Unpasteurized Fruit Juice Research Articles

Antimicrobial Activity of Essential Oils on Salmonella Enteritidis, Escherichia coli, and Listeria innocua in Fruit Juices

The antimicrobial properties of essential oils (EOs) and their derivatives have been known for years. However, the information published about the minimal effective concentration of EOs against microorganisms in fruit juices is scarce. In this study, both MIC and MBC of six EOs (lemongrass, cinnamon, geraniol, palmarosa, or benzaldehyde) against Salmonella Enteritidis, Escherichia coli, and Listeria innocua were determined by the agar and broth dilution methods, respectively. All of the six EOs inhibited the microbial (Salmonella Enteritidis, E. coli, and L. innocua) growth at a concentration from 1 μl/ml (MIC). These studies led to choosing the three most effective EOs. Lemongrass, cinnamon, and geraniol were found to be most effective in inhibiting the growth of the microorganisms and thus were used for the MBC analysis. On this last point, significant differences (P < 0.05) among EOs, their concentrations, and culture media (apple, pear, and melon juices, or tryptone soy broth medium) were found after comparing the results on MBC for each microorganism. A concentration of 2 μl/ml from lemongrass, cinnamon, or geraniol was enough to inactivate Salmonella Enteritidis, E. coli, and L. innocua in apple and pear juices. However, in melon juice and tryptone soy broth medium, concentrations of 8 and 10 μl/ml from cinnamon, respectively, or 6 μl/ml from geraniol were necessary to eliminate the three microorganisms, whereas lemongrass required only 5 μl/ml to inactivate them. These results suggest that EOs represent a good alternative to eliminate microorganisms that can be a hazard for the consumer in unpasteurized fruit juices. The present study contributes to the knowledge of MBC of EOs against pathogenic bacteria on fruit juices.

Mediterranean fruit fly as a potential vector of bacterial pathogens.

The Mediterranean fruit fly (Ceratitis capitata) is a cosmopolitan pest of hundreds of species of commercial and wild fruits. It is considered a major economic pest of commercial fruits in the world. Adult Mediterranean fruit flies feed on all sorts of protein sources, including animal excreta, in order to develop eggs. After reaching sexual maturity and copulating, female flies lay eggs in fruit by puncturing the skin with their ovipositors and injecting batches of eggs into the wounds. In view of the increase in food-borne illnesses associated with consumption of fresh produce and unpasteurized fruit juices, we investigated the potential of Mediterranean fruit fly to serve as a vector for transmission of human pathogens to fruits. Addition of green fluorescent protein (GFP)-tagged Escherichia coli to a Mediterranean fruit fly feeding solution resulted in a dose-dependent increase in the fly's bacterial load. Flies exposed to fecal material enriched with GFP-tagged E. coli were similarly contaminated and were capable of transmitting E. coli to intact apples in a cage model system. Washing contaminated apples with tap water did not eliminate the E. coli. Flies inoculated with E. coli harbored the bacteria for up to 7 days following contamination. Fluorescence microscopy demonstrated that the majority of fluorescent bacteria were confined along the pseudotrachea in the labelum edge of the fly proboscis. Wild flies captured at various geographic locations were found to carry coliforms, and in some cases presumptive identification of E. coli was made. These findings support the hypothesis that the common Mediterranean fruit fly is a potential vector of human pathogens to fruits.

Comparison of aqueous commercial cleaners for effectiveness in removing Escherichia coli O157:H7 and Salmonella muenchen from the surface of apples

Unpasteurized fruit juice and cider have been implicated in outbreaks of Escherichia coli O157:H7 and Salmonella infections, yet various processes used to clean and sanitize fruits before producing juice have not been thoroughly studied for their effectiveness in removing pathogens. The objective of this study was to evaluate cleaners used in the apple industry for their efficacy in removing E. coli O157:H7 and Salmonella from the surface of apples. E. coli O157:H7 was transformed with green fluorescent protein plasmid (pGFP). In addition to encoding for the production of GFP, the plasmid also encodes for ampicillin resistance. S. muenchen was adapted to grow in media containing 50 μg/ml nalidixic acid. The use of ampicillin and nalidixic acid resistant strains enabled enumeration of the pathogen without interference by microflora naturally present on apples. Unwaxed Red Delicious cv. apples were surface inoculated with 8.58 log 10 cfu of E. coli O157:H7 and 8.11 log 10 cfu of S. muenchen. Five commercial apple cleaners were applied at concentrations and exposure times recommended by manufacturers. Populations of E. coli O157:H7, S. muenchen, aerobic mesophiles, and yeasts and molds on apples treated with cleaners and water (control) were determined. Compared to washing with water, treatment with cleaners removed or killed up to 2.86, 3.11, 2.48, and 0.73 log 10 cfu of E. coli O157:H7, S. muenchen, aerobic mesophiles, and yeasts and molds per apple, respectively. There were differences in the effectiveness of cleaners in removing pathogens, but pH (2.0 and 12.0) and concentration (1% and 5%) of cleaner, and time of exposure (0.5–2 min) were not correlated with magnitude of reduction in population. The use of some types of cleaners commercially formulated for apples may contribute significantly in attaining target 5-log 10 reductions of pathogens on the fruit intended for unpasteurized juice production or the fresh produce market.

Effect of Low-Temperature, High-Pressure Treatment on the Survival of Escherichia coli O157:H7 and Salmonella in Unpasteurized Fruit Juices

The destructive effect of high pressure (615 MPa) combined with low temperature (15°C) on various strains of Escherichia coli O157:H7 and various serovars of Salmonella in grapefruit, orange, apple, and carrot juices was investigated. The three-strain cocktail of E. coli O157:H7 (SEA13B88, ATCC 43895, and 932) was found to be most sensitive in grapefruit juice (8.34-log reduction) and least in apple juice (0.41-log reductions) when pressurized at 615 MPa for 2 min at 15°C. Correspondingly, no injured survivor was detected in grapefruit and carrot juices under similar treatment conditions. No Salmonella spp. were detected in a 2-min pressure treatment (615 MPa, 15°C) of grapefruit and orange fruit juices. Except for Enteritidis, all four serovars tested in the present study have viability loss of between 3.92- and 5.07-log reductions when pressurized in apple juice at 615 MPa for 2 min at 15°C. No injured cells were recovered from grapefruit and orange juices, whereas the same treatment demonstrated reduction in numbers of Salmonella serovars Agona and Muenchen in apple juices and to a lesser extent with Typhimurium, Agona, and Muenchen in carrot juice. The present study demonstrated that low-temperature, high-pressure treatment has the potential to inactivate E. coli O157:H7 strains and different Salmonella spp. in different fruit juices.

Salmonellosis and Unpasteurized Orange Juice

Add salmonella to Escherichia coli O157:H7 and cryptosporidium as enteric pathogens associated with consuming unpasteurized acidic fruit juices such as