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In this study, our purpose was to investigate the effect of mild salting on the flavor of large yellow croaker. The volatile flavor compounds of raw (unsalted) and low-salted large yellow croaker were determined by solid phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) and evaluated by gas chromatography-olfactometry (GC-O) and odor activity values (OAV) analysis. The GC-MS analysis showed that the contents of hexanal, nonanal, heptanal, 1-octene-3-ol, anethole and hexanol in both samples were higher than those of other volatile compounds identified. GC-O and OAV analysis showed that the flavor of raw large yellow croaker was significantly affected by 1-octene-3-ol, octanal, nonanal, hexanal, heptanal, (E,Z)-2,6-nonadienal, trans-2-octenal and anethole (OAV > 1); the flavor of low-salted large yellow croaker was significantly affected by linalool, nonanal, hexanal, octanal, 1-octene-3-ol, anethole, (E,Z)-2,6-nonadienal and heptanal (OAV > 1). The changes in flavor after salting treatment was attributed to a significant increase in the OAV of linalool and anethole, and a significant decrease in the OAV of 1-octene-3-ol, hexanal, nonanal, trans-2-octenal, (E,Z)-2,6-nonadienal, heptanal and octanal. The changes of some flavor components might be related to reactions such as the oxidative degradation of unsaturated fatty acids, the biosynthesis of terpenoids, the isomerization of aromatic alcohols, the oxidation and reduction of aliphatic aldehyde and esterification.

In this study, the change of aroma components in instant Baiyaqilan tea powder during processing was investigated by sensory evaluation, gas chromatography-mass spectrometry (GC-MS) and odor activity value (OAV). The results showed that the over aroma profile and the types of aroma components in instant Baiyaqilan tea powder were similar at different stages of processing, while the aroma intensity and volatile components were significantly different. 3-Ethyl-2,5-dimethylpyrazine, hotrienol, methyl salicylate, safranal, geraniol, indole, β-damascenone, cis-jasmonone, geranyl acetone, trans-nerolidol and methyl jasmonate were found to make key contributions to aroma changes. The extraction process significantly increased the OAV of safranal, geraniol, indole, β-damascenone and cis-jasmonone. Disc separation, reverse osmosis and freeze drying significantly reduced the OAV of geraniol, indole, β-damascenone, cis-jasmonone, methyl jasmonate, trans-nerolidol, 3-ethyl-2,5-dimethylpyrazine and safranal. Moreover, ultrafiltration treatment removed tea polyphenol complexes, promoting the release of aroma volatile compounds combined with polyphenols and thus increasing the OAV of geraniol, indole, β-damascenone, cis-jasmonone and methyl jasmonate. This study clarified the aroma change during the processing of instant Baiyaqilan tea powder and showed that ultrafiltration treatment promoted the release of aromatic volatiles. This study can provide a theoretical basis for improving the processing of instant Baiyaqilan tea powder for improved aroma quality and the processing technology of instant tea.

In order to clarify the effect of the non-catalytic carbohydrate-binding module (CBM) and F5/8 type C domains on the enzymatic properties of AlgL7, an alginate lyase from Microbulbifer sp. ALW1, the full-length enzyme AlgL7 and two truncated enzymes: CD1 (catalytic domain) and CD2 (containing F5/8 type C domain and catalytic domain) were constructed and characterized. The results showed that the truncated enzyme CD2 exhibited higher specific activity, thermostability, Michaelis constant (Km), and maximum reaction velocity (Vmax) compared to the full-length AlgL7, indicating that the CBM domain played an important role in maintaining the substrate affinity of the enzyme, but reduced the catalytic activity, thermostability, and Vmax value the enzyme. Compared to the truncated enzyme CD1, CD2 exhibited higher specific activity, optimal reaction temperature, thermostability, Vmax, and Km, indicating that the F5/8 type C domain contributed to improve the enzymatic activity, optimum reaction temperature, thermostability, and Vmax, but reduced the substrate affinity of the enzyme. Using sodium alginate as the substrate, the specific activity of CD2 was 183.9 U/mg. The optimal reaction temperature and pH were 40 ℃ and 7.0, respectively. The Km and Vmax were 39.80 mg/mL and 2 000 U/mg, respectively. The major enzymatic hydrolysates were disaccharides and trisaccharides. This study promotes the understanding of the structure-activity relationship between the non-catalytic domains and the properties of alginate lyase, and lays a theoretical basis for using the non-catalytic domains to improve the catalytic properties of alginate lysate.

In this study, the total sugar, protein, 3,6-anhydro galactose and sulfate contents, apparent molecular mass and monosaccharide composition of porphyran isolated from Porphyra yezoensis were analyzed. The pro-angiogenic activity and underlying mechanism of porphyran were further investigated using human umbilical vein endothelial cells (HUVECs) as an in vitro angiogenesis model. The effect of porphyran on the cell viability of HUVECs was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell adhesion and migration capacity were evaluated using cell adhesion and wound healing assays. The number of lumens formed by HUVECs was analyzed using in vitro tube formation assay. The expression levels of E-cadherin and N-cadherin in HUVECs were analyzed by Western Blotting, and the pro-angiogenic mechanism of porphyran in HUVECs was explored using specific inhibitors of mitogen-activated protein kinases (MAPKs) and vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitors. The results showed that porphyran contained (77.48 ± 2.62)% total sugar, (3.24 ± 0.58)% protein, and (20.30 ± 1.06)% 3,6-anhydrogalactose as well as (20.78 ± 3.31)% sulfate groups. The apparent molecular mass of porphyran was 39.81 kDa. Porphyran was mainly composed of galactose, 3,6-anhydrogalactose and sulfate groups, suggesting it to be a sulfated galactan. Furthermore, porphyran treatment in the concentration range of 0–200 μg/mL had no significant toxicity no HUVECs, but instead promote cell proliferation, adhesion, migration, and vascular network formation. Further studies demonstrated that porphyran exerted its pro-angiogenic effect primarily by mediating the down-regulation of E-cadherin expression and the up-regulation of N-cadherin expression through the c-Jun N-terminal kinase (JNK) MAPK and VEGF receptor signaling pathways. In conclusion, porphyran has pro-angiogenic potential, which will provide a scientific basis for the development of porphyran as a novel pro-angiogenic factor and the precision nutrition-guided deep processing and high-value utilization of the red seaweed P. yezoensis.

Identity authentication and identification as the main activities in the modern human daily life, in the development of social economy and technological innovation of science and technology, information security and public security and other fields of identity recognition technology put forward higher request, not only to accurately record the relevant data information, and use of advanced technology concept advanced authentication technology is put forward. Knowing the living habits of current social residents, they need to choose appropriate ways to prove their identity, whether they enter the computer system or participate in financial services. For example, passwords, keys, ID cards and other contents are traditional means of identity authentication. As the reliability of traditional identity authentication means is getting lower and lower in today’s social network environment, in order to meet the needs of increasingly innovative network platforms and enhance the security and reliability of identity authentication technology, researchers propose to use biometric identification, among which face recognition is the most common. This recognition method is more direct and effective than palmprint, retina, fingerprint and so on, and occupies an important position in the current biometric research topic. After understanding the application of hidden Markov model (HMM) based on wavelet transform and its improved model in the field of face authentication, this paper analyzes the influence of various observation vector optimization methods on the authentication probability, and proposes a dynamic threshold method combined with the authentication model, in order to obtain a better authentication probability. The final design and implementation of the face information as the core of the identity authentication system. The improved hidden Markov model can effectively represent the correlation between face organs, so it has a positive role in the application of face modeling and authentication technology.