ic and thi~rllloduric bacteria that ~uruiue paeteurization, and this makas up most of tha residual bacterie count legally permitted in pasteurlzed product~.
In the treatment cells, unabsorbed infra-red or ultre-violet energy wlll strike tl-e hlghly-polished enclosures and will be mostly reflected back into the mass of the f.ood product to be e~entually absorb~d by the Rame.
~he low temperat~re sterilization assures ths destructian of 9pores reproducing bacter$a~ while a~oiding the cooked taste caùsed by high t~mperature treatment.
The holding chamber 2 down~tream from the infra-red heating cells 1 .~erve-~ to hold the product at the pasteuriz$ng temperature for sufficient time to complete.the paeteurization process.
When eterilizlng a chemically-unstable liquid, the time exposurs of the liquid to the ultra-violet raye must be carefully controlled, in order to prevent photo-chemical reactlonH whlch may have an adverse ~ffect on flavour.
Preferably, operation of the infra-red emittlr~g tubes i8 controlled by an electronic modulator located in the control center 5.
Rsterring to ~igure 7, after lea~ing the holding tank 2~ the food product to he treated le rlrst cooled down in the hsat-exchanger section 3 to the beet suitable tempereture for ~terilization in tha ultra-violet cells. Thereafter, the treeted flowablè.food product i8 ~urther cooled down in the escond heat-exchanger etage 3. It i8 then discharged in cooled condition at 86, or further cooled in a cooling unit 87.
The hold1ng chamber 2 is meinly requlred for mllk, creem, oyrup~
fruit Juice, alcohol. Some other producte, like wine~, do not need such 3~ a holding chamber.
Sterilizatlon mey not be required every time; therefore~ tne ultra-violet gensrating tubes 41 may be ds-energized from the control center 5. A ~lashi~g warning signal will $nform the operator that A

1 15g7~5 the sterilization i9 in operation. Sterili~ation by ths ultr~-violet cell8 i8 applicabla to alcohol, beer, brandy~ cider, coffee extract~
cooking oil, egg mixture, egg white, fruit juice, honey, herring brine, molasse~, mu~t, peptic juice, syrup~ tomato ketchup~ vinegar, water, wine, whisky, yolk and similar products.
The apparatuQ can handle liquid, semi-liquid or even pulpous products. It is applicable to the partial aging of wines, brandy, whisky, etc. No change of col`or or taste ha~ been found when treating ~ruit and vegetable ~uice.
The apparatus is compact, ag all the procesging equipment is assembled as a monoblock unit. It is energetically efficient~
since the whole operation requires ~0~ less energy than pasteurization effected with conventional systems. The entire apparatu~ may be mounted on caeters, 90 that ths unit may be tranaported to different areae o~ the same plant.
If only sterillzation is required, then the infra-red heating cells 1 may be simply cut off.
Figure 8 shows a flow diagram of a pasteurizing unit without the sterilizlng functlon~ Otherwise, this unit is the same as in Figure 7.
Figure 9 is a ~low diagram of a pasteuri2ing and sterilizing unit fitted with a pre-cooling or pre-heating section and a cooling section. It is similar to the flow diagra- of Figure 7, wlth the addition of a pre-cooling and/or heating section 91 fed by cooling of heating liquid circulated by pump 90. There ie another coollng section, indicsted at 92.
Figure 10 represents a flow diagram of a pastsurizing unit fitted with a pre-heating section. This i8 similar to the flow diagram o~ Figure ~ with the addition of a pre-heating exchange section 93 fed with hot water from a hot water tank 94 and hot water circu}ating pump 95. This ~ection 93 can be bypassed by operation of the three-way val~e 89.

_ g _

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED, ARE DEFINED AS FOLLOWS:

1. An apparatus for at least partially sterilizing flowable food products, comprising an elongated cell including an electro-magnetic radiation-emitting elongated member, bodies supporting the ends of said member, a first quartz tube spacedly surrounding said member and supported by said end bodies, said first quartz tube being transparent to electro-magnetic radiation, a second tube spacedly sur-rounding said first tube and defining a circulation space with said first tube, said first and second tubes being supported by said bodies in fluid-tight engagement therewith, said bodies each defining a chamber in communication with said space and for communication with tubing for circulating a flowable food product through said space.

2. An apparatus as claimed in claim 1, wherein said second tube is opaque and is reflective of said electro-magnetic radiations.

3. An apparatus as claimed in claim 2, wherein said member constitutes a source of infra-red radiations.

4. An apparatus as claimed in claim 2, wherein said member constitutes a source of ultra-violet radiations.

5. An apparatus as claimed in claim 4, further including a holding chamber connected to the outlet of said cell, said holding chamber being a heat-insulated tube assembly having an internal free cross-sectional area larger than the cross-sectional area of the circulation space of said cell.

6. An apparatus for at least partially sterilizing a flowable food product, such as milk, comprising an infra-red heating cell, a holding chamber and an ultra-violet sterilizing cell serially connected in the named order, each cell comprising a central, elongated radiation-emitting element, a first quartz tube spacedly surrounding said element and transparent to radiations emitted by said element, a second tube spacedly surrounding said first wuartz tube and reflect-ive of said radiations, said second tube defining a circulation space with said first tube, and bodies supporting the ends of said tubes and of said element in fluid-tight assembly, each body defining a chamber surrounding said first quartz tube and a port for communication with said chamber, the latter in communication with a circulation space between said first and second tubes, said holding chamber defining an elongated tubular member having heat-insulated walls and having a free circulation space, the cross-sectional area of which is larger than the circulation space of said cells and tubing connecting said cells and holding chamber.

7. An apparatus as claimed in claim 6, further including a first heat exchanger having a first path connected between said holding chamber and the outlet of said ultra-violet sterilizing cell, and a second path connected to the inlet of said infra-red heating cell for pre-heating the flowable product entering said last-named cell, and a second heat exchanger having a first path receiving the flowable product coming out of said ultra-violet sterilizing cell and a second path for circulating the untreated product prior to entering said first heat exchanger.