AU752652B2 - Solution useful for bacterial decontamination of foodstuffs and method for using same - Google Patents

Abstract

The invention concerns a method for treating foods characterised in that it comprises a step which consists in contacting said food with a solution having an OH-concentration ranging between 0.02 and 0.2 and in that said solution further comprises a tribasic salt of orthophosphoric acid such that the ratio of the initial OH-ion concentration, expressed in equivalent per litre, to the orthophosphate concentration is not less than 1/4, advantageously 1/3. The invention is useful for bacterial decontamination of foodstuffs.

Description

SOLUTION WHICH IS USEFUL FOR THE BACTERIAL DECONTAMINATION OF FOODSTUFFS AND PROCESS FOR USING IT The present invention relates to aqueous solutions which are useful for the bacterial decontamination of foodstuffs. The invention relates more particularly to weakly concentrated solutions containing both a basic compound and a tribasic phosphate.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

The bacterial contamination of foodstuffs is a problem which is of more and more increasing concern to the authorities and companies distributing foodstuffs. The reason for this is that bacterial contamination causes an impairment of foods and cdi lead to serious poisoning of the end consumer; whether this poisoning is a direct poisoning when the food is eaten uncooked without destruction of the microbial flora, or whether 15 this food is co.ntaminated with toxins released by the bacteria, during their lifetime or when they die.

The problem is particularly acute in the case of animal productions.

Many processes for decontaminating animal foodstuffs have already been ppe H proposed. However, only a few have a balance between their cost and the efficacy o• eeoe *o e* WO 00/18246 PCT/FR99/02226 2 which would allow them to be used on an industrial scale.

Specifically, the problem is complex since, on the one hand, the surface of the foodstuff should be decontaminated, and, on the other hand, subsequent recontamination should be avoided, either during the treatment or in the course of a subsequent or prior rinsing operation.

Moreover, the efficacy of the decontamination should be extremely rapid; failing this, the treatments cannot be carried out on an industrial scale since they would involve considerable treatment volumes.

In addition, when the treatment is directed towards the carcasses of land animals and uses an aqueous phase, a prolonged contact runs the risk of being problematic and may lead to a gain in weight by incorporation of water into the foodstuffs treated by the process, this gain in weight being regulated in many countries.

The problem of contamination is particularly acute in foods or foodstuffs which have not undergone any preparation, and/or which have not been cooked.

Mention may thus be made of plant productions directly after harvesting and animal foodstuffs immediately after fishing or slaughtering.

WO 00/18246 PCT/FR99/02226 3 Thus, products which may be treated include the carcasses of dead animals a short time after the animals have been slaughtered for consumption.

Without wishing to be limiting hereby, mention may be made of the carcasses of quadrupeds, in particular of bovids such as bovines (for example buffaloes, aurochs and bison), antelopes, ovines, caprines (including game such as stags, chamois, deer, elks, moose, izards and roe deer), suids (for example pigs, boars and peccaries), lagomorphs (such as rabbits, hares and agoutis) as well as the carcasses of fowl, among which mention may be made of all wild and/or rearing fowl, from the smallest (for example trogons and larks) to ratites (for example ostriches), in particular including passerines (for example thrushes), gallinaceans (for example hens, quails, guinea fowl, partridges, turkeys and grouse) and anatids (for example ducks, geese and teals) The treatment may also apply to reptiles and fish.

The carcasses may be treated before, but advantageously after skinning. In the case of birds, it is desirable for this treatment to be carried out after plucking.

One of the most awkward problems in the treatment of animal carcasses lies in the fact that these carcasses must often be washed with large amounts of water and that this water is often the vector for transferring a contamination from one particular carcass to all of the carcasses.

One of the solutions recommended to date is the use of bleach at concentrations of about several hundred PPM, in general at about 600 to 800 PPM.

However, some scientists consider that the use of bleach for treating carcasses may involve a risk of cancer when the bleach concentrations are high and in particular when they are higher than 500 PPM of chlorine.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

In a first aspect, the present invention provides a process for treating foods, comprising a step of placing said food in contact with a solution having an OHconcentration of between 0.02 and 0.2 N and said solution also comprising a tribasic salt of orthophosphoric acid such that the ratio between the initial concentration of OH ions, 15 expressed as equivalents, and the concentration of orthophosphates is at least equal to 1/4.

S: Preferably, the ratio is at least equal to 1/3. More preferably, the ratio is at least .o :equal to 1.

According to a second aspect, the present invention provides use, for bacterial decontamination, of a solution with an OH concentration of between 0.02 and 0.2, wherein a tribasic salt of orthophosphoric acid is added thereto such that the content of orthophosphate species is at least equal to 0.01 M and not more than 0.1 M.

According to a third aspect, the present invention provides foods treated according to the process of the first aspect.

25 Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

It is advantageous for the content of orthophosphorate species to be at least equal to 0.01 M and not more than 0.1 M.

ST The initial content of OH ions is advantageously at least equal to 0.05 M.

The expression "initial concentration of OH ions" means the concentration of OH ign of the solution without the tribasic salt of orthophosphoric acid.

In other words, it is thus the concentration of OH- ions which is obtained in the absence of the tribasic salt of phosphoric acid, more generally in the absence of any phosphate. This value of the OH may be readily measured by techniques that are well known to those skilled in the art by means of a pH meter with electrodes adapted to the type of medium and to the pH *o*oo e e WO 00/18246 PCT/FR99/02226 6 range under consideration, i.e. to the range between about 12 and about 13.

The values are given for a temperature of 250C and at atmospheric pressure.

Given the inherent risk of denaturing the food when a very basic solution is used, it is preferable to use solutions with an initial content of OH- ions of not more than 0.1 N (corresponding at 25 0

C

to a pH of 13) It is also preferable for the content of phosphate ions in the solution to be not more than 0.1 N, so as to prevent the solution from being overloaded with mineral elements.

In order to obtain a significant synergistic effect between the OH- ions and the phosphate species, it is preferable for the latter species to be present at a concentration at least equal to 0.02 M. The OHions are advantageously in the form of alkali metal hydroxides, ammonium hydroxides or quaternary phosphonium hydroxides, or in the form of hydroxide(s) of cation(s) masked by complexation (essentially complexing agents that are neutral complexers or sequestering agents, such as, for example, crown ethers) However, given the enormous amounts to be treated and the price of the latter compounds, it is WO 00/18246 PCT/FR99/02226 7 preferable for the cations associated both with the hydroxide ion and with the P0 4 3- ion to be alkali metals or mixtures of various alkali metals. Lithium is not preferred, far from it, for this application, the most effective being potassium, rubidium and caesium, a good compromise lying in the use of the sodium or potassium ion and mixtures thereof. Although rubidium and caesium give excellent results, they are far too expensive for this type of application.

The OH- ions may be introduced by any means known to those skilled in the art, whether in the form of salts of very weak acids, or by reaction of precipitable compounds (for example a successive mixture of trisodium phosphate combined with a calcium hydroxide thus precipitating phosphate and leading to the formation of sodium hydroxide in situ).

Products such as oxylith (Na 2 0 2 which may give rise to sodium hydroxide and hydrogen peroxide, which will reinforce the action of the anticontaminating system may also be used, and under basic conditions which give the hydrogen peroxide an extremely short lifetime.

It may also be envisaged to introduce the OHions in the form of alkoxides which will produce, by action on water, a hydroxide and an alcohol, which may be evaporated off during the treatment.

WO 00/18246 PCT/FR99/02226 8 Up to a content of about the alcohol does not modify the properties of the solution.

However, it is simpler to introduce the hydroxide ions in the form of alkali metal hydroxide(s), but also alkali metals or a mixture of alkali metal phosphates.

The solution targeted by the present invention is particularly suitable for rinsing and may be used, for example, before or after another treatment for decontamination of foodstuffs per se. It may be used more specifically to prevent contamination after a step of contamination, for example in the system denoted as a "tank chiller", i.e. in a system of cooling in a tank of water at high flow rate.

The solution according to the present invention can also be used for decontamination, by simply adapting the contact time. However, when the content of mineral ions is low, prolonging the contact time runs the risk of being problematic and may lead to a gain in weight by incorporating water into the foodstuff treated by the process, this gain in weight being regulated in many countries.

The decontaminating system has the advantage of being compatible with many other decontaminating systems, whether organic or mineral.

WO 00/18246 PCT/FR99/02226 9 The effect of the solutions according to the invention may be reinforced with oxidizing agents; among these, mention may definitely be made of permanganates and dichromates, but the latter are colored and may under certain conditions lead to precipitates, which may introduce a problem into the process. Thus, oxidizing agents containing ozone and/or hydrogen peroxide, or even hypochlorites, are preferred.

From the point of view of the efficacy of the treatment, it is desirable for the oxidizing power of the solution to be at least equal to 0.001 N, advantageously equal to 0.002 N and preferably equal to 0.005 N (electron equivalents per litre). However, the concentration of these agents should be limited as much as possible, since they do not always have a good reputation. Thus, one of the best agents would be ozone, if not for its cost. Otherwise, in the event of potentiating the solutions according to the invention with oxidizing agents, it is recommended to limit the oxidizing power to 0.05 N, advantageously to 0.02 N and preferably to 0.01 N.

The hypochlorite effect is reinforced by the system according to the present invention, which makes it possible to use low concentrations, generally concentrations of less than 500 PPM (as mass of WO 00/18246 PCT/FR99/02226 chlorine C12 relative to the mass of treating solution), more generally less than 200 PPM, and it is even possible to observe an effect between the two systems at concentrations of chlorine contained of less than 100 PPM.

Other elements, such as carbonates, may also be added to the solution, provided that this does not alter the initial basicity.

Thus, the main use of this solution is for placing in contact with the foodstuff to be treated, this placing in contact usually being carried out by dipping, spraying or misting. It is desirable for the dipping, spraying or misting time to be not more than /2 hour, advantageously not more than 1/5 hour and preferably not more than 1/10 hour. It is at least 1 second, advantageously 10 seconds and preferably seconds. The contact may be partially continued after the dipping, spraying or misting, if there is no rinsing operation.

This placing in contact may be carried out at a temperature at least equal to OOC, advantageously at about 10 0 C, preferably at 20 0 C. In the present description, the term "about" is used to emphasize the fact that the values which follow it correspond to mathematical round-ups and in particular that when the figure(s) furthest to the right of a number is (are) WO 00/18246 PCT/FR99/02226 11 zeroes, these zeroes are positional zeroes rather than significant figures, except, of course, unless otherwise specified.

It is preferable, in order to prevent the foods from being impaired, not to exceed the temperatures which modify the structure of the food. As regards carcasses and foodstuffs of animal origin that are untreated, this placing in contact may be carried out at a temperature equal to 800C and advantageously equal to 700C.

The pressure has very little influence on the process according to the present invention at atmospheric pressure or at a pressure thereabout, and at any altitude.

As has already been mentioned, the foodstuff to be treated is advantageously an animal foodstuff, whether this is carcasses or carcasses after cutting up, but the results may be obtained on other products such as, for example, eggs. This decontamination system also functions very well for compounds which are intended for freezing.

The non-limiting examples which follow illustrate the invention.

Example Measurement of the effect of TSP in the presence of different concentrations of NaOH on WO 00/18246 PCT/FR99/02226 12 Salmonella tyhpimurium IPL and Escherichia coli NIJH-JC2.

B.1 Principle B.1.1. Culturing A brain heart infusion (BHI) conical flask (10 ml) was inoculated with a colony of Salmonella typhimurium IPL or of E. coli NIJH-JC2, and then placed at 37 0 C on a shaker table. After 18 h, the bacterial count was, respectively, 6 x 109 and 7 x 109 colony forming units per milliliter (CFU/ml).

After diluting 500-fold with BHI culture medium, the bacterial count was 1 x 107 CFU/ml. This diluted culture was then used for the rest of the experiment.

B.1.2. Samples The various mixtures of TSP and NaOH were prepared beforehand, such that the concentrations obtained in these mixtures are twice that of the final concentrations tested. Thus, for example, the TSP had a concentration of 0.8%.

At t:0 min, 0.5 ml of bacteria (diluted 500-fold) was added to 0.5 ml of the different mixtures and left in contact for WO 00/18246 PCT/FR99/02226 13 s. 100 .1 were taken and then serially diluted (10-fold) in sterile distilled water containing NaCi (9 100 .1 of each dilution were spread on a Petri dish (BHI 1.5% agar-agar). For certain samples, 100 .1 were spread directly on the dish without being diluted.

The dishes were incubated for 18 h at 37 0

C.

The colonies present on the.dishes were counted and the number of CFU (colony-forming units)/ml deduced.

B.2 Results CFU/ml Samples S. typhimurium E. coli Control 7.00 x 106 2.01 x 106 Control 1.20 x 107 2.08 x 106 TSP 4.86 x 106 4.06 x 106 TSP NaOH 1.106 2.105 TSP NaOH 5.02 x 104 2.25 x 10 4 TSP NaOH 5.02 x 104 5.54 x 104 TSP NaOH (3.35) 5.00 x 104 4.32 x 10 3 TSP NaOH 5.02 x 104 1.52 x 104 TSP NaOH (3.45) 5.00 x 104 5.19 x 103 TSP NaOH 5.00 x 104 3.75 x 104 TSP NaOH 1.37 x 104 3.35 x 102 TSP NaOH 2.08 x 10 3 2.50 x 100 NaOH 3.88 x 106 2.57 x 106 NaOH 3.38 x 106 2.84 x 10 6 NaOH 9.50 x 105 1.80 x 106 NaOH 1.78 x 106 4.11 x 10 WO 00/18246 PCT/FR99/02226 14 B.3 Conclusion When used alone at anhydrous TSP induces no bactericidal action during the time of the experiment (30 either on a culture of S. typhimurium IPL or of E. coli NIHJ-JC2. Exposing these cultures to NaOH alone (3.1 to 3.5 g/l) does not induce any bactericidal action either. However, when used at 3.7 g/l, sodium hydroxide induces a decrease in the CFU/ml by a factor of 4 to 5 on S. typhimurium and E. coli, respectively.

When used in combination, TSP and sodium hydroxide (3.2 g/l) induce a decrease of 2 log of the number of CFU/ml on the two cultures.

Increasing the sodium hydroxide concentration (3.7 g/l) increases the bactericidal action log) on the E. coli culture.

The simultaneous addition of TSP and NaOH (4 g/l) induces a reduction in the number of CFU/ml by 3 log for S. typhimurium and of 6 log (limit of the experiment) for E. coli.

It is thus seen that strong synergism is induced between TSP and sodium hydroxide, when it is added at a concentration of greater than 0.4 g/l and especially greater than 3.2 g/l.

Claims (21)

1. Process for treating foods, comprising a step of placing said food in contact with a solution having an OH- concentration of between 0.02 and 0.2 N and said solution also comprising a tribasic salt of orthophosphoric acid such that the ratio between the initial concentration of OH- ions, expressed as equivalents, and the concentration of orthophosphates is at least equal to 1/4.

2. Process according to Claim 1, wherein the ratio is at least equal to 1/3.

3. Process according to Claim 1, wherein the ratio is at least equal to 1.

4. Process according to any one of Claims 1 to 3, wherein the content of orthophosphate species is at least equal to 0.01 M and not more than 0.1 M. Process according to any one of Claims 1 to 4, wherein the initial content of OH- ions is at least equal to 0.05 N.

6. Process according to any one of Claim 1 to 5, wherein the initial content of OH- ions is not more than 0.1 N.

7. Process according to any one of Claim 1 to 6, wherein the content of phosphate "ions is not more than 0.1 N.

8. Process according to any one of Claim 1 to 7, wherein the content of phosphate species is at least equal to 0.02 M. •o•

9. Process according to any one of Claims 1 to 8, wherein the OH- ions are in the 20 form of hydroxides of alkali metals, of ammonium or of phosphonium, or of cations masked by complexation.

10. Process according to any one of Claims 1 to 9, wherein the OH ions are in the form of sodium hydroxide or potassium hydroxide.

11. Process according to any one of Claims 1 to 10, wherein the phosphate is an alkali 25 metal phosphate or a mixture thereof.

12. Process according to any one of Claims 1 to 11, wherein said step is a rinsing step.

13. Process according to any one of Claims 1 to 12, wherein said placing in contact is carried out by dipping, spraying or misting.

14. Process according to any one of Claims 1 to 13, wherein said placing in contact is carried out at a temperature at least equal to 0"C. Process according to Claim 14, wherein said placing in contact is carried out at a mperature at least equal to 10 0 C. -16-

16. Process according to any one of Claims 1 to 15, wherein said placing in contact is carried out at a temperature of not more than

17. Process according to Claim 16, wherein said placing in contact is carried out at a temperature of not more than

18. Process according to any one of Claims 1 to 17, wherein said placing in contact is carried out at atmospheric pressure.

19. Process according to any one of Claims 1 to 18, wherein said food is an animal food. Use, for bacterial decontamination, of a solution with an OH- concentration of between 0.02 and 0.2, wherein a tribasic salt of orthophosphoric acid is added thereto such that the content of orthophosphate species is at least equal to 0.01 M and not more than 0.1 M.

21. Use according to Claim 20, wherein the ratio between the initial concentration of OH ions in the concentration of orthophosphates, expressed as equivalents, is at least equal to 1/4.

22. Use according to Claim 21, wherein the ratio is at least equal to 1/3. S: 23. Use according to Claim 21, wherein the ratio is at least equal to 1. S•24. Use according to any one of Claims 20 to 23, wherein the solution also comprises a bactericide or a bacteriostat. S 20 25. Use according to any one of Claims 20 to 24, wherein the solution also comprises not more than 200 PPM of bleach (expressed as mass of chlorine C12).

26. Foods treated according to the process of any one of claims 1 to 19.

27. Process for treating foods, substantially as herein described with reference to any one of the examples but excluding comparative examples. S 25 28. Use, for bacterial decontamination, of a solution, substantially as herein described with reference to any one of the examples but excluding comparative examples. DATED this RHODIA CHIMIE Attorney: PAUL G. HARRISON Fellow Institute of Patent and Trade Mark Attorneys of Australia of BALDWIN SHELSTON WATERS