Agriculture Reference
In-Depth Information
Green Onions
Cantwell and others (2001) studied the effects of heat treatment on quality and micro-
bial population of minimally processed green onions (leaf blades and stalks). They
found that hot - water treatment for 2 min at 55 ° C or 4 min at 52.5 ° C effectively con-
trolled postharvest leaf extension growth (a product defect) and reduced the microbial
population of green onions, while maintaining the visual quality of the leaves during
storage. Kim and others (2005) treated fresh-cut green onions (leaf blades) with warm
water (50°C for 20s) alone, and in combination with irradiation at 0, 0.5, 1.0 and
1.5 kGy. The treated green onions were stored at 4 °C for 14 days. The warm-water
treatment alone reduced the total plate count by 0.9 log CFU/g initially, but the benefi -
cial effect disappeared during storage. Signifi cantly higher scores of overall visual
quality and greenness and lower off-odor scores for irradiated samples were recorded
during sensory tests, regardless of the warm-water dip. With the test conditions used
in the study, the warm-water treatment did not provide added benefi ts for quality
improvement.
Sprouts and Watercress
Park and others (1998) reported reductions of microbial populations by 2.2 and
4.4 log CFU/g in soybean sprouts and watercress, respectively, after a 30 s hot-water
dip at 60 ° C.
In summary of the studies on vegetables, it is obvious that warm-water treatment
alone in the range of 45-50 °C reduced populations of
E. coli
O157 : H7 and
L. mono-
cytogenes
by only 2logCFU/g at the most, even when combined with chlorine.
Therefore, to achieve greater reductions of foodborne pathogens on produce, higher
temperatures are required. However, higher temperatures may cause tissue damage
(Loaiza-Velarde and others 1997; Fan and others 2003). Therefore, the sensitivity of
vegetables to heat injury prohibits the use of hot-water treatment to obtain dramatic
reductions in populations of foodborne pathogens on contaminated fresh-cut vegeta-
bles. Hot water in combination with other sanitizers (such as hydrogen peroxide) or
irradiation may achieve greater reductions of foodborne pathogens while maintaining
product quality.
Fruits
Cantaloupe
Pathogens, when present on the surface of whole fruits or vegetables, can be
transferred to the fresh-cut produce during processing (cutting, peeling, etc.).
Melons (mostly cantaloupes) are one of the groups of produce that are most frequently
associated with outbreaks and contamination with foodborne pathogens (Fan
and others 2006, 2008). The high rates of pathogen contamination associated
with melons highlight the need for effective interventions for both whole and cut
melons.
Lamikanra and others (2005) immersed whole cantaloupes into 50°C water for
60 min before being processed into cubes. Sensory evaluations indicated that the heat
treatment increased intensities of desirable attributes, such as fruity melon and sweet
aromatic fl avors, and reduced undesirable fl avors such as musty, sour, bitter, chemical,
and fermented fl avors. The treatment also reduced the initial total microbial count and
