Sveinung Birkeland

Injection-Salting and Cold-Smoking of Farmed Atlantic Cod (Gadus morhua L.) and Atlantic Salmon (Salmo salar L.) at Different Stages of Rigor Mortis: Effect on Physical Properties

Processing of fish is generally conducted postrigor, but prerigor processing is associated with some potential advantages. The aim of this study was to study how 5 processing regimes of cold-smoked cod and salmon conducted at different stages of rigor influenced yield, fillet shrinkage, and gaping. Farmed cod and salmon was filleted, salted by brine injection of 25% NaCl, and smoked for 2 h at different stages of rigor. Filleting and salting prerigor resulted in increased fillet shrinkage and less increase in weight during brine injection, which in turn was correlated to the salt content of the fillet. These effects were more pronounced in cod fillets when compared to salmon. Early processing reduced fillet gaping and fillets were evaluated as having a firmer texture. In a follow-up trial with cod, shrinkage and weight gain during injection was studied as an effect of processing time postmortem. No changes in weight gain were observed for fillets salted the first 24 h postmortem; however, by delaying the processing 12 h postmortem, the high and rapid shrinking of cod fillets during brine injection was halved.

Microbiological Quality of Desalted Cod in Consumer Packages—Effects of Storage Atmospheres and Pretreatments

The effect of modified atmosphere (MA) packaging using CO2 (50%) combined with different balancing gases (N2 and O2, 50%) was investigated and compared to packaging in air. In addition, the suitability of phosphate brining and steaming as a pretreatment of desalted cod to increase product quality was investigated. Headspace gas composition (%), drip loss (%), pH, and microbial counts were assessed in the desalted and packaged portions. Storage in MA significantly (p < .001) decreased the aerobic plate counts (APC), psychrotrophic counts (PC), and yeast counts by 2–3 log10 units after 15 days of chilled storage (2–3°C) as compared to storage in air. Using O2 or N2 as balancing gas had no significant impact on the microbiological counts. Application of N2 as a balancing gas significantly (p < .050) increased the drip loss as compared to balancing with O2 or storage in air. Pretreatment with phosphate brine significantly increased the weight of the portions as compared to steam treated and control groups. Phosphate-treated products had significantly (p < .001) decreased CO2 and increased O2 in the packaging headspace and a significantly (p < .001) higher pH (0.12–0.16 pH units) compared to the other treatment groups. No significant effects of pretreatments on the microbiological characteristics were observed. The use of MA for packaging of desalted cod portions increases the microbiological quality of the products.

The effect of K-lactate salt and liquid smoke on bacterial growth in a model system

ABSTRACT The effects of a commercial lactate salt formulation—containing potassium lactate (KL) and potassium acetate (KA)—and liquid smoke (LS) on the growth of selected lactic acid bacteria (LAB; Carnobacterium maltaromaticum, Carnobacterium inhibens, Lactococcus lactis, Lactobacillus curvatus, and Enterococcus faecalis), fish spoilage bacteria (Photobacterium phosphoreum, Pseudomonas putida, and Vibrio vulnificus), and Listeria innocua, were examined in a tryptic soy broth model system at 20ºC based on BioScreen data. The most pronounced inhibition effect on growth of bacteria was seen in the presence of 6% KL + 0.4% KA, used either combined with LS or alone. Only a minor inhibition effect on growth was found in the presence of LS alone. The only exception was Lactobacillus curvatus, which grew quite well in the presence of LS compared to control medium. The growth of Vibrio vulnificus was prevented in 6% KL + 0.4% KA, and significantly inhibited in the presence of 3% KL + 0.2% KA. When V. vulnificus was grown in NaCl, KA, and KL + KA, it was observed that KL + KA had a better inhibition effect than sodium salt within the same concentration range.

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.