Antimicrobial wash

Abstract

A new antimicrobial wash for treating fresh fruits and vegetables to reduce microorganisms, especially human pathogens, comprises an aqueous solution of hydrogen peroxide and one or more fruit acids.

Claims

1. An antimicrobial wash consisting of water, hydrogen peroxide, one or more fruit acids and lactic acid.

2. The antimicrobial wash of claim 1, wherein the fruit acid is one or more of malic acid, citric acid, tartaric acid and mandelic acid.

3. The antimicrobial wash of claim 2, wherein the fruit acid is citric acid.

4. The antimicrobial wash of claim 2, wherein the antimicrobial wash consists of water, 0.02-0.20% H.sub.2O.sub.2, 0.05-1.0 wt. % fruit acid and 0.005-0.15 wt. % lactic acid, and further wherein the lactic acid/fruit acid ratio in the antimicrobial wash is 0.02-2.0, the H.sub.2O.sub.2/fruit acid ratio in the antimicrobial wash is 0.04-1.0, and the H.sub.2O.sub.2/lactic acid ratio in the antimicrobial wash is 0.4-7.5.

5. The antimicrobial wash of claim 4, wherein the fruit acid is citric acid.

6. A process for treating a fresh fruit or vegetable to reduce microbial contamination of the surface of the fresh fruit or vegetable, the process comprising contacting the surface of the fresh fruit or vegetable with an antimicrobial wash consisting of water, hydrogen peroxide, one or more fruit acids and lactic acid.

7. The process of claim 6, wherein the process is carried out on multiple batches of fresh fruit and/or fresh vegetables, and further wherein the antimicrobial wash used to treat at least one of these batches is recycled for reuse in treating at least another of these batches.

8. The process of claim 6, wherein the fruit acid is one or more of malic acid, citric acid, tartaric acid and mandelic acid.

9. The process of claim 8, wherein the fruit acid is citric acid.

10. The process of claim 6, wherein the antimicrobial wash consists of water, 0.02-0.20% H.sub.2O.sub.2, 0.05-1.0 wt. % fruit acid and 0.005-0.15 wt. % lactic acid, and further wherein the lactic acid/fruit acid ratio in the antimicrobial wash is 0.02-2.0, the H.sub.2O.sub.2/fruit acid ratio in the antimicrobial wash is 0.04-1.0, and the H.sub.2O.sub.2/lactic acid ratio in the antimicrobial wash is 0.4-7.5.

11. The process of claim 10, wherein the fruit acid is citric acid.

12. An antimicrobial wash consisting of water, 1-35 wt. % hydrogen peroxide, one or more fruit acids in an amount such that the H.sub.2O.sub.2/fruit acid ratio in this antimicrobial wash is 0.02-4.0, and lactic acid in an amount such that the H.sub.2O.sub.2/lactic acid ratio in this antimicrobial wash is 0.1-40.

13. The antimicrobial wash of claim 12, wherein the fruit acid is citric acid.

Description

EXAMPLES

(1) In order to more thoroughly describe this invention, the following working examples are provided.

Examples 1 and 2 and Comparative Examples A and B

(2) Bay spinach leaves were separated into groups weighing 8 g per group, after which each group was placed on the top of a surface-sanitized test tube rack under a laminar flow hood. Each spinach leaf was then exposed to UV light for 5 min to decrease its concentration of surface microbes. After 5 min, each leaf was carefully turned over using tongs or ethanol-sanitized nitrile gloves and the other side of the leaf then exposed to UV light for an additional 5 min.

(3) Each decontaminated bay spinach leaf was then inoculated with certain human pathogens, in particular E. coli 0157:H7, Listeria monocytogenes and Salmonella serotypes, by flooding each set of leaves in an inoculum of the pathogen for 30 sec. The excess inoculum was then shaken off with tongs, after which the leaves were air dried on the top of their test tube racks in a laminar flow hood for 1 hour. Then each sample was added to 500 ml of an antimicrobial wash treatment solution in a 1 or 2 liter beaker, after which the contents of each beaker were stirred with a sterile pipette or stir bar for 5 minutes. The treated leaves were then removed from their antimicrobial wash solution, shaken to remove excess liquid, and then added to 32 ml of DE (Dey-Engley) neutralizing broth in a sterile/filtered/80 ml stomacher bag. The leaves were then pummeled in the mini-stomacher for 3 min, and contents of each bag then filtered to recover the supernatant liquid. The supernatant was then used to make serial dilutions which were plated onto Tryptic Soy Agar+0.1% sodium pyruvate+100 ppm nalidixic acid and incubated for 24 h at 37° C. Survival pathogens in the antimicrobial wash water after treatment were also plated out. Cfu (colony forming units) were manually counted or counted by a colony counter.

(4) The counts obtained from each sample were then compared with a positive control in which the inoculated leaves were washed with 0.1 wt. % peptone water in place of antimicrobial solutions (as Example B in Table 3).

(5) The counts obtained from each sample were then compared with a positive control in which the inoculated leaves were added directly to the DE neutralizing broth without being contacted with an antimicrobial treatment solution first,

(6) Four different aqueous antimicrobial wash solutions were tested, the compositions of which are set forth in the following Table 3:

(7) TABLE-US-00003 TABLE 3 Chemical Compositions of Aqueous Antimicrobial Washes Example Composition A 20 ppm peroxyacetic acid 1 0.344 wt. % malic acid, 0.051 wt. % lactic acid, 0.104 wt. % H.sub.2O.sub.2 2 0.462 wt. % malic acid, 0.068 wt. % lactic acid, 0.14 wt. % H.sub.2O.sub.2 B 0.1 wt. % peptone water

(8) The results obtained are set forth in the following Tables 4, 5 and 6:

(9) TABLE-US-00004 TABLE 4 Antimicrobial Wash Reduction of E. coli 0157:H7 from baby Spinach Log reduction of E. coli Population of 0157:H7 0157:H7 from baby (log) in antimicrobial Example spinach/5 minutes wash water A 0.53 0.00 1 1.16 0.00 2 1.58 0.00 B 0.77 3.77
Baby Spinach was inoculated to 6.72 log CFU/g of E. coli 0157:H7 before antimicrobial solution wash

(10) TABLE-US-00005 TABLE 5 Antimicrobial Wash Reduction of Salmonella from baby spinach (Four Salmonella strains: Stanley, Montevideo, St. Paul and Newport) Population of Log reduction of Salmonella (log) in Salmonella from baby antimicrobial wash Example spinach/5 minutes solution A 0.78 0.00 1 1.18 0.00 2 1.35 0.00 Sterile deionized water 0.78 1.73
Baby Spinach was inoculated to 7.43 log CFU/g of Salmonella four strains: Stanley, Montevideo, St. Paul and Newport

(11) TABLE-US-00006 TABLE 6 Antimicrobial Wash Reduction of Listeria monocytogenes from baby spinach Five strains, L2624 (CDC 2001 cantaloupe outbreak strain, serotype 1/2b), L2625 (CDC 2011 cantaloupe outbreak strain, serotype 1/2a - different molecule type than L2624), L008 (Canadian cole slaw/cabbage epidemic outbreak, serotype 4b), L499 (Historic U.S. outbreak strain human isolate, serotype 1/2a), L502 (Historic 1994 Illinois foodborne outbreak serotype 1/2b)” Log reduction of L. Population of L. Antimicrobial monocytogenes from baby monocytogenes (log) in Wash spinach/5 minutes antimicrobial wash water A 0.91 0.00 1 1.09 0.00 2 0.93 0.00 B 0.40 2.59
Baby Spinach was inoculated to 8.00 log CFU/g of L. monocytogenes

(12) As can be seen from the above examples, the inventive aqueous antimicrobial wash is considerably more effective than conventional antimicrobial compositions in terms of reducing microbial contamination of the fresh vegetable being treated.

(13) After the above treatments had been completed, the wash waters used in each example were also analyzed for pathogens. It was found that the wash water used in Examples 1 and 2 representing this invention contained no pathogen accumulation. In contrast, the wash water used in Comparative Example B (0.1 wt. % peptone water) contained 3.77 log E. coli O157, 1.73 log Salmonella and 2.59 log L. monocytogenes accumulations after a single wash of inoculated baby spinach.

Example 3-9

(14) In this example, the general method of BS EN 1276 was used to assess the effectiveness of seven additional aqueous antimicrobial wash compositions of this invention in connection with reducing microbial contamination of the wash water used for treating fresh fruits and vegetables. The make-up of these seven additional aqueous antimicrobial wash compositions was generally the same as those of the above Examples 1 and 2, although the total concentration of active ingredients in these compositions varied from most concentrated (Example 3) to least concentrated (Example 9). The microorganism used in this test was E. coli O157, the interfering substance was bovine albumin and the contact time was 5 minutes.

(15) A standard test suspension containing microorganism cells at a concentration of 8.0-9.0 log/ml was prepared as an inoculum. One ml of the interference substance was pipetted into a sterile 14 ml test tube, followed by 1 ml of the microorganism test suspension and mixed well. After 2 minutes, 8 ml of the aqueous antimicrobial wash being tested was added and vortexed to mix. After a contact time of 5 minutes, 1 ml of the aliquot was transferred to a sterile 14 ml test tube, which was neutralized by diluting to a DE-neutralizing broth. The composition was then plated onto Tryptic Soy Agar+0.1% sodium. After incubating 24 hrs at 37° C., the colony forming units were counted manually (only colonies with 25-250/plate were counted), and the concentration of microbes in terms of CFU/ml was then calculated using the formula CFU/ml=colonies counts×dilution factor.

(16) Two different interference substances were used. The first interference simulating “dirty conditions” contained 3 g of bovine albumin/100 ml. One ml of this interference was pipetted into the test tube, followed by adding 1 ml of the microbial suspension. The final concentration of bovine albumin in this test tube was 0.3%, thereby simulation dirty condition.

(17) The second interference simulating “clean conditions” contained 0.3 g bovine albumin/100 ml. One ml of this interference was pipetted into the test tube, followed by adding 1 ml of the microbial suspension. The final concentration of bovine albumin in this test tube was 0.03%, thereby simulation clean conditions.

(18) The results obtained are set forth in the following Table 7:

(19) TABLE-US-00007 TABLE 7 E. coli O157 Inactivation under both “DIRTY” & “CEALN” conditions per BS EN method (2009) E. coli Log Reduction E. coli Log Reduction CLEAN condition/5 minutes DIRTY condition/5 minutes Examples contact time contact time 3 ≧6.9 ≧6.9 4 ≧6.9 ≧6.9 5 ≧6.9 ≧6.9 6 ≧6.9 ≧6.9 7 ≧6.9 ≧6.9 8 7.3 ≧6.9 9 7.2 3.84

(20) As can be seen from this table, except for the most dilute composition, Example 9, all of these inventive aqueous antimicrobial washes achieved a reduction in E. coli concentration of at least log 6.9 when tested under both the “clean” and “dirty” conditions of this test. Moreover, even the most dilute of these composition, Example 9, achieved a reduction in E. coli concentration of at least log 6.9 when tested under the “clean” conditions of this test. This clearly demonstrates that the inventive antimicrobial washes will be highly effective in terms of reducing the microbial contamination of wash water which is recycled for reuse in connection with the antimicrobial treatment of multiple batches fresh fruits and vegetables.

(21) Although only a few embodiments of this invention have been described above, it should be appreciated that many modifications can be made without departing from the spirit and scope of this invention. All such modifications are intended to be included within the scope of this invention, which is to be limited only by the following claims: