Bjørn Tore Rotabakk

Pre-mortem stress and the subsequent effect on flesh quality of pre-rigor filleted Atlantic salmon (Salmo salar L.) during ice storage

The impact of pre-mortem stress and the subsequent effect on flesh quality of pre-rigor filleted Atlantic salmon (Salmo salar L.) was investigated. Market-sized salmon were sampled before or during crowding, and before and after pumping and live chilling, representing accumulating stress and fatigue. Blood parameters (pH, Na(+), iCa, pCO2, pO2, glucose, Hct, lactate) and muscle pH confirm a stepwise increase of stress, depending on whether the fish were uncrowded (control), just crowded, uncrowded and chilled or crowded and chilled. Drip loss, water-holding capacity (WHC) and muscle pH during ice storage were not affected by pre-slaughtering conditions. However, a significant effect of storage time was observed. Significantly lowest firmness (N) was observed in crowded and chilled salmon whereas the cathepsin L activity was found to be significantly affected by crowding, live chilling and storage time. Moreover, small effects were observed regarding colour and contents of free amino acids.

Enhancement of Modified Atmosphere Packaged Farmed Atlantic Halibut (Hippoglossus Hippoglossus) Fillet Quality by Soluble Gas Stabilization

The suitability of soluble gas stabilization (SGS) to dissolve CO2 into Atlantic halibut (Hippoglossus hippoglossus) fillets prior to modified atmosphere packaging (MAP) were investigated. Two levels of CO2 partial pressures (200 and 400 kPa) and two levels of time (1 and 2h) with SGS treatment was used in a factorial design, and compared to conventional MAP. Headspace gas volume (mL), headspace gas composition (%), drip loss (%), pH, microbiological characteristics, off-odor and color were assessed on the packaged fillets. Increased partial pressure and increased SGS treatment time before MAP significantly ( p<0.001) increased the CO2 content in the packaged fillets and counteracted package collapse. No interaction between the time and partial pressure was found. SGS treatment significantly (p = 0.038) reduced aerobic plate count (APC) and psychrotrophic count (PC). APC and PC increased significantly the tree first sampling days during storage (7, 15, and 21) and stabilized from day 21 to day 28. H2S producing bacteria and Brochothrix thermosphacta was not affected by the SGS treatment. H2S producing bacteria decreased significantly from day 7 to day 15. SGS treatment decreased the drip loss significantly (p = 0.006). Color and pH were not affected by the SGS treatment. No difference in the off odor was found between the treatments. Based on off odor analysis, the shelf life of the halibut fillet in this trial exceeded 28 days.

A comparative study of diploid versus triploid Atlantic salmon (Salmo salar L.). The effects of rearing temperatures (5, 10 and 15 °C) on raw material characteristics and storage quality

Several major market operators argue that the current level of knowledge about quality is too scant to justify a switch to a large-scale production of triploid salmon. The aim of the present study was, therefore, to elucidate how rearing conditions (5, 10 and 15°C) affect the flesh quality of triploid Atlantic salmon (Salmo salar L., 1.6±0.3kg). As a reference, diploid salmon kept under equal conditions and with equal genetics were used. The main design discriminant was the holding temperature; increased temperature gave increased blood lactate, rigor index (Ir), drip loss (DL), content of astaxanthin and intensity of redness, but reduced muscle pH, cathepsin activity and fillet lightness. Salmon kept at 10°C grew the fastest. It is concluded that ploidy gave less variation than temperature. Triploids were characterized by lower blood haematocrit (Hct) and Ir, higher DL and collagenase activity, and on average, paler and less yellowish fillets.

Effect of Season, Location, Filleting Regime and Storage on Water-Holding Properties of Farmed Atlantic Salmon (Salmo salar L.)

The effect of season, localization, filleting regime and storage on water-holding properties of Atlantic salmon (Salmo salar L.) was investigated. Salmon was sampled at two different slaughter facilities (in the north and south of Norway) in autumn and spring and divided in pre- and post-rigor groups, which were sampled before and after filleting. This gave a total of 16 groups that were analyzed for water-holding capacity (WHC), water content and pH. In addition, a storage trial was performed to assess the effect of all the design variables on drip loss and the composition of the drip loss during up to 18 days of storage. WHC was significantly affected by both rigor status and filleting, while water content was affected by localization and filleting. In addition, post-rigor filleting gave significantly decreased drip loss compared to pre-rigor filleting. However, storage time had the highest impact on the drip loss. Based on this, it is concluded that pre-rigor filleted salmon have excellent water-holding properties and a great potential for early processing (pre-rigor processing). It was however difficult to find a clear connection between the drip loss and the water-holding capacity of the muscle.

Effect of Blood Removal Protocol and Superchilling on Quality Parameters of Prerigor Filleted Farmed Atlantic Cod (Gadus morhua)

UNLABELLED A total of 40 farmed Atlantic cod (Gadus morhua) were in 2 groups either fillet directly after stunning and spray washed or produced into fillets according to traditional slaughter methods including exsanguination for 30 min, gutting and washing. Both groups were either stored superchilled or traditionally on ice. After 7 d postmortem color (CIE L*, a*, b*) and fillet shrinkage was measured by computer imaging along with drip loss and texture hardness. Results show that superchilled fillets had significant lower core temperature than fillets stored on ice during the entire 7 d storage period. This resulted in reduced fillet shrinkage from 14.7% to 6.9% and less drip loss dropping from 9.45% to 3.99% in average. Processing the fish directly into fillets resulted in satisfactory blood drainage, where all groups were in particularly well exsanguinated with a* values below zero. No color difference was observed between filleting groups or chilling methods. Spray washing of the fillets resulted in water uptake and higher drip loss in interaction with chilling method. We conclude that filleting farmed fish in one step is feasible. PRACTICAL APPLICATION Traditionally farmed fish are slaughtered and processed over several steps, which often include live chilling, stunning, exsanguination, chilling, gutting, rinsing, decapitation, filleting before the fillets are packed into polystyrene boxes and shipped with ice. These processes are often time, laboring, space, and energy consuming. A novel processing line for filleting of farmed fish is gutting and filleting the fish directly after decapitation and replacing exsanguination with spray washing the fillets. In addition, all the cooling steps are replaced by superchilling the fillets. This novel process line gives fillets with comparable if not superior quality compared to the traditional process.

Effects of Additives and Packaging Method on Quality and Microbiological Characteristics in Mild Thermal Processed Fish Mince

The effect of adding 2% sodium lactate (NaL) premix to mild thermal processed fish mince, and the effect of packaging the product in vacuum, modified atmosphere (MA), or pretreated with soluble gas stabilization (SGS) prior to MA packaging were investigated. Adding 2% NaL premix significantly affected the color, and the bacterial load was significantly decreased compared to the control product, together with significant differences in the sensory score. Breaking force, firmness, stiffness, and gel strength were significantly increased by adding NaL, while no effect was found on head space gas composition, top web deflation, and pH. SGS significantly decreased the microbial load, but had no interaction effect with NaL. SGS significantly increased the amount of CO2 in the head space gas, together with decreased top web deflation compared to modified packaging. Vacuum packaging significantly increased the breaking point, firmness, and stiffness and increased pH compared to MA and SGS. Addition of a NaL premix to minced fish products can be used successfully to increase shelf life without compromising other quality characteristics. SGS treatment before packaging in MA can successfully be used as an alternative to adding NaL with respect to microbiological product quality and without compromising other quality characteristics.