Effect of Chlorine, Blanching, Freezing, and Microwave Heating on Cryptosporidium parvum Viability Inoculated on Green Peppers

Abstract

<jats:p>Cryptosporidium parvum oocysts have been found on the surface of vegetables in both developed and developing countries. C. parvum can contaminate vegetables via various routes, including irrigation water. This study investigated the effect of individual treatments of chlorine, blanching, blast freezing, and microwave heating, as well as combined treatments of chlorine and freezing, and chlorine and microwave heating on the viability of C. parvum oocysts inoculated on green peppers. The viability of the oocysts after the treatments was assessed using propidium iodide and a flow cytometer. Based on the propidium iodide staining, the chlorine treatments did not affect the viability of the oocysts. Blast freezing significantly inactivated 20% of the oocysts. Microwave heating and blanching significantly inactivated 93% of oocysts. Treatment with chlorine followed by blast freezing did not affect the viability of the oocysts significantly. Treatment with chlorine and microwave heating was significantly more effective than microwave heating alone and inactivated 98% of the oocysts. The study indicates that C. parvum oocysts are sensitive to heat and, to some extent, to blast freezing, but are resistant to chlorine. Therefore, the use of chlorine during vegetable processing is not a critical control point for C. parvum oocysts, and the consumption of raw or minimally processed vegetables may constitute a health risk as C. parvum oocysts can still be found viable on ready-to-eat, minimally processed vegetables.</jats:p>

Physicochemical Quality and Chemical Safety of Chlorine as a Reconditioning Agent and Wash Water Disinfectant for Fresh-Cut Lettuce Washing

“…Protozoan parasites, such as Cryptosporidium parvum and Cyclospora cayetanensis, have also been associated with outbreaks related to fresh produce consumption, and countries in Latin America have recognized them as pathogens of concern (4,67,70,71). If produce wash water should be kept free of these pathogens, a chlorination system would fail due to the high level of resistance to chlorine (72,73), or alternatively, excessively Van Haute et al high free chlorine concentrations would be required. Ozone (74), UV (75), and, especially for avoiding cross-contamination in washing processes, the more stable chlorine dioxide (6,32,76,77) are better alternatives to chlorine for inactivation of protozoan parasites.…”

A Perspective on Cryptosporidium and Giardia, with an Emphasis on Bovines and Recent Epidemiological Findings

“…An investigation of the efficacy of different treatments used in food processing (i.e. chlorine, blanching, blast freezing and microwave heating) on the viability of C. parvum has showed that oocysts can be destroyed by heat and, to some extent, by freezing, but not by safe concentrations of chlorine (Duhain et al, 2012). Usually, Giardia cysts are more susceptible to chlorine disinfection than Cryptosporidium oocysts (Sterling, 1990).…”

The effects of microwave radiation on microbial cultures

“…When microwaves are applied at certain frequencies, with high energy and for a sufficiently long period of time, their thermal effect is most likely dominant and kills bacterial cells or yeasts. Numerous experiments with microwave irradiation of various cultures of bacteria and yeasts in a wet environment such as a water suspension did not show additional killing of the microbes by microwaves compared to that caused by conventional heating to the same temperature [8,9,10]. However, in a dry environment, the killing effect of microwave radiation was significantly decreased and happened only after a prolonged period of irradiation, most likely due to a lower transformation of microwave energy to heat.…”