To study the stability of antioxidant peptides extracted from fermented sausage under conditions simulating those occurring during industrial processing and gastrointestinal digestion, we investigated the effects of temperature, pH, food additives, metal ions, and simulated gastrointestinal digestion on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, Fe2+-chelation ability and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging activity. The results showed that the radical scavenging rate decreased significantly (P < 0.05) at high temperature and in acid and alkaline environment, while the Fe2+-chelation rate increased, but only slightly. NaCl, glucose and sucrose were beneficial to improve the radical scavenging activity, while they inhibited the Fe2+-chelation activity. NaNO2 had little effect on the antioxidant activity of the peptides when added at levels within the range permitted by the national standard. The antioxidant peptides were more sensitive to Cu2+ than to K+. The DPPH radical scavenging activity was completely lost after the simulated gastrointestinal (GI) digestion, but the Fe2+-chelation activity increased by 1.4 times compared with that before the digestion. The ABTS cation radical scavenging rate was stable at about 40%, and the total free amino acid content gradually increased.

This study investigated the functional properties of blends of normal barley starch (NBS) and waxy barley starch (WBS) with different mass ratios (75:25, 50:50 and 25:75) in excess water (water content 95%, m/m) such as solubility, swelling power, water absorption capacity, pasting properties, gel strength, and freeze-thaw stability. The results showed that with increasing amount of WBS, the solubility and puncture force of the blends significantly fell (P < 0.05), whilst the swelling power and water absorption capacity reached the maximum at WBS50. The pasting curves measured by a rapid viscosity analyzer showed that with increasing amount of WBS, the peak viscosity significantly increased (P < 0.05). Meanwhile, NBS75:WBS25 possessed the highest pasting temperature (P < 0.05). Furthermore, with increasing amount of WBS, the freeze-thaw stability of starch blends significantly improved after different freeze-thaw cycles (P < 0.05), which was verified by the results of electron microscopy scanning. Our present study indicated that changing the mass ratio of NBS to WBS had a significant effect on the functional properties of starch blends. This study provides a theoretical basis for the application of WBS and NBS blends in the food industry.

Considering that soymilk is a complex system, this study designed three model systems (glucose + Bowman-Birk inhibitor (BBI), fructose + BBI, and soybean protein (SP) + BBI) to examine the contribution of reducing sugar, SP and heat treatment to BBI inactivation. Without heating, glucose could enhance the activity of BBI, but fructose could not. With heating, reducing sugar could obviously affect trypsin inhibitor activity (TIA) of BBI, but only slightly affect its chymotrypsin inhibitor activity (CIA); glucose affected BBI more obviously than did fructose. SP could affect CIA of BBI more obviously than its TIA; BBI could link to basic peptide chains of glycinin by disulfide bonding to form a dimer, and also could interact with SP to form a polymer by disulfide bonding; in addition, BBI could interact with itself to form a BBI dimer. Under the conditions of incubation in boiling water bath for 3 h, and BBI, glucose, fructose, and SP concentrations of 2 mg/mL, glucose made the greatest contribution to TIA inactivation, followed by heat-induced conformation change, fructose and SP, while SP made the greatest contribution to CIA inactivation, followed by heat-induced conformation change, and glucose/fructose.

This study investigated and compared the inhibitory effect of various polyphenols on the formation of off-odors in thermally processed muskmelon juice using sensory evaluation combined with the Friedman test and multiple comparison analysis. Qualitative and quantitative analysis of the off-odor compounds in muskmelon juice with and without added catechin, genistein, daidzein, phlorotannins or pyrogallol was conducted using headspace solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS), and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to characterize the inhibitory action of each polyphenol on the off-odor compounds. The results revealed that the sensory evaluation was consistent with the instrumental analysis of the types of inhibited off-odor compounds and the percentage inhibition. The five polyphenols at the same concentration of 0.1 mg/mL had different inhibitory effects on the formation of thermally-induced off-odors. Catechin exhibited the strongest inhibitory effect, followed by phlorotannins, daidzein, genistein and pyrogallol, and the effects of catechin, phlorotannins and daidzein were significant (P < 0.05). The combined use of catechin and daidzein could serve as the best way to prevent and minimize the generation of heat-induced off-odors in muskmelon juice. This study provides theoretical guidance to overcome the problem of heat-induced off-odors in muskmelon juice as a representative of thermosensitive fruits and vegetables and to develop deeply processed products.

This study investigated the effects of amino acids on the quality of western-style smoked sausage and the formation of N-nitrosodimethylamine (NDMA), N-nitrosodi-npropylamine, NDPA) and N-nitrosopyrrolidine (NPYR). Different concentrations of sodium nitrite (0, 150 and 480 mg/kg) and three amino acids (arginine, alanine and proline) at 1 000 mg/kg were added to study their effects on the texture, color, pH, thiobarbituric acid reactive substances (TBARS), moisture, cooking loss, residual nitrite and the formation of N-nitrosamines in western-style smoked sausage. The results showed that arginine and alanine reduced residual nitrite, while proline had the reverse effect. The three amino acids significantly increased NDPA content. Proline resulted in a significantly higher NPYR content compared with the other amino acids. The three amino acids significantly increased hardness, cohesiveness, chewiness, a* value and pH value, and reduced L* value, b* value, TBARS value and cooking loss. Arginine increased springiness while alanine and proline reduced springiness. Adhesiveness was increased by arginine and proline, but was reduced by alanine. All three amino acids could improve the product quality and inhibit the oxidation of the product. Thus, they could be used as quality improvers. However, they could also promote the formation of N-nitrosamines. The contents of these three amino acids in the product should be reduced to inhibit the formation of N-nitrosamines. This study can lay a theoretical foundation and provide reference for further research to improve the product quality, inhibit the formation of N-nitrosamine and understand its formation mechanism.

In this study, single factor experiment and response surface methodology (RSM) based on Box-Behnken design (BBD) were used together to optimize the hydrolysis process of Porphyra haitanensis protein by acid protease. The antioxidant activity and molecular mass distribution of the hydrolysates at different hydrolysis times were measured. The results showed that under the optimized hydrolysis conditions (substrate concentration of 2 g/100 mL, enzyme/substrate of 4 240 U/g, pH value of 3.7, temperature of 54 ℃, and hydrolysis time of 4 h), the highest degree of hydrolysis (DH) of 11.40% was obtained. The relationship between DH and antioxidant activity of the hydrolysates was investigated. It was found that the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the 4 h hydrolysate (DH = 11.40%) was the strongest with a half maximum inhibition concentration (IC50) of 0.68 mg/mL, and that small molecular mass peptides (< 1 kDa) accounted for 73.46% of the total peptides in the hydrolysate. This hydrolysate was fractionated by gel filtration chromatography, yielding an antioxidant peptide (named PHAP). PHAP at 1 mg/mL concentration scavenged DPPH and hydroxyl radicals by 73.32% and 30.15%, respectively. It was confirmed that PHAP could repair H2O2-induced oxidative damage in HepG2 cells by enhancing the activity of superoxide dismutase and decreasing the content of malondialdehyde.

Effects of adding zein, soy protein isolate (SPI) or whey protein isolate (WPI) on the retrogradation of proso millet starch were investigated by textural profile analysis (TPA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results showed that adding the three proteins decreased the hardness of proso millet starch gel, making the mixed gels softer. Particularly, upon the addition of WPI, the hardness decreased from 407.32 g to 196.12 g at day 7. FTIR showed that no new functional group appeared, indicating that the starch-protein system is closely linked together by hydrogen bonding interactions, forming a tightly wound three-dimensional gel network structure. XRD analysis showed that in the retrogradated sample a strong diffraction peak appeared at around 17° as a typical B-type structure. Adding the proteins significantly reduced the retrogradation enthalpy, thus suppressing the recrystallization of proso millet starch and consequently retarding its retrogradation. By fitting the aging kinetics with the Avrami equation, it was found that the rate of recrystallization was reduced upon the addition of the proteins, and the nucleation type of recrystallisation was close to rod-like growth of sporadic nuclei (1 < n ≤ 2). Overall, addition of zein, SPI and WPI affected proso millet starch in varying degrees, with the greatest effect being observed with WPI. This study shows that the proteins act not only as nutrients but also as a starchy food anti-aging agent, which provides a theoretical basis for delaying starch aging and is of guiding significance for actual production.

This study analyzed the farinographic properties and starch viscosity properties (rapid viscosity analyzer (RVA) parameters) of wheat flour doughs with 0%, 40%, 45% and 50% replacement of wheat flour by raw dehydrated potato flour, and compared the stretching characteristics and gas production capacity of wheat doughs incorporated with unblanched and blanched raw dehydrated potato flour at the different proportions and the wall hanging rate and sensory quality of the resultant Nang, in order to determine the effect of hot blanching on the quality of raw dehydrated potato flour incorporated Nang. The results showed that addition of raw dehydrated potato flour changed water absorption rate, dough formation time, stability time, weakening degree and farinograph quality number (FQN) to different extents, and increased starch RVA parameters overall and setback value. Incorporation of blanched raw dehydrated potato flour at proportions above 40% could significantly increase the tensile resistance and stretching ratio of dough, enhanced the fermentation capacity and gas production capacity, and resulted in a wall-hanging rate of Nang up to 100%. However, the sensory attributes such as flavor and color of Nang incorporated with blanched raw dehydrated potato flour were significantly lower than those of Nang made from pure wheat flour.

In an attempt to explore the effect of protein on starch properties, we measured the pasting, rheological and textural properties and microstructure of buckwheat starch added with different proportions of mung bean protein utilizing a rapid visco analyzer, a rheometer and a texture analyzer. The results showed that the pasting time and temperature of buckwheat starch were increased while peak viscosity, final viscosity, breakdown value and setback value were reduced by adding mung bean protein. As the addition of mung bean protein increased, shear stress and consistency coefficient K declined while the starch paste was still a pseudoplastic fluid. An 8:2 ratio of mung bean protein to buckwheat starch showed more significant shear thinning. Both storage modulus (G’) and loss modulus (G”) were reduced, loss angle tangent (tanδ) was increased and gel strength was weakened by the addition of mung bean protein. Moreover, the hardness, gumminess and chewiness of the starch gel were significantly decreased and the elasticity became slightly lower. As observed by scanning electron microscopy (SEM), the starch gel showed a honeycomb-like microstructure with the pores becoming larger and the cell wall becoming thinner with increasing addition of mung bean protein.

Three sweet potato residue cellulose (SPRC) powders with different particle sizes (129, 64, and 25 μm) were obtained by ordinary pulverization, ultra fine pulverization and nano-ball milling, respectively. Each of them was separately added at 7% to wheat flour in order to determine their effects on the rheological properties of wheat dough. The results showed that SPRC increased the water absorption rate of dough, prolonged the dough formation time, and reduced the dough stability time, maximum viscosity index, thermal gel stability, retrogradation value and gelatinization value. In addition, SPRC increased the viscoelasticity of dough. Temperature had a great influence on the elastic modulus (G’) of the mixed dough, but had no significant influence on the viscous modulus (G’’). Scanning electron microscopy showed that the gluten network structure in dough incorporated with large-particle-size SPRC exhibited rupture and holes, but reducing the particle size of SPRC improved its density uniformity. Compared with ordinary pulverization and ultra fine pulverization, nano-ball milling SPRC enhanced the farinographic properties and thermomechanical properties of dough. Accordingly, the particle size of SPRC had a significant impact on the rheological properties of wheat dough. Reasonable control of the particle size of added dietary fiber in wheat flour can be useful to improve dough quality.

This study investigated the effect of pitaya stem phytosterol (PSP) on stability, membrane properties and in vitro release property of curcumin nanoliposomes (NLs-Cur). The stability of PSP-incorporated Cur-NLs was evaluated by particle size, polydispersity index (PDI), zeta potential and instability index in different environments. The results showed that the average particle size and PDI of curcumin-phytosterol nanoliposomes (PNLs-Cur) increased significantly with increasing content of PSP. Stability experiments showed that PNLs-Cur was more stable than NLs-Cur was under the same pH and ion conditions, and PNLs-Cur had higher retention rate of curcumin than NLs-Cur did at 80 ℃ for an hour (61.25% versus 57.48%). In addition, the cumulative release rates of PNLs-Cur and NLs-Cur were 50.08% and 63.64% within 72 h, respectively. In vitro release experiments indicated that the incorporation of PSP led to slower release of curcumin encapsulated in the nanoliposomes

This study aimed to compare the differences in lipid oxidation, protein oxidation and eating quality among cured chicken meat with different NaCl concentrations (0%, 3%, 6%, 9%, 12% and 15%). The results showed that with the increase in NaCl concentration, the carbonyl content and surface hydrophobicity increased significantly while the sulfhydryl content decreased significantly, and the thiobarbituric acid reactive substances (TBARS) value and protein solubility increased first and then decreased. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the increase in NaCl concentration promoted the formation of disulfide bonds, resulting in increased protein cross-linking and aggregation. With regard to the eating quality, as NaCl concentration increased, both the pH and moisture content first increased and then decreased, whereas the opposite trend was noted for the cooking loss. L* value was significantly reduced with increasing NaCl concentration, and a* value significantly increased upon the addition of NaCl, but did not significantly change with increasing NaCl concentration. b* reaches the maximum when NaCl concentration is 3%. Overall, the increase in NaCl concentration promoted lipid oxidation and protein oxidation, and consequently affected the eating quality of chicken.

In our study, the formation mechanism of the ternary complex of β-lactoglobulin (β-LG) with folic acid (FA) as a hydrophilic molecule and retinol (VA) as a hydrophobic molecule was explored by fluorescence spectroscopy. The changes in the antioxidant activity and allergenicity of β-LG after complexation were examined by 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging, 1,1-diphenyl-2-picrylhdrazyl (DPPH) radical scavenging and ferric ion reducing antioxidant power (FRAP) assays as well as indirect enzyme-linked immunosorbent assay (ELISA), respectively. Fluorescence spectroscopy indicated that FA and VA had a strong ability to quench the fluorescence of β-LG mainly in a static mode．FA and VA could form stable ternary complexes with β-LG through hydrophobic interaction, which was reflected by the binding constant (Ka) > 104 L/mol, the number of binding sites of β-LG for FA and VA (about 1) and the thermodynamic parameters. The presence of VA affected the affinity of FA for β-LG, while the presence of FA did not affect the affinity of VA for β-LG. The results of ABTS, DPPH and FRAP assays showed that the antioxidant activity of β-LG-FA and β-LG-VA was not significantly different compared with that of β-LG, but lower than that of β-LG-FA-VA. Different binding sequences had no significant effect on the antioxidant activity of the ternary complex. Indirect competitive ELISA showed that β-LG-FA-VA gave a lower inhibition of 42.23% against β-LG antigenicity, while β-LG-VA-FA exhibited a higher inhibition of 70.32%. These results indicate that different binding sequences had different effects on the antigenicity of β-LG.

This study investigated the effects of five frying oils (peanut oil, soybean oil, rapeseed oil, 24° palm oil and 42° palm oil) on the content of benzo(a)pyrene in French fries, Youtiao (fried dough stick), and chicken nuggets in order to control the content of benzo(a)pyrene in fried foods. The content of benzo(a)pyrene in French fries, Youtiao and chicken nuggets sequentially fried with each of the oils at 176 ℃ for 165, 150 and 210 s (two batches daily for 5 successive days) was investigated using liquid chromatography. The results showed that with increasing number of frying cycles, the content of benzo(a)pyrene in all three fried foods also increased gradually. All the foods fried in peanut oil contained the highest level of benzo(a)pyrene, which was 1.64 μg/kg in French fries, 1.73 μg/kg in Youtiao and 1.15 μg/kg in chicken nuggets. In contrast, all the foods fried in 42° palm oil contained the lowest level of benzo(a)pyrene, which was 0.04 μg/kg in French fries, 0.10 μg/kg in Youtiao and 0.05 μg/kg in chicken nuggets. In conclusion, this study showed that 42° palm oil had better frying stability and the fried foods with it contained lower content of benzo(a)pyrene compared to the other oils.

For a better understanding of its metabolic mechanism and function during mutton fermentation, the whole genome of Lactobacillus helveticus TR13, a strain with high lipase activity isolated from naturally air-dried mutton was sequenced using the PacBio Illumina HiSeq sequencing platform. The results showed that the genome of TR13 was a set of circular plasmid-free molecules, and the total length of the genome sequence was 2 172 224 bp with a GC content of 36.82%. It was predicted to contain 2 536 protein-coding genes with a total length of 1 883 532 bp, an average length of 799.46 bp, and an average density of 1.08 per kb, and the average sequence length of the coded proteins was 265 amino acids (aa), accounting for 86.71% of the genome. The genome of TR13 contained 15 rRNA operons and 63 tRNA, 75 virulence genes and 150 drug resistance genes being predicted from the genome. Moreover, functional annotation of the genome and metabolic pathway information annotation were accomplished by aligning the coding genes to the GO, COG and KEGG databases, which would provide a theoretical basis to explore the application of strain TR13.

Solid-state fermentation of sugarcane leaves was performed with Aspergillus niger for the purpose of extracting secondary metabolites. The effects of inoculum size, the water content of fermentation substrate and fermentation time on the release of phenolics from sugarcane leaves were investigated. The activities of cellulase and β-glucosidase were determined during the fermentation process. The antioxidant activity of the flavonoids extracted from native and fermented sugarcane leaves was investigated. The results showed that the contents of polyphenols and flavonoids in sugarcane leaves significantly increased after fermentation, reaching 10.40 and 13.82 mg/g on a dry basis under the following conditions: inoculum size 28 mL/100 g, water content of culture medium 50%, and fermentation time 5 days, which increased by 135% and 92% as compared with those in the unfermented samples, respectively. The activity of cellulase reached its maximum at 632.17 U/g on the fourth day of fermentation and the activity of β-glucosidase peaked at 75.02 U/g on the fifth day. Positive correlations were found between the contents of phenolic compounds and the activities of cellulase and β-glucosidase. By calculating the IC50, the flavonoids extracted from fermented sugarcane leaves exhibited stronger scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals than did those from the unfermented samples.

In order to study the effect of X-prolyl-dipeptide acyl-aminopeptidase (Pep X) activity of Lactobacillus on the antioxidant activity of Cheddar cheese, we obtained mutants with Pep X activity (named as UV-C3, UV-H3, UV-R3, and UV- P3, respectively) from Lactobacillus casei 1.0319, L. helveticus 1.0612, L. rhamnosus 1.0911, and L. plantarum 1.0202 by three rounds of UV mutagenesis and separately added them to Cheddar cheese. We analyzed the changes in Pep X activity and antioxidant activity during cheese ripening and established the correlation between them. Furthermore, we studied the effect of adding Pap X-producing Lactobacillus on cheese quality. The results showed that the activity of Pep X produced by Lactobacillus had a significant effect on the antioxidant activity and quality of Cheddar cheese. There was a significantly positive correlation between Pep X activity and the antioxidant activity of Cheddar cheese (P < 0.05). As maturation proceeded, the Pep X activity and antioxidant activity of cheese increased gradually up to the maximum on the 90th day. The activity of Pep X produced by UV-R3 was significantly higher than those produced by other strains (P < 0.05), and the maximum value was 10.16 U/g. The antioxidant capacity of the cheese inoculated with UV-R3 was significantly higher than those of the cheeses inoculated with other strains (P < 0.01), as evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate, hydroxyl radical scavenging rate, and reducing ability, and their maximum values were 68.43%, 67.56%, and 0.684 3 in the former sample, respectively. After the 120th day, as casein was hydrolyzed, bitter peptides were produced in a large amount, and the texture was remarkably lowered. The highest sensory flavor score of greater than 9.0 points was observed for all cheese samples, leading to the conclusion that they were edible at 120 days of ripening.

Antibacterial substances against Staphylococcus aureus from the fermentation supernatant of Bacillus amyloliquefaciens with improved antibacterial activity were separated and purified by sequential acid precipitation, organic solvent extraction, DEAE anion exchange chromatography and reversed phase-high performance liquid chromatography (RP-HPLC). Two antibacterial peptides were found in the purified product by liquid chromatography and mass spectrometry (LC-MS). One was a reported Surfactin homologue containing 13–15 carbon atoms; the other was a bacteriostatic peptide having the amino acid sequence of L-V-N-P-P-T with a molecular mass of 639.75 Da. The hexapeptide had an isoelectric point of 5.52, a GRAVY of 0.100, and a fat solubility index of 113.33 as analyzed by ProtParam software. The highest homology between this peptide with the bacteriopeptides reported in the APD database was only 37.5%, and it was inferred that it was a novel antimicrobial peptide. Surfactin and the hexapeptide showed antibacterial activity against both Gram-positive and Gram-negative bacteria.

A taste sensing system (SA402B) was applied to evaluate the taste characteristics of the meat samples of Eriocheir sinensis from five geographic origins, purse seined in lakes, wildly grown in natural waters or cultured inrice-crab coculture systems. The electronic tongue data showed that umami was the most predominant taste in steamed meat with a taste-active value (TAV) of 15.78–17.78, followed by bitterness (TAV = 7.33–13.53) and saltiness (TAV = 3.83–12.39). TAV for astringency (0.11–7.68) varied widely among geographic origins. There were no difference in sourness and only slight differences in richness (0–1.89), aftertaste-B (0–1.03) and aftertaste-A (0–0.38) among the samples, as reflected by the TAVs below ?30 and around zero, respectively. Linear discriminant analysis revealed that the accuracy of initial verification was as high as 100%. The scatter plot showed that all the five geographical origins could be clearly separated from each other. The results of the present study suggest that the taste sensing system can accurately profile the taste characteristics of E. sinensis from different geographic origins and that the electronic tongue data have the potential to discriminate the taste characteristics.

This study aimed to rapidly and quantitatively characterize subtle changes in the water distribution uniformity of noodle dough sheet by hyperspectral imaging technology combined with distributional homogeneity index (DHI) method. Firstly, noodle dough sheets with different water content gradients were set up, and different spectral pretreatment methods and pattern recognition methods were used to establish water prediction models. Then, visualization of the water content distribution in dough sheet was achieved using hyperspectral imaging technology. Finally, DHI was used to quantitatively characterize the water distribution uniformity in dough sheet at different mixing times. The results showed that the model constructed by least-squares support-vector machine (LS-SVM) based on spectra pre-processed by standard normal variate (SNV) had the best prediction performance. The water distribution was the most uniform when the dough mixing time was 15 min. This study verified the feasibility of using hyperspectral imaging technology combined with DHI for measuring the water distribution homogeneity of dough sheet, which would provide a theoretical guidance for the automatic monitoring of the noodle dough mixing process.

The contents of fatty acids, tocopherol and sterol in Moringa oleifera seed oils from eight areas in Yunnan province were analyzed. The differences in the fat-soluble functional components of the eight M. oleifera seed oils were analyzed by principal component analysis (PCA) and cluster analysis (CA). The results showed that a total of 20 fatty acids were found in these M. oleifera seed oils, mainly oleic acid (50.16%–56.51%), docosanoic acid (7.01%–12.03%), palmitic acid (4.91%–9.51%), stearic acid (6.76%–9.61%) and arachian acid (5.12%–7.24%), with unsaturated fatty acids accounting for 65.39% of the total fatty acids. The samples of M. oleifera seed oil all contained α-tocopherol (45–80 mg/100 g), δ-tocopherol (0.21–0.53 mg/100 g), and stigmasterol (243–495 mg/100 g). The results of PCA and CA showed that the compositions of functional components of the eight M. oleifera seed oil samples were similar, which fell into two distinct clusters according to different contents of functional components. The M. oleifera seed oil from Jinghong city, Xishuangbanna prefecture gained the highest comprehensive score, indicating a wide application prospect. This study provides data support and a scientific basis for further development of M. oleifera resources in Yunnan province.

In this research, gold magnetic nanoparticles (Fe3O4@Au) were formed by self-assembling method. Its physical and chemical properties were characterized. A highly sensitive and selective enzyme-free enhanced electrochemical sensor based on the peroxidase-like activity of composite nanoparticles was prepared for the detection of ascorbic acid (AA). Electrochemical cyclic voltammetry (CV) was used to measure AA and the electrochemical detection system was optimized. The results showed that the established enzyme-free electrochemical sensor showed an extremely high sensitivity towards AA under the optimized conditions, with a good linear relationship between the current response (y) and the concentration of AA (x) in the range of 1–100 mmol/L, which was fitted with the equation: y = 867.81x + 3.860 8 (R2 = 0.991 9), and the detection limit was 0.011 7 mg/L. In addition, the electrochemical sensor was successfully applied in the detection of AA in real samples. In view of this, the proposed new enzyme-free electrochemical assay has great potential in the fields of food quality control and safety detection.

Chinese wolfberries (Lycium barbarum L.) harvested at different developmental stages were analyzed for their physical and chemical properties. L. barbarum polysaccharides were purified and their structures were analyzed. The molecular mass, monosaccharide composition, sugar chain structure, thermal properties and surface morphology were determined by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR) spectroscopy comprehensive thermal analyzer and scanning electron microscopy (SEM). The HPLC results showed that L. barbarum polysaccharides were small molecules at different growth stages. The analysis of monosaccharide composition by GC-MS showed that L. barbarum polysaccharides were mainly composed of arabinose, rhamnose, glucose, xylose, mannose and galactose. The results of infrared spectroscopy indicated that the structure of the purified L. barbarum polysaccharides, found to be acidic polysaccharids, contained a β-pyran ring. Thermal analysis showed that the thermal characteristics of L. barbarum polysaccharides were both similar and different at different growth stages. The entire changes could be seen as mass losses sequentially caused by moisture release and polysaccharide breakdown. The observation by SEM showed that the structure of L. barbarum polysaccharides was different at different growth stages, and gradually changed from dense and lamellar to loose and peak-shaped and finally completely collapsed.

Changes in the contents of 3 free sugars and 18 free amino acids in two table corn cultivars (Jingtian 5 sweet corn and Jingnuo 8 waxy corn) during development from pollination after silking to milky maturation were determined using high performance liquid chromatography (HPLC). The contents of sucrose and alanine, as well as total sugars and total amino acids in both cultivars showed low-high-low trends with development time. Principle component analysis (PCA) and cluster analysis (CA) were applied to analyze the changes of these 21 compounds in the two cultivars at different developmental stages. Three PCs were extracted which explained 39.9%, 24.4%, and 13.3% of the total variance, respectively. Sweet amino acids and sugars presented high loadings on PC1 and PC2, illustrating that PC1 and PC2 are responsible to the sweet related informations. In addition, PC3 most correlated with the umami taste amino acids, aspartic acid and glutamic acid, and the samples from the different cultivars were separated on PC3. Moreover, CA showed that the samples were clustered into groups according to similar developmental stages. In conclusion, the PCA and CA performed on free amino acids and sugars clearly allowed to discriminate the developmental stages, and the cultivars to a lesser extent. These results would provide a practical reference for quality control of processed table corn products especially for corn juice flavor enhancement.

The volatile components in the pericarps and seed kernels of fresh Amomum tsaoko (ATK) from Nujiang, Yunnan were extracted by direct solvent extraction combined with solvent-assisted flavor evaporation (SAFE), and were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Thirty odor-active components (OACs), including 13 alkenes, 10 alcohols, 6 aldehydes and 1 ether, were identified by comparing the odor characteristics, mass spectrometry (MS) data, and retention indices with those of authentic compounds. Twenty-seven OACs were quantitated by using 2-octanol and 2-isopropylphenol as the internal standards. According to the quantitative results and the thresholds of OACs, the odor activity values (OAVs) of 22 OACs were calculated. Based on the OAVs obtained, a total of 17 key odorants (KOs) in the pericarps and 16 KOs in the seed kernels were determined. Some KOs, including 1,8-cineole, (+)-α-pinene, (E)-2-octenal, (E)-2-decenal, β-ocimene, linalool, α-terpineol, elemol, (E)-nerolidol, β-pinene, sabinene and 4-terpineol, were common to the pericarps and seed kernels, contributing to their similarities in odor notes. However, some odorants, including geranial, α-phellandrene, neral, terpinolene, (E)-2-dodecenal, β-myrcene, hexanal, d-limonene and β-caryophyllene, only occurred in either the pericarps or kernels, which made a distinction between their odors.

The epidermis of Poria cocos (Schw.) Wolf was used as the raw material to separate and prepare poricoic acid A and poricoic acid B by high-speed countercurrent chromatography (HSCCC). Total triterpenoids were extracted with n-butanol/water two-phase solvent system and fractionated into four peaks by HSCCC using a two-phase solvent system composed of hexane, ethyl acetate, methanol and H2O (3:6:4:2, V/V) under the conditions of clockwise rotation at a speed of 800 r/min, and a flow rate of 3 mL/min. The four peaks were collected and their purity was determined by high performance liquid chromatography (HPLC), and peaks III and IV with high purity were further identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). The results showed that peak III was identified as poricoic acid B and peak IV as poricoic acid A, which were 90% and 92% pure, respectively. The results of this study provide a simple and efficient method for the separation and preparation of poricoic acid A and poricoic acid B from Poriae Cutis, which is of great significance for the application of Poriae Cutis in the food and medical fields.

The sour substances in the muscle of Ryukyu squid (Symplectoteuthis oualaniensis) were determined and its sourness characteristics were evaluated by sensory omission experiments. The results showed that free amino acids, nucleotide-related compounds, opines, organic acids, inorganic ions and quaternary ammonium salts were the main sour substances of S. oualaniensis. The contents of alanine, taurine, glutamic acid, arginine, ATP, ADP, β-alanopine, meso-alanopine, tauropine, betaine, acetic acid, K+, Na+, and NH4+ were high. meso-Alanopine, β-alanopine, and tauropine were the characteristic sour substances in the muscle of Ryukyu squid, and they directly influenced the strength of sourness. Glu, Asp, Arg, Tar, Ace, K+, Na+, NH4+ and Cl- were the minor factors that constitute sourness.

In this study, four domestic hawthorn kernel liquid smokes: I, II, II-2002 and II-2003 and five liquid smokes produced by Red Arrow (USA): Smokez poly C-10-03, C-10-05, C-10-10, C-10-11, and C-10-22 were evaluated and compared for their flavor components using electronic nose and electronic tongue technology combined with gas chromatography-mass spectrometry (GC-MS). The results of electronic nose showed discrimination of the domestic liquid smokes from the imported ones, which had similarity in flavor. Principal component analysis performed on the electronic tongue data revealed that there were differences in overall taste profile among all liquid smokes except for oil-soluble C-10-11 and C-10-22, and C-10-03 and C-10-10 were mainly affected by salty taste while the five others were affected by salty taste, bitterness and astringency and richness. Besides, liquid smoke I was also affected by sourness. A total of 156 flavor compounds, including ketones, phenols, acids, aldehydes, alcohols, esters, nitrogen and other compounds, were identified by GC-MS. Ketones were dominant, followed by phenols and acids. Finally, a comprehensive evaluation model for the flavor of liquid smokes was obtained by principal component analysis. The comprehensive flavor scores of the nine liquid smokes were in the following decreasing order: C-10-05, C-10-10, C-10-03, C-10-11, C-10-22, II, II-2002, I, and II-2003, revealing the difference in flavor between hawthorn kernel liquid smokes and Red Arrow-produced liquid smokes.

Flavored peanut oil bodies prepared with nine combinations of pretreatment parameters (roasting temperature and time) were evaluated by fuzzy mathematic evaluation combined with gas chromatography-mass spectrometry (GC-MS) in order to select the best one. Subsequently, the volatile aroma components of flavored peanut oil bodies and the effects of characteristic compounds on the overall flavor were explored through principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The results showed that the sample with roasting pretreatment at 140 ℃ for 30 min gained the highest comprehensive score, with a light odor of raw peanut and strong characteristic flavor and without off-flavor, indicating good agreement between GC-MS analysis and fuzzy mathematics evaluation. Thus the optimal pretreatment parameters were determined to be 140 ℃ and 30 min. The results of PCA and OPLS-DA showed that heterocyclics, aldehydes and ketones, alcohols and phenols, and other components were the important components affecting the aroma of flavored peanut oil bodies. The key characteristic compounds in the four classes were 2-ethyl-6-methylpyrazine, N-methylpyrrole, 2,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, 2,3-dihydrobenzo furan, 3,5-diethyl-2-methylpyrazine; benzaldehyde, phenylacetaldehyde; 2-methoxy-4-vinylphenol; and 1-methylpyrrole-2-carboxylic acid methyl ester, respectively.

The taste components in yeast extract were analyzed by an automatic amino acid analyzer and high performance liquid chromatography (HPLC). Then the contribution of each taste component to the taste of yeast extract was evaluated by calculating the taste activity value (TAV), and the synergistic interactions between umami components were demonstrated through the calculated equivalent umami concentrations (EUC). Furthermore, the main taste components were determined by omission and addition test. Finally, yeast extract, salt and sucrose were used as raw materials to develop an umami-enhancing and deodorizing seasoning, and the optimal combination of the three ingredients was determined by single factor experiments and orthogonal array design. The changes in the taste of steamed silver carp fillets before and after the seasoning treatment were analyzed by electronic tongue. Results showed that sodium glutamate, alanine, 5’-GMP, 5’-IMP, sodium aspartate, arginine, tyrosine and 5’-AMP contributed the most to the taste of yeast extract. The EUC was calculated to be 184.48 g/g, indicating a strong synergistic interaction between umami amino acids (sodium glutamate and aspartate) and umami nucleotides (5’-GMP, 5’-IMP and 5’-AMP). The optimum formulation of seasoning for enhancing umami and reducing fishy odor consisted of 1% yeast extract, 1.5% salt, and 0.5% sucrose. After being pickled with the seasoning, the umami taste of silver carp fillets was obviously improved and the fishy odor was mitigated.

The characteristic flavors of 71 mutton samples from Altay, Bashibai, Bayinbuluk, Duolang, Hetian and Kazakh sheep from six different regions of Xinjiang respectively were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS). Out of these, 52 samples with similarities more than 85% were selected to establish flavor fingerprints according to the results of clustering analysis by Matching matrix in LAV (Laboratory Analytical Viewer) software. The differences between the characteristic flavors of mutton samples from different regions were compared, and the characteristic components, characteristic peaks, and characteristic marker substances and their contents were determined. The results indicated that 2-ethyl-1-hexanol was identified as characteristic ?avor compounds of Altay sheep meat; ethyl acetate, 3-methyl butyraldehyde and n-butanal as characteristic ?avor compounds of Bashibai sheep meat; benzaldehyde, 3-methylpentanoic acid and 5-methyl-2-furanmethanol as characteristic ?avor compounds of Bayinbuluk sheep meat; ethyl acetate and octanone as characteristic ?avor compounds of Duolang sheep meat; 2-octanol as characteristic ?avor compounds of Hetian sheep meat; and hydroxyacetone, (E)-2-heptenal and 3-hexen-1-ol as characteristic ?avor compounds of Kazakh sheep meat. Based on the fingerprints, principal component analysis (PCA) was performed, showing that there were differences among the characteristics flavors of Altay, Bashibai, Bayinbuluk, Duolang, Hetian and Kazakh sheep meat, especially among Altay, Bashibai, Duolang and Kazakh sheep meat, indicating that the flavor fingerprints can be used for evaluating the quality, tracing the origin and identifying the authenticity of mutton from different regions of Xinjiang.

This study aimed to analyze the differential volatile metabolites between Sichuan Baoning vinegar and Shanxi aged vinegar, both among the four famous vinegars in China. The volatile compounds of six samples of Sichuan Baoning vinegar and nine samples of Shanxi aged vinegar were qualitatively and quantitatively determined by gas chromatography-mass spectrometry (GC-MS). Using SIMCA-P+14.1 software, principal component analysis (PCA) was performed to examine the overall distribution between the two groups and the stability of the whole analysis process, and then orthogonal partial least-squares discriminant analysis (OPLS-DA) was used to discriminate the overall difference in metabolite profile between the groups. Finally, the points located at both ends of the S-plot with variable influence on projection (VIP) > 1 were selected as the potential markers that contribute the most to the differentiation between the two vinegars, and the differential metabolites between them were found. Multivariate data analysis showed that six flavor substances, furfural, ethyl acetate, 2,4-bis(1,1-dimethylethyl)-phenol, acetic acid, phenyl ethyl acetate and phenyl ethanol, were the potential markers that contributed the most to the discrimination between the two vinegars.

This study aimed to investigate the effects of processing techniques, including cold pressing, microwave-assisted cold pressing, accelerated solvent extraction, supercritical CO2 extraction, and subcritical fluid extraction on the yield, physicochemical properties, typical lipid concomitants contents, oxidation stability and in vitro antioxidant capacity of flaxseed oil. The results showed that microwave-assisted cold pressing significantly increased the yield of flaxseed oil by 4.3%–10.66% when compared with other techniques (P < 0.05). The physicochemical properties of flaxseed oils produced by the above five methods were different from one another but met the requirements of the Chinese national standard. Supercritical CO2 extraction possessed a better potential in the accumulation of α-linolenic acid in flaxseed oil (54.06%), which was 3.70%–5.31% higher than those of other techniques (P < 0.05). Moreover, the different processing techniques had specific effects on the typical lipid concomitants in flaxseed oil. The highest contents of tocopherols, carotenoids, chlorophyll, flavonoids and phospholipids were found in the flaxseed oils obtained by accelerated solvent extraction and microwave-assisted cold pressing. Subcritical fluid extraction significantly increased the contents of phytosterols in flaxseed oil (429.78 mg/100 g) by 5.07%, 9.34%, 15.57%, and 30.26% in comparison with other techniques (P < 0.05). The flaxseed oil obtained by supercritical CO2 extraction possessed the maximum total phenol content (13.60 mg/100 g), showing a 7.77%–68.53% increase when compared with those prepared by other techniques. Notably, the processing techniques had significant effects on the in vitro antioxidant capacity and oxidation stability of flaxseed oil (P < 0.05). The flaxseed oils prepared by accelerated solvent extraction and microwave-assisted cold pressing showed stronger oxidation stability and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity than those obtained by other methods, but the flaxseed oil obtained by supercritical CO2 extraction had a strong iron ion reducing power. These results will provide a theoretical basis for processing various kinds of flaxseed oil.

In this paper, soy protein isolate (SPI) was hydrolyzed by pepsin and then used to establish a stable SPI enzymatic hydrolysate-phospholipid complex emulsion system, aiming to find out a natural carrier that remains stable when passing through the stomach. Based on microscopic observation, particle size, potential, emulsion emulsification activity index (EAI), emulsion stability index (ESI) and creaming index (CI), we applied single factor experiment and orthogonal array design to determine the optimum composition of composite emulsions at pH 2.0 and 7.0. The results showed that the hydrolysis process was completed in 120 min. With increasing concentration of the protein hydrolysate, the stability of complex emulsions increased first and then remained unchanged. Maximum stability was observed for the complex emulsion with phospholipid concentration of 0.001 0 g/mL. With the increase of oil phase volume fraction, the stability of composite emulsions increased first and then remained unchanged. The emulsion with SPI hydrolysate concentration of 0.020 0 g/mL, phospholipid concentration of 0.000 5 g/mL and oil phase volume fraction of 10% was the most stable at pH 2.0, as determined by orthogonal array design

The physical properties of yuba were determined with a texture analyzer, a chromometer and a scanning electron microscope. We studied the correlation between the raw material components and the yield and eating quality of yuba, and we optimized the processing conditions. The results showed that when the soybean milk concentration was 6%, pH 8.0, temperature 90 ℃, the ratio of protein to fat 3:1, and the ratio of protein to carbohydrate 4:1, the highest yield of yuba of 43.13% was obtained with a tensile strength of 12.46 g/mm2 and an elongation at break of 9.85%. The eating quality of yuba prepared from soybean milk with a ratio of 11S to 7S protein of 4:1 was the best. Compared with the traditional production process, the yield and tensile strength at break of yuba produced using the optimized process were increased by 10.11% and 74.02%, respectively. In comprehensive evaluation of yield, mechanical properties and color, the optimized yuba scored 17.7% higher than that produced using the traditional process.

A droplet digital polymerase chain reaction (ddPCR) method was developed for the rapid and quantitative detection of Escherichia coli O157:H7 in foods. A pair of primers and a probe were designed specific for the single copy gene of hlyA in E. coli O157:H7. The specificity, sensitivity and repeatability of this method were evaluated. At the same time, the plate counting method, real-time PCR and the ddPCR method were compared through the detection of artificially contaminated salmon samples using them. The results indicated that the ddPCR method had excellent specificity, sensitivity and repeatability in E. coli O157:H7 detection. The limit of detection (LOD) and limit of quantification (LOQ) for pure bacterial culture were 105 and 25 CFU/mL, respectively. The sensitivity of this developed method was 110 CFU/g in artificially contaminated salmon samples. At different levels of artificial contamination in salmon samples, there was no significant difference (P > 0.05) between the results of ddPCR and plate counting, which were more stable and accurate than the results of real-time PCR. Therefore, the established ddPCR method can detect E. coli O157:H7 in food samples more rapidly, accurately, sensitively and specifically.

A method for the determination of deuterium content in drinking water labeled low deuterium by thermal conversion/elemental analysis-isotope ratio mass spectrometry (TC/EA-IRMS) was established. The water sample was filtered through a 0.22 μm filter membrane, and 2 mL of the sample was transferred to a vial. The sample volume was 0.1 μL. The reactor temperature was 1 380 ℃, the column temperature was 85 ℃, and the carrier gas flow rate was 100 mL/min. Each sample was analyzed 4 to 6 times. The accuracy of the calculated deuterium content was improved by eliminating the first data point and the top space of the sample vial to avoid the influence of the void space and memory effect on the measurement of δ2H. This method was suitable for the determination of deuterium content in drinking water within the range of 12.624–155.760 μg/g, and the relative standard deviation (RSD) between the measured and theoretical values was less than 0.6%. The relative deviation (SD) of deuterium content in one deuterium-depleted water sample was 0.08 μg/g for 8 consecutive measurements, and 0.086 μg/g for 3 measurements within 30 days, indicating good repeatability and reproducibility. The RSD for the determination of water samples with low deuterium content by different instrumental methods was lower than 1 μg/g. The deuterium contents of 8 deuterium-depleted packaged drinking waters were tested. Generally, the measured and labeled values were not consistent with each other. Determination of deuterium content in deuterium-depleted water by TC/EA-IRMS can provide technical support and a theoretical basis for supervision and testing of deuterium content in packaged drinking water labeled low deuterium.

A new method for screening pesticide residues in vegetables and fruits by multi-plug filtration cleanup (m-PFC) method combined with gas chromatography-quadrupole time of flight mass spectrometry (GC-QTOF-MS) was developed. The samples were extracted with acetonitrile, purified by m-PFC, and detected by GC-QTOF-MS. Qualitative analysis was carried out by retention time and accurate mass measurements in full scan mode and quantitation was performed using matrix-matched standard calibration, which could effectively eliminate matrix interference. Twelve typical samples (Chinese cabbage, celery, tomato, cucumber, spinach, Chinese leek, pakchoi, tangerine, pear, apple, grape, and orange) were used to evaluate the method. Good linearity was achieved for 234 pesticides in the concentration range of 5 to 500 μg/kg with correlation coefficients greater than 0.990. The results showed that the limits of detection of this method were in the range of 5–20 μg/kg. The average recoveries at three spiked levels of 10, 50, and 100 μg/kg were in the range of 73.2%–124.8%, 75.5%–122.6% and 74.8%–121.7%, with relative standard deviations (RSDs) of 2.4%–13.2%, 2.8%–11.4% and 2.2%–10.5%, respectively. The method could effectively improve the detection efficiency of high-resolution mass spectrometry for high throughput screening of pesticide residues in vegetables and fruits, thereby having great potential for practical application.

In this study, we discriminated the geographical origin of Hunan Anhua dark tea by using inductively coupled plasma mass spectrometry (ICP-MS) combined with chemometrics. Quantitative analysis of 48 elements such as B, Li and P was carried out in Hunan Anhua dark tea and those from other geographical origins by ICP-MS, and an elemental fingerprint for Anhua dark tea was obtained. The element distribution in dark teas from different geographical origins was evaluated by characteristic analysis, discriminant analysis, principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). In the PCA and the PLS-DA score plots, Anhua dark tea was effectively discriminated from those from other regions. Nineteen elements including Li, Pb and Ga were significantly different between Anhua dark tea and those from other regions. Seven key elements (Li, Pb, Ga, Ce, Rb, Cs and Na) were introduced into?the discriminant?analysis?model. The correct discrimination rate of the mode was 100% and 98%?in back substitution and cross-validation test, respectively. The results showed that the elemental fingerprint could be used for the geographical origin discrimination of Anhua dark tea.

A multi-residue analysis method was developed for the determination of 121 pesticides in Houttuynia cordata Thunb. by the QuEChERS extraction procedure (the abbreviation of quick, easy, cheap, effective, rugged and safe) coupled with gas chromatography-tandem mass spectrometry (QuEChERS-GC-MS/MS). This method was applied for screening of 68 sample batches. The pesticide residues from the samples were extracted with acetonitrile and purified by a modified QuEChERS method before being detected by GC-MS/MS in the multiple reaction monitoring mode. The results showed that all 121 pesticides exhibited good linearity in certain ranges with correlation coefficients (r) higher than 0.997 3. The recoveries of more than 90.9% pesticides ranged from 60% to 140% at three spiked concentration levels, with relative standard deviations of less than 15% for 86.8% of the pesticides. The limits of detection (RSN = 3) of this method ranged from 0.000 1 to 0.1 mg/kg, below 0.01 mg/kg for most of the selected pesticides. A total of 27 pesticide residues were detected from the 68 sample batches. This simple, sensitive and accurate method proved to be suitable for the fast screening and detection of pesticide residues in H. cordata Thunb. in order to provide?a?basis for the cultivation and circulation supervision of H. cordata Thunb..

The contents of 40 mineral elements in 180 Songjiang and non-Songjiang rice samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The mineral elements fingerprints were characterized by multivariate statistics including analysis of variance (ANOVA), correlation analysis, principal component analysis (PCA) and discriminant analysis, and a discriminant model for geographical origin traceability of Songjiang and non-Songjiang rice samples was developed. The results showed that the samples from different geographical origins displayed significantly different mineral profiles with significant correlations among mineral elements. Sixteen of these 40 mineral elements were selected for dimensionality reduction. As a result, the first five PCA factors were obtained. The geographical origins of rice samples were accurately discriminated from each other by a score plot of the first three PCA factors. The discriminant model based on the eight characteristic mineral elements B, Na, Fe, Co, Ni, Zn, As and Se constructed by linear discriminant analysis gave an overall correct discrimination rate of 93.0% to the training set. Besides, the discrimination accuracy was 95.2% (sensitivity) for Songjiang rice samples and 86.8% (specificity) for non-Songjiang rice samples. The cross-validation accuracy of discrimination was 84.2%–95.2% in the training set. The overall discrimination accuracy, sensitivity and specificity for the validation set was 92.1%, 96.0% and 84.6% in back substitution test, respectively. The overall discrimination accuracy for the validation set agreed with that for the test set, proving that the established model had good discrimination accuracy, sensitivity, specificity and stability and therefore, it was feasible to discriminate Songjiang rice from non-Songjiang rice.

A method of gas chromatography-tandem mass spectrometry was established for simultaneous detection of 41 organochlorine and pyrethroid pesticide residues in Lijiang-grown maca. Pesticide residues were extracted from the crushed samples with acetonitrile-sodium chloride saturated aqueous solution (5:4, V/V) with the aid of ultrasonic stirring. Then the extracts were purified with a graphitized carbon/amino composite column and eluted with a mixed solvent of acetonitrile and toluene (3:1, V/V). The purified extracts were separated with a medium-polar stationary phase (50% phenyl-methylpolysiloxane) capillary column. Finally, the analytes were detected by triple quadrupole mass spectrometry in the full scan mode, and quantified in the multiple reaction monitoring mode by an external standard method. The results showed that good linearity was observed for all analytes in the concentration range of 0.02–10 μg/mL or 0.04–20 μg/mL with a correlation coefficient (R2) over 0.99. The limits of detection (LODs) ranged from 0.01 to 2.38 μg/kg, and the average recovery rates of spiked samples varied from 90.2% to 108.8% with relative standard deviation between 2.1% and 10.9%. In summary, the proposed method proved to be simple, rapid, accurate, sensitive, economical and suitable for the screening and quantitative detection of organochlorine and pyrethroid pesticide residues in large batches of maca samples.

The distribution of veterinary drug residues in pork meat during slaughter and pre-cooling was evaluated in this experiment. A total of 240 samples of pork and viscera were randomly collected according to sampling method specified in the Sampling operating specification for the livestock and poultry and their products in slaughtering enterprises (NY/T 1897-2010), and they were analyzed for 43 veterinary drug residues by enhanced matrix removal lipid (EMR-L) cleanup followed by ultra-high performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS). Meanwhile, risk assessment of veterinary drug residues was carried out based on food safety index (IFS). The results showed that sulfamethazine, difloxacin and enrofloxacin were detected in the 240 samples. The detection rate of the 43 veterinary drugs was 5% at levels ranging from 2.43 to 19.94 μg/kg. The difference between the detection results after rigor mortis and maturation was not significant, indicating that there was no secondary pollution of the 43 veterinary drugs during slaughter and processing. At the same time, pork samples sold in Nanjing were collected and veterinary drug residues were detected in these samples with a detection rate of 4.4%. The IFS and values were found to be much less than 1, indicating that the levels of 43 veterinary drugs residues in pork products in Nanjing were acceptable.

A new method for simultaneous determination of eugenol, isoeugenol, methyl eugenol, methyl isoeugenol, aceteugenol and lsoeugenyl acetate residues in aquatic products by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed. The samples were extracted with acetonitrile and purified on an HLB solid phase extraction (SPE) column. Chromatographic separation was achieved on a Shim-pack GIST column (2.1 mm × 50 mm, 2 μm) by linear gradient elution using methanol/water as the mobile phase before analysis by UPLC-MS/MS. The method validation showed that good linearity (R > 0.999) was observed in the range of 1.00–500 ng/mL for the 6 eugenols. The limits of detection (LODs) were between 0.1 and 0.3 μg/kg, and the limits of quantification (LOQs) were between 0.3 and 1.0 μg/kg. The recoveries ranged between 83.9% and 105.4% at three spiked levels (2.00, 5.00, and 10.0 μg/kg) with relative standard deviations (n = 6) between 1.8% and 6.9%. This method proved to be simple, accurate, sensitive, and suitable for the quantitative determination of six eugenol residues in aquatic products.

A gas chromatography-negative chemical ionization-tandem mass spectrometry (GC-NCI-MS/MS) method for the determination of the residues of fipronil and its four metabolites (fipronil desulfinyl, fipronil sulfone, fipronil sulfide, and fipronil carboxamide) in animal-derived foods (egg, chicken, and chicken liver) was established. The samples were extracted with acetonitrile (saturated with n-hexane), and the extract was cleaned up using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method before being detected by GC-NCI-MS/MS in the multi-reaction monitoring (MRM) mode. The matrix matched standard curve method was used for quantitation. Results showed that there was a good linearity for all analytes in the range of 1–100 μg/L with correlation coefficient (r2) higher than 0.999 0. The limit of quantitation (LOQ, RSN ≥ 10) of the method was 0.5 μg/kg for fipronil disulfonyl, fipronil, fipronil sulfide and 1.0 μg/kg for fipronil sulfone and fipronil carboxamide. The average recoveries at three spiked concentration levels (2.0, 10.0, and 20.0 μg/kg) were 80.2%–108.7% with relative standard deviations (RSDs) of 3.8%–10.2%. This method exhibited high sensitivity and accuracy, and could be used for the determination of the residues of fipronil and its four metabolites in animal-derived foods.