High-intensity ultrasound improved the physicochemical and gelling properties of Litopenaeus vannamei myofibrillar protein.

The effects of high-intensity ultrasound on the physicochemical and gelling properties of Litopenaeus vannamei (L. vannamei) myofibrillar protein (MP) were investigated. MP solutions were subjected to ultrasound treatment (power 100 W, 300 W, and 500 W). It was found that the carbonyl and free amino contents of MP increased significantly with increasing ultrasound power, accompanied by enhanced emulsification properties. The increase of free radical and carbonyl content indicated that ultrasound induced the oxidation of MP. With the increase of ultrasound power, it was found that the total sulfhydryl content of the shrimp MP decreased, but the surface hydrophobicity increased significantly, which might be closely related to the conformational changes of MP. Meanwhile, a significant increase of ß-sheet but a decrease of α-helix in the secondary structure of MP was observed with increasing ultrasound power, indicating that ultrasound treatment induced the stretching and flexibility of MP molecules. SDS-PAGE showed that L. vannamei MP consisted of myosin heavy chain, actin, myosin light chain, paramyosin and tropomyosin. Ultrasound treatment could lead to some degree of oxidative aggregation of MP. The results of rheological properties indicated that ultrasound treatment enhanced the viscoelasticity of MP and further improved the gel strength of MP gel. This study can provide a theoretical basis for the functional modification of shrimp MP and the processing of its surimi products.

Effect of phytic acid combined with lactic acid on color and texture deterioration of ready-to-eat shrimps during storage.

To retard the deterioration of texture and color of ready-to-eat (RTE) shrimps during storage, phytic acid (PA) and lactic acid (LA) were used to soak the shrimp prior to cooking. The factors affecting texture (water holding capacity, protein oxidation and degradation, and microstructure) and color (Maillard reaction and lipid oxidation) were determined separately. The free radical and copper ion content were also determined in order to investigate the regulation mechanism of phytic acid and lactic acid on the texture and color of RTE shrimps. It was found that the inhibitor-treated RTE shrimps showed better texture and color properties than the control group, and the compound inhibitor (PA + LA) showed a better inhibition effect than single inhibitor. In addition, PA and LA prevented the oxidation of RTE shrimps by scavenging free radicals and chelating copper ions, which in turn enabled the regulation of color and texture deterioration.

Nanocomplexes of curcumin and glycated bovine serum albumin: The formation mechanism and effect of glycation on their physicochemical properties.

Bovine serum albumin (BSA) and BSA-glucose conjugates (GBSAⅠ and GBSAⅠI) with different extent of glycation were complexed with curcumin (CUR). The formation mechanism of BSA/GBSA-CUR complexes and the effect of glycation on their physicochemical properties were investigated. Fluorescence quenching and FTIR analysis indicated that the BSA/GBSA-CUR nanocomplexes were formed mainly by hydrophobic interactions. XRD analysis demonstrated that CUR was present in an amorphous state in the nanocomplexes. BSA with a greater extent of glycation (BSA < GBSAⅠ

Inhibition of ultraviolet-induced sea cucumber (Stichopus japonicus) autolysis by maintaining coelomocyte intracellular calcium homeostasis.

Apoptosis plays a critical role in sea cucumber autolysis. To investigate the ultraviolet (UV)-induced apoptosis, sea cucumbers with and without injection of BAPTA-AM (cytosolic calcium chelator) were exposed to UV (15 W/m2) for 30 min. The results showed that UV irradiation caused several changes in sea cucumber coelomocytes, including calcium imbalance, abnormal morphology of endoplasmic reticulum, upregulation of pro-apoptotic proteins CRT, CHOP, and caspases 9 and 3, and downregulation of anti-apoptotic protein Bcl-2. A comparison between the two groups showed that injection of the calcium chelator into sea cucumbers helped maintain coelomocyte intracellular calcium homeostasis and suppressed other abnormal changes caused by ER stress, indicating apoptosis in sea cucumbers is mediated by calcium imbalance and follows the activation of the ER stress pathway. Therefore, this study broadens understanding of the apoptotic mechanism involved in sea cucumber autolysis, which is helpful in developing preservative agents for sea cucumbers.

Effect of hydroxyl radical induced oxidation on the physicochemical and gelling properties of shrimp myofibrillar protein and its mechanism.

Protein oxidation is considered as an important factor affecting the texture quality of surimi. In this work, the myofibrillar protein (MP) from shrimp (Penaeus vannamei) was subjected to a hydroxyl radical generating system at various concentrations of H2O2, to simulate the oxidative environment during surimi processing. After the hydroxyl radical oxidation, it was found that the carbonyl content, surface hydrophobicity, and MP aggregation increased. Meanwhile, the a-helix decreased, but ß-sheet increased after oxidation. The moderate oxidation led to a dense network microstructure, increased water holding capacity (WHC) and decreased water mobility, which ultimately enhanced textural (hardness and springiness increased by 0.51- and 0.06-fold, respectively) and rheological properties of MP gel (MPG). However, excessive oxidation could reduce the mechanical properties of MPG. The microstructure, WHC and water distribution played a key role in the mechanical properties of MPG. This study can provide a theoretical basis for processing of shrimp surimi products.

Effects of natural phenolics on shelf life and lipid stability of freeze-dried scallop adductor muscle.

Effects of natural phenolics on the shelf life of dried scallop adductor muscle predicted by accelerated shelf life testing (ALST) combined with Arrhenius model were investigated. This allows the food industries to reliably and rapidly determine the shelf life of dried shellfish species treated with antioxidants. The shelf life of dried scallop adductor muscle treated with antioxidants of bamboo leaves (AOB) and tea polyphenols (TP) was more than 1.70-fold that of dried control scallop adductor muscle. Thus, the highly nutritional value of dried scallop adductor muscle, based on its lipid constituents, is maintained during storage. OXITEST method further confirmed the improvement of lipid stability of antioxidant treated dried scallop adductor muscle by protecting polyunsaturated fatty acids, especially eicosapentaenoic and docosahexaenoic acids, against autoxidation. Moreover, the natural phenolics employed effectively limited lipid oxidation by breaking the autoxidative chain reaction and/or inhibiting free radical formation in dried scallop adductor muscle during storage.