Agriculture Reference
In-Depth Information
Aqueous ozone has been tested for its effi cacy in the decontamination of lettuce (Kim
and others 1999b; Montecalvo 1998), and alfalfa seeds and sprouts (Sharma and others
2002a,b; Wade and others 2003). Kim and others (1999a) reported a 4-log reduction
of mesophilic bacteria on lettuce when exposed to 1.3 mg/l ozone. Similarly,
Montecalvo (1998) reported 4-log reduction of
E. coli
O157:H7 on lettuce when
exposing lettuce to 3 mg/l ozone for 3 min Sharma and others (2002a,b), and Wade
and others (2003) both reported that extending the exposure time of sprouts to ozone
increased log reduction of
L. monocytogenes
and
E. coli
O157:H7. Spotts and
Cervantes (1992) and Kim and others (1999b) proposed that bacterial survival of
ozone treatments was not attributed to a lack of effectiveness of ozone, but actually
to a lack of contact with ozone when bacteria were entrapped in the surface wounds.
Treating vegetables with ozone gas at 170 mg/l at 25 °C for 20 min and then immersing
vegetables in an aqueous solution of ozone at 20 mg/l at 20 °C provided a wider anti-
microbial spectrum than treatment with ozone gas or solution alone.
Ozone treatment was reported to extend the shelf life of fresh produce by removing
ethylene gas to slow down ripening (Rice and Farquhar 1982). Produce tested for this
purpose included blackberries (Barth and others 1995), black pepper (Zhao and
Cranston 1995), grapes (Sarig and others 1996), broccoli, carrots, and tomatoes
(Hampson and Fiori 1997). Barth and others (1995) reported that fungal development
on blackberries was suppressed during storage at 2 °C in air with 0.3 mg/l ozone.
Baranovskaya and others (1979) reported that the shelf life of potatoes was extended
to 6 months with good quality at 6-14 °C and 93-97% relative humidity with 2 mg/l
ozone.
Hydrogen Peroxide
Hydrogen peroxide is listed as GRAS for use in specifi c food products as a bleaching
agent, an oxidizing and reducing agent, and an antimicrobial agent (Anonymous
2007e). Hydrogen peroxide is a well-established antimicrobial agent used as an anti-
septic on wounds, for dental and medical instrument disinfection, and as a sterilizing
agent for aseptic packaging containers (Block 1991). As an antimicrobial agent, it is
allowed for use in cheese making, during the preparation of modifi ed whey, and during
thermophile-free starch production. However, it is not specifi cally approved by the
FDA for use on minimally processed fruits and vegetables unless it is used in combi-
nation with acetic acid to form peroxyacetic acid (Anonymous 2007b). The EPA, on
the other hand, exempts from the requirement of tolerance application rates of
1%
hydrogen peroxide on all food commodities when it is applied to growing or posthar-
vest crops (Anonymous 2007g). Although vaporized hydrogen peroxide provides
some promise for some commodities (Sapers and Simmons 1998; Simmons and others
1997), the use of hydrogen peroxide for washing fresh and fresh-cut fruits and veg-
etables has been investigated by several researchers.
The treatment of lettuce leaves with 2% hydrogen peroxide at 50 °C for 90 sec
reduced pathogenic populations and maintained good sensory qualities for up to 15
days. Specifi cally, 4.5-, 4.7-, and 2.7-log reductions of
Salmonella
enteritidis,
E. coli
O157:H7, and
L. monocytogenes
, respectively, were obtained (Lin and others 2002).
Larger reductions in pathogen populations were observed with a combination of lactic
acid and hydrogen peroxide; however, the quality of the lettuce was compromised.
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