Identification of volatile compounds in Antarctic krill (Euphausia superba) using headspace solid-phase microextraction and GC-MS

Analysis of Key Aroma Compound Changes in Grass Carp Fillets during Cold Storage Using Two-Dimensional Gas Chromatography-Olfactometry-Mass Spectrometry and Odor Activity Value

This study analyzed the changes in key aroma compounds in grass carp fillets during cold storage using aroma extract dilution analysis, odor activity values, and aroma recombination. A total of 11, 13, and 14 volatile compounds were recombined to construct recombination models representing the odor of fillets at 0, 3, and 7 days of cold storage, respectively. The key aroma compounds in fresh fillets included hexanal, (Z)-4-heptenal, nonanal, (E,E)-2,4-octadienal, (E,Z)-2,6-nonadienal, (E)-2-nonenal, decanal, (E)-2-decenal, (E,E)-2,4-decadienal, 1-octen-3-ol, and 2,3-pentanedione. Moreover, (E)-2-octenal, 2-cyclopenten-1-one, γ-dodecalactone, and octanoic acid became the key aroma compounds after 3 and 7 days of refrigeration, respectively. (Z)-4-Heptenal, (E,Z)-2,6-nonadienal, (E)-2-nonenal, decanal, and (E,E)-2,4-decadienal indicated the deterioration in flavor quality of fillets, which rose by 38.29 μg/kg (0-7 days). This study clarifies the key aroma compounds and characteristic compounds responsible for odor changes during the cold storage of fillets, establishing a basis for future improvement in odor quality during cold storage.

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.

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

This study investigated the impact of steaming on the flavor and metabolic profile of Antarctic krill, aiming to elucidate the pathways responsible for flavor development and metabolic shifts during processing. HS-SPME-GC-MS identified key volatile compounds, including alcohols, aldehydes, ketones and so on. The results demonstrated a significant increase in nonanal content from 2.23 ± 0.06 μg/kg to 8.14 ± 1.26 μg/kg after steaming. The formation pathways of two key flavor compounds, nonanal and 1-octen-3-ol, were attributed to fatty acid degradation. Hierarchical clustering and volcano plot showed metabolic shifts between raw and steamed krill, with differential metabolites like hydroquinone and gamma-aminobutyric acid emerging as key contributors to flavor changes. Furthermore, metabolic network further linked these shifts to reactions involving amino acids, nucleotide and other compounds during steaming, impacting the overall taste.

Construction of foam-templated Antarctic krill oil oleogel based on pea protein fibril and ι-carrageenan

Edible plant-based oleogels with zero trans-fat are promising solid fat substitutes. In this study, Antarctic krill oil (AKO) oleogels prepared from pea protein fibril (PPF) and ι-carrageenan (CG) by foam-templated method were developed for the first time. The modulation of the ratio of PPF and CG concentration on the structure and properties of foam, cryogel and oleogel was investigated and the potential formation mechanism of the foam-templated oleogel was explained. The results demonstrated that the addition of CG significantly decreased the foam size and enhanced the foam stability. The oil absorption and oil holding ability of the dense and reticular porous structure of the cryogel was demonstrated. Fourier infrared spectroscopy confirmed the interaction between PPF and CG involved in the formation of cryogels. With the addition of CG, the network structure and mechanical strength of the cryogel were reinforced, leading to more compact pores and higher capillary suction, which was appropriate for the establishment of good viscoelastic semi-solid oleogels. In addition, the oleogel was effective in masking the fishy odor of AKO. The significance of this study lies in its provision of a novel approach to the preparation of the foam-templated oleogel with PPF and CG as the oleogelators.

Different stages of flavor variations among canned Antarctic krill (Euphausia superba): Based on GC-IMS and PLS-DA

The aim of the present study was to explore changes in the profile of volatile compounds (VCs) in canned Antarctic krill (Euphausia superba) at different processing stages using partial least squares discriminant analysis (PLS-DA) and gas chromatography-mass spectrometry (GC-IMS). A total of 43 VCs were detected using GC-IMS in all krill meat samples, which included mainly alcohols, aldehydes, ketones, esters, and furans. Considering the different processing stages, the highest variation in VCs and the highest VC content were observed in krill meat which underwent both blanching and salt addition. PLS-DA further revealed flavor differences in canned Antarctic krill meat at different processing stages, with octanal, 2-hexanol, 2-octane, 2,3,5-trimethyl pyrazine, and cis-3-hexanol as the main contributors to observed differences in VC profiles. These findings contribute to the production of high-quality canned krill meat, enhancing its flavor quality and providing a feasible theoretical basis for future krill meat pretreatment and industry development.

Prevention of the Quality Degradation of Antarctic Krill (Euphausia superba) Meal through Two-Stage Drying

To achieve a krill meal of high quality, a two-stage drying involving hot-air drying and vacuum drying was investigated. Five experimental groups were established according to the different drying conditions in the second stage, including 95 °C and 101 kPa, 95 °C and 60 kPa, 75 °C and 101 kPa, 75 °C and 60 kPa, and 75 °C and 20 kPa. The results showed that reducing the drying temperature and vacuum pressure in the second stage had a significant impact on the drying characteristics, sensory quality, and bioactive compounds of krill meal. Among all five groups, the drying condition of 75 °C and 60 kPa maintained a high drying rate while preserving a phospholipid content of 30.01 mg/kg and an astaxanthin content of 37.41 mg/kg. It also effectively reduced the isomerization of astaxanthin and the oxidation of unsaturated fatty acids. These results suggested that the two-stage drying method may contribute to the production of high-quality krill meal.

Advances in encapsulation systems of Antarctic krill oil: From extraction to encapsulation, and future direction

Antarctic krill oil (AKO) is highly sought after by consumers and the food industry due to its richness in a variety of nutrients and physiological activities. However, current extraction methods are not sufficient to better extract AKO and its nutrients, and AKO is susceptible to lipid oxidation during processing and storage, leading to nutrient loss and the formation of off-flavors and toxic compounds. The development of various extraction methods and encapsulation systems for AKO to improve oil yield, nutritional value, antioxidant capacity, and bioavailability has become a research hotspot. This review summarizes the research progress of AKO from extraction to encapsulation system construction. The AKO extraction mechanism, technical parameters, oil yield and composition of solvent extraction, aqueous enzymatic extraction, supercritical/subcritical extraction, and three-liquid-phase salting-out extraction system are described in detail. The principles, choice of emulsifier/wall materials, preparation methods, advantages and disadvantages of four common encapsulation systems for AKO, namely micro/nanoemulsions, microcapsules, liposomes and nanostructured lipid carriers, are summarized. These four encapsulation systems are characterized by high encapsulation efficiency, low production cost, high bioavailability and high antioxidant capacity. Depending on the unique advantages and conditions of different encapsulation methods, as well as consumer demand for health and nutrition, different products can be developed. However, existing AKO encapsulation systems lack relevant studies on digestive absorption and targeted release, and the single product category of commercially available products limits consumer choice. In conjunction with clinical studies of AKO encapsulation systems, the development of encapsulation systems for special populations should be a future research direction.

Pyrazines in food samples: Recent update on occurrence, formation, sampling, pretreatment and analysis methods

Pyrazines are a class of active aromatic substances existing in various foods. The accumulation of pyrazines has an impact on flavor and quality of food products. This review encompasses the formation mechanisms and control strategies of pyrazines via Maillard reaction (MR), including the new reactants and emerging techniques. Pyrazines characteristics are better understood through the developed sample pretreatments and detection methods. Herein, an in-depth review of pretreatments and analysis methods since 2010 is presented to explore the simple, fast, green, and effective strategies. Sample preparation methods include liquid phase extraction, solid phase extraction, supercritical fluid extraction, and microextraction methods such as liquid phase microextraction, and solid phase microextraction, etc. Detections are made by chromatographic methods, and sensors, etc. Advantages and limitations are discussed and compared for providing insights to further studies.

Optimization of ultrasonic-assisted extraction of flavor compounds from shrimp by-products and characterization of flavor profile of the extract

This study aimed to optimize the ultrasonic-assisted extraction conditions of flavor compounds from white shrimp heads (WSHs). The effects of sonication amplitude, sonication time, and solvent-to-solid ratio on the extraction yield (EY) of flavor compounds and the degree of protein modification (DPM) were evaluated by Box-Behnken design and response surface methodology (RSM). The optimum EY (40.87 %) and DPM (26.28 %) were obtained at amplitude, time, and solvent-to-solid ratios of 63.2 %, 20.5 min, and 20.8 mL/g, respectively. The optimum DPM value indicates that sonication markedly influenced the protein denaturation, as evidenced by the higher TCA soluble protein content. Further, we also investigated the taste active composition of ultrasonic extract of shrimp head (USH). Results show that the equivalent umami concentration (EUC) value was significantly (p < 0.05) increased in the ultrasonic extract of shrimp head (USH) (55.44 ± 3.25 g MSG/100 g) compared to the control shrimp head extract (CSH) (8.32 ± 1.07 g MSG/100 g). This study also deals with the development of shrimp flavor concentrate (SFC) using USH by the conventional heating process. Sensory evaluation of SFC revealed that the shrimp-like aroma and umami taste characteristics were predominant. Thus, USH's improved umami taste composition demonstrates its potential utilization for producing SFC with higher EUC.

Characteristic flavor of Antarctic krill (Euphausia superba) and white shrimp (Penaeus vannamei) induced by thermal treatment

For the good acceptance and preference of heated shrimp, characteristic flavor composition analysis was necessary. The sensory evaluation, electronic tongue, electronic nose, and gas chromatography-ion mobility spectrometry were employed in this study. After steaming or cooking, the sensory scores of Antarctic krill (KM) and white shrimp (PM) were significantly increased, and five basic tastes were remarkably changed by electronic tongue analysis. Free glycine level increased from 86.48 to 687.12 mg/100 g in PM after steaming, but no significant changes in KM. 5'-nucleotides in heated PM were higher than those in heated KM. In two kinds of shrimp, inorganic ions and lactic acids contents exhibited the decrease trends after cooking, and the response intensities of S4, S5, and S6 showed increase trends after steaming. Nonanal, benzaldehyde, (Z)-3-hexen-1-ol, 1-8-cineol and limonene were produced by thermal treatment. Therefore, characteristic flavor formation was related to thermal treatment.

Behavioural responses of humpback whales to food-related chemical stimuli

Baleen whales face the challenge of finding patchily distributed food in the open ocean. Their relatively well-developed olfactory structures suggest that they could identify the specific odours given off by planktonic prey such as krill aggregations. Like other marine predators, they may also detect dimethyl sulfide (DMS), a chemical released in areas of high marine productivity. However, dedicated behavioural studies still have to be conducted in baleen whales in order to confirm the involvement of chemoreception in their feeding ecology. We implemented 56 behavioural response experiments in humpback whales using two food-related chemical stimuli, krill extract and DMS, as well as their respective controls (orange clay and vegetable oil) in their breeding (Madagascar) and feeding grounds (Iceland and Antarctic Peninsula). The whales approached the stimulus area and stayed longer in the trial zone during krill extract trials compared to control trials, suggesting that they were attracted to the chemical source and spent time exploring its surroundings, probably in search of prey. This response was observed in Iceland, and to a lesser extend in Madagascar, but not in Antarctica. Surface behaviours indicative of sensory exploration, such as diving under the stimulus area and stopping navigation, were also observed more often during krill extract trials than during control trials. Exposure to DMS did not elicit such exploration behaviours in any of the study areas. However, acoustic analyses suggest that DMS and krill extract both modified the whales' acoustic activity in Madagascar. Altogether, these results provide the first behavioural evidence that baleen whales actually perceive prey-derived chemical cues over distances of several hundred metres. Chemoreception, especially olfaction, could thus be used for locating prey aggregations and for navigation at sea, as it has been shown in other marine predators including seabirds.