Structural and functional properties of collagen isolated from lumpfish and starfish using isoelectric precipitation vs salting out.

The possibility of replacing the very time and resource demanding salting out (SO) method with isoelectric precipitation (IP) during collagen extraction from common starfish and lumpfish was investigated. The effect of IP on yield, structural and functional properties of the collagens was therefore compared with SO. Application of IP resulted in a higher or similar collagen mass yield compared with SO from starfish and lumpfish, respectively. However, the purity of collagens recovered with IP was lower than those recovered with SO. Replacing SO with IP did not affect polypeptide pattern and tropohelical structural integrity of collagen from the two resources as revealed with SDS-PAGE and FTIR analysis. Thermal stability and fibril formation capacity of collagens recovered with IP were also well preserved. Overall, the results showed that the IP can be a promising resource smart alternative for the classic SO precipitation during collagen extraction from marine resources.

Resource efficient collagen extraction from common starfish with the aid of high shear mechanical homogenization and ultrasound.

Processes currently used for collagen extraction are complicated requiring a great deal of time and chemicals. Here, high shear mechanical homogenization (HSMH) and ultrasound (US) were integrated in the pretreatment step of collagen extraction from common starfish to reduce chemical use and time consumption. Effects of the assistant technologies on yield, structural integrity and functionality of collagen were also investigated. HSMH reduced the deproteinization time from 6 h to 5 min and its required amount of alkali 4 times, compared with classic methods. HSMH + US reduced the demineralization time from 24 h to 12 h and improved its efficiency in extraction of minerals. Collagen extraction with HSMH and HSMH + US resulted in similar yield as the classic method and did not affect triple helical structural integrity, polypeptide pattern, thermal stability or fibril-formation capacity of the collagens. Altogether, HSMH and US can effectively improve resource efficiency during collagen extraction without imposing negative effect on collagen quality.

Effect of the mixtures of squid ink tyrosinase and tannic acid on properties of sardine surimi gel.

Effect of the mixture of squid ink tyrosinase (SIT) at 300 and 500 U/g protein and tannic acid (TA) at 0.5 and 1 % (based on protein) with different reaction times (90 and 180 min) on gel properties of sardine surimi was investigated. Surimi gel incorporated with mixture of SIT (500 U/g protein) and 1 % TA with a reaction time of 90 min had the highest breaking force and deformation (p < 0.05), in which the increases by 29.3 % and 11.9 % were observed, in comparison with the control. However, gels added with SIT/TA mixture had the lower whiteness, compared to the control (p < 0.05). Gel added with SIT/TA mixture showed more compact and finer network with higher connectivity of strands, compared to the control. This was coincidental with decreased expressible moisture content. Based on sensory evaluation, the highest overall likeness score was found in gel added with the mixture of SIT (500 U/g protein) and 1 % TA (p < 0.05). Therefore the mixture of tyrosinase from squid ink and tannic acid could be used as additives to improve the properties of surimi gel.

Application of melanin-free ink as a new antioxidative gel enhancer in sardine surimi gel.

BACKGROUND: The squid ink that is discarded as waste during processing can be effectively utilised as a gel enhancer in surimi gels, especially those prepared from dark-fleshed fish which have poor gel properties. It also acts as an antioxidant, inhibiting lipid oxidation. This investigation aimed to study the effect of melanin-free ink (MFI) from splendid squid (Loligo formosana) on properties and oxidative stability of surimi gel from sardine (Sardinella albella). RESULTS: MFI (0-0.1 g kg(-1) surimi) increased the breaking force and deformation of sardine surimi gel in a dose-dependent manner (P < 0.05). The addition of MFI had no effect on whiteness of surimi gels (P > 0.05). The expressible moisture content of gels decreased as the levels of MFI increased (P < 0.05). Based on a microstructure study, gel added with MFI at a level of 0.08 g kg(-1) surimi was denser and finer than that of the control (without MFI). Surimi gels with MFI had lower peroxide values, thiobarbituric acid reactive substances, nonanal and 2-decenal. CONCLUSION: MFI could improve the properties of sardine surimi gel. Additionally, it was able to prevent lipid oxidation in surimi gels during refrigerated storage.