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The effects of different concentrations (0.05%, 0.1%, 0.15%, 0.2%, and 0.25%) of resveratrol (RE) on the structural properties, rheological properties and gel properties (gel strength, water retention, water mobility, whiteness and microstructure) of silver fish myofibrillar protein were investigated. RE was found to combine with myofibrillar protein molecules, resulting in an increase in the particle size. Ultraviolet (UV) absorption spectra and intrinsic fluorescence spectra showed that the addition of RE changed the spatial conformation of myofibrillar protein and reduce its fluorescence intensity. The rheological results showed that the addition of RE increased the storage modulus and loss modulus of myofibrillar protein. As the amount of added RE increased, the gel strength first increased and then decreased. The addition of 0.15% of RE increased it by 38.43% compared with the control group. In addition, the addition of RE also improved the texture properties of the gel and increased the whiteness. Low-field nuclear magnetic resonance (LF-NMR) analysis showed that the addition of RE transformed part of the free water into immobilized water, enhancing the water-binding capacity of the gel. Scanning electron microscopy (SEM) showed that the addition of RE promoted the formation of a denser gel network. These results show that when added at an appropriate level, RE could interact with silver carp myofibrillar protein to change its conformation, thereby enhancing the gel properties of myofibrillar protein and forming a dense gel network structure. The results of this study can provide a reference for improving the gel properties of freshwater fish surimi and the quality of surimi products.

Bioactive peptides from marine sources have a broad spectrum of biological properties, including antioxidant, anti-hypertensive and anti-atherogenic activity. The molecular mass of antioxidant peptides from marine sources is generally less than 3 kDa, and most of them are produced by pepsin hydrolysis. The molecular mass of antihypertensive peptides from marine sources, which have angiotensin converting enzyme inhibitory activity, is generally less than 1.5 kDa. Peptides extracted from chlorella can inhibit the production of endothelial cell selectin and have anti-atherosclerotic activity. Peptides derived from the hydrolysis of green-lipped mussel by neutral protease can promote the proliferation of platelet endothelial cell adhesion molecule 1, fibroblast growth factor and epidermal growth factor, and repair skin wound. Peptides derived from proteins in fish processing byproducts have good foaming and emulsifying properties; the higher the degree of hydrolysis, the better the solubility. This article aims to review the information on bioactive peptides isolated from different marine sources, with focus on different biological activities and functional properties as well as different industrial applications. It is expected to promote the development of functional products from bioactive peptides derived from marine sources and provide a theoretical reference for further studies on their biological and functional characteristics.

Summary: The gel performance of surimi‐based products is indispensable technological attribute responsible for their high popularity. Here, surimi gels with tunable gel properties were successfully fabricated based on the double network theory. Konjac glucomannan (KGM) hydrolysed for various periods (0, 5, 15, 30, 60 and 90 min) was introduced into surimi systems. Corresponding structural characterisations including FTIR, XRD, SDS‐PAGE and grafting degree assessment, were conducted to confirm the presence of double crosslinking reactions. Furthermore, the gel strength, dynamic rheology, thermal stability and in vitro digestibility of the surimi gels were investigated. Red shifts in the amide A band and an increase in relative intensity indicated that hydrogen bonding existed in the complex systems, according to the FTIR spectra. The XRD patterns suggested that the crystalline structures were weakened by interfering with the protein chain arrangement due to the Maillard reaction. In addition, SDS‐PAGE and o‐phthalaldehyde (OPA) assays also confirmed that myofibrillar protein and hydrolysed KGM were partially linked by covalent bonding. The SK‐2 group showed the greatest mechanical strength and lowest digestibility amongst all groups due to its dense hierarchical structure. This work may provide inspiration for the design and development of surimi gels with improved gel properties via microarchitectural modulation. [ABSTRACT FROM AUTHOR]

Abstract Background Mitochondrial DNA sequences are extensively used as genetic markers not only for studies of population or ecological genetics, but also for phylogenetic and evolutionary analyses. Complete mt-sequences can reveal information about gene order and its variation, as well as gene and genome evolution when sequences from multiple phyla are compared. Mitochondrial gene order is highly variable among mollusks, with bivalves exhibiting the most variability. Of the 41 complete mt genomes sequenced so far, 12 are from bivalves. We determined, in the current study, the complete mitochondrial DNA sequence of Crassostrea hongkongensis. We present here an analysis of features of its gene content and genome organization in comparison with two other Crassostrea species to assess the variation within bivalves and among main groups of mollusks. Results The complete mitochondrial genome of C. hongkongensis was determined using long PCR and a primer walking sequencing strategy with genus-specific primers. The genome is 16,475 bp in length and contains 12 protein-coding genes (the atp8 gene is missing, as in most bivalves), 22 transfer tRNA genes (including a suppressor tRNA gene), and 2 ribosomal RNA genes, all of which appear to be transcribed from the same strand. A striking finding of this study is that a DNA segment containing four tRNA genes (trnk1, trnC, trnQ1 and trnN) and two duplicated or split rRNA gene (rrnL5' and rrnS) are absent from the genome, when compared with that of two other extant Crassostrea species, which is very likely a consequence of loss of a single genomic region present in ancestor of C. hongkongensis. It indicates this region seem to be a "hot spot" of genomic rearrangements over the Crassostrea mt-genomes. The arrangement of protein-coding genes in C. hongkongensis is identical to that of Crassostrea gigas and Crassostrea virginica, but higher amino acid sequence identities are shared between C. hongkongensis and C. gigas than between other pairs. There exists significant codon bias, favoring codons ending in A or T and against those ending with C. Pair analysis of genome rearrangements showed that the rearrangement distance is great between C. gigas-C. hongkongensis and C. virginica, indicating a high degree of rearrangements within Crassostrea. The determination of complete mt-genome of C. hongkongensis has yielded useful insight into features of gene order, variation, and evolution of Crassostrea and bivalve mt-genomes. Conclusion The mt-genome of C. hongkongensis shares some similarity with, and interesting differences to, other Crassostrea species and bivalves. The absence of trnC and trnN genes and duplicated or split rRNA genes from the C. hongkongensis genome is a completely novel feature not previously reported in Crassostrea species. The phenomenon is likely due to the loss of a segment that is present in other Crassostrea species and was present in ancestor of C. hongkongensis, thus a case of "tandem duplication-random loss (TDRL)". The mt-genome and new feature presented here reveal and underline the high level variation of gene order and gene content in Crassostrea and bivalves, inspiring more research to gain understanding to mechanisms underlying gene and genome evolution in bivalves and mollusks.