关键词：
pulsed electric field (PEF);Escherichia coli;non-thermal sterilization;inactivation mechanism;transcriptome
摘要：
Pulsed electric field (PEF) is an up-to-date non-thermal processing technology with a wide range of applications in the food industry. The inactivation effect of PEF on Escherichia coli was different under different conditions. The E. coli inactivated number was 1.13 +/- 0.01 lg CFU/mL when PEF was treated for 60 min and treated with 0.24 kV/cm. The treatment times were found to be positively correlated with the inactivation effect of PEF, and the number of E. coli was reduced by 3.09 +/- 0.01 lg CFU/mL after 100 min of treatment. The inactivation assays showed that E. coli was inactivated at electrical intensity (0.24 kV/cm) within 100 min, providing an effective inactivating outcome for Gram-negative bacteria. The purpose of this work was to investigate the cellular level (morphological destruction, intracellular macromolecule damage, intracellular enzyme inactivation) as well as the molecular level via transcriptome analysis. Field Emission Scanning Electron Microscopy (TFESEM) and Transmission Electron Microscope (TEM) results demonstrated that cell permeability was disrupted after PEF treatment. Entocytes, including proteins and DNA, were markedly reduced after PEF treatment. In addition, the activities of Pyruvate Kinase (PK), Succinate Dehydrogenase (SDH), and Adenosine Triphosphatase (ATPase) were inhibited remarkably for PEF-treated samples. Transcriptome sequencing results showed that differentially expressed genes (DEGs) related to the biosynthesis of the cell membrane, DNA replication and repair, energy metabolism, and mobility were significantly affected. In conclusion, membrane damage, energy metabolism disruption, and other pathways are important mechanisms of PEF's inhibitory effect on E. coli.
摘要：
低频电场解冻(low-frequency electric field thawing,LFEFT)与常温解冻(room temperature thawing,RTT)会导致牛肉pH值、颜色、总挥发性盐基氮(total...展开更多 低频电场解冻(low-frequency electric field thawing,LFEFT)与常温解冻(room temperature thawing,RTT)会导致牛肉pH值、颜色、总挥发性盐基氮(total volatile base nitrogen,TVB-N)含量、质构特性和持水力等方面显著不同,从分子水平解析LFEFT对牛肉品质影响的可能机制,采用蛋白质组学技术对2种解冻方式牛肉进行分析。结果表明:LFEFT组与RTT组之间有551个差异丰度蛋白(differentially abundant proteins,DAPs),其中14种DAPs与牛肉品质特性(pH值、色泽、TVB-N含量、质构和持水力)呈显著相关;生物信息学分析表明,DAPs主要参与蛋白结合、代谢酶和蛋白质周转等生物功能。LFEFT既可以提高生产效率,又保证了牛肉品质。收起
通讯机构：
[Yu Xiao; Yuanliang Wang] C;College of Food Science and Technology, Hunan Agricultural University, Changsha 410128, China<&wdkj&>Hunan Province Key Laboratory of Food Science and Biotechnology, Changsha 410128, China
关键词：
Maotai-Flavored Liquor;High-Throughput Sequencing Technology;Microbial Community Structure;Biodiversity Analysis
摘要：
The grains fermented in Maotai-flavored liquor can be classified into two groups: high-temperature fermented grains generated by stacking and grains fermented in pits. The Maotai-flavor making process enriches a special microbiota from the fermented grains, which makes related studies more difficult. The use of modern molecular techniques to detect and analyze diversity and changes in total bacterial (16S rRNA sequencing) and fungal (internal transcribed spacer (ITS) sequencing) counts have helped to overcome the shortcomings of traditional technological research. The total RNA extracted by Fe3O4-SiO2 nanoparticles was retrieved into DNA by MagBeads Total RNA Extraction Kit. However, discrepancies exist in the microbial community structures at different fermentation periods. Dominant bacteria include Escherichia-Shigella, Lactobacillus, Clostridium, and Streptococcus species and dominant fungi include Alternaria Ciliophora, Pyrenochaetopsis, Cyphellophora, Aspergillus, Issatchenkia, Pichia, Candida, and Zygosaccharomyces species. Analyses of the enzymatic activity of samples at different fermentation stages have revealed that some existing bacilli influence amylase activity. Here, to investigate flavor changes during each fermentation round, the liquor quality at all rounds was comprehensively assessed based on the corresponding physicochemical properties, which were summarized by sensory evaluation. These results suggested that the liquor quality in the third, fourth, and fifth fermentation rounds was superior.
摘要：
Traditional dry-cured pork, a meat product with a unique flavor and good chewability, occupies an important place in the Chinese market. However, the salt content of dry-cured pork is on the high side and long-term consumption of high-salt meat products is not good for human health. This study determined the role of salt in volatile organic substances and non-volatile taste components of dry-cured pork. Dry-cured pork samples with different salt content (0%, 1%, 3%, 5%, and 7%) were analyzed by electronic tongue for moisture content, pH, salt (NaCl) value, taste activity value, free amino acids, and taste components and by headspace-gas chromatography-ion mobility spectrometry for volatile organic components. The results showed that the moisture content of the tested samples decreased while the salt content increased. The highest amounts of free amino acids were found in dry-cured pork with 3% salt content (P < 0.05). The highest peak area of volatile organic compounds and the maximal taste indexes were found in dry-cured pork with 3% and 5% salt content.
摘要：
The aim of this study was to investigate the composition and function of microorganisms during the production of high-temperature Daqu, high-temperature stacking process, and in-pit fermentation with genomic DNA extraction at different periods. The microbial diversity of each fermentation period was analyzed using high-throughput sequencing. Results show that the quantity and distribution of the microbial flora in the diverse environment of high-temperature Daqu, stacking fermentation, and bacterial community are identical. The differences in the ecological environment between high-temperature Daqu and stacking fermentation leads to dominance of different bacteria. The dominant microorganisms in the high-temperature production process included Clostridium sensu stricto (cluster I), Escherichia-Shigella, Lactobacillus, Streptococcus, Alternaria, Issatchenkia, Pyrenochaetopsis, and Pichia, whereas the dominant microorganisms of fermented grains in stacking fermentation included Escherichia-Shigella, Lactobacillus, Clostridium sensu stricto (cluster I), Streptococcus, Actinobacillus, Bifidobacterium, and Alternaria. In agreement with flavor characteristics, the activities of protease, lipase, alpha-amylase, and glucoamylase in the "second round" of fermentation showed regular changes. The activities of protease, lipase, and alpha-amylase in the high-temperature stacking process were higher than that in in-pit fermentation. However, glucoamylase activity showed an opposite trend. The contents of some acids, such as acetic acid, isobutyric acid, and propionic acid in the in-pit fermentation were higher than those in stacking fermentation, whereas ethyl lactate content showed a different trend. The content of alcohol, total acids, and total lipids decreased with time. In addition, the liquor quality reached the best character in the third, fourth, and fifth liquor rounds, which preliminarily justifies brewing Maotai-flavored liquor with microorganisms in different fermentation periods. In addition, the flavor substances formed correlated with the microbial flora. Lactobacillus, Escherichia-Shigella, and Clostridium sensu stricto (cluster I) were the dominant microorganisms. Certain dominant yeasts and molds with possible antagonistic and agonistic interactions among themselves and different fungi can produce metabolites related to Daqu production, which further affect liquor flavor and quality.
