EFFECT OF PROCESSING ON BACTERIAL POPULATION OF CUTTLE FISH AND CRAB AND DETERMINATION OF BACTERIAL SPOILAGE AND RANCIDITY DEVELOPING ON FROZEN STORAGE

Processing techniques like cooking and freezing exhibited significant (P < 0.001) reduction in the bacterial load of cuttlefish, Sepia pharaonis, and marine crab, Portunus pelagicus. Raw cuttle fish had 2.4 × 10⁷ cfu/g which on cooking reduced to 9.7 × 10⁶ cfu/g. Freezing reduced the bacterial load further as cooked frozen product had only 9.9 × 10⁴ cfu/g. Similarly, raw crab had 2.6 × 10⁷ cfu/g which on cooking reduced to 6.5 × 10⁶ cfu/g. A further reduction in bacterial load was seen after freezing as cooked frozen crab exhibited only 7.3 × 10⁴ cfu/g. Escherichia coli and Staphylococcus aureus were present in the limit of acceptability for fish and fish products. Salmonella typhimurium and Vibrio cholerae were absent even in raw stage. Biochemical analysis performed on stored frozen products of cuttle fish and crab exhibited a significant (P ≤ 0.05) increase in bacterial spoilage and rancidity with increasing days of storage. Total volatile base nitrogen, trimethylamine, thiobarbituric acid and free fatty acid contents in frozen products of cuttle fish and crab increased significantly with 120 days of frozen storage.     

EXPOSURE TIME ON BACTERIA FLORA/COUNT AND SHELF LIFE OF CANNED SARDINE (SARDINELLA PILCHARDUS) UNDER AMBIENT AND COLD STORAGE CONDITIONS

This study is aimed at investigating the exposure time on bacteria flora/count and shelf life of conned sardine (Sardinella pilchardus) under ambient and cold storage conditions. Twenty‐five cans with an average weight of 165.05 g of the Titus (with an expiration date of 4 years (September 30, 2004 to September 30, 2008 of batch no. 1432) were purchased and stored at the ambient temperature of 27C and cold (?4C) storage conditions as samples for 12 weeks (precisely between June 15 and September 10, 2005 when the experiment lasted). Proximate analysis of the samples was taken at the beginning of the experiment and at the end for both the ambient and cold stored (after an exposure time of 24 h). Initial baseline and biweekly studies were carried out for 12 weeks for: (1) organoleptic (odor, taste, texture, appearance, rigidity of flesh, color and reaction of fish with can); (2) chemical (trimethylamine [TMA], peroxide values [PVs] and thiobarbituric acid [TBA]); and lastly (3) microbiological analysis for bacteria count and identification of the bacteria on the samples from each storage environment after an exposure time of 24 h in each case. All the chemical parameters (TMA, TBA and PV) were significantly (P < 0.05) correlated with exposure/storage time. Correlation coefficients r = 0.60, 0.66 and 0.54 were low in all classes therefore indicating spoilage rate increases slightly with exposure time/storage period. The highest PV (0.023–0.715), TBA (0.057–1.056) and TMA (1.01 × 10³–3.63 × 10³) ranges were recorded for canned sardines stored at ambient temperature of 27C. However, these are still within acceptable tolerance limit (i.e., organoleptic score of 4–7). Organoleptic assessment with average scores of 5.5 and 6.0 was recorded for cold and ambient stored samples. No viable bacteria count was recorded for cold‐stored samples throughout the experiment. However, the range initial 1.0 × 10⁵ and final 5.0 × 10⁴ cfu/g total plate counts recorded for ambient storage were still below the minimum bacteria count for spoilage that could cause significant or deleterious effect that could result in food poisoning. Traces of the following bacterial species were recorded at ambient temperatures: (1) Bacillus subtilis (1.2 × 10⁴ cfu/g); (2) Streptococcus faecium (9.0 × 10³ cfu/g); (3) Proteus vulgaricus (7.0 × 10⁵ cfu/g); (4) Pediococcus halophilus (6.0 × 10⁵ cfu/g); (5) Micrococcus acidophilus (4.0 × 10³ cfu/g); (6) Streptococcus lactis (4.0 × 10³ cfu/g); and (7) Aerobacter aerogenes (4.0 × 10³ cfu/g), while fungal species Aspergillus terreus (1.0 × 10³ cfu/g) and Aspergillus niger (3.0 × 10³ cfu/g) were recorded also for samples stored at ambient temperature of 27C. Hence, in view of this, the 4‐year recommended expiration date may be upheld for canned sardine (S. pilchardus fish products in oil sources) provided the hazard analysis and critical control points, and closely monitored. It is, therefore, recommended that exposure of canned sardine in oil should not exceed 12–24 h under whatever food storage temperatures to avoid food poisoning.     

MICROBIOLOGICAL QUALITY OF HAWAWSHY CONSUMED IN ISMAILIA, EGYPT

The focus of this study was to evaluate the microbial quality of hawawshy from vending shops in Ismailia Province, Egypt. Microbiological analysis of hawawshy resulted in aerobic plate counts from 2 × 10³ to 4 × 10⁶ cfu/g and spore counts from 2 × 10² to 5 × 10⁴ cfu/g. Total coliforms ranged from 3 to 2400 MPN/g while Enterobacteriaceae counts ranged from 6 × 10 to 8 × 10² cfu/g and enterococci counts were 3 × 10³ to 6 × 10⁵ cfu/g. Escherichia coli, coagulase positive staphylococci and fecal streptococci were detected in 17.3, 14.6 and 57.3% of examined samples, respectively. Salmonella spp. was not detected. Different Enterobacteriaceae spp. such as Citrobacter freundi, Enterobacter cloacae, Klebsiella oxytoca, Klebsiella pneumoniae and Serratia liquefaciens were isolated with different percentages. The obtained results indicate that consumption of hawawshy may constitute a public health hazard, and as a consequence, handling practices should require more attention and improvement.     

QUALITY CHANGES IN ICE-STORED TROPICAL WIRE-NETTING REEF COD (EPINEPHELUS MERRA)

The sensory, bacteriological and biochemical qualities of tropical wire‐netting reef cod (Epinephelus merra) stored in melting ice were studied. The total bacterial load in immediately iced (II) fish was 10 ⁶ cfu /g on the 17th day of storage. The histamine formers were 10 ¹ cfu /g on the initial day, whereas the total lactics was 10 ¹ cfu /g on the third day. The total coliforms decreased from MPN 35 to 0 per gram, while the anaerobic sulfite reducers did not exhibit any consistent trend. The fish delayed for 6 h before icing or delayed iced (DI) fish exhibited bacterial loads of 10 ⁶ cfu /g on the third day, while the total lactics ranged from 10 ¹to 10 ² cfu /g and the histamine formers ranged from 10 ²to 10 ⁴ cfu /g. The total coliforms declined and the anaerobic sulfite reducers increased over a period of 5 days. The pH and hypoxanthine increased during the storage. Both the total volatile base nitrogen and trimethylamine nitrogen attained the maximum limit of acceptability at the end of the storage. The fatty acid content was 0.17% as oleic acid even on the 17th day in II fish. The II fish exhibited a longer shelf life (17 days) when compared to the shorter shelf life (3 days) exhibited by the DI fish.     

The Microbial and Sensory Quality of Mackerel Hot Smoked in Mild Conditions

The quality indices of Atlantic mackerel, hot smoked at core temperature not exceeding 60°C, containing 14-27 g salt and 580-670 g water per kg meat, was determined just after smoking and during storage. The aerobic plate count after smoking, chilling and packing in cardboard boxes was 0-12 cfu/25 cm²of the skin of the smoked fish and 10-240 cfu/g of flesh. It was 1.9 log cycle lower than that in the frozen raw material. At 2°C, the bacterial count on the fish surface and in the meat remained unchanged for at least 3 wk. At 8°C after 14 d, the cfu in the meat of smoked fish ranged from 1.8×10²to 1.6×10⁷/g. The total count on the skin and just under the skin did not increase up to 21 d at 2 and 8°C. There was no statistically significant difference between the mean values of all evaluated sensory attributes of the smoked fish stored up to 2 wk at 2 and 8°C. These results regard products from a smoking plant of very high hygienic standard, fulfilling all EC requirements, with quality assurance system based on HACCP.     

Fermentation and aerobic stability of rehydrated corn grain silage treated with different doses of Lactobacillus buchneri or a combination of Lactobacillus plantarum and Pediococcus acidilactici

We investigated the effects of different types and doses of inoculants for ensiling rehydrated corn grain. Shelled corn was finely ground and rehydrated to 35% moisture. Treatments were as follows: (1) control (no additives); (2) Lactobacillus plantarum and Pediococcus acidilactici (LPPA) at a theoretical application rate of 1 × 10⁵ cfu/g; (3) LPPA at 5 × 10⁵ cfu/g; (4) LPPA at 1 × 10⁶ cfu/g; (5) Lactobacillus buchneri (LB) at 1 × 10⁵ cfu/g; (6) LB at 5 × 10⁵ cfu/g; and (7) LB at 1 × 10⁶ cfu/g. We detected no effect of inoculant dose. Gas losses were greater in silages treated with LB compared with control and LPPA silages. Treating silages with LB reduced the concentrations of lactic acid and ethanol and increased silage pH and concentrations of acetic acid, propionic acid, and 1,2-propanediol. At silo opening, silages treated with LB had higher counts of lactic acid bacteria but lower yeast counts than the control silage. Aerobic stability was greater for silages treated with LB and lower for silages treated with LPPA compared with the control. The LB reduced dry matter (DM) losses during aerobic exposure, whereas LPPA increased them. Prolamin content was lower in silages treated with LB compared with the control, resulting in greater ruminal in situ DM degradability. Inoculating LB to a dose of 1 × 10⁵ cfu/g increased aerobic stability and ruminal in situ DM degradability of rehydrated corn grain silage. The addition of LPPA did not alter the fermentation process and worsened the aerobic stability of rehydrated corn grain silage. Further studies are warranted to confirm these conclusions in other corn hybrids, inoculants, and their combinations.     

Bacterial mediated off-flavours in retail-ready beef after storage in controlled atmospheres

The effects of anoxic storage under CO₂ at 2°C for up to 10 weeks followed by 28 h aerobic display in a retail case on flavour attributes and bacteriology of beef were examined. Pseudomonads reached 2.5 log cfu/cm² in one replication only and their numbers decreased with increasing storage time. Enterobacteriaceae and Brochothrix thermosphacta were not above levels of 1.0 and 2.0 log cfu/cm², respectively. Presumptive lactic acid bacteria increased to maximum numbers of 5.5 log cfu/cm² after 8 weeks. A subpopulation of lactic acid bacteria, able to grow in the presence of 12 g/l acetate, developed later in storage reaching a maximum population of 4.3 log cfu/cm². Flavour amplitude dropped to an inappropriate level after 6 weeks. Between 6 and 8 weeks, the numbers of lactic acid bacteria able to grow in the presence of 12 g/l acetate increased in the absence of an increase in presumptive lactic acid bacteria. This time coincided with the development of “off barny” aromatic, “off barny” aftertaste and unidentified “off” aromatic and a reduction in flavour amplitude suggesting a relationship between the growth of these organisms and changes in organoleptic properties.     

Use of Fluorogenic Assays for the Enumeration of Escherichia coli from Selected Seafoods

Escherichia coli was enumerated and immediately confirmed by incorporating 4-methylumbelliferone glucuronide (MUG) into Lactose Broth (LB), Violet Red Bile Agar (VRB) and M-Endo Broth (M-Endo) in selected seafoods. E. coli in the seafood samples ranged from 1.0 × 10¹– 1.0 × 10³ Most Probable Number (MPN)/g, 1.0 × 10¹– 3.5 × 10² cfu/g and 0.9 × 10¹– 2.8 × 10² cfu/g in LB-MUG, VRB-MUG, and M-Endo-MUG, respectively. Although not statistically significant (α= 0.05), LB-MUG resulted in higher counts in fresh finfish, frozen fish and breaded seafoods. Specificity for E. coli in LB-MUG, VRB-MUG and M-Endo MUG was 96.5%, 92.0%, and 90.0%, respectively. All three fluorogenic assays enabled a rapid and sensitive enumeration of E. coli from seafood products.     

Spore-forming bacteria in commercial cooked,pasteurised and chilled vegetable purées

In commercial purées of broccoli, carrot, courgette, leek, potato and split pea, pasteurized in their final packaging and analysed at two periods, Bacillus spp. were the dominant aerobic mesophilic bacteria (AMB). Initial numbers were generally lower than 2 log cfu g⁻¹. They increased up to 6–8 log cfu g⁻¹after about 20 days of storage at 10°C. At 4°C, numbers of AMB after 20 days were lower than 3 log cfu g⁻¹in potato purée, lower than 4 log cfu g⁻¹in leek purée, and between 3 and 6 log cfu g⁻¹in other products. Strict anaerobes were in markedly lower numbers than AMB. At all storage temperatures tested courgette purée usually showed the most rapid bacterial growth and spoilage. On this product, an increase in storage temperature from 4°C to 10°C resulted in a threefold reduction in time to 5 log cfu g⁻¹, and time to spoilage. Growth kinetics of AMB in courgette purée at 20°C, 15°C, 10°C, 6·5°C and 4°C were determined using a mathematical model. Three hundred and forty eight isolates were identified using the API system. Bacillus circulans, B. macerans and B. polymyxa were among the main species isolated from products stored at 4°C and 10°C, while B. subtilis and B. licheniformis were the dominant species in product stored at abuse temperature. Bacillus cereus was isolated from all storage conditions, but mostly from products stored at abuse temperature.     

Microbial growth in vacuum packaged frankfurters produced in Spain

The effects of storage temperature and time on the microflora of vacuum packed frankfurters were analysed. Total aerobic counts, lactic acid bacteria, Brochothrix thermosphacta and yeast and moulds, were determined as functions of time. Statistically significant differences were observed (P ≤0·001) amongst the counts obtained at 2 and 7°C. At the end of the controlled storage period (42 days) the sausages kept at 7°C showed signs of spoilage. The appearance of superficial slime occurred after 28 days in samples with lactic acid bacteria at counts higher than 10⁸ cfu g⁻¹. The swelling of the pack showed after 42 days in those samples which had a level higher than 5 × 10⁸ cfu g⁻¹. On the contrary, the samples kept at 2°C did not show the aforesaid spoilage signs during the period of controlled storage. Basing our conclusions on the results obtained, a period of shelf life of 28 days was established at 7°C, whilst at 2°C a minimum shelf life of 42 days was obtained.     

The effect of different cooking procedures on microbiological and chemical quality characteristics of Tekirdaǧ meatballs

In this research, the effects of different cooking processes (grilling, oven, and microwave cooking) on microbial flora and chemical composition of the raw and cooked meatballs as consumed in Tekirdaǧ were investigated. Microbial flora of the raw meatballs was as follows: total bacteria, 6.02×10⁶ cfu/g; psychrophilic bacteria, 1.3×10⁵ cfu/g; yeast and mould, 2.4×10⁵ cfu/g; coliforms, 1.1×10⁵ cfu/g; Escherichia coli, 1.0×10² cfu/g; total staphylococcae, 3.3×10² cfu/g; Staphylococcus aureus, 85 cfu/g. While Salmonella was found in only one sample, none of the samples contained Clostridium perfringens. The cooking processes clearly decreased the microbial flora (2–3 log cycles in grilling (71°C) and oven‐cooked (79°C( 3–4 log cycles in microwave (97°C) heating) of the meatballs. However, because of the crust formation and high moisture losses from the meatball surface in microwave heating, some sensorial defects were observed in the final product. Also, fat and moisture losses were higher in microwave cooking compared to the other cooking processes. In conclusion, it is advised to use slightly higher temperatures than used in the grilling or conventinal cooking procedures to increase microbial quality of the meatballs studied in this research.     

MICROBIAL GROWTH IN PACKAGED FRESH ASPARAGUS

The effects of storage temperature and time on the microflora of fresh, vacuum packaged, and modified atmospheres packaged asparagus (Asparagus officinalis) were analyzed. Total aerobic mesophilic, psychrophilic, lactic acid bacteria, Enterobacteriaceae, and yeast and molds were determined as a function of time. The effect of washing on the original microflora of the asparagus and the growth of the different microbial groups during the storage time were checked. From day 8, a progressive increase in the mesophile and psychrophile counts in both types of packaging was observed. At the end of the experiment (day 21), the mesophile and psychrophile counts were all 10⁷ CFU/g, for both types of packaging. In the vacuum packaging, the final enterobacteria counts (2.5 × 10² CFU/g) and yeast and molds (10 CFU/g) were lower than in the polyethylene bag packaged asparagus, which showed enterobacteria counts of 7.3 × 10⁴ CFU/g) and yeast and mold counts of 2.3 × 10⁴ CFU/g. The non-packaged asparagus showed low counts from the fourth day due to their heavy dehydration caused by the low relative humidity in the storage chamber.     

The effect of storage temperature on histamine production and the freshness of yellowfin tuna (Thunnus albacares)

The present study was undertaken to assess the effect of storage temperatures on the shelf life and safety of yellowfin tuna (Thunnus albacares) by studying the changes in microbial, chemical, and organoleptical attributes. Shelf life of yellowfin tuna was determined through changes in total aerobic mesophilic and psychrotrophilic bacterial plate counts, K values, and organoleptic properties, whereas one aspect of its safety was determined through histamine development during storage at 0, 8, and 20 °C. The K value increased linearly at a slow rate (2.4%/day, r² = 0.90, p < 0.05) during storage at 0 °C. Based on K value indices, yellowfin tuna maintained an acceptable shelf life for 12, 5 and 1 day at 0, 8, and 20 °C, respectively. However, yellowfin tuna were rejected earlier by the sensory panelists than their K value indicated. Histamine development was found to be lower than the Food and Drug Authority (FDA) safety level of 5 mg/100 g fish during storage at 0 °C for 17 days. Yellowfin tuna stored at 8 and 20 °C became unsafe for human consumption, reaching unacceptable histamine levels after 4 and 1 day, respectively. Aerobic mesophilic bacteria initially dominated the microflora on yellowfin tuna, however, as storage time increased, aerobic psychrotrophic bacteria became dominant at cold storage but the numbers did not exceeded the International Commission on Microbiological Specifications for Foods (ICMSF) limit of 10⁷ cfu/g.     

Shelf‐life extension of vacuum‐packaged sea bream (Sparus aurata) fillets by combined γ‐irradiation and refrigeration: microbiological,chemical and sensory changes

The combined effect of γ‐irradiation and refrigeration on the shelf‐life of vacuum‐packaged sea bream (Sparus aurata) fillets was studied by monitoring the microbiological, chemical and sensory changes of non‐irradiated and irradiated fish samples using low‐dose irradiation doses of 1 and 3 kGy. Fish species such as sea bream and sea bass are very popular in the Mediterranean countries due to their high quality characteristics, and their preservation is a constant challenge given their extreme perishability. Irradiation (3 kGy) dramatically reduced populations of bacteria, namely, total viable counts (3 vs 7 log cfu g^?1) for the non‐irradiated samples, Pseudomonas spp (<2 vs 7.6 log cfu g^?1), H₂S‐producing bacteria typical of Shewanella putrefaciens (<2 vs 5.9 log cfu g^?1), Enterobacteriaceae (<2 vs 6.0 log cfu g^?1) and lactic acid bacteria (<2 vs 3.5 log cfu g^?1) after 10 days of storage. The effect was more pronounced at the higher dose (3 kGy). Lactic acid bacteria, Enterobacteriaceae and H₂S‐producing bacteria typical of Shewanella putrefaciens showed higher sensitivity to γ‐radiation than did the rest of the microbial species. Of the chemical indicators of spoilage, Trimethylamine (TMA) values of non‐irradiated sea bream increased very slowly, whereas for irradiated samples significantly lower values were obtained reaching a final value of 7.9 and 6.3 mg N per 100 g muscle at 1 and 3 kGy respectively (day 42). Total volatile basic nitrogen (TVB‐N) values increased slowly attaining a value of 67.3 mg N per 100 g for non‐irradiated sea bream during refrigerated storage, whereas for irradiated fish, lower values of 52.8 and 43.1 mg N per 100 g muscle were recorded (day 42). Thiobarbituric acid (TBA) values for irradiated sea bream samples were higher than respective non‐irradiated fish and increased slowly until day 21 of storage, reaching final values of 1.1 (non‐irradiated), 2.0 (1 kGy) and 2.2 mg malonaldehyde kg^?1 muscle (3 kGy), respectively (day 42). Sensory evaluation showed a good correlation with bacterial populations. On the basis of overall acceptability scores (sensory evaluation) a shelf‐life of 28 days (3 kGy) was obtained for vacuum‐packaged sea bream, compared with a shelf‐life of 9–10 days for the non‐irradiated sample. Copyright © 2004 Society of Chemical Industry     

Effect of Vacuum Concentration on Survival and Behavior of S. aureus 234

Staphylococcus aureus 234 population was reduced from 18 × 10⁵ cfu/mL to 31 × 10⁴ cfu/mL after 1:3 vacuum concentration of cow's milk. However, the corresponding figures during concentration of buffalo milk were 20 × 10⁵ cfu/mL and 109 × 10⁴ cfu/mL. The ability to produce enterotoxin B was completely lost in all the five variants (survivors) examined. However, coagulase and Thermonuclease (TNase) activities were only slightly decreased as compared to those of the parent strain. The egg yolk clearing by some variants on Baird Parker agar was delayed by 24 hrs and the colonies were of diffused type. The other activities like phosphatase, gelatin liquefaction, aerobic and anaerobic glucose and mannitol utilization, and hemolysis were not affected in the survivors.     

The microbiology of ogiri production from castor seed (Ricinus communis)

The micro-organisms involved in the fermentation of castor seeds (Ricinus communis) by the traditional method were enumerated and isolated. The effect of using pure cultures to ferment the seeds were also investigated. Using the surface spread plate technique and plate count agar, aerobic counts obtained after seven days of fermentation was 1·7 × 10¹¹ cfu g⁻¹. Similarly anaerobic counts obtained on reinforced clostridial agar was 1·2 × 10⁵ cfu g⁻¹. Bacillus sp., Pseudomonas sp., Micrococcus sp. and Streptococcus sp. were isolated from fermenting castor seeds. The pH of fermenting castor seeds increased from 6·5 to 8·1 during the seven days of fermentation while the total titratable acidity decreased from 47 ml to 36 ml 0.1 N NaOH 100 g⁻¹ sample.The use of pure isolates to ferment the sterile seeds showed that only Bacillus sp. could ferment the seeds in pure cultures.     

Changes in acid and alkaline phosphatase activities during the spoilage of raw muscle from horse mackerel Trachurus japonicus and gurnard Lepidotriga microptera

The aim of this work was to provide information on the role of acid phosphatase (Acp) and alkaline phosphatase (Alp) activities as spoilage indicators of raw fish. Horse mackerel Trachurus japonicus, a red-flesh fish, and gurnard Lepidotriga microptera, a white-flesh bottom fish, were stored at 4 °C. The aerobic bacteria count (APC) of horse mackerel skin increased from 10³ to 10⁷ CFU/cm² in seven days, the Alp activity increased about from 10 to 150 nmol p-nitrophenol/min/g tissue with increase of volatile basic nitrogen (VBN), an index of fish spoilage. The APC of gurnard skin also reached 10⁷ CFU/cm² after 8 days’ storage. The Alp activity was twice that of the Acp activity in the fresh gurnard and the activity decreased slightly during the initial 4 days and increased from four days’ storage.     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

Zusammenfassung: In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden. Vibrio spp. konnte mit 60 Isolaten in 49 Proben (44%) nachgewiesen werden. Am h?ufigsten wurde Vibrio cholerae non-O1 non-O139 isoliert (n=34). Aus 14 Proben konnte Vibrio parahaemolyticus isoliert werden und in fünf Proben konnte Vibrio vulnificusnachgewiesen werden. Erstmals konnte Norovirus in Garnelen nachgewiesen werden. 21 (18,9%) der untersuchten Proben waren positiv. Sowohl Rotavirus als auch Hepatitis A-Virus konnten hingegen nicht nachgewiesen werden.

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In this study 111 samples of raw imported aqua-cultured shrimps have been examined for bacterial pathogens and for pathogen viruses. The samples originated from South-East Asia except for eight Latin-American samples. Most samples were taken from Bangladesh (n=40). The bacteriological quality of these samples was analysed in terms of aerobic plate count, Escherichia coli, Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Vibrio species. Rotavirus, norovirus and hepatitis A-Virus were detected by using a nested RT-PCR. The aerobic plate count was found to be in a range between 4,8×10² to 1,3×10⁹ cfu/g. Fourteen samples (12,6%) showed an aerobic plate count >10⁷ cfu/g. One sample was found to be contaminated with Escherichia coli at a level of 1,9×10³ cfu/g. Staphylococcus aureus was isolated from sixteen samples. Listeria monocytogenes was not detected in any of the shrimp samples examined. Salmonella spp. was found in eight samples. Salmonella Weltevreden was the most frequently isolated serovar. Forty-nine shrimp samples (44%) were positive for Vibrio spp. and 60 Vibrio-isolates could be extracted. Vibrio cholerae non- O1 non-O139 was isolated in 34 samples as the most frequent species. 14 samples contained Vibrio parahaemolyticus, Vibrio vulnificus was present in five samples. For the first time Norovirus could be detected in shrimps. 21 (18,9%) of all examined samples were positive. However, both rotavirus and hepatitis A-virus could not be detected.

Eingegangen: 21. November 2007     

Survival of amine-forming bacteria during the ice storage of fish and shrimp

Survival of amine-forming bacteria during the ice storage of fish and shrimp was investigated up to 14 days of storage. On iced storage the total bacterial load was reduced to one log from an initial load of 10⁵ cfu g⁻¹ in fresh fish/shrimp due to cold shock. The total incidence of biogenic amine-forming bacteria was found to be 74·63% in fish and the same was recorded as 56·05% in shrimp. The amine-forming bacteria recorded were cadaverine- and putrescine-forming bacteria in fish/shrimp, and no histamine former was detected. Gram-negative, non-fermentative rods, viz. Alcaligenes. Flavobacterium, Acinetobacter. Shewanella andPseudomonas , were the predominant amine-forming bacteria during the ice storage of fish and shrimp, in addition to the only Gram-positive genus Micrococcus. The genera Aeromonas and Photobacterium also survived ice storage to a certain extent and may also be responsible for the formation of amines in fish and shrimp.     

CHEMICAL AND MICROBIOLOGICAL QUALITIES OF DRY-SALTED (LAKERDA) BONITO (SARDA SARDA, BLOCH 1793)

In this study, changes in the chemical and microbiological properties of bonito (Sarda sarda, Bloch 1793) salted by dry salting (lakerda) and stored for 6 months at 4 ± 1C were investigated. The fresh gutted and sliced bonitos were used as raw material for salting by using the ratio of fish to salt as 5:1 by weight. Salted fish remained in the liquid pickle formed by salt and the liquid extracted from the fish. This solution was not drained during the storage period. The product is described as “lakerda” in Turkey. In the fresh fish, total volatile basic nitrogen (TVB‐N) and trimethylamine nitrogen (TMA‐N) values were 11.21 mg/100 g and 1.19 mg/100 g, respectively. During the storage period, TVB‐N and TMA values increased slowly to 27.67 mg/100 g and 4.99 mg/100 g, respectively, at the end of the storage period. In the first month after salt processing, the total mesophilic bacteria count was 4.6 × 10² cfu/g. In the later months, mesophilic, psychotropic, coliform bacteria and yeast‐mold did not reproduce. According to the results, bonito salted by dry salting and stored at 4 ± 1C was in good quality in terms of chemical and microbiological properties during the storage period of 6 months.