Agriculture Reference
In-Depth Information
Inoculated apples washed with 5% hydrogen peroxide alone or in combination with
acidic surfactants showed 3 - 4 - log reduction of E. coli when treated for 1 min (Sapers
and others 1999). Liao and Sapers (2000) achieved 3.3-log reduction of Salmonella
Chester on apple skin and 1.52-log reduction in the calyx cavity when washing in a
6% hydrogen peroxide solution for 5 min. The use of 3% hydrogen peroxide for 1 min
reduced levels of E. coli O157:H7 inoculated on the surface of strawberries by
2.2 log CFU/g, which was signifi cantly higher than the other chemical treatments
tested (Yu and others 2001).
The treatments of cantaloupes, honeydew melons, and asparagus with 1% hydrogen
peroxide for 3 min was not as effective as chlorine, ASC, or POAA (Park and Beuchat
1999). However, using 5% hydrogen peroxide for 5 min, Ukuku and Sapers (2001)
observed a 3.2-log reduction of Salmonella Stanley populations that were inoculated
on the surface of cantaloupe. Sapers and others (2001) reported that applying 5%
hydrogen peroxide at 50 °C for 1 min to the rind of melons prior to cutting improved
the microbial quality and shelf life of fresh- cut cantaloupe.
The use of hydrogen peroxide on alfalfa seeds has also been investigated. Taormina
and Beuchat (1999) reported signifi cant reductions of E. coli O157:H7 on alfalfa seeds
using
1% hydrogen peroxide for 3 min with little or no effect on seed germination.
When alfalfa seeds inoculated with Salmonella were treated with 10% hydrogen per-
oxide for 30 sec, counts were reduced from 3.57 log CFU/g to less than 1 log CFU/g
(Beuchat 1997). Weissinger and Beuchat (2000) achieved similar results against
Salmonella on alfalfa seeds using 8% hydrogen peroxide for 10 min.
Organic Acids
Many types of produce, especially fruit, naturally contain organic acids. A number of
organic acids are generally recognized as safe (GRAS) and have broad regulatory
approvals for use in direct food applications. Organic acids are commonly used as
antimicrobials in food preservation. Citric and acetic acids are often used in the fresh-
cut industry to adjust the pH of water in chlorine applications, and lactic acid has been
studied extensively and is used widely in the meat industry as a postevisceration
carcass rinse.
In order for an organic acid to provide microbial control in produce washing it
must be used at or below the dissociation constant for the specifi c acid type. The dis-
sociation constants (or pKa) of most organic acids are between 3 and 5 (Beuchat
1992). Organic acids are very stable in the presence of organic material and generally
present no objectionable odor. A major disadvantage of using organic acids is the
relatively high cost, because it takes large amounts of acid to adjust the system pH,
especially for high-alkaline or buffered water sources. Additionally, due to the low
pH required, they can compromise the organoleptic properties of some produce.
The use of acetic acid to reduce natural microbial populations on lettuce was
studied by Nascimento and others (2003). Populations of aerobic mesophilic bacteria,
yeast and mold, and total coliforms were reduced by 3.91,
2.25 log CFU/g,
respectively, after washing for 15 min in a solution of 4% acetic acid. Washing parsley
leaves in a solution of 2% acetic acid for 15 min reduced populations of Yersinia
enterocolitica by 7 logs (Karapinar and Gonul 1992). Wright and others (2000)
reported that a 2-min treatment with 5% acetic acid was the most effective of several
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