Abstract:Facing "the 14th Five-Year Plan" or beyond, accelerating the drive of scientific and technological innovation and improving the level of food safety are the important cornerstone of supporting the implementation of national food safety strategy, healthy China and rural revitalization strategy. This paper expounds the new concept of food quality and safety, analyzes the current situation and problems of scientific and technological development in the field of food quality and safety both at home and abroad, puts forward the development direction and key points of food quality and safety technology, and prospects the new development trends of above fields in China.

Abstract:Food safety has become a global concern. Food incidents caused by various foodborne pathogenic bacteria occur frequently. Therefore, the development of safer and more efficient sterilization methods have always been a research focus in food industry. As a novel non-thermal sterilization method, photodynamic technology has attracted much attention due to its great advantages including easy to operate, excellent sterilization effect, safety and reliability, environmental friendliness, and low cost. This review summarizes the mechanism and research progress of photodynamic technology, the development of photosensitizer, and the application of photodynamic technology in food industry, which aims to provide reference for enlargement of the application range of photodynamic technology in food industry.

Abstract:N-acetyl-D-glucosamine（GlcNAc） is an important functional monosaccharide. In the production of GlcNAc using recombinant Bacillus subtillis（B. subtilis）, accumulation of acetate inhibites cell growth and GlcNAc production, which also decreases GlcNAc yield. To construct a B. subtilis cell factory with efficient acetate utilization and GlcNAc production, expression of acetyl-CoA synthetase AcsA, which catalyzes the conversion of acetate to Ac-CoA, was modulated in this study. Specifically, the global transcriptional regulator CodY binding sites in the 5' UTR region of acsA were mutated to promote transcription of acsA；then, enzyme AcsA was modified by deacetylation to improve its activity. Finally, the accumulated acetate during shake flask fermentation reduced from 6.3 to 3.6 g/L, dry cell weight increased from 2.7 to 5.3 g/L, and the GlcNAc yield was increased by 163% up to 5.0 g/L, which indicated that the developed strain offers improved properties for GlcNAc production.

Abstract:Yeasts with good characteristics are important for the alcohol fermentation in bergamot vinegar production while limonin in bergamot will inhibit the yeast growth. This study aimed to screen yeast strains with favorable characteristics in bergamot fermentation based on the unique properties of bergamot. Eighty five yeast strains were screened from natural fermented bergamot juice and the yeast strain named FS-ZJQ with good ethanol and organic acids production ability was selected through a three step screening method. Strain FS-ZJQ was identified as Saccharomyces cerevisiae in taxonomy through 18S rDNA sequencing and it showed strong ability to tolerate sugar, pH and alcohol. This strain could produce 8.49% alcohol in 18 °Bx bergamot juice when fermented at 25 ℃ for 7 d. High contents of terpenoid and ester compounds were observed in bergamot wine, which accounted for 58.83% and 16.44% of the total volatile compounds. After acetic fermentation, the content of non-volatile acids reached 5.06 mg/mL.

Abstract:In order to improve the catalytic properties of AEx11A，a glycoside hydrolase（GH） family 11 xylanase from Aspergillus oryzae，the Thr⁹⁸，Asn¹⁰⁰，Val¹²⁴，Pro¹²⁹ and Ile¹³²-encoding codons in AEx11A were selected for saturated mutagenesis by whole-plasmid PCR technique. Then，the mutagenesis libraries of AEx11A were constructed by transforming these variants into E. coli BL21（DE3），respectively. Using the enzyme activity of xylanase as criterion，transformants having an increase of more than 30% in activities were selected from the libraries by DNS method. Two mutation sites（Thr⁹⁸ and Val¹²⁴） with remarkably increased enzyme activities were subjected to iterative saturation mutation（ISM） and the optimal mutant，AEx11^AT98D-V124Q，was selected. The specific activity and catalytic efficiency of purified AEx11^AT98D-V124Q were 3.04- and 2.74-fold those of AEx11A. An improvement in the thermostability of AEx11^AV124T was observed compared with that of AEx11A，while the temperature properties of the other two mutants almost had no changes.

Abstract:Citrus disease caused by Penicillium expansum has become increasingly serious, which is responsible for economic loss to citrus producing areas. The research on the infection of citrus with postharvest pathogens was mainly focused on P.ditalicum and P.italicum, whereas the studies on the conditions of P.ditalicum infecting citrus have not been reported. In this study, the effects of different temperatures, wetness duration and fungus age on P.ditalicum H1 infection of citrus were investigated. The results showed that P.ditalicum H1 had the shortest incubation period and the strongest infectivity at 25 ℃, while at 4 ℃ the infectivity was inhibited. Longer wetness duration was beneficial to P.ditalicum H1 infection. The fungus age also affected the infection of citrus with P.ditalicum H1 with the order of infectivity: cultured for 7 d>11 d>15 d>9 d>3 d.

Abstract:Endo S（EC 3.2.1.96）is a β--N-acetylglucosaminidases from Streptococcus pyogenes, which can specifically hydrolyze the Fc N-glycan of immunoglobulin G（IgG）. In this study, recombinant plasmid BL21(DE3）/pET28a-endo S was constructed and the protein was successfully expressed in E. coli BL21（DE3） cells with confirmed enzymatic activity. Then, single-factor optimization, including screening of basal mediums, nitrogen and carbon sources, mineral salts, expression temperature and time, and initial pH of cultural medium, was performed at shake flask level to express the Endo S in a high level. Under the optimized medium（beef extract 25.4 g/L, yeast powder 10.0 g/L, NaCl 5.0 g/L, glycerol 4.0 g/L, pH 8.0）and condition（induced by 0.25 mM IPTG at 20 ℃ for 24 h）, the yield of recombinant enzyme was 225 mg/L after purification by Ni-resin affinity chromatography, which was 3.5 times higher than that before optimization and 5.6 fold higher than the highest yield reported.

Abstract:The method for Agrobacterium -mediated transformation of Aspergillus niger was improved by optimizing the co-culuture materials, Agrobacterium species, inducer concentration, co-culture time and temperature as well as the Agrobacterium concentration during co-culture. The optimum conditions for the transformation of A. niger were 10 ⁷ /mL non-germinated fresh spores and Agrobacterium with OD₆₀₀ 0.9~1.0 in a ratio of 1∶1, and 200 μmol/L acetosyringone in the IM plate. The mixed cells were then transfected at 23 ℃ for 48 h, and the number of transformants reached 60 ± 5 transformants / 10⁶ spores, and the positive rate reached over 90%. The expression vector of homologous A. niger lipase with constitutive or inducible promoter was constructed and transformed into A. niger by the optimized Agrobacterium-mediated transformation method. Finally the positive transformants were identified by Rhodamine-olive oil plate.

Abstract:Chu orange（Citrus sinensis Osbeck） essential oil is widely applied in food, medical, and cosmetic industries for its unique odor and antibacterial properties. However, its poor water solubility and strong volatility limit the wider application of this essential oil. In order to overcome these disadvantages, O/W Chu orange essential oil nanoemulsion was prepared with the non-ionic surfactant emulsifiers Tween 80 and Span 80. The effects of surfactant ratio, concentration and emulsification shear rate on the particle size, zeta potential, rheological viscosity and emulsion stability of Chu orange essential oil nanoemulsion were studied.The stable nanoemulsion with the particle size （135 ± 0.76） nm and the absolute vale of zeta potential （30 ± 0.36） mV was obtained under the conditions of 5%（w/w） Chu orange oil, 3% Tween 80 and Span 80（1∶2）, and shear rate of 12 000 r/min. In addition, the antibacterial activity of the Chu orange essential oil nanoemulsion was stronger than that of the pure essential oil，which suggested that nanoemulsion can efficiently improve its utilization. This opens up the possibility of expanding the application of Chu orange essential oil.

Abstract:In order to screen out strains for Xinjiang Naan, 12 strains of Saccharomyces cerevisiae from local yogurt, leaven and wine were used and the resulting flour doughs were compared with those by active dry yeast and local traditional starter yeast. Three strains（J-T111-4, S-S167-1, and SC9） among them had a good ability to rise the dough. Their abilities to rise the dough, produce acids and reduce the content of sugars and the growth were measured and the sensory characteristics of resulting Nann were evaluated by traditional Huokeng. The results showed the starter of J-T111-4 had the good growth and strong ability to rize the dough, the resulting doughs had the low acidity and content of sugars, and Naan had typical flavor and strong aroma, which made the strain the best candidate. The Naan fermented by SC9 strain showed good soft texture during chewing. This research affords good strains for the industry of Naan in Xinjiang.

Abstract:In this study, neutral protease and lipase were selected as exogenous enzymes applied in the production of bacon to accelerate the mature process. The uniform design method was used to optimize four key technical indicators(amount of neutral protease and lipase, tumbling and curing time). Differences of flavor precursors, protein hydrolysates, and fat oxidation index between traditional and exogenous enzyme fast mature bacons were investigated comparatively. The results showed that, addition of neutral protease and lipase could effectively promote the accumulation of flavor precursors. With the increased amount of exogenous enzymes, the degree of hydrolysis of bacon protein was significantly escalated, and the non-protein nitrogen, free amino acids and acid value were all increased notably. The values of thiobarbituric acid increased at the beginning and then decreased. When the amount of neutral protease was above 200 mg/kg, the degree of protein hydrolysis of bacon exceeded 20%. When lipase addition was 600 mg/kg, the acid value of bacon reached a maximum of 1.52 mg/g. Compared with the traditional bacon, the bacon with exogenous enzymes was richer in flavor. The contents of non-protein nitrogen and total free amino acids were all abundant. In addition, the contents of 7 free amino acids significantly increased in bacons with exogenous enzymes. The exogenous enzymes played an important role in promoting the formation of bacon flavor, effectively reducing the amount of salt added, and greatly shortening the product processing cycle. It had an important application value in the modernization of traditional bacon meat.

Abstract:In order to explore the new technology of food preservation, the synergistic antibacterial effect of LED visible light and organic acids were studied, and a novel storage method for the food industry was provided. The antibacterial effects of LED visible light wavelength, the type of organic acids, temperature on the Escherichia coli and Bacillus subtilis were investigated. The results showed that LED blue light had better antibacterial effect compared to green light and red light, while lactic acid had better antibacterial effect compared to citric acid and malic acid in different test conditions. The combination of the LED blue light and citric acid could achieve better antibacterial effects. With the combination of LED blue light and 1 g / kg lactic acid at 12 ℃, Escherichia coli at an anitial concentration of 6 lg（CFU/mL） could be completely inactivated, and the number of Bacillus subtilis could be decreased by（3.88±0.17） lg（CFU/mL）; At 25 ℃, compared with the blank control group, the number of Escherichia coli and Bacillus subtilis could be decreased by（4.99±0.07） lg(CFU/mL), （3.12±0.09） lg(CFU/mL), respectively.

Abstract:Strains tolerant of 20 g/L penicillin sodium were screened from the soil near the penicillin production company. A strain named Anti-Pen20 with highly efficient degradation of penicillin sodium was screened by high performance liquid chromatography. Based on the colony, cell morphological characteristics and the analysis of the 18S rRNA gene sequence, the strain Anti-Pen20 was found to belong to the genus Rhodotorula mucilaginosa. The degradation rate of penicillin sodium was 85% after culturing 24 h at 30 ℃ when Anti-Pen20 was inoculated with 15% and the initial concentration of sodium penicillin was 20 g/L. Anti-Pen20 showed high degradation rate in high concentration penicillin sodium medium, which is expected to be applied to the recovery of high concentration penicillin sodium slag, also provides research basis for the application of Anti-Pen20 as an additive for disease prevention in animal feed and fruit industry.

Abstract:Vinegar makers in China have suffered from brewing spoilage during high temperature seasons that seriously affects the nutritional composition and quality of vinegar. In order to thoroughly study the high temperature tolerant spoilage microbes, our research team selected five batches of spoilage vinegar samples for microbe isolation and identification and the composition of the gas producing bacterial consortium TYF-LIM-L09 was analyzed by microbial metagenomic sequencing. The TYF-LIM-L09 was then characterized for pH and ethanol tolerance, gas production capacity and activities of core enzymes in glucose metabolism. The results showed that 4 stable bacterial consortium and 46 strains were separated from spoilage vinegar samples, 44 strains of them belonged to the genera Rummeliibacillus, Enterococcus, Vagococcus, Lactobacillus, Bacillus, Staphylococcus, Brevundimonas, Paenibacillus, and the other two isolated strains came from unknown genera. The bacterial consortium TYF-LIM-L09, which had a strong gas-producing ability, could grow well at 50 ℃and had a high ethanol tolerance of 8% (v/v), was composed of more than 6 genera. The produced gas was CO2 and the highest concentration could reach 71.43%(v/v). The pyruvate kinase and pyruvate decarboxylase of TYF-LIM-L09 had relatively high activities. In summary, TYF-LIM-L09 was presumed to be the key microbial contaminant causing vinegar to swell.

Abstract:To investigate inoculation effects of different lactobacillus on sauerkraut（Suancai）fermentation, Lactobacillus brevis, L. oligofermentans, L. curvatus and L. plantarum isolated from traditional fermentation sauerkraut, were used for inoculation. The analyses included physicochemical index, microbial colony forming unit（CFU） and the bacterial community composition and dynamics at 12 d and 30 d in fermentation. The results showed that the lowering of pH and the accumulation of lactic acid of the fermentation system were more rapid in the inoculated groups than those in the control group, and the CFU of lactic acid bacteria (LAB) in the inoculated groups were significantly higher than that in the control group at 6 d fermentation. According to the Illumina MiSeq sequencing analyses，the relative abundance of Lactobacillus in all inoculated groups was higher than in the control group, and the relative abundance of Enterobacteriaceae and Pseudonomnas was lower. Among the inoculated treatments，at 30 d fermentation，the pH value with L. plantarum was the lowest, lactic acid contents with L. curvatus and L. plantarum were the highest, and acetic acid contents with L. brevis and L. oligofermentans were the highest. At the phyla level，the detected microorganisms consisted of Proteobacteria and Firmicutes. At the genus level，at 30 d fermentation，the relative abundance of Lactobacillus in the L. plantarum treatment was the highest，while the relative abundance of Enterobacteriaceae and Pseudonomnas was the lowest. The results would provide technical references for constructing the appropriate inoculants used for different fermentation purposes.