Three kinds of silicon dioxide including S655, R92 and R40F were characterized, and their application in low-temperature adsorption refining of fragrant rapeseed oil was studied. The results showed that all three kinds of silicon dioxide had a loose porous structure, but the particle size distribution, specific surface area, pore volume and pore size were obviously different. After being treated with 1.0% silicon dioxide at 45 ℃ for 30 min, the dephosphorization rates of rapeseed oil by S655, R92 and R40F were 90.3%, 99.6% and 88.5%, the lightness increased by 49.9%, 52.5% and 53.9%, the redness decreased by 31.5%, 23.4% and 37.8%, the yellowness increased by 17.3%, 20.0% and 20.6%, respectively. Meanwhile, the retention rate of sterols (above 97.1%) was high, and there were no significant differences in deacidification rate, fatty acid composition or tocopherol retention rate among the three treatment groups. The highest retention rates of total phenol and canolol (98.1% and 99.4%) were found in the samples treated with R92. The contents of glucosinolate degradation products, pyrazines, aldehydes and ketones in fragrant rapeseed oil all increased significantly after refining with the three kinds of silicon dioxide.

Objective: To investigate the effect of calcium, magnesium and potassium salts on the properties of coix seed starch-myofibrillar protein (CSS-MP) composite gel with low sodium content. Methods: Based on the results of previous research, the effects of partial substitution of NaCl by CaCl2, MgCl2 or KCl on the gel strength, water holding capacity (WHC), rheological properties, surface hydrophobicity, sulfhydryl group content, gel microstructure and sensory evaluation of CSS-MP composite gel were investigated. Results: The texture and rheological properties of the CaCl2 substitution group were better than those of the control group (3% NaCl), and the WHC and whiteness of the KCl substitution group were not significantly different from those of the control group, but the gel strength was decreased by MgCl2 or KCl substitution. The total sulfhydryl content of the CaCl2 and MgCl2 replacement groups was significantly lower than that of the control group, and the surface hydrophobicity of the CaCl2 replacement group was significantly higher than that of the other three groups. The addition of MgCl2 promoted the formation of hydrogen bonds, enhanced the hydrophobic interaction, while CaCl2 substitution had the opposite effect. In terms of sensory properties, the substitution of 1.0% CaCl2 and 0.5% MgCl2 could attain a saltiness perception similar to 3% NaCl. However, the comprehensive sensory score showed that the substitution of the three chlorine salts caused no significant difference in sensory properties of CSS-MP composite gel. Conclusion: Calcium, magnesium and potassium salts can improve the properties of CSS-MP composite gel in different degrees. The results of this study lay a theoretical foundation for the development of low-sodium composite surimi gel products.

In this study, xylose and arabinose were subjected separately to Maillard reaction with a crude extract of Mactra veneriformis under dry-heating conditions. The immunoreactivity and digestion properties of the Maillard reaction products (MRPs) were analyzed, finding that the Maillard reaction could reduce the immunoreactivity of allergens derived from Mactra veneriformis, increase the continuous digestion rate of the crude extract in simulated gastrointestinal fluid, and reduce the particle diameter of the digestion products. After that, TM in the MRPs was separated and purified, and its structural characteristics and immunoreactivity were analyzed. The results showed that the α-helix content of TM decreased and the β-sheet, β-turn, and random coil contents increased after the Maillard reaction, the surface hydrophobicity increased, and the spatial structure changed, which eventually led to a reduction in the immunoreactivity of TM. This study provides a theoretical basis for the development of hypoallergenic clam products.

In this work, the regulation mechanism of processed cheese stretchability was studied by adjusting the amount of added emulsifying salt (0.6%–3.0%) and potato acetate starch (0.125%–2%) and pH (5.4–5.8). The results showed that as the emulsifying salt increased from 0.6% to 3.0%, the content of bound calcium in processed cheese decreased from (4.42 ± 0.05) to (0.02 ± 0.04) g/kg, the average fat globule size D(4,3) decreased from (73.08 ± 3.16) to (27.90 ± 2.55) μm, and the bound water content increased from (9.57 ± 0.25)% to (10.40 ± 0.25)%, indicating that the calcium crosslinking effect gradually decreased, the emulsifying effect and hydration degree increased, the interaction between protein molecules changed from strong to weak, so the stretchability of processed cheese initially increased and then decreased. As pH increased from 5.4 to 5.8, the content of bound calcium increased from (2.01 ± 0.08) to (2.74 ± 0.05) g/kg, and the average fat globule size D(4,3) decreased from (36.36 ± 2.68) to (21.37 ± 2.39) μm. Fourier transform infrared spectroscopy showed that the bending vibration absorption peaks of O–H and N–H moved to lower wavenumbers, and the bound water content increased from (9.85 ± 0.16)% to (10.74 ± 0.12)%, indicating that the calcium crosslinking effect, emulsifying effect and hydration degree increased, the interaction between protein molecules changed from strong to weak, so the stretchability of processed cheese increased first and then decreased. As potato acetate starch concentration increased from 0.125% to 2%, the average fat globule size D(4,3) decreased from (54.17 ± 2.74) to (29.92 ± 2.71) μm, and the bound water content increased from (9.90 ± 0.38)% to (11.00 ± 0.21)%, indicating that the emulsifying effect and hydration degree increased, and the stretchability increased first and then decreased. At a potato acetate starch concentration of 2%, starch and protein were separated, so the stretchability became worse. In conclusion, the stretchability of processed cheese is comprehensively regulated by the degree of calcium ion chelation, emulsifying effect, electrostatic interaction between protein molecules, water distribution state and protein-polysaccharide phase behavior.

To investigate the effect of dietary fiber on batter characteristics and oil penetration in deep-fried battered and breaded fish nuggets (BBFNs) from silver carp surimi, deep-fried BBFNs were prepared with model batters (composed of wheat starch and gluten) added with 8% apple fiber, 6% soybean fiber or 12% wheat bran fiber. The moisture adsorption isotherms of dietary fiber, wheat starch and gluten, and the pick-up of BBFNs were evaluated, the viscosity, rheological behavior and calorimetric properties of batters were measured, and the thermogravimetric properties of the crust, the water state and oil penetration of deep-fried BBFNs were also evaluated. The results showed that the moisture absorption capacity of wheat starch was the largest, followed by soybean fiber, apple fiber, wheat bran fiber, and gluten. Compared to that the control group (without dietary fiber), the addition of 8% apple fiber, 6% soybean fiber or 12% wheat bran fiber significantly increased the viscosity of batters and the pick-up of BBFNs (P < 0.05). The loss modulus (G’) and storage modulus (G”) of batters were decreased firstly, then increased rapidly and ultimately remained stable with an increase in oil temperature, and soybean fiber resulted in the highest G’ and G”, which contributed to the fastest formation of gels and the highest thermal stability of the crust after frying. The addition of each of the dietary fibers resulted in transformation of free water into bound water and increased the total moisture content of the crust. Soybean fiber resulted in the lowest oil penetration in deep-fried BBFNs, followed by apple fiber, wheat bran fiber and the control group. This study indicated that the addition of the three dietary fibers in model batter systems can accelerate the formation of gels, significantly improve the strength of the gels formed, and ultimately inhibit oil penetration in deep-fried BBFNs.

Herein, curcumin (Cur) was encapsulated into poly(lactic-co-glycolic acid) (PLGA) nanoparticles to improve the water solubility of Cur, and the formulation was optimized by single factor experiments. The surface of PLGA nanoparticles was modified by human transferrin (Tf) to improve the absorption efficiency of active substances by intestinal cells. Our findings indicated that the optimal preparation method for Cur-PLGA-NP was solvent volatilization and mixing the oil phase with the aqueous phase at a volume ratio of 1:2.5, the optimal loading ratio was 1:15, and the optimal mass concentration of emulsifier F68 was 0.3%. The uptake of Tf-modified PLGA nanoparticles (Tf-NP) by human colon cancer cell line HT-29 cells was significantly higher than that of the control, indicating that both the loading efficiency of Cur and its absorption by intestinal cells were significantly improved by using Tf-NP as a delivery vehicle for Cur. In summary, the absorption efficiency of Cur can be improved by modifying Cur-loaded PLGA nanoparticles with Tf, which provides a reference for the design of delivery systems for active substances with poor water solubility.

In this work, oil-in-water (O/W) emulsion gels with 70% oil phase were prepared using micellar casein (MC) and sodium alginate (SA) as substrates with the addition of gluconate-δ-lactone (GDL) as acidifying agent. The effects of GDL addition on the microstructure, stability and rheological properties of emulsion gels were studied, and the release characteristics of emulsion gels loaded with proanthocyanidins (PC) were analyzed. The results showed that with increasing GDL concentration, the average size of oil droplets in emulsion gels decreased, and it gradually decreased during the storage period. GDL acidification improved the apparent viscosity and storage modulus of emulsion gels, and this effect increased with GDL concentration. The microstructure of emulsion gels did not change significantly after heat treatment at 65 or 80 ℃ for 30 min. Meanwhile, the emulsion gels were stable to acidic and basic conditions as well as storage. In addition, the release rate of PC-loaded emulsion gels was higher than that of free PC during simulated intestinal digestion, and the cumulative release rate at 10 h increased with GDL concentration. The results of this study could provide a reference for the preparation of emulsion gels based on MC and the improvement of PC stability.

In order to study the feasibility of applying cassava starch-fatty acid complexes as a Pickering emulsion stabilizer, complex nanoparticles with complexing index (CPI) of 2.74%, 9.17% and 27.66% were prepared by mixing cassava starch paste containing 78.65% amylopectin at 95 ℃ and stearic acid followed by alcohol precipitation. The three complexes had an irregular spherical-like shape under field emission scanning electron microscopy (FESEM), and their average particle sizes, determined by a laser particle size analyzer, were 315.35, 348.19 and 427.60 nm, respectively. The X-ray diffraction pattern of each of the complexes showed two peaks at 13° and 21°, which were characteristics of the V type crystal structure, and the crystal content increase with increasing CPI. Their deconvoluted infrared spectra exhibited changes in short-range ordering at 1 047, 1 022 and 995 cm-1. The contact angle of the particles with the highest CPI was 60.30°. The three complex nanoparticles stabilized Pickering emulsions for more than seven days compared to less than two days with starch nanoparticles. The complex nanoparticles with CPI of 27.66% stabilized emulsions best. The addition of the complex nanoparticles with CPI of 27.66% at levels above 0.1 g/100 mL resulted in the formation of an emulsion with an oil-to-water ratio of 1:9 (V/V). The emulsion with this nanoparticle at 7 g/100 mL exhibited an improved stability for 60 days without creaming or phase separation. Moreover, no significant changes in the droplet size distribution were observed. The emulsion was stable at pH 5.6-9.0 and not affected by NaCl concentration in the range of 0.01-0.1 mol/L. The emulsion maintained its morphology well after being heated to 80 ℃. These results suggest that the complex nanoparticles are a potential Pickering emulsion stabilizer.

The effects of adding different amounts (0.1%, 0.2%, 0.3%, 0.4% and 0.5%) of psyllium husk powder (PHP), gellan gum (GG) or konjac glucomannan (KGM) on the properties of phosphorylated surimi-crab meat mixed gels (MG) were investigated. The gel properties were improved by adding a small amount (0.1%) of PHP or GG. With increasing addition level of hydrophilic colloids, phase separation occurred, so that the gel properties did not significantly change and even began to decrease. However, the addition of KGM had no significant effect on the breaking force or gel strength, and no phase separation was observed under laser scanning confocal microscopy (LSCM). The addition of PHP and GG increased the temperature at which G’ began to decrease, which was beneficial to the improvement of gel properties. The denaturation of myosin required higher temperature and less energy in the phosphorylated MG system with hydrophilic colloids, and temperature may become a major influential factor in the denaturation process. The overall structural stability of proteins in MG was enhanced by adding a small amount of PHP or KGM. However, PHP and GG had a destructive effect on actin. On the contrary, the addition of a small amount of KGM could increase the structural stability of actin, which may be unfavorable for the formation of gels. The interaction between myosin and actin in the MG system was conducive to enhancing the overall structural stability of proteins. The three hydrophilic colloids, especially GG, at an addition level of 0.1% was beneficial to the improvement of gel properties. The incorporation of hydrophilic colloids may be a novel strategy to improve the quality of phosphorylated MG.

In this study, a composite hydrogel system was constructed by cross-linking of primary network hydrogels of gelatin (GE) and sodium hexametaphosphate (SHMP) by transglutaminase (TGase) after addition of Lactobacillus plantarum in order to improve its viability and bioavailability. The experimental results showed that the modification by SHMP and TGase changed the gel strength, water distribution state, and gel network structure of gelatin, and reduced the gelation rate, so that the three-dimensional network structure of the gel was more stable, and the intermolecular forces of the composite hydrogel was stronger, contributing to the resistance of the encapsulated L. plantarum to adverse environments. The presence of L. plantarum was found to slightly disrupt the ordered structure of the hydrogel by scanning electron microscopy (SEM). Endogenous fluorescence spectroscopy analysis showed that addition of L. plantarum resulted in the exposure of the extended region containing tryptophan within the GE molecule to a more polar environment. The steric effect occurred during the gelling process, delaying the formation of covalent crosslinks and physical interactions between the biopolymer molecules, which led to changes in their microstructure. Simulated gastrointestinal digestion tests and storage tests showed that L. plantarum encapsulated in GE/SHMP/TGase gels had better survival rates and gastrointestinal release properties compared to single GE-based hydrogels. It was confirmed that GE/SHMP/TGase hydrogels had a better protective effect on L. plantarum. In conclusion, this study has explored a new method for preparing GE-based hydrogels as a delivery system for probiotics, which will provide a theoretical basis for the development of probiotic functional foods.

In order to systematically investigate the quality differences between salted and alkaline noodles and the underlying mechanism, the effect of NaCl and K2CO3 on the quality formation of noodles was studied by evaluating the farinograph and extensograph properties and viscosity properties of wheat flour, as well as the cooking properties, texture properties, and storage stability of noodles. Additionally, the microstructure, protein aggregation and volatile components were investigated to explore the underlying mechanisms of the quality differences. The results showed that salt improved the extensibility of dough and noodles, endowed noodles with higher smoothness and elasticity, and showed little effect on starch viscosity, while alkali enhanced the tensile resistance of dough and the hardness and breaking force of cooked noodles, and increased the gelatinization viscosity of starch. The cooking loss of noodles increased with the addition of salt and alkali. Both salt and alkali significantly inhibited the increase of total plate count (TPC) in fresh noodles and consequently enhanced the storage stability, but 0.5% K2CO3 accelerated the browning rate. The scanning electron microscopy (SEM) results showed that NaCl induced a smooth surface microstructure, while K2CO3 resulted in a rough surface of noodles; K2CO3 significantly increased the rate and extent of thermal polymerization of proteins in noodles. NaCl increased the type and concentration of volatile components in noodles, thereby making the aroma of noodles more intense, but the flavor was similar to that of the control. K2CO3 significantly changed the flavor of noodles and resulted in the generation of unique aldehyde compounds.

In order to inhibit the formation of advanced glycation end products (AGEs) and heterocyclic aromatic amines (HAAs) in roasted peanuts, six phenolic acids (caffeic acid, ferulic acid, 4-coumaric acid, vanillic acid, gallic acid and chlorogenic acid) were employed to impregnate raw peanuts before roasting, and the effects of the type and concentration of impregnation solutions on AGEs and HAAs formation during peanut roasting were studied in this work. The results showed that gallic acid and chlorogenic acid could significantly inhibit the formation of Nε-(carboxymethyl) lysine (CML) and Nε-(carboxyethyl) lysine (CEL) with an inhibition rate in the range of 14.7%–24.4% and 13.0%–22.7%, respectively. However, the other four phenolic acids had no inhibitory effect (P > 0.05). What’s more, the inhibitory effects of gallic acid and chlorogenic acid were concentration dependent. Three HAAs including 2-amino-1,6-dimethylimidazo[4,5-b]pyridine (DMIP), 1-methyl-9H-pyrido[3,4-b]indole (Harman) and 9H-pyrido[3,4-b]indole (Norharman) were detected in roasted peanuts. All six phenolic acids could inhibit the formation of DMIP significantly (P < 0.05). Caffeic acid, ferulic acid, chlorogenic acid and gallic acid could inhibit the formation of Harman and Norharman significantly (P < 0.05), while the other two phenolic acids showed no inhibitory effect (P > 0.05). Ferulic acid and chlorogenic acid had a strong inhibition effect on the formation of 3 HAAs, but there was no obvious concentration dependence.

Angiotension converting enzyme (ACE) inhibitory peptides from high-temperature sesame meal protein hydrolyzed by subcritical water were separated and purified by sequential nanofiltration, ultrafiltration and liquid chromatography, and their structures were identified by liquid chromatography-mass spectrometry (LC-MS). The ACE inhibitory activity was verified using the synthetic oligopeptides. The absorption and metabolism characteristics of the oligopeptides were predicted, a three-dimensional quantitative structure-activity relationship (3D-QSAR) model was established, and molecular docking analysis was carried out. The peptide fraction with molecular mass less than 3 kDa had the strongest ACE inhibitory effect. After further purification, nine ACE inhibitory peptides were identified from peak 1. These peptides could not interfere with the normal physiological activities of the human body. The 3D-QSAR model for LFRAF was successfully established using the comparative molecular force field analysis (CoMFA) method. The positively charged amino acid residues and the introduced large groups on the side chain at the C-terminus of the ACE inhibitory peptides could improve their activity. LFRAF occupied the S2 and S1’ active pockets of the ACE peptides and bund to Zn2+ to inhibit ACE activity. These results indicate that it is feasible to use subcritical water technology to degrade high-temperature sesame meal proteins to prepare ACE inhibitory peptides.

Sarcoplasmic proteins (SP) derived from yak meat were oxidized by malondialdehyde (MDA) at different concentrations. The effects of lipid oxidation on physicochemical properties and color stability of SP were investigated by evaluating side-chain amino acid oxidation, protein structure and color of SP and the oxidation status of myoglobin (Mb). The results showed that after MDA oxidation, the a* value, b* value, C* value, and deoxymyoglobin and oxymyoglobin contents of SP significantly decreased (P < 0.05), and the L* value, metmyoglobin content, and ferrylmyoglobin concentration significantly increased (P < 0.05), indicating that MDA oxidation lowered color stability. The contents of carbonyl groups and dimeric tyrosine, the fluorescence intensity of SP-MDA adducts, and the relative contents of β-helix and β-turn significantly increased (P < 0.05), and total sulfhydryl content, surface hydrophobicity, intrinsic fluorescence intensity, and the relative contents of α-helix and random coil significantly declined (P < 0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed blurred expansion of small molecule bands and the formation of macromolecular aggregates, suggesting that MDA promoted the oxidation and aggregation of SP. Pearson correlation analysis revealed significant correlations between MDA oxidation and physicochemical properties and color stability of SP (P < 0.05). This study reveals that MDA alters the structure of SP by directly oxidizing it or mediating Mb oxidation, causing cross-linked aggregation of SP and reducing its color stability.

Using pea protein isolate (PPI) and pullulan (PUL) as raw materials and allicin (AC) as an antibacterial substance, nanofiber materials were prepared by electrospinning technology. The influence of allicin concentration on the structural and morphological characteristics, diameter distribution and antibacterial effects of nanofibers were investigated. Fourier transform infrared spectroscopy (FTIR) indicated that allicin was wrapped in the composite nanofibers. Scanning electron microscopy (SEM) showed that spherical structures of different sizes appeared around the nanofibers due to the addition of allicin. The size of the spherical structures increased (P < 0.05) with an increase in allicin concentration, while the nanofiber diameter gradually decreased (P < 0.05). With increasing allicin concentration up to 15%, the elastic modulus and tensile strength of the composite nanofibers gradually increased (P < 0.05), and the elongation at break gradually decreased (P < 0.05). Additionally, the composite nanofibers with more than 10% allicin exhibited an obvious bacteriostatic effect, and it was strongest at allicin concentrations of 15% and 20%, with inhibition zone diameters of 16.5 and 12.8 mm against E. coli and S. aureus, respectively. This research will provide data support and a theoretical basis for the development and application of new green food packaging nanomaterials.

The purpose of this study was to investigate the effects of sodium starch octenyl succinate (SSOS) as emulsifier and soy protein isolate (SPI) as co-emulsifier on the oxidative stability of nanoemulsion. The ultrasonic emulsification method was used to prepare flaxseed oil nanoemulsion. The results showed that the optimum preparation conditions were as follows: ultrasonic power of 600 W, core-to-wall ratio of 1:1.5, pulse mode of 8 s, and ultrasonication time of 20 min. The nanoemulsion obtained under these conditions was characterized by high embedding rate ((75.1 ± 4.9)% to (74.6 ± 4.2)%), low particle size ((244.0 ± 3.0) to (246.8 ± 4.5) nm) and high absolute zeta-potential value ((−67.2 ± 3.0) to (−69.3 ± 4.0) mV). With the addition of SPI, the peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) value of the nanoemulsion were significantly reduced, and the oxidative stability was remarkably improved. This could result from the fact that SPI could increase the hydrophobicity of the mixed emulsifier, preventing flaxseed oil from contacting with oxygen radicals in the aqueous phase. This study will provide a new idea for improving the water solubility and oxidative stability of flaxseed oil, and provide a theoretical basis for extending the shelf life of flaxseed oil and promoting its application in the food field.

In order to improve the mechanical properties, water resistance and barrier properties of rice bran protein (RBP) film, glycosylated RBP (RBP-G) film and RBP-G-chitosan composite (RBP-G-CS) film were prepared. The effects of the mass ratio of glucose to RBP and the mass ratio of RBP-G to chitosan on the mechanical properties of the films were investigated. The color, transparency, water resistance, water vapor permeability and thermal characteristics of RBP, RBP-G and RBP-G-CS films prepared under the optimal conditions were compared and analyzed. The structure of the films was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the mechanical properties of RBP-G film with a glucose to RBP ratio of 1:1 were obviously improved, and the tensile strength increased by 28.00% and the elongation at break by 33.13% compared with RBP film. RBP-G-CS film with a RBP-G to chitosan ratio of 1:1 had better mechanical properties, and its tensile strength and elongation at break increased by 197.33% and 84.42% compared with RBP film, respectively. The transparency, water resistance, barrier properties and thermal properties of RBP-G-CS film were significantly improved (P < 0.05). The structure of RBP-G-CS film was uniform and compact, owing to the strong hydrogen bonding forces. These results show that glycosylation modification can improve the performance of RBP film, and a good combination of modified RBP and chitosan can greatly improve the mechanical properties and water resistance of the film.

The water adsorption process by dough films at 20 and 40 ℃ was measured using a dynamic vapor sorption system under nine relative humidity (RH) levels. Water diffusivity was expressed as a function of water content and temperature according to the Vrentas & Duda free volume theory. The parameters of the free volume model were obtained by inversion of water content as a function of time. The results showed that the water diffusion coefficient determined based on the free volume theory could well simulate the water adsorption process by dough films at most water contents tested, but the predicted values were significantly lower than the actual ones at low water contents. Therefore, the Vrentas & Duda was improved by adding a free volume term as a function of water content. As the water content increased, the water diffusion coefficient slightly decreased initially, then increased, and finally increased rapidly. Finally, the mechanism of water diffusion at low water contents was discussed from the perspectives of β-transition and free volume changes.

Soybean protein isolate microgel (SPIM) was prepare by extreme acid combined with heat induction. The structural changes and molecular interactions of the protein, and the microstructure and gel properties of the microgel were explored by fluorescence spectroscopy, infrared spectroscopy, and atomic force microscopy, and the effects of different heat induction temperatures (25, 45, 55, 65, 75 and 85 ℃) on the structure and properties of the microgel were evaluated. The results showed that the relative content of β-sheet increased during the formation of SPIM, and electrostatic interaction, hydrophobic interaction and hydrogen bonding were involved in the self-assembly of microgels. In addition, with increasing temperature, the surface hydrophobicity index of SPIM increased first and then decreased, and that the thermal stability gradually increased. Compared with extreme acid, the specific surface area, emulsifying activity, emulsion stability and water-holding capacity of the microgel formed by extreme acid combined with heat induction at 75 ℃ were significantly increased (P < 0.05). Overall, extreme acid combined with heat induction is an effective method to regulate the structure and properties of protein microgels, and the quality of microgels can be improved by precise temperature control.

Oat β-glucan (OG) was used to replace salt in mutton mince at levels of 0%, 0.4%, 0.8%, 1.2% and 1.6%. To determine the appropriate level of OG replacement, the cooking loss, water-holding capacity (WHC), water distribution and content, color, gel strength, texture, secondary structure of myofibrillar protein, scanning electron micrograph (SEM) of mince samples with 2.0% salt, 0.4% OG + 1.6% salt, 0.8% OG + 1.2% salt, 1.2% OG + 0.8% salt and 1.6% OG + 0.4% salt were measured. The results showed that with increasing level of OG replacement, the cooking loss of mutton mince gels decreased first and then increased gradually, while the WHC showed the opposite trend. A significant decrease in the WHC was observed when 1.6% OG was added (P < 0.05). Low-field nuclear magnetic resonance (NMR) analysis indicated that high levels of OG replacement caused the transformation of weakly bound and free water into immobilized water in the gels. The brightness (L*) and whiteness of the gels increased gradually (P < 0.05), and the transverse cross-section showed an obvious white color. The rupture force and rupture distance of the gel with 0.4% OG replacement were good, indicating improved gel strength. High levels of OG replacement were unfavorable to the gel strength. The gel hardness, cohesiveness, chewiness and resilience significantly decreased at a substitution level of 0.8% (P < 0.05), and the gel elasticity showed a similar trend but with no significant difference between them (P > 0.05). The secondary structure of myofibrillar protein in the gel with high levels of OG replacement (> 0.8%) was similar to that in the control (P > 0.05), and the SEM image showed more loose structure with increased porosity. Through correlation analysis and principal component analysis (PCA), it was found that the synthetic score of the gel with 0.4% OG was higher than that of the other groups, which could ensure further reduction of salt intake while maintaining the gel quality of mutton mince.

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.

A thermophilic fungus, named HBFH10, was isolated from Luzhou-flavor Daqu and identified as Rhizopus microsporus. A new β-mannanase gene (RmMan134) from Rhizopus microsporus HBHF10, was cloned using degenerate primers, expressed, and characterized. The cloned RmMan134 gene had a total length of 552 bp without introns, encoding 183 amino acids and one stop codon. The expressed enzyme was composed of one signal peptide sequence of 19 amino acid residues and the catalytic region of the GH134 family. The optimal pH and temperature for the recombinant enzyme were 6.0 and 50 ℃, respectively. It had high thermal and pH stability. Its molecular mass was estimated to be approximately 18.5 kDa, and it was a glycosylated molecule. When konjac gum was used as the substrate, the Km and Vmax values of RmMan134 were 0.66 mg/mL and 57.1 μmol/(min·mg), respectively. RmMan134 exhibited the best clarification efficiency for orange juice, resulting in a 23.8% increase in its clarity, followed apple juice (11%) and peach juice (7%). Moreover, RmMan134 significantly increased the yield of grape juice by about 7%. Overall, RmMan134 has good application prospects in juice processing.

The inhibitory mechanism of α-amylase and α-glucosidase by cyanidin-3-O-glucoside was investigated by ultrafiltration, high performance liquid chromatography (HPLC), enzyme kinetics, and molecular docking. The results indicated that cyanidin-3-O-glucoside inhibited α-amylase and α-glucosidase in a reversible and non-competitive manner. Besides, the fluorescence quenching analysis indicated that cyanidin-3-O-glucoside combined with the two enzymes by hydrogen bonds to form a complex. Molecular docking analysis showed that cyanidin-3-O-glucoside interacted with the key amino acid residues of α-amylase and α-glucosidase through hydrogen bonds and hydrophobic forces, and the binding energies were −7.8 and −9.8 kcal/mol, respectively. Our research suggests that cyanidin-3-O-glucoside has the potential to be used as an inhibitor of α-amylase and α-glucosidase in the development of functional foods.

In this study, the nicotinamide riboside kinase 1 gene (ScNRK1) was cloned from Saccharomyces cerevisiae, and its soluble expression in Escherichia coli was achieved using pET28a plasmid. The enzyme activity in the fermentation broth was 14.75 IU/mL, and the specific activity the purified enzyme was 2 252.59 IU/mg. In addition, the kinetic parameters of ScNRK1 were significantly higher than those of other reported nicotinamide nucleoside kinases, so ScNRK1 could be more advantageous in the enzymatic synthesis of nicotinamide mononucleotide (NMN).

In order to explore the role and function of the inlJ gene of Listeria monocytogenes (Lm) in phage sensitivity and biofilm, the inlJ gene-deficient strain Lm NJ05-ΔinlJ was constructed by homologous recombination. The growth, adhesion and invasion characteristics of the defective strain were identified. The results showed that compared with the wide-type strain Lm NJ05, the adhesion and invasion of RAW264.7 cells by Lm NJ05-ΔinlJ were significantly reduced to 20.05% and 4.42%, respectively. The efficiency of plaque formation was enhanced by 2.72 folds and phage vB-LmoM-NJ05 had a stronger lytic activity on Lm NJ05-ΔinlJ. Phage vB-LmoM-NJ05 at titers of 105 and 108 PFU/mL could completely inhibit and remove the biofilm of Lm NJ05-ΔinlJ, respectively. Transcriptional analysis of biofilm formation-related genes showed that the transcriptional levels of the degU, agrA, agrD, luxS, yneA, recA and hpt genes were significantly decreased to nearly zero in the defective strain after interacting with phage vB-LmoM-NJ05. In conclusion, deletion of the inlJ gene can enhance the phage sensitivity of Lm, and down-regulate the ability of cell invasion and biofilm formation. Therefore, the inlJ gene not only regulate Lm but also affect its interaction with phage, which lays a foundation for the development and application of phage biocontrol.

In this study, the contents of (Z)-3-hexenal and (E)-2-hexenal during oolong tea processing were measured and four (3Z):(2E)-hexenal isomerase (HI) genes were selected based on transcriptomic data. Meanwhile, the correlation between the changes of (Z)-3-hexenal and (E)-2-hexenal contents and related gene expression was analyzed. The results indicated that during oolong tea processing, one of the two compounds fell, while the other rose. Mechanical damage caused by tossing increased and reduced the contents of (Z)-3-hexenal and (E)-2-hexenal, respectively. Subsequent spreading contributed to the transformation of (Z)-3-hexenal into (E)-2-hexenal, resulting in an increase in the content of (E)-2-hexenal. The four selected genes all responded to mechanical stress and water deficit stress. The constructed phylogenetic tree indicated that CsHI was closely related to many germin-like proteins in plants such as tea (Camellia sinensis) and carrot (Daucus carota). This study provides a reference for clarifying the formation and transformation mechanism of volatile substances during oolong tea processing and improving the quality of oolong tea.

In this study, we applied PacBio Sequel II and Illumina NovaSeq 6000 sequencing platforms to sequence the genome of a high-polymalic acid (PMLA)-producing strain, Aureobasidium melanogenum CGMCC18996, and used different assemblers to obtain a high-quality genome assembly, which was then annotated using transcriptomic data. The results indicated a total of 6 202 genes were found in the A. melanogenum genome, mainly involved in carbohydrate transport and metabolism, amino acid transport and metabolism, post-translational modification, RNA processing and modification. Meanwhile, functional annotation revealed that most genes in the genome were related to peroxisome in the strain. Transmission electron microscopy (TEM) indicated the existence of a circular peroxisome-like (glyoxysome) structure in the cells, demonstrating the ability to malic acid through the glyoxylate cycle. Finally, we predicted the protein structures of two enzymes related to PMLA biosynthesis, phosphoenolpyruvate carboxykinase (PCKA) and malate synthase (MASY). It was found that the enzymes could have the ability to synthesize malic acid. This study could provide a reference for metabolism regulation in A. melanogenum for improved PMLA production, and the assembled genome has been uploaded to the database, which could provide the basis for the future development and utilization of A. melanogenum CGMCC18996.

Metagenomic sequencing technology was used to analyze the microbial community structures and functional composition in three rounds of Daqu. The results showed that the average assembly length of the 25 samples was 100.5 Mb, a total of 439 000 gene catalogs were detected, and 5 104 species were identified. The results of species annotation showed that Kroppenstedtia eburnea was the dominant species, and the subdominant species were multiple Bacillus species. There was no significant difference in microbial community diversity between samples from the first feeding (Xiasha) and those from the first round of fermentation, and the β-diversity of the microbial community in samples from the second feeding (Zaosha) was higher than that in samples from Xiasha and the first round of fermentation. The results of gene functional annotation showed that the most abundant genes in Daqu were related to metabolism, while the most representative genes were related to carbohydrate metabolism and amino acid metabolism. The number of glycoside hydrolase genes in Zaosha samples was largest and the activities of related enzymes were highest. The above results indicated that the microbial community structures and functional composition in the three rounds of Daqu were basically consistent, whereas there was a difference in functional performance between the Zaosha samples and the other two samples.

The difference in the volatile flavors of five different Chinese acid-curd cheeses including milk fan, milk cake, Qula (yak milk cheese), Hurood cheese and milk knot was analyzed by sensory evaluation, gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS). The results of sensory evaluation showed that the five cheeses had a significant difference in flavor. Among them, dairy fan, with strong milky, fruity and bread-like aromas, had the best overall aroma performance and the highest preference score. The combination of GC-IMS and GC-MS expanded the detection range of volatile flavor compounds, and could more comprehensively reflect the volatile compounds in different Chinese acid-curd cheeses. The sensory evaluation results were verified by GC-IMS analysis. All five samples had their own characteristic peak areas, and the characteristic peak areas of dairy fan and Qula were significantly larger than those of the other samples. GC-MS analysis showed that the proportion of acids in dairy fan, Hurood cheese and Qula was the highest, the proportion of esters in milk cake was the highest, and the proportion of alcohols in milk knot was the highest. The calculation of odor activity value (OAV) combined with the results of principal component analysis (PCA) showed that ethanol, ethyl butyrate, ethyl caproate, 2-heptanone and δ-caprylactone were the major contributors to the flavor of dairy fan. Phenethyl formate, phenethyl acetate, caprylic acid, lauric acid and n-decanoic acid were the major contributors to the flavor of Qula. Dodecyl aldehyde was identified as the characteristic flavor compound of dairy cake. Partial least squares analysis (PLSA) revealed the correlation between aroma properties and volatile flavor compounds. Dairy fan has the potential to be developed and promoted in China because of its excellent flavor and consumer preference.

A method was developed for the rapid and sensitive detection of histidine using silver dendrimers as a substrate for surface-enhanced Raman spectroscopy in combination with azo-coupling reaction. The azo-coupling reaction of 3-aminobenzylamine, 3-anilinosulfonic acid or 2-fluoro-4-mercaptoaniline (2-F-PATP) with histidine was investigated. The Raman spectra of the resulting products revealed that 2-F-PATP gave the best Raman fingerprint for histidine, with a limit of detection (LOD) of 10-21 mol/L. The characteristic peaks (at 1 387 and 1 432 cm-1) of the azo-coupling product of histidine were selected for quantitative analysis, and the intensity of the characteristic peaks in the Raman spectra showed a linear relationship with histidine concentration in a certain range, with correlation coefficients (R2) of 0.975 61 and 0.968 84, respectively. This method can be used for the determination of bovine serum albumin, human serum albumin, α-lactalbumin and apple juice. The proposed method is sensitive and simple to use, and has good application potential.

In this study, the aroma compounds in Pu-erh ripe tea were enriched by means of atmospheric water distillation, and evaluated by gas chromatography-olfactometry (GC-O) after gradient dilution. A total of 22 aroma compounds with flavor dilution (FD) factor log4 equal to or greater than two were identified. Qualitative and quantitative analysis of these aroma compounds was performed using gas chromatography-mass spectrometry (GC-MS), and all of them, with odor activity value (OAV) greater than one, were identified as the key aroma compounds. Qualitative and quantitative analysis of the sequential distillation fractions was carried out using GC-MS, followed by analysis of the release pattern of the key aroma compounds by non-linear fitting model and heatmap cluster analysis. The results showed that the total concentration of key aroma compounds gradually decreased during boiling, and the concentrations of some key aroma compounds such as methoxybenzenes, alcohols and ketones also tended to decrease to different degrees with an increase in water vapor release. But the release pattern of aroma-active aldehydes conformed to the sin function, showing a trend of first increasing, then decreasing and finally increasing again. The concentration of each key aroma compound was analyzed by heatmap cluster analysis; the 22 key aroma compounds were divided into two categories, and the distillation fractions were divided into four categories. The contents of all aroma compounds in the first and second tubes were extremely high. The aroma of the 40th tube was very light with a stronger unpleasant odor, and the contents of most key aroma substances dropped to extremely low levels. This study helps to understand the release pattern of key aroma compounds during the boiling process of Pu-erh ripe tea, and provides a theoretical basis for the recovery and application of aroma compounds from Pu-erh ripe tea.

In this study, the wine grape cultivar Vitis vinifera L. cv. ‘Petit Verdot’ was used as the scion for ‘101-14’, ‘5BB’, ‘SO4’, ‘Beta’ and ‘1103P’ rootstocks as well as self-rooted control. The volatile components of ‘Petit Verdot’ grape berries from the commercial harvest period in 2016–2017 were analyzed by using head space solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the climate differences between vintages were the decisive factor affecting the contents of volatile components in ‘Petit Verdot’ grapes, which were also significantly affected by rootstocks. Compared with the self-rooted control, all five rootstocks significantly increased the contents of C6/C9 compounds in grapes. ‘5BB’ significantly increased the contents of C13-norisoprenoids and terpenes, ‘1103P’ significantly increased the content of bound carbonyl compounds, ‘101-14’ significantly increased the content of free carbonyl compounds and significantly decreased the content of bound C13-norisoprenoids, ‘Beta’ significantly increased the contents of bound C13-norisoprenoids and terpenes, and ‘SO4’ significantly increased the contents of C13-norisoprenoids, bound carbonyl compounds and free terpenes. Orthogonal partial least squares-discriminant analysis (OPLS-DA) results showed that C6/C9 compounds, such as (E)-2-hexenal, (Z)-2-hexenal and hexanal, were the common differential volatile components to differentiate the grafted grapes from the self-rooted ones. In general, grafting ‘Petit Verdot’ onto the rootstock ‘5BB’ in Beijing was conducive to the accumulation of terpenes and C13-norisoprenoids in grapes during harvest.

Based on the selective quenching effect of the flavonoid rutin on the fluorescence of carbon dots prepared by asparagine pyrolysis, a method for rapid detection of rutin content in the flower buds of Sophora japonica by using chitosan-based carbon dot paper chip was developed. A filter paper was immersed in the casting solution of carbon dots and chitosan. After drying, a carbon dot chitosan film was formed on the surface of the filter paper, so that the chitosan-based carbon dot paper chip was obtained. After samples were dripped on the chip, chromogenic reaction occurred uniformly within a limited region, and pictures were taken under an ultraviolet (UV) lamp at 365 nm for analysis of the red (R), green (G), and blue (B) values of the colored spots in order to optimize the preparation conditions and detection conditions. The results showed that the optimal conditions were as follows: chitosan concentration of 20 mg/mL, carbon spot concentration of 1.0 mg/mL, 50% ethanol as sample solvent, and reaction time of 20 min. Under these conditions, the difference (ΔG) in G-value between sample and solvent spots had a linear relationship with rutin concentration (C) in the range of 4 to 120 mg/mL. Using this method, the average contents of rutin in the flower buds of S. japonica from three batches were determined to be 23.85%, 22.83% and 20.30%, the average relative standard deviations (RSDs) were 6.1%, 5.6% and 6.7%, and the recoveries were 91.27% to 107.5%, which were close to the results of high performance liquid chromatography (HPLC). The proposed method is simple and rapid, and can be used for rapid on-site determination of rutin content in the flower buds of S. japonica.

In this study, the composition of volatile flavor substances during the fermentation of cream was analyzed by solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). A total of 32 volatile substances were identified at five different periods, among which acids were the most abundant. Principal component analysis (PCA) revealed that the composition of volatile compounds differed at different fermentation periods, and samples from different periods could be clearly distinguished. Nine key flavor components, including capric acid, caprylic acid, δ-decalactone, 2-nonanone and 3-hydroxy-2-butanone, were identified by calculating odor activity values (OAVs). Five sensory attributes of the samples were scored by descriptive sensory analysis. The correlations between key flavor substances and sensory attributes were analyzed by partial least squares regression (PLSR) analysis, and it was found that the fermented and creamy flavor had strong correlations with capric acid, capric acid, δ-decalactone, 2-decanone, 2-nonanone and 3-hydroxy-2-butanone. This study is of great significance to regulating the production of fermented cream.

To explore the effect of growing altitude on the quality of Zhenghe white tea, the sensory quality and biochemical composition of tea leaves and Zhenghe white tea from different altitudes were evaluated, and multivariate statistical analysis was applied to the obtained data. The results of sensory evaluation showed that there were significant differences in the quality of white tea from different altitudes. The mid- and high-altitude white tea tasted fresh, mellow and clean with a clean and pure aroma, while the low-altitude white tea tasted mellow and thick with a floral aroma. Partial least squares discriminant analysis (PLS-DA) showed that soluble sugars, caffeine, 3-carene, verbenenol, terpene oleene, cis-2-pentenol, 2-ethylfuran and cis-2-hexene-1-alcohol were the key components to distinguish fresh tea leaves from different altitudes. The contents of soluble sugar, cis-2-hexene-1 alcohol and cis-2-pentenol were higher in the mid- and high-altitude samples, while the contents of volatile components such as caffeine, 3-carene, verbenol and terpinolene were higher in the low-altitude samples. Soluble sugar, free amino acid, terpinolene, verbenol, 2-ethyl furan, 2-methylbutyraldehyde, 2-phenylethanol and 3-carene were the key components to distinguish white tea from different altitudes. The contents of soluble sugar and free amino acid were higher in the high-altitude white tea, and the contents of volatile components such as terpinolene, verbenol, phenyl ethanol and 3-carene were higher in the mid- and low-altitude samples, but low in the high-altitude samples. According to odor activity value (OAV) analysis, 2-methyl butyl aldehyde, 3-carene and terpinolene could be used as the characteristic volatile components to identify white tea samples from different altitudes. The results of this study will provide a reference for further exploring the flavor quality of tea from different altitudes.

To investigate the difference in the comprehensive quality of free amino acids (FAA) in crayfish meat from different co-culture modes, the FAA composition of crayfish tail meat from three representative co-culture modes in Xinghua city of Jiangsu province was determined, and the contribution of FAA to the taste of crayfish meat was evaluated by computing the taste active value (TAV). Comprehensive evaluation of FAA in crayfish meat was performed using principal component analysis (PCA) and cluster analysis. The results showed that 17 amino acids were found in crayfish meat from each co-culture mode, and the total amount of FAA was 21.80–27.11 mg/g. Arginine (Arg) was the most abundant FAA in all samples, accounting for 55.64%–67.76% of the total FAA, which was much more abundant than the other amino acids. Moreover, Arg contributed the most to the taste of crayfish meat. The TAV of the sweet amino acid alanine (Ala) and the bitter amino acid histidine (His) in crayfish were greater than 1 for all co-culture modes, indicating that both amino acids contributed to the taste of crayfish meat. The TAV of glutamic acid (Glu) as the amino acid with the strongest umami taste was greater than 1 only in crayfish meat from rice-crayfish mode with one-rice and two-crayfish in a field (RC2). Three principal components were extracted for the 17 amino acids, which cumulatively explained 89.937% of the total variance and could reflect the comprehensive information of amino acids in crayfish meat. The results of PCA showed that RC2 ranked first, and crayfish-crab mode (CC1) ranked last. The hierarchical cluster analysis divided crayfish meat from different co-culture modes into three categories. Similar results were obtained by PCA. This study demonstrated that the comprehensive quality of FAA in crayfish from rice-crayfish co-culture mode was better than that in crayfish from the other co-culture modes.

Odor compounds produced in salted egg yolk during thermal processing were identify by sensory evaluation and gas chromatography-mass spectrometry (GC-MS) combined with multivariate statistical analysis such as hierarchical cluster analysis (HCA), orthogonal partial least squares-discriminant analysis (OPLS-DA) and principal component analysis (PCA). By using quantitative descriptive sensory analysis, it was found that there was a significant difference in the flavor profile between egg yolk samples with and without unpleasant odor, and it was determined that some egg yolks had obvious off-flavor during hot processing. Cluster analysis showed that the six groups of salted egg yolk samples were clearly divided into two categories, which was consistent with the sensory evaluation results. Furthermore, OPLS-DA identified 33 major differential components with variable importance in the projection (VIP) scores greater than one between samples with and without unpleasant odor, and aldehydes and alcohols were the most significant differential components. Finally, the volatile compounds showing a positive correlation with sour odor were screened by PCA, and n-hexanal, n-valeraldehyde, 1-octen-3-ol, trans,trans-2,4-decadienal, styrene, dimethyl disulfide and 2-nonone were identified due to their odor activity values (OAV) greater than one as the major odor compounds of salted egg yolk during thermal processing. The results provide a reference for analysis of the flavor characteristics and possible off-flavor components of salted egg yolk after thermal processing and provide a scientific basis for accessing the quality of salted egg yolk.

Herein, we used an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) system to investigate changes in the profile of non-volatile metabolites in green tea after different periods (15, 40, 80 and 120 days) of storage at 37 ℃. The color of green tea and tea infusion changed after 40 days of storage at 37 ℃ when compared with the control (stored at −80 ℃). During 40 days of storage, the content of catechins did not significantly change, but the content of free amino acids significantly decreased. A total of 684 non-volatile components were identified, 77 of which were found to be characteristic differential metabolites, the major ones being polyphenols, lipids and organic acids. The content of octadecadien-6-ynoic acid, an umami-related compound, significantly decreased after 40 days and was undetected after 80 days. The content of theaflavine-3-catechin, related to the color and taste of tea infusion, significantly increased with storage time. Similarly, the content of flavone glycoside increased with storage time. Moreover, the content of lipids such as triacylglycerols (TAGs) and diacylglycerol (DAGs) changed significantly after 15 days, and the content of free fatty acids increased with storage time. The findings from this study showed that the contents of lipids and flavonoids in green tea significantly changed during storage, which played an important role in the quality deterioration of green tea.

The dominant spoilage bacteria in chicken feet with pickled peppers were analyzed by high-throughput sequencing technology and isolated by the traditional culture method to evaluate their spoilage capacity by back inoculation. The results showed that the dominant genus identified was Bacillus, and four dominant strains were identified including B. methylotrophicus, B. velezensis, B. subtilis and B. safensis. All these strains were able to produce protease and lipase activity. Among them, B. safensis showed the strongest protease activity (51.19 U/mL), while B. methylotrophicus showed the strongest lipase activity (3.75 U/mL). The pH, total volatile basic nitrogen (TVB-N) content and thiobarbituric acid reactive substances (TBARS) value of the samples inoculated with each of the four Bacillus strains were higher than those of the uninoculated control group, indicating that all four Bacillus strains had spoilage capacity. This study will provided a theoretical basis for preventing and controlling the spoilage of chicken feet with pickled peppers and extending its shelf life.

In this study, the low-level presence of genetically modified (GM) soybean event GTS-40-3-2 was quantitatively detected and the measurement uncertainty was estimated. Within 95% confidence interval, the quantitative method developed using real-time polymerase chain reaction (PCR) and digital PCR could stably detect 0.01% GTS-40-3-2 content with acceptable cost and uncomplicated operation, while the digital PCR method could quantify 0.1% GTS-40-3-2 content accurately, and the quantitative error did not exceed 50% even at GTS-40-3-2 content as low as 0.05%. The sources of uncertainty in quantitative digital PCR analysis were analyzed, and the calculation formula for uncertainty was derived from calculation models in analytical chemistry. Furthermore, GTS-40-3-2 was used for laboratory verification. The expanded uncertainty in quantitative analysis of 0.1% and 0.05% GTS-40-3-2 contents was calculated as 23.56% and 107.29% (k = 2), respectively.

In this study, an analytical method was established to determine pentachlorophenol (PCP) in milk powder by isotope dilution-liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sample was dissolved in water, extracted by the quick, effective, cheap, easy, rugged and safe (QuEChERS) method using acetonitrile as the extraction solvent and protein precipitant, purified on a Captiva EMR-Lipid column, and diluted with the same volume of water before analysis. The chromatographic separation was achieved on a C18 column (100 mm × 2.1 mm, 1.7 μm) with gradient elution using a mobile phase composed of methanol and 5 mmol/L ammonium acetate solution (containing 0.05% formic acid), and then the analyte was detected with negative electrospray ionization (ESI-) in the multiple reaction monitoring (MRM) mode. Matrix matching-isotope dilution internal standard method was used for identification and quantification of the analyte. The results indicated that the calibration curve of PCP was linear in the concentration range of 0.2‒150 μg/L with correlation coefficients (r) not less than 0.996 0. The limits of detection (LOD) and quantitation (LOQ) of the method were 0.5 and 1.5 μg/kg, respectively. The average recoveries for spiked milk powder ranged from 90.3% to 119.2%, with relative standard deviation (RSD, n = 6) equal to or less than 7.5%. The method has the advantages of simple pretreatment without concentration or dissolution, high sensitivity, accuracy and reliability, and can be used as an effective method for detecting pentachlorophenol in milk powder.

An indirect competitive-enzyme linked immunosorbent assay (ic-ELISA) was established to detect the multi-residue of biphenyl tetrazolium sartans in antihypertensive health foods. Candesartan was coupled with bovine serum albumin to obtain immunogen. New Zealand white rabbits were immunized and a broad-spectrum antibody was obtained by an antibody screening assay. The half maximal inhibitory concentrations (IC50) for candesartan, losartan carboxylic acid, losartan potassium, olmesartan, olmesartan medoxomil, irbesartan, valsartan and valsartan methyl ester were 0.2, 0.2, 0.7, 0.04, 0.6, 0.3, 0.9 and 2.4 ng/mL, respectively. The samples were extracted with methanol and the matrix effect was eliminated by diluting the extract with standard solutions. The average recoveries of the eight target compounds were in the range from 80.6% to 120.0% with coefficients of variation equal to or below 14.0%. The results of ic-ELISA were highly correlated with those of liquid chromatography-tandem mass spectrometry (LC-MS/MS) (r > 0.97), indicating high accuracy and good reliability of ic-ELISA.

The relaxation signals of rapeseed oil, soybean oil, peanut oil, sunflower oil and corn oil were investigated using low-field nuclear magnetic resonance (LF-NMR), and the correlation between the composition of vegetable oils and their NMR relaxation characteristics was analyzed. Furthermore, a classification model for vegetable oils was established based on the echo attenuation information of LF-NMR using principal component analysis-linear discriminant analysis (PCA-LDA), and the effects of discriminant functions and the number of principal components (PC) on the model’s performance were studied. The experimental results showed that the decreasing order of the attenuation rates of the echo curves was peanut oil > rapeseed oil > corn oil > soybean oil > sunflower oil. The types of vegetable oils had significant effects on relaxation properties including T2W, T23, S23 and Stotal (P < 0.05). There existed extremely significant correlations between T2W, T22, T23, S23 and Stotal and the contents of C18:1, C18:2, C20:0, monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) (P < 0.01). The classification precision of the PCA-LDA model developed using linear discriminant function and 10 PCs for the training and prediction sets were 100.0% and 88.2%, respectively. It can be seen that it is feasible to identify vegetable oil species using LF-NMR. This study can provide a theoretical basis and technical support for quality and safety detection of different edible vegetable oils.

In order to study changes in the characteristic flavor of ultra-high temperature sterilized (UHT) milk under the influence of storage temperature and light, headspace solid phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to detect the volatile flavor components of the product. Descriptive sensory evaluation, orthogonal partial least squares-discriminant analysis (OPLS-DA) and entropy weight method were used to determine the relationship between major characteristic flavors and characteristic substances. The effects of temperature and light flux on the flavor changes of different formulations of UHT milk were analyzed, and a model for comprehensive analysis of the characteristic flavors of UHT milk was developed based on the effects of initial unsaturated fatty acid content, temperature and light flux. The results of this research provide support for the quality control of different formulations of UHT milk.

In this study, headspace-solid-phase microextraction extraction combined with gas chromatography-orbitrap-mass spectrometry (HS-SPME-GC-Orbitrap-MS) was used to establish a method for the simultaneous determination of five aldehydes and ketones and four furans in fruit wines. The method was validated on model wine, goji berry wine, blueberry wine and hawthorn wine. The limits of detection (LODs) for all target compounds ranged from 0.004 to 6.300 μg/L, and the limits of quantification (LOQs) were between 0.01 and 21.00 μg/L. The recoveries of all analytes in spiked wine samples were between 81% and 120% and the relative standard deviations (RSDs) for precision were equal to or less than 19.08%. This method is accurate and can meet the requirements for the quantification of aldehydes, ketones and furans in fruit wines.