Changes in quality of rainbow trout (Oncorhynchus mykiss) fillets preserved with salt and sugar at low concentrations and stored at 4°C

The effects of dry-curing with low concentrations of salt and sugar on the quality of rainbow trout (Oncorhynchus mykiss) fillets were studied over a 16-day storage period at 4°C. Physicochemical characteristics (total volatile base nitrogen (TVB-N), biogenic amines (BAs), ATP-related compounds and K value), microbial populations (total aerobic counts (TAC), H₂S-producing bacteria, Pseudomonas, Aeromonas, and lactic acid bacteria) and sensory (SA) indicators were analyzed. Fish samples were subjected to the following treatments: untreated (control), dry-cured with 1.3% salt (T1), and dry-cured with 1.3% salt that also contained 0.9% sugar (T2). SA indicated that the sensory quality of the control, T1, and T2 was unacceptable after 8, 12, and 12 days of storage, respectively. Moreover, the cadaverine concentration of treated samples was significantly lower (P < 0.05) than the control after storing for 8 days. T1 and T2 were significantly higher (P < 0.05) than the control in inosine 5-monophosphate (IMP) content from the 2th to 10th day. Cadaverine, putrescine, hypoxanthine, and TAC were correlated significantly (P < 0.01) with SA, and these seemed to be reliable indicators of fish quality. The results indicated that curing treatments extended the shelf life of rainbow trout fillets, which could be exploited by processors.     

Effect of gutting on microbiological,chemical, and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting on microbiological, chemical, and sensory properties of aqua-cultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads and H₂S-producing bacteria (including Shewanella putrefaciens) were the dominant bacteria at the end of the 16-day storage period in ice for both whole ungutted and gutted sea bass. Brochothrix thermosphacta and Enterobacteriaceae were also found in the spoilage microflora of ungutted and gutted sea bass but their counts were always less than those of Pseudomonads and H₂S-producing bacteria. Bacterial counts of whole ungutted sea bass were always higher than those obtained for gutted sea bass samples. Mesophilic counts for gutted and ungutted fish exceeded 7 log cfu g⁻¹ after 9 and 15 days of ice storage, respectively. Of the chemical indicators of spoilage, TMA values of ungutted sea bass increased very slowly whereas for gutted samples higher values were obtained reaching a final value of 0.73 and 4.39 mg N 100 g⁻¹, respectively (day 16). TVB-N values showed no significant increase for whole ungutted sea bass during storage reaching a value of 27.7 mg N 100 g⁻¹ (day 16) whereas for gutted fish 36.9 mg N 100 g⁻¹ was recorded. TBA values remained low for ungutted sea bass samples until day 16 of storage, whereas for gutted fish were variable. Of the chemical indices used, none proved useful means of monitoring early ungutted and gutted sea bass freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 5 days for the ungutted sea bass, a grade A for a further 2 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Gutted sea bass was given a grade E for up to 3 days, a grade A for the 4–7th days, and a grade B for the 8–10th days of storage, whereas on day 11 it was graded as unfit. Acceptability scores for odor, taste and texture of cooked ungutted and gutted sea bass decreased with time of storage. Results of this study indicate that the shelf-life of whole ungutted and gutted sea bass stored in ice as determined by the overall acceptability sensory scores and microbiological data is 13 and 8 days, respectively.     

Biochemical,sensory and microbiological attributes of wild turbot (Scophthalmus maximus), from the Black Sea,during chilled storage

Freshness of wild turbot (Scophtalmus maximus) stored in ice was assessed by chemical, sensory and microbiological methods. The limit for sensory acceptability of wild turbot stored in ice was ∼12–15 days. The quality of turbot decreased on day 15 (B) and they were no longer acceptable on day 19 (C). The TVB-N level showed fluctuations during storage, indicating that TVB-N could not be a good indicator of turbot quality. The release of FFA increased from an initial value of 6.33 (expressed as % of oleic acid) to a final value of 20.6 during the storage period. The initial PV value was 5.60 meq/kg for turbot stored in ice and it started to increase to 21.6 meq/kg on day 12 and then started to decrease to 13.6 meq/kg at the end of storage period. The level of TMA in wild turbot increased sharply from an initial value of 9.36 mg/kg to a final value of 38.9 mg/kg. Linear regressions (r²) obtained from K, K_i, G, P, H and F_r were 0.92, 0.89, 0.99, 0.89, 0.96 and 0.89, respectively, for the wild turbot stored in ice. Turbot maintained high (E) and good quality (A) during the first 12 days of chilled storage when the average K, K_i and P values were ∼78–85%, and H, F_r and G values were ∼45%, 15% and 149%, respectively. Eight biogenic amines were investigated, namely, histamine, putrescine, cadaverine, spermidine, spermine, tryptamine, tyramine, and 2-phenylethylamine, three amines (histamine, tyramine, and tryptamine) were not detected in any of the fish samples during the storage period. As storage time progressed, putrescine and cadaverine became the dominant amines, reaching 22.7, and 16.9 mg/kg, respectively, at 19 days of storage in ice. Total viable counts of whole gutted turbot increased from the initial value of 3.3 log cfu g⁻¹ (day 0) to 7.87 log cfu g⁻¹ (day 19) over the period of storage. If 10⁶ microorganisms/g are considered to be the TVC limit of acceptability, the shelf life of turbot was approximately ∼13–14 days.     

Gutted and Un-Gutted Sea Bass (Dicentrarchus Labrax) Stored in Ice: Influence on Fish Quality and Shelf-Life

The sensory characteristics, chemical freshness indicator contents, and microbial counts (total aerobe, psychrotrophic bacteria, H₂S-producing bacteria, and Pseudomonas spp.) of whole un-gutted and gutted sea bass stored in ice were compared. Results of this study indicated that the acceptability quality of whole and gutted sea bass as determined by sensorial data is 11 days, respectively. No significant differences (p > 0.05) were found in the level of sensory score between whole and gutted sea bass samples. Total volatile basic nitrogen (TVB-N) values showed no significant increase for whole and gutted sea bass during storage. Trimethylamin (TMA-N) values of whole and gutted sea bass increased very slowly, reaching final values of 3.94 and, 3.38 mg/100g, respectively (day 13). Development of initial decomposition (after 7 days) occurred when bacterial counts were > 4 log CFU/g. Microbial counts showed a significant increase for whole and gutted sea bass during storage. Significant differences (p < 0.05) were found in the microbial counts between whole and gutted sea bass samples. This difference, may be attributed either to gutting procedures, which most probably were the cause of cross-contamination of fish or to the significantly higher fish flesh surface area exposed to environmental microbial contamination in the case of gutted fish.     

Biogenic amines in vacuum-packed and non-vacuum-packed flesh of carp (Cyprinus carpio) stored at different temperatures

Samples of carp flesh (Cyprinus carpio), vacuum-and non-vacuum-packed were stored at 3 and 15 °C. Chemical, sensory and microbial qualities were measured throughout the storage time to determine the changes that took place and to evaluate the effects of both storage temperature and the means of packaging. Seven biogenic amines (putrescine, cadaverine, spermidine, spermine, histamine, tyramine and tryptamine) were determined. Putrescine and cadaverine showed the best correspondence with the sensory and microbial states of the samples. Low storage temperature had a dominant effect, resulting in low biogenic amine content and better quality of samples. The effect of vacuum-packaging was less obvious, especially in samples kept at 15 °C. Application of vacuum-packaging at 3 °C prolonged the shelf life by about 4–5 days.     

Effects of E‐beam irradiation and vacuum packaging on biogenic amines formation in common carp (Cyprinus carpio) fillets

The effects of vacuum packaging followed by E‐beam irradiation treatment on the shelf life of common carp (Cyprinus carpio) fillets were studied by measuring biogenic amines and sensory analysis. Samples were irradiated at doses of 0.10, 0.50, 1.0 and 2.0 kGy. Putrescine, cadaverine, histamine and tyramine showed very good correspondence with the irradiation dose and the time of storage. Spermine, spermidine, tryptamine and phenylethylamine did not show statistically significant changes with the time of storage. According to the sensory assessment and biogenic amines index (BAI), the shelf life of unirradiated common carp fillets was found to be approximately seven days. The 1 and 2 kGy irradiation doses extended the shelf life of samples up to 66 and 77 days, respectively. High values of correlation coefficients (r < ?0.86) between BAI and sensory evaluation indicated that BAI could be considered as a quality indicator of common carp fillets.     

Hygienic status and biogenic amine content of mung bean sprouts

 Microbiological analyses of commercial mung bean sprouts showed the total, viable microbiological population to exceed 10⁸ cfu/g. Enterobacter cloacae, Klebsiella pneumoniae and Enterobacter agglomerans were found to be the dominant and most frequently isolated microbial species. Putrescine, cadaverine, spermidine and spermine were detected in all samples investigated. Formation of biogenic amines by pure culture isolates was studied in a modified decarboxylase medium at different temperatures, pH values and atmospheres. Highest activities were found under aerobic conditions at 20  °C. K. pneumoniae 861 produced 1.2 mg cadaverine/ml after an incubation period of 24 h and E. cloacae 862 produced 2 mg putrescine/ml after 48 h of incubation. For E. agglomerans 863, no biogenic amines were detected under these conditions. Production of cadaverine by E. cloacae 862 and K. pneumoniae 861 under aerobic conditions is presumably related to lysine decarboxylase activities. Although highest decarboxylase activities have usually been found at acidic pH values, amine production reached a maximum at pH 7. Under anaerobic conditions, E. cloacae 862 produced only about half the amount of putrescine as under aerobic conditions, whilst K. pneumoniae 861 produced significantly less cadaverine but was able to produce putrescine. Received: 10 October 1997 / Revised version: 21 January 1998     

Hygienic status and biogenic amine content of mung bean sprouts

 Microbiological analyses of commercial mung bean sprouts showed the total, viable microbiological population to exceed 10⁸ cfu/g. Enterobacter cloacae, Klebsiella pneumoniae and Enterobacter agglomerans were found to be the dominant and most frequently isolated microbial species. Putrescine, cadaverine, spermidine and spermine were detected in all samples investigated. Formation of biogenic amines by pure culture isolates was studied in a modified decarboxylase medium at different temperatures, pH values and atmospheres. Highest activities were found under aerobic conditions at 20  °C. K. pneumoniae 861 produced 1.2 mg cadaverine/ml after an incubation period of 24 h and E. cloacae 862 produced 2 mg putrescine/ml after 48 h of incubation. For E. agglomerans 863, no biogenic amines were detected under these conditions. Production of cadaverine by E. cloacae 862 and K. pneumoniae 861 under aerobic conditions is presumably related to lysine decarboxylase activities. Although highest decarboxylase activities have usually been found at acidic pH values, amine production reached a maximum at pH 7. Under anaerobic conditions, E. cloacae 862 produced only about half the amount of putrescine as under aerobic conditions, whilst K. pneumoniae 861 produced significantly less cadaverine but was able to produce putrescine. Received: 10 October 1997 / Revised version: 21 January 1998     

BIOGENIC AMINES FORMATION IN SARDINE MARINADE DURING REFRIGERATED STORAGE

Biogenic amines (tyramine, putrescine, cadaverine, histamine, spermidine, spermine) in sardine marinade were investigated. Sardine were beheaded, gutted, filleted, washed and marinated by immersing the fish into solutions containing 2 and 4% acetic acid and 10% NaCl for 24 h. Biogenic amine content, sensory scores and pH values of marinated sardine were recorded during the storage at 4C for up to 5 months. Biogenic amine content in marinated sardine was higher than in raw material. There were significant (P<0.05) differences in biogenic amine content between acetic acid concentrations of 2% and 4% just after marinating. Initial values of biogenic amines in marinade with 4% acetic acid were significantly (P<0.05) lower than those in marinade with 2% acetic acid. The contents of tyramine***, putrescine and histamine in sardine marinade decreased in the first 2–3 months of storage, followed by continuous increase up to 5 months of the storage. After decrease in the first month, cadaverine level did not significantly change. According to results, the marination process influences biogenic amine accumulation.     

Spermine and spermidine concentrations in pork loin as affected by storage, curing and thermal processing

Spermine and spermidine concentrations in pork loin as affected by three factors used in food processing [immersion-curing (10% brine: NaNO₂ and NaCl content of 0.6 and 99.4 g/l, respectively, and 20% brine: NaNO₂ and NaCl content of 0.6 and 199.4 g/l, respectively), boiling and grilling (70 °C core temperature) and storage of raw loin chops (“non-stored” versus storage at 4 °C for 5 days)] were studied. Spermidine and spermine concentrations of the “non-stored” raw loin chops were 2.7±0.7 and 19.8±1.5 mg/kg (fresh weight), respectively. Storage effects were negligible. Curing in 20% brine resulted in statistically significant spermidine decreases as compared to non-cured meat (p=0.04). Statistically significant decreases of spermine were observed for curing in 20% brine as compared with 10% brine (p=0.08), and boiling of meat in an equal amount of water compared to raw meat and grilled meat (p=0.03). Combined curing in 20% brine and cooking in an equal amount of water resulted in 2.0±1.0 mg/kg spermidine and 14.4±2.6 mg/kg spermine. Combined common food processing techniques resulted in a decrease of spermine and spermidine concentrations in pork loin of maximum 26% only. The latter should be considered as relevant for consumers for which the dietary polyamine uptake is critical.     

Establishment of quality predictive models for bighead carp (Aristichthys nobilis) fillets during storage at different temperatures

Quality predictive models were developed to predict the freshness of bighead carp (Aristichthys nobilis) fillets during storage at different temperatures. Quality indices [sensory score, total volatile base nitrogen (TVB‐N), total aerobic counts (TAC) and K value] at ?3, 0, 3, 9 and 15 °C were estimated and kinetically modelled by the Arrhenius equation. The activation energy (E_A) of sensory score, TVB‐N, TAC and K value was 78.17, 75.93, 106.53 and 76.21 kJ mol^?1, and the corresponding rate constants (k₀) were 1.16 × 10¹⁵, 2.60 × 10¹⁴, 4.05 × 10¹⁹ and 1.36 × 10¹⁵. The high regression coefficients (R² > 0.87) indicated the acceptability of the zero‐order reaction for sensory score, TVB‐N, TAC and K value. Relative errors between predicted and observed freshness indicators values of sensory score, TVB‐N, TAC and K value were all below 10% except the values at 6th day of K value, 3rd day and 9th day of TVB‐N. These results indicated that the models based on sensory score, TVB‐N, TAC and K value could effectively predict the freshness indicators of bighead carp fillets at the range of ?3 to 15 °C.     

Influence of modified atmosphere packaging on the chilled shelf life of gutted farmed bass (Dicentrarchus labrax)

The effect of MAP on quality changes of gutted farmed bass when stored at 3 °C were investigated for up to 9 days. Gutted farmed bass was packed with six different atmospheres (0%O₂–70%CO₂; 20%O₂–70%CO₂; 30%O₂–60%CO₂; 40%O₂–60%CO₂; 30%O₂–50%CO₂; 21%O₂–0%CO₂). Headspace gas composition (O₂%; CO₂%), aerobic mesophilic bacteria (AMB) and Enterobacteriaceae, pH, water loss, flesh moisture content, colour, stiffness, odour and eyes appearance were assessed by means of instrumental and sensory analysis after 0, 2, 5, 7 and 9 days of storage. Atmosphere composed of 30% of O₂ and 50% of CO₂ was the best one to preserve the quality of the gutted farmed bass. PCA was an effectively instrument to classify gutted bass samples on the bases of quality changes. The effect of the time was explained by the factor 1, whereas the fish were clearly classified along factor 2 in relation to storage atmosphere.     

Effect of delayed gutting on biogenic amine contents during ripening of European anchovies

The effect of delayed gutting on biogenic amine formation during ripening of European anchovies (Engraulis encrasicholus) was studied. The main difference between the two processes was the use of gutted or ungutted fish in the first step of ripening. Biogenic amines and microbial counts were studied in seven batches of samples taken during manufacturing from fresh anchovies and from anchovies throughout ripening. The formation of amines commonly related to fish spoilage (histamine, tyramine, cadaverine, putrescine and agmatine) was significantly higher in the first step of ripening of batches in ungutted fish. In contrast, no differences were observed between the content of the natural polyamines spermine and spermidine.     

Effects of gamma irradiation on the biogenic amines in pepperoni with different packaging conditions

Combined effects of gamma irradiation and packaging on biogenic amine (BA) formation in pepperoni sausage were investigated during storage. Pepperoni (fermented sausage) was made and packaged with air, vacuum and CO₂/N₂ (25%/75%) gas and then gamma-irradiated at 0, 5, 10 and 20 kGy. The pH was decreased after storage and non-irradiated samples showed a lower pH than irradiated. Lactic acid bacteria (LAB) were not detected after 5 kGy of gamma irradiation, while the LAB in the non-irradiated samples were 4–5 log counts during storage. A total of six different BAs, putrescine, cadaverine, β-phenylethylamine, spermidine, spermine and tyramine, were found in the pepperoni sausage. Detected BAs were statistically low under the irradiation or packaging conditions, except for cadaverine and β-phenylethylamine. Gamma irradiation was effective in reducing putrescine, spermidine, spermine and tyramine. Irradiation effects were not observed on the β-phenylethylamine level, while the CO₂/N₂ packaging caused increasing of the level. Most BAs detected were reduced by gamma irradiation of the pepperoni sausage during storage. However, CO₂/N₂ packaging was an improper condition for BA reduction in the pepperoni sausage.     

Production of Biogenic Amines and Their Potential Use as Quality Control Indices for Hake (Merluccius merluccius, L.) Stored in Ice

ABSTRACT: The production of tyramine, histamine, putrescine, cadaverine, agmatine, and spermidine was studied for use as quality indices in muscle of gutted hake stored in ice for 25 d. The changes in biogenic amine concentrations were correlated with trimethylamine nitrogen levels. All concentrations except for spermidine, increased progressively throughout storage. During storage, cadaverine reached 72.14 mg/kg while there were no significant increases in histamine and tyramine. The levels of free amino acids, which may be metabolized into biogenic amines, were not correlated to respective biogenic amines levels. The production of cadaverine and agmatine occurred prior to spoilage and these biogenic amines may indicate freshness of hake stored in ice.     

Quality assessment of whole and gutted sardines (Sardina pilchardus) stored in ice

The quality and shelf life of whole ungutted and gutted sardines ( Sardina pilchardus ) stored in ice were studied. The changes in the fish were investigated by sensory assessments, chemical analyses and microbiological analyses. The sensory scores of uneviscerated and gutted sardines stored in ice at +4 °C were 7 days. The chemical indicators of spoilage, total volatile basic nitrogen and trimethylamine values of gutted sardine increased very slowly, whereas for whole ungutted samples higher values were obtained reaching a final value of 15.03–29.23 mg per 100 g and 2.36–4.16 mg per 100 g, respectively (day 9). Peroxide and thiobarbituric acid values remained lower for whole ungutted sardine samples until day 9 of storage, whereas for gutted fish were higher. The level of histamine exceeded the legal limit in whole ungutted sardine after 7 days of storage in ice, during which sardines were rejected by the sensory panel. Mesophilic aerobic bacteria count, H₂S-producing bacteria, sulphide reducing anaerobe Clostridias, Enterobacteriaceae count of whole ungutted sardine samples are higher than gutted sardine samples during the storage. Psychrotrophic bacteria counts of the two groups were not different. The limits of microbiological data were not exceeded throughout the storage in both the groups' samples.     

Stimulation of Cadaverine Production by Foodborne Pathogens in the Presence of Lactobacillus,Lactococcus, and Streptococcus spp.

Abstract: The effect of Lactobacillus plantarum (FI8595), Lactococcus lactis subsp. cremoris MG 1363), Lactococcus lactis subsp. lactis (IL 1403), and Streptococcus thermophilus on cadaverine and other biogenic amine production by foodborne pathogens was investigated lysine decarboxylase broth. Both of lactic acid bacteria and foodborne pathogens used (especially Staphylococcus aureus, E. coli, Lc. lactis subsp. lactis and Lb. plantarum) had an ability to convert aminoacids into biogenic amine. The conversion of lysine into cadaverine was the highest (167.11 mg/L) by Lactobacillus spp. Gram‐positive bacteria generally had a greater ability to produce cadaverine with corresponding value of 46.26, 53.76, and 154.54 mg/L for Enterococcus faecalis, S. aureus, and Listeria monocytogenes, respectively. Significant variations on biogenic amine production were observed in the presence of lactic acid bacteria strains (P < 0.05). The role of lactic acid bacteria on biogenic amine production by foodborne pathogens varied depending on strains and specific amine. Cadaverine accumulation by Enterobactericeae was increased in the presence of lactic acid bacteria strains except for St. thermophilus, which induced 2‐fold lower cadaverine production by S. Paratyphi A. Lc. lactis subsp. lactis and Lc. lactis subsp. cremoris induced 10‐fold higher increases in histamine for E. coli and K. pneumoniae, respectively. Lactic acid bacteria resulted in strong increases in cadaverine production by P. aeruginosa, although remarkable decreases were observed for histamine, spermidine, dopamine, agmatine, and TMA in the presence of lactic acid bacteria in lysine decarboxylase broth . The result of the study showed that amine positive lactic acid bacteria strains in fermented food led to significant amine accumulation by contaminant bacteria and their accumulation in food product may be controlled by the use of proper starters with amine‐negative activity. Practical Application: Foodborne pathogens and certain lactic acid bacteria are particularly active in the production of biogenic amines. Most of the strains of bacteria possess more than 1 amino acid decarboxylase activity under lysine enrichment culture conditions. Lactic acid bacteria strains had a significant role on increase putrescine accumulation by foodborne pathogens. The increased production of biogenic amines in mixed culture is the result of presence of amine positive lactic acid bacteria strains. The addition of a proper selected starter culture with amine‐negative activity is advisable to produce safer fermented food with low contents of biogenic amines.     

Determination of Biogenic Amines in Sichuan-Style Spontaneously Fermented Sausages

The qualitative and quantitative profile of biogenic amines in 30 samples of Sichuan-style spontaneously fermented sausages sold in Sichuan retail markets was studied by HPLC. Tryptamine, phenylethylamine, putrescine, cadaverine, histamine, tyramine, and spermidine were analyzed by UV detection after pre-column derivatization with dansyl chloride. There were wide ranges of different biogenic amines in the samples, except spermidine. The results showed that the histamine was the major biogenic amines, followed by tyramine and cadaverine, which have a mean value of 196.06 mg/kg (ranging from 114.33 to 327.35 mg/kg), 164.67 mg/kg (ranging from 88.84 to 285.89 mg/kg), and 141.65 mg/kg (ranging from 19.14 to 376.46 mg/kg), respectively. The toxicity limit of histamine is 100 mg/kg, where all of the samples exceeded this limit. None of the samples of total biogenic amines content exceeded 1000 mg/kg. The results showed that the amounts of biogenic amines in Sichuan-style spontaneously fermented sausages sold in Sichuan retail markets may pose a potential health risk for sensitive individuals. This suggested that it is necessary to improve the production techniques and the raw materials’ hygienic quality, to ensure the quality and safety of this fermented sausages with respect to their biogenic amine content.     

Physicochemical and microbiological changes in postmortem crayfish (Procambarus clarkii) stored at 4 °C and 25 °C

The physicochemical and microbiological parameters of postmortem crayfish stored at 4 °C and 25 °C were evaluated in order to reduce safety risks of crayfish from temperature abuse during transportation and storage. Results showed that hepatopancreas of postmortem crayfish had significantly higher contents of total volatile basic nitrogen, biogenic amines (BAs) and higher microbial loads than tail meat, regardless of storage temperature. Enterobacteriaceae and Pseudomonas counts reached log 6.41 log₁₀ CFU g⁻¹ and 6.31 log₁₀ CFU g⁻¹ in hepatopancreas of crayfish at 25 ℃ for 6 h. Putrescine and cadaverine were the main BAs in tail meat with levels of 28.18 ± 0.73 mg kg⁻¹ and 187.32 ± 3.57 mg kg⁻¹, respectively, whilst cadaverine, spermidine and spermine were the major BAs in hepatopancreas, reaching 283.45 ± 3.95 mg kg⁻¹, 62.87 ± 9.02 mg kg⁻¹ and 155.31 ± 4.55 mg kg⁻¹, respectively, after postmortem storage at 25 °C for 12 h. With time increasing, Acinetobacter, Flavobacterium, Aeromonas and Chryseobacterium at 25 °C and Acinetobacter, Flavobacterium, Psychrobacter at 4 °C in tail meat as well as Bacteroides and Muribaculaceae at 25 °C, and Acinetobacter, Psychrobacter at 4 °C in hepatopancreas, gradually became the major genus at the end of storage. Based on the results of spoilage microorganisms and biogenic amines, crayfish stored at 4 °C and 25 °C could be edible within 24 h and 6 h, respectively.     

Determination of biogenic amines in Japanese miso products

Eight miso products sold in supermarket were purchased from Japan and analyzed for the determination of biogenic amines (BAs). Quantitative determination of BAs in miso products was carried out by means of HPLC with spectrophotometric UV-VIS detector. The amines were extracted in acid aqueous solution (HClO₄) and then derivatized by dansyl chloride. The levels of pH in the tested miso samples were ranged from 4.8–5.5. The BAs (tryptamine, 2-phenyl ethylamine, putrescine, cadaverine, agmatine, tyramine, and spermidine) determined in 8 miso samples were found in their respective range of ND-0.13, ND-4.20, ND-1.29, ND-0.87, ND-0.90, ND-4.19, and ND-3.57 mg%. None of the miso samples contained histamine and spermine, the major BAs of food poisoning.