Hydrogen Peroxide

Hydrogen peroxide is a highly effective antimicrobial agent against bacteria but is less active against yeasts, fungi, and viruses [59]. Characteristics and potential food applications of hydrogen peroxide as a sanitizer for produce were recently reviewed by the author [74]. Hydrogen peroxide may be considered as a potential alternative to chlorine. Numerous studies have demonstrated the efficacy of dilute hydrogen peroxide in sanitizing fresh produce including mushrooms [75-77], apples [16,67,78], melons [34,69,70,73], eggplant, and sweet red pepper [80]. In side-by-side comparisons, dilute (1 to 5%) hydrogen peroxide washes were at least as effective as 200 ppm chlorine [16,79]. When applied to apples with vigorous agitation at an elevated temperature (50 to 60° C), population reductions approaching 3 logs were obtained [67]. However, temperatures exceeding 60°C could not be used without inducing browning of the apple skin. Hydrogen peroxide treatments were ineffective in decontaminating sprouts [42] or the seeds used to produce sprouts [81].

While treatment with hydrogen peroxide vapor can reduce microbial populations on grapes [82], melons [83], and prunes [84], required treatment times are long compared to the application of a dilute hydrogen peroxide dip [85]. The vapor treatments proved to be ineffective with apples [86] and produced discolorations with mechanically damaged berries [85].

The regulatory status of hydrogen peroxide as a washing agent for produce is unclear. The FDA has jurisdiction if the washing treatment is applied as part of a processing operation, while the EPA has jurisdiction if the treatment is applied to a raw commodity. While fresh produce clearly falls within the EPA regulations, fresh-cut produce is under FDA regulations. However, if the wash treatment is applied to the raw produce before cutting, and if this operation is carried out in a receiving area, separate from the processing room, it would appear that EPA regulations apply. Under FDA regulations, hydrogen peroxide is GRAS (generally recognized as safe) for some specified food applications, provided that residual H2O2 is removed "by appropriate physical and chemical means during processing," but the regulation does not cover hydrogen peroxide as a washing or sanitizing agent for produce [87]. According to an Agency Response Letter (GRAS notice no. GRN 000014, May 26, 1999) a petition to the FDA to amend the regulation would be required to seek approval for a new application (in this case, reduction of the microbial load on onions prior to dehydration; http://vm.cfsan.fda.gov/~rdb). Peroxyacetic acid formulations, which contain low levels of hydrogen peroxide (59 ppm), are approved by the FDA for use in washing fruits and vegetables [6]. A higher concentration is permitted if the formulation is used to sanitize food contact surfaces [63] Under EPA regulations, postharvest hydrogen peroxide applications to produce as an antimicrobial treatment are exempt from the requirements of a tolerance if the concentration is <1% per application [88].

The presence of residual hydrogen peroxide should not represent an obstacle to use of this agent as a produce sanitizer. Most fruits and vegetables contain sufficient catalase to permit rapid breakdown of residual peroxide to water and oxygen. Peroxide residues could not be detected in mushrooms, apples, or cantaloupes following hydrogen peroxide wash treatments [16,34,77].

Information on hydrogen peroxide applications can be obtained from FMC Corp. (www.fmcchemicals.com), Solvay Interox (www.solvayinterox. com), US Peroxide (h2o2.com), and Degussa Corp. (www.degussa.com). BiosSafe Systems (www.biosafesystems.com) is marketing a formulation containing hydrogen peroxide and peroxyacetic acids (Storox®) for sanitizing fruits and vegetables; the recommended maximum use level is 0.27%.

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