NZ307127A

NZ307127A - Pasteurising or sterilising herbs and other materials comprises cooling and, at a pressure greater than 1 bar, rapidly heating and recooling

Info

Publication number: NZ307127A
Application number: NZ307127A
Authority: NZ
Inventors: Andrew Stirling Inglis; David James Lark
Original assignee: Boc Gases Australia Ltd
Priority date: 1995-05-18
Filing date: 1996-05-20
Publication date: 1999-09-29
Also published as: CN1184406A; WO1996036237A1; KR19990014912A; ZA964002B; AUPN305695A0; CA2215733A1

Description

New Zealand No 307127 International No PCT/AU96/00305 TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates 18 05 1995, Complete Specification Filed 20 05 1996 Classification (6) A23L1/221.226, A23L3/00,36, A23C3/02.04, A61L2/06 Publication date 29 September 1999 Journal No 1444 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention Method and apparatus for pasteurisation of sterilisiation of herbs and spices Name, address and nationality of applicant(s) as in international application form BOC GASES AUSTRALIA LIMITED, an Australian company of The BOC Gases Building, 799 Pacific Highway, Chatswood, New South Wales 2057, Australia 4m, WO 9<>/3<>237 1 PCTM.U96/00305 METHOD AND APPARATUS FOR PASTEURISATION OR STERILISATION OF HERBS AND SPICES This invention relates to a method and apparatus for pasteurising or 5 sterilising herbs, spices and other materials prone to microbial spoilage Attempts have been made to develop methods for pasteurising or sterilising herbs aiid spices involving heat treatment However, these methods have been found to be impracticable as the heal treatment step results in the mobilisation and/or destruction of the volatile substances 10 which give the herbs and spices their functionality and appeal Traditionally, therefore, herbs and spices have been treated by exposure to ethylene oxide Unfortunately, such ethylene oxide processes have certain disadvantages For example, it has been found that while such processing 15 can result in a reduction in the bacterial numbers in the product, they have the disadvantages that bacterial and fungal spores commonly have a natural resistance to this sterilant so its effect is concentiation dependant and long exposuie times are required for penetration Further, the exposure to ethylene oxide of foods with high salt concentrations has been reported to 2 0 produce reaction products such as epichlorhydrin. which are potentially toxogenic Thus it is one object of the present invention to provide a method and apparatus for effectively pasteurising or sterilising herbs, spices and other materials prone to microbial spoilage, which has little or no adverse 2 5 effect on their functionality Accordingly in a first aspect the present invention provides a method for pasteurising or sterilising heibs, spices and other materials prone to microbial spoilage comprising the steps of (1) cooling said herbs, spices or other materials to a temperature 3 0 less than about OnC, wo 96/36237 PCT/ATJ96/00305 w (2) rapidly heating said cooled herbs, spices or other materials to a pasteurising or sterilising tempeiature, and (3) recooling said herbs, spices or other materials to about room temperatuie, wherein at least steps (2) and (3) are performed in an enviioninent(s) having a pressure of greater than 1 Bar Performing steps [2] and (3) under pressures greater than 1 Bar prevents loss of volatiles from the materials being treated In addition, use of such pressure in these steps is believed to positively contribute to colour 10 fastness and the reduction of microbe numbers Preferably, the piessures applied in steps (2) and (3) are greater than 3 Bar Once step (3) is concluded, the environment within which the materials are contained may be returned to atmospheric pressure Step (1) is prefeiably a rapid cooling step and may be completed in 15 0 05 to 5 0 minutes more preferably 0 5 to 3,0 minutes During step (1) the herbs, spices or other materials are preferably cooled to a temperature less than about -70°C. moie preferably, to a temperature of about -170°C It is also preferred that step (1) be performed in an environment(s) having a piessuie greater than 1 Bar 20 The rapid heating step (2) may be achieved by the application of heat from anv source radiative, conductive or convective, which may be generated by combustion by induction or dielectnc heating with electromagnetic radiation nuciowave, by infra red irradiation, or any othei means The heat is preferably applied for 0 05 to 5 0 minutes, more 25 preferably 0 1 to 3 0 minutes or longer dependent oil the material and its microbial bioburden The recooling step (3) is also pieferably a rapid cooling step and may be completed in 0 05 to 5 0 minutes, more pieferably 0 1 to 2 0 minutes In a second aspect the present invention piovides apparatus for 30 conducting the method of the first aspect of the invention PCT/AU95/f><)305 The method may be performed on batches of materials or continuously Thus, an apparatus according to the invention for batch treatments may comprise, a vessel compnsing, an inlet means through which a batch of herbs, spices or other materials susceptible to microbial spoilage may be introduced, means for cooling said batch to a temperature less than about 0°C, means for rapidly heating said cooled batch to a pasteurising or sterilising temperature, means for recooling said batch to about room temperature, means for applying and/or regulating a pressure within the vessel during heating and recooling of gieater than 1 Bar, and outlet means for removing the treated batch from said vessel Preferably, the apparatus for batch treatments comprises a pressure 15 vessel constructed to sanitary standards which feeds out through a valve to an aseptic filer sourced commercially A batch of matenal for treatment is introduced through an infeed hopper equipped with a valve into the vessel were stirring is instigated by a motonsed stirrei The product is rapidly cooled to less than 0°C by the cooling effects of expanding coolant sparged 20 through the matenal being treated, which may be liquefied nitrogen, liquefied carbon dioxide or a mixture of both, or other gas, either in combination or alone and may be humidified prior to application Immediately the desired cooling step temperature (e g temperature of between -70°C and -170°C) and pressure (e g pressure greater than 1 Bar) is 25 reached a pressure regulating valve is closed, the inflow of coolant reduced and then controlled to maintain a pressure of gieatei than 1 Bar, more preferably greater than 3 Bar While this pressure is maintained, the matenal is exposed to heating for a treatment duration sufficient to reduce the total microbial content by the desired factor, dependant on the bacterial 30 and fungal bioburden of the infeed material #W0 96/36237 4 The applied heat source is preferably arranged on the vessel so as to optimise the application and penetration of the heat, thus minimising the treatment time needed and the resultant pioduct damage Fast response sensitive pressure and temperature sensors may be provided to monitor 5 progression of the treatment and the outputs from these are feed to a control circuit which in turn regulates the application of heat and pressure The control circuit typically includes a programmable logic controller and a supervising, control and data acquisition computer An apparatus according to the invention for continuous treatments 10 may comprise a first vessel comprising an inlet means through which herbs, spices or other materials susceptible to microbial spoilage may be conbnuoxisly introduced, and means for cooling said herbs spices or other materials to a temperature less than about 0°C, a second vessel comprising, means for rapidly heating said cooled herbs, spices or other materials, and means for applying and/or regulating a pressure of greater than 1 Bar, and a third vessel compusing means for recooling the herbs, spices or other materials to about room temperature, means foi applying and/or 2 0 regulating a pressure of greater than 1 Bar, and outlet means for removing the tieated herbs, spices or other materials from said vessel, wherein said first vessel is connected to said second vessel and said second vessel is connected to said third vessel, the arrangement being such that the heibs, spices or othei materials introduced into the first vessel may be 25 continuously and progiessively transfened to the second and then third vessels The material treated by this invention may be in addition to herbs and spices, for which it was specifically developed, other foods, pharmaceuticals, leaf matenal in various forms for example tobacco oi various free flowing powdered materials which are prone to microbial spoilage The invention will now be further descubed by way of the following, non-limiting examples and accompanying figuies Brief Description of Accompanying Figures Figure 1 piovides a schematic elevational representation of a preferred apparatus according to the invention for batch treatments of herbs and spices Figure 2 provides a schematic elevational representation of a preferred apparatus according to the invention for continuous flow treatments of herbs and spices EXAMPLE 1 Batch Apparatus 15 As shown in Figure 1, the sanitary designed piessure vessel (1) has a tapered conical base, is equipped with a motonsed stirrer (2), infeed liopper/valve (3) and outfeed hopper/valve (4) A safety vent (7) is also piovided A preweighed batch of matenal to be treated is introduced through 2 0 infeed hopper/valve (3) and stirring commenced with stirrer (2) Coolant is introduced through sparging ports (10) and allowed to escape through a pressure legulator valve (6) until the desired cooling step temperature is recorded by the thermocouple (9) in contact with the matenal being treated In the next stage, coolant gas flow is reduced and the pressure 25 regulating valve (6) is servo driven to maintain the desired pressure (greater than 3 Bar), sensed by a pressure transducer (8) Heating is then commenced, applied from heaters (5) to a temperature of between 70-90°C for pasteurisation and between 105-150°C for sterilisation The duration of exposure is optimised to piovide the maximum reduction in bioburden 30 while maximising the flavoui and other functionality of the material being ^ WO 96/36237 6 treated Typically, heating energy/batch mass can be balanced to attain treatment times of only 0 1-3 0 minutes This short time/high temperature processing yields at least 4 and often 6 log reductions in microbial bioburden At the end of the penetrative heat treatment stage the protective post treatment cooling is commenced This is mandatory to protect the delicate aromatic flavour and functional components Cooling is immediately effected while still underpiessureby again controlling cooling inflow at sparging ports (10) and its release at the pressure legulator valve (6) Rapid 10 cooling reduces the temperature of the matenal being treated to less than 20DC and then coolant inflow is ceased and the pressure within the vessel is allowed to return to atmospheric pressure Stirring is continued throughout the process and until the matenal is discharged directly into the aseptic filler located at (11) EXAMPLE 2 Continuous Flow Apparatus In an alternative arrangement the steps of the method according to the invention maybe applied to material conveyed through three vessels similarly equipped to the batch process so that each stage of the treatment 20 can be applied in a continuous mannei Each vessel is separated by lotary locks and each vessel has a discrete conveyor mechanism A suitable appai atus is depicted in Figure 2 The apparatus shown in Figure 2 employs open conveyor belts however it is to be understood that screw conveyor(s) could be used as an 25 alternative The components (3)-(6) (9) and (10) shown in Figure 2 are as described in Example 1 "WO 96/36237 EXAMPLE 3 - Preliminary Tests Test A Aim To assess the potential of applying heat to herbs and spices to reduce 5 the microbial bioburden Method Target Material Basil Whole peppercorns both with known high bacterial bioburden 10 (greater than 10H cfu/gram) Equipment A device was constructed foi these trials which consisted of a plastic pressure tank from a garden spray with a volume of approx 3 litres This was chosen so that it had adequate stiength to allow for the pressures The 15 pressure entry port was modified by the installation of a car tyre valve A screw down O-ring sealed inlet port was present nonnally for the addition of spray and water Also piesent was a safety pressure release valve which was strengthened appropriately The device, which appeared to be made from natural high or 20 ultrahigh density polyethylene or similar plastic, was tested at pressures gieater than intended to be reached in the test and found to withstand in excess of 3 Bar even when heated Heating was effected in a 750 Watt domestic microwave oven equipped with a rotating caiousel This was adapted to hold the plastic 25 vessel which was microwave transparent and did not heat appreciably when exposed to microwave energy on its own It was found that if it was loaded with approx 15inl of water and exposed for 5 minutes at 2 Bar overpressure all contact surfaces were sterilised and then the vessel could be dried out with the continuation of the heating at atmospheric pressure This piocess 30 was employed before each new trial.

^ WO 96/36237 8 To overcome some initial uneveness of heating a system was devised to tilt the vessel as it was iota ted by the cai ousel, thus mixing the target mateual during exposure Exposures: times and microwave powers and the temperatures achieved were taken with an electronic thermometer equipped with a fast response thermocouple This was repeated with 1 and 2 Bar overpiessure generated with 10 conipiessed air and read by an external pressure gauge to assess the effect of attained pressure on the tempeiatures achieved by varying the times and microwave power From this data a range of exposuies were chosen so that a spectrum of attained temperatures ranging from 70 to 140 deg C could be predicted 15 and duplicate exposures of each target material were made with 1 and 2 Bar compressed air overpressure This was released immediately after the exposure was completed Results 100 gram samples of each target material was exposed to varying Observations - condensation was present but minimal -a noticeable volatile aroma was present on release of the overpressure Target Matenal - loss of at least 30% of the oiganoleptic properties of the matenal was estimated Particularly efiected were the high flavour notes and after taste Microbiological Analyses - Reduction in microbial bioburden paralleled time and temperature with greater than 6 log reductions in Standard Plate Count achieved by the longer times and temperatures employed ^ WO 96/36237 9 Conclusions Significant reductions in microbial counts were observed, easily achieving product pasteurisation and commercial sterility.

Target Material Equipment Test B Aim To develop a means of preventing the loss of volatiles during heating of the herbs and spices by the use of protective cooling and overpressure Method As for Test A As for Test Abut employing overpressuie generated from bottled compressed food grade carbon dioxide contiolled by a regulator This was then used to assist with cooling, while maintaining the overpressure, after the target material had been exposed to heat Additional cooling was piovided by immersing the vessel in an ice bath Exposures As for Test A 2 0 Results Observations - condensation was maikedly reduced as was the volatile aroma Target Material - the material was now colour fast - theie was a considerable reduction m the 25 organoleptic profiles Microbiological Analyses - Not significantly different from Test A Conclusions Without losing microbial effect a definite improvement in the 3 0 condition and functionality of the materials were seen following treatment. 712 7 While this was thought to be of some value means by which the losses of volatiles could be further reduced were sought TestC Aim To further enhance the reduction of volatile loss by the use of a piecooling -tep in the process Method Target Matenal Equipment Exposures As for Test A As for Tests A and B plus either, - piecooling with carbon dioxide sparging (-70 deg C) in the vessel, or - immersion in liquid nitrogen (-170 deg. C) As foi Tests A and B Results Observations Target Material - As forTest B - no discernible loss in volatiles or functionality weie detectable bv organoleptic evaluation for either means of piecooling Microbiological Analyses - ieductions m miciobial bioburden of greatei than 7, approaching 8 log in the case of the mtiogen precooled material Conclusions The aim of achieving a commercially significant reduction in the loss of organoleptic functionality of herbs and spices while maintaining reductions in the microbial bioburden was achieved WO 96/36237 PCT/AU96/00305 11

Claims

1. Claims' 7127 1 A method foi pasteurising or sterilising herbs, spices and other matenals prone to microbial spoilage comprising the steps of 5 (1) cooling said herbs, spices oi other materials to a temperature less than about 0°C, (2) rapidly heating said cooled herbs, spices or other materials to a pasteurising or sterilising temperature, and (3) recooling said herbs, spices or other materials to about room 10 tempeiature, wheiein at least steps (2) and (3) are performed in an environment(s) having a pressure of greater than 1 Bar

2. 2 A method according to claim 1, wherein dunng step (1) the herbs, 15 spices oi other material aie cooled to a temperature less than about -70°C

3. 3 A method according to claims 1 oi 2 wherein during step (1) the heibs spices or othei matenals are cooled to a temperatuie of about -170°C 20

4. 4 A method according to any one of the pieceding claims, wherein step (1) is completed in 0 05 to 5 0 minutes

5. 5 A method according to claim 4 wheiein step (1) is completed in 0 5 to 3 0 minutes 25

6. 6 A method according to any one of the pieceding claims, wherein step (1) is also peifoinied in an envnonment(s) having a piessure greatei than 1 Bai J WO 96/36237 *^ /\ _ PCT/AU96/00305 12

7. 7 ^ " PCT/AU96/OC 3°7127 A method according to any one of the preceding claims, wherein steps (2) and (3) are perfoimed in an environment(s) having a pressure greater than 3 Bar 5

8. 8 A method according to any one of the preceding claims, wherein step (2) is completed in 0 05 to 5 0 minutes

9. 9 A method according to claim 8 wherein step (2) is completed in 0 1 to 3 0 minutes 10

10. 10 A method according to any one of the pieceding claims, wherein step (3) is completed in 0 05 to 5 0 minutes

11. 11 A method according to claim 10, wherein step (3) is completed in 0 1 15 to 2 0 minutes

12. 12 A method according to any one of the pieceding claims wherein the cooling of steps (1) and (3) is achieved by sparging of a suitable coolant gas(es) 20

13. 13 A method according to any one of the preceding claims, wherein the heating of step (2) is achieved by the application of heat generated by combustion, by induction or dielectric heating with electromagnetic radiation microwave or by infra red irradiation 25

14. 14 An apparatus for pasteurising or steiihsing a batch of herbs spices and othei materials pione to microbial spoilage comprising a vessel comprising an inlet means thiough which a batch of heibs, spices oi othei 30 matenals susceptible to microbial spoilage maybe intioduced. or - - j 96/36237 PCT/AU96/00305 307127 means for cooling said batch to a temperature less than about 0"C means for rapidly heating said cooled batch to a pasteurising or stenhsing tempeiature, means for recooling said batch to about room temperature, means for applying and/or regulating a pressure within the vessel during at least the heating and recooling of greater than 1 Bar, and outlet means for removing the treated batch from said vessel

15. 15 An apparatus according to claim 14, wherein the means for cooling coois the batch xo a temperature less than about -70°C

16. 16 An apparatus according to claims 14 oi 15 wherein the means for cooling cools the batch to a temperature of about -170°C

17. 17 An apparatus according to any one of claims 14 to 16, wherein the pressure applying and/or legulating means applies oi regulates a piessure greater than 3 Bar within the vessel

18. 18 An apparatus according to any one of claims 14 to 17, wherein the means for coohng and recoohng compiise sparging ports for a suitable coolant gas(es)

19. 19 An apparatus accoiding to any one of claims 14 to 18, wherein the heating means comprises a means foi applying heat generated by combustion by induction oi dielectric heating with electiomagnetic ladiation microwave or by infra red irradiation

20. 20 An appaiatus for pasteurising or stenhsing heibs spices and other materials prone to microbial spoilage comprising WO 9- .>6237 PCT/AU96/00305 a first vessel comprising, an inlet means thioughSvlxrch Zierbl, Spices or other materials susceptible to miciobial spoilage may be continuously introduced and means for cooling said heibs, spices or other materials to a temperatuie less than about 0°C, 5 a second vessel comprising, means for rapidly heating said cooled herbs, spices or other matenals. and means for applying and/or regulating a pressure of greater than 1 Bar, and a third vessel compnsing means for lecooling the herbs, spices oi other materials to about loom temperature means for applying and/or 10 regulating a piessure of greater than 1 Bai. and outlet means for removing the treated herbs, spices or other materials from said vessel, wherein said first vessel is connected to said second vessel and said second vessel is connected to said third vessel, the airangement being such that the herbs, spices or other materials introduced into the first vessel may be 15 continuously and progressively transferred to the second and then third vessels

21. 21 An apparatus accoiding to claim 20 wherein the means for cooling cools the herbs spices oi other material to a temperature less than about 20 -70°C

22. 22 An apparatus according to claims 20 or 21 wherein the means for cooling cools the herbs spices or other materials to a temperature of about -170°C 25

23. 23 An apparatus according to any one of claims 20 to 22 wherein the first vessel fuither comprises means for applying and/or regulating a piessure greater than 1 Bai WO 96/36237 PCT/AU96/00305 " 307127

24. An apparatus according to any one of claims 20 to 23, wherein the pressure applying and/or regulating means provided in the second and third vessel apply or regulate a pressure greater than 3 Bar.

25. 5 25 An apparatus accoiding to any one of claims 20 to 24, wherein the means for coohng and recooling provided in the first and third vessels comprise sparging ports for a suitable coolant gas(es)

26. 26 An apparatus according to any one of claims 20 to 25, wherein the 10 heating means comprises a means for applying heat generated by combustion, by induction or dielectric heating with electromagnetic radiation microwave, or by infra red irradiation

27. 27 Pasteurised or sterilised herbs and spices treated in accordance with 15 the method of any one of claims 1 to 13

28. A method according to claim 1 substantially as herein described or exemplified.

29. 29 An apparatus according to claim 14 substantially as herein described or exemplified.

30. An apparatus according to claim 20 substantially as herein described or exemplified.

31. Pasteurised or sterilised herbs and spices according to claim 27 substantially as herein described or exemplified. END OF CLAIMS i