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Chondroitin sulphate (ChS) from the scapular cartilage of the shortfin mako shark (Isurus oxyrinchus) was purified by two-stage enzymatic hydrolysis and a fractional precipitation process using isopropyl alcohol. Characteristics of the ChS fraction were investigated using cellulose acetate membrane electrophoresis and FT-IR spectra. A maximum hydrolysis rate of 78.26% was achieved with 1.35% (w ⁄ w) Alcalase and 1.20% (w ⁄ w) Flavourzyme. A minimum nitrogen content of 2.89% was obtained with 1.43% (w ⁄ w) Alcalase and 1.33% (w ⁄ w) Flavourzyme, as determined by response surface methodology. The precipitation of ChS from the enzymatic hydrolysates was optimised at 40% (v ⁄ v) isopropyl alcohol, which contained 2% (w ⁄ v) NaCl to lower the nitrogen content. The precipitate was further purified via membrane filtration (molecular-weight cut-off, 3 kDa) to remove salt and low-molecular-weight materials. The ChS purified by enzymatic hydrolysis, isopropyl alcohol precipitation and membrane filtration was identified as ChS C by electrophoresis and FT-IR spectra.

Fish gelatins extracted from shark (Isurus oxyrinchus) cartilage were dried by three different methods: freeze drying, hot-air drying and spray drying; and their functional properties were investigated. Freeze-dried gelatin was found to have the strongest gel strength, while gelatins made at high temperatures formed weaker gels. The 135-kPa gel strength of freeze-dried gelatin was relatively high. While foam formation ability of the freeze-dried gelatin was the highest, its foam stability was the lowest. In addition, spray-dried gelatin had the best emulsion capacities. Dynamic viscoelastic properties of shark cartilage gelatins prepared by these drying methods were closely correlated with their gel strength. Elasticity modulus (G'; Pa) and loss modulus (G''; Pa) of the freeze-dried gelatin had higher values than those prepared by hot-air drying and spray drying; viscoelastic properties of the freeze-dried gelatin were maintained longer than those of other drying methods.

Recently, many manufacturers have been developing or producing imitation crab sticks (ICSs) that are highly similar to real snow crab leg meat (RC). This study evaluated the similarities between commercial ICSs and RC based on the analysis of physicochemical and sensory properties. Normal ICS (NS) and premium ICSs either with real crab leg meat (PS-RC) or without it (PS) were compared with RC. The sensory evaluation results showed that PS and NS had the highest and lowest levels of similarity to RC, respectively. The carbohydrate contents of ICSs (10–23%) were higher than that of RC (0.5%). Among ICSs, PS showed more similarity with RC than NS and PS-RC in terms of gel strength and texture profiles. PS-RC and PS showed a microstructural pattern that slightly imitated the muscle fiber arrangement of RC. The electric tongue analysis of taste compounds, such as sugars, free amino acids, and nucleotides, showed that the taste profile of ICSs is distinctly different from that of RC. The electronic nose analysis identified 32 volatile compounds, while the principal component analysis using electronic nose data successfully distinguished three clusters: PS-RC and PS, RC, and NS. Our results could provide useful information for the development of ICSs with higher similarity to RC.

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