CAO Rong, LIU Qi, CHEN Shengjun YANG Xianqing and LI Laihao

1)Key Laboratory of Aquatic Product Processing,Ministry of Agriculture,South China Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Guangzhou510300,P.R. China

2)Department of Food Engineering and Nutrition,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Qingdao266071,P.R. China

Application of Lactic Acid Bacteria (LAB) in Freshness Keeping of Tilapia Fillets as Sashimi

CAO Rong1),2), LIU Qi2), CHEN Shengjun1), YANG Xianqing1), and LI Laihao1),*

1)Key Laboratory of Aquatic Product Processing,Ministry of Agriculture,South China Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Guangzhou510300,P.R. China

2)Department of Food Engineering and Nutrition,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Qingdao266071,P.R. China

Aquatic products are extremely perishable food commodities. Developing methods to keep the freshness of fish represents a major task of the fishery processing industry. Application of Lactic Acid Bacteria (LAB) as food preservative is a novel approach. In the present study, the possibility of using lactic acid bacteria in freshness keeping of tilapia fillets as sashimi was examined. Fish fillets were dipped inLactobacillus plantarum1.19 (obtained from China General Microbiological Culture Collection Center) suspension as LAB-treated group. Changes inK-value, APC, sensory properties and microbial flora were analyzed. Results showed that LAB treatment slowed the increase ofK-value and APC in the earlier storage, and caused a smooth decrease in sensory score. Gram-negative bacteria dominated during refrigerated storage, withPseudomonasandAeromonasbeing relatively abundant.Lactobacillus plantarum1.19 had no obvious inhibitory effect against these Gram-negatives. However,Lactobacillus plantarum1.19 changed the composition of Gram-positive bacteria. NoMicrococcuswere detected and the proportion ofStaphylococcusdecreased in the spoiled LAB-treated samples. The period that tilapia fillets could be used as sashimi material extended from 24 h to 48 h after LAB treatment. The potential of using LAB in sashimi processing was confirmed.

lactic acid bacteria; tilapia fillets; sashimi; freshness; microbial flora

1 Introduction

Freshness makes a major contribution to the quality of fish. A lot of preservation techniques have been developed to improve the microbial safety and extend shelf-life of aquatic products (Ghalyet al., 2010; Chenget al., 2014). Despite the advantage of chemical preservatives as convenient, food producers and consumers have both desired to reduce the use of synthetic chemicals in food preservation. Consequently, there have been increasing interests in the application of natural agents as bio-preservatives, which could extend the shelf-life and minimize the negative impact on the nutrition and sensory properties (Singhet al., 2010; Mehtaet al., 2013). Recently, particular attention has been paid in using lactic acid bacteria (LAB) and their metabolites as natural food preservation agents (Ghanbariet al., 2013).

LAB are well-known for their capacity to restrict the growth of unwanted organisms through competition for nutrients and/or generation of a wide range of anti-microbial metabolites such as organic acids, diacetyl, acetoin, hydrogen peroxide, reuterin, reutericyclin, antifungalpeptides, and bacteriocins (Chen and Hoover, 2003; Gálvezet al., 2007). LAB and their metabolites have been widely used in preservation of agricultural products and meat, and some strains have been reported to be antagonistic to pathogens and spoilage organisms (Tamanget al., 2005; Kostrzynska, and Bachand, 2006; Konthamet al., 2014).

In the field of aquatic products, quite a number of studies have focused on using LAB to control pathogenic organisms in lightly preserved and semi-preserved fish products (Nyk?nenet al., 2000; Yamazakiet al., 2003; H?SARet al., 2009). However, studies about LAB in fish freshness keeping are relatively few. On the other hand, fish fillet served as raw is called sashimi in Japan, which is a traditional delicacy and has become very popular in the world. There have long been issues regarding its storage due to the short shelf-life.

In this study, tilapia (Oreochromis niloticus) was selected as the experiment material for its global scale cultivation and consumption. Previous work has focused on quality assessment of tilapia with different storage forms (Caoet al., 2009) and shelf-life extension by bio-preservative (Caoet al., 2012). The objective of the present study was to examine the effect of LAB on freshness keeping of tilapia fillets as sashimi under refrigerated storage.

2 Materials and Methods

2.1 Tilapia Fillets Preparation

Tilapia (Oreochromis niloticus) with weight of 1000 ± 200 g were obtained from a local aquatic farm in Qingdao, China. Fish samples were packed in insulated polystyrene boxes and delivered to laboratory within 2 h after catching. After arrival, fish were slaughtered by immersing in ice cold water and then headed, gutted and filleted with sterilized knives. All tilapia fillets were kept at 4 ± 1℃ without isolation from air.

2.2 LAB Treatment

Lactobacillus plantarum1.19 was obtained from China General Microbiological Culture Collection Center (CGMCC). MRS medium was used for incubation and enumeration. The LAB cells used in the following treatment were in logarithmic phase.

Bacteria suspension with 105CFU mL-1ofLactobacillus plantarum1.19 in sterile saline solution was prepared. Tilapia fillets were dipped in the bacterial suspension for 3 min, then drained and kept in an opened plate under 4 ±1℃ as the LAB-treated samples. Control samples were dipped in sterile water.

2.3 Freshness Measurement

K-values and Aerobic plate counts (APC) were selected as the biochemical and microbiological indicators for freshness, respectively (Caoet al., 2009).

K-values were determined according to the method proposed by Fanet al. (2008) and defined by the following equation：

Aerobic plate counts (APC) were determined as follows： fish meat 25 g was taken aseptically in a vertical laminar-flow cabinet and transferred to a stomacher bag containing 225 mL of peptone water (0.1%). The meat was homogenized for 60 s. Ten-fold serial dilutions were made and samples (0.1 mL) were spread on triplicate nutrient agar plates. The number of colony-forming units (CFU) for each plate was counted after incubation at 30℃for 48 h and transformed into logarithms.

2.4 Sensory Assessment

The sensory properties of tilapia fillets were measured by a panel of six trained assessors from the staff of Department of Food Engineering & Nutrition, Yellow Sea Fisheries Research Institute. Fish samples were assessed on the basis of appearance, odour, taste and texture characteristics using a nine point scale (one, dislike extremely to nine, like extremely). A sensory score of four was taken as the borderline of acceptability.

2.5 Microbial Flora Determination

Plates with colony number between 20 and 50 were selected. All colonies were picked and streaked on nutrient agar three times to obtain pure cultures. Isolated strains were identified to the genus level according to Dortheet al.(2003). The scheme is suitable for the identification of bacteria isolated from aquatic products under processing environments.

2.6 Statistical Analysis

Statistical analysis was performed using SPSS 15.0 (IBM Inc.). Results were presented as mean values±S.D. (n= 2×3). The Student’s t-test was employed to calculate significance. The differences between the means were considered significant whenP＜ 0.05.

3 Results and Discussion

3.1K-value

K-value, which is the index of the degradation of ATP, has been widely used as the most effective indicator of fish freshness (Vazquez-Ortizet al., 1997). For our freshly caught fish, the initialK-value of tilapia was 6.2% (Fig.1). This result was similar to previous findings (Caoet al., 2009). During storage,K-value of control samples increased continuously. These changes are in accordance with those found in Atlantic herring (Ozogulet al., 2000), sea bream (Grigorakiset al., 2003) and cazon fish (Oca?o-Higueraet al., 2009), with an increase inK-value along with storage time being similarly reported. Lin and Morrissey (1994) suggested that fish withK-value of 60% or higher should be rejected for consumption. Tilapia fillets stored at 4℃ exceeded this level at day 5.

Fig.1 Changes inK-value of control and LAB-treated tilapia fillets during storage at 4 ± 1℃. The symbols diamond and triangle represent mean values of six measurements ± S.D. (n= 2 × 3).

TheK-values of LAB-treated samples were always lower than those of the control (P＜ 0.05) during the first 72 h storage. It could be concluded that LAB treatment inhibited the growth of certain microorganisms in the earlier storage period, and consequently resulted in the slower ATP degradation. LAB-treatment showed no significant differences in shelf-life, and the time thatK-valueof LAB-treated samples reached 60% was also 5 d, which implied that the inhibitory function of LAB may be selective and limited. However, LAB-treatment doubled the period thatK-value was below 20%, which is remarkable and meaningful in sashimi processing. Raw fish with a K-value less than 20% can be used in sashimi (Hamada-Satoet al., 2005). Therefore, tilapia fillets could be used as sashimi material within 24 h. LAB treatment extends this period to 48 h.

3.2 APC

The initial APC of control samples was 4.26 lg CFU g-1(Fig.2), while that of LAB-treated samples was a little higher (4.66 lg CFU g-1). This difference was due to the process of LAB treatment that tilapia meat fillets were dipped in bacteria suspension for 3 min. APC value of 7.0 lg CFU g-1is considered the maximum level for acceptability of tilapia (Caoet al., 2009). During storage, APC of control samples increased rapidly without obvious lag phase and approached the level of 7.0 lg CFU g-1on day 4. For LAB-treated samples, APC also got close to 7.0 lg CFU g-1on day 4. No obvious effect on shelf life extension was observed. However, a 48 h lag phase of APC was observed in LAB-treated samples, coinciding exactly with theK-value results.

Fig.2 Changes in APC of control and LAB-treated tilapia fillets during storage at 4±1℃. The symbols diamond and triangle represent mean values of six measurements ± S.D. (n= 2×3).

3.3 Sensory Score

The acceptability of fish and fishery products during storage depends on the changes in their sensory attributes. No significant differences were detected between the control and LAB-treated groups at the beginning (P＞0.05), which indicated that LAB-treatment had no disadvantageous impact on sensory quality of tilapia fillets before storage.

Fish samples were considered to be acceptable for human consumption until the sensory score reached 4.0. During storage, a sharp decrease of sensory score was observed in the control group, and became unacceptable on day 6 (Fig.3). For LAB-treated samples, the freshness score decreased much slower, especially during the first 72 h. However, the time that sensory score reached 4.0 was also 6 d.

Fig.3 Changes in sensory score of control and LAB-treated tilapia fillets during storage at 4±1℃. The symbols diamond and triangle represent mean values of six measurements ± S.D. (n= 2×3).

3.4 Shelf Life

The shelf life determined by sensory values in this experiment was somewhat longer than expected and was inconsistent with the results ofK-value and APC analysis. The reason might be that sensory evaluation was subjective and could lag behind the biochemical change and microorganism propagation. The low storage temperature might exaggerate this phenomenon by delayed exterior signs of deterioration in tilapia fillet while interior quality changed greatly. Thus, other techniques for judging freshness such as microbiological evaluation andK-value analysis are required as a supplement and to be validated besides sensory evaluation.

When different spoilage parameters were combined together, shelf life of 96-120 h for both groups were determined. No obvious differences between the control and LAB-treated samples were detected. Researchers have reported different results about the role of LAB in shelf life extension of fish fillets. Katikouet al. (2007) found that Lactobacillus cultures could improve microbiological, chemical and odour changes of refrigerated vacuumpackaged trout fillets, and extend the shelf-life by 5 days. Kisla and ünlütürk (2004) reported that no significant differences in bacterial counts of rainbow trout fillets were found between the control group and that of lactic culture-dipped samples. These differences are understandable because many factors could influence the activity of LAB, such as their ability to adapt to environment, the production of antimicrobial metabolites, and initial microbial flora of the target samples.

On the other hand, LAB treatment extended the time for tilapia fillets to be reserved in sashimi from 24 h to 48 h, which implies that LAB may have a key effect in the early storage period and result in the lower increase inK-value and smooth decrease in sensory score.

3.5 Microbial Flora

Fresh tilapia fillets contained a high diversity of bacterial community. The isolated strains were identified and classified into more than 8 genus (Table 1). Gram-negative bacteria (62%) were dominant, withAeromonas(21%) andPseudomonas(14%) being relatively abundant. Gram-positive bacteria accounted for 31% of the total bacterial community, withStaphylococcus(14%) being relatively abundant. Other bacteria includedAlcaligenes,Enterobacteriaceae,Flavobacterium, andMicrococcus, with proportions ≤ 10%. These findings were different from several previous studies, which showed that the dominant bacteria wereVibriospp. in tilapia (Oreochromis niloticus) cultured in brackish water (Al-Harbi and Uddin, 2005) orChromobacterium violaceumin the gastrointestinal tract of Nile tilapia cultured in a semi-intensive system (Molinariet al., 2003). This is understandable as the bacterial community diversity of freshly caught fish reflects the bacterial flora of the surrounding environment and can be influenced by many factors such as seasonal period and collection method (Gramet al., 2002).

Table 1 Microbial community composition of fresh and spoiled tilapia fillets

Microbial flora changed dramatically during storage. As compared with fresh samples, spoiled tilapia fillets had a simpler composition of bacterial community with onlyPseudomonas,Aeromonas,StaphylococcusandMicrococcus. Among these,Pseudomonaswas the dominant species, accounting for 54% of the total spoilage bacterial community, followed byAeromonas(29%). Proportion of Gram-positive bacteria was only 14%, significantly lower than that of the fresh samples. The microbiology of fish and shellfish has been actively studied. Many reports described non-fermenting Gram-negative bacteria as the main part of the microbial flora (González-Rodr??guezet al., 2002; Alexopouloset al., 2011). Gram and Huss (1996) reported that the fish spoilage bacterial community was comprised primarily ofPseudomonasspp. andShewanella putrefaciensduring aerobic, iced storage. Therefore, controlling the growth of these bacteria will be very effective in shelf life extension.

However, LAB treatment indeed changed the composition of Gram-positive bacteria. NoMicrococcuswere detected. Proportion ofStaphylococcusdecreased to 3%. These indicate that LAB treatment could influence the growth of Gram-positive bacteria. This effect on Grampositive bacteria might result in the slow increase ofK-value and APC in the earlier storage period.

Valenzuelaet al. (2008) reported that inhibitory effect of LAB on target bacteria greatly depended on incubation temperature, with best results at 22 and 30℃. In this study, experiments were conducted under 4 ± 1℃ condition.Lactobacillus plantarum1.19 was different with some psychrotrophic LAB, which could flourish during chilled storage and contribute to environmental changes that discourage unwanted species. At the end of storage, cell number ofLactobacillus plantarum1.19 only increased to about 106CFU g-1. Low temperature restricted the increase of LAB cell number and affected their an-tagonistic activity. However, in the meantime, disadvantage caused by LAB when converting nutrient to organic acids can be reduced as a potential benefit. This assumption had been strongly proved by sensory assessment.

4 Conclusion

Lactobacillus plantarum1.19 had no obvious antagonistic effect against Gram-negative bacteria, such asPseudomonasandAeromonas, which were dominant in the spoilage process of tilapia fillets, therefore shelf-life of LAB-treated samples was not prolonged. However, LAB treatment slowed the increase ofK-value and APC of tilapia fillets in the earlier storage, and extended the period being suitable as sashimi material from 24 h to 48 h. LAB have great potential in fishery industry as biopreservatives, especially in sashimi processing and preservation.

Acknowledgements

This research was supported by the National Natural Science Foundation of China (No. 31301587) and Key Laboratory of Aquatic Product Processing, Ministry of Agriculture, China.

Alexopoulos, A., Plessas, S., Voidarou, C., Noussias, H., Stavropoulou, E., Mantzourani, I., and Bezirtzoglou, E., 2011. Microbial ecology of fish species growing in Greek sea farms and their watery environment.Anaerobe, 17 (6)： 264-266.

Al-Harbi, A. H., and Uddin, N., 2005. Bacterial diversity of tilapia (Oreochromis niloticus) cultured in brackish water in Saudi Arabia.Aquaculture, 250 (3)： 566-572.

Altieri, C., Speranza, B., Del Nobile, M., and Sinigaglia, M., 2005. Suitability of bifidobacteria and thymol as biopreservatives in extending the shelf life of fresh packed plaice fillets.Journal of Applied Microbiology, 99 (6)： 1294-1302.

Cao, R., Liu, Q., and Yin, B. Z., 2012. Chitosan extends the shelf-life of filleted tilapia (Oreochromis niloticus) during refrigerated storage.Journal of Ocean University of China, 11 (3)： 408-412.

1.2檢查方法采用GE公司的BrightSpeed 16層螺旋CT掃描機(jī)行常規(guī)劑量及低劑量胸部CT掃描。常規(guī)劑量掃描參數(shù):120 k V,220 m A,準(zhǔn)直40 mm,層厚5 mm,螺距1.375,矩陣512×512;低劑量掃描參數(shù):120 k V,120 m A,準(zhǔn)直40 mm,層厚5 mm,螺距1.375,矩陣512×512。CT掃描后獲得的數(shù)據(jù)采用骨算法進(jìn)行圖像重建和多平面重組。CT掃描操作界面自動(dòng)顯示放射線輻射劑量和單位(m Gy),掃描人員記錄隨設(shè)備自動(dòng)顯示的容積CT劑量指數(shù)(Volume CT dose index)。

Cao, R., Xue, C. H., Liu, Q., and Yin, B. Z., 2009. Microbiological, chemical and sensory assessment of (I) whole ungutted, (II) whole gutted and (III) filleted tilapia (Oreochromis niloticus) during refrigerated storage.International Journal of Food Science & Technology, 44 (11)： 2243-2248.

Caridi, A., 2002. Selection ofEscherichia coli-inhibiting strains ofLactobacillus paracaseisubsp.paracasei.Journal of Industrial Microbiology and Biotechnology, 29 (6)： 303-308.

Chen, H., and Hoover, D. G., 2003. Bacteriocins and their food applications.Comprehensive Reviews in Food Science andFood Safety, 2： 82-100.

Cheng, J. H., Sun, D. W., Han, Z., and Zeng, X. A., 2014. Texture and structure measurements and analyses for evaluation of fish and fillet freshness quality： A review.Comprehensive Reviews in Food Science and Food Safety, 13： 52-61.

Dorthe, B. R., Yin, N. G., Mette, H., Jesper, N., Christiansen, C. J., and Lone, G., 2003. The microbial ecology of processing equipment in different fish industries-analysis of the microflora during processing and following cleaning and disinfection.International Journal of Food Microbiology, 87： 242-243.

Fan, W. J., Chi, Y. L., and Zhang, S., 2008. The use of a tea polyphenol dip to extend the shelf life of silver carp (Hypophthalmicthys molitrix) during storage in ice.Food Chemistry, 108： 148-153.

Gálvez, A., Abriouel, H., López, R. L., and Omar, N. B., 2007. Bacteriocin-based strategies for food biopreservation.International Journal of Food Microbiology, 120 (1)： 51-70.

Ghaly, A. E., Dave, D., Budge, S., and Brooks, M. S., 2010. Fish spoilage mechanisms and preservation techniques： Review.American Journal of Applied Sciences, 7 (7)： 859-877.

Ghanbari, M., Jami, M., Domig, K. J., and Kneifel, W., 2013. Seafood biopreservation by lactic acid bacteria - A review.LWT-Food Science and Technology, 54 (2)： 315-324.

Gram, L., and Huss, H. H., 1996. Microbiological spoilage of fish and fish products.International Journal of Food Microbiology, 33 (1)： 121-137.

Gram, L., Ravn, L., Rasch, M., Bruhn, J. B., Christensen, A. B., and Givskov, M., 2002. Food spoilage - Interactions between food spoilage bacteria.International Journal of Food Microbiology, 78 (1)： 79-97.

González-Rodr??guez, M. N., Sanz, J. J., Santos, J. á., Otero, A., and Garc??a-López, M. L., 2002. Numbers and types of microorganisms in vacuum-packed cold-smoked freshwater fish at the retail level.International Journal of Food Microbiology, 77 (1)： 161-168.

Grigorakis, K., Taylor, K. D. A., and Alexis, M. N., 2003. Seasonal patterns of spoilage of ice-stored cultured gilthead sea bream (Sparus aurata).Food Chemistry, 81 (2)： 263-268.

Hamada-Sato, N., Usui, K., Kobayashi, T., Imada, C., and Watanabe, E., 2005. Quality assurance of raw fish based on HACCP concept.Food Control, 16 (4)： 301-307.

Hisar, ?. A., Kaban, G., Hisar, O., Yanik, T., and Kaya, M., 2009. Effect ofLactobacillus sakeiLb706 on behavior ofListeria monocytogenesin vacuum-packed rainbow trout fillets.Turkish Journal of Veterinary and Animal Sciences, 29 (4)： 1039-1044.

Katikou, P., Ambrosiadis, I., Georgantelis, D., Koidis, P., and Georgakis, S. A., 2007. Effect of Lactobacillus cultures on microbiological, chemical and odour changes during storage of rainbow trout fillets.Journal of the Science of Food and Agriculture, 87 (3)： 477-484.

Kontham, K. V., Sulochana, P., Leena, D., and Kesavan, M. N., 2014. Control of spoilage fungi by protective lactic acid bacteria displaying probiotic properties.Applied Biochemistry and Biotechnology, 172 (7)： 3402-3413.

Kim, C., and Hearnsberger, J., 1994. Gram negative bacteria inhibition by lactic acid culture and food preservatives on catfish fillets during refrigerated storage.Journal of Food Science, 59 (3)： 513-516.

Kisla, D., and ünlütürk, A., 2004. Microbial shelf-life of rainbow trout fillets treated with lactic culture and lactic acid.Advances in Food Sciences, 26 (1)： 17-20.

Kostrzynska, M., and Bachand, A., 2006. Use of microbial antagonism to reduce pathogen levels on produce and meat products： A review.Canadian Journal of Microbiology, 52：1017-1026.

Lash, B. W., Mysliwiec, T. H., and Gouram, H., 2005. Detection and partial characterization of a broad-range bacteriocin produced byLactobacillus plantarum(ATCC 8014).Food Microbiology, 22： 199-204.

Lin, D., and Morrissey, M. T., 1994. Iced storage characteristicsof Northern squawfish (Ptychocheilus oregonensis).Journal of Aquatic Food Product Technology, 3 (2)： 25-43.

Mehta, R., Arya, R., Goyal, K., Singh, M., and Sharma, K. A., 2013. Bio-preservative and therapeutic potential of pediocin：Recent trends and future perspectives.Recent Patents on Biotechnology, 3： 172-178.

Molinari, L. M., De Oliveira, S. D., Pedroso, R. B., De Lucas Rodrigues Bittencourt, N., Nakamura, C. V., Ueda-Nakamura, T., and Dias Filho, B. P., 2003. Bacterial microflora in the gastrointestinal tract of Nile tilapia (Oreochromis niloticus) cultured in a semi-intensive system.Acta Scientiarum Biological Sciences, 25 (2)： 267-271.

Nyk?nen, A., Weckman, K., and Lapvetel?inen, A., 2000. Synergistic inhibition ofListeria monocytogeneson cold-smoked rainbow trout by nisin and sodium lactate.International Journal of Food Microbiology, 61 (1)： 63-72.

Oca?o-Higuera, V. M., Marquez-Ríos, E., Canizales-Dávila, M., Castillo-Yá?ez, F. J., Pacheco-Aguilar, R., Lugo-Sánchez, M. E., and Graciano-Verdugo, A. Z., 2009. Postmortem changes in cazon fish muscle stored on ice.Food Chemistry, 116 (4)：933-938.

Ozogul, F., Taylor, K. D. A., Quantick, P., and Ozogul, Y., 2000. Chemical, microbiological and sensory evaluation of Atlantic herring (Clupea harengus) stored in ice, modified atmosphere and vacuum pack.Food Chemistry, 71 (2)： 267-273.

Singh, A., Sharma, P. K., and Garg, G., 2010. Natural products as preservatives.International Journal of Pharma and Bio Sciences, 1 (4)： 601-612.

Tamang, J. P., Tamang, B., Schillinger, U., Franz, C. M., Gores, M., and Holzapfel, W. H., 2005. Identification of predominant lactic acid bacteria isolated from traditionally fermented vegetable products of the Eastern Himalayas.International Journal of Food Microbiology, 105 (3)： 347-356.

Valenzuela, A. S., Ruiz, G. D., Omar, N. B., Abriouel, H., López, R. L., Ca?amero, M. M., and Gálvez, A., 2008. Inhibition of food poisoning and pathogenic bacteria byLactobacillus plantarumstrain 2.9 isolated from ben saalga, both in a culture medium and in food.Food Control, 19 (9)： 842-848.

Vazquez-Ortiz, F. A., Pacheco-Aguilar, R., Lugo-Sanchez, M. E., and Villegas-Ozuna, R. E., 1997. Application of the freshness quality index (K value) for fresh fish to canned sardines from Northwestern Mexico.Journal of Food Composition and Analysis, 10 (2)： 158-165.

Yamazaki, K., Suzuki, M., Kawai, Y., Inoue, N., and Montville, T. J., 2003. Inhibition ofListeria monocytogenesin coldsmoked salmon byCarnobacterium piscicolaCS526 isolated from frozen surimi.Journal of Food Protection, 66 (8)： 1420-1425.

(Edited by Ji Dechun)

(Received June 13, 2014; revised February 12, 2015; accepted March 4, 2015)

? Ocean University of China, Science Press and Springer-Verlag Berlin Heidelberg 2015

* Corresponding author. Tel： 0086-20-84451442 E-mail： laihaoli@163.com