- Email: [email protected]
Synergistic effect of ionizing radiation on chemical disinfectant treatments for reduction of natural microflora on seafood
Radiation Physics and Chemistry 81 (2012) 1091–1094
Contents lists available at SciVerse ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Synergistic effect of ionizing radiation on chemical disinfectant treatments for reduction of natural microflora on seafood Hyunjoo Kim a, Ji-Hyoung Ha a, Ju-Woon Lee b, Cheorun Jo c, Sang-Do Ha a,n a
Department of Food Science and Technology, Chung-Ang University, Anseong 456-756, Republic of Korea Team for Radiation Food Science & Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Republic of Korea c Department of Animal Science and Technology, Chungnam National University, 220 Gung-dong, Daejeon 305-764, Republic of Korea b
a r t i c l e i n f o
abstract
Article history: Received 21 June 2011 Accepted 27 December 2011 Available online 21 January 2012
The purpose of this study was to determine whether combined treatments would produce synergistic disinfection effects on seafood products such as mussel and squid compared with single treatments. We investigated the bactericidal effects of chlorine and ionizing radiation on the natural microflora of mussel and squid. Total aerobic bacteria initially ranged from 102 to 104 Log CFU/g. More than 100 ppm of chlorine and irradiation at 1 kGy were sufficient to reduce the total aerobic bacteria on mussel and squid to a level lower than detection limit (10 CFU/g). Synergistic effects against natural microflora were observed for all combined treatment. These results suggest that a significant synergistic benefit results from combine chlorine-ionizing radiation treatment against natural microflora on mussel and squid. & 2012 Elsevier Ltd. All rights reserved.
Keywords: Seafoods Chlorine Gamma irradiation Electron beam irradiation
1. Introduction Seafood has become a predominant consumer product for large segments of the population. Seafood consumption in Korea has increased rapidly since 2000 (Mok et al., 2007). Seafood is more perishable than other high-protein foods. In seafood products, changes in flavor, odor, texture and color reflect the level of freshness or decomposition, caused primarily by microbial activity (Cruz-Romero et al., 2008). There have been some reports on the levels of Vibrio parahaemolyticus and V. vulnificus and the incidence of Salmonella spp. and Listeria spp. in various different seafood products (Mahmoud, 2009; Parihar et al., 2008; Ponce et al., 2008; Yang et al., 2008). Therefore, sanitation treatment is needed for this particular food product. Most studies on chemical or physical methods to ensure seafood safety have focused on single-agent disinfection techniques (Mahmoud, 2009). However, combined chemico-physical treatments as used in hurdle approaches are often more effective than single treatments (Ha and Ha, 2010). The implementation of hurdle technology in food matrices is becoming more attractive because individual treatments can be used at lower doses without affecting the taste or smell of the food product while still improving food safety. In these experiments, combined disinfection treatments have produced beneficial synergistic effects. The synergistic effect occurs when the
n
Corresponding author. Tel.: þ82 31 670 4831; fax: þ82 31 675 4853. E-mail address: [email protected] (S.-D. Ha).
0969-806X/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2011.12.051
benefit of a combination of disinfection treatments is greater than the summed effect of the individual treatments (Ha and Ha, 2010). Studies on combined disinfection treatments for various food products have been commonly reported. Previous studies have shown that chemical-gamma irradiation treatment can improve shelf life and microbiological quality of meat products, and shrimp (Chawla et al., 2006; Kanatt et al., 2006). However, very few studies have examined disinfection of seafood using chemical-ionizing radiation methods. The objective of this study was to assess the effectiveness of chlorine and ionizing radiation individually and combined when applied sequentially to seafood (mussel and squid) and to determine the efficacy of gamma and electron beam irradiation in ionizing radiation.
2. Materials and methods 2.1. Sample preparation, sanitizing solutions and irradiation treatment Mussel and squid were purchased from a local market in Anseong, Korea. The samples were transferred into sterilized oxygen-impermeable nylon bags. Chlorine at concentrations of 50 to 200 ppm (Sodium hypochlorite, 12%, Duksan, Korea) was used as the chemical disinfectant (10 1C). To perform the inactivation tests for the sanitizer, 10 g of samples were washed with sterile distilled water for 2 min, treated with the sanitizers for 2 min and then dried for 5 min. Sanitizer-treated samples were
1092
H. Kim et al. / Radiation Physics and Chemistry 81 (2012) 1091–1094
transferred into sterilized oxygen-impermeable nylon bags (Sunkyung, Seoul, Korea) with sterilized spoon and clean bench. The samples were irradiated at 0, 0.3, 0.5, 0.7 and 1.0 kGy in a cobalt60 gamma irradiator (Nordion International, Ottawa, Ontario, Canada) and linear electron beam RF accelerator (EB Tech, Daejeon, Korea). After irradiation, the samples were stored in a refrigerator set at 4 1C for further analysis. 2.2. Combined disinfection with chlorine treatment and ionizing radiation Inactivation efficacies of the combined treatments were compared with those for the individual treatments to estimate any synergistic effect resulting from combined chemical-ionizing radiation. The procedure described by Koivunen and HeinonenTanski (2005) was used for the combined disinfectant treatments. The synergistic effect values of combined chlorineionizing radiation disinfection treatments were calculated using the following equation: Synergistic effect value ¼ AðB þ CÞ where A is the reduction from combined chlorine-ionizing radiation disinfection, B is the reduction from ionizing radiation alone and C is the reduction from chlorine disinfection alone. 2.3. Microbial analysis The prepared sample (10 g) was homogenized for 2 min in a sterile stomacher bag containing 90 mL of sterile saline solution using a stomacher (bag mixers400, Interscience Co, France). Media for enumeration of the total aerobic bacteria was prepared using total plate count agar (Difco Laboratories, Detroit, MI, USA), and the plates were incubated at 37 1C for 48 h. The colony forming units (CFU) per gram were counted at a dilution of 30 to 300 CFU per plate. 2.4. Statistical analysis All experiments were carried out in triplicate with three observation numbers per trial. One-way analysis of variance was performed using the SPSS software system and Duncan’s multiple range test was used to compare the differences among the mean values. The result was expressed as a log CFU/g and the response surface was described using the SigmaPlot software system (SigmaPlot 7.0).
3. Results and discussions
Fig. 1. Reduction in total aerobic bacteria (Log CFU/g) resulting from combined chlorine-ionizing radiation ((a) gamma ray, (b) electron beam) treatment against natural microflora of mussel.
3.1. Microbiological evaluation Figs. 1 and 2 show the reduction of total aerobic bacteria in mussel and squid after ionizing radiation with chlorine treatments. The initial total aerobic bacterial population of the mussel and squid were 4.21 and 4.25 log CFU/g, respectively, and the decrease in total aerobic bacteria relative to the control depended on the chlorine concentration and radiation dose. Natural microflora were eliminated from mussel and squid after treatments with 100 ppm of chlorine and 1 kGy of gamma irradiation and 150 ppm of chlorine and 1 kGy of electron beam irradiation, respectively (Tables 1 and 2; Figs. 1 and 2). Gamma irradiation was more effective than electron beam irradiation in eliminating microorganisms in mussel and squid. Previous studies reported that higher sterilization efficiencies were obtained in foods treated with gamma irradiation when compared with electron beam. One of the reasons for this, in addition to the
penetration depth, can be explained by the difference in dose rate. Much higher dose rates of the electron beam causes suppression of oxidation damage in microorganisms. However, since this high dose rate of irradiation can also suppress oxidative deterioration in food itself, the dose rate effect of electron beam irradiation may not be large and will not cause serious problems in commercial application (Kim et al., 2010). 3.2. Synergistic effect Table 3 shows the synergistic effects of chlorine and ionizing radiation treatment on the inactivation of natural microflora in mussel and squid. Synergistic effects were observed for all combined treatments against natural microflora. The largest synergistic value for mussel and squid were 2.74 and 2.77 log CFU/g when the combined treatment was 150 ppm
H. Kim et al. / Radiation Physics and Chemistry 81 (2012) 1091–1094
1093
Table 1 Microbial population of mussel treated by gamma and electron beam irradiation. Dose (kGy)
Chlorine conc. (ppm)
Viable cell count (log CFU/g) Gamma ray
Electron beam
0
0 50 100 150 200
4.21 70.04a 4.16 70.02 4.14 70.01 4.10 70.01 4.08 70.02
4.23 7 0.03 4.17 7 0.01 4.15 7 0.02 4.13 7 0.01 4.107 0.02
0.3
0 50 100 150 200
4.05 70.01 3.99 70.02 3.94 70.03 3.87 70.03 3.80 70.01
4.087 0.02 4.037 0.02 3.98 7 0.02 3.91 7 0.02 3.85 7 0.03
0.5
0 50 100 150 200
3.90 70.01 3.85 70.03 3.81 70.03 3.72 70.02 3.71 70.01
3.95 7 0.01 3.91 7 0.01 3.84 7 0.02 3.79 7 0.03 3.69 7 0.02
0.7
0 50 100 150 200
3.03 70.03 2.98 70.02 2.89 70.04 2.80 70.03 2.61 70.02
3.057 0.02 3.007 0.02 2.94 7 0.02 2.89 7 0.03 2.69 7 0.04
1.0
0 50 100 150 200
2.73 70.02 2.48 70.04 NGb NG NG
2.84 7 0.01 2.607 0.03 2.46 7 0.04 NG NG
a b
Means 7standard deviation (n¼ 3). Viables with no growth at a detection limit o10 CFU/g.
Table 2 Microbial population of squid treated by gamma and electron beam irradiation. Dose (kGy)
Fig. 2. Reduction in total aerobic bacteria (Log CFU/g) resulting from combined chlorine-ionizing radiation ((a) gamma ray, (b) electron beam) treatment against natural microflora of squid.
of chlorine and 1 kGy of irradiation. Synergistic effects of chemical sanitizers differed among the natural microflora tested in this study and were not dependent on concentration or irradiation dose. This result was similar to those reported previously (Ha and Ha, 2010). In the present study, the combined chlorine-ionizing radiation disinfection treatments resulted in synergistic benefits in regards to reducing the numbers of natural microflora. These results indicate that these combined methods result in greater reduction than when the single methods are used alone. In this study, the combined disinfection with chlorine followed by ionizing radiation treatment produced synergistic effects. In conclusion, the present study demonstrated that the combined chlorine-ionizing radiation disinfection treatments resulted in greater reduction than did each treatment alone against natural microflora and holds great promise for use in industrial applications.
Chlorine conc. (ppm)
Viable cell count (log CFU/g) Gamma ray
Electron beam
0
0 50 100 150 200
4.23 70.02a 4.20 70.07 4.19 70.01 4.18 70.03 4.15 70.02
4.25 7 0.02 4.22 7 0.01 4.19 7 0.01 4.18 7 0.02 4.18 7 0.03
0.3
0 50 100 150 200
4.05 70.01 4.01 70.01 3.97 70.01 3.91 70.01 3.85 70.03
4.11 7 0.01 4.087 0.02 4.047 0.01 4.007 0.02 3.91 7 0.05
0.5
0 50 100 150 200
3.93 70.03 3.87 70.02 3.80 70.01 3.75 70.02 3.65 70.04
3.99 7 0.01 3.93 7 0.02 3.87 7 0.03 3.84 7 0.03 3.76 7 0.06
0.7
0 50 100 150 200
2.98 70.02 2.94 70.01 2.87 70.01 2.79 70.04 2.70 70.02
3.53 7 0.12 3.007 0.01 2.93 7 0.02 3.89 7 0.02 2.807 0.01
1.0
0 50 100 150 200
2.50 70.01 2.37 70.04 NGb NG NG
2.84 7 0.02 2.67 7 0.06 2.54 7 0.04 NG NG
a b
Means 7standard deviation (n¼ 3). Viables with no growth at a detection limit o101 CFU/g.
1094
H. Kim et al. / Radiation Physics and Chemistry 81 (2012) 1091–1094
Table 3 Synergistic values of combined chlorine-ionizing radiation treatment against mussel and squid. Food samples
Radiation source
Dose (kGy)
Mean( 7 SD) synergistic effect value (log CFU/g)a 50 ppm
100 ppm
150 ppm
200 ppm
0.3 0.5 0.7 1.0 0.3 0.5 0.7 1.0
0.017 0.02bz 0.00 7 0.05bz 0.00 7 0.07bz 0.207 0.12ay 0.017 0.23bz 0.027 0.11bz 0.017 0.05bz 0.18 7 0.15az
0.047 0.13by 0.027 0.04cz 0.077 0.15by 2.66 7 0.21ax 0.027 0.09bz 0.037 0.07bz 0.037 0.12bz 0.307 0.15ay
0.077 0.03cy 0.077 0.09cx 0.12 7 0.07by 2.62 7 0.12ax 0.077 0.15by 0.067 0.21by 0.067 0.11by 2.74 7 0.07ax
0.12 70.10cx 0.06 70.06cy 0.29 70.07bx 2.66 70.11ax 0.10 70.22cx 0.13 70.07cx 0.23 70.15bx 2.71 70.21ax
0.3 0.5 0.7 1.0 0.3 0.5 0.7 1.0
0.017 0.07bz 0.037 0.09bz 0.017 0.21bz 0.107 0.15ay 0.00 7 0.11cz 0.037 0.06cz 0.14 7 0.16bz 0.507 0.07ay
0.047 0.23cz 0.097 0.11by 0.077 0.07by 2.46 7 0.02ax 0.017 0.05cz 0.067 0.02cy 0.247 0.09bz 0.547 0.06ay
0.097 0.03cy 0.13 7 0.06by 0.14 7 0.22by 2.45 7 0.11ax 0.047 0.15cy 0.087 0.04cy 0.57 7 0.07by 2.77 7 0.09ax
0.12 70.11cx 0.20 70.09bx 0.20 70.08bx 2.42 70.06ax 0.13 70.03cx 0.16 70.09cx 0.66 70.11bx 2.77 70.15ax
Mussel Gamma ray
Electron beam
Squid Gamma ray
Electron beam
Initial population; mussel—4.21 log CFU/g, squid—4.23 log CFU/g. Within the same column, means with different letters a, b or c differ significantly (P o 0.05). Within the same row, means with different letters x, y or z differ significantly (P o0.05). a Synergistic effect values¼ (reduction achieved with the chlorine treatment and the ionizing radiation treatment) (reduction achieved by the chlorine þionizing radiation treatment).
Acknowledgments This research was supported by the GRRC program of Gyeonggi province. [GRRC CAU 2011-B03, Development of Tailor-Made Rice Flour as a Food Ingredient]. References Chawla, S.P., Chander, R., Sharma, A., 2006. Safe and shelf-stable natural casing using hurdle technology. Food Control 17, 127–131. Cruz-Romero, M., Kelly, A.L., Kerry, J.P., 2008. Effects of high-pressure treatment on the microflora of oysters (Crassostrea gigas) during chilled storage. Innovat. Food Sci. Emerg. Technol. 9, 441–447. Ha, J.H., Ha, S.D., 2010. Synergistic effects of ethanol and UV radiation to reduce levels of selected foodborne pathogenic bacteria. J. Food Prot. 73, 556–561. Kanatt, S.R., Chawla, S.P., Chander, R., Sharma, A., 2006. Development of shelfstable, ready-to-eat (RTE) shrimps (Penaeus indicus) using g-radiation as one of the hurdles. LWT-Food Sci. Technol. 39, 621–626.
Kim, H.J., Ham, J.S., Lee, J.W., Kim, K., Ha, S.D., Jo, C., 2010. Effects of gamma and electron beam irradiation on the survival of pathogens inoculated into sliced and pizza cheeses. Radiat. Phys. Chem. 79, 731–734. Koivunen, J., Heinonen-Tanski, H., 2005. Inactivation of enteric microorganisms with chemical disinfectants, UV radiation and combined chemical/UV treatments. Water Res. 39, 1519–1526. Mahmoud, B.S.M., 2009. Reduction of Vibrio vulnificus in pure culture, half shell and whole shell oysters (Crassostrea virginica) by X-ray. Int. J. Food Microbiol. 130, 135–139. Mok, J.S., Lee, D.S., Yoon, H.D., Park, H.Y., Kim, Y.K., Wi, C.H., 2007. Proximate composition and nutritional evaluation of fisheries products from the Korean coast. J. Kor. Fish. Soc. 40 (5), 259–268. Parihar, V.S., Barbuddhe, S.B., Danielsson-Tham, M.L., Tham, W., 2008. Isolation and characterization of Listeria species from tropical seafoods. Food Control 19, 566–569. Ponce, E., Khan, A.A., Cheng, C.M., Summage-West, C., Cerniglia, C.E., 2008. Prevalence and characterization of Salmonella enterica serovar Weltevreden from imported seafood. Food Microbiol. 25, 29–35. Yang, Z., Jiao, X., Zhou, X., Cao, G., Fang, W., Gu, R., 2008. Isolation and molecular characterization of Vibrio parahaemolyticus from fresh, low-temperature preserved, dried, and salted seafood products in two coastal areas of eastern China. Int. J. Food Microbiol. 125, 279–285.
Contents lists available at SciVerse ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Synergistic effect of ionizing radiation on chemical disinfectant treatments for reduction of natural microflora on seafood Hyunjoo Kim a, Ji-Hyoung Ha a, Ju-Woon Lee b, Cheorun Jo c, Sang-Do Ha a,n a
Department of Food Science and Technology, Chung-Ang University, Anseong 456-756, Republic of Korea Team for Radiation Food Science & Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Republic of Korea c Department of Animal Science and Technology, Chungnam National University, 220 Gung-dong, Daejeon 305-764, Republic of Korea b
a r t i c l e i n f o
abstract
Article history: Received 21 June 2011 Accepted 27 December 2011 Available online 21 January 2012
The purpose of this study was to determine whether combined treatments would produce synergistic disinfection effects on seafood products such as mussel and squid compared with single treatments. We investigated the bactericidal effects of chlorine and ionizing radiation on the natural microflora of mussel and squid. Total aerobic bacteria initially ranged from 102 to 104 Log CFU/g. More than 100 ppm of chlorine and irradiation at 1 kGy were sufficient to reduce the total aerobic bacteria on mussel and squid to a level lower than detection limit (10 CFU/g). Synergistic effects against natural microflora were observed for all combined treatment. These results suggest that a significant synergistic benefit results from combine chlorine-ionizing radiation treatment against natural microflora on mussel and squid. & 2012 Elsevier Ltd. All rights reserved.
Keywords: Seafoods Chlorine Gamma irradiation Electron beam irradiation
1. Introduction Seafood has become a predominant consumer product for large segments of the population. Seafood consumption in Korea has increased rapidly since 2000 (Mok et al., 2007). Seafood is more perishable than other high-protein foods. In seafood products, changes in flavor, odor, texture and color reflect the level of freshness or decomposition, caused primarily by microbial activity (Cruz-Romero et al., 2008). There have been some reports on the levels of Vibrio parahaemolyticus and V. vulnificus and the incidence of Salmonella spp. and Listeria spp. in various different seafood products (Mahmoud, 2009; Parihar et al., 2008; Ponce et al., 2008; Yang et al., 2008). Therefore, sanitation treatment is needed for this particular food product. Most studies on chemical or physical methods to ensure seafood safety have focused on single-agent disinfection techniques (Mahmoud, 2009). However, combined chemico-physical treatments as used in hurdle approaches are often more effective than single treatments (Ha and Ha, 2010). The implementation of hurdle technology in food matrices is becoming more attractive because individual treatments can be used at lower doses without affecting the taste or smell of the food product while still improving food safety. In these experiments, combined disinfection treatments have produced beneficial synergistic effects. The synergistic effect occurs when the
n
Corresponding author. Tel.: þ82 31 670 4831; fax: þ82 31 675 4853. E-mail address: [email protected] (S.-D. Ha).
0969-806X/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2011.12.051
benefit of a combination of disinfection treatments is greater than the summed effect of the individual treatments (Ha and Ha, 2010). Studies on combined disinfection treatments for various food products have been commonly reported. Previous studies have shown that chemical-gamma irradiation treatment can improve shelf life and microbiological quality of meat products, and shrimp (Chawla et al., 2006; Kanatt et al., 2006). However, very few studies have examined disinfection of seafood using chemical-ionizing radiation methods. The objective of this study was to assess the effectiveness of chlorine and ionizing radiation individually and combined when applied sequentially to seafood (mussel and squid) and to determine the efficacy of gamma and electron beam irradiation in ionizing radiation.
2. Materials and methods 2.1. Sample preparation, sanitizing solutions and irradiation treatment Mussel and squid were purchased from a local market in Anseong, Korea. The samples were transferred into sterilized oxygen-impermeable nylon bags. Chlorine at concentrations of 50 to 200 ppm (Sodium hypochlorite, 12%, Duksan, Korea) was used as the chemical disinfectant (10 1C). To perform the inactivation tests for the sanitizer, 10 g of samples were washed with sterile distilled water for 2 min, treated with the sanitizers for 2 min and then dried for 5 min. Sanitizer-treated samples were
1092
H. Kim et al. / Radiation Physics and Chemistry 81 (2012) 1091–1094
transferred into sterilized oxygen-impermeable nylon bags (Sunkyung, Seoul, Korea) with sterilized spoon and clean bench. The samples were irradiated at 0, 0.3, 0.5, 0.7 and 1.0 kGy in a cobalt60 gamma irradiator (Nordion International, Ottawa, Ontario, Canada) and linear electron beam RF accelerator (EB Tech, Daejeon, Korea). After irradiation, the samples were stored in a refrigerator set at 4 1C for further analysis. 2.2. Combined disinfection with chlorine treatment and ionizing radiation Inactivation efficacies of the combined treatments were compared with those for the individual treatments to estimate any synergistic effect resulting from combined chemical-ionizing radiation. The procedure described by Koivunen and HeinonenTanski (2005) was used for the combined disinfectant treatments. The synergistic effect values of combined chlorineionizing radiation disinfection treatments were calculated using the following equation: Synergistic effect value ¼ AðB þ CÞ where A is the reduction from combined chlorine-ionizing radiation disinfection, B is the reduction from ionizing radiation alone and C is the reduction from chlorine disinfection alone. 2.3. Microbial analysis The prepared sample (10 g) was homogenized for 2 min in a sterile stomacher bag containing 90 mL of sterile saline solution using a stomacher (bag mixers400, Interscience Co, France). Media for enumeration of the total aerobic bacteria was prepared using total plate count agar (Difco Laboratories, Detroit, MI, USA), and the plates were incubated at 37 1C for 48 h. The colony forming units (CFU) per gram were counted at a dilution of 30 to 300 CFU per plate. 2.4. Statistical analysis All experiments were carried out in triplicate with three observation numbers per trial. One-way analysis of variance was performed using the SPSS software system and Duncan’s multiple range test was used to compare the differences among the mean values. The result was expressed as a log CFU/g and the response surface was described using the SigmaPlot software system (SigmaPlot 7.0).
3. Results and discussions
Fig. 1. Reduction in total aerobic bacteria (Log CFU/g) resulting from combined chlorine-ionizing radiation ((a) gamma ray, (b) electron beam) treatment against natural microflora of mussel.
3.1. Microbiological evaluation Figs. 1 and 2 show the reduction of total aerobic bacteria in mussel and squid after ionizing radiation with chlorine treatments. The initial total aerobic bacterial population of the mussel and squid were 4.21 and 4.25 log CFU/g, respectively, and the decrease in total aerobic bacteria relative to the control depended on the chlorine concentration and radiation dose. Natural microflora were eliminated from mussel and squid after treatments with 100 ppm of chlorine and 1 kGy of gamma irradiation and 150 ppm of chlorine and 1 kGy of electron beam irradiation, respectively (Tables 1 and 2; Figs. 1 and 2). Gamma irradiation was more effective than electron beam irradiation in eliminating microorganisms in mussel and squid. Previous studies reported that higher sterilization efficiencies were obtained in foods treated with gamma irradiation when compared with electron beam. One of the reasons for this, in addition to the
penetration depth, can be explained by the difference in dose rate. Much higher dose rates of the electron beam causes suppression of oxidation damage in microorganisms. However, since this high dose rate of irradiation can also suppress oxidative deterioration in food itself, the dose rate effect of electron beam irradiation may not be large and will not cause serious problems in commercial application (Kim et al., 2010). 3.2. Synergistic effect Table 3 shows the synergistic effects of chlorine and ionizing radiation treatment on the inactivation of natural microflora in mussel and squid. Synergistic effects were observed for all combined treatments against natural microflora. The largest synergistic value for mussel and squid were 2.74 and 2.77 log CFU/g when the combined treatment was 150 ppm
H. Kim et al. / Radiation Physics and Chemistry 81 (2012) 1091–1094
1093
Table 1 Microbial population of mussel treated by gamma and electron beam irradiation. Dose (kGy)
Chlorine conc. (ppm)
Viable cell count (log CFU/g) Gamma ray
Electron beam
0
0 50 100 150 200
4.21 70.04a 4.16 70.02 4.14 70.01 4.10 70.01 4.08 70.02
4.23 7 0.03 4.17 7 0.01 4.15 7 0.02 4.13 7 0.01 4.107 0.02
0.3
0 50 100 150 200
4.05 70.01 3.99 70.02 3.94 70.03 3.87 70.03 3.80 70.01
4.087 0.02 4.037 0.02 3.98 7 0.02 3.91 7 0.02 3.85 7 0.03
0.5
0 50 100 150 200
3.90 70.01 3.85 70.03 3.81 70.03 3.72 70.02 3.71 70.01
3.95 7 0.01 3.91 7 0.01 3.84 7 0.02 3.79 7 0.03 3.69 7 0.02
0.7
0 50 100 150 200
3.03 70.03 2.98 70.02 2.89 70.04 2.80 70.03 2.61 70.02
3.057 0.02 3.007 0.02 2.94 7 0.02 2.89 7 0.03 2.69 7 0.04
1.0
0 50 100 150 200
2.73 70.02 2.48 70.04 NGb NG NG
2.84 7 0.01 2.607 0.03 2.46 7 0.04 NG NG
a b
Means 7standard deviation (n¼ 3). Viables with no growth at a detection limit o10 CFU/g.
Table 2 Microbial population of squid treated by gamma and electron beam irradiation. Dose (kGy)
Fig. 2. Reduction in total aerobic bacteria (Log CFU/g) resulting from combined chlorine-ionizing radiation ((a) gamma ray, (b) electron beam) treatment against natural microflora of squid.
of chlorine and 1 kGy of irradiation. Synergistic effects of chemical sanitizers differed among the natural microflora tested in this study and were not dependent on concentration or irradiation dose. This result was similar to those reported previously (Ha and Ha, 2010). In the present study, the combined chlorine-ionizing radiation disinfection treatments resulted in synergistic benefits in regards to reducing the numbers of natural microflora. These results indicate that these combined methods result in greater reduction than when the single methods are used alone. In this study, the combined disinfection with chlorine followed by ionizing radiation treatment produced synergistic effects. In conclusion, the present study demonstrated that the combined chlorine-ionizing radiation disinfection treatments resulted in greater reduction than did each treatment alone against natural microflora and holds great promise for use in industrial applications.
Chlorine conc. (ppm)
Viable cell count (log CFU/g) Gamma ray
Electron beam
0
0 50 100 150 200
4.23 70.02a 4.20 70.07 4.19 70.01 4.18 70.03 4.15 70.02
4.25 7 0.02 4.22 7 0.01 4.19 7 0.01 4.18 7 0.02 4.18 7 0.03
0.3
0 50 100 150 200
4.05 70.01 4.01 70.01 3.97 70.01 3.91 70.01 3.85 70.03
4.11 7 0.01 4.087 0.02 4.047 0.01 4.007 0.02 3.91 7 0.05
0.5
0 50 100 150 200
3.93 70.03 3.87 70.02 3.80 70.01 3.75 70.02 3.65 70.04
3.99 7 0.01 3.93 7 0.02 3.87 7 0.03 3.84 7 0.03 3.76 7 0.06
0.7
0 50 100 150 200
2.98 70.02 2.94 70.01 2.87 70.01 2.79 70.04 2.70 70.02
3.53 7 0.12 3.007 0.01 2.93 7 0.02 3.89 7 0.02 2.807 0.01
1.0
0 50 100 150 200
2.50 70.01 2.37 70.04 NGb NG NG
2.84 7 0.02 2.67 7 0.06 2.54 7 0.04 NG NG
a b
Means 7standard deviation (n¼ 3). Viables with no growth at a detection limit o101 CFU/g.
1094
H. Kim et al. / Radiation Physics and Chemistry 81 (2012) 1091–1094
Table 3 Synergistic values of combined chlorine-ionizing radiation treatment against mussel and squid. Food samples
Radiation source
Dose (kGy)
Mean( 7 SD) synergistic effect value (log CFU/g)a 50 ppm
100 ppm
150 ppm
200 ppm
0.3 0.5 0.7 1.0 0.3 0.5 0.7 1.0
0.017 0.02bz 0.00 7 0.05bz 0.00 7 0.07bz 0.207 0.12ay 0.017 0.23bz 0.027 0.11bz 0.017 0.05bz 0.18 7 0.15az
0.047 0.13by 0.027 0.04cz 0.077 0.15by 2.66 7 0.21ax 0.027 0.09bz 0.037 0.07bz 0.037 0.12bz 0.307 0.15ay
0.077 0.03cy 0.077 0.09cx 0.12 7 0.07by 2.62 7 0.12ax 0.077 0.15by 0.067 0.21by 0.067 0.11by 2.74 7 0.07ax
0.12 70.10cx 0.06 70.06cy 0.29 70.07bx 2.66 70.11ax 0.10 70.22cx 0.13 70.07cx 0.23 70.15bx 2.71 70.21ax
0.3 0.5 0.7 1.0 0.3 0.5 0.7 1.0
0.017 0.07bz 0.037 0.09bz 0.017 0.21bz 0.107 0.15ay 0.00 7 0.11cz 0.037 0.06cz 0.14 7 0.16bz 0.507 0.07ay
0.047 0.23cz 0.097 0.11by 0.077 0.07by 2.46 7 0.02ax 0.017 0.05cz 0.067 0.02cy 0.247 0.09bz 0.547 0.06ay
0.097 0.03cy 0.13 7 0.06by 0.14 7 0.22by 2.45 7 0.11ax 0.047 0.15cy 0.087 0.04cy 0.57 7 0.07by 2.77 7 0.09ax
0.12 70.11cx 0.20 70.09bx 0.20 70.08bx 2.42 70.06ax 0.13 70.03cx 0.16 70.09cx 0.66 70.11bx 2.77 70.15ax
Mussel Gamma ray
Electron beam
Squid Gamma ray
Electron beam
Initial population; mussel—4.21 log CFU/g, squid—4.23 log CFU/g. Within the same column, means with different letters a, b or c differ significantly (P o 0.05). Within the same row, means with different letters x, y or z differ significantly (P o0.05). a Synergistic effect values¼ (reduction achieved with the chlorine treatment and the ionizing radiation treatment) (reduction achieved by the chlorine þionizing radiation treatment).
Acknowledgments This research was supported by the GRRC program of Gyeonggi province. [GRRC CAU 2011-B03, Development of Tailor-Made Rice Flour as a Food Ingredient]. References Chawla, S.P., Chander, R., Sharma, A., 2006. Safe and shelf-stable natural casing using hurdle technology. Food Control 17, 127–131. Cruz-Romero, M., Kelly, A.L., Kerry, J.P., 2008. Effects of high-pressure treatment on the microflora of oysters (Crassostrea gigas) during chilled storage. Innovat. Food Sci. Emerg. Technol. 9, 441–447. Ha, J.H., Ha, S.D., 2010. Synergistic effects of ethanol and UV radiation to reduce levels of selected foodborne pathogenic bacteria. J. Food Prot. 73, 556–561. Kanatt, S.R., Chawla, S.P., Chander, R., Sharma, A., 2006. Development of shelfstable, ready-to-eat (RTE) shrimps (Penaeus indicus) using g-radiation as one of the hurdles. LWT-Food Sci. Technol. 39, 621–626.
Kim, H.J., Ham, J.S., Lee, J.W., Kim, K., Ha, S.D., Jo, C., 2010. Effects of gamma and electron beam irradiation on the survival of pathogens inoculated into sliced and pizza cheeses. Radiat. Phys. Chem. 79, 731–734. Koivunen, J., Heinonen-Tanski, H., 2005. Inactivation of enteric microorganisms with chemical disinfectants, UV radiation and combined chemical/UV treatments. Water Res. 39, 1519–1526. Mahmoud, B.S.M., 2009. Reduction of Vibrio vulnificus in pure culture, half shell and whole shell oysters (Crassostrea virginica) by X-ray. Int. J. Food Microbiol. 130, 135–139. Mok, J.S., Lee, D.S., Yoon, H.D., Park, H.Y., Kim, Y.K., Wi, C.H., 2007. Proximate composition and nutritional evaluation of fisheries products from the Korean coast. J. Kor. Fish. Soc. 40 (5), 259–268. Parihar, V.S., Barbuddhe, S.B., Danielsson-Tham, M.L., Tham, W., 2008. Isolation and characterization of Listeria species from tropical seafoods. Food Control 19, 566–569. Ponce, E., Khan, A.A., Cheng, C.M., Summage-West, C., Cerniglia, C.E., 2008. Prevalence and characterization of Salmonella enterica serovar Weltevreden from imported seafood. Food Microbiol. 25, 29–35. Yang, Z., Jiao, X., Zhou, X., Cao, G., Fang, W., Gu, R., 2008. Isolation and molecular characterization of Vibrio parahaemolyticus from fresh, low-temperature preserved, dried, and salted seafood products in two coastal areas of eastern China. Int. J. Food Microbiol. 125, 279–285.