Agriculture Reference
In-Depth Information
Table 13.2.
The effect of hot-water pasteurization on total plate count (TPC) and yeast and
mold count, as well as the population of inoculated
S. enterica
serovar Poona and
E. coli
ATCC
25922 on the fruit rind
Treatments
TPC
Yeast and Mold
S
. Poona
E. coli
Not washed
5.1
±
0.6 a
4.4
±
0.4 a
6.2
±
0.6 a
5.9
±
0.5 a
Water wash
5.0 ± 0.5 a
4.4 ± 0.5 a
6.3 ± 0.2 a
5.5 ± 0.1 a
Chlorine (20 μ g/ml)
4.8 ± 0.8 a
3.7 ± 0.7 b
NT
NT
76 ° water wash
3.9 ± 0.4 b
1.5 ± 0.7 c
0.8 ± 1.0 b
0.3 ± 0.3 b
For the study of
S
. Poona and
E. coli
, cantaloupes were dip-inoculated with
E. coli
and
Salmonella
Poona
for 5 min, allowed to air dry for 2 h, and stored at room temperature for 24 h prior to treatment at room
temperature or 76 °C for 3 min (Annous and others 2004). For the study of TPC and yeast and mold, whole
fruit were submerged into 10 ° C water for 20 min, 20 ppm chlorine at 10 ° C for 20 min, or 76 ° C water for
3 min (Fan and others 2008 ).
E. coli
and
S
. Poona populations were enumerated on MacConkey and xylos lysine tergitol-4 agar medium,
respectively.
Data represent the means
±
standard deviations (n = 4 - 9).
NT: not tested.
pasteurization with hot water at 76 °C for 3 min resulted in more than 5 log CFU/cm
2
reductions in
S. enterica
serovar Poona and
E. coli
populations (Table 13.2).
Cantaloupes that were surface pasteurized and stored at 4 °C for 21 days were fi rm
and had no visible mold growth; the control samples became soft and moldy. These
results indicated that the hot-water treatment enhanced the microbial safety of canta-
loupes and extended the shelf life of this commodity.
Fan and others (2008) compared the quality and shelf life of fresh-cut cantaloupe
prepared from hot - water - treated (76 ° C, 3 min) whole fruit with that prepared from
cold (10 ° C, 20 min) or chlorinated water (20 ppm, 10 ° C, 20 min). The quality and
microbial populations of fresh-cut cantaloupes prepared from whole fruit were also
analyzed after 1, 6, 8, 10, 13, 16 and 20 days of storage at 4 °C. Results showed that
the yeast and mold count on the rinds of whole fruits were reduced by 2.9 log CFU/
cm
2
(Table 13.2). However, the chlorine or cold-water washes did not result in signifi -
cant reductions in the microbial population. Although the hot-water treatment of whole
cantaloupe lowered the total plate count (TPC) on the rind, it did not reduce TPC on
fresh-cut cubes (Table 13.3) at day 1. However, in the subsequent storage periods (day
13 - 20), the fresh - cut fruit prepared from hot - water - treated cantaloupes were about
2 log CFU/g lower in TPC than that obtained from the other two treatments. This
observation was directly attributable to the lower counts and slower growth of bacteria
on the fresh-cut cantaloupes prepared from hot-water-treated samples during storage.
Soluble solids content, ascorbic acid content, fl uid loss, and aroma and appearance
scores were not consistently affected by either hot water or chlorine treatment. The
results suggested that hot-water pasteurization of whole cantaloupes resulted in a
longer shelf life of fresh-cut fruit without negatively effecting quality. A combination
of whole fruit surface sanitation by hot water (76 °C for 3 min) with low dose (0.5 kGy)
gamma irradiation of fresh-cut cantaloupes further reduced the microfl ora of cut fruit,
compared with either treatment alone (Fan and others 2006).
