Occurrence of Listeria monocytogenes on the seafood contact surfaces of Tuticorin Coast of India.

Listeria monocytogenes was screened from different seafood contact surfaces in five sampling sites of fishing harbour, fish landing centers, seafood processing plants, fish market, and fish curing yards of Tuticorin Coast of India. 115 swab samples were collected and tested for the occurrence of L. monocytogenes by conventional and molecular methods. Overall, 5.22% of swab samples collected were positive for L. monocytogenes. The fishing harbour had high incidence (10.3%) of L. monocytogenes followed by fish landing centers (5.9%), and seafood processing plants (4.1%). Boat deck, fish transport tricycle were the two seafood contact surfaces in fishing harbour, which had the occurrence of L. monocytogenes. The swab samples from fish market and fish curing yards were negative for L. monocytogenes. All the isolated colonies of L. monocytogenes were confirmed by PCR assay targeting virulent hlyA gene. The DNA of all the isolates yielded a product of 174 bp on PCR amplification in comparison with L. monocytogenes Type culture (MTCC 1143). The results clearly indicated the occurrence of L. monocytogenes in seafood contact surfaces along the Tuticorin Coast of India.

Sensory, biochemical and bacteriological properties of octopus (Cistopus indicus) stored in ice.

Octopus (Cistopus indicus) were examined for the changes in autolytic activity, ammoniacal nitrogen, non-protein nitrogen (NPN), total volatile base nitrogen (TVBN), free fatty acid (FFA) content, aerobic plate count (APC) and sensory quality based on Quality Index Method (QIM) during ice storage. They were sensorily acceptable up to 7 days when QIM score was 10.97 out of 16.00. Autolytic activity increased from the initial value of 174 to 619 nmoles Tyr/g/h within day 3 and later decreased. There was also an increase in NPN (34.88 to 76.16 mg %), ammoniacal nitrogen (0 to 7.30 ppm) and free fatty acid content (0.35 to 1.69 % of oleic acid) during storage. TVBN values did not correlate with the spoilage, as it increased from 28 to 145 mg% within day 5, exceeding the limit of acceptability; although total QIM score was 7.47. Aerobic plate count did not show significant change suggesting that the spoilage in octopus was not microbial. The rapid spoilage in octopus was mainly due to the release of NPN compounds following autolytic activity leading to the formation of ammoniacal nitrogen, rather than microbial spoilage. Hence, ammoniacal nitrogen can be taken as an index for spoilage of ice stored octopus.

Detection of hemolytic strains of Aeromonas hydrophila and A . sobria along with other Aeromonas spp. from fish and fishery products by multiplex PCR.

Hemolytic strains of Aeromonas spp. from fish and fishery products were detected by multiplex PCR. The selected primers for the amplification of segments of ahh1, asa1 and 16S rRNA gene yielded products with the size of 130 bp, 249 bp and 356 bp, respectively. This assay was found to be highly sensitive, as it could detect 7 and 9 cells of Aeromonas hydrophila and A. sobria with a detection limit of 1 pg of pure genomic DNA. The assay, when screened for 73 commercial fish and fishery product samples consisting of freshwater, marine fish and shellfish, showed 56 % positive for Aeromonas spp., 16 % for Aeromonas hydrophila and 13 % for A. sobria. This assay provides specific and reliable results and can be a powerful tool for the simultaneous detection of hemolytic strains of A. hydrophila A. sobria and other Aeromonas spp. from fish and fishery products.

Physico-functional and mechanical properties of chitosan and calcium salts incorporated fish gelatin scaffolds.

Four types of fish gelatin scaffolds viz. gelatin (G), gelatin-chitosan (GC), gelatin-calcium acetate (GCA) and gelatin-chitosan-calcium acetate (GCCA) prepared were investigated for their functional properties, biomechanical strength, microstructural changes in relation to biodegradation. GC scaffold was superior with pH 3.15 and viscosity 9.40 cP. Chitosan and calcium acetate improved tensile strength (TS) and Young's modulus (YM), but lowered elongation at break (EAB). GCCA scaffold possessed moderate TS of 19.6 MPa, EAB of 4.76% and YM of 185 MPa. Foaming ability ratio of GC scaffold was high (3.41). GCA and GCCA scaffolds remained for 4 days before complete in vitro biodegradation. GC scaffold had larger cavities (180-300 µm) that were responsible for low swelling ratios and shrinkage factor. GCCA scaffold with moderate swelling rates, mechanical, functional properties and lowered biodegradation rate were found more suitable for biomedical applications.

Skin, bone and muscle collagen extraction from the trash fish, leather jacket (Odonus niger) and their characterization.

Acid soluble (ASC) and pepsin soluble (PSC) collagens were extracted from the skin, bone and muscle of a trash fish, leather jacket (Odonus niger) by three different extraction methods. Method I gave 46-50% yield for ASC, Method II gave 49-58% yield for both ASC and PSC and Method III gave 64-71% yield for PSC. The addition of pepsin had increased the yield by 30-45%. The yields of collagen from skin and bone were higher than muscle. SDS-PAGE pattern revealed that skin and bone collagen as Type I collagen with a typical (α1)2α2 chains and muscle collagen as Type V collagen with a typical α1α3α2 chains. Td values of bone and muscle collagen were high (30-32 °C) compared to skin collagen (27-28 °C). The higher imino acids (190 residues/1,000 residues) were found responsible for the higher Td values. The trash fish, leather jacket can therefore be exploited effectively for collagen as it has got good thermal properties for pharmaceutical and biomedical applications.

Comparison of the properties of multi-composite fish gelatin films with that of mammalian gelatin films.

Four types of films viz. gelatin, gelatin-MMT, gelatin-chitosan and gelatin-MMT-chitosan prepared from redsnapper and grouper bone gelatin were compared with the mammalian gelatin films, for their mechanical and barrier properties. Grouper gelatin films had higher tensile strength (TS) and Young's modulus (YM), but lower elongation at break (EAB) than redsnapper films. Incorporation of MMT and chitosan improved the TS (p<0.05) of the films. Water solubilities were lower (p<0.05) in films incorporated with chitosan compared to simple gelatin film. Protein solubilities were lower in gelatin-MMT films, irrespective of the type of solvent used. The water vapour transmission rates (WVTR) of fish and mammalian gelatin films were similar, but addition of MMT had reduced WVTR (p<0.05). SEM micrographs depicted smoother surface for gelatin-MMT and gelatin-MMT-chitosan films. Thus, composite fish gelatin films made with MMT and chitosan could be the good natural biodegradable films due to their better mechanical and barrier properties.

Microbiological quality of cuttlefish (Sepia pharaonis) fillets stored in dry and wet ice.

Microbiological quality of cuttlefish (Sepia pharaonis) fillets stored in three different ice conditions was studied. Fillets stored in wet ice at a ratio of 1:1 (package III) were sensorially acceptable for only 18 h, while that stored in dry ice at 1:1 (package I) and combination of dry ice and wet ice at 1:0.2:0.5 (package II) were in acceptable condition up to 24 h without re-icing and thus there was an extension of shelf life by about 33%. Total bacterial load was 7 log10 cfu/g at the end of the storage period. Total psychrophilic population increased from zero to 7 log10 cfu/g while total lactic acid bacteria from zero to 5 log10 cfu/g. H2S producers were detected only at 18 h, with a count of 1 log10 cfu/g. Sulphite-reducing Clostridia increased gradually from zero to 110 most probable number count/g. Fresh cuttlefish fillets carried a bacterial flora of Micrococcus, Planococcus, Streptococcus, Moraxella, Proteus and Aeromonas. Pseudomonas was dominant in wet ice pack, while Aeromonas was dominant in both the dry ice and combination pack. Immediately after packing, the temperatures recorded in packages I, II and III were 10.5, 1.2 and 3.0 °C, respectively, which drastically decreased in 1 h and then maintained and finally increased gradually. The results indicate that use of combination of dry ice and wet ice is economical and very much useful to seafood industries, as this package considerably reduced the cost of air freight, as well as improved the quality and shelf life of cuttlefish.

Effect of processing treatments on the white spot syndrome virus DNA in farmed shrimps (Penaeus monodon).

AIMS: To investigate the effect of processing treatments on the destruction of white spot syndrome virus (WSSV) DNA in WSSV-infected farmed shrimps (Penaeus monodon). METHODS AND RESULTS: The presence of WSSV was tested by single step and nested polymerase chain reaction (PCR). The primers 1s5 & 1a16 and IK1 & IK2 were used for the single step PCR and primers IK1 & IK2-IK3 & IK4 were used for the nested PCR. Various processing treatments such as icing, freezing, cooking, cooking followed by slow freezing, cooking followed by quick freezing, canning, and cold storage were employed to destroy the WSSV DNA. Of the processing treatments given, cooking followed by quick freezing was efficient in destroying WSSV DNA in WSSV-infected shrimp products. Canning, and cooking followed by slow freezing process had some destructive effect on the WSSV DNA, as WSSV DNA in such processed shrimp products was detected only by nested PCR. Icing, slow freezing, quick freezing, and cooking processes had no effect on the destruction of WSSV DNA. A gradual increase in the destruction of WSSV DNA was observed as the cold storage period increased. CONCLUSION: The results indicated that cooking followed by quick freezing process destroy the WSSV DNA. SIGNIFICANCE AND IMPACT OF THE STUDY: WSSV can be destroyed by cooking followed by quick freezing and this combined process can reduce the disease transmission risks from commodity shrimps to native shrimps.

Effect of different types of heat processing on chemical changes in tuna.

The chemical changes in skipjack tuna (Katsuwonus pelamis) subjected to cooking, frying, canning and microwave heating were studied. Raw tuna contained an unusual fatty acid C16:3 in high proportion (29.3%) followed by C18:2, C24:1, C16:0 and C18:3. Health beneficial fatty acids, eicosapentaenoic acid (EPA) (1.67%) and docosahexaenoic acid (DHA) (2.50%), were quite low with ω-3/ω-6 ratio 0.28. The total saturated fatty acids suffered major loss in fried (70%) and canned tuna (40%) due to loss of C16:0, C14:0 and C22:0. The monounsaturated fatty acids content increased (38%) in cooked and microwave heated tuna due to C24:1. The polyunsaturated fatty acids content increased in fried (50%) and canned (25%) tuna due to the uptake of frying and filling oil, respectively during processing. The loss of health beneficial ω-3 fatty acids, EPA and DHA were minimum in cooked tuna followed by microwave heated tuna. Canning totally destroyed these fatty acids. In fried tuna, the losses of EPA and DHA were 70 and 85%, respectively. Thiobarbituric acid - reactive substances values increased in heat processed tuna. Cholesterol increased in canned and microwave heated tuna but not in cooked tuna. Reduction of cholesterol in fried tuna was due to its migration into frying oil. This study indicated that cooking and microwave heating are the better processing methods to retain the health beneficial ω-3 fatty acids in comparison to frying and canning.

Quality changes in squid (Loligo duvaucelli) tubes chilled with dry ice and water ice.

Squid tubes were packed with 100% (w/w of squid) dry ice (PI), 20% dry ice and 50% water ice (PII) and 50% water ice (PIII) in polyethylene bags and store in thermocole boxes at room temperature (32 ± 2°C) for 24 h. Quality changes curing storage were studied. Lowest temperature of -30.3°C was attained in PI while it was 15-16°C in PII and PIII at 1 h of storage. The gas compositions in packages initially were 21% O2, 0.4% CO2 and 78.1% N2 in PI, PII and PIII, respectively. During storage for 24 h highest level of 82.5% CO2 was noticed in PII. Fresh squid tubes had bacterial flora of Hafnia, Pseudomonas, Bacillus, Flavobacterium and Alcaligens. Hafnia constituted 74% of the flora. Alcaligenes (47%), Alteromonas (30%) and Alcaligenes (56%) were dominant in squid tubes stored in 100% dry ice, in the combination package, and in 100% water ice, respectively. Increase in total volatile base nitrogen and trimethylamine nitrogen, no definite trend in free fatty acid values in all packages while increase in pH in PI and PIII and no consistent changes in PI were noticed during storage for 24 h. The PI had lowest bacterial counts and PIII the highest. Squids stored in PI and PII were sensorily acceptable after 24 and 18 h, respectively.

Stability of chloramphenicol residues in shrimp subjected to heat processing treatments.

The stability of chloramphenicol residues in white shrimp (Penaeus indicus) subjected to cooking (100 degrees C) for 10, 20 and 30 min (C1, C2 and C3) as well as retorting (121 degrees C) for 10 and 15 min (R1 and R2) was studied by a microbial assay method using Photobacterium leiognathi as the test organism. The microbial assay method was found to have a good sensitivity of 1 microg/ml the loss of chloramphenicol in shrimp subjected to cooking for 10, 20 and 30 min was 6%, 12% and 29%, respectively. Similarly, the loss was 9% and 16% from the shrimp subjected to retorting for 10 and 15 min, respectively. The loss of chloramphenicol was found to increase with increase in temperature and duration of heating. This study showed that chloramphenicol is an unstable aquaculture drug that is destroyed or degrades during heat processing treatments.

Quantitative and qualitative studies on the bacteriological quality of Indian white shrimp (Penaeus indicus) stored in dry ice.

Indian white shrimp (Penaeus indicus) stored in dry ice at the 1:1 ratio were found to be organoleptically suitable for consumption when they were stored for 24 h without reicing. Shrimp stored in water ice at the 1:1 ratio (as control) were acceptable up to 18 h. Shrimp stored in a combination of dry ice and water ice at the ratio of 1:0.2:0.5 were also found to be acceptable up to 24 h. Total bacterial load ranged from 10(6) to 10(9) cfu g(-1), while total psychrophiles ranged from 10(3) to 10(6) cfu g(-1). Total lactics were found in the levels of 10(2)-10(6) cfu g(-1). H(2)S producers were from 10(3) to 10(5) cfu g(-1). Lowest temperature of -4.8 degrees C was observed in shrimps stored in dry ice at 1:1 ratio. Bacterial flora associated with fresh raw shrimp were Aeromonas, Pseudomonas, Vibrio, Flavobacterium and Serratia. Aeromonas constituted 38% of the flora in raw shrimp. Flavobacterium (43%), Pseudomonas (47%) and Pseudomonas (38%) were the dominant bacterial flora in the shrimp stored in dry ice at 1:1 ratio, in the combination package, and in water ice at 1:1 ratio, respectively.

Detection of White Spot Syndrome virus and Yellowhead virus in prawns imported into Australia.

OBJECTIVE: To determine whether viable White Spot Syndrome virus (WSSV) or Yellowhead virus (YHV) were present in prawn products imported into Australia. PROCEDURE: A sample of fourteen uncooked prawns was obtained from a consignment imported from southeast Asia. Each of the prawns was examined for WSSV by polymerase chain reaction (PCR), and then a bioassay was conducted in which a 10% homogenate of cuticular epithelium from each of the prawns was inoculated intramuscularly into healthy challenge prawns (Penaeus monodon) from Australia. The latter were then monitored for clinical signs of disease, and tissue samples were processed for electron microscopy, histological examination and for detection of WSSV by in situ hybridization (ISH) using a commercial kit. Limited numbers of haemolymph samples from inoculated challenge prawns were also examined by PCR for the presence of WSSV and YHV. All work was carried out under microbiologically secure conditions. RESULTS: Results of the initial PCR examination for WSSV on the imported prawns were not definitive. However, in the bioassay, several of the challenge prawns inoculated with homogenates from the imported prawns showed clinical signs of disease (inappetence and lethargy) within 24 h post inoculation (pi) and died at 1 to 4 days pi. Tissue samples from a number of moribund prawns demonstrated lesions typical of White Spot Disease (WSD), and the presence of the virus was confirmed by electron microscopy, ISH and PCR. YHV was also demonstrated by PCR in two challenge prawns inoculated with homogenates. CONCLUSION: Viable WSSV and YHV were present in frozen prawn products imported into Australia for human consumption from southeast Asia. Importation of frozen infected products may present a risk of transferring virus to wild and farmed populations of crustaceans in this country. To date, WSD and Yellowhead Disease remain exotic to Australia.

Incidence of Listeria spp. in tropical fish.

The incidence of Listeria spp. in tropical fish and shellfish was studied. The isolation protocol included a pre-enrichment, followed by two selective enrichment steps and plating on three selective agars. Listeria monocytogenes could be detected in 17.2% of finfish and 12.1% of shellfish. L. innocua was the most common species encountered. In 6.9% finfish and 5.6% shellfish, both L. monocytogenes and L. innocua were detected. Polymerase chain reaction (PCR)-based amplification of internal fragments of the iap gene was found to be useful in differentiation of L. monocytogenes from L. innocua.