The present study was carried out to optimize the fermentation conditions for exopolysaccharide (EPS) production by Bacillus amyloliquefaciens GSBa-1, isolated and screened from the traditional rice wine starter. The optimal fermentation conditions obtained by single factor experiments and response surface analysis were as follows: the culture medium consisted of peptone 10 g/L, yeast extract powder 5 g/L, sucrose 40 g/L, and NaCl 10 g/L and the fermentation was performed for 36 h at 35 ℃ with an inoculum size of 4% at a shaking speed of 160 r/min. The maximal production of EPS of 326.45 mg/L was obtained under the above conditions. The results of rheological studies indicated that the aqueous solution of the EPS had low viscosity, which increased with increasing its concentration and shearing rate. Measurement of molecular parameters by multi-angle laser light scattering showed that the weight-average molecular mass (mw) of the EPS was 4.993 × 105 g/mol, the radius of gyration (Rg) 48.34 nm, hydrodynamic radius (Rh) 64.62 nm, and Rg/Rh ratio (ρ) 0.748, indicating that the EPS molecule may be present as compact spheres. This was also confirmed by transmission electron microscope. The application of this EPS in acid milk beverage showed that the use of the EPS could improve the stability of the beverage without increasing its viscosity, indicating that the EPS from Bacillus amyloliquefaciens GSBa-1 can be potentially used as a novel food stabilizer.

The full-length sequence of 2-ketegluconate kinase gene (kguK) from was cloned from an industrial 2KGA producer of Pseudomonas plecoglossicida JUIM01 and expressed in the recombinant strain Escherichia coli BL21(DE3)/pET-28a(+)-kguK with isopropyl β-D-1-thiogalactopyranoside induction. The specific fusion protein KguK had a molecular weight of about 36.0 ku, which was confirmed by Western-Blot. The bioinformatics analysis showed that KguK in P. plecoglossicida was a hydrophilic protein with 305 amino acid residues. It was located in the cytoplasm, having a conserved domain similar to that of the pfkB family. The predicted secondary structure contained 35.73% of α-helixes, 12.79% of extended strand and 51.48% of random coil.

This study aimed to elucidate the effect of hly gene on the virulence of Listeria monocytogenes. We constructed a hly gene knockout mutant strain EGD-eΔhly from wild-type L. monocytogenes EGD-e by using a shuttle vector through homologous recombination. Biological characterization showed that there was no difference between the growth status of the mutant and parent strains. However, the mutant strain lost hemolytic activity, the cell invasion ability was decreased and there was no toxicity observed in animals receiving intraperitoneal injection at a concentration of 107 cells/mL. At the transcriptional level, the knockout of hly gene down-regulated the expression levels of virulence genes inlC and prfA by 81% and 76% respectively and up-regulated the expression levels of actA and plcB genes by 2.7 and 1.8 times, respectively. This paper may provide a basis for the study of the pathogenic mechanism of Lm.

Eleven bacterial strains and two fungal strains were isolated from Jiuqu, a traditional Chinese fermentation starter for rice wine. Out of these, one bacterial strain, designated LB-51, capable of producing rennet was screened by the casein plate method and the Arima method. The strain was identified as Bacillus amyloliquefaciens by its morphological characteristics, physiological and biochemical tests (API 50CHB system) and 16S rDNA sequence analysis and species specific gene analysis and named as B. amyloliquefaciens GSBa-1. The rennet and proteolytic activities were (431.53 ± 15.89) SU/mL and (5.05 ± 0.59) U/mL, respectively, after 72 h shaking culture (120 r/min) at 30 ℃ for 72 h in liquid LB medium. The enzyme exhibited high milk-clotting activity and low protein hydrolysis activity. The milk-clotting activity was 1.54 × 105 SU/g. B. amyloliquefaciens GSBa-1, an efficient producer and a safe source of rennet activity, is worth further research and development as a candidate strain for industrial production of rennet.

The liquid-state fermentation conditions for β-1,3-1,4-glucanase production by Aspergillus awamori CAU33, a fungal strain isolated from soil sample, were optimized using a combination of one-factor-at-a-time method and response surface methodology. The highest β-1,3-1,4-glucanase activity of 8 447 U/mL was achieved after 6 days of culture at 35 ℃ in a medium consisting of corncob 55 g/L, soybean peptone 25 g/L, and Triton X-114 23 g/L at an initial pH of 4.5, about 17.6 times higher than before the optimization.

The excessive use of antibiotics has brought about many adverse effects to natural ecology. Finding suitable alternatives to antibiotics to reduce the use of antibiotics is becoming a research hotspot. The aim of this study was to highly express the antimicrobial peptide moricin derived from the diamondback moth Plutella xylostella in Pichia pastoris, and study its antibacterial properties and biochemical properties. The mature peptide gene mor-3 of moricin from Plutella xylostella (L.) was amplified by PCR, and then cloned into the pGAPZα A vector, and an expression plasmid of pGAPZα A-mor3 was constructed. The linearized plasmid pGAPZα A-mor3 was transformed into P. pastoris SMD1168 by electroporation, and the high copy recombinant transformants were screened out by using high concentration of Zeocin. The molecular mass of the recombinant protein expressed in P. pastoris SMD1168 was approximately 5 kD, corresponding to the theoretical molecular mass of this target peptide. Up to 248.98 mg/L recombinant protein in the supernatant after 60 h fermentation was obtained. The recombinant protein in the supernatant showed obvious antibacterial activity against several microorganisms detected by an improved agar diffusion method, including Escherichia coli and Staphylococcus aureus. The minimum inhibitory concentration (MIC) against E. coli CMCC44103 was 6.25 μg/mL, while that against S. aureus ATCC25923 was only 124.49 μg/mL. It showed potent antibacterial activity against both Gram-positive and Gram-negative bacteria, especially Gram-negative bacteria. In addition, the recombinant protein also had good thermal stability, and strong resistance to acid and alkali. In particular, the antimicrobial activity was maintained in an acidic environment, and so it had good adaptability to the animal intestinal environment. Due to these unique antibacterial properties and biochemical characteristics it has a broad development and application prospect with good social and environmental benefits.

Objective: The aim of this study was to analyze the genetic diversity of mungbean varieties from Inner Mongolia region and to establish a simple sequence repeat (SSR) fingerprinting database for providing scientific evidence to explore the genetic background of mungbean germplasms and authenticate mungbean varieties. Methods: A total of 92 mungbean varieties from Inner Mongolia area were taken to establish their genetic diversity and DNA fingerprint maps by using 10 pairs of SSR primers. Results: A total of 58 alleles were detected, and each pair of primers detected 3–10 alleles with an average of 5.8. The genetic diversity coefficients among the 92 mungbean varieties varied from 0.033 4–1.000 0 with an average of 0.46. Unweighted pair-group method with arithmetic means (UPGMA) clustering analysis showed that these mungbean varieties were clustered into 2 groups at theof genetic similarity coefficient of 0.294 4. SSR fingerprinting database and molecular identification of the 92 mungbean cultivars were established, and it was found that most of the tested varieties, with different SSR fingerprints, which could be molecularly discriminated from each other, could serve as cultivars-specific patterns and as an important basis for cultivar identification. Conclusions: There was a high level of genetic diversity among mungbean germplasms from Inner Mongolia, but a certain degree of inbreeding also existed. Therefore, further efforts are needed to develop new mungbean breeding materials. SSR fingerprinting and molecular identification using fluorescent labeled SSR marker technique is of great significance for genetic authentication, identity validation, traceability management and origin protection of mungbean varieties.

The changes in fungal communities in Pixian soybean paste during post-fermentation were analyzed using high-throughput sequencing method in order to reveal the essence of ‘being kept under sunlight in the daytime and being allowed to absorb moisture in the air at night during the fermentation process’. The results revealed that at the taxonomic levels of microbes, including phylum, class, order, family, and genus, high-throughput sequencing method could detect 3 phyla, 20 classes, 47 orders, 77 families and 106 genera. It was shown that the fungal community in Pixian soybean paste was highly diverse and abundant. The dominant microbes were greatly changed during the post-fermentation process; the quantities of Pleosporaceae and Sclerotiniaceae continued to reduce, while those of Saccharomycetaceae, Saccharomycodaceae and Pichiaceae increased firstly and then decreased. In addition, a large number of non-cultivated fungi and unclassified fungi were also found in this study. The observed fungal diversity was highly similar to the microbial ecology of the investigated samples. This study may provide scientific support for the modernization of the traditional Pixian soybean paste industry as well as food safety and quality control.

In order to screen lactic acid bacterial strains (LAB) with good performance for the fermentation of traditional cured meat products, nine strains of LAB were isolated and purified from home-made cured meat products. Out of these nine isolates, strain 10M-7 was selected for its good fermentation properties and it was prepared into a starter culture by freeze-drying method. Effects of the starter culture on sensory quality and microbial growth in fermented sausage were examined using naturally fermented sausage without any starter cultures as a control. The results showed that strain 10M-7 had good acid production performance and antibacterial properties, and it was identified as Lactobacillus plantarum according to its morphological, physiological and biochemical characteristics and 16S rRNA sequence alignment. The pH value of LAB-fermented sausage decreased apparently during the early fermentation period, which was always lower than that of the control. LAB in artificially fermented sausage grew rapidly and the numbers of Staphylococcus and Escherichia coli were significantly lower than those in the control group. Addition of the starter culture at 104 CFU/g raw meat could retain and improve the flavor of sausages so that the group exhibited better overall sensory acceptance.

The purpose of this study was to investigate the effect of fermentation conditions on the acidity and viable bacterial count of a beverage developed from quinoa malt fermented with lactic acid bacteria. Mixed starter cultures of Lactobacillus plantarum and Lactobacillus casei were used for the fermentation. One-factor-at-a-time method and response surface methodology were used to explore the effect of starter culture composition, inoculum amount and fermentation time on fermentation. A ratio of L. plantarum to L. casei of 2.5:1, an inoculum amount of 3% and a fermentation time of 10.3 h were found to be optimal. Under these conditions, the acidity of fermented quinoa malt was 85.32 °T and the viable count was 9.21 (lg(CFU/mL)), which were in good agreement with the predicted values. The result showed that homogenized quinoa malt was suitable for the growth of lactic acid bacteria.

The amino acid sequence of epitope peptides of the coat protein of strawberry mild yellow edge virus was predicted by bioinformatic tools including IEDB, DNAStar, DNAMAN and SnapGene. The peptide from the 27th to 38th amino acid residues with predicted high antigenic activity, referred to as AE, was reversely translated into its encoding DNA sequence according to the codon bias of E. coli. The encoding DNA fragment AE was then synthesized and cloned into the expression vector pET32a (+) between the EcoRⅠ and XhoⅠ sites. The open reading frame (ORF) containing the AE fragment was 561 bp, which encoded a fusion protein of 187 amino acid residues. The theoretical molecular mass of the recombinant fusion protein was 20.29 kD. Expression of the target gene in the recombinant plasmid pET32a (+)-AE was induced and optimized in E. coli BL21 (DE3) and E. coli Rosetta, respectively. The optimal expression conditions of the fusion protein in E. coli Rosetta were 1.5 mmol/L IPTG at 35 ℃ for 2 h, resulting in a yield of 13.22 mg/L, while those for expression in E. coli BL21(DE3) were 0.5 mmol/L IPTG at 30 ℃ for 2 h, giving a yield of 9.55 mg/L. The recombinant fusion protein was isolated by SDS-PAGE and identified by tandem mass spectrometry. The results showed that the recombinant fusion protein contained the designed peptide AE. The recombinant fusion protein was purified by Ni2+-affinity chromatography, digested by EK enzyme, and separated from the fusion protein tag by molecular sieve. Chicken immunoglobulin (IgY) was extracted from chicken eggs collected on the 21st day after the first injection. The binding activity of the IgY to AE and SMYEV was analyzed by the Dot-Blot method. The results showed that the IgY could specifically recognize both AE peptide and SMYEV indicating that the predicted AE peptide has desired immunogenicity.

Aims: To isolate and screen the antagonistic strains with inhibitory activity against Pseudomonas syringae pv. actinidiae from a soil sample collected from the rhizosphere of kiwifruit in different areas and to optimize the fermentation conditions for enhanced production of antibacterial substances. Methods: Antagonistic strains were isolated by pour plate method, screened by inhibition zone method, and identified by morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis. The optimal medium composition and fermentation conditions were optimized by one-factor-at-a-time and orthogonal array design methods. Results: A total of 288 actinomycetes strains were isolated, among which strain NA-TXL-1 exhibited the strongest inhibitory activity against Pseudomonas syringae pv. actinidiae. The effects of the fermentation broth in preventing and controlling Pseudomonas syringae pv. actinidiae in pot cultivated plants were 73.06% and 55.62%, respectively. Strain NA-TXL-1 was identified as Streptomyces antibioticus. The seed medium, inoculum size and initial pH value were optimized to be lactose-yeast power culture medium, 2%; and 7.0, respectively. The optimal culture medium consisted of 30 g/L lactose, 3 g/L yeast powder, 1 g/L NaCl, 0.5 g/L K2HPO4, 0.5 g/L MgSO4·7H2O, and 0.01 g/L FeSO4 at initial pH of 7.0. The optimal culture times for harvesting fermentation broth, the supernatant, and re-suspension were 5, 14, and 5 days, respectively. Conclusions: Strain NA-TXL-1 was identified as Streptomyces antibioticus, exhibiting stronger antagonistic effect under optimized fermentation conditions.

In order to investigate the influence of N-glycosylation on the expression of β-mannanase from Trichoderma reesei (Man1) in Pichia pastoris GS115, the asparagine (Asn) residues at three N-linked glycosylation sites (N131, N158 and N329) of Man1 were substituted by neutral glutamine (Gln) through site-directed mutagenesis. The results showed that mutations of the N-glycosylated sites had no significant effects on the expression of Man1 at the transcriptional level. Compared with Man1, the apparent molecular mass of the mutant Man1 decreased slightly, and the activities of the mutants (N131, N158 and N329) decreased by 85.43%, 79.48% and 16.3%, respectively. However, the thermal stability of mutant N131, N158 and N329 increased by 7.87%, 13.5% and 15.37% compared to that of Man1. Therefore, N-glycosylation especially at N131 and N158 was essential for the high-level expression of Man1 in P. pastoris GS115, but led to a slight reduction in the thermal stability of Man1.

In this study, we examined the effects of fermentation by pure cultures of Lactobacillus plantarum, Pediococcus pentosaceus, Enterococcus faecium, Saccharomyces cerevisiae and Bacillus, which play an important role in affecting the retrogradation properties of naturally fermented starch, on the molecular structure and retrogradation characteristics of millet starch with the aim of providing a theoretical basis and data support for elucidating the mechanism by which natural fermentation and pure culture fermentation improve the retrogradation properties of millet starch, and new ways of developing fermented millet products. Millet starch was extracted from fermented millet with 0.2 g/100 mL NaOH and evaluated for granular characteristics, functional groups, molecular mass and, pasting and retrogradation properties. The results obtained were as follows. Fermentation did not changed the cross polarization characteristics of starch. The surface of millet starch granules fermented by Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecium was eroded, but the surface of starch granules after fermentation by Saccharomyces cerevisiae and Bacillus was eroded more seriously, with more deeper channels. The fermentation by Saccharomyces cerevisiae and Bacillus did not change the peak positions in the functional region, but reduced the intensity of the characteristic peaks. The fingerprint region of millet starch fermented by Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecium partially disappeared, The weight average and number average molecular masses in regions Ⅰ and Ⅱ were decreased after fermentation by Lactobacillus plantarum. In region Ⅰ, the weight average molecular mass after fermentation by Pediococcus pentosaceus, Enterococcus faecium and Saccharomyces cerevisiae was increased, and the average molecular weight was decreased, while in region Ⅱ, the weight average and number average molecular masses were both decreased. After fermentation by Bacillus, the number average molecular mass in region Ⅰ was slightly increased, but the weight average molecular weight was slightly decreased; both the weight average and number average molecular weight in region Ⅱ were decreased. The gelatinization temperature, final viscosity and retrogradation value were decreased, but the enthalpy was increased after fermentation by Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecium. The gelatinization temperature and retrogradation value were decreased, the final viscosity and enthalpy were increased after fermentation by Saccharomyces cerevisiae. In conclusion, fermentation could change the molecular structure of starch, branched chain starch and amylose, and improve the short-term anti-retrogradation performance.

Cereals are the most important staple crops in China. However, cereals are low in iron (Fe) absorption, which is attributed as the major reason of nutritional anemia. Proper processing can relieve the inhibition of substances like phytic acid and polyphenol in grains on iron bioavailability (Fe BV). In this experiment, an in vitro digestion/Caco-2 cell model was used to assess the impact of yeast fermentation on Fe BV in wheat flour. Results demonstrated that after fermentation, the pH of wheat flour dough declined and consequently the acidity showed a rising trend. In addition, the contents of polyphenol and phytic acid declined and the phytase activity increased. All the above changes were statistically significant (P < 0.05). Fe BV of flour samples increased by 5%–38% after fermentation, with significant differences (P < 0.05) being observed for most wheat flours compared with that measured before fermentation. Fermentation can reduce the pH of wheat flour and increase the acidity, thereby promoting the degradation of polyphenol and phytic acid, increasing phytase activity, and effectively improving Fe BV in wheat flour.

The contents of 10 flavonol glycosides in 18 tea varieties were determined using ultra high performance liquid chromatography-quadrupole-time of flight mass spectrometry (UHPLC-QTOF-MS). The ratios of flavonol glycoside to flavonol galactoside were also calculated. The results showed that the glycosylation level of flavonol was higher in tea varieties with processing suitability for black tea when compared with those suitable for green tea processing. Kaempferol-3-glucoside, kaempferol-3-glucosylrutinoside, kaempferol-3-glucoside to kaempferol-3-galactoside ratio, quercetin-3-glucoside to quercetin-3-galactoside ratio, myricetin-3-glucoside to myricetin-3-galactoside ratio were significantly different (P < 0.05) among tea varieties with different processing suitabilities. The significant difference (P < 0.001) in kaempferol-3-glucoside and its ratio to kaempferol-3-galactoside indicates the potential for the discrimination of the processing suitability of tea varieties. The discrimination accuracy of tea varieties for their suitability for processing of green and black tea were 100% and 83%, respectively.

Solid phase micro-extraction combined with gas chromatography-olfactometry-mass spectrometry (SPME-GC-O-MS) was used to analyze the flavor compounds of cooked rice from seven indica rice cultivars and four japonica rice cultivars. The results showed that cooked japonica rice was slightly richer in volatile flavor compounds than cooked indica rice. The key flavor compounds of cooked indica and japonica rice were significantly different. Specifically, 2-acetyl-1-pyrroline was not detectable in indica rice samples while 4-vinylphenol was only detectable in japonica rice. The content of vanillin in japonica rice was significantly higher than in indica rice. However, the contents of 1-octene-3-ol, pentanal and hexanal in indica rice were significantly higher than in japonica rice. Thus, through principal component analysis (PCA) of the flavor components of cooked rice, we distinguished between indica and japonica rice.

Free and bound phenolics from Morchella angusticeps Peck were separately extracted and analyzed by ultra performance liquid chromatography-diode array detector/electrospray ionization-time of fight-mass spectrometry (UPLC-DAD/ESI-TOF-MS). The antioxidant activities of the phenolic extracts were assessed. The results showed that phenolics were present mainly in the free form in Morchella angusticeps Peck. The DPPH (1,1-dipheny1-2-picryl-hydrazyl) scavenging capacity, reducing power and oxygen radical absorption capacity (ORAC) value of free phenolics from Morchella angusticeps Peck were significantly higher than those of bound ones (P < 0.05), but no significant difference in ABTS+· (2,2’-amino-di (3-ethyl-benzothiazoline sulphonic acid-6) ammonium salt) scavenging capacity existed between free and bound phenolics. A total of 15 polyphenols in Morchella angusticeps Peck, including gallic acid, pyrogallic acid, protocatechuic acid, p-hydroxybenzoic acid, catechin, caffeic acid, chlorogenic acid, orientin, rutin, hyperoside, resveratrol, luteolin, quercetin, cinnamic acid and ferulic acid, were identified. We identified 15 and 14 components in the free and bound phenolic extracts, respectively.

NiO/g-C3N4 complex was successfully synthesized from NiCl2 and C3H6N6. The as-prepared NiO/g-C3N4 composite modified glassy carbon electrode by both casting method and electrodeposition showed remarkable electrocatalytic performance for ascorbic acid (AA). The peak current displayed a linear relationship with scanning rate in the range from 70 to 200 mV/s. The equations were depicted as follows: Ipa = ?34.14?1.167v, and Ipc= 53.42 + 0.357 8v, with correlation coefficients (R) equal to 0.998 and 0.982, respectively. Meanwhile, it was shown that the spike potential deviated with increasing scanning rate. This effect demonstrates that the electrochemical process was controlled by surface diffusion. The anodic current was proportional to the AA concentration and the calibration plot was Ipc= ?1.435 + 2.900C, R = 0.998, which was linear over the concentration ranges of 0.017 6 to 22.88 μg/mL. The detection limit (LOD) of the method was 0.008 8 μg/mL. Furthermore, results also showed that the sensor had good selectivity, stability and reproducibility and could be used to detect AA in juice samples with satisfactory results.

The contents of free amino acids and umami active nucleotides in the hepatopancreas, gonads and meat of female Portunus trituberculatus from the coastal areas of the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea were determined and compared by an electronic tongue, an amino acid autoanalyzer and high performance liquid chromatography (HPLC). The taste intensity was evaluated by taste active value (TAV) and equivalent umami concentration (EUC) methods. The results showed that the hepatopancreas, gonads and meat of crab from different sea areas were distinguished effectively with the electronic tongue. The content of free amino acids in hepatopancreas was the highest among three edible parts. IMP and AMP were more abundant than GMP. The free amino acid content and EUC in the hepatopancreas of Bohai Sea crab were 3 315.05 mg/100 g and 15.87 g MSG/100 g, respectively, higher than that of crabs from all other sea areas. However, the free amino acid content in the hepatopancreas of South China Sea crab was significantly lower than that in crabs from all other sea areas, but the contents of sweet-taste amino acids (accounting for 63.10% of the total free amino acids) and umami active nucleotides (the TAVs of IMP and AMP were greater than 1) were higher than those in crabs from all other sea areas. The contents of umami active nucleotides and EUC in gonads were the highest among three edible parts. The EUC value of the gonads of South China Sea crab was 36.46 g MSG/100 g, higher than that of crabs from all other sea areas. In crab meat, IMP was more abundant than two other umami active nucleotidess, and crab meat from the Yellow Sea had a lower IMP content compared to crabs from three other sea areas, with a TAV value of lower than 1, suggesting that IMP made no direct contribution to the umami taste of crab meat. The EUC of crab meat from the East China Sea was the highest, 7.19 g MSG/100 g.

Black buckwheat is widely used in many foods because it contains unique aroma components. This study aimed to prepare black buckwheat milk tea from black buckwheat tea infusion and fresh milk with added sugar. Volatile compounds were extracted by headspace-solid phase microextraction (HS-SPME) from black buckwheat milk tea and analyzed by gas chromatography-mass spectrometry (GC-MS) using a polar DB-WAX column or an HP-5MS weak polar column. The results showed that 44 and 33 compounds were separated on the two columns, respectively, and the relative contents of volatile compounds separated on the HP-5MS column were higher than on the DB-WAX column. A total of 57 volatile compounds were identified by using these two columns, including 15 pyrazines, 6 aldehydes, 5 ketones, 3 alcohols, 3 esters, 3 acids, 3 phenols, 2 alkenes, 17 heterocyclic and other compounds. The prominent compounds were pyrazines, aldehydes, heterocyclic and other compounds.

This study aimed to establish a near infrared (NIR) diffuse reflectance spectrometry method for measuring the contents of crude protein and starch in foxtail millet for providing a fast, simple and non-destructive analytical method for the identification and screening of foxtail millet germplasm resources. For this purpose, a total of 191 samples of a foxtail millet core collection in Shanxi province were measured using NIR diffuse reflectance spectroscopy. The results showed that with the spectral preprocessing method of first derivative + vector normalization, calibration models were established to predict the contents of crude protein and starch in foxtail millet. The corresponding coefficients of determination for calibration (R2cal) were 0.977 0 and 0.907 3, and the root mean square errors of cross-validation (RMSECV) were 0.203% and 0.466%, the coefficients of determination for external validation (R2val) were 0.989 6 and 0.977 2, and the root mean square errors of prediction (RMSEP) were 0.225% and 0.368%, respectively. For the detection of crude protein and starch foxtail millet, no significant differences were seen between chemical analysis and NIR measurement, but the results obtained with NIR measurement were more accurate and reliable. NIR diffuse reflectance spectrometry technology can be useful for the detection of crude protein and starch in foxtail millet.

In this study, anthraquinones were obtained by the hydrolysis of Semen Cassiae with a mixture of 20% sulfuric acid and chloroform. By using an orthogonal array design method the optimal conditions for extraction were determined as follows: extraction temperature 60 ℃, liquid-to-solid ratio 1:30 (g/mL), 20% sulfuric acid-to-chloroform ratio 0.6, and extraction time 3 h. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) radical scavenging and ferric reducing antioxidant potential (FRAP) assays were employed to determine the in vitro antioxidant activity of total anthraquinones extracted from Semen Cassiae from different regions. The results showed that the antioxidant capacity of total anthraquinones of Semen Cassiae from India was far lower than that of Semen Cassiae from any other selected region. The antioxidant activity of total anthraquinones extracted from Semen Cassiae from different growing regions was ranked as follows: Hebei > Henan > Anhui > Jiangxi > Shandong > India. The present study also determined 6 anthraquinone components in Semen Cassiae by HPLC. Results showed that the contents of both chrysophanol and aurantio-obtusifolin in Semen Cassiae from all regions from India and Henan were not lower than 0.2% and 0.08%, respectively, which reached the levels stated in the Pharmacopeia of China.

The effect of three kinds of Sichuan pickled peppers (made from Mexican pepper, wild pepper and Erjingtiao pepper) on flavor characteristics of silver carp surimi gel was investigated. The volatile components were identified by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and analyzed by principal component analysis (PCA) The overall taste was discriminated and evaluated by electronic tongue. The relative content of aldehydes (52.98%) was higher in control surimi gel, while the relative contents of alcohols (26.30%–39.78%) and esters (5.63%–17.05%) were higher in surimi gels added respectively with these pickled peppers. Pentanal, hexanal, and 1-penten-3-ol were identified as key odor components contributing to the overall odor of all four surimi gel samples. The principal components of surimi gels with the addition of pickled Mexican pepper and pickled wild pepper varied more significantly from those of the control surimi gel compared to the surimi gel added with pickled Erjingtiao pepper. The sourness and saltiness values of the three surimi gels added with pickled peppers were basically consistent. The umami value of the surimi gel added with pickled Erjingtiao pepper was the highest (0.82). The umami value of the surimi gel added with pickled Mexican pepper was the lowest (?0.65). There were no obvious differences in astringency, bitterness, and astringent and bitter aftertaste among four surimi gels.

The enzymatic hydrolysis of tartary buckwheat protein with neutral protease to produce antibacterial peptides was optimized using Plackett-Burman and Box-Behnken designs. One-factor-at-a-time experiments were carried out to investigate the effect of substrate concentration, enzyme-to-substrate ratio, pH, hydrolysis temperature and time on the antibacterial activity and peptide concentration of hydrolysates. The factors with a significant influence on the response variables were selected using Plackett-Burman design and optimized for maximum peptide concentration using Box-Behnken design. The optimum parameters for enzymatic hydrolysis were determined as follows: substrate concentration 3.22%, enzyme-to-substrate ratio 4 000 U/g and pH 6.86. Under these conditions, the peptide concentration was 32.41 mg/mL, in good agreement with the predicted value (32.12 mg/mL), and the percentage inhibition of antimicrobial peptides was (27.88 ± 2.78)% against E. coli and (94.56 ± 0.74)% against S. aureus. In conclusion, this optimized procedure was reasonable.

The stepwise enzymatic hydrolysis of Pacific oyster (Crassostrea gigas) for preparing angiotensin-Ⅰ converting enzyme (ACE) inhibitory peptides was optimized by orthogonal array design and response surface methodology (RSM). Pacific oyster was sequentially hydrolyzed by protamex followed by alcalase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and ACE inhibitory activity analysis were used to determine the optimal hydrolysis conditions. The results showed that the optimal conditions for the first hydrolysis step were determined as follows: solid to liquid ratio, 1:4 (g/mL); pH, 7.0; protamex dosage, 1.2%; hydrolysis duration, 1 h, and those for the second hydrolysis step were temperature were 53 ℃; pH, 8.3; alcalase dosage, 0.42%, and hydrolysis duration, 73 min. Gel filtration chromatography analysis showed that the molecular masses of almost all (99.72%) the peptides produced were lower than 3 000 D. Meanwhile, the oyster peptides revealed high ACE inhibitory activity, with IC50 of 0.8 mg/mL. Amino acid composition analysis indicated that glutamic acid was the most abundant amino acid while cysteine was the least abundant one in the peptide products. Among the total amino acids, essential amino acids accounted for 36.6% while hydrophobic amino acids accounted for 37.2%. Our present work can provide a theoretical reference for the development of antihypertensive peptides derived from oyster.

In an effort to overcome the functional and nutritional deficiencies of traditional Chinese liquor, wine was prepared from milk protein hydrolysates added with Chinese wolfberry juice. First of all, milk protein hydrolysates were prepared by enzymatic hydrolysis of skim milk and different proteases were compared in terms of sensory and chemical properties of hydrolysates for this purpose. Then, the hydrolysis process and the fermentation process were optimized using an orthogonal array design method. Besides, the antioxidant activity of the wine was assessed. The results obtained were as follows: 1) trypsin was the best protease for hydrolyzing milk protein; 2) the optimal conditions for enzymatic hydrolysis were 120 min hydrolysis at pH 7.0 and 40 ℃ with an enzyme dose of 4 500 U/g; and 3) the optimum fermentation conditions were addition of 14% (V/V) Chinese wolfberry juice to milk protein hydrolysates, which were then fermented at 28 ℃ for 9 days. The wine exhibited high antioxidant activity in vitro, having a harmonious aroma and a good taste. Moreover, its sensory and physicochemical indicators could meet or exceed the national standard of fermented sweet milk wine.

Oyster?enzymatic hydrolysate and glucose were used to establish a Maillard reaction system. The reaction conditions were optimized based on sensory evaluation and browning degree, and the nutritional quality of Maillard reaction products was evaluated by amino acid score (AAS), chemical score (CS), and essential animo acids index (EAAI). The optimal reaction parameters were determined as follows: glucose concentration, 8%; temperature, 110 ℃; pH value, 7.5; and reaction time, 90 min. In the Maillard reaction products, 18 amino acids were detected with essential amino acids (EAAs) accounting for 32.99% of the total amino acids. EAA index (EAAI) was 71.568 indicating high nutritional quality. Umami amino acids, especially glutamic acid, were abundant.

This research aimed to develop probiotic foods by fortifying probiotics in carrot using vacuum or ultrasonic impregnation. The vacuum and ultrasonic impregnation conditions were optimized by one-factor-at-a-time and orthogonal array design methods. The results showed that the optimum parameters for vacuum impregnation were obtained as temperature 35 ℃, impregnation time 15 min and restoration time 20 min and the optimum parameters for ultrasonic impregnation were temperature 30 ℃, ultrasonic power 125 W and impregnation time 12 min. The two techniques were compared with atmospheric pressure impregnation in terms of viable bacterial count and the results showed that the number of viable bacteria enriched by vacuum impregnation was the highest, reaching 1010 CFU/g. Scanning electron microscopy (SEM) confirmed the presence of rod-shaped bacteria being embedded in the intracellular space of vacuum and ultrasonic impregnated carrot samples, which were not observed within the tissue of samples impregnated at atmospheric pressure. However, there was a large quantity of bacteria observed on the surface of the samples impregnated under all three conditions. Vacuum impregnation can be considered a new approach for fortifying probiotics in carrot. The results of this research may provide new ideas for the development of functional probiotic foods.

The extraction and purification of polysaccharides from the stems and leaves of wild Taxus chinensis var. mairei (Lemée et Lévl.) Cheng et L.K.Fu grown in mountain areas in the south of Anhui province were investigated and their monosaccharide compositions were determined. The results indicated that flash extraction was the best method to extract polysaccharides from these plant materials. The yields of polysaccharides extracted from thin stems from Taiping county and leaves from Yi county were the highest (7.09 and 10.25 mg/g, respectively). Thin stems contained 10–20 times more polysaccharides than did thick ones. The Sevag method gave the highest deproteinization rate (66.5% and 69.1% for crude polysaccharides extracted from thin stems from Taiping county and leaves from Yi county, respectively). The highest decolorization rate (84.2% and 85.3% for the two crude samples, respectively) was achieved by using hydrogen peroxide. Infrared spectra of polysaccharides extracted from thin and thick stems as well as leaves were similar. The purified polysaccharides (Ⅰ, Ⅱ and Ⅲ) from thin and thick stems as well as leaves contained a similar monosaccharide composition with xylose being predominant, but varying in monosaccharide ratio. These findings can provide valuable information for the development and application of polysaccharides from Taxus plants.

In this study, the effect of pretreatment with dense phase carbon dioxidense (DPCD) on improving the enzymatic extraction of collagen from Chinese giant salamander skin was investigated. For collagen extraction, lyophilized Chinese giant salamander skin was pretreated with DPCD under different operating conditions of pressure and temperature, and then hydrolyzed by pepsin for different time periods. The optimization of these three parameters for improved extraction yield was performed using a combination of one-factor-at-a-time method and response surface methodology. The optimal enzymatic extraction conditions were found to be 6 h hydrolysis after DPCD pretreatment at 32 ℃ and 30 MPa. The model-predicted extraction yield under these optimized conditions was 39.70%, and it was not significantly different from the experimental value, (39.48±0.74)% (P > 0.05), 18.85% higher than that obtained without any pretreatment, (20.63±0.46)%.It was observed with a scanning electron microscope (SEM) that the microstructure of the skin became more loose, and collagen fibrils were damaged and became more orderly arranged and porous after DPCD treatment. The SDS-PAGE patterns showed that the typical characteristics of type I collagen was retained after DPCD treatment. Meanwhile, DPCD treatment significantly increased the extraction yield of collagen.

Based on the electrochemical redox properties of benzo(a)pyrene (BaP), a rapid electrochemical method for the determination of BaP in barbecued foods was established. The optimum conditions for the method were established as follows: using acetonitrile-water (1:3, V/V) as solvent, LiClO4 concentration (as electrolyte) 0.15 mol/L, sulfuric acid concentration 0.1 mol/L, and enrichment time 10 min, where the response current linearly increased with increasing BaP concentration in the range of 0–100 nmol/L. The limit of detection (LOD) of the proposed method was 0.187 nmol/L (RSN = 3). Excellent stability and reproducibility of the method were observed. The recovery of the analyte added to shish kebab was in the range of 96.67%–101.56%. The results were in agreement with those obtained by high performance liquid chromatography (HPLC). Consequently, the electrochemical method was useful for rapid determination of BaP in barbecued foods.

A new method based on matrix solid phase dispersion, ionic liquid-based homogeneous liquid-liquid microextraction and high performance liquid chromatography was developed for the determination of fluroquinolones (FQs), including enoxacin (ENO), pefloxacin (PEF), norfloxacin (NOR) and enrofloxacin (ENR) in muscle samples. Muscle samples were directly treated by matrix solid phase dispersion using silica gel as dispersant, 200 μL of 1-hexyl-3- methylimidazolium hexafluorophosphate ([C6mim]BF4) was used as extraction solvent, and aqueous solution of pH 1.0 was used as elution solvent. After the target analytes were transferred into eluate, ammonium hexafluorophosphate was added. The eluate obtained was treated by ionic liquid-based homogeneous liquid-liquid microextraction and the analytes were enriched into the ionic liquid phase. High performance liquid chromatography with diode array detection was applied to separate and determine the target analytes. The experimental results showed that the calibration curve exhibited a good linear relationship (r > 0.997 4). The limits of detection (LODs) of the method were in the range of 2.9 to 8.6 μg/kg. The recoveries were between 87.9% and 105.3% with relative standard deviations (RSDs) of 2.2%–8.6%. The proposed method has the advantages of simple operation and no need for organic solvent and can be extensively applied for determination of fluroquinolones in animal tissue samples.

In this work, a cyclodextrin and peptide ligand-assisted noncompetitive detection model was developed using chlorpyrifos (CPF) as typical target. The possibility of CPF encapsulated by β-cyclodextrin (β-CD) was first confirmed through the use of molecular modeling and UV and fluorescence spectroscopy. Then, bovine serum albumin (BSA)-β-CD conjugate, which was still able to include CPF, was synthesized and five positive peptide ligands specifically bound to the CPF:β-CD inclusion complexes rather other β-CD were screened from a commercialized phage-display liner dodecapeptide library. At last, a noncompetitive detection model was developed using BSA-β-CD conjugate and the most active peptide (Clone 8). The developed detection model could specially detect CPF, but not profenofos, dichlofenthion, or bromophos without the need for the modification and immobilization of the target small molecules, thereby providing an alternative method for the rapid detection of small molecules.

Chahayang rice is a special brand of rice produced in Heilongjiang. In order to protect this brand, there is a need to establish a method for the rapid identification of Chahayang rice. In this paper, near infrared spectra of rice from a test paddy field were scanned in the full wavenumber range, and the characteristic bands for Chahayang rice were screened. Qualitative and quantitative analysis of 233 rice samples from Chahayang and other areas at the characteristic band were performed and compared. The results showed that the main factors associated with the geographical origin of Chahayang rice exhibited absorption bands in the wavenumber range of 5 136–5 501 cm-1. The rate of correct identification of Chahayang rice with the qualitative analysis model established based on the main factors was 100%, while that with the model developed through partial least squares (PLS) regression was 95.83%.

The aim of this study was to develop a semiconductor gas sensor for the rapid and sensitive detection of L. monocytogenes by targeting 3-hydroxy-2-butanone, the characteristic metabolite of L. monocytogenes. The sensitive material that matches 3-hydroxy-2-butanone was synthesized by a hydrothermal method and used to fabricate the sensor. The structure and morphology of the material were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The response of the as-prepared sensor to 3-hydroxy-2-butanone calibration gases and its performance for the detection of L. monocytogenes in milk were analyzed. The results indicated that the sensor exhibited high response, quick response-recovery kinetics, and good repeatability to 3-hydroxy-2-butanone. Furthermore, the response showed a good linear relationship with the concentration of L. monocytogenes, and the linear regression equation was lg(S-1)=0.198 3lgC - 0.472 5 (R2 = 0.990 1). This method could be completed within a short time without extensive sample preparation. Accordingly, it has a great potential as a rapid method for the detection of L. monocytogenes in food samples.

This study aimed to develop a new hybrid method to detect and quantify adulterated peanut oil based on the compositions of total fatty acids and Sn-2 position fatty acids determined by gas chromatography (GC). Firstly, the information on total and Sn-2 position fatty acids was fused together by principal component analysis (PCA) to reduce the data dimension. Then, a least squares support vector machine (LS-SVM)-based model, whose parameters were optimized by particle swarm optimization (PSO), was established to discriminate between authentic and adulterated peanut oil with a 100% recognition rate. Besides, a partial least square model and a principal component regression model were constructed to predict the level of adulteration in the mixed oils. To validate the effectiveness of these methods, a set of samples was prepared by mixing peanut oil with corn oil. Experimental results showed that the LS-SVM method a higher prediction accuracy with a root-mean-square error and a correlation coefficient of 3.452 1% and 0.986 6, respectively, indicating that this method is a potentially valuable tool in the detection of adulterated oils.

A new rapid and high-throughput microbial chromogenic assay was developed to analyze antibiotic residues in animal-derived food samples. The positive samples were further confirmed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. Bacillus sterothermophilus was used as an indicator strain to produce a 96-well microplate for detecting a variety of antibiotics simultaneously. The results showed that the microbial assay was simple and cheap, and gave easy-to-interpret results. After extraction with phosphate buffer at pH 7.4, muscle samples were detected using a chromogenic assay system consisting of the reactant solution (150 μL), bacterial suspension (50 μL) with an initial optimal density (OD600 nm) of around 0.4, and the sample extract (100 μL). The limits of detection (LODs) of aminoglycosides, beta-lactam, macrolide, and tetracyclines antibiotics were 60, 20–40, 60–80, and 40–60 μg/kg, respectively, which reached the requirements for the determination of antibiotic residue levels in the country and abroad. Consistent results were obtained in examining antibiotic residue in 60 animal-derived food samples using the microbial chromogenic assay and HPLC-MS/MS, indicating that the proposed assay could be used to detect antibiotic residues in animal-derived food samples with reliable results.

A high performance liquid chromatography-ion trap-time of flight mass spectrometry method was used for rapid screening, confirmation and quantification of 24 alkaloids, saponins and organic acid in beverage. After centrifugation of samples at high speed and filtration through a 0.22 μm drainage membrane filter, the filtrate was separated on a C18 column (2.1 mm × 250 mm, 3.0 μm) using a binary solvent system composed of acetonitrile and water containing 0.1% of formic acid through gradient elution. The analysis was carried out both in the positive and negative ion modes. The results showed that good linear relationships were obtained in the range of 50–750 μg/L for all 24 compounds with correlation coefficients of higher than 0.995. The limits of detection (LOD) obtained at signal-to-background noise of 3 for all analytes were in the range of 8–20 μg/L. Average recoveries were between 63.0% and 126.6% at three spiked levels (70, 250 and 700 μg/L) with relative standard deviations (RSDs) of 4.11%–14.73%. Depending on the match of accurate mass number and retrieval in the self-built standard library, rapid screening was achieved and multistage characteristic fragments were also used for confirmation. The method, thanks to its rapidity, high efficiency, and good accuracy, could be used in the rapid screening and determination of multi-plant derived ingredients in beverage.

In this study, we analyzed elemental contents and stable isotope ratios of carbon (C) and nitrogen (N) in organic and non-organic wines from Helan mountain east region in Ningxia of China and then used the obtained data to distinguish between the two wines. Our results showed that there were significant differences in the contents of several metal elements including Na, Mg, K, Al and Cu between the organic and non-organic wines and that the δ13C ratios of ethyl alcohol and glycerol in the organic wine were much lower than those in the non-organic one, but the N stable isotope ratios were significantly higher than those in the non-organic one. Thus, C and N stable isotopes and the contents of selected metal elements could be used to effectively distinguish between organic and non-organic wines by principal component analysis. This method has a great potential to be applied for organic wine authentication and therefore can provide a technical support for the development of the wine industry in this region.

A near infrared (NIR) spectroscopic model for the quantitation of flour moisture was developed using partial least squares regression (PLSR). Infrared spectra of 130 randomly selected samples were used to establish PLSR models employing different spectral pretreatments combined with wavelength selection using genetic algorithm (GA). The correlation coefficient (R2), root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) of the optimized model were 0.977 7, 0.245 3 and 0.264, which were respectively higher, lower and lower than those of the unoptimized one. Thus tt is feasible to establish a quantitative model for estimating flour moisture by spectral data pretreatment and GA-based wavelength selection which had better accuracy and lower errors than the unoptimized one.

Microbial samples collected from a representative mutton slaughter and processing plant in Suzhou, Jiangsu province, China were detected. This study mainly focused on the processing of cooked products, including the contact surfaces of cooking workshop, the air in each processing workshop, raw meat before and after washing and cooked meat. The aim was to determine the distribution of contaminating microbiota during the industrial production of cooked meat products. Bacterial counts of all the air samples were lower than 10 CFU per plate, respectively, being in line with the air quality standards. However, the total colony number of cooked meat reached 3.23(lg(CFU/cm2)) due to cross-contamination with the seriously polluted contact surfaces of cooking workshop. The contaminating spoilage bacteria were identified to be mainly Bacillus, Staphylococcus saprophyticus, Proteobacterium, Chryseobacterium and Microbacterium based on a combination of morphology and 16S rDNA sequences. Subsequently, three dominant spoilage bacteria, Bacillus sp. M1, S. saprophyticus M7 and Bacillus sp. M9, were selected to evaluate their potential for cooked mutton spoilage by detecting sensory scores, pH value, total colony number, total volatile basic nitrogen value and yield factors of microbial metabolites. The results suggested that Bacillus sp. M1 displayed the strongest spoilage potential, followed by S. saprophyticus M7 and Bacillus sp. M9. This study may provide a theoretical basis for microbial pollution control of cooked mutton products.

An analytical method was developed for the determination of 21 pesticide residues in bamboo shoot using dispersive solid phase extraction clean-up combined with gas chromatography (GC). To optimize this method, we compared the effects of different adsorbents on the purification of bamboo shoot extract and clean-up and the?baseline?of electron capture detector (ECD). Bamboo shoot samples were extracted with acetonitrile, followed by clean-up by dispersive solid phase extraction with anhydrous MgSO4, Florisil, primary secondary amine (PSA), strong cation exchange (SCX) or Pesticarb and subsequent determination by GC-ECD. All the 21 pesticides could be completely separated with an excellent linear relationship. The limits of detection (LODs) and quantification (LOQs) for the 21 pesticides were in the range of 0.079–1.77 and 0.26–5.89 μg/kg, respectively. For all spiked samples, mean recoveries were 92.97% with relative standard deviations (RSDs, n = 3) of less than 6.07%. The presented method was successfully applied to analyze 230 samples from China’s main bamboo shoot-producing regions. Apart?from fenvalerate, all the pesticides were detected from the 230 samples. p,p’-DDE (33.48%), δ-BHC (26.52%) and cyhalothrin (26.09%) showed high detection rates. Buprofezin was detected in the highest concentration of 9 508.9 μg/kg, which showed the largest percentage increase (6.69%) compared to the maximum residue limit.

A method was established for the determination of 6 zeranols (α-zearalanol, β-zearalanol, α-zearalenol, β-zearalenol, zearalanone, and zearalenon) in foods by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with immunoaffinity column clean-up. Sample extraction was carried out with 80% (V/V) acetonitrile-water mixture followed by purification on an immunoaffinity column, which was eluted with 2 mL of acetonitrile, and the eluate was blown to dryness by nitrogen and redissolved with 0.5 mL of 50% (V/V) acetonitrile-water mixture. The target compounds were assayed by UPLC-MS/MS. The chromatographic separation was performed on an ACQUITY UPLC HSS T3 column by gradient elution using acetonitrile and water as mobile phase. The mass spectrometric acquisitions were carried out by means of multiple reaction monitoring (MRM) in the electrospray negative ionization mode. Good linearities (R2 > 0.992) were achieved for these 6 compounds over the concentration range of 0.1–100 μg/L. The limit of detection (LOD) of the method was 0.05 μg/kg, and the limit of quantification (LOQ) was 0.2 μg/kg. The mean recoveries of the 6 target compounds (spiked at three concentration levels) ranged from 73.0% to 119.1%, with relative standard deviations (RSDs) of not more than 10%. This method is suitable for the simultaneous determination of multiple zearalenonic mycotoxins in foods with simple pretreatment, high sensitivity, and good recovery.

Objective: The aim of this study was to establish a new method for the rapid and accurate quantification of walnut-derived ingredients and adulterated ingredients, mainly derived from soybean, in commercial walnut beverage using droplet digital polymerase chain reaction (ddPCR). Methods: This method was based on the ratio between the numbers of target gene copies per unit mass of walnut and soybean, which could represent the relationship between gene copy number and the mass of plant materials. The soybean lectin gene and the walnut Jugr2 gene were chosen as the target genes according to the commercial inspection standard SN/T 1961-2013. The specificity of the assay was evaluated by testing DNA from six different species using the species-specific primers and probes. The results showed that there was no cross-reaction among the target species and high sensitivity was observed. The ddPCR assay showed a limit of detection (LOD) for added soybean-derived ingredients in walnut protein drink was 0.5% with a relative error of 5.6%. The ratios of target gene copy numbers between soybean and walnut in pure samples of five different masses and between the two species in five mixtures with different proportions were determined three times, and the experimental data were fitted to a linear equation to calculate the ratio between gene copy numbers per unit mass soybean and walnut (Csoybean/Cwalnut ratio = 1.771 1). Furthermore, we applied this method to test 11 commercial brands of walnut beverage, and it turned out that walnut-derived ingredients were detected in all these samples and 6 of them were found to also contain soybean-derived ingredients, out of which 4 were adulterated with more than 10% soybean and the others contained as low as 0.2% soybean, which may be unintentionally incorporated during the production process. Conclusion: The ddPCR assay can provide a rapid and accurate quantitative method for the identification of adulterated walnut beverage.

This study aimed to establish a new accurate quantitative method to detect Staphylococcus aureus in yogurt using droplet digital PCR (ddPCR). Specific primers and probes targeting the nuc gene of Staphylococcus aureus were designed, and the PCR reaction system was optimized. The specificity and sensitivity of ddPCR for detecting the target gene were tested using the DNA extracted viable bacterial cells, and the quantitative results were analyzed. The ddPCR method could be useful to quantitatively detect S. aureus in yogurt with good specificity. The limit of detection (LOD) of the method was 3.3 × 101 CFU/g, and the quantitative deviation was +10.18%, which proved the feasibility of using ddPCR for absolute quantitation of S. aureus. It will provide a useful demonstration for standardized control systems of other food-contaminating bacteria and foodborne pathogenic bacteria.

The urea content in adulterated milk powder was rapidly determined by nonlinear chemical fingerprint method using a reaction system consisting of sulfuric acid, malonic acid, ceric ammonium sulfate, sodium bromate and sodium bromide. Firstly, urea was added at different levels to milk powder to obtain adulterated milk powder standard samples each weighing 1.00 g. The nonlinear chemical fingerprint was recorded for each milk powder standard sample, and a linear relationship between the induction time and the urea content was established. Then, the urea content in milk powder was calculated by the least square method. The results showed that urea contents within the range of 0–40.00 mg/g in milk powder and induction time values displayed a good linear relationship with correlation coefficients equal to 0.996 6 and 0.999 5. The recoveries were 95.48%–104.06%, the relative standard deviations (RSDs) were not greater than 1.82%, and the detection limits (LODs) for milk powder samples 1#, 2# and 3# were 3.3 × 10-4, 4.5 × 10-4 and 1.1 × 10-4 mg/g, respectively. The method developed has the advantages of good accuracy and simple operation. It is a practical and feasible method for determining the urea content in milk powder.

A large-area, highly-ordered Ag nanodot array was prepared by anodic aluminum oxide (AAO) template method. A monolayer of decanethiol was then assembled on the surface of the nanodot array for the rapid detection of benzo(a)pyrene (BaP). The Ag nanodots array was characterized by scanning electron microscopy (SEM), UV-visible spectroscopy, and rhodamine 6G probe. The results showed that the best Raman enhancement effect of surface enhanced Raman spectroscopy (SERS)-active substrate was achieved by 80 min pore broadening, with an enhancement factor of up to 1.6 × 106. Then, a layer of decanethiol molecules was modified on the surface of the substrate. The pre-concentration of BaP could be achieved by the hydrophobic interaction between decanethiol and BaP. Sensitive and reproducible detection of BaP could be realized. The detection limit (LOD) of BaP was 1.0 ng/mL, and the relative standard deviation (RSD) of characteristic Raman peak was 9.7%, which met the standard for a highly repeatable SERS substrate. This method has a great potential in the rapid detection of BaP.

This study analyzed and evaluated seven residual polychlorinated biphenyls (PCBs) in three commercial fish species in Ningbo, including large yellow croaker, ribbon fish and Scomberomorus commerson. We examined the characteristics of PCBs contaminants in different tissues of fish and conducted risk assessment for human health. The results showed that the residual concentrations of PCBs in three fish species were in the decreasing order of large yellow croaker (3.82 ± 1.20) μg/kg > ribbon fish (2.00 ± 1.32) μg/kg > S. commerson (1.36 ± 0.40) μg/kg. Among all the PCBs tested, the concentration of PCB52 in ribbon fish was the highest, which was (0.78 ± 0.07) μg/kg, while for large yellow croaker and Scomberomorus commerson, the most dominant PBC contaminants were PCB153, at levels of (0.33 ± 0.09) and (1.59 ± 0.10) μg/kg, respectively. For all three fish species, the average concentration of residual PCBs tested in different tissues followed the decreasing order of skin (3.87 μg/kg) > sexual gland (2.57 μg/kg) > liver (2.53 μg/kg) > gill (1.95 μg/kg) > muscle (1.57 μg/kg). However, according to the National Food Safety Standard GB 2762-2012, the residue levels of PCBs in three fish were all within an acceptable range.