Agriculture Reference
In-Depth Information
others 2005a). Additional enhancements in microbial reduction were achieved using
mild heat (50 °C) in combination with the ASC solutions; however, this combination
was detrimental to product quality. In another study by Inatsu and others (2005b),
washing Chinese cabbage with ASC reduced natural aerobic bacteria populations by
2.0 log CFU/g and artifi cially inoculated pathogen populations by
2.0 log, and popu-
lations remained relatively constant through the incubation period of 8 days at 10 °C
with the exception of L. monocytogenes, which gradually increased.
The effi cacy of sanitizers to inactivate E. coli O157:H7 on shredded carrots was
compared when using tap water and simulated process water with a chemical oxygen
demand of 3500 mg/l (Gonzalez and others 2004). ASC eliminated E. coli O157:H7
to undetectable levels (5.25-log reduction) under both tap water and process water
scenarios when used at 1000 ppm for 2 min, and no viable counts were recovered from
the samples treated with ASC after enrichment. Ruiz-Cruz and others (2006) found
that high levels of ASC caused tissue damage to shredded carrots. By reducing the
concentration of ASC to 100-500 ppm, Ruiz-Cruz and others (2007) were still able to
reduce pathogen populations to undetectable levels, achieving reductions of 4.81,
4.84, and 2.5 log CFU/g of E. coli O157:H7, Salmonella , and L. monocytogenes ,
respectively, under both tap and process water conditions. Park and Beuchat (1999)
reported reductions of comparable magnitudes when they evaluated ASC at 800-
1200 ppm on cantaloupes, honeydew melons, and asparagus spears.
When reviewing the effi cacy of ASC in eliminating E. coli O157:H7 from alfalfa
seeds, Taormina and Beuchat (1999) found 500 ppm ASC was effective in reducing
populations of the pathogen by more than 2 logs. Weissinger and Beuchat (2000)
reported slightly lower reductions against Salmonella on alfalfa seeds when using
similar concentrations of ASC solutions.
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Peroxyacetic Acid
Peroxyacetic acid (POAA or peracetic acid) has been used for several years as a sani-
tizer and a disinfectant in the food, dairy, and beverage industry (Cords 1994). Peracetic
acid (C 2 H 4 O 3 ) is produced by the reaction of acetic acid (CH 2 COOH) with hydrogen
peroxide (H 2 O 2 ). The reaction is allowed to equilibrate for several days before the
maximum level of peracetic acid is generated, as shown in this equation:
CH COOH
+ ↔ +
The primary mode of action for peracetic acid is oxidation. Oxidation is the transfer
of electrons, and the stronger the oxidizer the faster the electrons are transferred to
the microorganism rendering them inactivated or killed. It has been suggested that
POAA disrupts the sulfydryl and sulfur bonds in proteins, enzymes and other metabo-
lites causing rupturing of the outer cell walls (Block 1991). POAA has a stronger
oxidizing potential than chlorine, chlorine dioxide, chlorous acid, and hydrogen per-
oxide, but less than ozone.
Peracetic acid is approved for fresh and fresh-cut produce as an antimicrobial
process water additive (Anonymous 2007b,f) at a maximum concentration of 80 ppm.
One advantage of POAA over other oxidizing treatments is its higher tolerance to
organic materials, which allows the active ingredient to maintain effectiveness with
the varying degree of soil loading in the recycled wash water (Herdt and others 2007).
H O
CH COOOH
H O
3
2
2
3
2
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