Impact of onboard chitosan treatment of whole cod (Gadus morhua) on the shelf life and spoilage bacteria of loins stored superchilled under different atmospheres.

The initial handling of marine fish on board fishing vessels is crucial to retain freshness and ensure an extended shelf life of the resulting fresh products. Here the effect of onboard chitosan treatment of whole, gutted Atlantic cod (Gadus morhua) was studied by evaluating the quality and shelf life of loins processed six days post-catch and packaged in air or modified atmosphere (% CO2/O2/N2: 55/5/40) and stored superchilled for 11 and 16 days, respectively. Sensory evaluation did not reveal a clear effect of chitosan treatment on sensory characteristics, length of freshness period or shelf life of loins under either packaging conditions throughout the storage period. However, directly after loin processing, microbiological analysis of loins showed that onboard chitosan treatment led to significantly lower total viable counts as well as lower counts of specific spoilage organisms (SSO), such as H2S-producers and Pseudomonas spp., compared to the untreated group. In addition, the culture-independent approach revealed a lower bacterial diversity in the chitosan-treated groups compared to the untreated groups, independently of packaging method. Partial 16S rRNA gene sequences belonging to Photobacterium dominated all sample groups, indicating that this genus was likely the main contributor to the spoilage process.

In vitro biological response of human osteoblasts in 3D chitosan sponges with controlled degree of deacetylation and molecular weight.

We have studied the effect of chitosan sponges, produced from chitosan batches with distinct degree of deacetylation (DDA) and molecular weight (Mw), on the adhesion, growth and differentiation of primary human osteoblasts with an aim to offer a suitable tool for guided bone regeneration. All the chitosan sponges revealed similar microstructure, irrespective of the DDA (58, 73, 82, 88, and 91 %) and Mw (749, 547, 263, 215, and 170 kDa, respectively). Cell spreading was higher on sponges having a higher DDA. Higher DDA induced a more pronounced increase in alkaline phosphatase activity, osteopontin (OPN), vascular endothelial growth factor-A (VEGF), interleukin-6 (IL-6), and reduction in monocyte chemoattractant protein-1 (MCP-1), sclerostin (SOST) and dickkopf related protein-1 as compared to lower DDA. Lower DDA induced the increased secretion of osteoprotegerin and SOST as compared to higher DDA. The combination of higher DDA and Mw induced an increased secretion of VEGF and IL-6, however reduced the secretion of OPN as compared to chitosan with similar DDA but with lower Mw. In summary, the variations in cellular responses to the different chitosan sponges indicate a potential for individual tailoring of desired responses in guided bone regeneration.

Shelf life of air and modified atmosphere-packaged fresh tilapia (Oreochromis niloticus) fillets stored under chilled and superchilled conditions.

Optimal packaging and storage conditions for fresh tilapia fillets were established by evaluating sensory and microbiological changes, as well as monitoring physicochemical properties. Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted, deskinned, and packaged in air and 50% CO2/50% N2 prior to chilling and superchilling storage at 1°C and -1°C. Sensory analysis of cooked samples revealed a shelf life of 13-15 days for air-packaged fillets during storage at 1°C and 20 days at -1°C. At the end of shelf life in air-packaged fillets, total viable counts (TVC) and pseudomonads counts reached log 8 colony-forming units (CFU) g(-1). In 50% CO2/50% N2-packaged fillets, the lag phase and generation time of bacteria were extended and recorded counts were below the limit for consumption (

Bacterial composition and succession during storage of North-Atlantic cod (Gadus morhua) at superchilled temperatures.

BACKGROUND: The bacteriology during storage of the North-Atlantic cod has been investigated for the past decades using conventional cultivation strategies which have generated large amount of information. This paper presents a study where both conventional cultivation and cultivation independent approaches were used to investigate the bacterial succession during storage of cod loins at chilled and superchilled temperatures. RESULTS: Unbrined (0.4% NaCl) and brined (2.5% NaCl) cod loins were stored at chilled (0 degrees C) and superchilled (-2 and -3.6 degrees C) temperatures in air or modified atmosphere (MA, % CO2/O2/N2: 49.0 +/- 0.6/7.4 +/- 0.2/43.7 +/- 0.4). Discrepancy was observed between cultivation enumeration and culture independent methods where the former showed a general dominance of Pseudomonas spp. (up to 59%) while the latter showed a dominance of Photobacterium phosphoreum (up to 100%).Gas chromatography-mass spectrophotometry (GC-MC) showed that trimethylamine was the most abundant volatile in mid- and late storage periods. Terminal restriction polymorphism (t-RFLP) analysis showed that the relative abundance of P. phosphoreum increased with storage time. CONCLUSION: The present study shows the bacteriological developments on lightly salted or non-salted cod loins during storage at superchilled temperatures. It furthermore confirms the importance of P. phosphoreum as a spoilage organism during storage of cod loins at low temperatures using molecular techniques. The methods used compensate each other, giving more detailed data on bacterial population developments during spoilage.

Effect of brining, modified atmosphere packaging, and superchilling on the shelf life of Cod (Gadus morhua) loins.

The aim of these experiments was to evaluate the effect of brining, modified atmosphere packaging (MAP), and superchilling on the quality changes of cod loins as measured by microbial, sensory, and chemical analysis. Unbrined and brined (2.5 +/- 1.0% NaCl) cod loins were kept in styrofoam boxes (air) and under modified atmosphere (MA, CO(2)/O(2)/N(2): 50/5/45) at 0, -2, and -3.6 degrees C. Samples were examined over a 4-wk period. Total viable psychrotrophic counts and counts of H(2)S-producing bacteria reached higher numbers in the air-packed brined fish at -2 and -3.6 degrees C than in comparable unbrined groups, being significantly different (P < 0.05) at the lower temperature. However, lower counts of these bacteria were obtained in the brined MAP fish than in comparable unbrined fish. Counts of Photobacterium phosphoreum increased most rapidly in air- and MA-packed loins kept at 0 degrees C. Lower counts were found at superchilled temperatures. According to sensory analysis the shelf life of unbrined air-packed loins was about 11 d at 0 degrees C and 14 to 15 d at -2 degrees C. The shelf life of MA-packed unbrined loins was about 14 to 15 d at 0 degrees C but 21 d at -2 degrees C. Thus, synergism of combined superchilling (-2 degrees C) and MA led to a considerable shelf life increase for unbrined loins despite the fact that processing and packaging took place 4 to 5 d post-catch. The shelf life of air-packed brined loins at -2 degrees C was 12 to 15 d but only 13 d under MA. The same synergistic effect did therefore not apply to brined loins as with unbrined ones.

Characterization of volatile compounds in chilled cod (Gadus morhua) fillets by gas chromatography and detection of quality indicators by an electronic nose.

Volatile compounds in cod fillets packed in Styrofoam boxes were analyzed during chilled storage (0.5 degrees C) by gas chromatography (GC)-mass spectrometry and GC-olfactometry to screen potential quality indicators present in concentrations high enough for detection by an electronic nose. Photobacterium phosphoreum dominated the spoilage bacteria on day 12 when the fillets were rejected by sensory analysis. Ketones, mainly 3-hydroxy-2-butanone, were detected in the highest level (33%) at sensory rejection, followed by amines (TMA) (29%), alcohols (15%), acids (4%), aldehydes (3%), and a low level of esters (<1%). The electronic nose's CO sensor showed an increasing response with storage time coinciding with the production of ethanol and 2-methyl-1-propanol that were produced early in the storage, followed by the production of 3-methyl-1-butanol, 3-methyl-butanal, 2,3-butandiol, and ethyl acetate. Lipid-derived aldehydes, like hexanal and decanal, were detected in similar levels throughout the storage time and contributed to the overall sweet odors of cod fillets in combination with other carbonyls (3-hydroxy-2-butanone, acetaldehyde, 2-butanone, 3-pentanone, and 6-methyl-5-heptene-2-one).

Tracing Listeria monocytogenes isolates from cold-smoked salmon and its processing environment in Iceland using pulsed-field gel electrophoresis.

Listeria spp. and Listeria monocytogenes contamination of cold-smoked salmon (n=125) and its processing environment (n=522) were evaluated during surveys conducted in 1997-1998 and 2001 as well as in samples of final products analysed in 2001. The overall frequencies of Listeria spp. and L. monocytogenes in samples from all sources were 15.1% and 11.3%, respectively, but the incidence of L. monocytogenes in cold-smoked salmon final products was only 4%. A total of 201 L. monocytogenes isolates were characterised by Pulsed-Field Gel Electrophoresis (PFGE) in order to trace L. monocytogenes contamination in the processing plants. The combination of AscI and ApaI macrorestriction patterns yielded 24 different pulsotypes in 6 plants. One pulsotype observed by AscI restriction digestion comprised 148 of the 167 typed isolates from two processing plants. Two other pulsotypes predominated in samples from raw material, processing environments and final products. The results indicate that raw material, floors, and drains are potential sources of the L. monocytogenes found on cold-smoked salmon products. This highlights the need to readdress the design and cleaning of processing plants and equipment, and staff behavior. Hindering the introduction into and spread of the organism through the processing environment is necessary to avoid jeopardizing safety of the final product.