Comparison of Different Washing Treatments for Reducing Pathogens on Orange Surfaces and for Preventing the Transfer of Bacterial Pathogens to Fresh-Squeezed Orange Juice

Abstract

The objectives of this study were to compare the effectiveness of various washing treatments for reducing Escherichia coli O157:H7, Salmonella sp., and Listeria monocytogenes populations on orange surfaces and to measure the effect of some of these treatments in preventing the transfer of pathogens during juice extraction. Orange surfaces inoculated with L. monocytogenes or a mixture of E. coli O157:H7 and Salmonella Typhimurium were washed by water spray and then sprayed with or dipped in water at 80°C for 1 min, 70% ethanol for 15, 30, or 45 s or 1, 2, or 4 min, 2 or 4% lactic acid solution at 55°C for 15, 30, or 45 s or 1, 2, or 4 min, or 200 mg/liter hypochlorite at pH 6.5 or 10 for 15 s. The surviving populations of these pathogens on the oranges were enumerated after each treatment. In a further stage, the ability of these pathogens to be transferred to the juice during extraction was tested. Juice was obtained from inoculated oranges that were subjected to selected treatments using chlorine, lactic acid, ethanol, and hot water as described above, and then bacterial counts in orange juice were determined. The application of these treatments reduced the populations of pathogens on orange surfaces by 1.9 to >4.9 log, 1.9 to >4.6 log, and 1.4 to 3.1 log cycles for E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes, respectively. The treatments using hot water or lactic acid showed greater reductions than other treatments. The time, antimicrobial concentration, and form of application affected the bacterial reduction. All treatments resulted in undetectable counts in the juice. Nevertheless, pathogens were recovered by the enrichment-plating method. Treatment of oranges before juice extraction may reduce the risk associated with consuming orange juice.

Effect of the Use of a Neutralizing Step after Antimicrobial Application on Microbial Counts during Challenge Studies for Orange Disinfection

“…A recent study in our laboratory (14) showed that washing pathogen-inoculated oranges with hot water, lactic acid, ethanol, or chlorine resulted in reductions of 1.9 to >4.9 log CFU/cm2 for E. coli 0157:H7, 1.1 to >4.6 log CFU/cm2 for Salmonella Typhimurium, and 1.4 to 3.1 log CFU/cm2 for Listeria monocytogenes. In that study, oranges were allowed to drain for 15 min after treatment and then were sampled to measure the bacterial reduction as a result of antimicrobial application.…”

“…The oranges were then ah dried in a sanitized plastic basket for 15 min at room temperature before application of treatments. This method was previously tested to ensure complete drying of the orange surfaces (14).…”

Flow cytometry and growth‐based analysis of the effects of fruit sanitation on the physiology of Escherichia coli in orange juice

“…AC concentrations of 50–200 ppm with a contact time of 1–2 min are commonly used for washing fresh produce including oranges (Parish et al., ; Suslow, ). Consequently, numerous studies have investigated the effectiveness of AC for eliminating E. coli from the surface of orange fruits (Bagci & Temiz, ; Martinez‐Gonzales, Martinez‐Chavez, Martinez‐Cardenas, & Castillo, ; Pao & Davis, ; Pao, Davis, & Kelsey, ). However, these studies have only measured elimination of bacteria using plate counts; the physiological state of the bacteria has not been determined using nongrowth‐based methods.…”

Viable microbial loads on citrus carpoplane during packhouse processing and survival of foodborne pathogens in reconstituted postharvest fungicides

“…Citrus fruit are grown in natural, open environments and may come into contact with irrigation and postharvest processing water which are potential sources of microbial contamination (Martinez‐Gonzales, Martinez‐Chavez, Martinez‐Cardenas, & Castillo, ; Sela & Fallik, ). Hence, microbiota on fruit surfaces reflects the environmental biota where the produce is grown (Lindow & Brandl, ).…”

“…Although total viable counts (TVCs) are not directly related to public health, they indicate the overall viable microbial load on fruit surfaces and the exposure of fruit to potential sources of contamination and conditions conducive to multiplication of microorganisms (Goodrich‐Schneider, Danyluk, Ehsani, & Friedrich, ). Additionally, their natural association with agricultural environments and fresh produce in high numbers helps to quantitatively monitor the sanitation procedures and effectiveness of packhouse processes in cleaning and disinfecting fresh produce with some degree of accuracy (Keller et al, ; Martinez‐Gonzales et al, ).…”