花生红衣中原花青素A1的分离鉴定及其对丙烯酰胺的抑制效果

以花生红衣原花青素（peanut skin procyanidins,PSP）混合物经过凝胶色谱分离后得到的第4个级分PSP-4为原料,通过制备型高效液相色谱分离得到1?种原花青素,记为PSP-4-1,并利用液相色谱-四极杆飞行时间质谱及核磁共振技术鉴定其结构。分别比较其在化学模拟体系和炸薯条食品体系中对丙烯酰胺的抑制效果。结果表明：分离制备得到的PSP-4-1结构为表儿茶素-（2β→O→7,4β→8）-儿茶素（原花青素A1）,在化学模拟体系和炸薯条食品体系中对丙烯酰胺的抑制均呈非线性的质量浓度-抑制率关系,在化学模拟体系中,原花青素A1添加质量浓度为0.05?mg/mL时抑制率可达（58.10±3.86）%,在炸薯条食品体系中原花青素A1添加质量浓度为0.03?mg/mL时抑制率可达（57.16±2.61）%。这一研究对于开发一种高效、经济的丙烯酰胺抑制剂具有指导意义。     

天然植物提取物对萝卜干腐败菌抑菌研究

实验用肉桂、五倍子、陈皮、桂皮、丁香、艾叶、补骨脂、桑白皮、甘草、连翘、大蒜、姜、茶叶水提取液对萝卜干的4种常见腐败微生物(克柔念珠菌,枯草芽孢杆菌,蜡样芽孢杆菌,金黄色葡萄球菌)进行了抑菌试验。并且研究了最有效的添加剂的最低抑菌浓度以及pH有效作用范围。结果表明,茶叶水提取液的抑菌效果最好,其次是五倍子。茶叶水提取液对枯草芽孢杆菌、蜡样芽孢杆菌、克柔念珠菌和金黄色葡萄球菌的最低抑菌浓度分别为:5%、10%、5%和5%。且在pH值3～7范围内抑菌能力稳定。     

Coagulase-negative staphylococci species affect biofilm formation of other coagulase-negative and coagulase-positive staphylococci

Coagulase-negative staphylococci (CNS) are considered to be commensal bacteria in humans and animals, but are now also recognized as etiological agents in several infections, including bovine mastitis. Biofilm formation appears to be an important factor in CNS pathogenicity. Furthermore, some researchers have proposed that CNS colonization of the intramammary environment has a protective effect against other pathogens. The mechanisms behind the protective effect of CNS have yet to be characterized. The aim of this study was to evaluate the effect of CNS isolates with a weak-biofilm phenotype on the biofilm formation of other staphylococcal isolates. We selected 10 CNS with a weak-biofilm phenotype and 30 staphylococcal isolates with a strong-biofilm phenotype for this study. We measured biofilm production by individual isolates using a standard polystyrene microtiter plate assay and compared the findings with biofilm produced in mixed cultures. We confirmed the results using confocal microscopy and a microfluidic system with low shear force. Four of the CNS isolates with a weak-biofilm phenotype (Staphylococcus chromogenes C and E and Staphylococcus simulans F and H) significantly reduced biofilm formation in approximately 80% of the staphylococcal species tested, including coagulase-positive Staphylococcus aureus. The 4 Staph. chromogenes and Staph. simulans isolates were also able to disperse pre-established biofilms, but to a lesser extent. We also performed a deferred antagonism assay and recorded the number of colony-forming units in the mixed-biofilm assays on differential or selective agar plates. Overall, CNS with a weak-biofilm phenotype did not inhibit the growth of isolates with a strong-biofilm phenotype. These results suggest that some CNS isolates can negatively affect the ability of other staphylococcal isolates and species to form biofilms via a mechanism that does not involve growth inhibition.     

基于LC-MS/MS的酸乳肽谱及ACE抑制活性

利用液相色谱-串联质谱(liquid chromatography-tandem mass spectrometry,LC-MS/MS)的方法,对4种酸乳(优味舒风味发酵乳、风味发酵乳、初乳24+K风味发酵乳和十天风味发酵乳)的肽谱进行分析,分别鉴定到152、125、364条和274条肽段。利用血管紧张素转换酶(angiotensin converting enzyme,ACE)的抑制活性比较以上4种酸乳的生物活性,在相同质量浓度2.0 mg/L时,4种酸乳ACE抑制率分别为46.84%、42.75%、77.41%和63.84%。初乳24+K风味发酵乳含有肽的数量大、ACE抑制活性高可能与其独特的原料成分相关。对4种酸乳的肽谱及ACE抑制活性的考察,为进一步研究酸乳肽的功能特点和ACE抑制活性提供了理论依据。     

4种防腐剂对副溶血弧菌生物膜形成的抑制作用

在确定4种防腐剂壳聚糖、山梨酸钾、脱氢乙酸钠和ε-聚赖氨酸对副溶血弧菌(Vibro parahaemolyticus)的最小抑菌浓度(minimum inhibitory concentration,MIC)的基础上,研究其对副溶血弧菌生物膜的抑制作用。采用结晶紫染色法测生物膜形成量,XTT法测生物膜代谢活性,硫酸-苯酚法测定生物膜中胞外多糖的分泌量。结果表明,壳聚糖的MIC最小,为1.25 mg/m L。4种防腐剂在MIC以及亚抑菌浓度条件下对副溶血弧菌生物膜均有明显的抑制作用,不仅抑制生物膜的形成,而且能显著降低细菌的代谢活性,减少胞外多糖的分泌,其中壳聚糖对副溶血弧菌生物膜的抑制作用最强。     

用于农残快速检测的离心式微流控芯片研制

基于酶抑制原理结合光度分析方法,研制一种预存储生化试剂的离心式微流控芯片。设计制作的一次性微流控CD芯片集成进样、酶抑制反应、显色反应及检测单元,结合自行研制的便携式分析装置,可以同时检测12个样品,能够实现对大批量农产品中有机磷和氨基甲酸酯类农药残留进行现场、快速、高通量检测。结果表明:与传统农残快速测定仪比较,微流控芯片农残速测系统操作单元集成度高,可以实现农残检测流程的自动化,样品及试剂消耗量降至传统速测方法的约1/20,同时检测灵敏度、重复性和准确性整体优于传统农残快速测定仪,可以满足基层非专业人员针对大批量样品农药残留的筛查需求。     

Molecular Cloning and Characterizations of Xylanase Inhibitor Protein from Wheat (Triticum Aestivum)

Xylanase inhibitor proteins (XIPs) were regarded to inhibit the activity of xylanases during baking and gluten‐starch separation processes. To avoid the inhibition to xylanases, it is necessary to define the conditions under which the inhibition takes place. In this study, we cloned the XIP gene from 2 different variety of Triticum aestivum, that is, Zhengmai 9023 and Zhengmai 366, and investigated the properties of XIP protein expressed by Pichia pastoris. The results showed that the 2 XIP genes (xip‐9023 and xip‐366) were highly homologous with only 3 nucleotide differences. XIP‐9023 showed the optimal inhibition pH and temperature were 7 °C and 40 °C, respectively. Inhibition of xylanase by XIP‐9023 reached the maximum in 40 min. At 50% inhibition of xylanase, the molar ratio of inhibitor: xylanase was 26:1. XIP‐9023 was active to various fungal xylanases tested as well as to a bacterial xylanase produced by Paenibacillus sp. isolated from cow rumen.     

Effect of raspberry pomace extracts isolated by high pressure extraction on the quality and shelf‐life of beef burgers

Raspberry pomace extracts isolated with supercritical carbon dioxide (SCE) and pressurised ethanol/water (ETE) were tested in beef burgers. Only ETE additives effectively inhibited lipid oxidation and the growth of microorganisms, as it was observed by measuring the changes of thiobarbituric acid reactive substances, bacterial counts and the content of O₂ and CO₂ during storage in the modified atmosphere package. ETE additives also demonstrated some meat colour preservation effects, which were assessed by the intensity of hamburger colour and metmyoglobin concentration. However, ETE additives did not alter burger's taste at the applied concentrations (up to 1%). It may be concluded that the most effective extracts possessing strong antioxidant and antimicrobial activity may be isolated from raspberry pomace by the pressurised liquid extraction with a hydroethanolic solvent; such extracts may be considered as promising additives in meat products for improving their stability and enriching with beneficial to health phytochemicals.     

果蔬加工中果胶甲基酯酶活性抑制的研究进展

果胶甲基酯酶（pectin methylesterase,PME）是一种广泛存在于高等植物、真菌和细菌的果胶降解酶,其残余活性会导致果蔬汁和鲜切果蔬等产品产生分层沉淀、析水结块、质构软化等品质劣变。因此,在果蔬加工过程中实现对PME活性的有效抑制是加工的重要目的。目前生产中对于PME活性的抑制主要以热加工方式为主,但这会对热敏性果蔬产品品质造成不可逆转的不良影响。随着人们生活水平和健康意识的提高,为了满足人们对更高品质产品的追求,一些新型热加工和非热加工技术以及PME抑制剂逐渐被研究并应用于PME活性的抑制。本文综述当前热、非热加工方式和抑制剂对于PME的抑制效果及其机理,并列举不同加工方式联合处理或加工手段与抑制剂联合处理在PME抑制方面的应用情况,以期为未来更高品质果蔬产品的加工提供理论指导。     

乙二醇抑制DES预处理过程中木质素缩合程度的研究

利用氯化胆碱/草酸和氯化胆碱/草酸/乙二醇2种低共熔溶剂（DES）体系预处理竹粉以分馏提取木质素,并通过多种表征手段探究木质素的结构变化。结果表明,在110 ℃反应180 min的条件下,氯化胆碱/草酸二元DES体系提取的木质素（二元DES木质素）中β-O-4芳基醚键的相对含量仅为0.26/Ar,氯化胆碱/乙二醇/草酸三元DES体系提取的木质素（三元DES木质素）此值则为0.43/Ar。同时,二元DES木质素中的缩合结构（β-β,β-5=3.11/Ar）及缩合的芳环C—C连接（Aromatic C—C=2.18/Ar）多于三元DES木质素（β-β,β-5=2.02/Ar,Aromatic C—C=1.99/Ar）。利用超声辅助三元DES体系预处理过程,发现反应20 min后木质素脱除率即可达76.0%。采用水相电位滴定法测定不同反应条件下的三元DES木质素的酚羟基和羧基含量;并提出乙二醇在三元DES体系预处理竹粉过程中抑制木质素缩合的机理,证实乙二醇与对香豆酸和阿魏酸反应生成了酯化的木质素结构。