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.
Merki: Atlantic cod
The effects of insulated tub depth on the quality of iced Atlantic cod / Áhrif dýptar einangraðra kera á gæði ísaðs þorsks
Markmið verkefnisins var að rannsaka gæði þorsks sem hafði verið slægður einum degi eftir veiði, ísaður og pakkað í 12 mismunandi stór ker, 4×250 L, 4×460 L og 4×660 L. Fylgst var með tilraunafiskum efst og neðst í hverju keri. Kerin voru geymd í hitastýrðu umhverfi við 1 °C og gerðar mælingar eftir 6, 10, 13 og 15 daga frá pökkun. Til að meta gæði þorsksins var notast við vatnstap í kerum eftir geymslu, vinnslunýtingu og skynmat. Niðurstöður sýndu að vatnstap var mest í 660 L keri og minnst í 250 L keri. Enginn munur var á vinnslunýtingu. Í öllum tilfellum var minna los í botni kers miðað við toppinn, líklega vegna mismunandi stærðar fiska í toppi og botni. Enginn munur var á niðurstöðum úr mati með gæðastuðulsaðferð (QIM) milli kera en þeir skynmatsskalar sem til eru ná ekki til þeirra eiginleika sem greinilegur munur sást á. Mikill munur sást á fiskum í topplagi og fiskum í botnlagi í öllum tilvikum, en ísför og marin flök voru fyrirferðameiri á botnfiskum. Í framhaldi tilraunarinnar verður í áframhaldandi rannsóknum á gæðum ísaðs og ofurkælds fisks í mismunandi stórum kerum hannaður nýr skynmatsskali sem tekur á þessum þáttum, þ.e. förum eftir ís og marskemmdum í flökum.
The aim of this project was to examine the quality difference of Atlantic cod that had been iced and packed into 12 different sized food containers (tubs), 4×250 L, 4×460 L and 4×660 L. Each tub was split up into two groups, top-and bottom layer. Drip loss, processing yield, and sensory evaluation were used to evaluate the quality of the cod. The results showed that the greatest drip loss was in the 660 L tub, and the least in the 250 L tub. There was no difference in processing yield. Sensory evaluation showed no difference between tubs, except that the fillets from fish in the bottom layer of all containers had less gaping than fillets from the top layer of fish, most likely due to size differences of top-and bottom layer fish. No current sensory evaluation scales account for different amounts of ice marks and crushed fillets that was detected between fish in the top-and bottom layer of the tubs. The results of this project will be used in continuing research of iced and superchilled fish in different sized containers to develop a new sensory scale that will account for these qualities.