Krill Euphausia Superba Research Articles

Spatial distribution of Salpa thompsoni in the high Antarctic area off Adélie Land, East Antarctica during the austral summer 2008

The salp Salpa thompsoni has the potential to alter the Southern Ocean ecosystem through competition with krill Euphausia superba. Information on the reproductive status of S. thompsoni in the high Southern Ocean is thus essential to understanding salp population growth and predicting changes in the Southern Ocean ecosystem. We carried out stratified and quantitative sampling from the surface to a depth of 2000 m during the austral summer of 2008 to determine the spatial distribution and population structure of S. thompsoni in the Southern Ocean off Adélie Land. We found two salp species, S. thompsoni and Ihlea racovitzai, with the former being dominant. S. thompsoni was distributed north of the continental slope area, while I. racovitzai was observed in the neritic zone. Mature aggregates and solitary specimens of S. thompsoni were found south of the Southern Boundary of the Antarctic Circumpolar Current, suggesting that S. thompsoni is able to complete its life cycle in high Antarctic waters during the austral summer. However, S. thompsoni was sparsely distributed in the continental slope area, and absent south of the Antarctic Slope Front, suggesting that it is less competitive with krill for food in the slope area off Adélie Land, where krill is densely distributed during the austral summer.

Antihypertensive effects of Ile–Pro–Ile–Lys from krill (Euphausia superba) protein hydrolysates: purification, identification and in vivo evaluation in spontaneously hypertensive rats

Angiotensin I-converting enzyme (ACE) inhibitory peptide was purified from krill (Euphausia superba) protein hydrolysate using consecutive chromatography using an SP-Sephadex C-25 cation exchanger and then reverse-phase high-performance liquid chromatography. The purified ACE inhibitory peptide was identified to be Ile–Pro–Ile–Lys with a molecular weight of 470.3 Da by LC–MS/MS. The IC50 value of Ile–Pro–Ile–Lys was 57.4 µM. Lineweaver–Burk plots suggest that Ile–Pro–Ile–Lys acts as a non-competitive inhibitor against ACE. Oral administration of Ile–Pro–Ile–Lys significantly (p < 0.05) decreased the systolic blood pressure of spontaneously hypertensive rats. Collectively, an antihypertensive peptide purified from krill protein hydrolysates may be useful as a food ingredient for treatment of hypertension and related diseases.

At-Sea Distribution and Prey Selection of Antarctic Petrels and Commercial Krill Fisheries.

Commercial fisheries may impact marine ecosystems and affect populations of predators like seabirds. In the Southern Ocean, there is an extensive fishery for Antarctic krill Euphausia superba that is projected to increase further. Comparing distribution and prey selection of fishing operations versus predators is needed to predict fishery-related impacts on krill-dependent predators. In this context, it is important to consider not only predators breeding near the fishing grounds but also the ones breeding far away and that disperse during the non-breeding season where they may interact with fisheries. In this study, we first quantified the overlap between the distribution of the Antarctic krill fisheries and the distribution of a krill dependent seabird, the Antarctic petrel Thalassoica antarctica, during both the breeding and non-breeding season. We tracked birds from the world biggest Antarctic petrel colony (Svarthamaren, Dronning Maud Land), located >1000 km from the main fishing areas, during three consecutive seasons. The overall spatial overlap between krill fisheries and Antarctic petrels was limited but varied greatly among and within years, and was high in some periods during the non-breeding season. In a second step, we described the length frequency distribution of Antarctic krill consumed by Antarctic petrels, and compared this with results from fisheries, as well as from diet studies in other krill predators. Krill taken by Antarctic petrels did not differ in size from that taken by trawls or from krill taken by most Antarctic krill predators. Selectivity for specific Antarctic krill stages seems generally low in Antarctic predators. Overall, our results show that competition between Antarctic petrels and krill fisheries is currently likely negligible. However, if krill fisheries are to increase in the future, competition with the Antarctic petrel may occur, even with birds breeding thousands of kilometers away.

Temporal variation in isotopic composition of Pygoscelis penguins at Ardley Island, Antarctic: Are foraging habits impacted by environmental change?

Several studies have suggested that penguins are undergoing a major restructuring of their feeding habits and distribution after drastic climatic changes in the Antarctic Peninsula region. With the objective of estimating potential medium-term and inter-annual variations in trophic niche, we measured δ 15N and δ 13C in feather samples of pygoscelid penguins from museum specimens (1982–1984) and in blood and feather samples from 2009/10–2011 collected from animals on Ardley Island. Current penguin feathers had lower δ 13C and δ 15N values and were more similar to Antarctic krill values, than feathers in 1982–1984 and blood from 2009/10-2011. Moreover, δ 13C and δ 15N values from museum feathers and modern samples occupied a larger isotopic space in Gentoo Penguins (Pygoscelis papua), compared to Adelie Penguins (Pygoscelis adeliae) and Chinstrap Penguins (Pygoscelis antarctica). Our results from feathers samples indicated that penguins have decreased their consumption of fish and other prey of higher trophic levels in the early interbreeding period (EIBP), while increasing the amount of euphausiids (Antarctic krill Euphausia superba) taken. The isotopic values of the species suggest that foraging sites varied significantly over time and seasonally. We suggest that environmental changes may have modified the feeding habits of pygoscelid penguins, resulting in changed foraging behaviour in the EIBP, and altering the secondary prey consumption. Prey choice in breeding pygoscelid species is probably limited by the foraging range around the breeding colony and competitive exclusion between congeners.

Recovery of Chitin from Antarctic Krill (Euphausia superba) Shell Waste by Microbial Deproteinization and Demineralization

ABSTRACTA two-stage fermentation process of deproteinization and demineralization was used to purify chitin from Antarctic krill shell waste. Two bacterial cultures were isolated and tested for the degradation of krill shell waste. According to the morphological examination, physiological tests, and applied molecular techniques conducted, isolates were identified as Bacillus subtilis and Lactobacillus plantarum. At a temperature of 37°C, both strains were cultivated separately in flasks containing krill shell waste. At determined periods of time, deproteinization and demineralization of residuals were measured. For deproteinization tests, the liquid phase fermentation of krill shell waste showed protein removal of 88.9% after 60 h. For demineralization tests, the liquid phase fermentation of krill shell waste showed calcium carbonate removal of 84.6% after 72 h. Fourier transform infrared spectroscopy (FTIR) analysis of chitin prepared by the process was carried out and compared with spectra of samples treated by strong acids and bases.

Winter distribution and size structure of Antarctic krill Euphausia superba populations in-shore along the West Antarctic Peninsula

Antarctic krill Euphausia superba are a key component of food webs in the maritime West Antarctic Peninsula, and their life history is tied to the seasonal cycles of sea ice and primary production in the region. Previous work has shown a general in-shore migration of krill in winter in this region; however, the very near-shore has not often been sampled as part of these surveys. We investigated distribution, abundance, and size structure of krill in 3 fjordic bays along the peninsula, and in the adjacent Gerlache Strait area using vertically stratified MOCNESS net tows and ADCP acoustic biomass estimates. Krill abundance was high within bays, with net estimated densities exceeding 60 krill m-3, while acoustic estimates were an order of magnitude higher. Krill within bays were larger than krill in the Gerlache Strait. Within bays, krill aggregations were observed near the seafloor during the day with aggregations extending to the sediment interface, and exhibited diel vertical migration higher into the water column at night. We suggest these high winter krill abundances within fjords are indicative of an active seasonal migration by krill in the peninsula region. Potential drivers for such a migration include reduced advective losses and costs, and availability of sediment food resources within fjords. Seasonally near-shore krill may also affect stock and recruitment assessments and may have implications for managing the krill fishery in this area.

The opsin repertoire of the Antarctic krill Euphausia superba

The Antarctic krill Euphausia superba experiences almost all marine photic environments throughout its life cycle. Antarctic krill eggs hatch in the aphotic zone up to 1000m depth and larvae develop on their way to the ocean surface (development ascent) and are exposed to different quality (wavelength) and quantity (irradiance) of light. Adults show a daily vertical migration pattern, moving downward during the day and upward during the night within the top 200m of the water column. Seawater acts as a potent chromatic filter and animals have evolved different opsin photopigments to perceive photons of specific wavelengths. We have investigated the transcriptome of E. superba and, using a candidate gene approach, we identified six novel opsins. Five are r-type visual opsins: four middle-wavelength-sensitive (EsRh2, EsRh3, EsRh4 and EsRh5) and one long-wavelength-sensitive (EsRh6). Moreover, we have identified a non-visual opsin, the EsPeropsin. All these newly identified opsin genes were significantly expressed in compound eyes and brain, while only EsPeropsin and EsRh2 were clearly detected also in the abdomen. A temporal modulation in the transcription of these novel opsins was found, but statistically significant oscillations were only observed in EsRrh3 and EsPeropsin. Our results contribute to the dissection of the complex photoreception system of E. superba, which enables this species to respond to the daily and seasonal changes in irradiance and spectral composition in the Southern Ocean.

Community structure of under-ice fauna in relation to winter sea-ice habitat properties from the Weddell Sea

Climate change-related alterations of Antarctic sea-ice habitats will significantly impact the interaction of ice-associated organisms with the environment, with repercussions on ecosystem functioning. The nature of this interaction is poorly understood, particularly during the critical period of winter–spring transition. To investigate the role of sea-ice and underlying water-column properties in structuring under-ice communities during late winter/early spring, we used a Surface and Under Ice Trawl to sample animals and environmental properties in the upper 2-m layer under the sea ice in the northern Weddell Sea from August to October 2013. The area of investigation was largely homogeneous in terms of hydrography and sea-ice coverage. We hypothesised that this apparent homogeneity in the physical regime was mirrored in the structure of the under-ice community. The under-ice community was numerically dominated by the copepods Stephos longipes, Ctenocalanus spp. and Calanus propinquus (altogether 67 %), and furcilia larvae of Antarctic krill Euphausia superba (30 %). In spite of the apparent homogeneity of the environment, abundance and biomass distributions at our sampling stations indicated the presence of three community types, following a geographical gradient in the investigation area: (1) high biomass, krill-dominated in the west, (2) high abundance, copepod-dominated in the east, and (3) low abundance, low biomass at the ice edge. Combined analysis with environmental data indicated that under-ice community structure was correlated with sea-ice coverage, chlorophyll a concentration, and bottom depth. The heterogeneity of the Antarctic under-ice community was probably also driven by other factors, such as advection, sea-ice drift, and seasonal progression. The response of under-ice communities to changing sea-ice habitats may thus considerably vary seasonally and regionally.

Growth and shrinkage in Antarctic krill Euphausia superba is sex-dependent

The ability of Antarctic krill Euphausia superba Dana to withstand the overwintering period is critical to their success. Laboratory evidence suggests that krill may shrink in body length during this time in response to the low availability of food. Nevertheless, verification that krill can shrink in the natural environment is lacking because winter data are difficult to obtain. One of the few sources of winter krill population data is from commercial vessels. We examined length-frequency data of adult krill (>35 mm total body length) obtained from commercial vessels in the Scotia-Weddell region and compared our results with those obtained from a combination of science and commercial sampling operations carried out in this region at other times of the year. Our analyses revealed body-length shrinkage in adult females but not males during winter, based on both the tracking of modal size classes over seasons and sex-ratio patterns. Other explanatory factors, such as differential mortality, immigration and emigration, could not explain the observed differences. The same pattern was also observed at South Georgia and in the Western Antarctic Peninsula. Fitted seasonally modulated von Bertalanffy growth functions predicted a pattern of overwintering shrinkage in all body-length classes of females, but only stagnation in growth in males. This shrinkage most likely reflects morphometric changes resulting from the contraction of the ovaries and is not necessarily an outcome of winter hardship. The sex-dependent changes that we observed need to be incorporated into life cycle and population dynamic models of this species, particularly those used in managing the fishery.

Predatory impact of the myctophid fish community on zooplankton in the Scotia Sea (Southern Ocean)

Myctophids are the most abundant mesopelagic fishes in the Southern Ocean, although their trophic role within the predominantly krill-based food web in regions south of the Antarctic Polar Front (APF) is poorly resolved. This study therefore examined the diets of 10 species of myctophid fishes: Electrona antarctica, E. carlsbergi, Gymnoscopelus braueri, G. fraseri, G. nicholsi, Krefftichthys anderssoni, Protomyctophum bolini, P. tenisoni, P. choriodon and Nannobrachium achirus, in the Scotia Sea, together with their predatory impact on the underlying zooplankton community. Myctophids and their prey were sampled in different seasons by scientific nets deployed across the Scotia Sea from the sea-ice zone to the APF. Based on the percentage index of relative importance, myctophids had high overlap in their diets, although the data indicate dietary specialisation in some species. There was also a distinct switch in diet, from copepods to euphausiids and amphipods, with increasing myctophid size. Myctophid predation impacted daily copepod production by between 0.01 and 5%, with Calanus simillimus being most impacted. Total annual consumption of copepods was around 1.5 million t (Mt) per year. All myctophids preyed upon the euphausiid Thysanoessa spp., consuming ~12% of its daily productivity and around 4 Mt per year. However, only larger myctophid species preyed upon Antarctic krill Euphausia superba, consuming 2% of its daily productivity, which could amount to as much as 17 Mt per year. Themisto gaudichaudii was also an important dietary component, with 4% of its daily productivity being consumed, amounting to around 2 Mt per year. This study demonstrates that myctophids link secondary productivity to higher predators both through krill-dependent and krill-independent trophic pathways.

Phosphorylated Peptides from Antarctic Krill (Euphausia superba) Prevent Estrogen Deficiency Induced Osteoporosis by Inhibiting Bone Resorption in Ovariectomized Rats.

In the current study, we investigated the improvement of phosphorylated peptides from Antarctic krill Euphausia superba (PP-AKP) on osteoporosis in ovariectomized rats. PP-AKP was supplemented to ovariectomized Sprague-Dawley rats for 90 days. The results showed that PP-AKP treatment remarkably prevented the reduction of bone mass and improved cancellous bone structure and biochemical properties. PP-AKP also significantly decreased serum contents of tartrate-resistant acid phosphatase (TRACP), cathepsin K (Cath-k), matrix metalloproteinases-9 (MMP-9), deoxypyridinoline (DPD), C-terminal telopeptide of collagen I (CTX-1), Ca, and P. Mechanism investigation revealed that PP-AKP significantly increased the osteoprotegerin (OPG)/receptor activator of nuclear factor κB ligand (RANKL) ratio in mRNA expression, protein expression, and serum content. Further research suggested that NF-κB signaling pathways were inhibited by suppressing the mRNA and protein expressions of nuclear factor of activated T-cells (NFATc1) and tumor necrosis factor receptor-associated factor 6 (TRAF6), diminishing the mRNA expression and phosphorylation of nuclear factor κB p65 (NF-κB p65), three key transcription factors in NF-κB pathways. These results suggest that PP-AKP can improve osteoporosis by inhibiting bone resorption via suppressing the activation of osteoclastogenesis related NF-κB pathways.

Modeling the transport and fate of euphausiids in the Ross Sea

Antarctic krill (Euphausia superba) and crystal krill (Euphausia crystallorophias), important components of the Ross Sea food web, differ in their population distribution. The objective of this study was to determine whether these differing distributions result primarily from differences in spawning locations, larval development times, and transport by the Ross Sea circulation. To address this objective, Lagrangian particle tracking experiments were used to simulate the transport of larvae of Antarctic krill and crystal krill. The particle simulations showed that regions providing inputs of Antarctic krill to the Ross Sea were along the outer shelf/slope. Crystal krill transport and retention were along the shallow banks on the outer Ross Sea shelf. Particles initialized in the inner shelf off Victoria Land showed high retention in the region south and along the Terra Nova Bay polynya, with timescales consistent with development times of crystal krill. These results suggest that the cyclonic circulation over the shelf contributes significantly to the dispersion and retention of crystal krill in parts of the inner Ross Sea continental shelf that overlaps with regions with high concentrations of krill-dependent top predators. The westward circulation along the shelf break contributes to the transport and aggregation of Antarctic krill in regions where Circumpolar Deep Water is observed on the outer continental shelf and along the shelf break. The transport pathways and connectivity obtained from this study provide a baseline for assessing the effects of projected changes in the Ross Sea circulation on the distribution of two important krill species.

Assessing the structure and temporal dynamics of seabird communities: the challenge of capturing marine ecosystem complexity.

Summary Understanding interspecific interactions, and the influences of anthropogenic disturbance and environmental change on communities, are key challenges in ecology. Despite the pressing need to understand these fundamental drivers of community structure and dynamics, only 17% of ecological studies conducted over the past three decades have been at the community level.Here, we assess the trophic structure of the procellariiform community breeding at South Georgia, to identify the factors that determine foraging niches and possible temporal changes. We collected conventional diet data from 13 sympatric species between 1974 and 2002, and quantified intra‐ and inter‐guild, and annual variation in diet between and within foraging habits. In addition, we tested the reliability of stable isotope analysis (SIA) of seabird feathers collected over a 13‐year period, in relation to those of their potential prey, as a tool to assess community structure when diets are diverse and there is high spatial heterogeneity in environmental baselines.Our results using conventional diet data identified a four‐guild community structure, distinguishing species that mainly feed on crustaceans; large fish and squid; a mixture of crustaceans, small fish and squid; or carrion. In total, Antarctic krill Euphausia superba represented 32%, and 14 other species a further 46% of the combined diet of all 13 predators, underlining the reliance of this community on relatively few types of prey. Annual variation in trophic segregation depended on relative prey availability; however, our data did not provide evidence of changes in guild structure associated with a suggested decline in Antarctic krill abundance over the past 40 years.Reflecting the differences in δ15 N of potential prey (crustaceans vs. squid vs. fish and carrion), analysis of δ15 N in chick feathers identified a three‐guild community structure that was constant over a 13‐year period, but lacked the trophic cluster representing giant petrels which was identified using conventional diet data.Our study is the first in recent decades to examine dietary changes in seabird communities over time. Conventional dietary analysis provided better resolution of community structure than SIA. However, δ15 N in chick feathers, which reflected trophic (level) specialization, was nevertheless an effective and less time‐consuming means of monitoring temporal changes.

The other krill: overwintering physiology of adult Thysanoessa inermis (Euphausiacea) from the high‑Arctic Kongsfjord

Polar environments like the high-Arctic Kongsfjord are characterized by pronounced seasonality leading to strong variations in primary production. Food sources are particularly scarce during winter. Herbivorous krill, such as the arcto-boreal Thysanoessa inermis, are key components in the ecosystem of Kongsfjord and strongly rely on phytoplankton as a food source. During the polar night such species must therefore be adapted to survive long periods without sig- nificant nutritional input. We investigated physiological mechanisms and the allocation of energy resources to try to explain how T. inermis manages to survive the Arctic winter. Adult specimens caught in late summer were kept under starvation conditions for 28 d. Changes in metabolic rates (respiration and excretion) and biochemical composition (protein, lipid and fatty acid analyses) were monitored. In contrast to the Antarctic krill Euphausia superba and the subtropical E. hanseni, the arcto-boreal species did not reduce metabolism but utilized lipid reserves for sur- vival. Assessed from total lipid stores and energy demand, the potential survival period was esti- mated at 63 d without food uptake, which is not sufficient to survive the entire winter. Results were compared to specimens that overwintered in situ and were discussed in relation to other euphausiids. In conclusion, T. inermis is well adapted to survive the Arctic winter provided that alternative food sources are available, but has a different strategy to cope with starvation than krill species from other latitudes.

Parameterising a generic model for the dynamic energy budget of Antarctic krill Euphausia superba

Dynamic Energy Budget (DEB) theory is a generic and comprehensive framework for understanding bioenergetics over the entire life cycle of an organism. Here, we apply a simplified model derived from this theory (DEBkiss) to Antarctic krill Euphausia superba. The model was parameterised using growth curves, and conversion factors for body composition and length-weight relationships. Subsequently, the model was used to predict a series of life-history traits (as function of body size) that were not used for parameterisation: instantaneous growth rates, ingestion and respiration rates, weight loss on starvation, and the number of eggs produced at spawning. Within the DEB framework, these traits are not intrinsic properties of the organism, but tightly coupled model outputs that depend on body size, life stage, and environmental conditions. Overall, the model predictions are consistent with the patterns in the (rather uncertain) observations, lending credence to the model assumptions underlying the DEBkiss model. More work is needed to fully elucidate the bioenergetics of the E. superba life cycle, but this analysis demonstrates how a dynamic budgeting framework can ensure consistency among the different life-history traits. Thereby, such models help in the interpretation of experimental results and the comparison of species, but can also form the basis for predicting population dynamics and the impacts of stressors.

Winter preconditioning determines feeding ecology of Euphausia superba in the Antarctic Peninsula

We examined the feeding ecology and lipid composition of Antarctic krill Euphausia superba around the northern Antarctic Peninsula from 2001 to 2012. We used lipid biomarkers to quantify feeding patterns and relate the variability in biomarkers to environmental conditions that structure the phytoplankton community. Fatty acid profiles varied among years, with some years dominated by lipids indicative of herbivory, while other years were indicative of greater omnivory. Principal component analysis of 60 fatty acids showed that 3 principal components (PCs) explained approximately 50% of the variability in fatty acid profiles. The first PC separated the fatty acid indi- cators along a herbivoryomnivorycarnivory gradient. Correlations between the gradient of her- bivory and carnivory, as summarized by the first PC, were found with both winter sea ice extent (r = 0.55, p < 0.01) and with ENSO conditions the previous winter (r = 0.88, p < 0.001). These findings suggest that climatic conditions during the late winter precondition the pelagic ecosystem around the Antarctic Peninsula, impacting the trophic ecology of Antarctic krill the following summer.

Contrasting specialist and generalist patterns facilitate foraging niche partitioning in sympatric populations of Pygoscelis penguins

Specialization is a common mechanism of niche differentiation that can lead to eco- logical co-existence among species. However, species with specialized habitat or dietary require- ments often exhibit a high degree of sensitivity to environmental change. Understanding patterns of specialization and niche segregation among Antarctic marine predators is of increased impor- tance because of recent climate-driven reductions in a key prey species, Antarctic krill Euphausia superba. We examined the stomach contents and stable isotope values of sympatric chinstrap Pygoscelis antarctica and gentoo P. papua penguins across 5 breeding seasons at Cape Shirreff, Livingston Island, Antarctica. Our goal was to examine foraging niche segregation and the degree of specialization between species during the chick-rearing period. Dietary and isotopic foraging niches indicated consistent niche partitioning with higher krill consumption and greater use of off- shore foraging habitats by chinstrap relative to gentoo penguins. While chinstrap penguin diets were dominated by krill with little variation, gentoo penguins exhibited broader dietary and iso- topic niches with a higher degree of variation. There was little evidence that shifts in the availabil- ity of adult krill influenced penguin diets or foraging niches during our study, though the contrast- ing foraging strategies identified provide insight into the differing population trends observed between penguin species. The narrower foraging niche observed in declining chinstrap penguin populations indicates that they are likely highly sensitive to declines in the abundance of Antarc- tic krill. In contrast, the generalist niche exhibited by recently expanding gentoo penguin popula- tions is likely better suited to the rapidly changing environmental conditions in the Antarctic Peninsula.

Isotopic Values of Antarctic Krill in Relation to Foraging Habitat of Penguins

Abstract Antarctic Krill Euphausia superba is a key component of the Antarctic coastal marine ecosystem. Investigations into stable isotopic values of krill in predation hotspots are important in facilitating our understanding of the feeding environments of krill in a local coastal ecosystem. In this study we investigated stable isotopic values and maturity and size composition of krill at a small spatial scale, by logging GPS tracks of five Chinstrap Pygoscelis antarcticus and seven Gentoo P. papua penguins, and analyzing their stomach contents. The study was conducted at a penguin colony on Barton Peninsula, King George Island, Antarctica. The main food item of both species was Antarctic Krill (>98% wet mass). One Chinstrap and four Gentoo penguin foraging trips were classified as “on-shelf” trips, and four Chinstrap and three Gentoo Penguin foraging trips were classified as “off-shelf” trips. Krill collected from off-shelf trips had higher δ 15N (4.22±0.28‰) values than those from on-shelf trips (3.78±...

Development of Reaction Flavors with Enzymatic Hydrolysate of Krill Euphausia superba in Ramen Sauce

Abstract Antarctic krill Euphausia superba is an excellent potential source of food protein. We used enzymatic hydrolysate of Antarctic krill and 10 other precursors to seek the optimum krill reaction flavor and apply to ramen sauce. Krill concentrate and powder were compared by sensory evaluation. The krill powder performed better preference, and was added to ramen sauce, which itself performed better than a commercial shrimp flavored sauce. In total, 47 and 39 volatile compounds were identified from krill con-centrate and powder, respectively. Both products contained many aldehydes and sulfur-containing compounds. The whisky flavor of aldehydes lowered the shrimp flavor of the krill concentrate. Sulfur-containing compounds were found in krill powder, confirm-ing the results from sensory evaluation. Key words: Antarctic krill, Reaction flavor, Ramen sauce, Volatile compounds, Euphausia superba Introduction Antarctic krill Eupausia superba is a shrimp like zooplank -ton which is found in cold (-2°C to 2°C) seawater in the Ant-arctic region. Some estimates put the amount of harvestable krill at more than one billion tons (Oh et al., 2011); thus, it is a promising future food resource and bioactive ingredients.Antarctic krill is composed of 79.1% moisture, 13.1% protein, 4.0% lipids and 2.7% ash, chitin, and chitosan (Lee, 1999). It is a rich source of high-quality protein, with an es-timated protein content of 60-65% by dry weight. Like other animal proteins, the protein derived from krill is complete, containing all nine of the essential amino acids required by hu-mans. Krill also offers the advantage of being high in omega-3 polyunsaturated fatty acids (ω-3 PUFAs) such as eicosapen-taenoic acid (EPA) and docosahexaenoic acid (DHA) (Tou et al., 2007). Techniques are needed for making krill palatable to humans; currently, most harvested krill is used only as fish bait.Various studies have reported on krill’s composition and an-tioxidative activity (Kim et al., 2012); its application to Teri-yaki sauce, soy sauce, and soybean paste and patties (Kim et al., 2013; Lee et al., 1984; Kim et al., 2009; Lee et al., 1985); and its fluoride content (Park et al., 1988). However, there has been little research on krill reaction flavor. Therefore, it is im-portant to study this issue before using krill as an ingredient.Generally, the term “process flavor” is used to define a group of flavors or flavoring ingredients that are produced from heating precursors. The reaction technique is usually used to produce meat and savory flavors (Manley, 1994). Studies on seafood reaction flavors from shrimp, tuna, and krill have been published. In particular, krill reaction flavor contains abundant sulfur-containing compounds, pyrazines and furans, yielding showing meaty and boiled flavors (Kim, 2011). However, studies on reaction flavor in seafood are chal-lenging due to the foods’ fishy smell.Ramen sauce is a typical seasoning in processed foods and provides the “ramen” taste. It is made with salt, seasonings

Monthly Variations in the Nutritional Composition of Antarctic Krill Euphausia superba

Abstract The proximate composition and various specific components of Antarctic krill Euphausia superba , in the catch season between March and August were investigated. Frozen krill were freeze-dried and milled. The proximate composition comprised water, proteins, fats, ash, fatty acids, and amino acids, while the specific components were vitamins, minerals, nucleotides, betaine, and astaxanthin. The moisture content of the krill ranged from 77 to 80%, with the highest value in June, and the ash content was be-tween 12 and 13%. The protein content was lowest in May, and the fat content was 18–19%, with the highest value in March. The amino acid content varied according to the season: taurine and glycine were highest in August; β-alanine was higher in April and May; and arginine, ornithine, and lysine were highest in March. The unsaturated fat content was ~50% and omega-3 fatty acids were highest in June. Oil-soluble vitamins A and E were highest in March, and the water-soluble vitamin content was less than that of oil-soluble vitamins. The mineral content was highest in June, and the most abundant mineral was sodium at 235.60 mg/100 g krill. The content of other minerals was lowest (2.94 mg/100 g) in April, except for lead. The nucleotide content was highest in July, while the betaine content was highest in April and lowest in June. The astaxanthin content was highest in May and ranged from 6 to 10 ppm in other months.