Skip to main content
NCBI home page
Iranian Journal of Public Health logoLink to Iranian Journal of Public Health
. 2012 Mar 31;41(3):95–103.

Evaluating the Efficiency of Lettuce Disinfection According to the Official Protocol in Iran

M Yarahmadi 1, M Yunesian 2, MR Pourmand 3, A Shahsavani 2, I Mubedi 4, B Nomanpour 5, K Naddafi 2,*
PMCID: PMC3481702  PMID: 23113153

Abstract

Background

The objective of this study was to evaluate the efficacy of Sanitization of Lettuce according to the protocols set forth by Iranian Ministry of Health and Medical Education for reducing populations of total coliform, fecal coliform, and helminth eggs present on lettuce.

Methods:

In the present study, we determined the load of total coliform, fecal coliform, and parasites of lettuce. The lettuce was sanitized by protocol of Iranian Ministry of Health and Medical Education. The protocol consists of 3 levels to disinfect the fruits and vegetables. The procedure was as follows: first washing stage. The leaves of leafy vegetables washed with tap water, second stage, separation of helminth eggs by 3 to 5 droplets of detergent per liter for 5 min; third stage, disinfection of vegetables by calcium hypochlorite solution (with 200 mg/l free chlorine) for 5 min; and finally the disinfected vegetables were washed with tap water.

Results:

The average initial levels of total coliform and fecal coliform in the samples were 3.36 log10 cfu/g and 2.31 log10 cfu/g, respectively. Helminth eggs were not detected in any of the samples tested. The efficiency of total coliform and fecal coliform removal were 78.1% (0.75 log10cfu/g) and 79.6% (0.67 log10cfu/g), respectively, after washing. This increased up to 94.8(1.44 log10cfu/g) and 98.5% (1.90 log10cfu/g) after the use of detergent. Chlorine disinfection rose these amounts up to 98.3% (2.18 log10cfu/g) and 100% (2.31 log10cfu/g), respectively.

Conclusion:

By applying the protocol large parts of microorganisms existing on lettuce have indeed been removed.

Keywords: Raw vegetable, Disinfection, Fecal coliform, Total coliform

Introduction

Fruits and vegetables are known to be rich in nutrients and considered as an important part of people’s daily diet (1). Although raw-eaten fruits and vegetables have a primary role in the diet, they can cause food-borne diseases if they are contaminated (2–4). Listeria monocytogenes, Salmonella (5), and Escherichia coli are among the pathogens that have been observed on vegetables (4,6), Research indicates that food-born diseases have significantly increased during the recent years, due mainly to the consumption of raw-eaten fruits and vegetables (2,6). Studies have shown the occurrence of 22 outbreaks in the United States between 1995 and 2006, half of which has been attributed to the consumption of contaminated vegetables such as spinage. According to these studies, tomato, lettuce, sprouts, and spinage are the most important causes of food-born diseases in the United States (7). The American Food and Drug Administration have reported that there are serious concerns about the consumption of vegetables, especially leafy vegetables such as lettuce (8). Vegetables can be contaminated in various ways; for example, at the time of harvest, transport, distribution, sale, and even during the food preparation processes at home or restaurants (9). The main causes of the contamination of the vegetables are application of human or animal fertilizers and the use of wastewater effluent for irrigation purposes (10). It has been estimated, according to the studies conducted in 2006, that raw wastewater, unfinished, or finished wastewater are used in more than 20 million acres of the agricultural lands around the world (11). Preventing the contamination of fruits and vegetables should be set as an important objective during production, transport, and delivery. However, some pathogens are natural flora of the soil and may exist on vegetables even at the time of harvest (3).Rinsing the vegetables with clean water is a simple, but effective way in the disinfection of vegetables with low pathogens load. However, the application of an effective disinfectant is essential in case of high microbial load (12). Rinsing vegetables with clean water decreases the microbial load only by 1 log10 CFU/g (4,13). In a study conducted by Singh et al., it was found that one and several times of water rinse can reduce the load of Escherichia coli on lettuce by 0.22 log10 CFU/g and 1 log10 CFU/g, respectively (14). Several studies have been conducted around the world to assess the efficacy of different disinfectant for vegetables disinfection (15–17). However, no studies have yet been conducted in Iran in this filed. Some of the most commonly used disinfectants are calcium hypochlorite, sodium hypochlorite (NaClO), and electrolyzed water with pH of 4–5 (18). A variety of disinfection methods are in use around the world depending mainly on the contamination load and the processes used for the production of the vegetables. Chlorinated water is used by some countries for disinfection of the vegetables after of harvest, transport, and processing (19). The most commonly used method for the disinfection of vegetables in Brazil is the application of sodium hypochlorite solution with a concentration of 200 mg/l for 15 min (20). Result of the study conducted by Garcia-Gomez et al., in Mexico indicated that approximately 30% of the studied population use a disinfectant containing colloidal silver for disinfection of vegetables; 28% use water rinse, 25% apply sodium hypochlorite, and the rest of the population use a variety of other disinfectants such as salt, detergent, salt combined with lemon, and finally iodine combined with detergent and lemon (21). In some countries, such as US, the vegetables are only rinsed with clean water and the use of any kind of disinfectant is not suggested (22). In Iran, in the recent years, the prevalence of food-born diseases, such as gastrointestinal complications, has increased due mainly to the consumption of contaminated vegetables. According to the study of Rahbar et al. in 2006, the consumption of contaminated vegetables irrigated by wastewater effluents was found to be the main cause of cholera (23). In another study conducted in Markazi and Golestan provinces, improper disinfection of vegetables was found to be the major cause of cholera in those provinces (24). Results of another study conducted in Karaj indicated the same cause for the prevalence of cholera in this city (25).

Iranian Ministry of Health and Medical Education has developed a method for the disinfection of raw-eaten fruits and vegetables. The procedure is as follows: first washing stage, the leaves of leafy vegetables were separated and washed with tap water. Thus, mud and dust of these vegetables were removed; second stage, separation of helminth eggs by 3 to 5 droplets of detergent per liter for 5 min, third stage, disinfection of vegetables by calcium hypochlorite solution (with 200 mg/l free chlorine) for 5 min; and finally the disinfected vegetables were washed with tap water (26). The main objective of the present study was to assess the efficacy of the disinfection method proposed by the Iranian Ministry of Health and Medical Education for decreasing the contamination load on lettuce.

Materials & Methods

Fresh lettuce was purchased from a wholesale market of fruits and vegetables in Tehran, Iran. Having transferred to the laboratory, lettuce was kept in 7 °C and all of the experiments were performed within the same day. 200gr samples of lettuce leaves were provided. From this sample, 50 g of lettuce was transferred to a Ziploc bag containing 250 ml 0/1% peptone water with a pH of 7.2 (PW, Merck). The bags containing lettuce leaves and PW were orbitally agitated by a shaker at 150 rpm for 2 min. Dilution series were prepared from the solution and the population of total coliforms and fecal coliforms were determined by MPN test (27, 28). In order to determine the efficacy of water rinse of lettuce in decreasing the microbial load, 50 gr of the lettuce was put in a sterile bag containing peptone water. Afterwards, dilution series were prepared and the population of total coliforms and fecal coliforms were determined by MPN test (27, 28).

The efficacy of detergent in decreasing the microbial levels present on lettuce surfaces showed that on the remaining 100 gr of sample from the previous level submerged in 1 liter of water that contained approximately 3 drops of detergent for approximately 5 minutes. Then, the lettuce sample was washed with water, and 50 grams of which was separated. Again, it was proved that total coliforms and fecal coliforms exist on the surface of the lettuce. Finally, the remaining 50-gr-lettuce sample was immersed in one liter of calcium hypochlorite solution (200 ppm free chlorine with 700 g/kg available chlorine) for approximately 5 minutes at the end of the contact time. Then, treatment solution was drained off and the treated lettuce was rinsed. Total coliforms and fecal coliforms were then determined by MPN test. calcium hypochlorite solution was prepared by adding calcium hypochlorite (700 g/kg available chlorine) to deionized water. The concentrations of free chlorine were measured using a Hach DR: 2000 meter. Finally, results were reported as CFU/g (27,29,30).

The second step of this study was to assess the efficacy of the disinfection method proposed by the Iranian Ministry of Health and Medical Education in terms of decreasing helminth eggs from lettuce surfaces. In the present study, flotation method was used to determine the helminth eggs load of the lettuce. For this purpose the vegetable samples from wholesalers were brought, they were transported to the laboratory for analysis in nylon bags.

Portion of vegetables was weighted (250 g) and the sample was placed into a beaker, containing a 1.5–l detergent solution. The samples were then completely mixed and kept for approximately 30 min. Afterwards, the lettuce samples were gathered from the beaker and discarded. The water used for washing purposes was filtrated in order to remove all the remaining dirt, filth, and small debris that may have remained in the sample. Then, the container containing the wash water was stored for approximately two hours until helminth eggs layers, and sediments were precipitated. Then, the resulting eggs was transferred to a beaker. This process was repeated for several times in order to ensure the full precipitation. After that, 50 mL of the bottom liquid was transferred to centrifugation tubes and centrifuged for for 3 min at 2000g The sediment was examined at 10× magnification under a light microscope for helminth egg content. The eggs were identified at 40× magnification. (31,32). The experiments were repeated for three times in order to determine their precision and the accuracy.

Results

Results of the present study regarding the initial microbial and parasitological loads of the lettuce as well as the efficacy of the method proposed by the Iranian Ministry of Health and Medical Education are presented in Tables. According to table 1, the initial loads of total coliforms and fecal coliforms on the lettuce were 3.36 log10 CFU/g and 2.31 log10 CFU/g, respectively. The initial load of total coliform was higher than that of fecal coliform. However, no helminth eggs were observed in any of the samples. Table 2 presents the loads of total coliforms and fecal coliforms after the disinfection according to the proposed method. The loads of total coliforms and fecal coliforms after disinfection by this method were 2.18 log10 CFU/g, and 2.31 log10 CFU/g, respectively.

Table 1:

Initial contamination of lettuce samples purchased from a wholesale market of fruit and vegetable in Tehran, Iran 1n 2010

Sample (Total coliform) CFU/g log10 (Fecal coliform) CFU/g log10 Parasite
1 3.34 2.40 0
2 3.40 2.83 0
3 3.20 2.14 0
4 3.38 1.89 0
5 3.50 2.30 0
Average 3.36 2.31 0
Open in a new tab

Table 2:

Reduction of total coliforms and fecal coliform populations on lettuce by the method of disinfection that proposed by the Iranian Ministry of Health and Medical Education

Total coliform (Log10 CFU/g) Fecal coliform (log10 CFU/g)
Treatment Population recovered (mean + SD) Reduction Population recovered (mean + SD) Reduction Parasite
Control 3.36±0.10 2.31±0.34 0
Water 2.61±0.2 0.75 1.63±0.17 0.67 0
Detergent 1.89±0.47 1.44 0.41 ± 0.58 1.90 0
calcium hypochlorite (200 ppm,5min) 1.88±0.10 2.18 0 2.31 0
Open in a new tab
1-

Means and standard deviations represent five samples per experiment

2-

Values with different letters for total coliform are significantly different (P=0.007)

3-

Values with different letters for fecal coliform are significantly different (P=0.015)

The removal efficiency of total coliforms and fecal coliforms by the method proposed by the Iranian Ministry of Health and Medical Education is presented in Table 3. As given in this table, the removal efficiency of the method is as follows: 78.1% (0.75 log10 CFU/g) and 79.6% (0.67 log10 CFU/g) for total coliforms and fecal coliforms at the first stage of the method (washing stage); 94.8% (1.44 log10 CFU/g) and 98.5% (1.9 log10 CFU/g) for total coliforms and fecal coliforms at the second stage (use of detergent); 98.3%(2.18 log10 CFU/g) and 100% (2.34 log10 CFU/g) for total coliforms and fecal coliforms at the final stage(disinfection). Significant differences were observed between the efficacies of the method in different stages (P=0.007, P=0.015) implying the effectivness of the method.

Table 3:

Efficiency of the removal of total coliforms and fecal coliforms by the method of disinfection that proposed by the Iranian Ministry of Health and Medical Education

Treatment Total coliform (%) Fecal coliform (%)
Water 78.1 79.6
Detergent 94.85 98.5
Calcium hypochlorite (200ppm/L,5min) 98.3 100
Open in a new tab

Discussion

No studies have yet been conducted in Iran in order to determine the microbial load of vegetables, though a number of studies have been carried at in different countries. It is noteworthy that the initial microbial load of vegetables is different in different countries, due mainly to the different condition of harvest, transport, distribution, and finally delivery to the costumer. In a study performed by Nascimento et al., in 2003 in Brazil, initial loads of total coliforms and Escherichia coli were evaluated on 10 lettuce samples. Results indicated that the initial loads were 3.25 log10 CFU/g and 1.64 log10 CFU/g, respectively, which is in agreement with those presented by the present study (20). Studies indicate that the population of microorganisms on vegetables can vary significantly (33, 35). The microbial load of vegetables is not always representative of the use of wastewater effluents or human fertilizers, because some of the microorganisms are considered as the natural microflora of the soil and exist on the vegetables at the time of harvest. In addition, presence of fecal coliforms is not always indicator of fecal contamination since this bacterium is the natural microflora of the plants (34–36).

However, the presence of Escherichia coli is undoubtedly representative of irrigation by wastewater effluents or use of human fertilizers (37). No helminth eggs was observed in any of the samples, indicating the lettuce was not irrigated by raw waste water. In a study conducted by Homayuni et al. in 2007 in Tehran, 270 vegetable samples were studied and it was found that 41.3% of the samples had different types of helminth eggs contamination (38). In another study conducted by Davami in 2000, 120 samples of raw-eaten vegetables were evaluated; in this case, 68.3% of the samples had a variety of helminth eggs contamination (39). Similar study in Bushehr indicated the contamination of 12.5% of the samples (40). These finding are not consistent with those observed by the present study. This can be attributed to our smaller sample size, different types of methodologies applied, and the currently more advanced methods of production of vegetables compared to the traditional methods used in the past. At the first stage (water wash of lettuce) of the present study, total coliforms and fecal coliforms decreased by 0.75 log10 CFU/g and 0.67 log10 CFU/g, respectively. Results of the study of Nascimento indicated decreases in aerobic bacteria, yeasts, fungi, and total coliforms of 0.78, 0.87 and 0.82, respectively. In another study carried out by Frank et al. in 1999, it was found that water wash can decrease the microbial load of vegetables by 1 log10 CFU/g (41). In the study of Barak et al, in US, a 1 log10 CFU/g decrease was observed in the population of Salmonella induced on cantaloupe by water rinse. The second stage (use of detergent) decreased total coliforms and fecal coliforms by 1.44 log10 CFU/g and 1.9 log10 CFU/g, respectively.

Results of the study of Barak et al. indicated a 1 log10 CFU/g decrease in Salmonella population by detergent. Detergent facilitates the separation of helminth egg from the vegetables; in addition, it decreases the water phobia characteristics of the vegetables, increasing the effectiveness of disinfection due to improved contact between the disinfectant and the pathogens (42). Total coliforms and fecal coliforms decreased by 2.18 log10 CFU/g and 2.31 log10 CFU/g, respectively, at the third stage (use of disinfectant). Results of the study of Zhang et al. indicates 1.3–1.7 log10 CFU/g and 0.9–1.2 log10 CFU/g decreases in the population of Salmonella on the lettuce and cabbage using chlorine (with a concentration 200 mg/l) as the disinfectant (43). A concentration of 150 mg/l chlorine decreased the population of Salmonella by 1 log10 CFU/g. Overall, the method proposed by the Iranian Ministry of Health and Medical Education.and Medical Education.decreased the total coliforms and fecal coliforms by 98.3% (2.18 log10 CFU/g) and 100% (2.31 log10 CFU/g), respectively. Results of Barak et al. indicated a 3 log10 CFU/g decrease in the population of Salmonella induced on cantaloupe by using a combination of water wash, detergent, and chlorine (150 mg/l) (44). The study conducted in Brazil indicates that the common method in that country (vegetable disinfection by 200 mg/l chlorine for 15 min) can decrease total aerobic bacteria by 2.63 log10 CFU/g, yeasts and fungi by 2.78 log10 CFU/g, and total coliforms by 1.96 log10 CFU/g (20). In another study performed in Mexico it was found that the disinfectant containing colloidal silver can decrease the population of total aerobic bacteria and fecal coliforms on lettuce by 52% and 99.4 %,, respectively. Corresponding values for coriander are 28.6% and 98.6 %, respectively. However, this disinfectant did not remove Salmonella typhi existing on the vegetables. It was suggested in the study that chlorinated water can be used as an effective alternative for the mentioned disinfectant (21). Removal efficiency of disinfectants depend primarily on the type of product, type of the fruits and vegetables surface, and the type of the microorganism that is to be removed, resulting in a broad range of results (12).

According to the results from the present study, it can be concluded that although the disinfection method proposed by the Iranian Ministry of Health and Medical Educationcan effectively remove the organisms present on vegetables, chlorine can react with the organic matters of fruits and vegetables and produce toxic compounds such as THMs (14,45,46). Instead of disinfection by chemical compounds, applying appropriate control measures at the time of harvest, transport, distribution, and delivery according to the HACCP can surely decrease the contamination load of fruits and vegetables and decline the prevalence of food-born diseases linked to them. For this purpose, all people involved in the production and sale of such products should be well trained. It is also noteworthy that further studies have to be conducted to evaluate the effectiveness of different methods of disinfection.

Ethical considerations

Ethical issues (Including plagiarism, Informed Consent, misconduct, data fabrication and/or fal-sification, double publication and/or submission, redundancy, etc) have been completely observed by the authors.

Acknowledgments

This work was part of an M.Sc thesis funded by Tehran University of Medical Sciences. We wish to thank the Department of Environmental Health Engineering because of cooperation in this work. All of the experiments were conducted at the microbial laboratory of Department of Environmental Health Engineering, School of Public Health. The authors declare that there is no conflict of interests.

References

  • 1.Dimitri C, Tegene A, Kaufman PR. U.S Fresh Produce Markets: Marketing Channels, Trade Practices, and Retail Pricing Behavior. 2003 Report. Report No: 825. [Google Scholar]
  • 2.Allende A, McEvoy J, Tao Y, Luo Y. Antimicrobial Effect of Acidified Sodium Chlorite, Sodium Chlorite, Sodium Hypochlorite, and Citric Acid on Escherichia coli O157:H7 and Natural Microflora of Fresh-Cut Cilantro. Food Cont. 2009;20:230–234. [Google Scholar]
  • 3.Beuchat LR, Ryu JH. Produce Handling and Processing Practices. Emerg Infect Dis. 1997;(3):459–465. doi: 10.3201/eid0304.970407. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Nguyen-The C, Carlin F. The microbiology of Minimally Processed Fresh Fruits and Vegetables. Food Sci Nutri. 1994;34:371–401. doi: 10.1080/10408399409527668. [DOI] [PubMed] [Google Scholar]
  • 5.Johannessen GS, Loncarevic S, Kruse H. Bacteriological Analysis of Fresh Produce in Norway. Int J Food Microbiol. 2002;7:199–204. doi: 10.1016/s0168-1605(02)00051-x. [DOI] [PubMed] [Google Scholar]
  • 6.Abadias M, Usall J, Anguera M, Solsona C, Vinas I. Microbiological Quality of Fresh, Minimally-Pprocessed Fruit and Vegetables and Sprouts from Retail Establishments. Int J Food Microbiol. 2008;123:121–129. doi: 10.1016/j.ijfoodmicro.2007.12.013. [DOI] [PubMed] [Google Scholar]
  • 7.Elano RS, Kitagawa T, Bari ML, Kawasaki S, Kawamoto S, Inats Y. Comparison of the Effectiveness of Acidified Sodium Chlorite and Sodium Hypochlorite in Reducing Escherichia coli. Food borne Pathog Dis. 2010;7:1481–1489. doi: 10.1089/fpd.2010.0595. [DOI] [PubMed] [Google Scholar]
  • 8.Food and Drug Administration. Fresh Leafy Greens Grown in the United States are Safe. 2006. http://www.fda.gov/fdac/features/606_greens.html. Accessed 14.02.08.
  • 9.Beuchat LR. Surface disinfection of Raw Produce. Dairy Food Environ Sanit. 1992;12:6–9. [Google Scholar]
  • 10.Beuchat LR. Pathogenic Microorganisms Associated with Fresh produce. J Food Prot. 1996;59:204–216. doi: 10.4315/0362-028X-59.2.204. [DOI] [PubMed] [Google Scholar]
  • 11.Hamilton JA, Stagnitti F, Premier R. All Rights Reserved.Quantitative Microbial Risk Assessment Models for Consumption of Raw Vegetables Irrigated with Reclaimed Water. Appl. Environ. Microbiol. 2006;72(5):3284–3290. doi: 10.1128/AEM.72.5.3284-3290.2006. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Beuchat LR. Surface Decontamination of Fruits and Vegetables Eaten Raw: a review Food Safety Issues, Food Safety Unit. World Health Organization; Geneva: 1998. WHO/FSF/FOS/98.2. [Google Scholar]
  • 13.Adams HR, Hartley AD, Cox LJ. Factors Affecting the Efficiency of Washing Procedures Used in Production of Prepared Salads. Food Microbial. 1989;6:69–77. [Google Scholar]
  • 14.Singh N, Singh RK, Bhunia AK, Stroshine RL. Efficacy of Chlorine Dioxide, Ozone & Thyme Essential Oil or a Sequential Washing in Killing E. coli O157:H7 on Lettuce and Baby Carrots. Lebensm-Wiss u-Technologie. 2002;35:720–729. [Google Scholar]
  • 15.Baert L, Vandekinderen I, Devlieghere F, Van Coillie E, Debevere J, Uyttendaele M. Efficacy of Sodium Hypochlorite and Pperoxyacetic Acid to Reduce Murine Norovirus 1, B40-8, Listeria monocytogenes, and Escherichia coli O157:H7 on Shreddediceberg Lettuce and in Residual Wash Water. J Food Prot. 2009;72:1047–1054. doi: 10.4315/0362-028x-72.5.1047. [DOI] [PubMed] [Google Scholar]
  • 16.López-Gálvez F, Allende A, Selma MV, Gil MI. Prevention of Escherichia Coli Cross-Contamination by Different Commercial Sanitizers During Washing of Fresh-cut Lettuce. Int J Food Microbiol. 2009;133:167–171. doi: 10.1016/j.ijfoodmicro.2009.05.017. [DOI] [PubMed] [Google Scholar]
  • 17.López-Gálvez F, Gil MI, Truchado P, Selma MV, Allende A. Cross-Contamination of Fresh-cut Lettuce after a Short-term Exposure During Pre-Washing Cannot be Controlled after Subsequent Washing with Chlorine Ddioxide or Sodium Hypochlorite. Food Microbiol. 2010;27:199–204. doi: 10.1016/j.fm.2009.09.009. [DOI] [PubMed] [Google Scholar]
  • 18.Hricova D, Stephan R, Zweifel C. Electrolyzed Water and its Application in the Food Industry. J Food Prot. 2008;71:1934–1947. doi: 10.4315/0362-028x-71.9.1934. [DOI] [PubMed] [Google Scholar]
  • 19.Weissinger WR, Chantarapanont W, Beuchat LR. Survival and growth of Salmonella baildon in Shredded Lettuce and diced Tomatoes, and Eeffectiveness of Chlorinated Water as a Sanitizer. Int J Food Microbiol. 2000;62:123–131. doi: 10.1016/s0168-1605(00)00415-3. [DOI] [PubMed] [Google Scholar]
  • 20.Nascimento MS, Catanozi M, Silva KC. Effects of Different Disinfection Treatments on the Natural Microbiota of Lettuce. J Food Prot. 2003;66(9):1697–1700. doi: 10.4315/0362-028x-66.9.1697. [DOI] [PubMed] [Google Scholar]
  • 21.García-Gómez R, Chávez-Espinosa J, Mejía-Chávez A, Duránde-Bazúa C. Microbiological Determinations of some Vegetables from the Xochimilco zone in Mexico City, Mexic. Rev Latinoam Microbiol. 2002;44(1):24–30. [PubMed] [Google Scholar]
  • 22.Food and Drug Administration (FDA) Safe Handling of Raw Produce and Fresh-Squeezed Fruit and Vegetable Juices. 2009 www.cfsan.fda.gov. Accessed 28.8.11. [Google Scholar]
  • 23.Rahbar M, Sabourian R, Saremi M, Abbasi M, Masoomi A, Soroush M. Epidemiological and Drug Resistant Pattern of Summer of 2005 Outbrak In Iran. JAUMS. 2007;7:41–5. (Persian) [Google Scholar]
  • 24.Khodabakhshi B, Heidari M, Fazeli MR, Ghaemi E, Karimi MS. Epidemiological Study of Clinical and Paraclinical Manifestation of Cholera Patients and Report of Uncommon Manifestation of During the Epidemic Episode in Ggorgan. 1998. JMS. 2003;3:43–46. (Persian) [Google Scholar]
  • 25.Barati HA, Golmohammadi A, Momeni I, Moradi G. A Cholera Outbreak Investigation in Karaj District in 2008. I J E. 2010;6(3):28–34. (Persian) [Google Scholar]
  • 26.Ministry of Health and medical education of IRAN. Guidline to disinfection vegetable. 2010 www.behdasht.gov.ir. Accessed.2010[persian]. [Google Scholar]
  • 27.Eaton AD, Clesceri LS, Greenberg AE. Standard Methods for the Examination of Water and Wastewater. 20 ed. APHA, AWWA, WEF; Washington, D.C: 2005. [Google Scholar]
  • 28.Gay MJ. Modern Food Microbiology. 16 ed. Gaithersburg: Aspen; 2000. pp. 91–126. [Google Scholar]
  • 29.Roberts D. Practical Food Microbiology. 3rd ed. Black well Publishing; 2003. pp. 25–131. [Google Scholar]
  • 30.Ray B. Fundamental Food Microbiology. 3rd ed. New York: CRC Press; 2005. pp. 439–491. [Google Scholar]
  • 31.Cook N, Paton CA. Towards Standard Methods for the Detection of Cryptosporidium Parvum on Lettuce and Raspberries and Raspberries. Part 1: Development and Optimization of Methods. Food Microbiol. 2006;109:215–219. doi: 10.1016/j.ijfoodmicro.2005.12.015. [DOI] [PubMed] [Google Scholar]
  • 32.Robertson LJ, Ggerde B. Isolation and Enumeration of Giardia Cysts, Cryptosporidium Oocysts, and Ascaris Eggs Front Fruits and Vegetables. J Food Prot. 2000;63:775–788. doi: 10.4315/0362-028x-63.6.775. [DOI] [PubMed] [Google Scholar]
  • 33.Brackett RE, Splittstoesser DF. Compendium of Methods for the Microbiological Examination of Foods. 4th ed. American Public Health Association; Washington, D.C: 2001. pp. 515–520. [Google Scholar]
  • 34.Karapinar M, Gonul SA. Removal of Yersinia Enterocolitica from Fresh Parsley by Washing with Acetic Acid or Vinegar. Int J Food Microbiol. 1992;16:261–4. doi: 10.1016/0168-1605(92)90086-i. [DOI] [PubMed] [Google Scholar]
  • 35.Riser EC, Grabowski J, Glenn EP. Microbiology of Hydroponically-grown Lettuce. j Food Prot. 1984;(47):765–9. doi: 10.4315/0362-028X-47.10.765. [DOI] [PubMed] [Google Scholar]
  • 36.Splittstoesser DF. Predominant Microrganisms on Raw Plant Foods. Journal of Milk Food Technology. J Milk Food Technol. 1970;33:500–510. [Google Scholar]
  • 37.Geldreich EE, Bordner RH. Fecal Contamination of Fruits and Vegetables During Cultivation and Processing for Market. J Milk Food Technol. 1971;34:184–195. [Google Scholar]
  • 38.Homayouni M, Khalagi N. Parasitic Infection of Consumed Vegetable in Tehran. AUMS. 2007;4(4):1053–1063. (Persian) [Google Scholar]
  • 39.Davami M, Mosayyebi M, Mahdavipour A. Prevalence of Parasitic Infections in Consumed Vegetables in Ardabil City. J RAD. 2000;3(2):18–22. (Persian) [Google Scholar]
  • 40.Sahebani N, Fouladvand M, Dalimi A. Parasitic Infections of Consumed Vegetables in Boushehr City. J Tebbe Jonoub. 1999;2(1):59–63. (Persian) [Google Scholar]
  • 41.Frank JF, Takeushi K. Direct Observation of E. Coli O157:H7 Inactivation on Lettuce Leaf Using Confocal Scanning Laser Microscopy. In: Elmadfa i, König J., editors. Proceedings of the International Conference of International Committee on Food Microbiology and Hygiene. S. Karger Medical and Scienti. C Publishers; Vienna, Austria. 1999. pp. 795–797. [Google Scholar]
  • 42.Keskinen LA, Annous BA. Efficacy of Adding Detergents to Sanitizer Solutions for Inactivation of Escherichia Coli O157:H7 on Romaine Lettuce. Int J Food Microbiol. 2011;147:157–161. doi: 10.1016/j.ijfoodmicro.2011.04.002. [DOI] [PubMed] [Google Scholar]
  • 43.Zhang S, Farber JM. The Effects of Various Disinfectants A gainst Listeria monocytogenes on Fresh-cut vegetables. Food Microbiol. 1996;13:311–321. [Google Scholar]
  • 44.Barak JD, Chue B, Mills DC. Recovery of Bacteria Following Surface Sanitization of Cantaloupes. J Food Prot. 2003;66(10):1805–1810. doi: 10.4315/0362-028x-66.10.1805. [DOI] [PubMed] [Google Scholar]
  • 45.Food and Drug Administration (FDA) Method to Reduce Pathogens from Fresh and Cut Produce.Center for Safety and appied nutrition. 2001. http://www.Cfsan.Fda.gov.com.
  • 46.Rodgers SL, Cash JN, Siddiq M, Ryser ET. Acomparison of Different Chemical Sanitizers for Inactivating Escherichia Coli O157:H7 and Listeria monocytogenes In Solution and on Apple, Lettuce, Strawberries and Cantaloupe. J Food Prot. 2004;67:721–731. doi: 10.4315/0362-028x-67.4.721. [DOI] [PubMed] [Google Scholar]

Articles from Iranian Journal of Public Health are provided here courtesy of Tehran University of Medical Sciences

RESOURCES