Inulin for surimi gel fortification: Performance and molecular weight-dependent effects.

Inulin is a prebiotic carbohydrate widely used in food industry due to its health benefits and unique rheological properties. For the first time, this study explores the potential of natural inulin as a sustainable food additive to enhance surimi gel characteristics, specifically focusing on understanding its molecular weight effects. The good solubility of inulin facilitates the conversion of α-helix to other secondary conformations which are favorable for protein denaturation and aggregation during gelation. Moreover, the abundant -OH groups at the surface of inulin can boost the chemical forces within surimi proteins to reinforce the gel network. Compared to short-chain inulin, long-chain inulin can alleviate proteolysis, enhance hydrophobic interactions and intertwine with myosin molecules, thereby reinforcing the gel network. A more viscous long-chain inulin solution formed within surimi gels fills the space between aggregated proteins and facilitates the lock of water molecules, improving the water-holding capacity (WHC). Thus, an addition of 12 % long-chain inulin leads to an enhanced hardness of surimi gel from 943 to 1593 and improved WHC from 72 % to 85 %. A new inulin-myosin interaction mechanism model is also proposed to provide useful guidelines for surimi processing and expanding the application of inulin within the food industries.

Collagens for surimi gel fortification: Type-dependent effects and the difference between type I and type II.

Surimi products have unsatisfactory gel properties. Hence, this study evaluates the effect of collagen-adding on surimi gel properties and provides the first observation results regarding collagen type influence. With higher water solubility and more charged amino acids than type II, collagen type I intertwines with surimi myofibrillar proteins better to induce higher exposure of protein functional domains, more sufficient conformational changes of myosin and greater formation of chemical forces among proteins. These enhancements accelerate the gelation rate, leading to a well-stabilized surimi gel. The collagen I-containing surimi gels show more compact structures with uniformly distributed smaller pores than those containing collagen II, thereby providing the final products with higher water holding capacity and better textural profiles. As such, the surimi gel fortification performance of collagen I and the well-elucidated collagen-myofibrillar protein interaction mechanism will guide the further exploitation of collagen as an effective additive in the food industry.

Changes in Biochemical Properties and Activity of Trypsin-like Protease (Litopenaeus vannamei) Treated by Atmospheric Cold Plasma (ACP).

The changes in the functional properties of trypsin from shrimps (Litopenaeus vannamei) after, Atmospheric Cold Plasma (ACP) treatments, have been evaluated in terms of enzyme inactivation, surface hydrophobicity, secondary structure, fluorescence intensity, and particle size distribution. Different exposure voltages of 10, 20, 30, 40, and 50 kV at various treatment times (1, 2, 3, and 4 min) have been employed, in a separate assay. The results showed that trypsin-like protease activity decreased (by about 50%), and the kinetic constants Km value increased, while the kcat value decreased. Surface hydrophobicity and fluorescence intensity revealed a significant increase compared to the control sample. A high degree of protein degradation has been noticed by SDS-PAGE analysis. In addition, circular dichroism indicated that random coil and α-helix contents declined while ß-turn and ß-sheet contents have raised. A sharp drop in the particle size was observed with increasing the treatment voltage from 0 to 40 kV for 4 min, and the corresponding peak reached the minimum of 531.2 nm. Summing up the results, it can be concluded that the ACP technique effectively affects the activity of trypsin-like protease, which in terms enhances the quality of dietary protein.