MXPA00003416A - Method for optimizing the efficacy of chlorous acid disinfecting sprays for poultry and other meats - Google Patents

Abstract

A method for disinfecting a meat carcass by spray application of an aqueous solution containing from about 0.05-0.12%of a metal chlorite and a sufficient quantity of an acid having a pKa of from about 2.0-4.4 to adjust the pH of the aqueous solution to about 2.2-4.5 and to maintain the chlorite ion concentration in the form of chlorous acid to not more than about 35%by weight of the aqueous solution, the molar ratio of the acid to metal chlorite being at least equal to the first pKa of the acid multiplied by the grams/liter concentration of metal chlorite in the aqueous solution. In one embodiment, the meat carcass is poultry.

Description

METHOD TO OPTIMIZE THE EFFICACY OF CHLOROUS ACID DEVICES FOR BIRD MEAT AND OTHER MEAT ICO TECHNICAL FIELD This invention relates to a method for increasing the effectiveness of antimicrobial solutions of chlorous acid used to eliminate pathogenic and decomposing organisms from the surfaces of food products such as poultry meat and other meats.

BACKGROUND OF THE INVENTION The surfaces of freshly killed and non-viscera poultry and other meats are contaminated with microorganisms that are present in the skin, folds, feathers, and hair of the animals from the contact with feces of both the same animal and animals. of nearby animals, as well as by physical transfer of the viscera of the animals through contact with the processing equipment. The bacteria of greatest concern are pathogens such as Salmonella and Campylobacter species, Escherichia coli, including the particularly virulent strain 0157: H7; Lysteria monocytogenes and other harmful enterobacteriaceae. Many of these organisms can survive temperatures to scald dead birds from 50 ° C to 58 ° C, and thereafter by cross-contamination of other parts in the processing line. This is also true for so-called "decomposing organisms", where excessive levels of psychotropic bacteria and lactic acid will reduce the shelf life of final processed poultry and meat products by proliferation to a level where the Odor and textural qualities make meat products unacceptable to the consumer. In poultry processing, until recently, the main focus for reducing surface pathogens was directed to the use of cooling tanks, which included antimicrobials such as chlorine and chlorine dioxide in the processing waters. These were intended to lower the levels of pathogens in dead animals that had been transferred to the water, and reduce their cross-contamination with other parts. Regulatory authorities in the United States have now approved the use of acid chlorite / chlorous acid antimicrobial systems for inclusion in cooler tanks, as well as for direct application to plucked dead birds without viscera immediately prior to their immersion in the waters of the cooler. This results in the destruction of surface pathogens in individual pieces, so that their number is reduced or eliminated so that they can not subsequently contaminate the waters of the cooler and other uncontaminated parts. The application of these chlorite / chlorous acid systems can be either by separate immersion of each bird piece in the liquid germicidal solution, or by spray application. When these systems are used to disinfect the surfaces of the pieces of red meat, after removing the viscera, they are applied as a spray. Chlorite / chlorous acid technology was the subject of U.S. Patent No. 5,389, 390, to eliminate bacteria from poultry meat and other meats. According to that patent, disinfectant solutions can contain about 0.001% up to about 0.2% by weight of metallic chlorite, with a sufficient amount of acid to adjust the pH of the solution from about 2.2 to about 4.5 and to maintain the concentration of the chlorite ion in the form of chlorous acid in not more than 35% weight percent of the total chlorite ion present in the aqueous solution. Under such conditions no more than about 35% weight percent of chlorite ion (CIO2) that is present will exist in the form of chlorous acid (HCIO2). Preferred acids can be strong inorganic acids such as sulfuric, hydrochloric or phosphoric or organic acids of moderate strength such as citric, malic or fumaric acids. It has now been found that when such chlorite / chlorous acid solutions are applied as a spray to surfaces of red meat and dead birds, the levels of disinfection that are reached are significantly lower than those reached by immersion. Thus, there is a continuing need for an effective and safe spray disinfectant to be applied to the animal parts immediately after the viscera removal process, before contaminating organisms can develop a firm point of support on the surfaces of the meat. The present invention satisfies these needs and furthermore provides relative advantages.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention to provide a method for increasing the efficiency to destroy microorganisms in animal parts and fresh meat products such as poultry meat, beef, fish and pork, as well as non-meat products. I eat fruits and vegetables. It is a further and more specific objective of the invention to provide a method for spraying dead birds and dead animal parts during processing in order to increase the effectiveness of acidified sodium chlorite solutions in the destruction of surface microorganisms including such pathogens as Salmonella. and Escherichia coli. It is a further object of the invention to provide a method for spraying waste from animals and parts of dead animals, as well as other food products such as fruits and vegetables, with acidified solutions of sodium chlorite in order to reduce spoilage microorganisms and therefore Increase the commercial life of the sideboard of the processed food products. These and other objects are achieved by the present invention, which provides a composition and method for destroying microorganisms in food products by spraying them with an aqueous solution containing about 0.050% to about 0.12% by weight of a metal chlorite and an amount of acid such that both (a) the pH of that solution will be reduced from about 2.2 to about 4.5, and (b) the molar ratio of the acid to chlorite salt will equal or exceed the first pKa of the activating acid multiplied by the concentration in grams / liter of the metal chlorite in the dew solution. Chlorites of alkali metals, such as sodium or potassium chlorite, or a mixture thereof can be used in the practice of this invention. In one embodiment, the alkali metal chlorite is sodium chlorite. In some embodiments, the acid is selected such that it will not completely ionize upon dissolution in water, and is further limited to the group of acids in which no more than about 1 in 100 of its first ionizable groups will dissociate in aqueous solution. This corresponds to acids having a first PKa value of about 2 or higher, although acids of pKa values greater than about 5 are not suitable for this application.

Suitable acids for use in this invention include phosphoric acid, citric acid, lactic acid, malic acid, fumaric acid and acetic acid or mixtures thereof. When acid mixtures are used, the molar ratio of acid to metal chlorite is based on the average weight of the acid molar concentrations of the acids in the mixture. When disinfecting meat products, the compositions of this invention are used as a spray on animal bones or dead animal parts shortly after having removed the animal's viscera, and / or cut off when applied to the parts of the dead animal. In the practice of the invention, the spray may be applied once or several times, as necessary to reduce microorganisms in dead animals including pathogens. In the case of birds, the dew can also be applied to the dead animal after the removal of the cooling tank. The compositions of this invention can also be used in more than one of these process steps. In one embodiment, the acidified metal chlorite solution is allowed to remain in the disinfected piece 5 for a minimum of 30 seconds before its removal in a subsequent step of the process. These and other aspects of this invention will become apparent by reference from the following detailed description.

BRIEF DESCRIPTION OF THE DIAMETER FIGURE RA represents the pH of aqueous solutions at various ion concentrations ranging from 0 to 5.0 grams per 100 ml.

DETAILED DESCRIPTION OF THE INVENTION 15 As mentioned above, when the chlorite / chlorous acid solutions of U.S. No. 5,389, 390 (hereinafter "the Patent '390') are applied as sprays to the surfaces of pieces of red meat and poultry, the levels of disinfection obtained are significantly lower than those obtained by immersion.

The invention is the result of investigations directed to overcome the deficiencies associated with such spray application of acidified chlorite solutions, particularly in regard to prolonging the availability of hydrogen ions so that a greater amount of the fragrant acid germicide is available for further reduce the level of pathogenic microorganisms. In the practice of this invention, any food product surface can be disinfected by the methods and compositions disclosed herein, including surfaces of meat, fruit and vegetables. However, for purposes of illustration, the food product surfaces exemplified hereinafter are meat surfaces, such as poultry and beef. However, it should be understood that the invention is not limited in this way. It is believed that during the immersion process, there is a surrounding reservoir of virtually inexhaustible acidity, from which to replenish the germicide of spent chlorous acid by disinfection. That is, how ^ proceeds in the following reaction: HCIO2 + [organic matter / bacteria] - »[oxidized materials] + Cl ion" Additional CO2 can form more chlorous acid from other hydrogen ions [H +] in the aqueous medium. These ions [H +] are particularly available from those of the immersion solutions where the acidifying agent has a first pKa greater than ™ approximately 2, such as for phosphoric acid (pKa = 2.15), acid fumaric (pKa = 3.03), citric acid (pKa = 3.13) and malic acid (pKa = 3.40). However, when the chlorite / chlorous acid solutions are sprayed onto the surfaces of the parts, the thin film apparently constitutes an insufficient liquid reservoir from which it can be largely [-T] turned to restore the spent chloro acid. There are a similar deficiency between the spray application of other disinfectants for dead animals, such as chlorine and chlorine dioxide, both of which are gases and are rapidly lost by evaporation of the sprayed fine films. Accordingly, this invention is an improvement over the '390 Patent in which aqueous solutions containing from about 0.001% to about 0.2% by weight of a metal chlorite, adjusted to a pH from about 2.2 to about 4.5, are apply by spraying pieces of fresh birds or other meat, or pieces of dead animals, in order to remove unwanted bacteria. In the practice of the '390 Patent, preferred acids in some embodiments include such strong acids as hydrochloric acid, sulfuric acid and phosphoric acid. When used as a spray on dead animals or pieces of dead animals the metal chlorite is used in a concentration from about 0.075% to about 0.15%, and the solution is adjusted to a pH of about 2.4 to about 3.0. When applied as a spray on bird parts or pieces of dead animals after removing them from the cooling tanks, the concentration of the alkali metal chlorite is about 0.5% to about 0.1% by weight, and is adjusted to a pH of around 2.6 to about 3.2. No disclosure is given in the '390 Patent regarding the amounts of acid to be used for obtaining such pH values. only that "sufficient acid" is used to adjust the pH in the desired range. This adjustment, in essence, is the source of increased levels of chlorous acid, as illustrated in equation (1): Na + CIO2- + H +? HCI02 + Na + (1) It is well established that the effectiveness of acidified chlorite acid systems depends, to a significant degree, on the level of chlorous acid, in both absolute and relative, which is present in the solution. Chlorous acid is the source of antimicrobial oxidants that form transiently when unstable chlorous acid degrades to the more stable reaction products (chloride and chlorate, as well as chlorine oxidizing dioxide). The cascade of reactions that is carried out is represented by the empirical formula that expresses the degradation regime of the chlorous acid, in the absence of significant chloride ion, as expressed in equation (2): dfHCIO »! = k ^ HClOz] 2 + k2 [HCIO2] [CIO2'J2 (2) dt The faster the degradation, when the bacteria is present in the aqueous system, the more quickly they are eliminated. The level of chlorite present also plays a role, but it is set approximately by the initial amount. (Since some of the chlorite is used to create chlorous acid, its amount will vary as the chlorous acid is formed and consumed). When a piece of bird or meat is immersed in a solution of acid chlorite, and the chlorous acid in the immediate vicinity of the meat, it is consumed by the interaction with the organic matter and local bacteria and / or the interaction with the On the surface of the skin, additional chlorite ions in the vicinity of the flesh can attract other nearby hydrogen ions to each other to form additional amounts of chlorous acid. Without the influx of hydrogen ions in this micro domain, the level of chlorous acid remains reduced, and the pH level of that area rises. This loss of continued activity is in accordance with the observation that when acidic chlorite solutions are sprayed onto the pieces of poultry or other meat, there is less efficiency to destroy pathogenic bacteria than when the pieces of meat are submerged in the same solutions. The '390 patent does not specify the nature of the acid that can be used to convert the metal chlorite to the active species of chlorous acids. It certainly indicates that such strong mineral acids as sulfuric and hydrochloric acids are useful, as well as such weaker acids as lactic acid, although lactic acid can result in unwanted effects on the skin. It has been discovered, surprisingly, that there is a subclass of acids that can be used to overcome the deficiencies associated with the spray application of acidified chlorite solutions for poultry and meat surfaces. This group of acids, which includes phosphoric acid, can provide the necessary complementation of hydrogen ions when their use levels are specified in proportion to the amounts of chlorite that are present in the spray disinfection system. Those who have skill in the field of chemistry, will try to overcome the acid deficiency in the micro-domain of the meat sprinkled by simply increasing the initial amounts of acid. However, if that were done using acids such as sulfuric or hydrochloric, the pH of the resulting solution would fall below the range of about 2.2 to about 4.5 which is that required for the '390 Patent. At lower pH's, excessive levels of chlorous acid would result in its rapid degradation, according to the regime expression shown in equation (2) above. In the practice of this invention, it has been found that, if the nature of the acid and its level of use in the spray solution meet the following criteria, one can obtain a disinfectant capacity comparable to that obtained with immersion solutions: a) an acid with a pKa of about 2.0 to about 4.4; b) use of that acid in a concentration such that its molar to chlorite ratio is equal to, or greater than, the pKa value of that acid, multiplied by the concentration in grams / liter of metal chlorite in the dew solution (ie, [acid]: [chlorite] (pka) [chlorite]); and (c) maintaining the pH of the spray solution at a pH from about 2.2 to about 4.5. The present invention describes the use of excessive levels of particular acids, for partial conversion of chlorite to chlorous acid, where a pseudo-dampening effect can be obtained from these acids to obtain stabilized ranges of pH outside their normal buffer ranges. For example, the midpoint of the buffer range of an acid corresponds to its pKa value according to the well-known Henderson-Hasselbach equation (3): pH = pKa + log fForm Anion! (3) [Acid Form] When the Anion Form and the Acid Form of the molecules are equivalent, the final term of the logarithm becomes 0, and pH = pKa. Thus, for example, malic acid will form its most stable buffer at a pH of around 3.40, which is equivalent to its pKa. However, for use in this invention, when a pH is required to effect a more efficient antimicrobial activity at, say, a pH = 2.3 for a sodium chlorite solution of 1.0 grams / liter, it is possible to achieve a pseudo-buffer concentration driven, which will provide a continuous source of hydrogen (H +) ions in a film sprayed with acidic metal chlorite solution, using a molar concentration of malic acid that is at least 3.4 times that chlorite molar concentration. With an initial concentration of sodium chlorite of 0.12% (1.2 gm / liter), for example, which would correspond to a minimum concentration of malic acid of 0.726%. At that concentration, as illustrated in FIGURE, there is a relatively small upward change in pH, from around 2.4, as a small fraction of malic acid is consumed at! convert chlorite to chlorous acid When, at the middle of that clopid sai, the remaining concentration of malic acid is 0.636% and the corresponding pH, according to FIGU RA, is still around 2.4. . If a weaker acid is used, to say succinic acid, with a pKa of 4.19, then the minimum concentration of acid to be used, which corresponds to the same sodium chlorite solution of 1.2 gm / liter, would be 0.79% . As shown in the FIGURE, this point falls on a portion of the pH / concentration curve where relatively small consumption of acid by the chlorite will cause relatively small pH changes. If the lower claimed limit of 0.05% metal chlorite, such as sodium chlorite, were to be used with succinic acid in the spray, the minimum concentration of acid according to this invention would be 0.14%, which corresponds to a pH of around 3.1. When half of the chlorite is consumed by the succinic acid, whose concentration would be reduced to about 0.10%, the pH would rise only to about 3.2. In both of these illustrative cases, a relatively invariable pH can be achieved using acidic materials whose normal buffering ranges (pH ~ 3.40 for malic, pH ~ 4.19 for succinic) are significantly different from the concentration-driven pH values (2.4 and 3.1). for malic and succinic acids, respectively). Acids such as phosphoric acid, with a pKa near the lower range of acid pKa's, from about 2.0 to about 4.4, can only effectively stabilize spray formulations that are planned to be used at pH's close to or slightly above! lower pH limit of 2.2 described in this invention. Under these conditions the similarity between the desired pKa and pH also accommodates a greater contribution of the buffering capacity of the acid to provide a continuous source of hydrogen ions. The following examples are presented to illustrate and further explain the present invention, and should not be taken as limiting in any way. Unless indicated otherwise, all parts and percentages are by weight.

EXAMPLES EXAMPLE 1 This example illustrates the effect of spraying pieces of birds with solutions of activated sodium chlorite with citric acid, at a concentration of 0.12% sodium chlorite, compared to non-sprayed pieces, where the enhanced antimicrobial activity created by the optimization of the levels of citric acid as taught by this invention was determined by measuring the levels of (1) Total Aerobic Organisms, (2) E. coli and (3) Total Coliforms (excluding E. coli). The study was run with groups of 10 commercial pieces for grill of 1 .5-2.0 kg. , of mixed sex, averaging 35 days of age. These were processed in a pilot slaughter facility and sprayed with 90 g of acid chlorite solutions for 30 seconds after washing with water after the removal of viscera. Sprays were allowed to remain on the dead animals for 30 seconds before removing with water during the subsequent processing. A spray solution contained the necessary amount of citric acid to reduce the pH of the solution to 0.12% to about 2.5. The molar ratio of acid / chlorite to that solution was 1 .4, which is below the threshold of 3.76 for this combination of citric acid and sodium chlorite (ie, (pKa of citric acid = 3.13) • (1.2 gm / 1 of chlorite) = 3.76). The other spray solution had a molar ratio of 3.8, which equals that threshold. A small amount of alkali was added to the last solution to adjust its pH up from about 2.38 to about the same value of 2.5 as in the molar ratio solution of 1.4. As mentioned above, the regulatory authorities of U.S. , have approved the use of acid chlorite / chlorous acid solutions for the disinfection of poultry parts in a pH range of 2.5 to 3.2. Consequently, the alkali was added in such a way that the test solution fell within the approved range. It should be noted, however, that alkali is not a necessary component of the disinfectant solution. Following the microbiological evaluation by means of standard procedures, the logarithmic reductions of the three groups of organisms previously identified in the sprayed pieces were determined, in comparison with the corresponding microbial counts in untreated pieces (control). The results are presented in table 1.

TABLE 1 The results in Table 1 show that the use of an acid amount which is at least equal to the molar ratio of the adjusted threshold concentration (CAMR) of citric acid: sodium chlorite of 3.76 (3.13 x 1.2) resulted in a superior logarithmic reduction of the pathogenic organisms tested.

EXAMPLE 2 This example illustrates the effect of spraying chicken pieces with solutions of sodium chlorite and activated phosphoric acid, at a sodium chlorite concentration of 0.085%, in comparison with untreated pieces, where the reinforced antimicrobial activity created by increasing the levels of phosphoric acid was determined by measuring the reductions of increased percentages of (1) Total Aerobic Organisms, (2) E. coli and (3) Total Coliforms (excluding E. coli). The study was carried out in the same way as, and with polio groups similar to those used in example 1. The molar ratio of the increased spray solution (1 .9) approximated the CARM threshold value for the phosphoric acid / sodium chlorite concentration (1.83), compared to the molar ratio of the non-augmented solution ( 0.68). As shown in Table 2, the increased solution showed an improved reduction of potentially pathogenic coliform groups, but not for aerobic organisms. It is generally believed that a significant reduction of the normal flora of the skin, as reflected by the total aerobic organisms, is not desirable, as its continued presence tends to competitively exceed the growth of pathogenic organisms. Thus, the lower effect of the treatment solution increased in acid in the "Total aerobics" of Table 2 can be considered a positive finding.

TABLE 2 EXAM PLO 3 This example illustrates the difference between two sodium chlorite spray compositions, both acidulated with phosphoric acid, in their ability to destroy pathogenic Escherichia coli 01 57: H7. The threshold CARM for both solutions was 2.60 (2.15 X 1.21). One of the solutions had a phosphoric acid level which gave a CARM of 0.661, and the other a CARM of 2.69. Several representative cuts of meat were selected from freshly slaughtered cattle and prepared in a university slaughterhouse according to commercial procedures, and the cut surfaces were spread with an inoculation of an E. coli strain 0157: H7 resistant to mixed rifampicin. in a cow's feces base. After contamination, the cuts were washed with water spray at high and low pressure and separated into a Control group and one or two Test. Two minutes after washing, the Test group (s) were further sprayed for 10 seconds with a sodium chlorite solution activated with phosphoric acid. After draining, all the pieces were then subjected to microbiological analysis. In the following study, for the subthreshold application, the concentration of phosphoric acid in the 0.12% sodium chlorite spray solution was 0.0868% (8.86 millimolar), the chlorite concentration was 13.4 millimolar, and the molar ratio of chlorite acid was 0.661. In this part of the study, two sets of spray solutions were tested, one that includes an active surface agent to promote wetting and one without that. In the supra-threshold study the concentration of phosphoric acid was 36.0 millimolar and, with the same level of chlorite in the spray, the molar ratio of acid to chlorite was 2.69. Surfactant was not included in this suprathreshold spray. The threshold CARM for the combination of acid and chlorite used in these studies is 2.15 x 1.21 = 2.60; thus, the first spray was significantly below the threshold value and the second was slightly exceeded. The results for these studies, expressed in terms of logarithmic reductions in residual E. coli pathogens per cm2 of surfaces of contaminated meat compared to surfaces of washed but untreated meat, are presented in Table 3.

TABLE 3 As the data in Table 3 illustrate, a significantly greater reduction of contaminating red meat pathogens was obtained by adjusting the molar ratio of acid: chlorite to equal or exceeding the threshold CA RM. EXAMPLE 4 This example illustrates the use of citric acid as acidifier of a sodium chlorite solution at 0.12%, according to the procedure of Example 3, where the level of citric acid was selected to slightly exceed the CARM for that combination of acid and chlorite. In this study the cuts of meat were contaminated with one of two pathogens, £ .co // '0157: H7 or Salmonella Typhimurium, in the manner described in Example 3. The concentration of citric acid in the spray solution was 51.57. millimolar, and the molar ratio with respect to the 13.4 millimolar chlorite concentration was 3.86. The CARM for this combination of 3.13 by 1.21 is the threshold value of 3.79, slightly below the molar ratio used in this suprathreshold study. The logarithmic reductions of these organisms, following the treatment with the spray solution in the manner described in Example 3, are presented in Table 4.

TABLE 4 These results illustrate that spraying meats with solutions of sodium citrate activated with citric acid, with citric acid exceeding in concentration the level required by the CAMR threshold, leads to a highly significant reduction in the level of pathogenic surface bacteria. From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not limited except by the appended claims.

Claims (7)

1. REIVI NDICATIONS 1. A method for disinfecting a surface of a food product, comprising contacting the surface by spray application of an aqueous solution containing from about 0.075% to about 0.12% by weight of a metal chlorite, and a sufficient amount of acid having a first pKa from about 2.0 to about 4.4 to adjust the pH of the aqueous solution from about
2. 2.2 to about 4.5 and to maintain the concentration of the chlorite ion in the form of chlorous acid in not more than about 35% by weight of the ion total chlorite present in the aqueous solution, where the molar ratio of acid to metal chlorite is at least equal to the first pKa of the acid multiplied by the concentration in grams / liter of the metal chlorite in the aqueous solution, and with the that when the acid is lactic acid the molar ratio of lactic acid to metal chlorite is in excess of approximation 5.6. The method of claim 2 wherein the molar ratio of acid to metal chlorite is greater than the first pKa of the acid multiplied by the concentration in grams / liter of metal chlorite in the aqueous solution.
3. 3. The method of claim 1 wherein the acid is selected from phosphoric acid, citric acid, lactic acid, malic acid, fumaric acid, acetic acid and mixtures thereof.
4. 4. The method of claim 1 wherein the metal clopto is sodium chlorite
5. 5. The method of claim 1 wherein the aqueous solution is allowed to remain on the surface for a period of time ranging from 30 seconds to 10 minutes before removing it.
6. 6. The method of claim 1 wherein the spray application of the aqueous solution is performed at least twice. The method of claim 1 wherein the food product is a piece of meat. S. The method of claim 7 wherein the piece of meat is bird. 9. The method of claim 7 wherein the piece is beef. 10. The method of claim 7 wherein the piece of meat is selected from fish and pork. 1 1. The method of claim 1 wherein the surface is a fruit surface. 12. The method of claim 1 wherein the surface is a vegetable surface.