Agriculture Reference
In-Depth Information
others (2004) may not be suffi cient for pathogens to become attached onto the surface,
internalized in the stem scar area, or incorporated in resistant biofi lms, which may
explain the large difference in the reduction of bacterial population among those
studies. Therefore, when reporting results about inactivation of pathogens by any inter-
vention technologies, incubation conditions and incubation time after inoculation
should be indicated.
Mangoes
Whole mangoes were washed in water with or without chlorine (100 ppm) at 11.7 °C
and 50 °C before slicing and packaging (Ngarmsak and others 2006). The washing
process reduced the populations of microorganisms in the stem scar area and on the
whole fruit, and the effect was enhanced by the addition of chlorine and the elevated
temperature. However, none of the treatments prevented the transfer of microbial
contaminants to the fl esh during slicing, and the evidence of spoilage in the form of
discrete fungal colonies was observed in samples stored for 1 week at 5 °C.
Pears
A washing system using a high-pressure spray, warm water (30 °C), a wetting agent,
and rotating soft brushes was found to be effective in decay control without causing
internal or external damage to pear fruit (Bai and others 2006). It is doubtful that the
system would signifi cantly reduce the population of pathogens due to the low tem-
perature (30 °C) applied. Heat injury was observed on pear fruit treated with 40 and
50 ° C water spray.
Pineapples
Wilson Wijeratnam and others (2005) used a hot - water dip (54 ° C for 3 min) to treat
pineapples inoculated with C
halara paradoxa
(10
4
spores/ml), a fungus causing black
rot. The treated fruit was free of disease when stored at 10 °C for 21 days followed
by 48 h at ambient temperature (28
2 ° C). As a contrast, characteristic symptoms of
the disease were observed in fruit that was inoculated and held under similar storage
conditions. No signifi cant difference was observed between hot - water - dip - treated and
untreated controls with respect to fl esh and shell color of fruit, ascorbic acid levels,
and titratable acidity. A signifi cant difference (
p
±
0.05) in total soluble solids (mean
Brix of 14 °) was observed between hot-water-treated and untreated fruit (mean Brix
of 11.5 ° ), irrespective of storage temperature.
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Sprouting Seeds
Decontamination of alfalfa seeds by hot-water treatment in combination with chemi-
cals such as chlorine or ozonated water has been investigated. It was demonstrated
that it is not possible to reduce the numbers of
Salmonella
and
E. coli
O157 : H7 by
more than 5 log CFU/g without affecting seed germination (Jaquette and others 1996;
Scouten and Beuchat 2002; Sharma and others 2002; Suslow and others 2002).
However, Weiss and Hammes (2005) found that hot-water treatment of inoculated
mung bean seeds for 2 - 20 min at 55 - 80 ° C, and radish and alfalfa seeds for 0.5 - 8 min
at 53 - 64 ° C reduced
Salmonella
and
E. coli
O157 : H7 by more than 5 log CFU/g, with
germination rates of more than 95%. The variations among the studies on the
