Antarctic Krill Research Articles

Effects of sterilization intensity on the flavor profile of canned Antarctic krill (Euphausia superba): Moderate vs. excessive.

Selecting the appropriate sterilization intensity is crucial for the canning of Antarctic krill (Euphausia superba). This study investigated the effects of different sterilization intensities on volatile organic compounds (VOCs) of canned krill. Using gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS), which identified 45 and 36 VOCs, respectively. As the sterilization intensity was increased, the flavor profile became more stabilized; however, excessive sterilization led to the generation of off-flavor compounds. Eight key flavor markers were identified at different sterilization intensities. Cluster analysis could distinguish between samples obtained from low (F=6, 9) and high (F=12, 15) sterilization intensities. Odor Activity Value (OAV) analysis revealed that higher sterilization intensities led to the generation of fishy, fatty, and earthy notes. The findings suggest that sterilization at F=9 can best maintain the desired flavor characteristics. Overall, this work provides valuable insights into the optimization of the canning process of Antarctic krill.

Temporal variability in mortality and recruitment jointly influence the periodic fluctuations in Antarctic krill populations.

Antarctic krill (Euphausia superba) is a key part of the food web in the Southern Ocean ecosystem. Significant inter-annual fluctuations in population dynamics make stock assessment and management of its population a significant challenge. To better understand the population dynamics and fluctuation of krill, a survey-based age-structured catch-at-length model (ACL) is used to estimate the periodic fluctuations, based on length data collected from scientific surveys under the US Antarctic Marine Living Resources (AMLR) Program between 1992 and 2011. Spectral analysis of the model estimates revealed periodic fluctuations of 5-6 years in the recruitment, total abundance, and total biomass of krill in the Antarctic Peninsula, while spawning stock biomass exhibited periodic fluctuations of both 5-6 years and 2-3 years. The variations in krill total abundance and total biomass were mainly driven by recruitment, but the variation in spawning stock biomass was likely driven by both recruitment and time-varying, age-specific mortality. Our study contributes to a better understanding of the patterns and drivers of the periodic dynamics of Antarctic krill, which may help lead to improved assessments and fishery management for this important stock.

Dynamics of bacterial composition and association with quality formation and histamine accumulation during Antarctic krill fish sauce fermentation.

In this study, we first verified the feasibility of using Antarctic krill as a raw material for quick-brewed fish sauce, and the results showed that the amino acid nitrogen (AAN)and total soluble nitrogen(TSN) in the fermented 30days fish sauce met the national level fish sauce standards, but the histamine content exceeded the maximum limit value of histamine in fish sauce (400mg/kg) set by the International Codex Alimentarius Commission (CAC) and the European Union (EU). On this basis, the correlation between physicochemical indexes and bacterial communities during the fermentation of fish sauce was investigated using high-throughput sequencing, culture method. The correlation analyses revealed the relationship between bacterial communities and the quality and safety of fish sauce, and these studies will be helpful for the development of Antarctic krill fish sauce. The results showed that Staphylococcus were positively correlated with the accumulation of histamine and TVB-N during fermentation. This may be due to the presence of genes encoding histidine decarboxylase in Staphylococcus. Virgibacillus was positively correlated with the accumulation of AAN during fermentation. It was also found that Virgibacillus dokdonensis had a high protease activity (153.22U/mL) and Staphylococcus epidermidis was the most capable of producing histamine at 31.59mg/kg. Therefore histamine can be reduced by adding bacteria that inhibit the growth of Staphylococcus or degrade histamine as a fermenter.

A new dynamic distribution model for Antarctic krill reveals interactions with their environment, predators, and the commercial fishery in the south Scotia Sea region

A new dynamic distribution model for Antarctic krill reveals interactions with their environment, predators, and the commercial fishery in the south Scotia Sea region

Antarctic krill vertical migrations modulate seasonal carbon export.

Vertical migrations by marine organisms contribute to carbon export by consumption of surface phytoplankton followed by defecation in the deep ocean. However, biogeochemical models lack observational data, leading to oversimplified representation of carbon cycling by migrating organisms, such as Antarctic krill (Euphausia superba). Using a numerical model informed by 1 year of acoustic observations in the East Antarctic, we estimated the total particulate organic carbon (POC) flux from krill fecal pellets to be 9.68 milligrams of carbon per square meter per day (mg C m-2 day-1). A maximum of 25% of krill migrated to depths >200 m with a strong seasonality component, transporting <10% of the total krill POC flux (1.28 mg C m-2 day-1) to the deep ocean. Accurate carbon flux estimates are essential to inform climate policy and mitigation strategies, and models that include vertical migration will overestimate carbon export if this seasonality is not captured.

Antarctic Krill Protein Amyloid Fibrils as a Novel Iron Carrier for the Improvement of Iron Deficiency.

Iron fortification with food supplements remains the primary dietary strategy for improving iron deficiency anemia (IDA). This study used Antarctic krill protein for fibrillar design to form an Antarctic krill protein amyloid fibril (AKAF). The results indicated that peptides generated by proteolysis were a prerequisite for fibril assembly, forming elongated fibril structures and cross-linking upon heating. During this process, hydrogen bonds were rearranged, forming ordered β-sheet conformations (49.36 ± 0.21%); π-π stacking interactions among aromatic residues contributed to fibril formation. Further studies showed that AKAF effectively maintained iron in a bioavailable state and exhibited a high binding capacity (60.67 ± 0.69%). Moreover, the AKAF-iron complex markedly ameliorated hematological abnormalities in IDA mice, enhanced iron storage in the liver and spleen, and positively influenced the expression of iron homeostasis genes. This complex was also effective in alleviating gastric inflammatory responses induced by IDA. Overall, AKAF holds promise as an efficient iron delivery carrier.

Deep‐sea food‐web structure at South Sandwich Islands (Southern Ocean): net primary production as a main driver for interannual changes

Food‐webs are a major component of ecosystems and determinant for their functioning and structure. The food chain length (FCL) is a key feature of food‐webs and it is crucial for the resistance of the community to external stressors. The Southern Ocean (SO) food‐web is known for being short and dominated by an Antarctic krill Euphausia superba surplus, though recent studies proved the existence of different pathways. However, previous studies focused on the pelagic realm, with the deep‐sea and benthopelagic coupling remaining poorly understood. Using stable isotopes of δ13C and δ15N in muscle from individuals collected during toothfish fishing seasons 2020, 2021 and 2022, we 1) studied the bathyal food‐web structure at South Sandwich Islands; 2) evaluated the interannual variability of FCL; and 3) tested which FCL hypothesis better explains the variability at the SO deep‐sea. Our results show that this food‐web is composed of five trophic levels with both Patagonian Dissostichus eleginoides and Antarctic Dissostichus mawsoni toothfish as top predators. The 4th and 5th trophic levels are mostly composed of fish, while in the 3rd trophic level we mainly found cephalopods and crustaceans. The benthopelagic coupling occurs at different trophic levels, though mostly between the 3rd and 4th trophic level. The FCL varied between years, being in 2022 0.30 trophic levels shorter than in 2020. Our results suggest that food‐webs including a benthic component are longer than pelagic and coastal SO food‐webs. The FCL is positively related with net primary productivity, supporting that the productivity hypothesis explains the variability in FCL in SO bathyal food‐webs in slope and seamount areas. With climate change, the productivity in the SO is expected to increase which will increase the length of the food‐web. This change will affect the structure of the ecosystem, increasing assimilation losses, exposure to biomagnifying contaminants and changing nutrient cycles.

Hepatic and intestinal insights into the molecular mechanisms of dietary Antarctic krill-induced body color differentiation in Plectropomus leopardus.

Antarctic krill (Euphausia superba), which is rich in astaxanthin, has been widely utilized as a dietary supplement in fish aquaculture. Our study was to feed juvenile leopard coral grouper (Plectropomus leopardus) a diet containing 50% Antarctic krill, revealing significant body color differentiation between a reddened group (BKR) and a non-reddened group (BKB), followed by comparative analysis with the control group (BCon) without krill supplementation. Histological analysis and carotenoid content in the liver and intestine were differentially regulated in color-differentiated individuals. Transcriptomic profiling revealed differentially expressed genes (DEGs) among color-differentiated individuals, with up-regulated DEGs in BKR being linked to carotenoid uptake, metabolism, and transport. Key DEGs (acss2l, insig1, fabp7, and bco1) were validated through qRT-PCR and FISH. Additionally, WGCNA identified potential gene regulatory networks in the liver and intestine that were responsive to the body coloration. This study elucidates the molecular mechanisms by which Antarctic krill influences carotenoid-based body coloration, offering new insights into the application of Antarctic krill in aquaculture.

The formation pathway of flavor compounds in steamed Antarctic krill (Euphausia superba) based on untargeted metabolomics

The formation pathway of flavor compounds in steamed Antarctic krill (Euphausia superba) based on untargeted metabolomics

Arsenic toxicity in Antarctic krill oil and its impact on human intestinal cells.

Arsenic is a pervasive environmental pollutant that can bioaccumulate in Antarctic krill through the food chain, posing potential risks to human health. This study investigates the toxic effects of arsenic in Antarctic krill oil (AKO) on Caco-2 cells, focusing on oxidative stress and apoptosis induction. AKO is nutrient-rich and contains various arsenic species, including arsenite (As³⁺), arsenate (As⁵⁺), dimethyl arsinic acid (DMA), and arsenobetaine (AsB), each exhibiting different toxic potencies. Caco-2 cells were treated with arsenic standards and AKO to assess cell viability, lactate dehydrogenase (LDH) release, oxidative stress markers (superoxide dismutase [SOD], catalase [CAT], malondialdehyde [MDA], and glutathione peroxidase [GSH-Px]), reactive oxygen species (ROS) production, and apoptosis. Results demonstrated dose-dependent cytotoxicity, with As³ ⁺ being the most toxic, followed by As⁵⁺, DMA, and AsB. After 24 hours of exposure, cell viability in the high-concentration AKO group decreased to 63.95 %. Arsenic exposure elevated ROS levels, disrupted mitochondrial membrane potential, upregulated apoptosis-related genes such as Caspase-3, Caspase-9, and Bax, and downregulated the PI3K/AKT/mTOR signaling pathway. This study elucidates the mechanisms underlying arsenic toxicity in AKO and underscores its implications for food safety assessments.

The rapid fermentation of Euphausia superba sauce and revealing of the relationship between key flavor compounds and core microorganisms

The rapid fermentation of Euphausia superba sauce and revealing of the relationship between key flavor compounds and core microorganisms

The Effects of Cooking Methods on Gel Properties, Lipid Quality, and Flavor of Surimi Gels Fortified with Antarctic Krill (Euphausia superba) Oil as High Internal Phase Emulsions.

In this study, silver carp surimi products enriched with Antarctic krill oil high internal phase emulsions (AKO-HIPEs) were cooked using steaming (STE), microwave heating (MIC), and air-frying (AIR), respectively. The gel and flavor properties, lipid quality and stability were investigated. Compared to the MIC and AIR groups, the STE surimi gel added with HIPEs had better texture properties, exhibiting higher water-holding capacity and a more homogeneous structure, while the air-frying treatment resulted in visually brighter surimi products. The degree of lipid oxidation during cooking was in an order of STE < MIC < AIR as determined by electron paramagnetic resonance spectrometer and thiobarbituric acid reactive substances. HIPE-added surimi gels retained more nutrients and flavor when cooked by AIR compared to STE and MIC. Results imply that the texture properties and lipid stability of surimi products fortified with AKO-HIPEs were better than those of the oil group under any cooking method. In conclusion, surimi products added with AKO-HIPEs had better gel properties and retained more fatty acids and flavor than AKO-SO.

Abundance and estimated food consumption of seabirds in the pelagic ecosystem in the eastern Indian sector of the Southern Ocean

Quantification of abundance and food consumption of seabirds are key to understand characteristics and ecological functions of local marine ecosystem due to their abundance and diversity in foraging areas, habitat, behavior, mobility and prey types. This study aimed to quantify seabird abundance in pelagic areas in the eastern Indian sector of the Southern Ocean (80–150E°) based on an at-sea observational study conducted during the 2018/19 austral summer season. We estimated food consumption by seabirds based on their biomass, estimated field metabolic rates, number of days spent in the areas, and diet composition. Among the five functional seabird groups (penguins, albatrosses/giant petrels, shearwaters, petrels/Charadriiformes, prions/storm-petrels), shearwaters, non-Antarctic resident, were the most dominant taxa both by abundance (15,650,000 birds) and biomass (9,332 tonnes) in the study area during the summer. Most of the prey consumed by all seabirds in the area was presumed to be Antarctic krill (55,504 tonnes) and pelagic fishes (91,695 tonnes), such as myctophids. Although the total food consumption by the seabirds during the summer (209,973 tonnes) was lower than that reported in the Antarctic neritic areas (e.g., 753,000 tonnes in the neighboring Prydz Bay region), the higher proportion of non-resident shearwaters in biomass and estimated food consumption (85%) were the characteristic of the study area. Our results highlight the characteristics of the ecological importance of the study area in which seabirds consume Antarctic krill and pelagic fishes in the upper layer of the water column, and its nutrients are easily transported by the seabirds as their subcutaneous fat or stomach oil to the outside of the areas.

Carboxymethyl-β-cyclodextrin/chitosan complexes formed through electrostatic interactions to stabilize Pickering emulsions: A delivery vehicle for Antarctic krill oil

Carboxymethyl-β-cyclodextrin/chitosan complexes formed through electrostatic interactions to stabilize Pickering emulsions: A delivery vehicle for Antarctic krill oil

Encapsulation of Antarctic krill peptide by polysaccharide-based nanoparticles: Preparation, characterization, evaluation of stability and hypoglycemic activity

The aim of this study was to construct a chitosan quaternary ammonium salt (HTCC)/sodium alginate (SA) nanoparticle delivery system for the encapsulation of Antarctic krill peptide (AKP), with the goal of enhancing its stability and post-digestive hypoglycemic activity. Additionally, the effect of the content and encapsulation sequence of HTCC/SA on the structure and properties of AKP-loaded nanoparticles (AKP-loaded NPs) was investigated. As the content of the outermost wall material (HTCC) increased, the particle size of nanoparticles initially increased and then decreased. Concurrently, the zeta potential showed a trend of increase, ranging from -38.77 to 46.07 mV. When SA was used as the outermost wall material, the nanoparticles exhibited a smaller particle size (240.1 nm) and better dispersibility. Electrostatic interaction and hydrogen bonding were the major forces involved in the formation of AKP-loaded NPs. X-ray diffraction revealed that AKP was successfully encapsulated in an amorphous state. Scanning electron microscopy showed that AKP-loaded NPs had an elliptical or blocky appearance. Moreover, AKP-loaded NPs demonstrated good storage and temperature stability, while nanoparticles with HTCC in the outermost layer (HTCC:SA=2:1) showed good pH and ionic stability. During simulated digestion, AKP-loaded NPs inhibited the release of AKP in gastric fluid. Consequently, the hypoglycemic activity of digested AKP-loaded NPs was remarkably higher than unencapsulated AKP. Notably, the nanoparticles with HTCC in the outermost layer provided superior hypoglycemic activity. In summary, the polysaccharide-based delivery system exhibited great potential to improve the stability and post-digestive hypoglycemic activity of AKP, broadening its applications in the food and pharmaceutical industries.

Selenium-chelating peptides from the hydrolysates of degreased Antarctic krill (Euphausia superba) powder: Preparation, structural characterization and antioxidant properties

The huge resources of Antarctic krill (Euphausia superba) are considered one of the primary sources of high-quality protein for humans. Effective use of protein sources, active peptides, and functional foods is one of the best approaches for producing high-value Antarctic krill. In this present study, Antarctic krill powder was hydrolyzed and optimized to yield Antarctic krill peptides (AKPs), which were then combined with selenite (Se2+) to create Antarctic krill selenium-enriched peptides (Se-AKPs). The synthesized Se-AKPs showed a concentration of Se2+ was 185.66 ± 0.59 mg/g and a chelation rate of 23.60% ± 1.10%. The chelation successfully synthesized Se2+ with the NH2 peptide chain or amide bond of AKPs, resulting in a considerable reduction in the quantity of sulfur-containing, basic, and aromatic amino acids in peptides. Based on the phenotypic study, it was determined that Se-AKPs had distinct crystal structures. Meanwhile, antioxidant studies revealed that Se-AKPs had significant antioxidant activity, with half-maximal inhibitory concentration (IC50) values for 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and superoxide anion (O2−) radical scavenging of 0.149 mg/mL and 0.275 mg/mL, respectively. These results suggested that Se-AKPs might be a unique organic Se2+ supplement with antioxidant properties, and great potentials for use in medicine and the special food industry.

Extraction of high-quality Antarctic krill (Euphausia Superba) oil using low-temperature continuous phase-transition extraction equipment.

The aim of this study was to explore a processing method for efficient extraction of high-quality krill oil (KO) using a low-temperature continuous phase-transition extraction equipment (LCPE). The efficiency of lipid extraction and quality of KO and defatted krill meal (DKM) by LCPE were compared with those of supercritical CO2 and n-hexane extraction. Results showed that compared to other methods, extraction using LCPE had the highest lipid yield (21.72±0.34%), bioactive substances, and dimethyl sulfide (3.12±0.09mg/kg), the lowest oxidative deterioration. Moreover, compared to other methods, DKM extracted by LCPE had the lowest fat (<2%), the highest protein (>60%), and the best oxidative stability. These benefits would ensure easier transportation and better long-term storage, allowing for its application on distant-ocean fishing vessels. Therefore, LCPE is a method that allows for efficient extraction of high-quality KO.

Effects of Different Levels of Antarctic Krill Oil on the Ovarian Development of Macrobrachium rosenbergii.

Antarctic krill oil has been proven to be able to promote the ovarian development of crustaceans, but its optimal application dose and potential regulatory mechanism in Macrobrachium rosenbergii are still unclear. In this study, five isonitrogenous and isolipidic diets with gradient additions of Antarctic krill oil (0%, 1.5%, 3%, 4.5%, and 6%) were served exposed to 8 weeks of feeding. The results show that 3-4.5% Antarctic krill oil supplementation significantly increases the weight gain rate and specific growth rate of M. rosenbergii (p < 0.05). In addition, 3-4.5% Antarctic krill oil supplementation significantly increased the content of hemolymph vitellogenin (VTG) and the levels of reproductive hormones, including methyl farnesoate (MF), estradiol (E2), and progesterone (P4) (p < 0.05). The differences in ovarian index, oocyte volume, yolk granule deposition in oocytes, and the transcription levels of VTG genes in hepatopancreas and ovarian tissues demonstrated that the addition of Antarctic krill oil significantly promoted ovarian development and vitellogenesis, especially at the 4.5% addition level. In terms of molecular signaling, this study confirms that the retinol metabolic signaling pathway, MF signaling pathway, steroid hormone signaling pathway, and ecdysone signaling pathway, along with their specific molecules, such as Farnesoic acid-O-methyltransferase (FAMeT), retinoid x receptor (RXR), ecdysone receptor (EcR), and estrogen-related receptor (ERR), are involved in the regulation of the ovarian development of M. rosenbergii by adding Antarctic krill oil at appropriate doses. The findings indicate that the supplementation of 4.5% Antarctic krill oil in the diet is optimal for stimulating the secretion of reproductive hormones in female M. rosenbergii, thereby promoting vitellogenesis and ovarian development.

Four-liquid-phase system for simultaneous extraction and separation method of various active components in Antarctic krill crude oil extract

A four-liquid-phase system (FLPS) was serendipitously discovered when appropriate amounts of Antarctic krill crude oil extract (AKCOE), salt, water, a hydrophilic solvent, and a hydrophobic solvent were mixed. The system contained two hydrophobic phases and two hydrophilic phases, so the four main components of AKCOE (astaxanthin, phospholipids, proteins, and saccharides) could be simultaneously extracted into the various phases in a single step. For example, in a Na2CO3/ethanol/isooctane FLPS, 97.53% of phospholipids (the most important components) partitioned into the weakly hydrophobic phase, and astaxanthin, proteins, and saccharides simultaneously separated into the other three phases, with high yields (approximately 80%). Furthermore, the AKCOE phospholipids have been demonstrated to be key factors in FLPS formation, which provides an important reference for future designs of new FLPSs. This novel method is simple to operate and has the potential to scale-up; therefore, it may serve as a simple and efficient method for the separation and purification of biological mixtures containing many different polar components.

Physicochemical Properties and Metal Ion-Binding Capacity of Thermal-Induced Antarctic Krill Protein Aggregates under Different pH Conditions.

Protein properties can be modified by thermal treatment at different pH values, resulting in the formation of protein aggregates with diverse morphologies and functionalities. This study investigated the morphology of aggregates of Antarctic krill protein (AKPS) formed by thermal treatment (90 °C, 15 min) at pH 2, 3, 4, and 6-12, characterized the different morphologies of AKPS, and determined the metal ion (Ca2+, Fe2+, and Zn2+)-binding capacities. Results showed that heat treatment with different pH values generated various AKPS with distinct morphology and metal ion-binding abilities. AKPS have formed fibrils at pH ≤ 3, particles at pH 4-7, and amorphous aggregates at pH ≥ 8. Fibrous AKPS (pH 2) exhibited a high solubility (80.36%) and strong reducing effect on iron. The binding capacities of Ca2+ and Fe2+ reached 36.08% and 66.75%. Particulate AKPS (pH 6 and 7) primarily only showed Zn2+-binding capacity similar to that of casein phosphopeptide (17.33%). Amorphous AKPS (pH 9-11) displayed the optimal capacity to bind Zn2+ and Fe2+ (26.90% and 74.94%). The alterations in morphology and functional characteristics of AKPS permit the design of various nanostructures for food-derived mineral supplements, thus developing their potential for application in functional foods.