Abstract:The effect of enzymatic protein hydrolysates with different degrees of hydrolysis (DHs) of the hazelnut from Changbai Mountain on the immune function in mice was evaluated in this study. Hazelnut protein hydrolysates with 6 different DHs (24.16%, 29.69%, 33.22%, 36.33%, 38.08%, and 39.57%) were prepared according to their hydrolysis time, and were orally (gavage) administered to the test mice groups at a dose of 1.00 g/kg body weight. Through immune organ index analysis and the spleen lymphocyte proliferation function, phagocytic activity of macrophages, cytokine levels in serum (IFN-γ and IL-4), and the activity of alkaline phosphatase in serum as indicators, the immunomodulatory effects of hazelnut protein hydrolysates in mice were studied on 10, 20, and 30 days after administration. The results demonstrated that the hazelnut protein hydrolysate with a DH of 33.22% significantly increased the thymus index of mice (p < 0.05). The hazelnut protein hydrolysates with DHs of 36.33%, 38.08%, and 39.57% also significantly increased the immune organ index, IFN-γ and AKP levels in serum, and enhanced the spleen lymphocyte proliferative activity and macrophage phagocytic activity (p < 0.05 or p < 0.01). In conclusion, hazelnut protein hydrolysates with DHs of 36.33%, 38.08%, and 39.57% could enhance the immune function in mice. This study provides an experimental basis for the development of peptide products with immune activity from hazelnut proteins.

Abstract:In this study, the influence of red cabbage anthocyanins (RCAs) in regulation of the blood lipid profile of atherosclerotic rabbits was studied. New Zealand white rabbits were divided into normal control group, model control group, low-, medium-, and high-dose anthocyanin groups, and positive control (simvastatin) group (n = 8). The normal control group was fed an ordinary diet and the other groups were fed high-fat diet. After six weeks, the rats of the low-, medium-, and high-dose anthocyanin groups were administered 30, 60, and 90 mg/(kg?d) anthocyanin by gavage, respectively; the positive control group received 5 mg/(kg?d) simvastatin; and the model group received 2 mL/(kg?d) physiological saline. Serum total cholesterol (TC), triglycerides (TGs), and low-density lipoprotein (LDL-C) were measured after 6 and 10 weeks. After 10 weeks, the rabbits were sacrificed, and the aorta was collected for pathomorphological observation. Results showed that RCA and simvastatin significantly reduced serum TC, TGs, and LDL-C content in the rabbits. Histological sections demonstrated that RCA could mitigate atherosclerotic plaque and other atherosclerotic damages, demonstrating its important, protective, and dose-dependent effects on atherosclerosis and hyperlipidemia.

Abstract:One quorum sensing (QS) strain was isolated from spoilage bacteria of Scophthalmus maximus and by using classical tests and 16S rRNA gene analysis, it was determined to be Aeromonas hydrophila. The changes in the activity of N-acyl-homoserine lactones (AHLs) during the growth stages of the strain and the effect of different culture conditions on the secretion of AHLs were studied by the punch method. The results indicated that the strain Ah-11 could induce Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136 to produce color. The activities of AHLs increased first and then decreased during the growth phase. The different carbon sources influenced the activity of AHLs in the following order: maltose> glucose> sucrose> fructose> lactose> xylose. The ability of Ah-11 to produce AHLs was reduced in weak acid and alkalescent environment; the optimum pH fat which Ah-11 could secrete AHLs was pH 8.0. Higher concentrations of NaCl would not only inhibit the growth of Ah-11 but also inhibit the activity of AHLs. The concentration of NaCl (0.5–1.0 g/100g) had a significant effect on the ability of Ah-11 to secrete AHLs. The optimal temperature at which the Ah-11 strain could produce AHLs was 28°C and relatively higher or lower temperatures could inhibit AHL secretion. Quorum sensing systems of Ah-11 were regulated by both the density of the bacteria and by environmental factors.

Abstract:Fatty acids (FAs) and normal corn starch (NCS) complexes prepared by the HCl/KOH method, were analyzed for in vitro digestibility in terms of the curve for degree of hydrolysis. Additionally, the crystal structure was analyzed using an X-ray diffractometer and a Fourier-transform infrared (FTIR) spectrometer. The results identified seven fatty acids that exhibited the strongest complexation capability with corn starch at the crystallization temperature of 60 ℃. FT-IR spectroscopy confirmed FA-NCS complexation. Except for linolenic acid, the optimal complexation ratio for the six remaining FAs to NCS was 10:1. The time to form inclusion complexes with corn starch varied between the FAs. With increasing chain length and degree of unsaturation, the complexation ability of the FAs with NCS decreased gradually and the content of slowly digestible starch increased, whereas the hydrolysis rate, relative digestion rate, and glycemic index decreased. After forming complexes with FAs, the crystal structure of NCS changed from A to VI, while the degree of crystallinity decreased gradually with increasing FA chain length and degree of unsaturation.

Abstract:L-isoleucine is one of the eight essential amino acids for humans and animals, and it plays a vital role in numerous life functions. α-Ketobutyrate is the key precursor of L-isoleucine, and acetohydroxy acid synthase (AHAS; encoded by ilvBN) is the key enzyme in L-isoleucine synthesis. Therefore, L-isoleucine production can be theoretically increased either by increasing the supply of α-ketobutyrate or ilvBN expression. Citramalate synthase, encoded by cimA, catalyzes the generation of α-ketobutyrate from pyruvate and acetyl-CoA. α-Ketobutyrate is a direct precursor of L-isoleucine; thus, increasing cimA expression increases the metabolic flux of L-isoleucine synthesis. In the present study, the promoter of the ilvBNC operon in the L-isoleucine-producing strain Corynebacterium glutamicum YILW was replaced by the potent tac promoter to construct a recombinant strain, C. glutamicum YILWPtac, which overexpresses ilvBNC. Shake flask fermentation experiments showed that L-isoleucine production and glucose (Yp/s) conversion in the recombinant strain were increased by 14.8% and 18.6%, respectively. To further increase L-isoleucine production and Yp/s, a construct containing the cimA gene under the control of a strong promoter was introduced into C. glutamicum YILWPtac to construct C. glutamicum YILWPtacpXMJ19cimA. Compared to the original strain, in C. glutamicum YILWPtacpXMJ19cimA, L-isoleucine production and Yp/s were increased by 14.5% and 42.4%, respectively. Thus, the findings of this study provide a basis for constructing new and improved amino acid-producing C. glutamicum strains.

Abstract:The gluten network structure of wheat flour-based products is weakened during cold storage owing to ice crystal migration and recrystallization, resulting in reduced quality. Xanthan gum is an excellent food additive, and its application in frozen dough has attracted increasing attention. The effects of xanthan gum on the rheological properties, water-holding capacity, solu bility, and the ultramicro network structure of gluten proteins were studied. The results showed that the water-holding capacity significantly increased when xanthan gum was added. When 0.25% (m/m) xanthan solution was mixed with gluten, the water-holding capacity reached 131.8%, which was 9.1% higher than that of the original gluten proteins. The solubility of gluten declined after the initial increase with the increasing amount of added xanthan gum. When the ratio of xanthan/gluten was 0.075%, the solubility of gluten was 4.08 mg/mL, 0.77 mg/mL higher than that of the original gluten. The addition of a certain amount of xanthan gum led to a decreased gluten elasticity and an increased viscosity (decreased storage modulus G', increased loss modulus G'', and loss tangent tan δ). The gluten network structure became more uniform with the addition of xanthan gum; when the xanthan/gluten ratio was 0.375%, the pore size of the gluten/xanthan complex system decreased from 100 μm to approximately 20 μm.

Abstract:Tryptophan (Trp) participates in the regulation of protein synthesis and plays very important roles in regulating appetite and maintaining health. The effect of Trp on amino acid transporters in weaned piglets was explored by determining growth performance, serum biochemical parameters, free amino acid content in the serum, tryptophan 2,3-dioxygenase (TDO) content in the liver, indoleamine 2,3-dioxygenase (IDO) content in the jejunum, and gene expression of amino acid transporters in weaned piglets. The results showed that addition of 0.2% Trp significantly increased the daily gain and daily feed intake, markedly elevated the levels of serum Trp and leucine, and dramatically decreased the levels of valine and isoleucine. The addition of 0.1% Trp and 0.2% Trp significantly increased TDO content in the liver and IDO content in the jejunum, respectively. The addition of 0.2% Trp markedly enhanced the gene expression of ATB0,+, 4F2hc, B0AT1, and ASCT2 in the jejunum (P < 0.05). In conclusion, Trp can promote the expression of amino acid transporter-related genes and ultimately promote the transport and uptake of amino acids, indicating that Trp can regulate and control the health of the body by upregulating the expression of amino acid transporters.

Abstract:The effect of Bacillus natto glycopeptide (BNGP) on the nuclear translocation of nuclear factor (NF)-κB p65 into the nucleus of RAW264.7 macrophages was studied using immunofluorescence; its effect on NF-κB p65 expression in the cytoplasm and nucleus was detected by western blot, while its effect on fluorescein isothiocyanate-lipopolysaccharide (LPS-FITC) binding to cell receptors was determined by flow cytometry. The results showed that the percentage of the cells with NF-κB p65 nuclear translocation in 62.5~500 μg/mL BNGP groups was significantly higher than that in the control group. High-dose BNGP (500 μg/mL) significantly reduced the percentage of cells with NF-κB p65 nuclear translocation induced by LPS and no significant changes were found between the low dose (≤ 250 μg/mL) BNGP and LPS groups. When macrophages were treated with 62.5~500 μg/mL BNGP alone, NF-κB p65 expression level increased in the nucleus and decreased in the cytoplasm, suggesting that BNGP promoted the translocation of NF-κB p65 from cytoplasm to nucleus. When macrophages were treated with 62.5~500 μg/mL BNGP and LPS, the expression level of NF-κB p65 increased in the cytoplasm and decreased in the nucleus, suggesting that BNGP inhibited the LPS-induced nuclear translocation of NF-κB p65 from the cytoplasm to the nucleus in RAW264.7 cells. BNGP also reduced the amount of LPS-FITC bound to macrophages at doses ranging from 62.5 to 500 μg/mL, where 500 μg/mL BNGP showed a significant effect, indicating that BNGP interferes with the binding of LPS-FITC to macrophages.

Abstract:In order to investigate the influence of pre-harvest calcium treatment on the hard-end Whangkeumbae (Pyrus pyrifolia.Nakai.) pear fruits, normal fruits and hard-end fruits were used as test materials. Some of the hard-end pear fruits were sprayed with CaCl2 solutions before harvest, and the fruit storage characteristics, gene expression level of PpEXPA2, and other indicators were determined. The results showed that during storage at 2 ℃, the firmness, adhesiveness, springiness, cohesiveness, and chewiness of the calyx-end area of normal fruit, CaCl2-treated fruit and hard-end fruit showed a downward trend after the initial increase. The firmness and chewiness in both stem end and calyx end areas of CaCl2-treated fruit were lower than those of hard-end fruit. The weight loss rate was highest in normal fruit, followed by in CaCl2-treated fruit. CaCl2 treatment reduced the rot rate of hard-end fruit and inhibited the respiration rate of the fruits. After 180 days of storage, the rot rate and respiration rate of CaCl2-treated fruit were decreased by 18.87% and 59.70%, respectively, compared with hard-end fruit. During the early stage of the postharvest period, the relative expression level of PpEXPA2 in hard-end fruit was significantly higher than those in normal fruit and CaCl2-treated fruit and was then decreased. The relative expression levels of PpEXPA2 in normal fruit and CaCl2-treated fruit gradually increased during the storage period. Pre-harvest CaCl2 treatment may inhibit the gene expression of PpEXPA2.

Abstract:A prokaryotic expression vector, pET28a-rhC I was constructed, with recombinant, human-like type I collagen peptide gene and transformed into Escherichia coli Rosetta (DE3) for inducible expression. The cDNA sequence of recombinant human-like collagen type I peptide was amplified by polymerase chain reaction (PCR) and cloned into the prokaryotic expression vector, pET28a. The recombinant plasmid was transformed into E. coli Rosetta (DE3) for IPTG-induced expression and gene expression conditions were optimized. The expressed products were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot. The expressed recombinant proteins were purified by nickel affinity chromatography. Additionally, in vitro antioxidant activity and cell proliferation assay were conducted on the purified proteins. The results showed that the molecular weight of the expressed recombinant protein induced by of E. coli Rosetta (DE3) was approximately 40 ku, consistent with the expected value. Nickel affinity chromatography produced a collagen peptide with relatively high purity, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical test revealed that the recombinant protein showed antioxidant activity. In addition, the methylthiazolydiphenyl-tetrazolium bromide (MTT) assay showed that the recombinant protein promoted the proliferation of mouse embryonic fibroblasts cells (3T3). These results indicate potential applications of this protein in industries such as food, cosmetics, and medicine.

Abstract:Six endophytic strains were isolated from the fruits of Zanthoxylum Bungeanum by grinding, and these included four strains of bacteria and two strains of fungi. The endophytic bacteria, Z2, was used as the research object in the present study, and its morphological, physiological, biochemical, and molecular biological characteristics were investigated. It was found that the strain Z2 was Gram-positive without spores and flagella, and was observed as a short rod of about 1.5~2.5 μm in length and 0.6~0.7 μm in width. According to the results on the physiological and biochemical characteristics, 16S rDNA gene sequence, and the phylogenetic tree, Z2 was identified as Brevibacterium frigoritolerans. During comparative analysis of the broth fermentated with Z2 and the broth without fermentation using high-performance liquid chromatography (HPLC), a new substance was found in the fermentation broth. This new substance was further purified by Sephadex LH-20 column chromatography and by semipreparative HPLC. Based on of the data from electrospray ionisation tandem mass spectrometry and nuclear magnetic resonance imaging, this substance was identified as L-tyrosine and its content was 12.90 mg/L in the fermented broth.

Abstract:Various properties including the angle of repose, activation index, contact angle, dispersibility, and polarized light property of different types of starch (corn starch, tapioca starch, and potato starch) were analyzed in this study. Additionally, the effects of different pH conditions and different concentrations of added octenyl succinic anhydride (OSA) and Al3+ were investigated. The results showed that the angles of repose of corn and tapioca starch presented an initial decrease, followed by an increase, with higher pH values and increasing concentrations of added OSA and Al3+. Variation of pH value showed an obvious effect on angle of repose in case of potato starch only. Modification caused the contact angles of different types of starch to increase to >90°, indicating a significant improvement in the hydrophobic property of all three kinds of starch. The activation index for both, tapioca and potato starch reached a value of 0.95. The results of the dispersibility test in liquid paraffin showed highest dispersibility for corn starch, followed by tapioca starch, whereas potato starch showed lowest dispersibility. However, the dispersibility of modified starch did not change significantly as compared to that of native starch. Finally, the properties of starch under polarized light of the same intensity showed that the birefringence of modified starch granules was weaker and the shadow areas were larger.

Abstract:To broaden the spectral response of nanoscale TiO2 and to enhance its visible-light photocatalytic antibacterial activity, in this study, chemical deposition of silver (Ag) and the doping of nonmetal elements nitrogen (N) and sulfur (S) was performed to prepare modified P25 antibacterial materials (Ag-P25, Ag-N-P25, and Ag-S-P25) with commercial TiO2 nanoparticles as the raw material. The antibacterial effects of these three P25 materials were studied against Escherichia coli under visible light. The study showed that all the three antibacterial materials had good inhibitory effects on E. coli growth. The antibacterial rate of the modified P25 materials increased with the extension of illumination time under visible light. The antibacterial effects of the three materials were in the following order: Ag-S-P25 > Ag-N-P25 > Ag-P25. When the materials were illuminated for 100 min, the antibacterial rate of Ag-S-P25, Ag-N-P25, and Ag-P25 reached 100%, which was 21% higher than that of pure P25 material. The results from scanning electron microscopy (SEM) and electrophoresis of the bacterial plasmid DNA showed that the E. coli cells were damaged by these three materials, which also caused the leakage of plasmid DNA and led to the death of bacteria. Further study and discussion on the E. coli inactivation mechanism of modified P25 materials can provide a theoretical and experimental foundation for the development of new antibacterial materials for food preservation.

Abstract:To determine the antibacterial mechanism of ginger mix-fried magnolia bark (GMB) against Escherichia coli and Staphylococcus aureus, the morphological structure of the bacterial cells, enzyme activity in the ion channels of cell membrane, and energy mechanism after treatment with GMB were studied. The results showed that the minimum inhibitory concentrations (MICs) of GMB against E. coli and S. aureus were 6.25 and 12.5 mg/mL, respectively. The absorbance values for extracellular alkaline phosphatase (AKP) and β-galactosidase in E. coli increased 1.78-fold and 4.24-fold, respectively. Four hours after GMB treatment, the conductivity of the culture medium changed significantly, and membrane Na+K+-ATPase activity increased from 0.42 to 1.74 mg prot/mL, which was 1.7 times higher than that of the negative control. There were vesicular or irregular projections on the cell surface of S. aureus, and the sorbitol dehydrogenase (SDH) activity, total adenosine triphosphate (ATP) activity, and soluble protein content decreased by 40%, 23.4%, and 17.9%, respectively, whereas AKP enzymatic activity and conductivity increased. These results suggested that GMB increased E. coli cell permeability by disrupting the cell wall and damaging membrane structure, which resulted in an outflow of intracellular material and a decreased amount of synthesized proteins, thereby inhibiting bacterial growth. GMB appeared to inhibit S. aureus by enhancing the cell wall permeability, reducing the activity of enzymes related to energy metabolism, and interfering with the normal metabolic activities.

Abstract:The changes in the content of polyphenols during electric field (EF)-assisted aging of brandy with amorphous oak were investigated in this study. To accelerate the physical and chemical reactions of brandy in amorphous oak and to shorten the maturation process, the aging process of brandy in amorphous oak enhanced by EF was studied, and the variations of polyphenol content over aging time were analyzed. The content of total phenols and tannins was determined by the Folin-Ciocalteu method; the content of condensed tannins was determined by vanillin-hydrochloric acid method and those of volatile phenols were determined by high-performance liquid chromatography (HPLC). The results showed that the content of total phenols and tannins of EF-treated oak samples was significantly higher than in untreated samples with the same aging period and volume. The content of total phenols in the EF-treated brandy sample aged with oak powder for 10 days was 10.03%, 18.41%, 5.03%, and 5.71% higher than in the control sample aged with oak powder, oak chips, oak cubes, and oak blocks, respectively. The content of total tannins in the EF-treated brandy sample aged with oak powder for 10 days was 23.62%, 14.04%, 9.70%, and 20.03% higher than in the control sample aged with oak powder, oak chips, oak cubes, and oak blocks, respectively. This study indicates that the extraction efficiency of polyphenol compounds from amorphous oaks can be enhanced by EF, thus improving the brandy quality.

Abstract:Peroxyl radicals were generated by the thermal decomposition of 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) under aerobic conditions in this study and served as a representative free radical derived from lipoxygenase-induced lipid peroxidation of polyunsaturated fatty acids. The effects of the peroxyl radical on the properties and secondary structure of selenium-enriched soy isolate protein (SPI) were investigated. With increasing concentrations of AAPH, the results of Fourier transform infrared spectroscopy showed that the ?-helix, β-turn, and random coil content increased, while the β-sheet content decreased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns indicated that the subunits of SPI accumulated at the top of the stacking gel; protein solubility and the free sulfhydryl content of SPI decreased. Surface hydrophobicity, emulsifying activity, and emulsifying stability of SPI increased initially, but later decreased; the wavelength of the maximum emission (λmax) in the intrinsic fluorescence spectrum was gradually blue-shifted, and fluorescence intensity first increased then decreased. The selenium-enriched soy isolate protein was superior to ordinary soy isolate protein in terms of structure, distribution of subunits, properties, and other test indicators, which may be related to the high selenium content in selenium-enriched soy isolate protein, indicating its stronger antioxidant activity.

Abstract:The modification of starch by the high hydrostatic pressure (HHP)-assisted esterification reaction was studied herein. Tapioca was selected as the raw material and the esterified tapioca samples were synthesized using HHP-assisted reactions with acetic anhydride at 300, 450, and 600 MPa. The physicochemical and structural properties were systematically studied via a polarized light microscope, Fourier transform infrared (FT-IR) spectrometer, viscometer, visible spectrophotometer, and others. The FT-IR spectra showed an absorbance peak attributable to the ester group at approximately 1700 cm-1 and no significant changes in the birefringence were observed with increasing pressure. This demonstrated that the crystal structure of the starch granules was markedly stabilized by the formed ester linkage, and no apparent ruptures occurred in starch granules even at the high-pressure treatment of 600 MPa. The HHP-assisted esterified tapioca starch showed reduced stability, enhanced acid resistance, and obvious aging resistance compared with the original tapioca. The esterified tapioca prepared at 450 MPa exhibited the largest difference (27.56 mPa?s) between cold and hot viscosities compared with those prepared at 300 and 600 MPa. The above results demonstrated that the modified starch has broad prospects for application in papermaking, textile, and chemical industries.

Abstract:To investigate the diversity of the endophytic bacterial communities, high-throughput sequencing technique was used to measure the sequence of 16S rDNA-V4 variable region of endophytic bacteria in maize. QIIME and Mothur software programs were employed to sort and calculate the number of sequences and operational taxonomic units (OTUs) for each sample. Thereafter, the abundance, distribution, and alpha diversity index of species and the differences of species abundance among the samples were analyzed. The number of effective sequences and OTUs for each sample was 96334/156; the rarefaction curves showed a sufficient sequencing depth, and the number of OTUs was close to saturation. The Chao1 and Shannon indices of sample YM were 156.0 and 1.211, respectively. The endophytic bacteria in maize belonged to the following six genera: Sphingomonas (37.78%), Halomonas (33.33%), Pseudomonas (13.33%), Shewanella (6.67%), Methylobacterium (4.44%), and Pedobacter (4.44%). The dominant species were Sphingomonas and Halomonas, and accounted for 37.78% and 33.33%, of the total bacteria identified, respectively. Illumina MiSeq high-throughput sequencing system provides a more accurate andscientific data resource for the study of endophytic bacteria in plants.

Abstract:Recently, increasing attention has been paid to the hazards of pyrethroid insecticide residues. Rapid detection techniques can provide technical support for monitoring the pyrethroid pesticide residues in agricultural products. Using o-aminophenol (OAP) as the functional monomer and 3-phenoxybenzoic acid (3-PBA) (the structural analog of type II-pyrethroid insecticides) as the template molecule, the electropolymerized molecularly imprinted membrane (MIM) was prepared for the detection of type II-pyrethroid insecticides; MIM was synthesized on the surface of glassy carbon electrode (GCE) by the method of cyclic voltammetry in this study. The prepared MIM was applied in the detection of type II-pyrethroid insecticides and responses to the insecticides were completed within five minutes. The changes in the peak current value showed a good linear correlation with deltamethrin, fenvalerate, fenpropathrin, and cyhalothrin within a certain concentration range; the corresponding correlation coefficients were 0.991, 0.992, 0.995, and 0.990, respectively; precisions were 2.20%, 2.80%, 2.50%, and 2.12%, respectively; and detection limits ranged from 0.01 mg/kg to 0.30 mg/kg. The system was used for measurements of spiked citrus samples such as tangerine, Gong orange, and Ponkan, and results showed high accuracy.

Abstract:Brewer’s spent grains (BSGs) were used as the raw material to conduct citric acid modifications. The raw and modified BSGs were characterized by Brunauer-Emmett-Teller (BET) surface area analysis and Fourier transform infrared spectroscopy (FTIR), and the changes in the performance of dynamic adsorption of single component Pb2+ and Zn2+ before and after the BSG modification were studied. Additionally, various factors of the fixed bed on the adsorption and separation of heavy metal ions Pb2+ and Zn2+ were investigated, providing a novel approach for the practical application of BSGs in the separation of Pb2+ and Zn2+ in wastewater. The test results showed that the mesopore/micropore ratio and specific surface area of citric acid-modified BSGs increased to some extent, and the number of carboxyl groups increased, demonstrating that citric acid modification was generally successful. In the Pb2+ and Zn2+ adsorption and separation system, the pH of wastewater and the height of the adsorption column had a relatively large impact on the selective adsorption and separation of Pb2+ and Zn2+ using modified BSGs, while the initial concentration ratio of the two components had a relatively small impact. The results showed that the modified BSG fixed bed could effectively separate lead and zinc ions in wastewater when the lead and zinc ion concentrations were 30 mg/L and 15 mg/L, respectively, pH was 4.5, flow rate was 6 mL/min, and the height of the adsorption column was 12 cm. After adsorption, the concentration of Pb2+ in the effluent was less than the 0.5 mg/L that is required by the national standard (GB), and the operation time for adsorption and separation was 8.67 h.

Abstract:This study investigated the influence of fermentation by different lactic acid bacteria on the sugar and polyphenol content of defatted rice bran. Semi-dry enzymatic hydrolysis was used to increase the fermentable sugar content in defatted rice bran. After being treated with semi-dry enzymatic hydrolysis and sterilization, the defatted rice brans were inoculated with Lactobacillus bulgaricus, Streptococcus lactis, L. plantarum, L. casei, and Leuconostoc mesenteroides, respectively. Changes in the viable count of lactic acid bacteria, and the content of total sugar, reducing sugar, soluble polyphenols, and insoluble polyphenols during the fermentation were studied. The results showed that semi-dry enzymatic hydrolysis increased the content of reducing sugar in defatted rice bran to 155.08 mg/g, almost six times higher than that of the untreated defatted rice bran. All five lactobacilli grew in the defatted rice bran, but significant differences were found among their growth rates after entering the logarithmic phase. Among the five lactobacilli, L. acidophilus exhibited the strongest sugar transformation capacity; after 72-hour fermentation by L. acidophilus, the content of total sugar and reduced sugar decreased by 31.33% and 60.76%, respectively. The highest content of soluble polyphenols (33% increase) was observed after 24-hour fermentation by L. acidophilus; after 72-hour fermentation, the insoluble polyphenol content decreased by 20.32%, significantly better than those of other four stains.

Abstract:To investigate the impact of storage temperature on active oxygen metabolism and cell wall degradation of eggplant fruits, “Shangxin” eggplant fruits were stored at 2 ℃, 12 ℃, and 20 ℃ for 12 days. Firmness, superoxide anion (O2-) production rate, peroxide (H2O2) content, and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), lipoxygenase (LOX), ascorbate peroxidase (APX), and glutathione reductase (GR), and pectin, cellulose, and lignin content were measured every two days. The results showed that at 2 ℃, over the storage period, SOD, POD, CAT, APX, and GR activities decreased continuously; the O2- production rate and H2O2 content increased; and LOX activity increased, which accelerated peroxidation of membrane lipids. At the same time, after storage for six days at 2 ℃, the eggplant fruits showed signs of lignification, with increased firmness. During the storage period, changes in the cell wall structure were closely related to the degradation of cell wall materials. At 12 ℃, fruit firmness decreased slowly and antioxidant enzyme activity declined gradually. At 20 ℃, fruit firmness decreased significantly, fruits rotted, the activity of cell wall-degrading enzymes increased, and cell wall degradation occurred. In conclusion, 12 ℃ appears to be an optimal temperature for short-term storage of eggplant fruits.

Abstract:In this study, the effects of UV-C treatment on mildew, decay, and the expression pattern of cell wall hydrolases and the pathogenesis-related genes of ‘Darselect’ strawberry fruit stored at 20 ℃ were studied. The results indicated that 4.2 kJ/m2 UV-C treatment effectively decreased the mildew and decay of strawberry fruit during storage, and significantly reduced the respiratory rate at the later stages of storage. The results of quantitative PCR analysis showed that UV-C treatment significantly inhibited the expression of three cell wall hydrolase genes, β-glucosidases (FaBG3), β-1, 3-glucanase (FaGlu), and polygalacturonase (FaPG), at the later stages of storage. Moreover, UV-C treatment delayed the expression peak of the polygalacturonase-inhibiting protein gene (FaPGIP) and enhanced the expression levels of phenylalanine ammonia-lyase gene (FaPAL). These results suggested that UV-C treatment of the strawberry fruit controlled decay by decreasing mildew and by regulating the expression levels of cell wall-hydrolases and the pathogenesis-related genes during storage.

Abstract:A pH-sensitive polymer (PMDMN) was synthesized from four types of acrylic monomers. Polymer PMDMN-Cu or PMDMN-Fe was obtained after PMDMN was attached to a metal chelating agent, and then chelated with Cu2+ or Fe3+ via a coordination bond. First, the infrared spectra, isoelectric point, and recovery rate of the polymer were determined. Second, the adsorption conditions of PMDMN-Cu and PMDMN-Fe on the crude papain, including pH, time, and NaCl concentration, were explored. Based on the measurement of enzyme activity recovery rate, the elution efficacies of imidazole, guanidine hydrochloride, and ethylenediaminetetraacetic acid and their combinations were evaluated. Finally, enzyme purity under optimal elution conditions was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that the isoelectric points before and after grafting of the metal ligand were 5.15 and 5.08, respectively; the recovery rate was higher than 95% after five adsorption-elution cycles. The optimum pH value for adsorption by PMDMN-Cu or PMDMN-Fe was 7.0, and PMDMN-Cu and PMDMN-Fe reached adsorption equilibrium at 120 and 210 min, respectively, with maximum adsorption capacities of 5.09 and 4.58 mg/g, respectively. The amount of adsorbed papain increased with increasing NaCl concentration to some extent. In all elution methods, the combination of 0.5 M imidazole with 1.0 M guanidine hydrochloride showed the best elution effect, with an elution rate close to 95% and without metal ligand leakage. The electrophoresis results revealed that both PMDMN-Cu and PMDMN-Fe largely improved the purity of papain, with purification folds of 4.29 and 4.48, respectively.

Abstract:To study the effect of treatment with an exogenous substance on the chilling tolerance in green bell pepper fruits, different concentrations of exogenous ceramide solutions (0, 200, and 400 μmol/L) were used to treat pepper fruits. The chilling index, relative electrical conductivity, contents of malondialdehyde (MDA), chlorophyll, vitamin C (Vc), and soluble proteins, and the activities of peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) of pepper fruit, during storage, were determined. The results showed that exogenous ceramide treatment could effectively inhibit chilling injury in pepper fruits stored at 4 ℃. Both 200 and 400 μmol/L exogenous ceramide treatments effectively inhibited the increase of chilling index, delayed the increase of relative electrical conductivity, suppressed the accumulation of MDA content, and maintained the integrity of the cell membrane. At the same time, exogenous ceramide treatment delayed the degradations of chlorophyll, Vc, and soluble proteins, and enhanced the activities of POD, CAT, and APX, thereby increasing the chilling tolerance of pepper fruits. Among all the treatments, optimal chilling tolerance of pepper fruits was found in 400 μmol/L of ceramide treatment.

Abstract:In the present study, the changes in the quality components of Jun jujube samples obtained from Southern Xinjiang after storage at different temperatures were analyzed by one-dimensional near infrared spectral analysis. Then, a two-dimensional correlation analysis of the collected infrared spectra was conducted using 2D-shige software. The numbers of automatically numbered peaks in the synchronous spectra of Jun jujube stored at 25 ℃, 1 ℃, 0 ℃, and -1 ℃ were six, five, four, and three, respectively. The strongest band detected in Jun jujube stored at room temperature (7,173 cm-1) suggested that the largest change in total acid content occurred at this temperature. The protein and vitamin content was largely unchanged after storage at 1 ℃. The strongest band detected in Jun jujube stored at 0 ℃ (at 7,081 cm-1) indicated that the largest change in total acid content occurred at this temperature. The three automatic peaks detected in Jun jujube stored at -1°C indicated that the total acid, total sugar, water content changed after storage at this temperature. The analysis results showed that the position and number of automatic peaks detected by two-dimensional correlation spectroscopy (2DCOS) in Jun jujube stored at different temperatures were different, indicating that the changes in the temperature-sensitive components of Jun jujube were different. Compared to Jun jujube stored at a normal temperature of 25 ℃, Jun jujube stored at 1 ℃, 0 ℃, and -1 ℃ showed significant cold storage effects. These results show that cold storage plays an important role in maintaining the quality of Jun jujube and that the best cold storage temperature for Jun jujube from Southern Xinjiang is 0 ℃.

Abstract:Chickpea protein was used as the raw material in this experiment, and a series of chickpea protein hydrolysates (CPHs) with different degrees of hydrolysis (DHs) were prepared by double-enzyme digestion. Using the CPHs as the substrate, descriptive sensory analysis and gas chromatography-mass spectrometry were employed to analyze and compare the flavor characteristics of flavor peptide products prepared from the model Maillard reaction system to identify the most suitable chickpea proteolytic system for the preparation of Maillard reaction peptides (MRPs). The results revealed significant differences in the sensory attributes and aroma components among MRPs prepared from CPHs with different DHs. Compared with other samples, the MRPs produced from CPHs with a DH range of 23.03~26.02% contained a large number of aroma compounds and showed an apparent meaty and umami taste with a long duration. Correlation analysis on the aroma substances, sensory evaluation data, and electronic nose data was conducted using partial least squares regression and the results further confirmed that the CPHs with a DH range of 23.03~26.02% is a desirable substrate for thermal reactions to produce MRPs.

Abstract:The effect of different microwave oven cooking methods on vitamin C (Vc), retention rate of flavor substance, and texture of white radish were studied in this experiment. After white radish samples were cooked in a water bath, an inverter microwave oven, a non-inverter microwave oven, and in a direct injection steam microwave oven, the Vc content, brittleness, and the retention rate of flavor substance were determined by ultraviolet spectrophotometry, texture profile analysis (TPA) by using a texture analyzer, and gas chromatography (GC), respectively. On the contrary, the morphologies of raw and processed white radish samples were examined using scanning electron microscope (SEM). Under the experimental conditions, the retention rates of flavor substances and Vc generally showed a downward trend along with the increase in temperature and extended heat-holding time, i.e., 65 ℃ > 75 ℃ > 85 ℃ > 95 ℃. Texture analysis showed that the brittleness values decreased along with the increase in temperature and extended heat-holding time. However, the brittleness values of some processed samples were higher than those of the corresponding raw ones. The results obtained showed that after cooking at 85 ℃ for 5 min, the moisture retention rates for water bath, inverter microwave oven, non-inverter microwave oven, and direct injection steam microwave oven were 92.76%, 90.87%, 90.31%, and 91.86%, respectively, and that microwave cooking caused food moisture loss more easily than cooking in a water bath. After cooking at 85 ℃ and/or 95 ℃ for about 5 min, the moisture retention rates were above 90.00% for all, and the Vc retention rates were higher than 60.00% for all, except for the sample cooked in the inverter microwave oven. Within suitable cooking temperatures and durations, the effect of using a non-inverter microwave and a direct injection steam microwave oven to cook white radishes were better than when the water bath and inverter microwave were used.

Abstract:Alkaline protease hydrolysate was isolated from codfish muscle, desalinated using DA201-C macroporous resin, and purified using SP Sephadex C-25 ion-exchange chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). The final product comprised of two bitter peptides at a relatively high concentration. Peptide structures were characterized by liquid chromatography/time-of-flight tandem mass spectrometry (LC-TOF-MS/MS), while bitterness intensity was evaluated by a combination of sensory evaluation and Q value. Their amino acid sequences were determined using an amino acid analyzer as HWPWMK (His-Trp-Pro-Trp-Met-Lys) and AVVLII (Ala-Val-Val-Leu-Ile-Ile). The amino acid composition of bitter fractions C7 and S9 was also analyzed; their Q values were determined as 6.03 and 6.79 kJ/mol, while their bitterness intensities were determined by sensory evaluation as 9 ± 0.8 and 8.2 ± 1.6, respectively. Q values of the purified bitter peptides S9purity and S10purity were 8.85 kJ/mol and 8.53 kJ/mol, while their bitterness intensities were 9.4 ± 0.8 and 8.9 ± 0.9, respectively. The bitter peptides isolated and purified from the codfish hydrolysate in this study are new members of the bitter peptide family and provide data for further study.

Abstract:Porcine longissimus muscles were used as the raw material to study changes in the molecular interactions of proteins, degree of oxidation of myofibrillar protein (the main components of pork), and changes in surface hydrophobicity and structure of myofibrillar proteins using a combination of ultra-high pressure and thermal treatment to determine their correlation. The results showed that hydrogen bonds, hydrophobic interactions, and disulfide bonds were the primary molecular forces maintaining the three-dimensional network structure of porcine proteins following a combination ultra-high pressure and thermal treatment. After combined treatment with ultra-high pressure and thermal process, the number of SH groups in myofibrillar proteins was significantly reduced (p < 0.01), whereas the number of S-S bonds, surface hydrophobicity, and carbonyl content in myofibrillar proteins significantly increased (p < 0.01). Secondary structure analyses confirmed that the content of helical structures decreased, while the content of disordered structures increased concomitantly.and Correlation analysis indicated a close relationship (p < 0.01) of the ultra-high pressure coupled with thermal treatment with the molecular interaction of proteins, carbonyl content, and protein structure. These findings will be useful for improving the understanding of changes in proteins after ultra-high pressure combined with thermal treatment, provide scientific guidance for the protein production process, and offer a theoretical basis for developing new meat products.

Abstract:Currently, the low number of studies and the lack of a systematic theoretical system on Sichuan dongcai have become the main factors restricting its industrial development. In order to understand variation in the quality and appearance of the Sichuan dongcai, indicators of quality and appearance were monitored during the salting process. Nitrite, crude protein, and amino acid content were determined according to national standard methods. The nitrite content reduced by more than 97% to only 1~2 mg/kg dry matter; crude protein and amino acid content was reduced by 78% and 81%, respectively, whereas the proportion of the essential amino acids increased from 23% to 34%. Color changes in different portions of the Sichuan dongcai were determined by using a colorimeter. It was found that the L* and b* values decreased while a* value increased in three portions of the Sichuan dongcai, respectively. Colors in different parts were similar in the post-salting period. Micro-morphology was observed by scanning electron microscopy. The structure of the sample tissue gradually blurred and was damaged. In conclusion, it was observed that the quality and appearance of the Sichuan dongcai was maintained in a stable state after 32 months of salting, and extending the salting time has little effect on it.

Abstract:Mushroom (Lentinus edodes) caps and stems were powdered using four different grinding methods (ordinary grinding, shear-ultrafine grinding, jet-ultrafine grinding, and nano-ultrafine grinding) and added to bread dough. The effects of the powders on dough fermentation characteristics and bread quality were analyzed. The results indicated that powdered mushroom increased the hardness of dough in a dose-dependent manner, where the increase was higher with powdered mushroom stems as compared to caps. Adhesiveness of the dough decreased with the amount of mushroom powder added; at 4.0% the dough was relatively hard with relatively poor viscoelasticity when compared with the control. The results showed that addition of <1% mushroom cap powder obtained by nano-ultrafine grinding, resulted in good quality dough, with relatively low hardness as well as relatively high viscosity and gas production after fermentation for 100 min. On the other hand, the results for bread quality with <1% mushroom cap powder obtained by jet-ultrafine and nano-ultrafine grinding were similar to those with control dough. The bread made with powdered mushroom stem obtained by nano-ultrafine grinding showed moderate brightness, white color, relatively good elasticity and resilience, as well as low hardness and chewiness.

Abstract:Based on the UV spectra analysis of ethanol-water system, the combination of UV spectrophotometry and 1H-NMR spectroscopy was used to contrast samples of the ethanol-water system and the freshly brewed Chinese rice wine before and after ultra-high pressure treatment. The results of these analysis were used to discuss the effect of ultra-high pressure treatment on the association of alcohol and water in new brewed Chinese rice wine. The UV spectroscopy data showed that ultra-high pressure treatment made the ethanol-water system strengthen the association between the ethanol and water molecules. The absorption peak value showed the most obvious changes at 300 MPa for 30 min. Upon combining the data of the NMR spectra, it was seen that the hydroxyl proton displacement δO-H of both the alcohol-water system and new brewed Chinese rice wine increased after ultra-high pressure treatment and moved to a lower field. At the same time, the δO-H of fresh brewed Chinese rice wine was closed one year after treatment. The results obtained in this study show that ultra-high pressure treatment had certain reinforcing effects on the alcohol-water association in Chinese rice wine, and was conducive to the aging of Chinese rice wine.

Abstract:To increase the comprehensive utilization of fresh-water fish byproducts and improve the nutritional value of surimi products, a calcium-rich silver carp surimi gel was prepared. Then, the effects of adding ground fishbone on the gel properties of silver carp surimi were investigated, and the nutrients in ground fishbone and silver carp surimi gel were analyzed. Single-factor experiments and sensory evaluations were used to determine the most suitable amount of ground fishbone to add, using gel strength, whiteness, and water-holding capacity (WHC) as the indexes of surimi quality. The effects of ground fishbone on the gelling of surimi were studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy. The results showed that 3% (mass percentage) added ground fishbone was suitable for increasing surimi gel strength and preparing a nutritional surimi gel. The strength of this prepared nutritional silver carp surimi gel reached 282.44 g/cm, whereas common surimi without added ground fishbone only reached 239.89 g/cm. The calcium and phosphorus contents were 1697.69 μg/g and 1278.16 μg/g, respectively, which was 4.6 times and 2.2 times higher than that in common surimi, respectively. The ratio of calcium to phosphorus was 1.33:1, which aids in the absorption of calcium and phosphorus. Moreover, the ratios of essential amino acids to total amino acids (EAA/TAA) and essential amino acids to nonessential amino acids (EAA/NEAA) were in accord with the recommendations of the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO). Therefore, this calcium-rich nutritional silver carp surimi can be used as a potential source of high quality proteins for human consumption.

Abstract:Summit cherry fruits were evaluated via gas chromatography-mass spectrometry (GC-MS), electronic nose, and sensory evaluation, as well as quality indices were measured for changes in content of volatile components within five days of shelf life. After initial storage at 13 ℃ for 12 h, the samples were stored at 13 ℃, 20 ℃, and at 20 ℃. The results from electronic nose evaluation showed that linear discriminant analysis (LDA) and principle component analysis (PCA) methods effectively distinguished between samples with different shelf-life durations. The results from GC-MS peak area normalization showed that the total peak areas of the three treatment groups decreased during storage, with differences between treatment groups, in the types of volatile compounds present. The main volatile compounds were aldehydes and alcohols, which was consistent with the results of electronic nose. On day four, a large amount of ethanol was detected in the 20 ℃ group, while the lowest ethanol content was found in 13 ℃ group. The results showed that the highest quality was observed in the 13 ℃ group on the third day of storage, indicating that temperature changes could be one of the main causes for the decline in quality. The results from GC-MS combined with electronic nose were largely consistent with the changes observed in the internal quality indices of cherry and the results of sensory evaluation. Therefore, it is feasible to combine these two techniques to evaluate the aroma quality of cherry during storage.

Abstract:To observe the changes in the quality of green pepper during Chinese cooking and food delivery processes and to determine the optimal delivery time, variations of green pepper quality before and after cooking as well as after 1, 15, 30, and 45 min of simulated delivery were studied. Green pepper was used as the raw material and the procedure to prepare a Chinese dish, “Hupi–pepper”, was the cooking method. The results showed that compared with the fresh sample, the cooked sample did not show significant changes on Vc content after 1 min of cooking, while the total phenolic content and antioxidant ability significantly increased. Good sensory and nutritional quality could be maintained after the sample was allowed to stand for 15 min. The sensory score was still higher than 3 points after the sample was allowed to stand for 45 min, and the overall sensory quality was acceptable. However, the nutritional quality decreased to some extent. After the sample was allowed to stand for 45 min, the sensory score was less than 3 points, the sensory quality was not acceptable, and the nutrition quality did not change significantly compared to that of the 30-min sample. Therefore, it was found that if the dish was consumed immediately after cooking, there was no significant loss of Vc content in green pepper, and total phenolic content and antioxidant activity were significantly increased, thus, favoring the nutrient intakes. A delivery within 30 min can ensure a relatively good sensory quality of green pepper and a high level of nutrients can be maintained. Therefore, it is recommended that the delivery time for the dishes with green pepper as the raw material should not be longer than 30 min.

Abstract:To establish a sensory evaluation system for pressed fresh rice noodles, the related indicators were screened according to GB/T 16861~1997. Based on the two-element comparison method, index weight was calculated and the score of the indicators was assigned. Thereafter, the Quantitative Description Analysis and the Hierarchical Cluster Analysis were combined to classify the indicators and describe their classification. Last, these factors were unified to form the rice vermicelli sensory evaluation system. The first grade indices included odor, appearance of the structure, texture, and taste. The second grade indices for the appearance of the structure included color, luster, structural integrity, and homogeneity; the second grade indices for texture included viscosity, hardness, and chewiness. Each index had 3 to 4 levels, and the different levels had a different description of characteristics and scores. Compared to the previous studies on rice noodle sensory evaluation systems, the indicators of the system in this study were comprehensive, the score distribution was reasonable, and the index grading and description of classification was exhaustive. Correlation analysis between the sensory evaluation of rice noodles and gelatinization and texture characteristics showed that the instrument measuring the indices demonstrated a good prediction of the sensory score.

Abstract:Fruit characteristics and nutritional components were comprehensively determined for three Xinjiang paddan almond samples (Shuangguo, Shuangren, and Zhipi) in this study. Atomic absorption spectrophotometry was used to determine the content of trace elements and major elements; a method described by the Chinese Pharmacopeia was used to measure amygdalin content; the nutritional value of proteins was evaluated as the score of the ratio coefficient of amino acid; gas chromatography mass spectrometry was used to measure the components and content of fatty acids. The results indicated that among the three Xinjiang paddan almond samples, the highest proportion of the edible part and highest content of amygdalin were found in Zhipi; Shuangren showed the highest content of total sugar and had a sweet taste. A full range of trace elements and major elements were found in three Xinjiang paddan almond samples, with the content in the following order: K > Na > Mg > Ca > Fe > Mn > Zn > Cu. There were a full range of amino acids with high content; the content of essential amino acids was relatively high, and the average content of amino acids for medical purposes accounted for 70.33% of the total amino acids. The score of ratio coefficient was62.786–66.738, which was close to the Food and Agriculture Organization of the United Nations and the World Health Organization requirement. The highest fat content (51.23%) was found in Zhipi. The average content of unsaturated fatty acid was relatively high (88.850%); oleic acid showed the highest content, followed by linoleic acid. Additional studies should examine Xinjiang paddan almond to promote its development and utilization because of its high nutritional value, sweet taste, high-quality proteins and oils, and potential medicinal value.

Abstract:Using GC-MS and a pulsed flame photometric detector (PFPD), 65 aroma compounds were identified and quantified in Colla Corii Asini (CCA) samples. The main volatile components of the CCAs were aldehydes, pyrazines, ketones, and sulfur compounds. Using GC-O and aroma extract dilution analysis (AEDA), 23 aroma-active compounds were detected. Based on the flavor dilution (FD) factor, the most powerful aroma-active compounds identified in the extracts were S-methyl thioacetate (sulfurous/burnt), 2,6-dimethylpyrazine (roasted nut), and 2-ethyl-3,6-dimethylpyrazine (roast). Principal components analysis (PCA) and correlation analysis were performed on the 23 aroma-active compounds. The principal components scores demonstrated significantly different patterns for five CCAs. Moreover, correlation coefficients (Pearson's r) among the five CCAs were very low and the largest correlation coefficient was 0.5285 obtained between Dong-E and Zhangjiachuan CCAs. It was concluded that GC-MS/GC-O can provide an effective and reliable tool for the analysis and characterization of the aroma components in CCA. Although it is rarely considered, aroma was demonstrated to be an important aspect of CCA quality. Chemometric analysis of the patterns of the 23 aroma-active compounds showed potential for quality evaluation and identification of CCAs from different habitats.

Abstract:Ferroferric oxide (Fe3O4) nanoparticles, chitosan (Chit), and graphene (GR) composite films and Nafion (NF) solution were used to modify the glassy carbon electrode (GCE) in order to prepare an acetylcholinesterase (AChE) amperometric biosensor (NF-AChE/Chit-Fe3O4/GR/GCE) for the detection of chlorpyrifos pesticide. This modified electrode combined the unique absorbability and biocompatibility of Fe3O4 nanoparticles, the excellent adhesiveness of chitosan, and the large specific surface area and excellent electron transport properties of graphene nanomaterials for providing a good binding interface for AChE. The results of cyclic voltammetry, alternating current (AC) impedance spectroscopy, and squarewave voltammetry showed that the electrochemical properties of the newly modified electrode were greatly improved. Under optimum conditions, the results from squarewave voltammetry revealed that the inhibition rates on AChE activity had a good linear relationship with chlorpyrifos concentrations in the range from 0.05 μg/L to 4.5 μg/L; the linear correlation coefficient was 0.997 and the detection limit was 0.02 μg/L (S/N = 3). Finally, this proposed biosensor was applied to determine the chlorpyrifos content in vegetable samples, and it was found that it showed excellent reproducibility and accuracy.

Abstract:A method for simultaneously measuring the content of inorganic elements in edible Zanthoxylum bungeanum seed oil (EZBSO) was established. After the EZBSO sample was dissolved in kerosene, 22 elements (Be, B, Na, Mg, P, K, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Sb, Hg, and Pb) were determined using inductively coupled plasma mass spectrometry (ICP-MS). The signal fluctuations caused by direct injection of organic solvent were eliminated by optimizing the plasma radio frequency power, carrier gas flow rate, sample uptake rate, and other operating parameters. Octopole reaction system (ORS) and internal standard method were used to eliminate the mass spectrometry interference and matrix effect, respectively. The results indicated that the detection limits for the 22 elements were in the range of 0.012~16.25 ng/g, relative standard deviations (RSDs) ranged from 1.28% to 4.16%, and recoveries ranged from 90.00% to 110.00%; the method was accurate and reliable. The element P showed the highest concentration in the EZBSO, followed by the element K. The method can be applied for the quality control and nutritional evaluation of EZBSO.

Abstract:To investigate the prevalence of Staphylococcus aureus and drug resistance at pig farms and during slaughter and processing, 507 pork and environmental samples were collected from farms, slaughter and processing, and markets. A total of 136 Staphylococcus aureus strains were identified according to the GB.4789.10-2010. All isolates were tested for antimicrobial susceptibility by the disk diffusion and E-test methods. The presence of genes conferring resistances to tetracyclines, macrolides, and lincosamides as well as the mecA and mecC (mecALGA251) genes carried by methicillin-resistant S. aureus (MRSA) strains in the isolates was examined by polymerase chain reaction (PCR). The results showed that the S. aureus infection rate of fresh pork from slaughterhouses was (44.11%, 60/136), and this value differed significantly from the rates at other sources (P < 0.05). The resistance rates to penicillin, tetracycline, and clindamycin, which are used to treat S. aureus infection, were (92.64%, 126/136), (56.62%, 77/136), and (50.00%, 68/136), respectively. The multidrug resistance rate was 56.62% (77/136), and the main resistance profiles of S. aureus strains were CIP/P/CN/TE/CLR/SXT/DA, P/CLR/DA, and CIP/P/TE/CLR/C/SXT/RD/DA. The drug-resistance genes carried by S. aureus stains posed a serious problem, and gene with the highest detection rate was the tetracycline-resistant gene tetK (90.44%). This study provides a theoretical basis for controlling the spread of multi-resistant strains of S. aureus in the food chain.

Abstract:To achieve the rapid detection of the common contaminating bacteria C. muytjensii in milk powder, specific probes and primers were designed based on the cgcA gene. The reaction system and reaction conditions for the detection of C. muytjensii were developed using quantitative real-time polymerase chain reaction (PCR) assay. Additionally, the specificity, sensitivity, and reproducibility of this method were evaluated, and the method was applied for the detection of artificially contaminated samples. The results showed that the specificity of real-time PCR assay was 100%; the sensitivity results revealed a detection limit of 440 cfu/mL for C. muytjensii. The reproducibility test results showed that the intra-assay coefficient of variations (CVs) ranged from 0.48% to 0.69%, while inter-assay CVs ranged from 0.69% to 0.73%. For the artificially contaminated samples, a positive result was obtained after 6 h of enrichment. The established real-time PCR assay exhibited good specificity, high sensitivity, and high reproducibility, and has promising potential to be a novel method for the rapid detection of C. muytjensii in food as well as a good value in research and application.

Abstract:The migration of mineral oil saturated hydrocarbons (MOSH) from food packaging paper into the food simulant Tenax was studied and the migration behavior of MOSH was explored for different types of food packaging paper and at different temperatures (25 ℃, 40 ℃, and 100 ℃). The threshold of toxicological concerns (TTC) was introduced to assess the safety of MOSH. The results showed that the thickness and grammage of the food packaging paper was important for the migration of MOSH at a specific temperature, and a smaller thickness and lower grammage led to a greater MOSH migration rate. Under certain conditions, a higher temperature resulted in a shorter time to reach the migration equilibrium for MOSH (100 ℃: 100 min; 25 ℃: 8 days) and a greater migration rate (100 ℃, 24.81% and 25 ℃, 7.82%). The amount of migrated MOSH of all testing packaging paper samples at equilibrium were beyond the migration limit (0.6 mg/kg) specified by the Joint FAO/WHO Expert Committee on Food Additives. Most MOSH is prone to migration had chains of C16~C18 or C23~C26, and they belonged to the low- and medium-viscosity mineral oils that are easily accumulated in the human body. The TTC results showed that migrating MOSH were classified as Cramer Class I. The estimated daily intakes of MOSH from four types of food packaging paper into Tenax were markedly higher than the corresponding TTC threshold (1.8 mg/person?day), which requires further analysis.

Abstract:To detect the volatile aroma components in the black teas from Luokeng Guangdong and determine the main aroma components, headspace solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were used. The aromatic compounds in teas that were produced in different areas of Luokeng, including Luxi wild black tea, Huajiaoyan wild black tea, Shangkeng wild black tea, Shangxie wild black tea, Jianggong wild black tea, Yulan black tea, and Banshanyuan black tea were determined. A total of 66 aroma compounds were identified in Luokeng Guangdong wild black tea, including alcohols, esters, aldehydes, ketones, hydrocarbons, and others. Alcohols and esters were the dominant aroma substances. From the 66 aroma compounds, 6 principal components were extracted using an SPSS software program, and the total contribution of the first five principal components was 97.8%; thus these components reflected the aroma characteristics of Luokeng black tea. The results of a cluster analysis showed that the seven black tea samples from different regions of Luokeng could be divided into two clusters: one cluster with an obvious almond aroma character, and another cluster with the typical sweet aroma of black tea. This study, based on multivariate statistical analysis, provides a new method for the evaluation of black tea aroma quality.

Abstract:The aim of this study was to establish a rapid, sensitive method for detecting enterohemorrhagic Escherichia coli O157 in foods. To establish a real-time fluorescence single primer isothermal amplification (real-time fluorescence SPIA) method for the detection of Escherichia coli O157, an RNA/DNA primer and chain terminator were designed based on the sequence of the rfbE gene of Escherichia coli O157, and the reaction conditions, such as primer concentration, Mg2+ concentration, and temperature, were optimized. The specificity, sensitivity, and detection limit for artificial contamination were determined. Under optimal conditions, a sample measurement could be completed within 55 min. No other bacteria besides E. coli O157 showed a specific fluorescent amplification curve. The sensitivity of the real-time fluorescence SPIA method for the detection of E. coli O157 was 2.0 CFU/mL, and the detection limit for an artificially contaminated pork sample was 4.0 CFU/g. The advantages of this real-time fluorescence SPIA assay include short detection time, high sensitivity, high specificity, and convenience. This study establishes a technology platform for the detection of food-borne pathogens.

Abstract:The gonad of steamed Chinese mitten crab (Eriocheir sinensis) is popular among Chinese population, owing to its delicious taste and savory flavor. To explore the unique aroma composition, the volatiles in the gonad of steamed Chinese mitten crab were studied by gas chromatography/mass spectrometry-olfactometry (GC/MS-O) combined with monolithic material sorptive extraction (MMSE). Thirty seven odorants were detected from the gonads of steamed males and females of E. sinensis by two GC-O methods: detection frequency methods and time-intensity methods. Among them, 23 and 34 compounds were detected in the gonads of steamed female and male crab samples, respectively; 20 compounds were commonly found in both types of crab samples. Aldehydes were the main contributors to the typical aroma of the gonad of steamed Chinese mitten crab; (E,Z)-2,6-nonadienal was the most important odorant compound. Owing to its high content, trimethylamine was also an important odorant compound in the steamed Chinese mitten crab with a relatively high detection frequency and odor intensity in the GC-O study.

Abstract:A method to simultaneously detect all-trans-Lutein, all-trans-β-cryptoxanthin and their stereoisomers was developed using C30-column, high-performance liquid chromatography, diode array (C30-HPLC-DAD) technique. The structures of isolated compounds were elucidated by atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) and ultraviolet/visible (UV/Vis) spectroscopy. The optimal chromatographic condition was as follows: mobile phase A: 1.5% ammonium acetate:water:methyl tert-butyl ether (MTBE)-MeOH (5:25:70, V/V/V), mobile phase B: 1.5% ammonium acetate:water:MTBE-MeOH (5:85:10, V/V/V); flow rate: 0.6 mL/min; elution time: 24 min; injection volume: 20 μL; column temperature: 25 ℃. Using this novel method, 15-cis-lutein, 13/13′-cis-lutein, 9-cis-lutein, 9′-cis-lutein, 15-cis-β-cryptoxanthin, 13- and 13′-cis-β-cryptoxanthin, 9-cis-β-cryptoxanthin and 9′-cis-β-cryptoxanthin were successfully separated from the mixture. The peak areas of all-trans lutein and all-trans β-cryptoxanthin showed a good linear relationship with their injection volumes in the range of 2 to 150 ng and 5 to 250 ng, respectively. The proposed method accurately and rapidly separated all-trans lutein, all-trans β-cryptoxanthin, and their cis-isomers simultaneously. This method has potential applications in qualitative and quantitative analysis of all-trans lutein, all-trans β-cryptoxanthin, and their stereoisomers in fruits and vegetables.

Abstract:Paclobutrazol is a common growth retardant used in vegetable cultivation. In order to understand the risk associated with dietary intake of paclobutrazol residue in vegetables, a supervised residue trial as well as monitoring of the market for potato, tomato, and eggplant was conducted. Chronic risk assessment and acute risk assessment techniques for paclobutrazol residue in vegetables were developed based on the above experimental data, and the recommended maximum residue limit (MRL) for paclobutrazol in vegetables was proposed. The assessment results showed that the national estimated daily intake (NEDI) values of paclobutrazol in vegetables was in the range of 0.040~0.21 μg/(kg bw?d) for all groups of Chinese residents, accounting only for 0.04%~0.21% of the acceptable daily intake (ADI). The national estimated short-term daily intake (NESTI) was between 0.070~0.95 μg/(kg bw?d), accounting only for 0.07%~0.95% of the acute reference dose (ARfD). The assessment result for the supervised trials was consistent with the results from market monitoring. The chronic dietary intake of paclobutrazol residue in vegetables was very low for all groups of Chinese residents. Despite the variation between the different groups of people and different types of vegetables, the acute risk levels of paclobutrazol residue in vegetables was very low and within an acceptable range. The chronic and acute risk levels were both within an acceptable limit. The recommended paclobutrazol MRL in vegetables was 0.5 mg/kg, which was 12.5~50 times as much as the paclobutrazol exposure levels in all groups of Chinese residents.

Abstract:Objective: The aim was to develop a rapid, simple, and sensitive LAMP method for the detection of Gluconobacter to be used in the yogurt industry. Method: Gluconobacter oxydans was selected as the type culture strain. Two pairs of LAMP primers targeting the 16S rRNA（X73820）housekeeping gene of Gluconobacter available in GenBank were designed. Concentrations of the primers and Mg2+ and the temperature of the LAMP were optimized, and a rapid, sensitive LAMP assay for Gluconobacter detection was established. Sensitivity of the assay was evaluated and compared with the PCR assay. Results: It was found that the LAMP primers showed high specificity and the LAMP product sizes, after restriction enzyme digestion, were consistent with the theoretical fragment sizes. The sensitivity of the LAMP assay for Gluconobacter was 7.5 × 101 CFU/mL. The LAMP assay was found to be 10-fold more sensitive than the traditional PCR assay. The LAMP detection limit was 7.5 × 102 CFU/mL for artificial contaminated yogurt. Conclusion: LAMP amplification established in this study provides a rapid,highly specific and sensitive method for Gluconobacter detection. The LAMP method is valuable for its application and exploitation in food industries.