Fresh fruits and vegetables are prone to microbial contamination throughout different phases of human handling, processing, transportation,... Show moreFresh fruits and vegetables are prone to microbial contamination throughout different phases of human handling, processing, transportation, and distribution.
Emerging technologies, such as power ultrasound, have received attention due to their
capacity to reduce or eliminate foodborne bacterial pathogens on these commodities.
Power ultrasound, when combined with certain antimicrobials, has demonstrated its
effectiveness as a valuable tool for washing fresh produce. The objective of this study
was to examine the effectiveness of power ultrasound combined with organic acids on the
reduction of Listeria monocytogenes on fruits. In this study, peaches and apples were
subjected to surface inoculation with a four-strain cocktail of L. monocytogenes and dried
for 1 h. Stomacher bags, containing 225 mL of citric, lactic, or malic acids at
concentrations of 1%, 2%, or 5%, were employed for treating inoculated peaches and
apples. The acid treatment was used alone, or in combination with power ultrasound for
2, 5, or 10 min. Water was used for controls. Before treatment, the initial population of L.
monocytogenes on apples was lower compared to the initial population on peaches, with
apples showing a 1.94 log CFU/fruit reduction. Water controls demonstrated no
significant log reduction in both apples and peaches. The greatest L. monocytogenes
reduction on apples occurred when treated with 1% citric acid for 2 min with power
ultrasound where L. monocytogenes was significantly reduced from 6.98±0.88 log
CFU/fruit to 5.56±0.91 log CFU/fruit. The greatest L. monocytogenes reduction on
peaches occurred when treated with 5% citric acid for 5 min with power ultrasound
where L. monocytogenes was significantly reduced from 7.44±0.45 log CFU/fruit to
6.68±0.40 log CFU/fruit.
Overall, the combined effect of acid and power ultrasound was more pronounced
in apples than in peaches. The survival of L. monocytogenes on apples and peaches
appeared to be highly dependent on the specific treatment and hurdle technology applied.
The combination of ultrasound hurdle technology with acid washing has proven effective
in reducing L. monocytogenes on both peaches and apples, with a more significant impact
observed on apples. While acid washing is a more economical option compared to
ultrasound technology, the efficiency of microorganism reduction is considerably
enhanced when power ultrasound is combined with organic acids. Looking ahead, the
development of cost-effective power ultrasound methods could facilitate widespread
adoption of ultrasound hurdle technology in the produce industry. Show less