黄曲霉菌的差异挥发性代谢产物及其代谢途径分析

为了弥补当前食品安全检测技术相对滞后的缺陷,构建了气相色谱-质谱(GC-MS)结合顶空固相微萃取(HS/SPME)技术用于探究黄曲霉菌的挥发性代谢产物,并结合代谢组学和基因组学分析豆腐干中黄曲霉菌差异性代谢产物及其代谢途径。结果表明黄曲霉菌的差异性代谢物包括1,2,3-三甲基-苯、均三甲苯、乙醇、十六烷酸甲酯、2,4-二叔丁基苯酚、乙酸、三氯甲烷、1-丁醇、1-甲基-3-(1-甲基乙基)-苯。特别地,乙酸、乙醇和1-丁醇在黄曲霉菌代谢网络中起关键作用。     

金黄色葡萄球菌污染牛奶后的代谢产物研究

为解决食品安全中存在的隐患,作者构建了气相色谱-质谱（GC-MS）结合顶空固相微萃取（HS/SPME）技术用于探究金黄色葡萄球菌的挥发性代谢产物,并结合代谢组学和基因组学分析牛奶中金黄色葡萄球菌的差异性代谢产物及其代谢途径。结果表明,金黄色葡萄球菌的差异性代谢物包括N-甲硫基甲酰胺、1-丁醇、乙酸、乙苯、均三甲苯、辛酸、苯甲酸、正癸酸、十二烷酸、乙醇、苯酚和丙二醇。之后对其进行基因组学分析得到金黄色葡萄球菌主要是以基础的生命代谢为主,明确了代谢网络中参与代谢的物质（乙醇、乙酸、1-丁醇）的代谢途径和相关基因。本研究为金黄色葡萄球菌的生物标志物研究提供了理论基础。     

基于非靶向代谢组学分析副干酪乳杆菌发酵枸杞汁各阶段代谢差异

为研究副干酪乳杆菌NXU-19004发酵对枸杞汁品质特性的影响,采用气相色谱-质谱非靶向代谢组学技术对4 种不同阶段枸杞发酵液差异代谢物进行鉴定分析,结合主成分分析和偏最小二乘判别分析对其进行精确区分。再通过京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes,KEGG）数据库注释差异代谢物参与的代谢途径,从中筛选出关键代谢物。结果表明,4 种发酵液共检测到63 种非挥发性差异代谢物,其中氨基酸类、有机酸类、酯类等成分在枸杞发酵液中平均相对丰度总体呈上升趋势。多元统计分析结果显示,各样品之间差异显著,均有明显样本聚集区,表明代谢产物可用于甄别发酵阶段。共注释到47 条代谢途径,富集代谢产物较多且显著性高的关键通路有9 条,且多与氨基酸代谢相关,可见发酵阶段对枸杞发酵液中氨基酸类物质的代谢影响最大。进一步确认了关键代谢物为丙氨酸、柠檬烯、苯甲醛、苯甲酸、烟酰胺、烟酸、角鲨烯、脯氨酸、肌氨酸、2-苯基乙酰胺。该研究从代谢组学角度初步揭示了枸杞及其乳酸菌发酵产品的代谢产物差异性以及特征化合物,为进一步研究影响乳酸菌发酵形成差异的因素提供理论依据。     

基于非靶向代谢组学分析牛肉干法成熟过程代谢产物的变化

以不同成熟时间的牛上脑肉为研究对象,借助超高效液相色谱-质谱技术,基于非靶向代谢组学方法分析干法成熟过程中牛肉代谢产物的变化情况,并对代谢产物进行多元统计分析和代谢通路分析。结果表明,牛肉干法成熟过程中有41种代谢物被鉴定为差异代谢物,包括氨基酸类物质21种、脂肪酸类物质16?种、核苷酸类物质2种以及其他代谢物2?种。通过对差异代谢物的种类和相对含量进行分析,发现随着成熟时间的延长,差异代谢物的种类和相对含量显著增加。通过对差异代谢物的代谢途径进行分析,筛选出5条关键代谢通路,分别为嘌呤代谢,脂肪酸降解,丙氨酸、天冬氨酸和谷氨酸代谢,精氨酸和脯氨酸代谢,三羧酸循环,这些代谢途径对成熟牛肉风味和营养物质的形成具有促进作用。     

微发酵对牛肉干风味的影响

为改善和丰富市场上牛肉干的口味,以未加发酵剂制作的牛肉干为空白组,通过电子感官仪器、气相色谱-嗅闻-质谱联用仪、氨基酸分析仪和感官评价研究微发酵对牛肉干风味的影响。结果表明,微发酵对牛肉干的风味影响较大。电子感官仪器可以很好区分2 组样品,说明微发酵可以改善产品的风味。与空白组相比,微发酵可以显著提高产品的挥发性风味物质和游离氨基酸含量,说明微发酵可以促进产品滋味和气味物质的形成。通过火山图分析,结合相对气味活度值、嗅闻检测和味觉分析系统分析结果,得到微发酵牛肉干的特征性滋味物质为谷氨酸,特征性气味物质为3-甲基丁醇、己醛、辛醛、壬醛、反式-2-癸烯醛、反,反-2,4-癸二烯醛和3-甲基丁酸,为后续牛肉干的风味调控提供一定的理论基础和技术支持。     

不同品种绿豆中代谢产物的分离鉴定及代谢机制分析

利用气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）分离鉴定不同种类绿豆（大明绿豆和九鲤湖绿豆）中的代谢产物。以代谢组学研究方法为基础,以绿豆为研究对象,先利用甲醇溶液提取极性代谢组分,再用N,O-双(三甲基硅烷基)三氟乙酰胺进行衍生化处理,通过GC-MS进行代谢产物的分离鉴定。结果表明：分离鉴定共得到2?个品种绿豆的总代谢物67?种,其中相同代谢产物30?种,但含量均有不同。大明绿豆相对于九鲤湖绿豆的差异代谢物有10?种,九鲤湖绿豆相较于大明绿豆的差异代谢物有20?种,并且九鲤湖绿豆的糖代谢途径、脂肪酸代谢途径、氨基酸代谢途径、三羧酸循环都比大明绿豆代谢活跃;在大明绿豆中,较为优势代谢产物（＞7%）为L-正缬氨酸、肌醇2?种,在九鲤湖绿豆中,较为优势代谢产物仅为L-正缬氨酸。这种代谢产物差异性受不同品种的基因差异性、代谢途径和机制差异性等因素的综合影响。     

基于UHPLC-MS技术分析贵州红、白酸汤代谢物差异

以贵州红酸汤、白酸汤为研究对象，基于超高效液相色谱-质谱（UHPLC-MS）非靶向代谢组学技术分析分析贵州红、白酸汤中代谢产物差异，并对其进行主成分分析（PCA）及正交偏最小二乘-判别分析（OPLS-DA），以变量投影重要性（VIP）值>1结合t检验P值<0.05为标准筛选差异显著代谢物，并进行代谢通路分析。结果表明，酸汤样品中共注释到2 929个代谢物，正离子模式差异显著代谢物数为1 223种，负离子模式差异显著代谢物数为1 173种。差异显著代谢物在Super Class分类上，脂类化合物占14.96%，有机酸及其衍生物占8.5%，有机杂环化合物占6.87%，苯环类化合物占4.17%，有机氧化合物占3.52%，苯基丙酸类和聚酮类化合物占2.7%。根据京都基因与基因组百科全书（KEGG）代谢通路富集分析，差异显著代谢物主要富集在正离子模式下的莽草酸途径生物碱的生物合成、血清素能突触通路和负离子模式下组氨酸和嘌呤的生物碱生物合成通路，其中显著差异代谢物主要为生物碱、酚类和黄酮类物质。     

绞股蓝茯砖茶代谢物特征及其体外降血脂作用

为探究绞股蓝茯砖茶特征性代谢物的变化及其潜在功能,该研究利用液质联用技术对绞股蓝茯砖茶代谢物进行分析;进而对绞股蓝茯砖茶与传统茯茶的差异性代谢产物进行鉴定、分类,并对产生途径进行分析。最后,通过体外试验评价绞股蓝茯砖茶的降脂、降糖的功效。结果表明：与传统茯砖茶相比,绞股蓝茯砖茶中共发现10 类142 种显著性差异代谢产物,主要包括38 种脂质和类脂分子、29 种有机酸及其衍生物、19 种有机杂环化合物和15 种苯丙烷和聚酮类等。代谢通路富集分析结果发现,绞股蓝茯砖茶差异性代谢物主要集中在脂类代谢通路、碳水化合物代谢通路、氨基酸代谢通路等方面。绞股蓝茯砖茶体外降血脂作用是同浓度的辛伐他汀药物的17.88%～36.52%,体外降血糖作用是同浓度的阿卡波糖药物的13.63%～58.18%。该研究探讨绞股蓝茯砖茶的代谢物特征及其潜在的降血脂和降血糖活性,为开发功能性茯砖茶产品,推动茯茶产业多元化发展提供理论依据。     

基于非靶向代谢组学分析老面酵头传代发酵过程中的代谢差异

以老面酵头为研究对象,采用基于超高效液相色谱-四极杆飞行时间质谱（UHPLC-QTOF-MS）的非靶向代谢组学分析技术对老面酵头传代发酵过程的差异代谢物进行鉴定分析,并研究老面酵头传代发酵过程中的风味特征代谢物的相对含量变化和关键代谢通路。结果表明,传代发酵1代、2代和4代的代谢产物存在差异,共鉴定出54种差异代谢物,主要的差异代谢物种类为氨基酸及肽类、有机酸类和糖类。共检索到15条与差异代谢物相关性高的关键代谢通路和14种主要参与的差异代谢物,其中关键代谢物为D-麦芽糖、鞘氨醇、L-谷氨酸、纤维二糖、鞘磷脂、甘油磷酸胆碱。该研究从代谢组学角度初步揭示了老面酵头传代发酵过程的代谢产物差异性以及特征化合物,为进一步对老面酵头发酵过程中的风味调控机制提供理论依据。     

基于代谢组学分析光照对油茶鲜果后熟过程代谢物的影响

为解析光照条件下油茶鲜果的特征性代谢物,采用液相色谱-电喷雾-串联质谱（liquid chromatography electrospray ionisation tandem mass spectrometry,LC-ESI-MS/MS）对后熟过程油茶鲜果进行广泛靶向代谢物分析。结果表明：共鉴定出739种代谢物,其中正离子模式和负离子模式下鉴定的代谢产物数量分别为711种和28种,共55个代谢物种类,主要有萜类118种、生物碱类97种、黄酮类88种、酚类53种、苯丙素类52种、类黄酮44种等。主成分及聚类热图分析表明,油茶鲜果不同后熟处理中光照对其代谢物有明显影响。代谢途径富集分析表明差异代谢物主要参与了类黄酮、黄酮和黄酮醇的生物合成。     

Reduction of Numbers of Salmonella typhimurium on Poultry Parts by Repeated Freeze-Thaw Treatments

Cells of Salmonella typhimurium suspended in 50 ml of 0.1% buffered peptone were subjected to five cycles of rapid or slow freezing and rapid or slow thawing. A five cycle rapid freeze-rapid thaw process was found to be an effective treatment resulting in 99% reduction in the numbers of S. typhimurium cells. Of the surviving cells after treatment, 75% was sublethally injured. The five cycle rapid freeze-rapid thaw process was investigated for its effectiveness in reducing numbers of S. typhimurium cells on experimentally inoculated chicken wings. The part of chicken wings consisting of ulna and radius with attached skin and muscle was inoculated with low (16–20 CFU/g) or high (ca 1,100 CFU/g) numbers of S. typhimurium and each wing was subjected to five cycles of the rapid freeze-rapid thaw process. There was over 90% reduction in the numbers of S. typhimurium cells on the chicken wings after the freeze-thaw treatment.     

豆腐渣微波真空干燥实验的研究

豆腐渣是生产豆腐或豆浆的副产品,其营养丰富,可被用于许多方面。但因其含水量高,容易腐败变质,所以将豆腐渣及时进行干燥处理,是扩大其开发利用的前提条件。研究了豆腐渣的微波真空干燥特性,比较了不同干燥方法对豆腐渣品质的影响。结果显示,微波真空干燥过程中,干燥速率随微波功率和真空度的增加而加快,尤其是在较大功率（700～380W）和较高真空度（100～60kPa）时这种趋势更为明显。采用二次多项式逐步回归方法,得到了微波真空干燥过程中豆渣含水量与微波功率、真空度、干燥时间之间的回归模型,采用微波功率510W、真空度80kPa、干燥时间30min的工艺参数效果较好。与热风干燥和冷冻干燥相比,微波真空干燥豆腐渣能够节约90%以上的干燥时间,且干制品的品质接近冷冻干燥。因此,微波真空干燥是适合豆腐渣干燥的有潜力的干燥技术,具有良好的应用前景。     

Reduction of Pathogens Using Hot Water and Lactic Acid on Beef Trimmings

Beef trimmings from young or mature beef cattle were obtained commercially. Trimmings within age type then were inoculated with about 6.0 log₁₀ CFU/mL of rifampicin-resistant. Escherichia coli O157:H7 and Salmonella typhimurium (ATCC 13311) were randomly assigned to 1 of 3 treatments (control; 95 °C hot water alone, or with 2% L-lactic acid). After treatment, trimmings were ground, held for 0, 14, 28, or 42 d in chub packages at 4 °C, and total aerobic plat counts, E. coli O157:H7, and S. typhimurium counts were determined. Non-inoculated trimmings were also treated and samples were evaluated for pH, fat, moisture, TBA, meat color by colorimeter, and meat color, and odor by trained sensory panels. Trimmings treated with water or hot water plus lactic acid reduced levels of E. coli O157:H7 and S. typhimurium and tended to be darker after treatment. Meat odor in the final product was not affected by treatment.     

Survival of Listeria monocytogenes and Salmonella typhimurium and Quality Attributes of Cooked Pork Chops and Cured Ham after Irradiation

Cooked pork chops (pumped with salt/polyphosphate brine or untreated) and cured hams were inoculated with Listeria monocytogenes and Salmonella typhimurium. The samples were irradiated at low (0.75 to 0.90 kGy) or medium doses (1.8 to 2.0 kGy), and each dose was delivered at either a low (2.5 M/min conveyor speed) or high (5.4 M/min) dose rate. Low-dose irradiation reduced L. monocytogenes by more than 2 log and S. typhimurium by 1 to 3 log. Pathogen populations and total plate counts (TPC) were reduced to undetectable levels by medium doses. No meat quality attributes were affected, and no dose rate effect was observed. Nitrite reduced (P < 0.05) both pathogens and TPC during 7°C storage in ham, especially when combined with low-dose irradiation.     

Sodium Lactate Affects Pathogens in Cooked Beef

Cooked, quartered beef top rounds containing either 1, 2, 3 or 4% sodium lactate were aseptically sampled and slice sections were inoculated with Listeria monocytogenes (ATCC 43256), Staphylococcus aureus (ATCC 27154), Salmonella typhimurium (ATCC 13311), Clostridium perfringens (ATCC 12924), or Escherichia coli O157:H7 (ATCC 43895). Inoculated slices were stored at 10°C for 0. 7. 14. 21 or 28 days.‘Three and 4% sodium lactate generally displayed lim-ited proliferation of S. typhimurium, L. monocytogenes and E. coli O157:H7 when compared with control roasts (0% sodium lactate) and roasts containing 2% sodium lactate.     

传统卤豆干工艺优化及其对风味物质的影响

针对传统卤豆干卤制不透、产品质量不稳定等问题,以大方县本地黄豆为原料,采用卤汁与压榨成型耦合技术生产卤豆干,并经单因素实验和正交试验优化生产条件,研究了新工艺对卤豆干风味、品质及营养物质的影响。结果表明:采用新工艺生产,卤汁与豆花浸渍比1:1,食盐添加量1.5%,浸渍时间10 min,卤豆干风味最佳,感官评分为90.42。此时豆干外表光滑,口感细腻,风味突出,硬度及弹性优良。与传统豆干相比,NaCl含量由36.35 mg/100 g降低至24.01 mg/100 g,挥发性风味物质由优化前27种提升至31种,芳香族类物质和其他类物质含量明显提升,卤汁与压榨成型耦合生产卤豆干工艺可行。     

Destruction of Salmonella typhimurium on Chicken Wings by Gamma Radiation

No viable CFU of a streptomycin-resistant S. typhimurium were detected on chicken wings inoculated with 100 CFU and treated with 1.8 kGy or greater doses of gamma radiation at 5°C in air. The inoculated S. typhimurium did not recover from radiation injury during 3 days of refrigerated storage. Viable CFU were detected on wings inoculated with 1,000 or 10,000 CFU and irradiated with 1.8 kGy but not on those irradiated with 2.7 or greater kGy. The indigenous aerobic mesophilic population on the wings was reduced from 10⁴ to 44 CFU/cm² by 1.4 kGy.     

Chemical Spray Conditions for Reducing Bacteria on Chicken Skins

Chemical spray parameters, including temperature, pressure and exposure time, were evaluated for their effects on reducing Salmonella typhimurium on chicken skins. Pre-chilled chicken carcass skins were inoculated with S. typhimurium and sprayed with 0.1% cetylpyridinium chloride (CPC), 10% trisodium phosphate (TSP), or 2% lactic acid (LA). In the CPC spray, the 40°C treatments resulted in the greatest bacterial reduction. The most effective spray temperatures for LA and TSP treatments were 40 to 55°C. All chemical spray treatments at 207–1034 kPa reduced S. typhimurium. The reduction of S. typhimurium was greatest in all treatments when sprayed with 90 sec spray and 90 sec setting time.