Purpose: To determine the loading, antioxidant activity protection and sustained-release effect of wheat starch on Ligustrum robustum (Rxob.) Blume extract (LRE) for the purpose of providing a theoretical basis for the high value added development and utilization of LRE in the food and biomedical industries. Methods: The major compounds in LRE were identified by mass spectroscopy (MS) and nuclear magnetic resonance (NMR) spectroscopy, and the in vitro antioxidant capacity of LRE was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and reducing power assays. The loading capacity and stability of starch for LRE were measured by cumulative release of total phenols. Besides, the protective effect of starch on the antioxidant activity of LRE was analyzed, and the sustained-release effect of starch on LRE during in vitro simulated digestion was investigated. Results: The major bioactive compounds in LRE were identified as ligurobustoside B (C31H44O13), ligurobustoside N (C35H46O18) and ligupurpuroside J (C35H46O19), and LRE had strong free radical scavenging capacity and reducing power. Furthermore, different concentrations of wheat starch could stably load LRE, delaying the attenuation of the free radical scavenging capacity and reducing power of LRE and inhibiting the release of LRE during in vitro simulated digestion to a certain extent.

In this study, silver carp myofibrillar protein (MP) was oxidized with different concentrations of H2O2 (0.0‒10.0 mmol/L) in the Fenton system (H2O2-VC-FeCl3) to explore the effect of oxidation degree on protein gel formation and gel properties. The sulfhydryl content of MP was measured. The gel strength, whiteness, water-holding capacity, moisture distribution and microstructure of MP gels were determined. The results showed that as H2O2 concentration increased, the total sulfhydryl content, whiteness and water-holding capacity of MP increased first and then decreased. When the H2O2 concentration in the system was low (0.1‒0.5 mmol/L), the gel strength and whiteness were both improved. The area of pores in the three dimensional gel structure became smaller, the distribution became more uniform, and the water-holding capacity of MP gels was enhanced. However, at high H2O2 concentration (5.0‒10.0 mmol/L), the gel whiteness decreased, and the gel structure became disordered, the pore area became larger, the pore distribution became nonuniform, and the water-holding capacity decreased, indicating a deterioration in gel quality. Therefore, appropriate oxidation (0.1‒0.5 mmol/L H2O2) contributed to the improved properties of protein gels. The analysis of the peptide composition by liquid chromatography-tandem mass spectrometry (LC-MS/MS) showed that the major oxidation regions of MP by hydroxyl radicals were the heavy chain of myosin and actin. Moreover, methionine, cysteine, aspartic acid and glutamic acid were recognized as the high-frequency oxidation sites of MP.

Selenized Lonicera caerulea L. polysaccharide was obtained by microwave-assisted HNO3-Na2SeO3 method and purified by column chromatography. The selenium content of the selenized polysaccharide was (0.184 ± 0.03) mg/g with an average molecular mass of 58 828.3 kDa, and the polysaccharide was composed of galacturonic acid, rhamnose, arabinose, mannose, glucose and galactose with a molar ratio of 1:3.06:6.18:0.29:1.78:13.01. Nuclear magnetic resonance analysis showed six glycosidic bonds to be present in the selenized polysaccharide, namely →3)-β-D-galactose-(1→; →4)-β-D-mannose-(1→; →6)-α-D-glucose-(1→; →4)-α-D-galacturonic acid-(1→; →2,4)-α-L-rhamnose-(1→; and α-L-arabinose-(1→. The selenized polysaccharide at a concentration of 10.0 mg/mL reduced the oxidative hemolysis of erythrocytes induced by H2O2 by 32.52%, reactive oxygen species (ROS) level by 44.93%, and malondialdehyde (MDA) content by 17.04 nmol/mL, and decreased the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) by 163.93, 9.95 U/mg and 20.07 mU/mg protein, respectively. Therefore, the selenized polysaccharide from L. caerulea L. fruit can protect erythrocyte against oxidative damage.

In order to reduce the amount of added sodium in myofibrillar protein (MP) gel, the effects of partial substitution of different chloride salts (CaCl2, MgCl2, and KCl) for NaCl on the gel strength, microstructure, water-holding capacity and rheological properties of MP gel were studied. The underlying mechanism of action of sodium substitutes was elucidated by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and intrinsic fluorescence spectroscopy as well as measuring surface hydrophobicity and sulfhydryl content. The results showed that KCl was the best substitute for NaCl, followed by CaCl2, and MgCl2 was least effective in replacing NaCl. The gel strength of the KCl substitution groups (0.5% KCl + 2.5% NaCl, 1.5% KCl + 1.5% NaCl, and 1.0% KCl + 2.0% NaCl; m/m) was better than that of the control group (3% NaCl), while no significant difference in water-holding capacity was found between the two groups (P > 0.05). The gel strength of the 1.5% CaCl2 + 1.5% NaCl group decreased significantly (P < 0.05), and the water-holding capacity decreased first and then increased. The gel strength significantly decreased (P < 0.05) and the water-holding capacity increased in the MgCl2 substitution groups. In terms of rheological properties, the storage modulus (G’) of the KCl substitution groups was significantly higher than that of the control group. Substitution of CaCl2 and MgCl2 increased the surface hydrophobicity of MP and decreased the sulfhydryl content. Substitution of CaCl2, MgCl2, and KCl resulted in a blue shift in intrinsic fluorescence spectra. At low substitution levels (0.5%), the microstructure of MP gel showed no significant difference from that of the control group. The above results indicate that CaCl2, MgCl2 and KCl can be used to partially substitute NaCl in surimi gel products.

In this work, starches were extracted from four species of minor legume widely planted in China: cowpea, lentil, pea, and red kidney bean by wet milling, and their structural characteristics and physicochemical properties were analyzed and compared. The infrared spectra of all the samples presented the typical structural characteristics of starch. The starch granules had complete kidney-like or oval shape with a smooth surface. The average hydrodynamic radii of the four starches were in the following decreasing order of cowpea starch > pea starch > lentils starch > red kidney bean starch. The crystal type of pea starch was CC-type, while the crystal type of cowpea starch, lentils starch and red kidney bean starch was CA-type. The relative crystallinity of these starches was significantly different, ranging between 27.6% and 38.5%. The gelatinization characteristics varied greatly among them, all of which had high gelatinization temperature (75.3-82.8 ℃), being difficult to gelatinize. Cowpea starch was not prone to retrogradation with the lowest amylose content (26.3%), and the thermal stability of cowpea paste was best. Red kidney bean starch had the highest amylose content (31.5%) and retrogradation value, which was most prone to retrogradation. In conclusion, the four legume starches had similar granular morphology and all exhibited a C-type crystal structure, and they were similar in their retrogradation characteristics but distinct in their molecular structure and gelatinization characteristics.

In this study, the stability of Pickering high internal phase emulsions (HIPEs) stabilized by silkworm pupa protein in an in vitro gastrointestinal environment and their astaxanthin loading capacity as well as the bioaccessibility of astaxanthin-loaded HIPEs were characterized, and the mechanism of the targeted and controlled release of astaxanthin-loaded HIPEs in the simulated gastrointestinal environment was elucidated by measuring the particle size distribution and zeta potential as well as using confocal laser scanning microscopy (CLSM), reversed-phase high performance liquid chromatography (RP-HPLC) and electrophoresis. The results showed that silkworm pupa protein stabilize effectively stabilized Pickering HIPEs with an internal phase as 78%, and the encapsulation efficiency of AST in the HIPEs was nearly 88%. The Pickering HIPEs remained stable in the simulated gastric environment for 90 min and became progressively unstable with prolonged digestion in the simulated intestinal environment, significantly increasing the bioaceessibility of astaxanthin. The interfacial protein composition of the emulsion indicated that silkworm pupa protein, with a molecular mass of 70 kDa, was the major protein stabilizing the Pickering HIPEs, and its hydrolysis by the intestinal digestive enzymes was the major cause of the destabilization of the emulsion and the release of astaxanthin. The present study provides a theoretical basis for the application of Pickering HIPEs stabilized by silkworm pupa protein for targeted intestinal delivery of hydrophobic bioactive substances, and opens up new possibilities for the application of astaxanthin in the food and nutraceutical fields.

Food-grade methyl cinnamate as an acyl donor was used to enzymatically acylate cyanidin-3-O-glucoside (C3G) under reduced pressure, which has the advantages of safety, high efficiency and single acylation product. After being purified by semi-preparative high-performance liquid chromatography (SP-HPLC), the acylation product was evaluated for its thermal stability and antioxidant activity. The results showed that the acylation rate was 80%, and the purity of the purified acylated C3G was as high as 98.3%. Mass spectral analysis showed that the acylated product was cyanidin-3-(6-cinnamoyl)-glucoside (C3(6C)G). Acylation modification significantly improved the lipid solubility and thermal stability of C3G. C3G and C3(6C)G had weaker scavenging capacity against 2,2-amino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation but similar 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, ferric reducing and antioxidant power (FRAP) and hydroxyl radical scavenging capacity compared with vitamin C (VC) at the same concentration. At 200 μmol/L, the hydroxyl and DPPH radical scavenging capacity of C3(6C)G was significantly enhanced compared with C3G (P < 0.05), while there was no significant difference in ABTS radical cation scavenging or FRAP between C3G and C3(6C)G (P > 0.05), which showed that cinnamyl modification did not impair the antioxidant capacity of anthocyanins, but instead improved the scavenging capacity against hydroxyl radicals.

The effects of adding different amounts (0.1%–0.5%) of arabic gum (AG) or guar gum (GG), natural polysaccharides with similar molecular mass but different viscosity, on the emulsifying properties of myofibrillar protein (MP) were investigated. The results showed that both AG and GG could significantly improve the emulsifying properties of MP, and AG was more effective in improving the emulsifying activity, while GG was more conducive to the emulsion stability. Both emulsifying activity index (EAI) and emulsion stability index (ESI) initially increased and then decreased with increasing the amount of added polysaccharides, reaching maximum values when 0.3% AG or 0.2% GG was added. Both polysaccharides, especially GG, resulted in a marked reduction of the interfacial protein content. The droplet size of emulsions gradually decreased with increasing the amount of added polysaccharides, and the droplet size distribution became more uniform. When more than 0.3% GG was added, slight flocculation occurred in the emulsions. At the same concentration, GG reduced the droplet size of the emulsions compared to AG. Rheological analysis confirmed that all emulsions were pseudoplastic fluids, exhibiting weak gel properties. AG at low levels (≤ 0.3%) caused a decrease in the viscosity of the emulsions while remarkably increasing the storage modulus. In contrast, the addition of GG significantly increased the apparent viscosity and storage modulus of the emulsions. Compared with AG, the emulsion prepared with GG, with higher viscosity, exhibited greater apparent viscosity and storage modulus, which was more favorable to the emulsion stability.

In this study, we aimed to explore the effect of anaerobic treatment on the contents and functions of bioactive components such as γ-aminobutyric acid (GABA) in yellow tea and to analyze the mechanism by which anaerobic treatment promotes GABA enrichment using metabolomics. We also analyzed the changes in related metabolism pathways. The results showed that the content of GABA in yellow tea was increased to 3.3 mg/g after anaerobic treatment, and the contents of the upstream and downstream amino acids related to GABA were changed correspondingly. Moreover, anaerobic treatment significantly increased the contents of total phenolics and total flavonoids in yellow tea. In vitro bioactivity evaluation showed that anaerobic treatment improved the free radical scavenging capacity, total antioxidant activity and inhibitory effect on the formation of glycosylation products of yellow tea, but had little effect on the ability of yellow tea to inhibit starch digestion enzymes. A total of 218 differential metabolites between fresh and GABA-rich tea, including amino acids, organic acids, flavonoids, nucleotides, and sugars. Pathway enrichment analysis demonstrated that the amino acid biosynthesis, tryptophan metabolism, flavonoid biosynthesis, and butyrate metabolism pathways were significantly regulated. Anaerobic treatment could regulate the GABA content in yellow tea by affecting the L-glutamate and succinic semialdehyde pathways. This study can provide a reference for the research and development of GABA-rich tea.

In this study, the effect of dynamic high pressure microfluidization at different pressures on the structural and functional properties of pea albumin and its complex with chlorogenic acid was investigated by measuring particle size, zeta potential, fluorescence spectra, infrared spectra, hydrophobicity, solubility and emulsification properties. The mechanism of the influence of chlorogenic acid on pea albumin in the binary system was explored. The results showed that after dynamic high pressure microfluidization treatment, the particle size and zeta potential of pea albumin firstly decreased and then increased. The microstructure, secondary structure and tertiary structure of pea albumin were changed. The solubility of small pea albumin particles was significantly increased by 42.37%, reaching 0.84 mg/mL under the action of shear force and other effects (P < 0.05), and the emulsification characteristics were also enhanced. The addition of chlorogenic acid changed the microenvironment of tryptophan residues in pea albumin, which led to significant changes in the structure of pea albumin. Meanwhile, it significantly increased the surface hydrophobicity and decreased the solubility of pea albumin (P < 0.05), and improved the solubility. This study provides an idea for pea albumin modification and a theoretical foundation for the development of high-value protein products.

In order to improve the quality of freshwater fish surimi products, the effect of adding 4% of native cassava starch or modified cassava starch (starch phosphate, hydroxypropyl starch, acetylated distarch phosphate, or a 3:2 (m/m) mixture of acetylated distarch phosphate and hydroxypropyl starch) on improving the quality of surimi gels prepared from frozen tilapia surimi was investigated by measuring texture, rheological properties, water-holding capacity, moisture distribution and microstructure. The results showed that compared with the control group, the whiteness of tilapia surimi gels with native and modified cassava starch significantly decreased (P < 0.05), the gel strength, hardness, chewiness and water-holding capacity significantly increased (P < 0.05), the percentage of cooking loss decreased (P < 0.05), the bound water content increased (P < 0.05), and the microstructure was more uniform and compact. The best gel texture and highest water-holding capacity were achieved with the addition of the modified starch mixture. Low-field magnetic resonance imaging and optical microscopy results showed that both native and modified cassava starch could effectively keep the water in the surimi gel. The native and modified starch could absorb water and expand during the heating process, concentrating and filling the surimi gel network structure, and the surimi gel structure with the modified starch mixture was most compact and uniform. Therefore, addition of acetylated distarch phosphate-hydroxypropyl starch mixture can effectively improve the quality of tilapia surimi products, which will provide theoretical support for the development of freshwater fish surimi products.

In order to reveal the protective mechanism of hydrocolloid on wheat dough gluten during freezing, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to investigate the secondary structure, microstructure, disulfide bond content and water-binding capacity of gluten obtained from frozen-thawed wheat dough added with different amounts of flaxseed gum (FG) or Artemisia sphaerocephala Krasch. gum (ASKG). Results showed that freezing-thawing treatment destroyed the ordered network structure of gluten, while FG and ASKG could cross-link with the gluten protein network structure to form a stable cross-linked structure. Upon the addition of FG or ASKG at 0.4%, the gluten network structure was most uniform and dense. The addition of FG and ASKG increased the content of disulfide bond and the relative content of α-helix in gluten, making the gluten structure more stable under repeated freeze-thaw cycles. In addition, the addition of FG and ASKG reduced the surface hydrophobicity and consequently led to an increase in the water-binding capacity of wheat gluten. The highest water-binding capacity was obtained at an addition level of 0.4% for both FG and ASKG, 1.46 and 1.43 times higher than that of the control group without added hydrocolloid undergoing repeated freeze-thaw cycles, respectively. All these results showed that FG and ASKG could interact with gluten to form a stable cross-linked structure, thereby enhancing the water binding capacity of gluten protein and exerting a cryoprotective effect on it.

In this work, black sesame melanin was used as template and reducing agent to prepare a melanin-nanoselenium complex. The preparation process was optimized, and its structure and morphology were characterized. Also, its antioxidant capacity in vitro was tested, and its protective effect on oxidative damage of red blood cells and EAhy926 endothelial cells was evaluated. Its anticancer activity and biocompatibility were investigated by using lung cancer cell line A549 and shrimp killing experiment. The results showed that the optimum conditions for the synthesis of melanin-nanoselenium complex were as follows: volume ratio of melanin solution (0.3 mg/mL) to selenium dioxide solution (0.555 mg/mL) 9:5, pH 7, and reaction time 5 h with magnetic stirring (400 r/min). The results of X-ray photoelectron spectroscopy (XPS) showed that Se4+ was completely reduced. The results of infrared (IR) spectroscopy indicated that the carboxyl and conjugate structures of melanin might be involved in the reaction. According to the results of characterization by synchronous light scattering, the particle size of the melanin-nanoselenium complex was approximately 200 nm, and it was stable and could be well distributed in water dispersion system. The complex remained stable for 2 h in simulated gastric juice, and was pH tolerant. It could be released slowly in simulated intestinal juice, thus having the potential for long-term sustained release. In vitro antioxidant results showed that the scavenging capacity against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation and total reducing power of the complex were significantly better than those of selenium dioxide. The complex significantly inhibited hemolysis of red blood cells and oxidative damage of EAhy926 endothelial cells induced by hydrogen peroxide, and had inhibitory activity on lung cancer cells. The toxicity of this complex was weaker than that of selenium dioxide, whose semi-lethal concentration (LC50) values were 347.393 and 19.781 µg/mL, respectively. This study is meaningful for guiding further research on melanin resources and the preparation of melanin-nanoselenium complex, and also provides a theoretical basis for the use of melanin-nanoselenium complex as a dietary selenium supplement.

Purpose: To prepare a calcium supplement for efficient absorption and utilization in the human body and to explore its effect on the osteogenic activity of MC3T3-E1 cells. Methods: Bovine bone peptide was chelated with calcium, and the optimal reaction conditions were determined by response surface methodology (RSM). The structural characteristics and stability of peptide-calcium chelate were studied by infrared spectroscopy, X-ray diffraction and atomic absorption spectrometry. The effects of bovine bone peptide-calcium chelate on the proliferation, differentiation and mineralization of MC3T3-E1 cells were investigated. Results: The optimum conditions for the preparation of bovine bone peptide calcium chelate were peptide/calcium mass ratio 2.97, temperature 62.54 ℃ and pH 9.06. Under these conditions, the calcium chelating capacity was 55.65 μg/mg. The results of spectral analysis showed that amino nitrogen, hydroxyl oxygen and carboxyl oxygen were the major calcium-chelating sites. Bovine bone peptide could form coordinate bonds with calcium, and the molecular mass of the peptide increased after chelation with calcium. In addition, the stability of bovine bone peptide-calcium chelate was little affected by temperature, but sensitive to pH. The peptide-calcium chelate could significantly promote the proliferation, differentiation and mineralization of MC3T3-E1 cells. Conclusion: Bovine bone peptide-calcium chelate has the potential to promote the osteogenic activity of MC3T3-E1 cells.

The effects of addition of different amounts (10%, 20%, 25% and 30%) of high amylose corn starch (m/m, based on buckwheat flour) on the structure, cooking quality and digestive characteristics of extruded buckwheat noodles were explored. The results showed that the diameter and gelatinization degree of extruded noodles decreased with increasing addition of high amylose corn starch. The X-ray diffraction results showed that noodles with added high amylose corn starch exhibited the typical B-type peaks of amylose not completely gelatinized in addition to V-type crystallization peaks. Thermodynamic properties also indicated partial gelatinization of amylose. After addition of high amylose corn starch, the color of noodles became lighter and brighter, the optimal cooking time was shortened, and the cooking loss percentage increased from 9.90% to 12.43%. When the addition of high amylose corn starch was 25%, the noodles began to break. The hardness of noodles increased from 2 105.709 to 3 680.401 g, and the elasticity decreased from 0.961 to 0.866. The results of scanning electron microscopy (SEM) showed that with increasing amount of added high amylose corn starch, cracks appeared in the dense structure of noodles gradually, and more starch grains were not completely gelatinized in the cross-section of noodles. In vitro starch digestion experiments showed that with increasing addition of high amylose corn starch, the rate of starch hydrolysis and predicted glycemic index (pGI) decreased, and resistant starch (RS) content increased. The pGI of extruded buckwheat noodles decreased from 74.28 to 66.31 and RS content increased from 34.43% to 47.86% after addition of 30% high amylose corn starch.

To prepare a calcium-binding peptide as calcium supplement, phosvitin phosphopeptide (PPP) was prepared from egg yolk and chelated with calcium ions. Phosvitin (PV) was treated at high temperature and high pressure, and then sequentially hydrolyzed with trypsin and alkaline protease. Based on hydrolysis degree and calcium binding efficiency of peptide, the hydrolysis conditions of alkaline protease were optimized. Phosvitin phosphopeptide-calcium chelate (PPP-Ca) was characterized by ultraviolet (UV) spectroscopy, infrared (IR) spectroscopy, circular dichroism (CD) spectroscopy, scanning electron microscopy (SEM) and zeta potential analysis. The results revealed that the optimal hydrolysis conditions were as follows: enzyme dosage 5%, hydrolysis time 90 min, pH 9.0 and 40 ℃. Under these conditions, the degree of hydrolysis was (25.45 ± 0.17)% and the calcium binding efficiency of peptide was (93.41 ± 1.10)%. The structural characterization showed that Ca bound to PPP mainly through interactions between carboxyl, amino and phosphate groups, and the structure of PPP-Ca was tightly ordered and had aggregation phenomenon.

The present study was conducted in order to investigate the effects of adding different concentrations of glutathione-enriched inactive dry yeast (g-IDY) at different stages of brewing on the quality of pear wine. Wine was prepared from Korla fragrant pears. g-IDY was added at 10, 20 and 30 mg/L before alcoholic fermentation, malolactic fermentation or aging. After aging for two months, the contents of total and individual phenols, antioxidant activity, organic acid contents, aroma components and sensory evaluation of pear wine were analyzed. The results showed that adding g-IDY before alcoholic fermentation or aging significantly increased the content of total phenols and antioxidant capacity and decreased the color index of pear wine (P < 0.05). Besides, adding g-IDY increased the contents of malic acid, lactic acid and citric acid as well as total the content of flavor substances in pear wine. Adding g-IDY before alcohol fermentation or aging was beneficial to the formation of aromatic compounds and contributed to reducing the generation of some undesirable gas, but it led to the generation of more H2S. Together, these findings showed that pear wine prepared with the addition of 20 mg/L of g-IDY before alcoholic fermentation showed the best quality, with total phenol content of 282 mg/L, total flavor substance content of 13 453.22 mg/L and sensory evaluation score of 88.7 out of 100 points.

The amino acid composition of collagens from different animal species was determined and their binding capacities to integrin α2β1 and HT1080 cells were studied by enzyme-linked immunosorbent assay (ELISA) and cell adhesion experiments. Furthermore, the effect of amino acid composition on collagen binding to α2β1 was discussed. The results showed that there were significant differences among the binding capacities of collagens from different animal species to integrin α2β1 and HT1080 cells, and the binding capacity of mammalian collagen was higher than that of fish collagen. The effects of amino acid composition on the binding capacities of collagen to integrin α2β1 and HT1080 cells were similar. The binding capacities were positively correlated with the contents of hydroxyproline, polar uncharged amino acids, imino acids and the degree of hydroxylation of proline, but negatively correlated with the contents of glutamate, glycine, polar charged amino acids and acidic amino acids (P < 0.01). Based on the content of informative amino acids at the high-affinity binding site between collagen and integrin α2β1, a mathematical model between the contents of hydroxyproline and arginine and collagen-integrin α2β1 binding was established by multivariate step-wise regression analysis, which had good predictive accuracy.

In order to uncover the growth and decline of microorganisms during the processing of frozen cooked crayfish and to determine the critical control points, the traditional microbial culture method combined with high-throughput sequencing was used to analyze the changes in the microbial community at different processing stages, namely, raw materials, sand spitting, washing, cooking and finished products. The results showed that the sand spitting process could significantly reduce the number of microbes in the gills by 98.9%, but did not change the number of microbes in the intestine. The total number of colonies in the gills and intestines of crayfish decreased by 4.22 and 4.64 (lg(CFU/g)), respectively during the cooking process. The microbial load in crayfish meat was below the detection limit. Besides, the coliform bacteria and Pseudomonas were killed completely. The high-throughput sequencing results showed that the species abundance and diversity in the gills and intestine of raw crayfish were lower than those in cooked crayfish meat. The microbial community in the crayfish gills was dominated by Proteobacteria, while that in the intestine was dominated by Firmicutes. The species abundance and diversity of crayfish were reduced during sand spitting, and the relative abundance of Proteobacteria in the crayfish intestine was decreased significantly. The relative abundance of Flavobacterium in the meat and gills of crayfish was more significantly decreased after cooking compared with washing. The key control points of microorganisms during the processing of frozen cooked crayfish were determined as sand spitting and cooking, which will provide a theoretical basis for improving the quality and safety of and preserving crayfish products.

In order to improve the utilization of Haliotis discus hannai mantle, collagen purified from it was hydrolyzed by trypsin and pepsin to prepare angiotensin I-converting enzyme (ACE) inhibitory peptides. The hydrolysate was purified by sequential ultrafiltration, SuperdexTM peptide 10/300 GL gel filtration chromatography and high performance liquid chromatography (HPLC). Three ACE inhibitory peptides, SGEVGQ, QRGPAGAQGPQ and GPPGPAGAR, were obtained . Among them, GPPGPAGAR had the highest ACE inhibitory activity with a half maximal inhibitory concentration (IC50) of 177.1 μmol/L. Molecular docking results showed that GPPGPAGAR mainly acted on the S1 active pocket of ACE and the inhibitory mode was similar to that of lisinopril. GPPGPAGAR still showed high ACE inhibitory activity after simulated gastrointestinal digestion. This study will provide a reference for deep processing of abalone mantle and the development of ACE inhibitory peptides.

In order to explore the mechanism for the production of vitamin B12 (VB12) by Lysinibacillus sphaericus C5.1, the whole genome of this stain was sequenced on the PacBio Sequel and Illumina NovaSeq PE150 platforms. Several bioinformatics methods were then used to assemble the sequence data obtained for gene prediction and functional annotation. The results showed that the genome of strain C5.1 consisted of one circular chromosome without plasmids and was 4 690 817 bp in length with an average GC content of 37.21%, and 4 756 protein-encoding genes, 34 rRNAs, and 111 tRNAs were predicted. A total of 3 095, 3 182, 4 374, and 397 genes were respectively matched to the Gene Ontology (GO), Clusters of Orthologous Groups (COG), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Transporter Classification Database (TCDB). Furthermore, we found that the genome of strain C5.1 contained the genes encoding the key enzymes involved in the conversion of uroporphyrinogen III to VB12 . These results could provide an important foundation for studies on the metabolic pathways of L. sphaericus C5.1 during the fermentation of stinky tofu and also provide theoretical support for exploring the mechanism of vitamin B12 biosynthesis in fermented foods.

The changes of yeast count, ethanol, reducing sugar, pH, titratable acidity and total phenols as well as antioxidant properties such as hydroxyl and superoxide anion radical scavenging activities and reducing power during Suaeda salsa fermentation by yeast were studied. The SGompertz, DoseResp, Logistic and Boltzmann models were used to investigate the fermentation kinetics. Meanwhile, a comprehensive evaluation index (CEI) system of S. salsa fermentation was developed by correlation analysis (CA) and principal component analysis (PCA). The growth kinetic model of yeast was established using the DoseResp and Boltzmann equations, the kinetic model of ethanol production was established using the SGompertz equation, and the kinetic model of reducing sugar consumption was established using the Logistic equation. The fitting coefficients (R2) of these models were 0.977, 0.995 and 0.982, respectively, indicating excellent goodness of fit. CA showed that total phenols and organic acid were the major contributors to the antioxidant capacity of fermented S. salsa. PCA showed that the CEI value increased first, then leveled off, and finally decreased. The fermentation endpoint was on the eighth day in overall consideration. The results of this study provide a theoretical basis for the precision preparation of fermented S. salsa.

The changes of microbial diversity and volatile flavor compounds in fermented bamboo shoots with chopped pepper during post-ripening were determined by high-throughput sequencing and headspace solid phase micro-extraction (HS-SPME) couple to gas chromatography-mass spectroscopy (GC-MS), and the correlation between them was analyzed. The results showed that Colletotrichum, Penicillium, Xanthomonas, Erwinia, Ralstonia, Pseudomonas, Pediococcus and Enterobacter were dominated in fermented bamboo shoots with chopped pepper during post-ripening. A total of 71 volatile compounds were detected, and the total content of volatile compounds increased from 406.57 to 900.08 μg/kg over the ripening period. The results of principal component analysis (PCA) showed obvious separation between samples at the early and late ripening stages. Based on variable importance in projection (VIP) greater than 1 from orthogonal partial least squares-discriminant analysis (OPLS-DA), 28 important metabolites were identified. The Pearson correlation coefficient showed that bacteria had a greater impact on flavor compounds than fungi, and the dominant bacteria were positively correlated with most flavor substances. This study will provide a theoretical basis for improving the flavor quality of fermented pepper products during post-ripening.

This study was undertaken in order to explore the effects of mixed culture fermentation with Saccharomyces cerevisiae and Lactobacillus plantarum on the sensory quality, texture characteristics, storage characteristics and flavor quality of wet noodles. Wet noodles were prepared by inoculating dough with S. cerevisiae and/or L. plantarum isolated from old dough. The sensory score of mixed culture fermented noodles was higher than that of single strain fermentation. S. cerevisiae fermentation improved the hardness and elasticity of wet noodles, both single and mixed strain fermentations effectively increased the protein content of noodles, and the protein content of mixed culture fermented noodles was (7.82 ± 0.36)%. After sterilization at 120 ℃, the sensory score and texture quality of noodles fermented with S. cerevisiae alone and in combination with L. plantarum increased, the enthalpy change (ΔH) for aging decreased in the single and mixed strain fermentation groups compared with the control group during storage, and the L* value (brightness) of the L. plantarum and mixed strain fermentation groups was greater than that of the control group. A total of 40, 48, 49 and 53 aroma components were detected in the control, L. plantarum, S. cerevisiae, and mixed strain fermentation groups, respectively. Aldehydes, esters and acids were identified as the major flavor substances of wet noodles. The relative contents of these three substances in the fermentation groups increased significantly, indicating that mixed strain fermentation can promote the production of flavor substances. Furthermore, principal component analysis of the aroma composition data showed a clear separation of the four groups.

Objective: To determine whether the prokaryotic expression product of the red rice OsPrx3 gene, which encodes a peroxiredoxin, can enhance oxidative stress resistance in animals. Methods: OsPrx3 was cloned and expressed in Escherichia coli. After ingestion of the target protein, the animal model Caenorhabditis elega was evaluated for its motility, body length, oxidative stress resistance, reactive oxygen species (ROS) and fat contents, and oxidation-related gene expression levels. Results: This gene was cloned and expressed in E. coli successfully, and the purified expressed protein had high antioxidant activity, which at 1 μg/mL scavenged more than 40% of H2O2 in five minutes. Ingestion of the target protein significantly increased the resistance to oxidative stress within 15 minutes after oxidative treatment and reduced ROS and cellular lipid content in C. elegans compared to the control group, although there were no significant changes in motility or body length. Additionally, the expression levels of several critical antioxidant genes were evidently increased in the treated C. elegans. Conclusion: The OsPrx3 protein had high in vitro antioxidant potency, and when ingested by C. elegans, significantly enhanced the resistance to oxidative stress.

To investigate the effect of lactic acid bacteria (LAB) fermentation on the antioxidant activity of glucosinolates from broccoli florets, the glucosinolate composition and in vitro antioxidant activity of broccoli florets fermented by Lactobacillus plantarum were determined, and the effect of glucosinolates extracted from fermented broccoli florets on oxidative stress resistance and antioxidant indicators in Caenorhabditis elegans was evaluated. Results showed that LAB fermentation improved the in vitro antioxidant activity of broccoli glucosinolates. Glucosinolates from fermented broccoli could increase the survival rate of C. elegans under heat and oxidative stress, significantly reduce the levels of reactive oxygen species (ROS) and lipofuscin (P < 0.05), and increase the activity of superoxide dismutase (SOD), thereby alleviating oxidative damage in C. elegans. To sum up, LAB fermentation can help to improve the antioxidant activity of broccoli glucosinolate, which will provide a theoretical basis for the development of glucosinolates from cruciferous vegetables.

In this study, a myrosinase-producing strain named RJ35 was isolated from a rapeseed field soil, and it was identified by morphological and molecular biological methods. The myrosinase produced by strain RJ35 was purified by sequential ultrafiltration and gel filtration chromatography and its enzymatic properties were studied. Strain RJ35 was assigned to the genus Sphingobacter. The molecular mass of the myrosinase was about 100 kDa. The optimum pH and temperature of the myrosinase were 7.5 and 40 ℃, respectively. Moreover, metal ions had no significant activating effect on the myrosinase. The results of high performance liquid chromatography (HPLC) showed that this enzyme could hydrolyze radish seed extract to produce sulforaphane. Hydrolysis for 30 min under the optimum conditions resulted in a yield of sulforaphane of 5.95 mg/g (radish seed). These research results may lay an experimental foundation for the development of microbial myrosinase.

The physiological inhibitors of soluble epoxide hydrolase (sEH) have significant efficacy in the treatment of hypertension, inflammation, cardiovascular disease and diabetes. In this study, a Hypogen pharmacophore was developed using Atlantic cod peptide and was used to screen for bioactive peptides with tryptophan and sEH inhibitory activity by molecular docking. Bioactive peptide sequences were prepared by solid-phase synthesis, and their in vitro sEH inhibitory activity was determined by high performance liquid chromatography (HPLC). The results showed that the tetrapeptide (PLLW) selected by the optimal pharmacophore model had the best Fit value (9.053) and LibDock score (147.807), and its half-maximal inhibitory concentration (IC50) was 506.66 μmol/L. The molecular docking results showed that PLLW competed with physiological substrates to bind to the active site of sEH through hydrogen bonding and hydrophobic interactions. This study provides a new idea for the screening and mechanistic study of sEH inhibitors in foodborne mixed systems, and also provides a suitable model for the development of sEH inhibitor products.

In this study, gas chromatography (GC) and ultra-high performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS) were used to explore the effects of feeding Schizochytrium spp. on the fatty acid and lipid composition of goat milk, and the differences in fatty acid and lipid composition between goat milk and commercially available pure bovine milk and docosahexaenoic acid (DHA)-enriched bovine milk were analyzed. The results showed that the lipid content was significantly higher in goat milk than in bovine milk (P < 0.05), the major fatty acids in both goat and bovine milk were myristic acid, palmitic acid and oleic acid. The content of DHA in goat milk was significantly increased by feeding Schizochytrium spp.. Triglycerides were the major lipid components in goat and bovine milk, and the phospholipid content in goat milk was significantly higher than that in bovine milk. DHA was mainly present in an glyceride esterified form in dairy milk lipids, and goat milk contained more phospholipid (PL)-bound DHA than bovine milk. Feeding Schizochytrium spp. at 50 g/day provided the highest DHA enrichment in goat milk. In a nutshell, this study demonstrated that dietary DHA supplementation can improve the nutritional value of goat milk, thereby solving the problem of the single source of dietary DHA.

Simultaneous distillation and extraction (SDE) combined with gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile aroma compounds of steamed five grains for the production of Nongxiangxing baijiu: sorghum, wheat, maize, glutinous rice and rice as well as their mixture. A total of 153 compounds were identified from the five grains, of which 108, 93, 93, 66 and 66 were found in sorghum, wheat, maize, glutinous rice and rice, respectively. The identified compounds were dominated by aldehydes, alcohols, ketones, aromatic compounds and esters. Totally 140 compounds were identified in the mixed grain sample by dual-column qualitative analysis. A total of 29 odor active compounds were identified by gas chromatography-olfactory-mass spectrometry (GC-O-MS). The effects of different compounds on the overall flavor of steamed grains were evaluated by using aroma extract dilution analysis (AEDA) and odor activity value (OAV). The OAVs of 17 compounds including benzylthiol, (E,E)-2,4-decadienal, (E)-2-nonenal, nonanal, hexanal, octanal, (E)-2-octenal, (E,E)-2,6-nonadienal, 1-heptanol, (E)-2-decenal, (E,E)-2,4-nonadienal, phenylacetaldehyde, 4-ethyl-2-methoxyphenol, ethyl hexanoate, geranyl acetone, ethyl octanoate and vanillin were larger than 1, which were considered as important compounds contributing to grain flavor. Benzylthiol and (E,E)-2,6-nonadienal were identified as important flavor compounds in steamed grains for the first time.

In order to explore the effect of substituting Chinese baijiu with brandy on the quality of traditional air-dried sausages, sausage samples were formulated with mixtures of mulberry brandy and baijiu in different proportions, and the amount of alcohol added to the sausages was 0.03 mL/g. Air-dried sausages were evaluated for volatile components, biogenic amine content, thiobarbituric acid reactive substances (TBARS) content, total volatile basic nitrogen (TVB-N) content and sensory evaluation after air-drying and ripening. In total 63 volatile components were detected in the samples by headspace-solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) , and 45 known volatile components were detected by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). Benzaldehyde, decyl aldehyde, ethyl acetate, ethyl octanoate, ethyl phenylacetate, ethyl nonanoate and isoamyl acetate were found to be the major typical flavor components in the sausages with brandy. The flavor and overall acceptability of the sausage with complete replacement of baijiu by brandy were best. The TBARS value and TVB-N value were 0.92 mg/kg and 7.15 mg/100 g, respectively, which were significantly lower than those of the control and liquor groups (P < 0.05). In addition, the formation of histamine, tryptamine and 2-phenylethylamine was controlled during the ripening process, and the effect was significantly better than that in the control and liquor groups (P < 0.05). However, the inhibitory effects of baijiu and brandy on the formation of total biogenic amines were not significantly different (P > 0.05). Overall, mulberry brandy imparts a distinct flavor to air-dried sausage, inhibits oxidative deterioration and accumulation of biogenic amines, and improves its quality.

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used for the detection of terpenoids in the raw materials, Daqu, pit mud, fermented grains and base liquor during the brewing process of Nongxiangxing baijiu. Totally 19 terpenoids were detected from the nine raw materials, and their total concentration was 1 338.22 μg/kg. In addition, 18 terpenoids were detected in Daqu at eight time points during fermentation with a total concentration of 2 020.32 μg/kg. A total of 13 terpenoids were detected in pit mud from 10 different cellars with a total concentration of 2 167.89 μg/kg. Eight terpenoids were detected in fermented grains at four time points with a total concentration of 702.68 μg/kg. Nine terpenoids were detected in two groups of base liquor with a total concentration of 338.56 μg/kg. Comparative analysis showed that two of the nine terpenoids came from the raw materials, three came from Daqu, and two were converted from other substances due to high temperatures during the steaming process.

In this study, solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to investigate the volatile compound profiles of eight dairy fat products (including four butters, two creams and two cultured butters) that are popular on the Chinese market. Their key flavor compounds were identified by calculating relative odor activity value (ROAV) as well as using gas chromatography-olfactometry (GC-O). In total 40 volatiles were found in the eight milk fat products, including 7 aldehydes, 6 methyl ketones, 7 fatty acids, and 7 lactones. A total of 17 volatile compounds were identified as key flavor compounds according to their ROAV, and GC-O identified seven of these compounds. Acetic acid, butanoic acid, hexanoic acid, δ-octanolactone, δ-decanolactone and γ-dodecalactone, all of which had ROAV greater than 1 and could be recognized by GC-O, were considered the most significant flavor compounds in dairy fat products.

In order to determine the key odorants in Shaomai (SM) and to investigate the changes of the odorants during SM storage, volatiles were extracted by solvent extraction combined with solvent-assisted flavor evaporation. A total of 50 odor-active compounds were identified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Among these compounds, 1-octen-3-ol, anethole, guaiacol and 2-pentylfuran had the highest flavor dilution (FD) of 6 561 as determined by aroma extract dilution analysis (AEDA). Thirty-seven compounds with FD factors ≥ 81 were quantitated by the internal standard method. Based on the quantitative results and odor thresholds reported in the literature, their odor activity values (OAVs) were calculated. Totally 21 odorants with OAV ≥ 1 were determined as the key odorants of SM. The contents of the 37 compounds in SM stored for up to 13 months at room temperature were analyzed and their OAVs were calculated. The results showed that the number of key odorants in SM did not change during storage. The levels of 5-ethyl-4-hydroxy-2-methyl-3(2H)-furanone, hexanal and 4-vinylguaiacol decreased greatly, while most of the other compounds changed little.

In order to explore the flavor characteristics of different colored millet porridges, the differences in volatile organic compounds in black, green, white and yellow millet porridges were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS). The results showed that a total of 48 volatile organic compounds were identified from all samples, including 22 aldehydes, 11 ketones, 9 alcohols, 2 furans, 2 esters and 2 ethers, accounting for 68.58%–80.66%, 6.52%–9.89%, 5.99%–14.91%, 2.09%–5.66%, 1.13%–1.72% and 0.39%–0.69% of the total amount of volatile organic compounds, respectively. The major volatile organic compounds identified were aldehydes, alcohols and ketones, followed by furans, esters and ethers. The relative contents of aldehydes, ketones and esters in black millet porridge were higher, and the relative content of ketones in green millet porridge was highest. The relative contents of alcohols and furans in white millet porridge were highest. The relative contents of aldehydes and esters in yellow millet porridge were highest. Principal component analysis (PCA) and Euclidean distance analysis showed that the GC-IMS data of volatile organic compounds could be used to distinguish different colored millet porridge samples. A prediction model with good stability was established using orthogonal partial least squares-discriminant analysis (OPLS-DA), and 13 differential volatile organic compounds (variable importance in the projection (VIP) >1) were identified, which could be used for classification of different colored millet porridges. This study provides useful information for enriching the eating quality characteristics of different colored millet.

Gas chromatography-ion mobility spectrometry (GC-IMS) was used to analyze the characteristics and flavor components of 31 jujube samples from three major production areas around the Tarim Basin in Xinjiang autonomous region, Xinzheng in Henan province and Linxian in Shanxi province. GC-IMS flavor fingerprints were constructed to visually identify the differences in the volatile organic jujubes from different geographical origins. The volatile flavor compounds of Huizao and Junzao jujubes from the regions in Xinjiang were significantly different from those of the jujubes from their native habitats. 1-Octene-3-ol (D), 2-methylpropionic acid, 3-octanone (D), butyric acid, and hydroxyacetone contributed the most to the aroma of Huizao jujube. The volatile organic compounds that contributed the most to the aroma of Junzao jujube were propanal, acetone, 3-methyl butyral, octanal (M), and nonanal (M).

The characteristic aroma volatile compounds of black tea were identified, the aroma profile of black tea was dissected, and the perceptual interaction of important characteristic aroma compounds was explored. On this basis, the modified vector model and Steven’s law were applied to this system. Headspace solid-phase microextraction (HS-SPME) and solvent-assisted evaporative extraction (SAFE) combined with gas chromatography-olfactometry (GC-O) were used to evaluate aroma compounds. A total of 51 characteristic aroma compounds were obtained. The major aroma substances identified were alcohols and aldehydes. The results of aroma extract dilution analysis (AEDA) and aroma intensity (OI) record showed that linalool, phenethyl alcohol, (Z)-3-hexenol, geraniol and methyl salicylate significantly contributed to the aroma of black tea. The partial least squares method was used to analyze the correlation between compounds and aroma characteristics, and the electronic nose sensors were matched with the aroma profile using the gray correlation method for comprehensive understanding of the aroma of black tea. Feller’s additive model was used to analyze the perceptual interaction of aroma compounds. Among the 10 groups of binary compounds, eight showed a masking effect, and the remaining two showed a synergistic effect. In conclusion, the above experiments can provide a reference for further study of important flavor substances in black tea.

This research was undertaken to explore the effects of different rolling speeds (35, 45, 55 and 60 r/min) on the flavor quality and internal quality components of Congou black tea from the Jiukeng cultivar. Flavor attributes including taste and color were determined by sensory evaluation, color difference analysis and electronic tongue analysis. Quantitative analysis of tea pigments and theaflavin components were performed by systematic analysis and high-performance liquid chromatography (HPLC). In addition, metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap high resolution-mass spectrometry (UPLC-Q-Orbitrap-MS) was used to determine the non-volatile compounds in Congou black tea. Partial least squares discriminant analysis (PLS-DA) and one-way analysis of variance (ANOVA) were used to investigate the effect of different rolling speeds on the internal quality components of Congou black tea. The results showed that a rolling speed of 45 r/min resulted in the best sensory quality of Congou black tea, especially in taste and aroma, as verified by color difference and electronic tongue analysis. Sixteen significantly differential metabolites were identified among the four tea samples, including procyanidin C1, vitexin, isovitexin, asparagine, aspartic acid, gallic acid, malic acid, succinic acid, and gluconic acid. It was found that rolling speed showed a significant influence on phenolic acids, organic acids and tea pigments (theaflavins, thearubigins, and theabrownins), but had little effect on other metabolites. The contents of thearubigins, carbohydrates and aspartic acid and quality index were highest in Congou black prepared with a rolling speed of 45 r/min, and the contents of organic acids, phenolic acids and theabrownins were lowest, which indicated that this rolling speed was more favorable for the formation of the flavor quality of Congou black tea. This study is expected to provide a theoretical basis and technical guidance for the improvement of Congou black tea quality and the precise production of Congou black tea.

In order to explore the flavor composition profiles of fresh and dried Stropharia rugosoannulata and the key components determining its good flavor, the aroma and flavor components of fresh and dried samples prepared by four different drying methods, namely hot air drying (HAD), vacuum freeze drying (VFD), microwave drying (MWD), natural drying (ND) were analyzed. A total of 118 aroma compounds were detected. After drying, the aroma richness was significantly improved (P < 0.05), and VFD could retain the aroma quality of fresh mushroom to a large extent. Meanwhile, 19 aroma components common to all samples were found to constitute the characteristic component profile of S. rugosoannulata, among which the number and content of aldehydes were dominant, especially for n-hexanal (green aroma). The total amounts of soluble sugar and free amino acids in the HAD sample were significantly higher than those in the fresh sample, and the loss of flavor nucleotides in the VFD sample was least. Therefore, the two drying methods had significant advantages in equivalent umami concentration (EUC) (P < 0.05). The comprehensive sensory score for flavor was in the decreasing order of VFD > HAD > ND > fresh sample > MWD. A partial least squares regression model was established based on the sensory scores and the component data. The R2X, R2Y and Q2 of the first three principal components were 79.4%, 98.9%, and 0.974, respectively. The loading information showed that the interaction between aroma and taste characteristics was obvious. Variable importance in projection scores showed that sweet amino acids, 1-octene-3-ol, butyl-2-octenal and EUC were crucial for the good characteristic flavor of S. rugosoannulata. This study will provide a theoretical basis for subsequent screening of sample pretreatment methods and the development of flavor related products.

In order to accurately evaluate the aroma quality of watermelon grown in dry sandy soil, the volatile aroma components of 9 major watermelon cultivars planted in Jingyuan, Gansu province were identified and analyzed using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The 15 major quality traits of watermelon were comprehensively evaluated by coefficient of variation and grey correlation analysis. Principal component analysis (PCA) was used to identify and analyze the major aroma components in watermelon. The grey correlation analysis showed that Kangle 6, Xisha 1 and Longke 13 ranked top three in terms of comprehensive quality. A total of 77 volatile aroma components were detected in the nine cultivars. Kangle 6 had the largest number (37) of volatile aroma components, of which 10 were unique to Kangle 6. Principal component analysis (PCA) divided the nine cultivars into four groups based on volatile aroma composition. Group I included Longke 13, Laojincheng, Xinjincheng, Laojincheng 5, Jinhua 1, and Longxingjincheng. Group II included Kangle 6. Group III included Xisha 1. Group IV included Linfengjuxing. Furthermore, the major volatile aroma components of each group were identified. There was a significantly positive correlation between the number of volatile aroma components and the grey correlation coefficient of comprehensive quality, suggesting that watermelon cultivars with excellent quality traits usually contain relatively abundant volatile aroma components.

Headspace solid phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O) and an electronic nose were used to investigate the effects of five pretreatment methods including raw fruit, baking, drying, steaming and boiling on the volatile flavor profile of Elaeagnus angustifolia fruit grown in Xinjiang. The results showed that by GC-MS analysis, a total of 69 compounds were detected in the five samples. Based on the results of GC-O combined with odor activity value (OAV), 14 volatile compounds were identified as characteristic aroma components. It was found that (E,E)-2,4-decadienal, nonal, (E,E)-2,4-nonadienal, and β-ionone contributed most to the aroma of E. angustifolia fruit. After different pretreatments, there were significant differences in the aroma intensity for multiple sensory attributes among the samples. The electronic nose could effectively distinguish the aroma intensity of these samples. Partial least squares regression (PLSR) was used to analyze and explain the correlation between characteristic aroma intensity and sensory attributes. Overall, the sensory quality of baked E. angustifolia fruit was relatively better than that of the other samples.

The major bioactive components and flavor characteristics of Toona sinensis buds from different production areas such as Sichuan, Shaanxi, Shandong, Shanxi, Hebei and Yunnan were explored. The overall odor was evaluated by sensory evaluation, and the volatile components were analyzed using electronic nose and gas chromatography-ion mobility spectrometry (GC-IMS) in order to analyze the differences in the flavor characteristics of T. sinensis buds from different production areas. The sensory evaluation results showed that the odor of T. sinensis buds from Yunnan was rich and pleasant, while the odor of T. sinensis buds from Shaanxi was irritating. The results of electronic nose analysis showed that the contents of aromatics and long-chain alkanes in T. sinensis buds from the six production areas were similar, while the contents of nitrogen oxides and sulfides were quite different. A total of 76 volatile substances were identified by GC-IMS, including 12 alcohols, 10 esters, 9 pyrazines, 9 ketones, 8 terpenoids, 7 organic sulfides, 7 aldehydes, 6 acids, 4 phenols and 4 other compounds. The principal component analysis (PCA) of electronic nose and GC-IMS data showed that the flavor of T. sinensis buds from Yunnan was unique, and the flavors of T. sinensis buds from Sichuan, Shaanxi and Shandong were similar. T. sinensis buds from Shanxi was different from those from other geographical origins, and the content of flavor substances in T. sinensis buds from Hebei was low. The results of this study may provide a theoretical basis for the screening of T. sinensis for deep processing.

In order to explore the mechanism of flavor differences, the effect of two cooking methods, namely steaming and microwaving on the lipid composition, the degree of lipid oxidation and hydrolysis, and volatile substances in Penaeus vannamei was studied. The results showed that the contents of total lipids as well as phospholipids, triglycerides, and free fatty acids in P. vannamei were significantly reduced after cooking (P < 0.05). The lipid composition differed between steamed and microwaved shrimp. Microwaved shrimp had higher phospholipid contents but lower free fatty acid contents than the steamed one. The content of saturated fatty acids decreased markedly whereas the content of unsaturated fatty acids increased significantly after cooking (P < 0.05), which may be related to the hydrolysis of phospholipids. Steaming and microwave heating accelerated the oxidation and hydrolysis of lipids, resulting in a significant increase in acid value and thiobarbituric acid reactive substances (TBARS) value (P < 0.05). The results of electronic nose analysis showed that the odor characteristics of fresh, steamed and microwaved shrimp were significantly different, and the odor of fresh shrimp changed more after microwave heating. Twenty-five volatile substances were isolated and identified from shrimp meat using gas chromatography-ion mobility spectrometry (GC-IMS). Among these compounds, 2,3-glutaraldehyde, 2-butanone, 2-methyl butyraldehyde, hexanal, 1-octen-3-one and glutaraldehyde were the major flavor substances in cooked shrimp meat and their contents were higher in the microwaved sample. Pearson correlation analysis showed that oxidative hydrolysis of lipids made an essential contribution to the flavor formation of cooked shrimp and the free fatty acids C14:0, C15:0, C16:1, C18:1n9c, C18:2n6c and C18:3n3 were closely related to the formation of the characteristic odors of shrimp meat.

Based on the highly positive correlation between chilled chicken freshness and the number of Pseudomonas, this study established a loop-mediated isothermal amplification (LAMP) method for rapid detection of Pseudomonas for the purpose of freshness detection. The results showed that the established LAMP system had high specificity for Pseudomonas, and the highest sensitivity was 3.05 × 102 CFU/mL. According to the measured values of Pseudomonas count, total bacterial count, total volatile basic nitrogen (TVB-N) content, pH, sensory properties of chilled chicken during storage, it was found that the total bacterial count and odor properties were the most accurate indicators of freshness, and the correlation between Pseudomonas count and them was the strongest. Pseudomonas count in the early stage of spoilage could be accurately identified by LAMP, and based on it the freshness of chilled chicken could be inferred. The method established in this study is time-saving, flexible, and applicable to a variety of scenarios, and it deserves to be popularized.

In this study, magnetic metal organic framework composites as capture probe and immunofunctionalized gold nanoparticles as signal probe were used to develop a rapid colorimetric method for the detection of Listeria monocytogenes. Under optimal conditions, the visual detection limit for L. monocytogenes was 1.2 × 103 CFU/mL. The results of ultraviolet spectroscopy showed a good linear relationship in the range of 1.2 × 101‒1.2 × 108 CFU/mL (Y = 0.519 ‒ 0.043X, R2 = 0.978), the detection limit was as low as 0.45 CFU/mL, and the intra-batch coefficient of variation of all concentration gradients was between 0.31% and 1.30%. The recoveries for spiked chicken breast were 91.1%‒108.7% with coefficient of variation less than 7.4%, and the result was consistent with that of the plate counting method. In conclusion, the proposed assay is rapid, accurate sensitive, and highly applicable to the detection of foodborne pathogens.