Potential mechanism of different gelation properties of white and red muscle fibre from crocodile (Crocodylus siamensis) meat: Study of myofibrillar protein

Ultrasound combined with slightly acidic electrolytic water thawing improved rheological properties, quality and structure of mutton myofibrillar protein gel

This study investigated the influence of ultrasound combined with slightly acidic electrolyzed water thawing (UST) on the rheological characteristics, quality and structure of mutton myofibrillar protein (MP) gel in comparison with other thawing methods (air thawing (AT), water immersion thawing (WT), microwave thawing (MT)). According to the result of rheological properties, the UST group had a higher storage modulus among thawing groups. UST treatment significantly improved the gel water holding capacity and whiteness (P < 0.05). In terms of texture, the MP gel of the UST group had better elasticity and strength than other thawing groups (P < 0.05). The UST treatment has no influence on the water distribution in the MP gel (P > 0.05). The UST treatment protected the secondary structure in the MP gel. Among all thawing groups, the UST group exhibited a smoother and more compact microstructure. In conclusion, the UST method effectively improved the MP rheological properties and gel quality, which could be applied as a promising method for deep processing of meat products.

Exploration of antioxidant peptides from crocodile (Crocodylus siamensis) meat using modern information technology: Virtual-screening and antioxidant mechanisms

To develop a safe, stable and easily absorbed new antioxidant peptide. The myofibrillar protein hydrolysates of Siamese crocodile meat were prepared and purified, their free radical scavenging and Fe2+ chelating ability were determined. The results showed that isolated component 3 of neutral protease hydrolysate (N3) had the highest antioxidant activity. Subsequently, liquid chromatography-mass spectrometry was applied to appraise the amino acid sequences within the N3 component, and 8 novel antioxidant peptides were screened by bioinformatics analysis, the antioxidant test proved that all 8 synthetic peptides had certain antioxidant activity. Among them, there was no significant difference in the DPPH radical scavenging capacity of GWDK, LWDK, ERWP, LGWK and LWAK (P > 0.05), which were higher than that of DFRDY and WYRDD (P < 0.05), the ABTS radical scavenging ability of DFRDY was similar to WYRDD (P > 0.05), but remarkably stronger than that of the other 6 peptides (P < 0.05). Finally, the binding mechanism of 8 novel peptides to Keap1 protein was explored through molecular docking, and it was found that hydrogen bonding and hydrophobic interaction were the primary forces that bind antioxidant peptides to Keap1 protein.

Metabolomic profile of muscles from tilapia cultured in recirculating aquaculture systems and traditional aquaculture in ponds and protein stability during freeze-thaw cycles

Muscle protein stability during freeze-thaw (F-T) cycles was investigated with tilapia cultured in recirculating aquaculture systems (RAS) and traditional aquaculture in ponds (TAP). This study found that fatty acids (eg., palmitic acid) were enriched in TAP, while antioxidants (eg., glutathione) were enriched in RAS. Generally, proteins in the RAS group exhibited greater stability against denaturation during the F-T cycle, suggested by a less decrease in haem protein content (77% in RAS and 86% in TAP) and a less increase in surface hydrophobicity of sarcoplasmic protein (63% in RAS and 101% in TAP). There was no significant difference in oxidative stability of myofibrillar protein between the two groups. This study provides a theoretical guide for the quality control of tilapia cultured in RAS during frozen storage.

Gelation of crocodile myofibrillar protein - κ-carrageenan mixtures in two low-NaCl solution

Crocodile meat is a novel reptile meat source, but its processing method is rare. This study investigated the effect of κ-carrageenan addition and partial substitution of NaCl on the gel properties of crocodile myofibrillar protein (CMP). Result showed that CMP formed gel when temperature above 60 ℃. The water-holding capacity, gel strength, denaturation degree, sulfhydryl content covalent bond and hydrophobic bond of gel in KCl solution were significantly higher than those in CaCl2 solution (P < 0.05). K+ induced CMP to form a tight network structure with uniform small pores though covalent and hydrophobic bonds, but the gel properties were reduced by κ-carrageenan. In CaCl2 solution, κ-carrageenan improved the gel structure by filling the protein network through hydrogen bonding. Therefore, it can be concluded that KCl is better than CaCl2 in the manufacturing of low-sodium crocodile foods. Moreover, κ-carrageenan was only beneficial to gel quality in CaCl2 solution.

Effects of protein and lipid oxidation on the water holding capacity of different parts of bighead carp: Eye, dorsal, belly and tail muscles

The quality of fish can change due to differences in the lipid and protein oxidation rates in different muscles. This study examined vacuum-packed eye muscle (EM), dorsal muscle (DM), belly muscle (BM), and tail muscle (TM) of bighead carp frozen for 180 days. The results reveal that EM had the highest lipid content and the lowest protein content, while DM had the lowest lipid content and the highest protein content. EM also showed the highest values of centrifugal loss and cooking loss, and the correlation analysis showed that these losses were positively correlated with dityrosine content and negatively correlated with conjugated triene content. The content of carbonyl, disulfide bond, and surface hydrophobicity of myofibrillar protein (MP) also increased with time, with DM having the highest values. The microstructure of EM was looser than other muscles. Therefore, DM had the fastest oxidation rate and EM had the lowest water holding capacity.

Ultrasound combined with slightly acidic electrolyzed water thawing of mutton: Effects on physicochemical properties, oxidation and structure of myofibrillar protein

The effects of air thawing (AT), water immersion thawing (WT), microwave thawing (MT) and ultrasound combined with slightly acidic electrolyzed water thawing (UST) on the myofibrillar protein (MP) properties (surface hydrophobicity, solubility, turbidity, particle size and zeta potential), protein oxidation (carbonyl content and sulfhydryl content) and structure (primary, secondary and tertiary) of frozen mutton were investigated in comparison with fresh mutton (FM). The solubility and turbidity results showed that the MP properties were significantly improved in the UST treatment. UST treatment could effectively reduce the MP aggregation and enhance the stability, which was similar to the FM. In addition, UST treatment could effectively inhibit protein oxidation during thawing as well. The primary structure of MP was not damaged by the thawing methods. UST treatment could reduce the damage to MP secondary and tertiary structure during the thawing process compared to other thawing methods. Overall, the UST treatment had a positive influence in maintaining the MP properties by inhibiting protein oxidation and protecting protein structure.

Study on the quality and myofibrillar protein structure of chicken breasts during thawing of ultrasound-assisted slightly acidic electrolyzed water (SAEW)

The effects of air thawing (AT), water thawing (WT), slightly acidic electrolyzed water (ET), ultrasound-assisted water thawing (WUT) and ultrasound-assisted slightly acidic electrolyzed water (EUT) on the quality and myofibrillar protein (MP) structure of chicken breasts were investigated. The results showed that WUT and EUT could significantly improve the thawing rate compared with AT, WT, and ET groups. The EUT group not only had lower thawing loss, but also their immobilized and free water contents were similar to fresh sample according to the low-field nuclear magnetic resonance (LF NMR) results. The EUT treatment had no adverse effect on the primary structure of the protein. The secondary and tertiary structures of MP were more stable in the EUT group according to Raman and fluorescence spectra. The muscle fibers microstructure from EUT group was neater and more compact compared with other thawing methods. Therefore, EUT treatment could be considered as a novel potential thawing method in the food industry.

Effect of Active Coatings Containing Lippa citriodora Kunth. Essential Oil on Bacterial Diversity and Myofibrillar Proteins Degradation in Refrigerated Large Yellow Croaker

The research evaluated the effects of locust bean gum (LBG) and sodium alginate (SA) active coatings containing 0.15, 0.30 or 0.60% lemon verbena (Lippa citriodora Kunth.) essential oil (LVEO) on the bacterial diversity and myofibrillar proteins (MPs) of large yellow croaker during refrigerated storage at 4 °C for 18 days. Variability in the dominant bacterial community in different samples on the 0, 9th and 18th day was observed. Pseudomonas and Shewanella were the two major genera identified during refrigerated storage. At the beginning, the richness of Pseudomonas was about 37.31% and increased for control (CK) samples during refrigerated storage, however, the LVEO-treated samples increased sharply from day 0 to the 9th day and then decreased. LBG-SA coatings containing LVEO treatments significantly delayed MPs oxidation by retarding the formation of free carbonyl compounds and maintaining higher sulfhydryl content, higher Ca²⁺-ATPase activity, better organized secondary (higher contents of α-helix and β-sheet) and tertiary structures during refrigerated storage. The transmission electron microscope (TEM) images showed that the integrity of the sarcomere was damaged; the boundaries of the H-, A-, and I-bands, Z-disk, and M-line were fuzzy in the CK samples at the end of storage. However, the LVEO-treated samples were still regular in appearance with distinct dark A-bands, light I-bands, and Z-disk. In brief, LBG-SA active coatings containing LVEO treatments suggested a feasible method for protecting the MPs of large yellow croaker during refrigerated storage.