Bacteriological Quality of Tuna Fish ( Thunnus thynnus ) Destined for Canning: Effect of Tuna Handling on Presence of Histidine Decarboxylase Bacteria and Histamine Level

Microbiota diversity of three Brazilian native fishes during ice and frozen storage

This study aimed to assess the bacterial microbiota involved in the spoilage of pacu (Piaractus mesopotamics), patinga (female Piaractus mesopotamics x male Piaractus brachypomus), and tambacu (female Colossoma macropomum × male Piaractus mesopotamics) during ice and frozen storage. Changes in the microbiota of three fish species (N = 22) during storage were studied through 16S rRNA amplicon-based sequencing and correlated with volatile organic compounds (VOCs) and metabolites assessed by nuclear magnetic resonance (NMR). Storage conditions (time and temperature) affected the microbiota diversity in all fish samples. Fish microbiota comprised mainly of Pseudomonas sp., Brochothrix sp., Acinetobacter sp., Bacillus sp., Lactiplantibacillus sp., Kocuria sp., and Enterococcus sp. The relative abundance of Kocuria, P. fragi, L. plantarum, Enterococcus, and Acinetobacter was positively correlated with the metabolic pathways of ether lipid metabolism while B. thermosphacta and P. fragi were correlated with metabolic pathways involved in amino acid metabolism. P. fragi was the most prevalent spoilage bacteria in both storage conditions (ice and frozen), followed by B. thermosphacta. Moreover, the relative abundance of identified Bacillus strains in fish samples stored in ice was positively correlated with the production of VOCs (1-hexanol, nonanal, octenol, and 2-ethyl-1-hexanol) associated with off-flavors. 1H NMR analysis confirmed that amino acids, acetic acid, and ATP degradation products increase over (ice) storage, and therefore considered chemical spoilage index of fish fillets.

Investigation of Biogenic Amine Levels and Microbiological Activity as Quality Markers in Some Dairy and Fish Products in Food Markets in the Kingdom of Saudi Arabia

This study aimed to verify the presence of biogenic amines (BAs) and evaluate the microbiological activity of some food samples collected from retail stores in the Kingdom of Saudi Arabia. A total of thirty-five dairy and fish products were collected and analyzed for BAs, including putrescine (PUT), cadaverine (CAD), spermidine (SPE), histamine (HIS), spermine (SPR), and tyramine (TYR), as well as for total colony count (TCC), lactic acid bacteria (LAB), Enterobacteriaceae, yeast and mold (Y and M), coliforms, and aerobic sporulation count (ASF). The thin layer chromatography (TLC) method was used in the analytical methodology to identify the BAs. The results showed the presence of BAs in all dairy products, but their concentration did not exceed the maximum permissible limit, which in contrast was established by the Food and Drug Administration (FDA) at 10 mg/100 g. The amounts of BAs in fish products varied significantly. All fish product samples contained levels of BAs below the permissible limit. Results of an independent study also indicated potential toxicity at levels of BAs (>10 mg/100 g) in Egyptian herring. Enterobacteriaceae and the coli group were present in higher concentrations in the Egyptian herring samples, whereas other samples (particularly frozen shrimp) showed increased TCC levels with a higher concentration of histamine-producing bacteria. From a consumer safety perspective, this study also indicated that food samples generally contained acceptable levels of BAs. In conclusion, there is a need to improve and standardize food quality and hygiene practices during production and storage to ensure human safety and prevent HIS formation.

Effects of Environmental and Water Quality Variables on Histamine-Producing Bacteria Concentration and Species in the Northern Gulf of Mexico

Scombrotoxin (histamine) fish poisoning is a common seafood-borne illness attributed to toxin production by histamine-producing bacteria (HPB) in fish tissues during decomposition. In laboratory studies, growth of HPB and other bacterial species is affected by physical and chemical attributes, but natural communities of HPB are not well understood. To determine how in situ environmental and water quality variables may affect density of HPB in the natural aquatic environment, we compared presence and abundance of HPB to ambient temperature, salinity, dissolved oxygen, fecal coliforms, male-specific coliphage, nutrient concentrations, carbon and nitrogen stable isotope ratios, and C:N in water samples collected from July 2017 to February 2018 along a natural salinity gradient in a tidal river on the coast of northern Gulf of Mexico. HPB in water samples were quantified using a real-time PCR, most probable number method. HPB species were identified via 16S rRNA gene sequences. Temperature and salinity were determined to be the main factors driving HPB presence and concentration. Canonical correspondence analysis revealed that different HPB were associated with different environmental conditions. Photobacterium damselae was found under warmer, higher-salinity conditions; Raoultella planticola was found at colder, lower-salinity conditions; Enterobacter aerogenes was found at warmer, lower-salinity conditions; and Morganella morganii was found at most sites, independent of environmental conditions. These results showed that naturally occurring HPB abundance and species composition can be affected by environmental conditions, which could manifest in various potentials for histamine formation and scombrotoxin fish poisoning risk based on environmental factors. IMPORTANCE This study determined the effects of environmental conditions on presence and abundance of naturally occurring histamine-producing bacteria in the northern Gulf of Mexico. Here, we show that HPB abundance and species composition are related to in situ ambient temperature and salinity, with the magnitude of this effect dependent on the particular HPB species. This finding suggests that environmental conditions at fishing sites could affect the risk of human illness from scombrotoxin (histamine) fish poisoning.

Prevalence of Histamine-Forming Bacteria in Two Kinds of Salted Fish at Town Markets of Guangdong Province of South China

ABSTRACT

Histamine-forming bacteria (HFB) were isolated from the 70 salted fish samples bought from town markets of Guangdong Province of south China. In addition, the histamine-forming ability of HFB was analyzed. There were 31 strains of HFB isolated from 36 salted fish pickled overnight. They were identified as six bacteria species: Vibrio alginolyticus, Vibrio rumoiensis, Staphylococcus saprophyticus, Staphylococcus xylosus, Lactococcus lactis, and Morganella morganii. The rate of confirmation of V. alginolyticus was highest (23 of 31), exceeding 200 mg/kg histamine. In particular, M. morganii produced a histamine amount that exceeded 2,000 mg/kg, although it was only one isolate in this study. In addition, five bacteria species of HFB were isolated from 34 dried salted fish. Among them, S. saprophyticus was dominant in the dried salted fish but produced histamines below 200 mg/kg. However, Enterobacter aerogenes from dried salted fish formed a histamine amount exceeding 200 mg/kg. The study showed that the dominant strain of HFB was different in two kinds of salted fish. Both kinds of salted fish contained HFB whose histamine-forming capacity exceeded 200 mg/kg. As a result, the safety of salted fish should be of concern, especially salted fish pickled overnight.

HIGHLIGHTS

Histamine Fish Poisoning and Histamine Production by Raoultella ornithinolytica in Milkfish Surimi

ABSTRACT

In April 2017, an outbreak of histamine fish poisoning causing illness in nine victims associated with consumption of milkfish surimi products (fish ball) occurred in Kaohsiung City, southern Taiwan. Of the two suspected frozen milkfish surimi samples, one sample contained 91.06 mg/100 g of histamine, levels that are greater than the potential hazard action level (50 mg/100 g) in most illness cases. Moreover, 28 frozen milkfish surimi samples from retail stores were collected and tested to determine the occurrence of histamine. One (3.6%) of 28 commercial surimi samples had histamine levels greater than the U.S. Food and Drug Administration (FDA) guideline for decomposition of 5 mg/100 g for scombroid fish and/or products. Thirteen histamine-producing bacterial strains isolated from suspected and commercial surimi samples were identified as prolific histamine formers, able to produce 98.4 to 121.8 mg/100 mL of histamine in Trypticase soy broth supplemented with 1.0% l-histidine. In addition, milkfish surimi was inoculated with Raoultella ornithinolytica at 5.0 log CFU/g and stored at 4, 15, 25, and 37°C to investigate bacterial growth and formation of histamine. The histamine contents quickly increased to more than 50 mg/100 g in samples stored at 37 and 25°C within 12 and 24 h, respectively, as well those stored at 15°C within 96 h. To our knowledge, this is the first report in Taiwan to demonstrate that milkfish surimi products could cause histamine intoxication.

HIGHLIGHTS

The use of the so-called 'tubs' for transporting and storing fresh fishery products

On-land transport/storage of fresh fishery products (FFP) for up to 3 days in 'tubs' of three-layered poly-ethylene filled with freshwater and ice was compared to the currently authorised practice (fish boxes of high-density poly-ethylene filled with ice). The impact on the survival and growth of biological hazards in fish and the histamine production in fish species associated with a high amount of histidine was assessed. In different modelling scenarios, the FFP are stored on-board in freshwater or seawater/ice (in tubs) and once on-land they are 'handled' (i.e. sorted or gutted and/or filleted) and transferred to either tubs or boxes. The temperature of the FFP was assumed to be the most influential factor affecting relevant hazards. Under reasonably foreseeable 'abusive' scenarios and using a conservative modelling approach, the growth of the relevant hazards (i.e. Listeria monocytogenes, Aeromonas spp. and non-proteolytic Clostridium botulinum), is expected to be < 0.2 log10 units higher in tubs than in boxes after 3 days when the initial temperature of the fish is 0°C ('keeping' process). Starting at 7°C ('cooling-keeping' process), the expected difference in the growth potential is higher (< 1 log10 for A. hydrophila and < 0.5 log10 for the other two hazards) due to the poorer cooling capacity of water and ice (tub) compared with ice (box). The survival of relevant hazards is not or is negligibly impacted. Histamine formation due to growth of Morganella psychrotolerans under the 'keeping' or 'cooling-keeping' process can be up to 0.4 ppm and 1.5 ppm higher, respectively, in tubs as compared to boxes after 3 days, without reaching the legal limit of 100 ppm. The water uptake associated with the storage of the FFP in tubs (which may be up to 6%) does not make a relevant contribution to the differences in microbial growth potential compared to boxes.

Monitoring the Levels of Biogenic Amines in Canned Fish Products Marketed in Ghana

An ion-pair HPLC method with postcolumn o-phthalaldehyde (OPA) derivatization and fluorescence detection was validated for quantitative determination of five biogenic amines (histamine, tyramine, cadaverine, putrescine, and agmatine) in canned fish products (mackerel, sardine, and tuna) marketed in Ghana. The validated method exhibited excellent selectivity and good linearity (R2 > 0.9990) for all the amines. The limits of detection and quantification for studied biogenic amines were in the range of 0.32–0.78 mg·kg−1 and 1.10–2.57 mg·kg−1, respectively. Also, a satisfactory recovery was obtained for all the amines (82.1–101.4%), and the relative standard deviations were lower than 9.3% under repeatability conditions for the studied amines. Subsequently, the method was applied to the analysis of biogenic amines in canned fish products to estimate the safety of Ghanaian consumers. The maximum levels of histamine, tyramine, cadaverine, putrescine, and agmatine detected in the analysed canned fish products were 64.05 mg·kg−1, 27.44 mg·kg−1, 27.23 mg·kg−1, 18.74 mg·kg−1, and 52.72 mg·kg−1, respectively. Thus, the levels of biogenic amines detected in the canned fish products were lower than the acceptable levels and, therefore, can be considered relatively safe for human consumption.

Determination of Histamine in Japanese Spanish Mackerel (Scomberomorus niphonius) Meat Implicated in a Foodborne Poisoning

An incident of foodborne poisoning causing illness in seven victims due to ingestion of fried Japanese Spanish mackerel (JS mackerel; Scomberomorus niphonius) meat occurred in September 2014 in Hualien County, eastern Taiwan. Of the two suspected fish meats, one raw sample contained 3,318 ppm of histamine and one fried sample contained 1,906 ppm of histamine, levels which are greater than the potential hazard action level (500 ppm) in most illness cases. Given the allergy-like symptoms of the victims and the high histamine content in the suspected fish samples, this foodborne poisoning was strongly suspected to be caused by histamine intoxication. In addition, five histamine-producing bacterial strains isolated from suspected raw fish samples, capable of producing 152 to 1,020 ppm of histamine in Trypticase soy broth supplemented with 1.0% l-histidine, were identified as Hafnia alvei (one strain), Enterobacter aerogenes (two strains), Raoultella ornithinolytica (one strain), and Morganella morganii (one strain) by 16S rDNA sequencing with PCR amplification. Moreover, 12 raw fish samples and 39 fried fish samples from retail stores were collected and tested to determine the occurrence of histamine. Two of 12 commercial raw fish samples (16.7%) had histamine levels greater than the U.S. Food and Drug Administration guideline for decomposition of 50 ppm for scombroid fish or product or a combination of both. To our knowledge, this is the first report in Taiwan to demonstrate that the JS mackerel meat products could cause histamine intoxication.

Molecular Characterization of Histamine-Producing Psychrotrophic Bacteria Isolated from Red Octopus (Octopus maya) in Refrigerated Storage

The present study aimed at determining the histamine production capacity of Gram (+) and Gram (-) bacteria isolated from Octopus maya, along with identifying the presence of amino acid decarboxylase genes. Of the total 80 psychrotrophic microorganisms, 32 strains were identified as histamine-forming bacteria. The recombinant DNA technique was used for genotypic identification of histidine (hdc), ornithine (odc), and lysine decarboxylases (ldc) genes. Thirty-two strains were able to produce 60⁻100 ppm in trypticase soy broth with 1.0% l-histidine after 6 h at 20 °C. NR6B showed 98% homology with Hafnia alvei. NR73 represented 18.8% of the total isolates and showed 98% homology with Enterobacter xianfengensis and Enterobacter cloacae. NR6A represented 6% of the total isolates, which were identified as Lactococcus sp. The hdc gen from NR6B showed 100% identity with hdc from Morganella morganii; ldc showed 97.7% identity with ldc from Citrobacter freundii. The Odc gene was detected only in NR73 and showed 100% identity with Enterobacter sp. All the isolated were identified as weak histamine⁻former. The ingestion of a food containing small amounts of histamine has little effect on humans; however, the formation of biogenic amines is often considered as an indicator of hygienic quality; this emphasizes the importance of improving good management practices and storage.

Effect of Different Cooking Methods on Histamine Levels in Selected Foods

BACKGROUND

Histamine in food is known to cause food poisoning and allergic reactions. We usually ingest histamine in cooked food, but there are few studies about the influence of cooking method on the histamine level.

OBJECTIVE

The purpose of this study was to determine the influence of cooking methods on the concentration of histamine in foods.

METHODS

The foods chosen were those kinds consumed frequently and cooked by grilling, boiling, and frying. The histamine level of the food was measured using enzyme-linked immunosorbent assay.

RESULTS

Grilled seafood had higher histamine levels than raw or boiled seafood. For meat, grilling increased the histamine level, whereas boiling decreased it. For eggs, there was not much difference in histamine level according to cooking method. Fried vegetables had higher histamine levels than raw vegetables. And fermented foods didn't show much difference in histamine level after being boiled.

CONCLUSION

The histamine level in food has changed according to the cooking method used to prepare it. Frying and grilling increased histamine level in foods, whereas boiling had little influence or even decreased it. The boiling method might be helpful to control the effect of histamine in histamine-sensitive or susceptible patients, compared with frying and grilling.

Hygienic quality, adulteration of pork and histamine production by Raoultella ornithinolytica in milkfish dumpling

Ten milkfish dumpling products purchased from retail stores in southern Taiwan were collected to determine the occurrence of biogenic amines, histamine-forming bacteria, and adulteration of pork. This study showed the high contents of aerobic plate count (APC), total coliforms (TC) and Escherichia coli in tested milkfish dumpling samples, whereas the average content of various biogenic amines in all tested samples was < 1.6 mg/100 g (< 0.05 to 1.54 mg/100 g). Three histamine-producing bacterial strains (2 isolates of Raoultella ornithinolytica and 1 isolate of Enterobacter aerogenes) isolated from tested samples produced 276.6 ppm to 561.8 ppm of histamine in trypticase soy broth supplemented with 1.0% L-histidine (TSBH). Assay of multiplex polymerase chain reaction (PCR) revealed that the adulteration rates were 50% (5/10) for pork in milkfish dumplings. In addition, milkfish dumpling stuffing was inoculated with R. ornithinolytica at 5.0 log colony forming units (CFU)/g and stored at various temperatures from 4°C to 37°C to investigate bacterial growth and formation of histamine. The histamine contents quickly increased to higher than 50 mg/100 g in samples stored at 37°C and 25°C within 24 hours and 36 hours, respectively, as well as stored at 15°C within 48 hours. Therefore, bacterial growth and histamine formation were controlled by cold storage of the samples at 4°C.

Review: Loss of Quality during the Manufacture of Canned Fish Products

From the moment the fish is caught till it arrives at the consumer as a canned product, raw matter is submitted to a variety of industrial steps. Thus, a storage process (namely, chilling or freezing) is needed for holding the raw material to be canned; a cooking step is normally employed for reducing moisture and inactivating endogenous enzyme activity; a rigorous thermal treatment (sterilization) is undertaken to inactivate micro-organisms; and a proper canned storage is necessary to guarantee good palatability of the product. As a result, labile and essential nutrients (proteins, vitamins, lipids, minerals) present in the raw fish are exposed to different processing conditions that can reduce the nutritional and sensory values of the final product. In the present work, detrimental changes produced in each of the steps involved in the manufacture of canned products are mentioned. This review is focused on nutritional and sensory losses in species commonly employed for canning preparation, and special attention is given to research concerning the effect of varying conditions of previous processing (chilling, freezing and frozen storage and cooking) on the quality of the final canned product. New and current technological strategies are recommended to increase the shelf life of previously stored material and to retain sensory and nutritional quality in the final canned product.

Histamine development and bacterial diversity in microbially-challenged tonggol (Thunnus tonggol) under temperature abuse during canning manufacture

Histamine formation and bacteriological changes caused by temperature abuse commonly occurring in the manufacturing process of standard canned tuna was assessed in microbiologically challenged tonggol (Thunnus tonggol). The in situ challenge was performed by water-soaking at 26-28 °C for 7 h to ensure the multiplication and active phase of fish microflora. Right after pre-cooking to back-bone temperature (BBT) of 50-52 °C, histamine dropped to 5.17 ± 2.71 ppm, and slowly reached 6.84 ± 1.69 ppm at 16 h abuse. On the contrary, histamine was reduced to 2.87 ± 1.23 ppm and eventually reached 5.01 ± 1.32 ppm at 24 h abuse in the pre-cooked fish previously frozen. The numbers of total aerobic bacteria, Enterobactericeae, psychrotroph, histamine forming bacteria (HFB) and diversity of fish microflora were revealed by cultural and nested PCR-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) techniques. Interestingly, frozen storage effectively halted histamine formation in raw fish throughout 16 h abuse despite the presence of HFB. These included the prolific strains of Morganella morganii, Proteus penneri, Proteus mirabilin, Citrobacter spp. The nested PCR-DGGE profile confirmed the presence of M. morganii and Citrobacter spp. in raw fish. These prolific strains were hardly observed in the precooked fish previously frozen. Frozen storage did not only promote even histamine distribution throughout fish muscle but also enhanced histamine loss during thawing and pre-cooking. Therefore, pre-cooking and frozen storage were proven to be the effective combined hurdles not only to reduce but also prolong histamine formation of the challenged toggol throughout 24 h of temperature abuse during canning process.

Determination of histamine in milkfish stick implicated in food-borne poisoning

An incident of food-borne poisoning causing illness in 37 victims due to ingestion of fried fish sticks occurred in September 2014, in Tainan city, southern Taiwan. Leftovers of the victims' fried fish sticks and 16 other raw fish stick samples from retail stores were collected and tested to determine the occurrence of histamine and histamine-forming bacteria. Two suspected fried fish samples contained 86.6 mg/100 g and 235.0 mg/100 g histamine; levels that are greater than the potential hazard action level (50 mg/100 g) in most illness cases. Given the allergy-like symptoms of the victims and the high histamine content in the suspected fried fish samples, this food-borne poisoning was strongly suspected to be caused by histamine intoxication. Moreover, the fish species of suspected samples was identified as milkfish (Chanos chanos), using polymerase chain reaction direct sequence analysis. In addition, four of the 16 commercial raw milkfish stick samples (25%) had histamine levels greater than the US Food & Drug Administration guideline of 5.0 mg/100 g for scombroid fish and/or products. Ten histamine-producing bacterial strains, capable of producing 373-1261 ppm of histamine in trypticase soy broth supplemented with 1.0% L-histidine, were identified as Enterobacter aerogenes (4 strains), Enterobacter cloacae (1 strain), Morganella morganii (2 strains), Serratia marcescens (1 strain), Hafnia alvei (1 strain), and Raoultella orithinolytica (1 strain), by 16S ribosomal DNA sequencing with polymerase chain reaction amplification.

Interactions between accumulated copper, bacterial community structure and histamine levels in crayfish meat during storage

BACKGROUND

Pollution in aquaculture areas may negatively impact edible species and threaten seafood quality and safety. The aim of this study was to determine the interaction between copper and bacteria in the aquatic habitat and their impact upon crustaceans. Marbled crayfish was chosen as a model of aquatic crustaceans and the influence of metal contamination on bacterial community structure in water used to culture crayfish and in crayfish themselves was investigated. Histamine, an allergen commonly formed by certain groups of bacteria in crustacean edible tissue during storage, was also determined.

RESULTS

Copper exposure increased its concentration in crayfish meat by 17.4%, but the copper concentration remained within acceptable food safety limits. Elevated copper levels affected the bacterial community both in the water used to cultivate crayfish and in the marbled crayfish themselves. Cluster analysis of 16S rRNA-gene based microbial community fingerprints revealed that copper impacted the bacterial community in the water and in the crayfish meat. However, copper exposure reduced the formation of histamine in crayfish meat during storage by 66.3%.

CONCLUSION

Copper from the habitat appears to reduce histamine accumulation in crayfish meat during storage by affecting the bacterial community structure of the cultivation water and most likely also in the intestine of the crayfish. From a food safety point of view, copper treatment during the aqua culturing of crustaceans has a positive impact on the postharvest stage.

Determination and frying loss of histamine in striped marlin fillets implicated in a foodborne poisoning

An incident of foodborne poisoning causing illness in 67 victims due to ingestion of fried fish fillets occurred in June 2011, in southern Taiwan. Of the five suspected fish fillets, one fried sample contained 62.0 mg/100 g and one raw sample contained 89.6 mg/100 g histamine, levels which are greater than the potential hazard action level (50 mg/100 g) in most illness cases. Given the allergy-like symptoms of the victims and the high histamine content in the suspected fish samples, this foodborne poisoning was strongly suspected to be caused by histamine intoxication. Five histamine-producing bacterial strains capable of producing 59 to 562 ppm of histamine in Trypticase soy broth supplemented with 1.0% L-histidine were identified as Enterobacter aerogenes (two strains), Raoultella ornithinolytica (two strains), and Morganella morganii (one strain). The degradation loss of histamine in suspected raw fillets was 28% after they were fried at 170°C for 5 min.

Histamine levels in commercially important fresh and processed fish of Oman with reference to international standards

Histamine was investigated in fresh (378), frozen (441), canned (290) and dried (24) fish samples of scombroid and non-scombroid species of Oman using a high performance liquid chromatography with a fluorescence detector. Of the 1133 fish samples tested, histamine was detected in 551 samples with a detection rate of about 41.8% among fresh fish, 61.0% of frozen fish, 78.9% of canned fish and 91.6% of dried fish samples and the mean histamine levels were 2.6, 5.8, 3.1 and 104mgkg(-1), respectively. A total of 3.7% and 0.79% of the total samples exceeded the FDA and EU regulatory limits for histamine. Imported dried anchovies contained high histamine levels. The study confirms that post catching and commercialisation practices of seafood are adequate, warranting good quality fish and may not cause histamine risk to consumer in terms of human diet. While necessary monitoring may be done for imported dried fish products.

Scombroid poisoning: a review

Scombroid poisoning, also called histamine fish poisoning, is an allergy-like form of food poisoning that continues to be a major problem in seafood safety. The exact role of histamine in scombroid poisoning is not straightforward. Deviations from the expected dose-response have led to the advancement of various possible mechanisms of toxicity, none of them proven. Histamine action levels are used in regulation until more is known about the mechanism of scombroid poisoning. Scombroid poisoning and histamine are correlated but complicated. Victims of scombroid poisoning respond well to antihistamines, and chemical analyses of fish implicated in scombroid poisoning generally reveal elevated levels of histamine. Scombroid poisoning is unique among the seafood toxins since it results from product mishandling rather than contamination from other trophic levels. Inadequate cooling following harvest promotes bacterial histamine production, and can result in outbreaks of scombroid poisoning. Fish with high levels of free histidine, the enzyme substrate converted to histamine by bacterial histidine decarboxylase, are those most often implicated in scombroid poisoning. Laboratory methods and screening methods for detecting histamine are available in abundance, but need to be compared and validated to harmonize testing. Successful field testing, including dockside or on-board testing needed to augment HACCP efforts will have to integrate rapid and simplified detection methods with simplified and rapid sampling and extraction. Otherwise, time-consuming sample preparation reduces the impact of gains in detection speed on the overall analysis time.

Changes in histamine and microbiological analyses in fresh and frozen tuna muscle during temperature abuse

Temperature abuse of tuna (Thunnus alalunga) was carried out in order to assess the histamine buildup in fish-processing facilities where fish can be exposed to high temperatures for short periods of time. Histamine production was studied in tuna loins under different storage and abuse conditions. Tuna was stored at 0-2 degrees C, 3-4 degrees C, and 6-7 degrees C, and abused for 2 h daily at 20 degrees C and 30 degrees C for 7-12 days. Loins abused at 30 degrees C for 2 h daily contained potentially toxic histamine concentrations (67-382 mg kg(-1)) when stored at a low refrigeration temperature (0-2 degrees C), whereas when stored at 6-7 degrees C, the loins contained highly toxic histamine concentrations (544.5-4156.6 mg kg(-1)). Lower histamine concentrations (23-48 mg kg(-1) in loins stored at 0-2 degrees C and 124.7-2435.8 mg kg(-1) in loins stored at 6-7 degrees C) were observed in temperature-abused loins that were initially frozen. An increase over time was observed in most microbial counts tested. Bacteria isolated from the temperature-abused loins showed a varied ability of histamine production, with Morganella morganii, Klebsiella oxytoca, Staphylococcus hominis, and Enterococcus hirae being the most active histamine-producing bacteria.

Evaluation of PCR-single-strand conformational polymorphism analysis for identification of gram-negative histamine-producing bacteria isolated from fish

In this study, the previously established PCR-single-strand conformation polymorphism (SSCP) system for detecting and identifying gram-negative histamine-producing bacteria was evaluated. This system can detect and identify histamine-producing bacteria directly from seafood by the use of sequence polymorphisms of the histidine decarboxylase gene (hdc). First, we isolated 81 histamine-producing strains of bacteria from fish samples and analyzed the hdc gene by the PCR-SSCP system. The 22 newly obtained SSCP banding patterns were added to our database, and the utility of our modified database was tested in a second experiment consisting of 18 strains of histamine-producing bacteria isolated from 25 fish samples. Approximately 80% of the histamine-producing strains corresponded to those in the new database. Use of the database for PCR-SSCP analysis, including the band patterns newly added in this study, for the hdc gene makes it possible to more accurately identify histamine producers.