Abstract:MCF-7 (human breast adenocarcinoma cell line) cells were cultured in roller bottles to investigate the apoptosis-inducing effects of porcine cartilage polysaccharide in terms of formation of large cell aggregates. Protein expression before and after apoptosis were explored. The cell apoptotic characteristics were observed by laser scanning confocal microscopy (LSCM) after Hoechst 33342/propidium iodide (PI) staining; apoptosis was detected by Annexin V-fluorescein isothiocyanate (FITC)/PI; and changes in cell cycle were analyzed by flow cytometry (FCM). Total proteins of MCF-7 were extracted and differentially expressed proteins were analyzed by two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF). The results showed that the typical apoptotic characteristics of MCF-7 cells were observed after exposure to porcine cartilage polysaccharide, and FCM results showed apoptotic rates of 20.23% and 44.7% after 24- and 48-h exposure, respectively. Additionally, it was found that the cell cycle of MCF-7 cells was arrested in S phase. Moreover, two differentially expressed proteins were identified: actin and an antioxidant protein, PRDX6.

Abstract:The in vitro effects of unsaturated fatty acids of rice bran oil (RBO-UFA) on HepG2 cells were examined by soft agar colony formation and transwell migration assays. Changes in the expression of the apoptosis-related factor, NF-κB, before and after RBO-UFA treatment were analyzed by western blot assay. Hoechst staining indicated that the number of HepG2 cells after RBO-UFA treatment was significantly decreased and the cytoplasm and nuclear chromatin were condensed. The soft agar colony formation assay showed that the HepG2 colonies were markedly reduced after RBO-UFA treatment and no colonies appeared. The migration assay indicated that the inhibition rates of linolenic acid and linoleic acid on the migration ability of HepG2 cells were up to 47.45 ± 4.60% and 41.61±4.08%, respectively, followed by that of rice bran oil (32.85 ± 3.24%) and that of oleic acid (25.55 ± 2.56%) (P < 0.05). The western blot results showed that NF-κB expression levels in total proteins from RBO-UFA treated groups were significantly lower than that of the normal control group. Compared with the control group, the relative expression levels of NF-κB in HepG2 cells treated with rice bran oil, oleic acid, linoleic acid, and linolenic acid were reduced by 0.46 ± 0.017, 0.058 ± 0.018, 0.25 ± 0.005, and 0.47 ± 0.011, respectively. On the other hand, compared with the control group, NF-κB expression in the RBO-UFA treated groups in the nuclear protein fraction was higher than that in the normal control group. The relative expression levels of NF-κB in HepG2 cells treated with rice bran oil, oleic acid, linoleic acid and linolenic acid were increased by 0.59 ± 0.036, 0.053 ± 0.040, 0.28 ± 0.043, and 0.59 ± 0.007 (P < 0.05), respectively. In summary, RBO-UPA treatment presented an inhibitory effect on the migration and clonogenicity of HepG2 hepatic cancer cells.

Abstract:A high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method was established to conduct qualitative analysis and structural elucidation of the unknown quinocetone metabolites in the body wall of Apostichopus japonicus. Apostichopus japonicus were exposed to the one-time feed containing 20 mg/kg of quinocetone for 24 h, and then were transferred to clean seawater for 72 h. Sea cucumber samples were collected regularly during the experiment for analysis after removal of the viscera. In this study, acetonitrile was used for direct extraction, the extract was dried, and the dried sample was reconstituted in a volumetric flask. After hydrochloric acid hydrolysis, sample enrichment and purification were performed on a solid-phase extraction (SPE) cartridge to detect the quinocetone in the Apostichopus japonicus body wall due to the two pre-treatments as well as to extract and purify the possible metabolites. The metabolites were separated on an ACQUITYTM ? BEH C18（2.1 mm?50 mm, 1.7 μm）column by gradient elution with acetonitrile-water (containing 0.1% formic acid) as the mobile phase, and were detected using full-scan-data-dependent scan (Fullscan-DDA) by positive ion electrospray ionization (ESI+). By comparing the MS1 and MS2 ions of the test sample with those of quinocetone and other metabolite standards, the metabolite MQCA (3-methyl-quinoxaline-2-carboxylic acid) was identified in Apostichopus japonicus body wall, along with other four possible, metabolites for the first time.

Abstract:Mulberry polysaccharide T2 was obtained by water extraction and ethanol precipitation. Proteins were removed by salting out with 4% (mass fraction) ZnSO4 at a rate of 88.52%, to yield mulberry polysaccharide T3, which was isolated and purified by DEAE-52 cellulose ion exchange chromatography. Thus, four fractions: T3-1, T3-2, T3-3, and T3-4 were collected. T3-1 and T3-4 were the main components of mulberry polysaccharide T3. Subsequently, the antioxidant activity of the four components was measured in terms of protective effect on cellular oxidative damage. The cellular oxidative damage model was established after damage of PC-12 cells was induced by treatment with 700 μmol/L H2O2 for eight hours. Effects of all T3 fractions on normal PC-12 cellular proliferation were investigated and the results showed that T3-3 improved cell survival rate to 41.81%. Finally, the protective effect of T3-3 on H2O2-induced oxidative damage in PC-12 cells was investigated. The results showed that 600 μg/mL T3-3 exhibited the strongest protective effect, indicating that T3-3 exerts very strong cellular antioxidant activity at high concentrations.

Abstract:Based on the combination of repeated freeze-thaw cycles, homogenization, and ultrasonic-extraction, the extraction rate between salt-extraction and water-extraction of Spirulina proteins was compared. Taking water-extracted Spirulina proteins as the raw material, six types of Spirulina proteolytic peptides were obtained through enzymolysis of Spirulina proteins using trypsin, chymotrypsin, pepsin, alkaline protease, and papain individually, using alkaline protease and papain together, and using trypsin, pepsin, and chymotrypsin to simulate the digestive processes of the gastrointestinal tract in vitro. Results of the degree of hydrolysis and anti-proliferation effects before and after decolorization suggested that there was no direct correlation between the degree of hydrolysis and the anti-proliferation effects. In addition, decolorization was found to lower the anti-tumor activity of hydrolytic components. Therefore, five types of proteolytic peptides with good anti-proliferation effects were used for ultrafiltration, providing nine components that could significantly inhibit the growth of both MCF-7 and HepG-2 in vitro. Then, the 0~3 K component of alkaline protease was isolated and purified using a Sephadex G-15 column to obtain the A3 component, which had a strong anti-proliferation effect on MCF-7 and HepG-2 cells, showing IC50 values of 64.59 μg/mL and 61.65 μg/mL, respectively. Additionally, another three components, A1, A4, and A5, were obtained, which had strong selective anti-proliferation effects on HepG-2 cells, with IC50 values of 47.67 μg/mL, 79.44 μg/mL, and 69.54 μg/mL, respectively. These results provide a theoretical basis for the development of new drugs and health foods using Spirulina platensis as raw materials.

Abstract:Soybean is a high-quality plant protein source, but it is also one of the top eight food allergens. Glycosylation is an effective method to reduce the allergenic potential of food protein allergens. Xylose was conjugated to soy protein isolate (SPI) by means of glycosylation to form SPI-xylose conjugates. The changes in the antigenicity and allergenicity of glycinin in SPI-xylose conjugates at a specific temperature, specific mass ratio of the protein and sugar, and different reaction times were determined by the indirect competitive enzyme-linked immunosorbent assay, and the structural properties of SPI-xylose conjugates were also studied. The results indicate that glycosylation can effectively reduce the antigenicity and allergenicity of glycinin. The antigenicity of glycinin was reduced from 83.01% to 67.43%; the allergenicity of glycinin was reduced from 46.32% to 29.48%, and both immunoreactivities were relatively low after ten hours of reaction. Glycosylation was confirmed by trinitrobenzene sulfonic acid and sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Fourier transform infrared spectroscopy results showed that compared with SPI, the α-helix and β-turn content in SPI-xylose conjugates decreased, while the β-sheet and random coil contents increased.

Abstract:To preliminarily investigate the hypolipidemic mechanism and effect of Cyclocarya paliurus polysaccharides (CPP) in hyperlipidemic mice, the mice were randomly divided into model control, blank control, simvastatin, low dose CPP, medium dose CPP, and high dose CPP groups (16 mice per group). Model control and blankcontrol groups were orally administered with equivoluminal bacteria-free water. The simvastatin group was administered with a suspension of 4 mg/kg simvastatin and carboxymethylcellulose sodium (CMC-Na; 0.5%). The low-dose, medium-dose, and high-dose CPP groups were administered with 100 mg/kg, 200 mg/kg, and 400 mg/kg CPP water solutions, respectively. After four weeks of feeding, the lipopolysaccharide (LPS) activity and the levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), HDL-C, and free fatty acids (FFA) were determined. The liver was removed to assess the pathological morphology and reverse transcription polymerase chain reaction (RT-PCR) was employed to detect the expression level of hormone-sensitive lipase (Hsl) mRNA. The results indicated that CPP induced a significant reduction in TC, TG, and LDL-C levels and LPS activity (P < 0.01), a significant increase in HDL-C and FFA levels (P < 0.01), and different degrees of improvement in the degree of hepatic steatosis when compared to the model group. Compared with the model group, a remarkable increase of Hsl mRNA expression was observed in CPP groups (P < 0.05). In summary, CPP can significantly decrease blood lipid levels and improve hepatic steatosis due to excessive uptake of lipids in hyperlipidemic mice.

Abstract:The nutritional components in the enzymatic extract of sea cucumber Apostichopus japonicus were measured and analyzed, and the effects of the extract on the immunological function of mice were evaluated according to the “Test Method for Strengthening Immune System Function” in “Health Food Inspection and Specifications for Evaluation Techniques (2003)”. The result showed that the moisture, crude protein, crude fat, ash, phospholipid, polysaccharide, and saponin contents in the enzymatic extract of sea cucumber Apostichopus japonicus were 6.41%, 70.51%, 5.05%, 6.83%, 0.96%, 8.56%, and 0.78%, respectively. In the enzymatic extracts, the total amount of amino acids was 56.046 g/100 g (dry weight); the essential amino acids accounted for 24.2% of the total amino acids and the delicious amino acids accounted for 55.6% of the total amino acids. The low, medium, and high (0.1 g/kg?bw, 0.2 g/kg?bw, 0.6 g /kg?bw) dose groups of sea cucumber extract pronouncedly increased concanavalin A (ConA)-induced T lymphocyte proliferation, showing significant differences compared with control group (p < 0.05); all three groups increased the serum hemolysin level in mice (p < 0.05), and the high-dose group significantly improved the number of antibody-producing cells (p < 0.01); medium and high dose groups also significantly increased the natural killer (NK) cell activity (p < 0.01). Enzymatic extracts of sea cucumber are rich in nutrients and can improve the immunological function of mice.

Abstract:The aim was to study the anti-aging effects of polysaccharides from Lophatherum gracile Brongn. (DZY) using a mouse model of subacute aging induced by D-galactose. Kunming mice were randomly divided into a blank control group, an aging model group, and a low-, medium-, and high-dose DZY group (100, 200, 400 mg/kg, respectively). After 6 weeks, the learning and memory abilities of the mice were measured using Morris water-maze and step-down tests. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the contents of malondialdehyde (MDA) in the serum, liver tissue, and brain tissue were assayed. Thymus and spleen indices and the number of neurons were also determined. The anti-aging effects of DZY positively correlated with increased dosages. Compared with the model group, the high-dosage group showed a significantly higher spleen index, thymus index, and number of neurons (increase of 22.18%, 46.28%, and 25.60%, respectively). In the serum, liver tissue, and brain tissue, there were also significant increases in the activities of SOD (by 34.27%, 29.69%, and 41.63%, respectively) and GSH-Px (by 23.18%, 42.88%, and 45.80%, respectively). However, the contents of MDA significantly decreased (by 19.81%, 56.50%, and 13.31%, respectively). In the step-down test, the learning reaction time decreased by 40.21% and the number of errors decreased by 39.57%. Memory latency increased by 51.58%, while the number of memory errors decreased by 38.26%. The escape latency decreased by 39.27% in the Morris water-maze test, while the number of platform crossings increased by 63.61% (p < 0.01). These results indicated that the polysaccharides from Lophatherum gracile Brongn. had a significant anti-aging effect.

Abstract:To understand the relationship of dielectric properties and physiological properties with the internal qualities of pears during the late growth stage, the open-ended coaxial-line probe technique was used to measure the permittivities (relative dielectric constant and dielectric loss factor ) of pears over the frequency range of 20~4500 MHz during the last 2 months of the ripening period, along with the physiological properties (amount of released ethylene and respiration intensity) and internal qualities (soluble solid content [SSC], firmness, and moisture content). Over the frequency measurement range, decreased with increase in frequency, and had maximum and minimum values at approximately 25 MHz and 1300 MHz, respectively. Over time, and increased after the initial decrease, and sugar content and firmness decreased generally. The respiration peak occurred before the peak of released ethylene, and the time when the peak of released ethylene appeared was the same as the turn point when permittivities changed from decreasing to increasing. Apparent linear relationships of the permittivities with SSC and firmness were not found. The results indicate that the dielectric properties of pears are the reflection of physiological properties and that the maturity of pears can be determined on the basis of values of permittivities. However, it is difficult to use the value of a permittivity at a single frequency to assess the internal qualities of pears.

Abstract:Into DVS Gluconacetobacter xylinums cell suspension, 1% Glutamic acid, 5% trehalose, 10% skim milk, or a mixture of 0.575% glutamic acid ,0.075% trehalose and 6.4% skim milk was added as a cryoprotectant. Their effects of on the cytochemical properties of Direct-Vat-Starter (DVS) Gluconacetobacter xylinus (GBX) cells were determined and compared. Changes in the physiological activity of GBX cells was measured in terms of changes in DNA leakage, total antioxidant capacity, superoxide dismutase (SOD) activity, as well as cellulose synthase and ATP activity of the bacterial cells. The results showed that DNA leakage of the bacterial cells was reduced and total antioxidant capacity, SOD activity, cellulose synthase, and ATP synthase activities were increased by adding 1% glutamic acid, 5% trehalose, 10% skim milk or 0.575% glutamic acid + 0.075% trehalose + 6.4% skim milk as a cryoprotectant during freeze-drying process. The results indicated that the GBX cells were well protected by cryoprotectants, and the optimum protective effect was observed with the compound cryoprotectant 0.575% glutamic acid + 0.075% trehalose + 6.4% skim milk. The results from scanning electron microscopy (SEM) also verify that the various cryoprotectants could significantly reduce the damage to GBX cells during freeze-drying process, thus maintaining good physiological activity of GBX cells.

Abstract:Proteins in the by-products of Grifola frondosa polysaccharides extraction were isolated and their functional properties were studied. Proteins in the supernatant obtained after ethanol precipitation of Grifola frondosa polysaccharide extract were isolated by ultrafiltration membrane with a molecular weight cut-off of 5.0 ku. Polypeptides were obtained by enzymolysis and secondary ultrafiltration of the isolated protein. Functional properties of the polypeptides and proteins, including solubility, foaming capacity, and antioxidant activities,were analyzed and compared. The results indicated that ultrafiltration could effectively isolate and purify the protein, with a purity of 70.24% and a yield of 7.26%. The isolated protein was found to be a high-quality edible protein, with essential amino acids/total amino acids (EAA/TAA) and nonessential amino acids/total amino acids (EAA/NEAA) values of 40.5% and 68.0%, respectively. The solubility and antioxidant activities of the isolated protein were significantly increased after enzymolysis by each enzyme tested. Of these enzymes, papain yielded the highest degree of hydrolysis (DH = 8.94%). The polypeptide showed relatively good antioxidant activities, with scavenging rates for hydroxyl radical (?OH), 2,2-diphenyl-1-picrylhydrazyl (DPPH?), and [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS)? + free radical, of 66.14%, 65.78%, and 98.95%, respectively, while those of the isolated protein were 50.88%, 44.01%, and 72.74%, respectively.

Abstract:The alkaline pectate lyase gene pel from Paenibacillus campinasensis BL-11 was synthesized by total gene synthesis, cloned on a pHKA carrier, and actively expressed in Pichia pastoris GS115. The signal peptide and promoter were optimized, so that the pectate lyase activity reached 432.36 U/mL after induction was carried out by 168-h shake flask fermentation. The basic enzymatic properties of the recombinant pectate lyase were preliminarily measured, and the optimal pH and temperature were 10.0 and 60 ℃, respectively. The residual enzyme activity was still higher than 90% when it was incubated at 50 ℃ for 300 min, while the residual enzyme activity was only about 50% after the treatment was carried out at 60 ℃ for 210 min. The enzyme activity remained more than 90% after the recombinant pectate lyase was treated with different buffer solutions ranging from pH 9~12 for 16 h. This enzyme had strong alkali resistance, but the enzyme activity was slightly decreased after being treated in slightly acidic buffers. Meanwhile, the effects of divalent metal ions on pel expression were also determined. The results showed that Ca2+ was essential for the trans-elimination reaction, and Fe2+, Mg2+ and Ni2+ had activating effects on pel activity, while the enzyme was completely inactivated with metal ion-ethylenediaminetetraacetic acid complexes. In summary, pectate lyase exhibits potential industrial application owing to its good stability under alkali conditions.

Abstract:Based on the complete sequence of the SOD gene cloned from Alicyclobacillus (A). acidoterrestris DSM 3922, quantitative real time polymerase chain reaction (PCR) was used to analyze the differences in SOD mRNA expression levels in A. acidoterrestris under acid and heat stresses. The results showed that the SOD gene of A. acidoterrestris was constitutively expressed under normal growth conditions and was quickly upregulated under acid and heat stress conditions. SOD expression level after 0.5 h of acid stress was 4.63 times higher than that of the control group and then increased to a maximum level, which was 32.55 times higher than that of the control group after one hour of acid stress. Subsequently, the SOD gene expression level rapidly decreased and was 1.67 times higher than that of the control group when acid stress was applied for five hours. When heat stress was applied at 70 ℃ for five minutes, the relative expression level of the SOD gene was 2.81 times higher than that of the control group and then increased to a maximum level, which was 15.05 times higher than that of the control after 25 minutes of heat stress. Subsequently, the SOD gene expression level rapidly decreased and was 4.93 times higher than that of control group when heat stress was applied for 40 minutes. A rapid response is a characteristic of SOD gene expression in A. acidoterrestris under heat and acid stresses, indicating that the SOD gene of A. acidoterrestris was closely related to the unique physiological mechanism for thermoacidophilic adaptation of A. acidoterrestris.

Abstract:Using Vc as control and hydroxyl radical (?OH), 2,2-diphenyl-1-picrylhydrazyl (DPPH?), [2,2′-azino-bis(3- ethylbenzothiazoline-6-sulfonic acid)] (ABTS)? + free radical scavenging activities and ferric-reducing/antioxidant power (FRAP) values as indicators, the interactive effect of the antioxidant activities of jujube polysaccharides (JPs) and jujube flavonoids (JFs) were studied. The results showed positive interactions between the antioxidant activities of JPs and JFs in four reaction systems, which were positively related to the effective concentration and activity of the antioxidants (R2 > 0.82; P < 0.01), as well as to the reaction systems. With ?OH reaction system as a representative example, the ratio of JPs and JFs for the optimum antioxidant activity was 1:1; when the concentration was 1.5 mg/mL, the scavenging rate increased to 97.88%, which was 63.33% higher than that of JPs and 16.36% higher than that of JFs. These results provide a theoretical basis for the study of antioxidant and ant-aging activities by using JPs and JFs as raw materials.

Abstract:The antimicrobial potential of gingerols against six food-related bacteria was investigated in this study. The minimum inhibitory concentrations (MICs) of gingerols against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Shigella dysenteriae, Saccharomyces cereviseae, and Aspergillus niger ranged from 8.0 to 22.0 μg/mL, showing that gingerols could effectively inhibit the growth of all test bacterial pathogens. The time-kill assay demonstrated that the lag phase of S. aureus and S. dysenteriae were apparently delayed by the different concentrations of gingerols. Electron micrographs con?rmed the effects of gingerols on the morphological and ultrastructural characteristics of S. aureus, S. dysenteriae, and A. niger. Electron micrographs revealed that gingerols induced morphological changes to the cell or mycelia, such as shrinkage, local deformation, damage to cell wall and membranes, and loss of cytoplasm. These morphological alterations might be due to the direct effect of gingerols on the cell membrane. DNA damage assay revealed that gingerols had no genotoxic effect on the microbes within the test concentration range, and the functional mechanism of gingerols needs to be explored by further studies.

Abstract:Various microbes are involved in the fermentation of pu-erh tea. , among themAspergillus niger plays a crucial role in this process. Therefore, some consumers worry about the contamination of pu-erh tea with aflatoxins (AFs). In this study, the effect of Yunnan large-leaf Camellia sinensis extract on the growth of A. flavus AS3.4408 was studied by measuring the colony diameter, spore germination, and mycelial dry weight. The effect of Yunnan large-leaf Camellia sinensis extract on the biosynthesis of AFs was studied using ultraviolet fluorescence analysis and HPLC. Tea containing Yunnan large-leaf Camellia sinensis extract was inoculated with A. flavus AS3.4408 and the AF content in the tea was measured in order to evaluate the safety of pu-erh tea. The results showed that the growth and AF production of A. flavus AS3.4408 were significantly inhibited by the Yunnan large-leaf Camellia sinensis extract in a dose-dependent manner. After A. flavus AS3.4408 was inoculated into the tea containing the Yunnan large-leaf Camellia sinensis extract, the strain grew well. However, the AF B1, B2, G1 and G2 were not detected by HPLC, indicating that AF biosynthesis was inhibited by some components of Yunnan large-leaf Camellia sinensis.

Abstract:The lactic acid bacterial strains SDC4-1, MDC3-1, and WDC3-1 were isolated from milk cake and acid whey obtained from Sani area of Yunnan province. A superior strain was identified based on acid resistance and bile salt tolerance tests. The fermentation capability of the superior strain was studied in terms of acid production, post-acidification acetaldehyde production, protease activity, and β-galactosidase assay. All three strains were found to be acid tolerant; MDC3-1 showed the strongest acid resistance with a survival rate of 81%; WDC4-1 showed the weakest acid resistance, with survival rate of 52%. However, only SDC4-1 was tolerant to bile, and the survival rate was 81% after being in contact with 0.5% bile salt for 4 hours. Therefore, SDC4-1 was considered the superior strain. In the fermentation test that followed, SDC4-1 strain showed a perfect curd consistency and the fermented yoghourt was rich in flavors. Additionally, high viable count was noted during the storage period, reaching 9.79 lg CFU/g after a 15-day cold storage, which is far more than the national standard. SDC4-1 showed increased rate of acid production, where acidity reached 82.0°T after 13 hours. Meanwhile, SDC4-1 exhibited good post-acidification, good acetaldehyde-producing ability, strong proteolytic activity, and high β-galactosidase production (up to 7.7 μg/mol), while maintaining stable yoghurt quality during cold storage. Therefore, the selected strain, SDC4-1, showing good fermentability, can be considered for use in the preparation of fermented food.

Abstract:The stability of sea cucumber collagen was improved by crosslinking with natural plant extracts. These data provide a theoretical basis for sea cucumber processing. Sea cucumber Apostichopus japonicus was used as the raw material. The degree of crosslinking of instant sea cucumber body wall with different treatments as well as changes in the texture, the degree of protein degradation, and the microstructure of the instant sea cucumber body walls during storage at 37 ℃ were studied. The results indicated that the elasticity of the body wall of instant sea cucumber crosslinked by Galla chinensis and Fructus chebulae extracts was significantly higher than that of the control group by 1.58 times and 1.16 times, respectively. Compared with the control group, the degree of protein degradation of the body wall of the crosslink treated instant sea cucumbers was reduced by 20~30%. The moisture content, water activity, and moisture state analysis showed that the moisture contents of Galla chinensis and Fructus chebulae treated groups were 13.12% and 16.78% lower than that of the control group, respectively. The decreasing moisture content of the instant sea cucumber helped improve its storage stability. During the storage at 37 ℃, the sensory scores of the sea cumber in crosslinking groups were twice has high as those of the control group and met the sensory requirements that were more easily accepted by consumers.

Abstract:In order to study the icrobial variation during the storage of bulk-marinated duck meat, reveal the nature of meat spoilage, and provide the basis to determine the specific spoilage organisms (SSO), Illumina MiSeq sequencing was used in this study to analyze the diversity of microflora in bulk-marinated duck meat during storage at 4 ℃ and 25 ℃. Bacterial and fungal species diversity showed a downward trend in general during the storage at 4 ℃ and 25 ℃. During the initial stage of storage, the dominant bacteria were Weissella sp., Staphylococcus sp., and unclassified Enterobacteriaceae, and the dominant fungi were Debaryomyces sp. IZ_1257 and Lodderomyces elongisporus. During the mid-to-late stage of storage at 4 ℃, the dominant bacteria were Psychrobacter pulmonis and Staphylococcus sp.; during the mid-to-late stage of storage at 25 ℃, the dominant bacteria were Weissella sp., Staphylococcus sp., Macrococcus caseolyticus, and unclassified Enterobacteriaceae. During the mid-to-late stage of storages at 4 ℃ and 25 ℃, the dominant fungus was Debaryomyces sp. IZ_1257. Compared with traditional method, the information obtained by Illumina MiSeq sequencing provides more information of the sample microecology and a comprehensive description of the diversity of microflora in various environmental samples.

Abstract:A lactic acid bacterium with high angiotensin-I converting enzyme (ACE)-inhibitory activity was screened from 31 isolates obtained from traditional fermented foodsin Yunnan. The isolates were preliminarily screened by ultraviolet (UV) spectrophotometry, followed by high-performance liquid chromatography (HPLC). Potential probiotic properties and dynamic changes in ACE inhibitory activity during skim milk fermentation were evaluated. Lactobacillus plantarum YM-4-3 strain was selected owing to its high ACE inhibitory activity, broad antibacterial spectrum, sensitivity to antibiotics, and strong tolerance to acid and bile. The inhibition zone diameters of Lactobacillus plantarum YM-4-3 against Escherichia coli O157:H7 and Listeria monocytogenes were 41.30 and 42.00 mm, respectively.After treatment with strong acid (pH 2.5) and high concentration of bile salt (0.3%), the viable cell count was still above 105 CFU/mL. The dynamic monitoring of ACE inhibitory activity of Lactobacillus plantarum YM-4-3 during the fermentation of skim milk indicated that the optimum condition for Lactobacillus plantarum YM-4-3 to produce ACE inhibitory peptide was 37 ℃ for 48 h. Under this condition, the ACE inhibition rate of fermented milk reached 81.23%, and the maximum biomass of the strain and the highest content of free amino acid and polypeptides in fermented milk were achieved. This study can provide a theoretical basis and a candidate bacterium for the study and development of a novel, functional fermented milk beverage, with high ACE inhibitory activity.

Abstract:The aim was to interfere with and repress the expression of the alcohol dehydrogenase II (ADH2) gene in a specific region by constructing a silencing expression vector PURH-ADH2. The silencing expression vector contained the ADH2 gene, a PGK strong promoter, and a CYC1 terminator. Using BamHI and XmaI restriction enzymes for the double digestion of the SADH2 and PURH plasmid, the antisense recombinant expression plasmid PURH-SADH2 was constructed. Through high-efficiency yeast transformation and electroporation, the recombinant plasmid components were transformed into Saccharomyces cerevisiae SY01 cells, and positive JY01 clone strains were obtained. Fermentation test results of the S. cerevisiae JY01 mutant strain compared with the original strains, SY01 and Y01, showed that glycerol-3-phosphate dehydrogenase activity decreased by 16.31% and 13.5%, respectively. When S. cerevisiae Y01, SY01, and JY01 were fermented for 36 h, 48 h and 60 h, the glycerol production of JY01 decreased by 16.34%, 14.25%, and 14.89%, respectively, compared with that in the original Y01 strain. After a 48-h fermentation, the ethanol concentrations of Y01, SY01, and JY01 were 6.243 g/100 mL, 7.145 g/100 mL, and 7.288 g/100 mL, respectively. The ethanol production of JY01 was 14.33% higher than that observed in the original Y01 strain. Results showed that the antisense interference of the ADH2 5′ UTR sequence can effectively interfere with ADH2 transcription and expression in engineered yeast strains, weaken glycerol accumulation pathways, and promote ethanol-metabolic pathways.

Abstract:Isolated Aspergillus oryzae PRB-1(AP) strain was applied in the manufacture of koji and high-salt diluted-state soy sauces. The results showed that the acid protease and neutral protease activities of AP koji were 398.53 U/g and 1539.98 U/g, which were increased by 71.79% and 59.93% when compared with those of Aspergillus oryzae 3.042(AO), respectively. The amylase activity of AP koji was slightly lower than that of AO. AP koji contained five neutral protease components, two acid protease components, and four amylase components, among which protease Rf6 and amylase Rf3 showed the highest activity. The total acid content of AP and AO moromi samples increased as the fermentation time was prolonged and the pH value decreased from neutral to acidic. Amino acid nitrogen continuously increased in moromi and the reducing sugar content showed a slow downward trend after the initial sharp increase. The amino acid nitrogen content of AP first filtrate was 0.86 g/100 mL after 55 days of fermentation. Meanwhile, the utilization ratio of raw material (81.97%) and the amino acid production rate (61.37%) of AP were higher than those of AO. The reducing sugar content of AP first filtrate was 4.82 g/100 mL, lower than that of AO. The neutral protease activity of koji was positively correlated with the amino acid production rate (p < 0.05), but had no significant impact on other indices (p > 0.05).

Abstract:The surface of hollow nanoparticles of magnetite (Fe3O4) with an inverse spinel structure was modified by (3-aminopropyl)-triethoxysilane (APTES), followed by coating with polyacrylic acid (PAA) to synthesize pH-sensitive, composite Fe3O4@PAA, hollow magnetic nanoparticles (HMNPs) via chemical crosslinking. The morphology, structure, magnetism, encapsulation ratio before and after encapsulation were analyzed by transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), laser particle size analysis, Fourier transform infrared (FT-IR) spectrometry, and ultraviolet (UV) spectrophotometry techniques., Drug loading and drug release efficiencies of these nanocomposites were investigated in vitro by using rhodamine 6G (R6G) as a model drug. The composite Fe3O4@PAA nanoparticles showed excellent magnetic property, and T maximum adsorption capacity was found to be 1011 mg R6G per 1.00 g Fe3O4@PAA nanoparticles. The maximum drug delivery rate for R6G release from the composite magnetic particles was 93.0%, and the drug delivery dynamics followed first-order kinetics. Additionally, the possible mechanism based on molecular solubility was explored. The results demonstrated that the composite drug loading system, based on magnetic nanoparticles and polymer materials could help to enhance the performance of targeted drug delivery and improve the efficiency of diagnosis and treatment.

Abstract:The whole genome of a typical hard-to-culture beer-spoilage Lactobacilli strain which had never been sequenced was analysized. The Lactobacilli strain was isolated from beer and its genomic DNA was extracted and purified. A high-quality sequencing library was constructed and the whole genome sequencing was then performed using De novo system. The sequences were further analyzed and the predicted genes were obtained, including GO gene function, COG gene function and KEGG pathway. In the whole genome sequences of this Lactobacilli strain, 1,824 genes were predicted and 545, 1,303, and 120 of them had GO, COG, and KEGG annotation, respectively. This study may provide more references for the study of functional gene and bioinformatics analysis of the beer-spoilage lactobacilli strains .

Abstract:Molecularly-imprinted, solid-phase extraction membrane with high selectivity to diniconazole was prepared by in situ polymerization using diniconazole as the template molecule and acrylamide (AM) as the functional monomer. AM was optimized and the binding ability of different functional monomers with the template molecule was investigated by ultraviolet (UV) spectroscopy. This property was also used to select porogens for preparation of molecularly imprinted membrane and the influence of imprinting time on liquid permeability. A method based on molecularly imprinted, solid-phase membrane, high-performance liquid chromatographic was developed for the determination of diniconazole residues in grains. The results showed that compared with the functional monomer α-methacrylic acid (MAA), AM showed a stronger binding capacity to diniconazole. When the molecularly-imprinted diniconazole membrane was prepared using acetonitrile as the porogen, the once-imprinted membrane was stable with a good liquid permeability. A good linear range of diniconazole was obtained in the range of 0.5~15 μg/mL (r = 0.9987). The average recoveries ranged from 80.34% to 87.03%, and the detection limit of diniconazole was 2.0 μg/g. Thus, the method developed in this study is highly selective, sensitive, and reliable, which can be applied for determination of diniconazole residues in grain and other complex matrices.

Abstract:Zein was extracted from corn gluten meal (CGM) and treated at 100 ℃ and 110 ℃ for 10 min, 20 min and 30 min. The effects of heat treatment temperature and treatment time on extraction yield and some structural properties were investigated. Additionally, heat-treated zein was hydrolyzed by alkaline protease alcalase and the effect of heat treatment conditions on the hydrolysis efficiency was studied. The results showed that the extraction yield, amount of free sulfhydryl groups, surface hydrophobicity, and denaturation temperature of zein increased with prolonged treatment time and increasing heating temperature. As the heat treatment time further increased, the surface morphology of the zein aggregates changed, and the amount of zein aggregates and free sulfhydryl groups as well as the denaturation temperature increased continuously, while the surface hydrophobicity, extraction yield, and total denaturation enthalpy of zein decreased. When zein was subjected to alcalase hydrolysis after being processed at 110 ℃ for 30 min, the degree of hydrolysis increased by 8.29% compared with non-pretreated zein.

Abstract:Jiangnan rice cakes were used as the object in this study, and a network analyzer was used to determine the effects of frequency (915~2450 MHz), moisture content of rice cakes (16~48%), and temperature (25~60 ℃) on the relative permittivity ε' and dielectric loss factor ε". The microwave penetration depth was calculated and the impacts of frequency, moisture content, and temperature on the microwave penetration depth were analyzed. A relationship model between dielectric parameters of rice cakes and the main factors at some frequencies was established to examine the accuracy and feasibility of moisture content prediction based on the dielectric parameters. The results showed that in the frequency range of 915~2450 MHz, ε' of rice cakes decreased and ε" increased with increasing frequency; both ε' and ε" increased with increasing moisture content, but decreased with increasing temperature. The value of energy penetration depth decreased with increasing moisture and frequency, and increased with increasing temperature. The relationship between dielectric parameters and the main influencing factors could be described by binary cubic functions, and the coefficients of determination of all models were greater than 0.99. These findings would have an important guiding significance on understanding the dielectric properties of rice cakes and developing moisture detectors.

Abstract:Soybean protein isolate (SPI) adsorbed on the oil-water interface was used as an emulsifier and stabilizer to form an oil-in-water (O/W) emulsion (2.0 wt% protein and 20.0 wt% soybean oil). The characteristics of SPI-stabilized emulsions, including changes in particle size, zeta potential, and microstructure, under the action of simulated gastric fluid (37 ℃, pH 1.2, and 34 mM NaCl ionic strength, with continuous shaking at approximately 95 r/min for 2 h) were investigated. The microstructure and diameter of the emulsion showed that SPI (pH 7.0) was capable of forming a stable emulsion, but underwent extensive droplet flocculation or coalescence when mixed with simulated gastric fluid. The degree of droplet flocculation or coalescence markedly depended upon hydrolysis time. The zeta-potential values gradually changed from -35.9±0.3 mV to +16.3±0.9 mV after the emulsion was mixed with simulated gastric fluid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that when SPI was present at the interface of the O/W emulsion, it was more easily hydrolyzed by pepsin as compared to native SPI solution. This study improves our understanding of the characteristics of an O/W emulsion stabilized by SPI in simulated gastric fluid and has high significance for guiding the design of food systems based on SPI emulsions.

Abstract:Multidrug-resistant and drug-sensitive strains of Escherichia coli were inoculated separately into fresh beef, and cultured at 10 ℃, 20 ℃, 30 ℃, and 40 ℃. The growth data at 25 ℃ and 35 ℃ were used for validation. The primary and secondary models were set up using Origin 8.0 in order to obtain the maximum specific growth rate and lag phase of the two strains at different temperatures. The results showed that the modified Gompertz and Logistic models fit well with the growth parameters of the two multidrug-resistant and drug-sensitive strains in beef (R2＞0.95). The lag phase of drug-sensitive E. coli was shorter than that of the drug-resistant strain. The functional relationship between the parameter values (U and LPD) and temperature was explained by a Belehvadek model. The experimental results showed that the temperature and maximum specific growth rate presented a linear relationship. The maximum specific growth rates at 25 ℃ and 35 ℃ were computed by the secondary growth kinetic model. The deviation value was relatively small when compared with the predicted values and actual values, indicating that the growth model was reliable. These experimental results provide a theoretical basis for the control of E. coli in beef.

Abstract:The effect of different heating voltages and end-point temperatures (EPTs) of ohmic heating on the proteins in the lamb semimembranosus muscle and their correlations with quality indicators, including meat color and water holding capacity were studied. Lamb semimembranosus muscle samples were ohmically heated to internal temperatures of 50, 60, 80, and 100 ℃ with voltages of 10 V/cm and 20 V/cm, respectively. Differential The results showed that compared to the 10 V/cm groups, the 20 V/cm groups exhibited lighter color and higher cooking loss (p < 0.05 at 100 ℃) and a higher degree of sarcoplasmic protein denaturation (p < 0.05). Sarcoplasmic protein solubility showed a strong correlation with cooking loss and meat color indicators. The a* values and cooking loss values were positively and negatively correlated with the soluble sarcoplasmic protein concentration, respectively. Samples were also ohmically heated to 95 ℃ with the voltages of 10 V/cm and 20 V/cm, respectively, followed by seven-day storage. Subsequently, carbonyl, sulfhydryl, non-heme iron, and malondialdehyde contents were measured. The 20 V/cm group presented a higher degree of oxidation than the 10 V/cm group, indicating that the sample treated with 10V/cm presented a relatively good quality.

Abstract:The effects of different repeated gelatinization and retrogradation (RGR) treatments at temperatures of 75, 95, and 121 ℃ on the structural and physicochemical properties of sweet potato starch were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and rapid visco analysis (RVA) were used to evaluate the changes in the structural, crystalline, thermal, and pasting properties of sweet potato starch. The swelling power, solubility, and in vitro digestibility were also determined. The starch granule morphology was damaged or disappeared and irregular lumps formed after RGR treatment at 75, 95, or 121 ℃. For the RGR cycle treatment at 75 ℃, the intensities of the crystal absorption peak and heat absorption peak of sweet potato starch were reduced, while its gelatinization enthalpy decreased. The gelatinization temperature increased and the gelatinization temperature range became smaller. After RGR cycle treatments at 95 and 121 ℃, the X-ray diffraction patterns of sweet potato starch were converted from A-type to B-type and the heat absorption peak disappeared completely. In addition, with the increasing RGR cycles at different temperatures, the solubility of sweet potato starch increased first and then decreased, resulting in a decrease of starch viscosity characteristic value, a weakening retrogradation trend, and an increase of the slowly digestible starch (SDS) content. The highest SDS content (29.25%) of sweet potato starch was found in one RGR cycle treatment (RGR-1) at 121 ℃.

Abstract:The effects of cold-shock treatment (CST) at 3 ℃ on fatty acids present in the membrane lipids and lipoxygenase of cold-stored banana fruits and the related physiological mechanisms were investigated. Banana fruits were treated with cold air at 3 ℃ for 6 h and then stored at 8 ℃ ± 0.5 ℃; the fruits without CST were directly stored at 8 ℃ ± 0.5 ℃ and were used as the control group. The chilling injury index, cell membrane permeability, lipoxygenase activity, and membrane fatty acid composition of banana fruits were measured regularly during the period of storage at 8 ℃ ± 0.5 ℃. After the fruits were stored in a constant temperature oven at 20 ℃ ± 0.5 ℃ for 30 days to accelerate fruit ripening, the conditions of chilling injury and fruit after ripening were observed. Eight fatty acids were identified in the pulp of banana, that is, tridecylic acid, heptadecanoic acid, arachidic acid, cis-10-heptadecenoic acid, trans-linoleic acid, linoleic acid, γ-linolenic acid, and α-linolenic acid. CST at 3 ℃ for 6 h could decrease the chilling injury index, relative conductivity, lipoxygenase activity, and the content of tridecylic acid, heptadecanoic acid, arachidic acid, and other saturated fatty acids (SFAs). Besides, it effectively prevent the decrease in the content of cis-10-heptadecenoic acid, trans-linoleic acid, linoleic acid, γ-linolenic acid, α-linolenic acid and other unsaturated fatty acids (UFSAs). It can also maintain relatively high SFA and UFSA indexes in membrane lipids. Thus, CST enhanced the chilling resistance of banana fruits, reduced the incidence of cold damage, and improved the after-ripening quality of banana fruits.

Abstract:To monitor the process of solid-state fermentation of Chinese herring, parameters including water content, pH, total acid content, amino nitrogen (ANN) content, total volatile basic nitrogen (TVB-N) content, and changes in the taste fingerprint were measured by conventional analytical methods and an electronic tongue. The principal component analysis (PCA) and discriminant analysis (DA) were used to identify fermented Chinese herring samples undergoing different durations of fermentation, while partial least-squares regression (PLSR) prediction models for the electric tongue and related physicochemical indicators were also established and evaluated. The results indicated that the physical indicators and taste of Chinese herring samples changed significantly during fermentation. The accumulative contribution rate of three extracted principal components was 94.49%, the discrimination coincidence rate was 100%, and the Chinese herring samples with different fermentation durations could be identified effectively by both, PAC and DA. In five prediction models based on electronic tongue signals, both relative percent deviation (RPD) values of water content and ANN models were 1.80, and the RPD value of TVB-N model was 2.47, which could be used for qualitative analysis. The RPD values of pH and total acids models were both > 5, which indicated good quantitative effect, good stability, and high prediction accuracy. Thus, it is feasible to identify and monitor the process of solid-state fermentation of Chinese herring using the electric tongue coupled with related chemometric methods.

Abstract:To achieve normalization and standardization of tofu production, the dynamic rheological properties of soymilk and related kinetics during the coagulation process were investigated. Dynamic time scanning was performed at 75 ℃, 80 ℃, and 85 ℃; coagulation of soymilk consisted of two first-order reactions and matched a consecutive first-order reaction model. The rate constant in the first stage was much higher than that in the second stage and the calculated activation energy values from elastic modulus and viscous modulus were 19.19 × 101 kJ/mol and 8.67 × 101 kJ/mol, respectively. Tofu gel could not be formed from soymilk at temperatures below 70 ℃. The elastic modulus G'-t and viscous modulus G"-t curves intersected at 75 ℃, which indicated that the coagulation temperature of soymilk was 75°C. Through dynamic temperature scanning, it was found that the coagulation process could be divided into three stages: induction stage (65 ℃~70 ℃), acceleration stage (70 ℃~92 ℃), and stabilization stage (above 92 ℃). The elastic modulus G' and viscous modulus G" increased slowly and a small amount of flocculent precipitate was generated in soymilk during induction; G' and G" increased rapidly during acceleration and tended to be stable during stabilization, indicating that the coagulation process was complete and tofu gel was formed.

Abstract:The cavitation effect of ultrasonic waves can improve the efficiency of mass transfer in the process of osmotic dehydration. In order to study the drying characteristics and energy consumption of peach slices during ultrasound-assisted osmotic dehydration in combination with infrared radiation, drying experiments after ultrasound-assisted osmotic dehydration were carried out at 60, 70, and 80 ℃, respectively; the drying curves were obtained, and the mathematical models for the drying kinetics were established. Meanwhile, the energy consumption during the drying process was analyzed. The results showed that ultrasound-assisted osmotic dehydration could improve the ratio of water loss and solid gain. The appropriate ultrasound-assisted osmotic times were set at 30 min (T1) and 60 min (T2), and the Verma et al. model was found to be suitable to describe the drying characteristics of peach slices during the ultrasound-assisted osmotic dehydration and infrared radiation. The effective moisture diffusivity values of non-treated, T1 and T2 treated peach slices at 60, 70, and 80℃ were in the ranges of 8.8789 × 10-9~1.3011 × 10-8 m2?s-1, 7.1213 × 10-9~1.0393 × 10-8 m2?s-1, and 6.6771 × 10-9~8.7785 × 10-9 m2?s-1, respectively. With the increase in temperature, energy consumption reduced but increased after ultrasound-assisted osmotic dehydration. Under different treatments, energy consumption increased rapidly with a moisture content of about 0.3 (dry basis), which can be a moisture conversion point to use other drying methods, such as explosion puffing drying at varied temperatures and pressures, to reduce energy consumption and improve product quality. This study provides a reference for the parameter optimization in the infrared drying of peach slices and the development of new fruit slices.

Abstract:The aim was to explore the effect of spray drying on the physiochemical, structural, and functional properties of seed-watermelon seed proteins. The bulk density, color, in vitro digestibility, amino-acid composition, thermal denaturation, surface hydrophobicity, endogenous fluorescence, secondary structure, ultrastructure, and functional properties of spray-dried seed-watermelon seed proteins were compared to those of freeze-dried seed-watermelon seed proteins. The results showed that spray-dried seed-watermelon seed proteins had a larger bulk density (p=0.34 g/mL), greater whiteness, better color, higher in vitro digestibility (96%), a lower ratio of lysine and arginine (0.20), similar essential amino-acid composition, better thermal stability, a higher denaturation temperature (89.06°C), and a higher thermal denaturation enthalpy value (1.75 J/g) compared to the freeze-dried proteins. Additionally, spray-dried seed-watermelon seed proteins showed a red shift in the endogenous fluorescence maximum-emission wavelength from 352 nm to 354 nm, and increased surface hydrophobicity (4097.5) and β-turn content (29.62%). There was also a shift from the α- helix, β-sheet, and random coil secondary structures to β-turns, as well as a decrease in the solubility, water- and oil-holding capacities, emulsifying activity, and foaming properties.

Abstract:Commercially available potato starch, sweet potato starch, mung bean starch, and corn starch were used as controls to investigate the granule morphology, amylose and amylopectin content, gelatinization property, freeze-thaw stability, and gel texture of the starch obtained from Quercus variabilis Bl. acorn grown in the Qinba mountain area. These properties were investigated by scanning electron microscopy (SEM), Rapid Visco Analyzer (RVA), and texture profile analysis (TPA). The results showed that the granules of Quercus variabilis Bl. acorn starches were kidney-, triangular-, oval-, and sphere-shaped, respectively, with an average particle size of 9.4 μm, which is smaller than that of the control starches. The gelatinization temperature of the acorn starch was 71.23 ℃ and the viscosity of gelatinized acorn starch was higher than that of corn starch and lower than that of potato, mung bean, or sweet potato starches. The hot-paste stability of acorn starch was higher than that of sweet potato, mung bean, or potato starches, and lower than that of corn starch. The retrogradation rate of acorn starch was higher than that of potato, corn, and sweet potato starches, and lower than that of mung bean starch. The freeze-thaw stability of acorn starch paste was higher than that of potato starch and lower than that of mung bean, corn, or sweet potato starches. At the same starch concentration, the hardness, gumminess, and chewiness of the acorn starch gel were lower than those of mung bean starch and higher than those of corn, potato, and sweet potato starches. The springiness of the acorn starch gel was higher than that of potato starch, lower than that of sweet potato starch, and the same as that of corn and mung bean starches. The cohesiveness and resilience of acorn starch gel were higher than those of control starches. Therefore, the starch from Quercus variabilis Bl. corn is suitable to be used as auxiliary material for quality improvement in starch-based gel foods including noodles, vermicelli, glass noodles, and jelly, and as a stabilizer in sugar and baking industry. This starch, however, is not suitable for frozen foods.

Abstract:The effects of internal temperature on Tibetan mutton quality during marination were investigated. The effects of internal temperature during marination (30 ℃~ 99 ℃) on the Warner-Bratzler shear force, cooking loss, and protein solubility of Tibetan mutton muscle from hind leg were analyzed. The changes in myofibrillar protein composition and microstructure of Tibetan mutton muscle were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that with increasing internal temperature of marination, the cooking loss gradually increased from 15.82% at 30 ℃ to 41.15% at 99 ℃ (P < 0.05); Warner-Bratzler shear force was gradually increased to the peak value at 70 ℃ (P < 0.05). When temperature reached 80 ℃, the shear force decreased initially before it gradually increased. The protein solubility showed a slow downward trend with increasing internal temperature. The results of SDS-PAGE, SEM, and TEM indicated that with the increase of internal temperature of marination, protein degradation and crosslinking occurred in the myofibrillar tissue, the space among myofibrillar bundles gradually decreased, myofibrillar bundles became denser and more compact, and myofibril diameter and sarcomere length decreased gradually. Therefore, an internal temperature of 70 ℃ is the key temperature point for the quality of marinated Tibetan mutton.

Abstract:The most suitable strain of lactic acid bacteria from four different species, Lactobacillus bulgaricus (Lb), Streptococcus thermophilus (St), L. plantarum (Lp), and L. acidophilus (La), was selected to prepare a fermented oat beverage. The effects of the bacteria on the physicochemical properties, nutritional components, and taste and flavor of the oat beverage were investigated. Compared with the other three strains, Lp showed a faster acid production rate and a larger increase in viable cell count (3.89 × 109 cfu/mL). The viscosity (9.08 mp?s) of the beverage prepared using Lp showed no significant difference from that prepared using La (9.28 mp?s) (p < 0.05), but was significantly higher than those using Lb (7.07 mp?s) and St (7.17 mp?s) (p < 0.05). The oat beverage fermented by Lp showed high content of total phenols (12.43 mg/100 mL), low content of phytic acid (16.49 mg/100 mL), and no significant difference in β-glucan content when compared with beverages prepared using other bacteria (p > 0.05). The results of gas chromatography–mass spectrometry (GC-MS) showed that after Lp fermentation, a larger quantity of aldehydes, alcohols, organic acids, and other volatile flavor components were produced, giving the fermented oat beverage a unique taste and the highest sensory score. Therefore, Lp was chosen as the most suitable lactic acid bacterial strain to prepare the fermented oat beverage.

Abstract:The effect of sugar addition (3%, 6%, 9%, and 12%, m/m) on lipolysis in Cantonese-style sausage was studied. Lean pork and diced fatty meat in Cantonese-style sausage were separated; the lipids were divided into neutral lipid, phospholipids, and free fatty acids (FFAs) by solid phase extraction, and the compositions and content of the fatty acids and FFAs in neutral lipid and phospholipids were determined by gas chromatography-mass spectrometry (GC-MS). The results showed that most lipolysis reactions involved phospholipids; neutral lipid also played a certain role in the release of FFAs, and the lipids in the lean pork played the main role in the lipolysis in Cantonese-style sausage. The proportions of polyunsaturated fatty acids (PUFAs) in neutral lipids and phospholipids were considerably influenced by the amount of added sugar. When a small amount of sugar was added, high proportions of PUFAs were obtained, especially in phospholipids of lean pork. When 12% of sugar was added, the proportion of PUFAs was 17.88%. When 6% and 3% of sugar were added, the proportions of PUFAs were 36.70% and 33.94%, respectively. The content of FFAs decreased with decrease in the amount of sugar, indicating that sugar can promote the lipolysis in sausage. A relatively low proportion of PUFAs was found because PUFAs are easily oxidized.

Abstract:A juice beverage containing juice sacs was prepared from oranges. The effects of juice content and compound thickeners were studied in terms of suspension stability of the extract. The aroma-producing compounds in the beverage were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and their rheological properties were also studied. The results showed that good suspension stability was achieved for the juice beverage containing orange sacs, using four different compound stabilizers: 0.2% xanthan gum+0.25% pectin, 0.15% carboxymethyl cellulose (CMC)+0.2% xanthan gum+0.1% pectin, 0.1% CMC+0.05% xanthan gum+0.1% agar, and 0.1% xanthan gum+0.1% pectin+0.1% agar. The addition of thickeners resulted in higher stability and the juice exhibited characteristics of a non-Newtonian fluid, pseudoplastic fluid. In addition, thickeners influenced the release of several major aroma-producing compounds in the beverage with orange sacs, where different compositions of thickeners showed different effects. The contents of β-myrcene, 3-carene, d-limonene, γ-terpinene, and perillaldehyde decreased significantly, while the apparent viscosity of the orange juice were not directly related to the release of aroma compounds.

Abstract:Organic phosphorus is a type of neurotoxin capable of inhibiting the activity of acetylcholinesterase (AChE) in the blood and tissues. During AChE catalysis, acetylthiolcholine chloride (ATCl) was hydrolyzed to thiol choline (TCl) in aqueous solution, and TCl was oxidized on the surface of the electrode, thus enabling the detection of large current signals. However, both AChE activity and TCl electrochemical signals produced by hydrolysis decreased in the presence of organic phosphorus. Based on this principle, a new biosensor for the quantitative determination of organic phosphorus was constructed by immobilizing functionalized multi-wall carbon nanotubes (FMWCNTs), p-DSPAB, and AChE on the surface of carbon-paste electrodes. The content of MWCNTs was 1.0 μg/cm2 and the AChE load on the modified electrode was 1.5 U. Under optimal conditions, the measurement of organic phosphorus by differential-pulse voltammetry was performed in 5.0 mL of 50 mmol/L PBS (pH 7.0) solution using 3.0 ng/mL ATCl as the substrate. The detection parameters were as follows: pulse increment, 0.006 V; pulse amplitude, 0.05 V; pulse width, 0.1 V; and pulse interval, 0.1 s. According to the change in the response current and the concentration of organic phosphorus, the biosensor offered a linear range of ~3.00–90.00 ng/mL for the detection of organic phosphorus, and the detection limit was 1.00 ng/mL (S/N = 3). Compared with HPLC, this method has the advantages of simplicity, rapidity, sensitivity, and accuracy in the determination of organic phosphorus.

Abstract:To understand the quality and volatile substances in different grape varieties, the components and relative contents of volatile substances in the fresh grapes of four different varieties were measured using head space solid-phase micro extraction combined with gas chromatography mass spectrometry. An electronic nose (E-nose) was used to verify the results, and the quality characteristics were analyzed. Significant differences were found in the quality indicators among the four varieties. Among them, seedless Han Xiang-mi had a relatively high soluble solid content and titratable acidity, and Xiang Yue had high vitamin C content and fruit firmness. From the matured fruits of the four varieties, 87 volatile substances were detected and most of them were alcohols, esters and aldehydes. Differences were also found in the volatile substance content. Xiang Yue, Muscat Hambourg, Jin Shou-zhi, and Han Xiang-mi had the highest relative content of ethyl acetate, linalool, leaf aldehyde and ethyl acetate, respectively, and the corresponding flavors were strawberry flavor, rich aroma of roses, fresh green leafy aroma, and strawberry flavor, respectively. The volatile substances were also analyzed by the electronic nose, principal component analysis, and linear discriminant analysis, which could successfully differentiate the four different varieties. Therefore, the post-harvest quality differences in grapes were determined and the approach employing an electronic nose combined with GC-MS can effectively evaluate the volatile substances in grapes.

Abstract:A new method based on membrane dialysis/high performance liquid chromatography-tandem mass spectrometry (MD/HPLC-MS/MS) was developed for the analysis of nine β-agonist residues (e.g., clenbuterol, ractopamine, salbutamol) in livestock products. The samples were extracted with ammonium acetate buffer, enzymolyzed by β-glucuronidase/arylsulfatase, and purified with a standard-grade regenerated cellulose dialysis membrane (RC, MWCO: 1000 D). The residues of β-agonists were infiltrated through the membrane into the dialysis solution, which was extracted with cyclohexane-ethyl acetate (4:1). The β-agonists were separated with Waters Xbridge C18 columns using a gradient elution with 0.1% formic acid-acetonitrile as the mobile phase. The β-agonists were detected by positive electrospray ionization (ESI+) in the multiple reaction monitoring (MRM) mode, and the quantification analysis was performed by an external standard method. The results showed that the nine β-agonists had good linearities in the range from 0.5 μg/kg to 10 μg/kg. The limits of quantitation for all β-agonists were 0.5 μg/kg. The recoveries of these analytes varied from 72.5% to 92.6% at the spiked levels of 0.5 μg/kg, 1.0 μg/kg, and 2.5 μg/kg. The relative standard deviation of the method varied from 4.1% to 12.7% (n = 6). The method was based on membrane dialysis and expensive solid-phase extraction cartridges were not required. Thus, this method is economical, highly sensitive, and suitable for the determination of the nine β-agonists residues in livestock products.

Abstract:Vibrio parahaemolyticus is a food-borne pathogen that causes gastroenteritis and other diseases worldwide, with consumption of contaminated raw or undercooked seafood. To develop a method for rapid and specific detection of V. parahaemolyticus in seafood, its genomic sequence was analyzed and compared with those of other Vibrio species, a V. parahaemolyticus-specific genetic marker was screened, and a nested-PCR-based method to rapid detect V. parahaemolyticus was established based on this gene. Additionally, the specificity, sensitivity, and reproducibility of this method were assessed. The results showed that the target amplicon only appeared with V. parahaemolyticus genomic DNA as the template, but not the other 11 Vibrio species and non-Vibrio species. The limits of detection of this method were 10 fg V. parahaemolyticus genomic DNA and 6.6 colony-forming units (CFU) for purified culture. Artificial contamination experiments indicated that V. parahaemolyticus could be detected after two hours of enrichment with an initial concentration of 25.7 CFU/100 mL. In conclusion, the VP1331 gene can be used as a V. parahaemolyticus-specific marker, and this PCR method can be used for the detection and identification of V. parahaemolyticus in contaminated seafood.

Abstract:In order to establish a method to accurately and effectively detect zeaxanthin and its stereoisomers, the zeaxanthin products formed by iodine-catalyzed photoisomerization were separated using different mobile phases, ratios of the mobile phase, and elution times. The qualitative and quantitative analyses of zeaxanthin and its stereoisomers were conducted using spectroscopy, chromatography and mass spectrometry. The results indicated that the optimum conditions for the detection of zeaxanthin and its stereoisomers were as follows: mobile phase A: methanol, methyl tert-butyl ether (MTBE), and water (ratio, 80/15/5); mobile phase B: methanol and MTBE (ratio, 1/10); elution time: 24 minutes. In the zeaxanthin products from the iodine-catalyzed photoisomerization, 15,15′-, 13,13′-, and 9,9′-mono-cis-zeaxanthin isomers were identified by comparing the maximum absorption wavelength for each peak, Q value, and ion fragments in mass spectra with those in related reports. Peak area and injection volume of all-trans-zeaxanthin showed a good linear relationship in the range of 5–250 ng. The proposed method showed advantages including good reproducibility, high accuracy, and rapid detection, which is suitable for the detection of zeaxanthin and its stereoisomers.

Abstract:Nitrite (NO2-) was detected by a glassy carbon electrode (GCE) modified by hemoglobin (Hb) with gold nanoparticle-reduced graphene oxide (AuNPs-rGO) composite. The qualitative and quantitative detection of nitrite were conducted using the signal of a direct electron transfer generated from methemoglobin and NO3- that were produced by the redox reaction between hemoglobin and nitrite. The GCE surface was modified by AuNPs-rGO composites to produce AuNPs-rGO/GCE, which was modified by Hb after drying to form an Hb/AuNPs-rGO/GCE biosensor. After the modified electrode was coated with 80 μL of 0.5% Nafion to form a Nafion film, the Nafion/Hb/AuNPs-rGO/GCE biosensor was finally obtained. The results showed that the biosensor had good selectivity and sensitivity when cyclic voltammetry method was used to detect nitrites, with a relative wide linear range from 0.5 to 100 μM. The relationship between peak current and the nitrite concentration could be described by the linear equation of IP = 0.0369C(NO2-) + 0.2245 (R = 0.9918), and the limit of detection was 0.1 μM. This method is simple, rapid, sensitive and can be used for nitrite detection in food and environmental samples.

Abstract:The effects of different amounts of added star anise (0, 0.05%, 0.10%, 0.20% and 0.30%) on the volatile compounds of marinated chicken drumsticks were analyzed by an electronic nose and gas chromatography-mass spectrometry. The results showed that the electronic nose could distinguish between marinated chicken drumsticks with different amounts of star anise added. The main effect was that the relative contents of volatile compounds in the chicken drumsticks changed, while there were no changes in the types of volatile compounds. The volatile compounds in the five groups of marinated chicken drumstick samples mainly included aldehydes, alcohols, ketones, and esters. With increasing amount of added star anise, the relative content of aldehydes and alcohols decreased after the initial increase, while the relative content of ketones continuously increased. Compared with the control group，the presence of the newly presented volatile compounds, including terpenes and their oxygenated derivatives, of the marinated chicken drumsticks was mainly attributed to the addition of star anise, and the relative content and number of these compounds increased with the increasing amount of star anise. The highest number of new volatile compounds was found when the amount of added star anise reached 0.30%.

Abstract:Volatile aromatic components produced during the brewing process of red raspberry vinegar were separated and identified by headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). This was combined with the odor threshold value to determine the relative odor activity value at different brewing stages. Principal Component Analysis (PCA) was then applied to evaluate the contribution of aromatic components to the overall flavor of raspberry vinegar in order to determine the key flavor of raspberry vinegar. Four key flavor compounds in red raspberry juice–β-ionone, damascenone, D-limonene, and naphthalene, were found. After the alcohol fermentation stage, β-ionone and ethyl acetate were the two key flavor compounds produced. After the acetic acid fermentation stage, β-ionone and α-ionone were the two key flavor compounds. After the aging stage, β-ionone, ethyl acetate, and α-ionone were the three key flavor compounds. PCA showed that PC1 reflected the important role of microbial fermentation and aging in the formation of the overall flavor in red raspberry vinegar. PC2 showed that the aromatic compounds and carbonyl compounds changed significantly during the formation of flavor in red raspberry fruit vinegar.

Abstract:Xihu Longjing tea, one of the famous teas of China, has a long history and superior aroma quality, is and originally produced in Xihu district, Hangzhou city, Zhejiang Province. It is greatly favored by many consumers. The aroma components of 24 Xihu Longjing tea samples were investigated by solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME/GC-MS), and their GC-MS fingerprints were established. Optimal extraction for HS-SPME in this study was achieved with 50/30 μm CAR-DVB-PDMS fiber and extraction for 30 min with a water bath temperature of 60 ℃. In the GC-MS fingerprints established for the aroma components of Xihu Longjing tea, a total of 24 characteristic peaks were identified, and their peak areas accounted for 76.20% of the total peak area. The GC-MS fingerprints were analyzed by cosine and correlation coefficient methods, and a high similarity among different Xihu Longjing tea samples was observed. Cluster analysis demonstrated that Xihu Longjing tea samples with different grades could be grouped into one cluster. Thus, this method, which is based on GC-MS fingerprints combined with cluster analysis, can provide a scientific reference for aroma quality evaluation of Xihu Longjing tea.