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Antarctic krill (Euphausia superba) is a source for compounds of high nutritive value. Within that process of extraction, exocuticles (shells) accumulate which are currently disposed. A valorization of the compounds of the exocuticle such as chitosan would be beneficial to avoid waste and to obtain a versatile polymer at the same time. In contrast to previous investigations focusing on chitosan production from whole krill, we applied and optimized process stages of the chitosan production from the exocuticles, performing a comprehensive analytical evaluation of the whole process, the side streams and the products for the first time. Degreasing was the first step resulting in a krill oil yield of 6.2% using ethanol. The fatty acid profile exhibited high contents of phospholipids (21.2%). Citric acid offered a demineralization efficiency of 93%. Deproteinization investigation revealed 2 M NaOH and 90°C for 2.5 h to be the best parameters, resulting in a deproteinization efficiency of 99.9% and a chitin content of 92.8%. The spectroscopic investigation indicated that the chitin has a crystallinity index of 76% and an acetylation degree of 88%. The deacetylation degrees of the resulting chitosans is determined to be 74%–88%, the molecular weight ranges from 102 to 126 kDa. [ABSTRACT FROM AUTHOR]

The properties of a thin sheet of poly(dimethylsiloxane) (PDMS) membrane as an extraction phase were examined and compared to solid-phase microextraction (SPME) PDMS-coated fiber for application to semivolatile analytes in direct and headspace modes. This new PDMS extraction approach showed much higher extraction rates because of the larger surface area to extraction-phase volume ratio of the thin film. Unlike the coated rod formats of SPME using thick coatings, the high extraction rate of the membrane SPME technique allows larger amounts of analytes to be extracted within a short period of time. Therefore, higher extraction efficiency and sensitivity can be achieved without sacrificing analysis time. In direct membrane SPME extraction, a linear relationship was found between the initial rate of extraction and the surface area of the extraction phase. However, for headspace extraction, the rates were somewhat lower because of the resistance to analyte transport at the sample matrix/headspace barrier. It was found that the effect of this barrier could be reduced by increasing either agitation, temperature, or surface area of the sample matrix/headspace interface. A method for the determination of PAHs in spiked lake water samples was developed based on the membrane PDMS extraction coupled with GC/MS. A linearity of 0.9960 and detection limits in the low-ppt level were found. The reproducibility was found to vary from 2.8% to 10.7%.

Krill is a valuable sustainable resource of omega-3 fatty acids and protein, which may be processed into a krill powder for human consumption. The objective of this study was to investigate the stability of krill powder when stored for up to 12 months at room temperature. In addition, the effect of packaging in vacuum was observed. The stability was assessed by changes in concentrations of lipid classes, antioxidants, pyrroles and lipid, and Strecker-derived volatiles. Some degradation occurred during storage at room temperature. Thus, a minor increase in volatiles, an increase in free fatty acids and a concomitant decrease in antioxidants, tocopherol, and astaxanthin was observed. In addition, there was a minor decrease in phospholipids and n-3 fatty acids; however, storage at vacuum improved the oxidative stability of krill powder. Practical applications: For the use of krill powder in human nutrition, it is important, that the quality and stability is sufficiently high to retain the nutritional value during storage. This study contributes with information about the stability during storage up to 12 months at room temperature and the effect of packaging the powder in vacuum. Antarctic krill ( Euphausia superba) is a shrimp-like marine crustacean. It is rich in omega-3 fatty acids, primarily bound in phospholipids in the sn-2 position of the molecule, making it highly bioavailable. Krill may be processed into powder also rich in protein and astaxanthin. Stability of krill powder, stored for up to 12 months at room temperature, showed slight lipid oxidation. [ABSTRACT FROM AUTHOR]

The quality of krill products is influenced by their manufacturing process and could be evaluated by their degradation products from lipid oxidation and non-enzymatic browning reactions. The main objectives of this study were: (i) to investigate the effect of thermal treatment on these two reactions in krill products during their manufacturing process; and (ii) to understand and postulate the possible mechanisms for non-enzymatic browning reactions in krill products. Characterisation of krill products at different stages was obtained by determination of their lipid composition (lipid classes and phospholipids), antioxidant (α-tocopherol and astaxanthin esters) and volatile profiles (degradation products from lipid oxidation and Strecker degradation). The use of thermal treatment resulted in lipid oxidation and subsequently led to the development of non-enzymatic browning reactions in krill products during their manufacturing process. It is hypothesized that non-enzymatic browning reactions in krill products might occur through Maillard reaction or lipid peroxidation pathways. Practical applications: The quality of krill products is influenced by the temperature used during their manufacturing process, and the occurrence of their degradative reactions is influenced by the chemical composition and matrix of krill products. This work provides information about the possible mechanisms of the two most commonly found reactions in the food system namely, lipid oxidation and non-enzymatic browning reactions. This information is not only applicable to krill products but also to other food matrices containing lipid, protein, sugar, etc. The quality of krill based products is influenced by the thermal treatment used during their manufacturing process and could be evaluated by their degradation products derived from lipid oxidation and non-enzymatic browning reactions. Therefore, the processing temperature needs to be kept as low as possible to prevent the occurrence of these reactions and subsequently preserve the quality of krill products. [ABSTRACT FROM AUTHOR]

The main objective of this study was to further investigate whether the occurrence of Strecker degradation in krill-based products is due to the presence of N-Acetylglucosamine (amino sugar derived from krill exoskeleton) or lipid-derived carbonyls. A simple model system comprising amino acids was incubated at 60°C for 0, 3, 9, and 24 h with five selected lipid-derived carbonyls or five Strecker-derived volatiles or an amino sugar. The presence of both amino sugar and lipid-derived carbonyls (especially α,β-unsaturated aldehydes) caused non-enzymatic browning reactions: (i) pyrrole formation; (ii) browning development; and (iii) Strecker degradation of amino acids, with a faster reaction rate by amino sugar. In addition, the presence of a high level of Strecker degradation products might enhance pyrrole formation. Practical applications: This work provides information about the Strecker degradation of amino acids induced by amino sugar ( N-Acetylglucosamine) and lipid-derived carbonyl compounds, and the increase of pyrrole formation is ascribed to the presence of a high level of Strecker degradation products. The obtained knowledge from this fundamental study explains the occurrence of Strecker degradation in krill products especially after enzymatic treatment due to the increased level of amino acids, lipid oxidation products and amino sugar derived from krill shell. This information is not only applicable to krill matrix but also to similar matrices from other food systems. Non-enzymatic browning reactions, especially Strecker degradation of amino acids in krill-based products during their thermal treatment, are induced either through Maillard reaction due to the presence of amino sugar derived from krill exoskeleton or through the lipid peroxidation pathway due to the presence of unsaturated aldehydes derived from lipid oxidation. [ABSTRACT FROM AUTHOR]