Svein Kristian Stormo

Automatic Nematode Detection in Cod Fillets (Gadus Morhua) by Transillumination Hyperspectral Imaging

Traditional quality control of cod fillets is currently made by manual inspection on candling tables. This is a time consuming and expensive operation, contributing to a significant share of the cost with cod fillet production. In this study, transillumination hyperspectral imaging was implemented as a method for automatic nematode detection in cod fillets moving on a conveyer belt, and evaluated on industrially processed cod fillets. An overall detection rate of 58% of all nematodes (N= 922), with detection rate of 71% and 46% for dark and pale nematodes, respectively, is reported. This is comparable, or better, than what is reported for manual inspection under industrial conditions. The false alarm rate was high, with 60% of the fillets reported with one or more false alarms. These results show that the method is promising, but needs further refinements to reduce the false alarm rate and increase the imaging speed from 25 to 400 mm/s. Practical Application: Manual inspection of cod fillets is a huge bottleneck for the industry, accounting for half the production cost with cod fillet processing and reducing the processing speed. Transillumination hyperspectral imaging has the potential to reduce the manual labor required for cod fillet inspection and hence reduce the cost and increase the end product quality.

Effects of single wavelength selection for anisakid roundworm larvae detection through multispectral imaging

The occurrence of parasites in fillets of commercially important fish species affects both food quality and safety. Presently, the detection and removal of nematode parasites is done by inspection on a light table (candling) and manual trimming of the fillets. This operation is costly and time-consuming and is not effective for detecting and removing all the nematodes in the fillets. In the last decades, several alternative methods have been proposed, but these methods have failed to replace the candling method. A newly described method called imaging spectroscopy has produced promising results because the operator can record both spectral and spatial information from an object. In this work, we studied single-wavelength bands from a spectral image. Discrimination between nematodes and other objects in the fillets is dependent on the level of contrast. Quantification of the contrast in such images revealed that the level of contrast varied when different wavelengths were selected, and these variations are correlated with the absorption properties of the nematode. Visible light scatters greatly in fish muscle, generally complicating the detection of nematodes. In this study, light scattering was used in a way that reduces the background complexity in spectral images. When light scattering properties were used in a wavelength range different from the bulk of the nematode light absorption, spectral images with significantly higher contrast were produced.

Cold tolerance in sealworm ( Pseudoterranova decipiens ) due to heat-shock adaptations

Third-stage larvae of Pseudoterranova decipiens commonly infect whitefish such as cod, and the parasite can be transferred to humans through lightly prepared (sushi) meals. Because little is known about the nematodes cold tolerance capacity, we examined the nematodes ability to supercool, and whether or not cold acclimation could induce physiological changes that might increase its ability to tolerate freezing conditions. Even if third-stage Pseudoterranova decipiens larvae have some supercooling ability, they show no potential for freezing avoidance because they are not able to withstand inoculative freezing. Still, they have the ability to survive freezing at high subzero temperatures, something which suggests that these nematodes have a moderate freeze tolerance. We also show that acclimation to high temperatures triggers trehalose accumulation to an even greater extent than cold acclimation. Trehalose is a potential cryoprotectant which has been shown to play a vital role in the freeze tolerance of nematodes. We suggest that the trehalose accumulation observed for the cold acclimation is a general response to thermal stress, and that the nematodes moderate freeze tolerance may be acquired through adaptation to heat rather than coldness.

Antioxidant and Anti-Inflammatory Activities in Extracts from Minke Whale (Balaenoptera acutorostrata) Blubber

Intake of long-chain omega-3 polyunsaturated fatty acids (LC-n3-PUFA) is commonly recognized to reduce cardiovascular disease (CVD). In previous studies, cold-pressed whale oil (CWO) and cod liver oil (CLO) were given as a dietary supplement to healthy volunteers. Even though CWO contains less than half the amount of LC-n3-PUFA of CLO, CWO supplement resulted in beneficial effects on anti-inflammatory and CVD risk markers compared to CLO. In the present study, we prepared virtually lipid-free extracts from CWO and CLO and evaluated the antioxidative capacity (AOC) and anti-inflammatory effects. Oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) assays were used to test the AOC, and the results indicated high levels of antioxidants present in all extracts. The anti-inflammatory effects of the extracts were tested with lipopolysaccharide- (LPS-) treated THP-1 cells, measuring its ability to reduce cytokine and chemokine secretion. Several CWO extracts displayed anti-inflammatory activity, and a butyl alcohol extract of CWO most effectively reduced TNF-α (50%, p < 0.05) and MCP-1 (85%, p < 0.001) secretion. This extract maintained a stable effect of reducing MCP-1 secretion (60%, p < 0.05) even after long-term storage. In conclusion, CWO has antioxidant and anti-inflammatory activities that may act in addition to its well-known LC-n3-PUFA effects.

In-Pack Surface Pasteurization of Capture-Based, Pre-Rigor Filleted Atlantic Cod (Gadus morhua)

ABSTRACT In this study, we targeted the surface bacteria of high quality vacuum-packed cod loins to investigate how this affected the shelf life. After heat processing, the storage temperature was kept at 4°C in order to mimic supermarket shelf conditions. Samples that had undergone minimal heating regimes were compared with control samples as well with samples that were heated into the core. Shelf life was assessed based on the findings of a sensory analysis and on microbial growth data and supported by measurements of liquid loss and pH. Surface pasteurization of these samples seems to prolong shelf life only to a limited degree, even for samples with a low initial contamination level. Transportation of some bacteria into the filet, possibly during the intense rigor mortis progress triggered by the heat process, may have created a general flux of water in the samples. Underneath the surface, these bacteria are exposed to a limited thermal load and very little microbial competition. Surface pasteurization is an efficient method to reduce microbial contamination of many foodstuffs. In the case of fresh fish, however, surface pasteurization seems to have a limited effect due to the structure of the muscle and the subsequent storage condition.

Weakening Pin Bone Attachment in Fish Fillets Using High-Intensity Focused Ultrasound

High Intensity Focused Ultrasound (HIFU) can be used for the localized heating of biological tissue through the conversion of sound waves into heat. Although originally developed for human medicine, HIFU may also be used to weaken the attachment of pin bones in fish fillets to enable easier removal of such bones. This was shown in the present study, where a series of experiments were performed on HIFU phantoms and fillets of cod and salmon. In thin objects such as fish fillets, the heat is mainly dissipated at the surfaces. However, bones inside the fillet absorb ultrasound energy more efficiently than the surrounding tissue, resulting in a “self-focusing” heating of the bones. Salmon skin was found to effectively block the ultrasound, resulting in a significantly lower heating effect in fillets with skin. Cod skin partly blocked the ultrasound, but only to a small degree, enabling HIFU treatment through the skin. The treatment of fillets to reduce the pin bone attachment yielded an average reduction in the required pulling force by 50% in cod fillets with skin, with little muscle denaturation, and 72% in skinned fillets, with significant muscle denaturation. Salmon fillets were treated from the muscle side of the fillet to circumvent the need for penetration through skin. The treatment resulted in a 30% reduction in the peak pulling force and 10% reduction in the total pulling work, with a slight denaturation of the fillet surface.