纤维素微纤丝改性方式对胶原纤维复合膜性能的影响

利用金属-多酚网络（metal-polyphenol network，MPN）和不同程度羧基化改性制备的纤维素微纤丝（cellulose microfibrils，CMF）与胶原纤维（collagen fiber，CF）共混制成复合膜，探究CMF改性方式对复合膜性能的影响。结果表明：MPN改性的CMF能使复合膜抗氧化性能提高51.49%，断裂延伸率和阻光性也有显著提高；MPN和高含量羧甲基共同改性的CMF能最大程度降低MPN对复合膜机械强度的影响；MPN和高含量羧乙基共同改性的CMF能使复合膜对水蒸气和氧气的阻隔能力分别提高1.30 倍和3.48 倍。扫描电子显微镜和红外光谱分析表明不同方式改性的CMF与CF之间是物理交联且具有良好的相容性，从而为提高复合膜的性能以更好地应用到食品包装领域提供了一种新手段。     

金属-多酚网络/纤维素微纤丝复合物的制备及其抗氧化性和稳定性研究

利用Fe³⁺和单宁酸（TA）制备金属-多酚网络（MPN）,并用于纤维素微纤丝（CMF）的功能化改性,以制备CMF-MPN复合物,探讨CMF与MPN制备条件对CMF-MPN复合物抗氧化性和稳定性等的影响。结果表明,MPN可赋予CMF抗氧化性,当TA与Fe³⁺质量比为4∶1、pH值为3制备的MPN添加量为2%（相对于绝干CMF质量）时,所得CMF-MPN复合物的DPPH清除率达97.0%;热重分析结果表明,CMF-MPN复合物残余质量相对于CMF提高了8.13%,但最大热降解温度略有下降;傅里叶变换红外光谱分析结果表明,CMF与MPN间的吸附为物理吸附;以CMF为载体可以提高MPN结构的稳定性,放置60天后仍能保持初始抗氧化性的80%左右,具有缓慢持续释放抗氧化因子的性能,这为开发绿色食品保鲜包装材料提供了新思路。     

金属有机框架材料在食品检测中应用的研究进展

食品安全问题始终是社会关注的热点之一。为保障食品安全和人类健康,对食品污染物进行检测是控制和消除其所造成风险的关键。因此,开发灵敏、准确的食品污染物检测方法具有十分重要的意义。金属有机框架（metal-organic frameworks,MOFs）是一类由金属离子或金属团簇与有机配体自组装而成的新型多孔晶体材料,具有孔隙率高、比表面积大、结构可调、功能多样等优点,越来越受到学界关注。MOFs可与多种检测技术、样品前处理技术相结合,在食品检测方面具有广泛的应用前景。本文综述了近些年MOFs及其复合物材料在食品检测中应用的研究进展,主要包括作为传感检测材料和作为色谱法样品前处理材料应用的研究,同时对其在食品安全领域中存在的应用问题进行了总结,并展望了其在食品安全领域未来的研究方向。     

鱼皮明胶和多酚组装行为与相互作用

研究不同结构多酚与鱼皮明胶（fish skin gelatin,GLA）间的相互作用及组装行为,期望对水产品加工、副产品的利用和新型食品配料的开发提供科学依据,同时为多酚-蛋白质复合物在食品领域的应用提供理论指导。选取单宁酸（tannic acid,TA）、表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）、没食子酸3 种含有不同数量邻三元酚结构的多酚为研究对象,以体系浊度和复合物粒径为考察指标,探讨多酚添加量、pH值对GLA和多酚体系的组装行为的影响。采用荧光光谱和等温滴定量热法探究多酚与GLA之间的相互作用机制。结果显示：TA、EGCG在一定浓度下均可与GLA发生组装形成多酚-GLA纳米复合物,且随着pH值的变化,体系透光率可实现可逆转变。荧光光谱结果分析发现3 种多酚均可以和GLA形成多酚-GLA复合物导致GLA内源荧光的猝灭,猝灭机制为静态猝灭。等温滴定量热法表明TA和GLA结合的主要作用力为氢键和范德华力,而EGCG和GLA间的相互作用主要为静电相互作用。     

水凝胶封装细胞研究进展

近年来,活细胞广泛应用于组织工程、细胞治疗等领域。为了保证活细胞在应用过程中的活性与功能完整性,在细胞表面构建保护性外壳的细胞封装策略应运而生。细胞封装可以避免免疫细胞、抗体、酶等物质与细胞的直接接触,同时保证氧气、营养物质、代谢物等一些小尺寸物质的自由交换。水凝胶因其与细胞基质相似且可形成3D结构模拟细胞微环境而被广泛用于细胞封装。本文首先对细胞封装进行了简单介绍,随后在多细胞封装中重点介绍了木质纤维素基水凝胶在细胞封装中的应用;在单细胞封装中从层层（LbL）自组装、接枝到表面（grafting to）和从表面接枝（grafting from）的3种方法,分别阐述了水凝胶壳层对细胞活性与功能特性的影响。最后讨论了水凝胶封装细胞未来发展方向与前景,希望能为医药食品等领域活细胞的储存及应用提供参考。     

多酚的功能性质及与蛋白质、多糖相互作用研究进展

多酚是具有多种化学结构的多相分子群,具有很强的抗氧化性、抗菌性以及预防慢性疾病的能力,在食品和医疗领域具有广泛的应用价值。多酚由于含有多个酚羟基基团使其化学稳定性差,生物利用度低,在功能性食品中的应用受到了限制。蛋白质、多酚、多糖相互作用所形成的复合结构能够有效地提高食品的感官品质以及各生物大分子的功能特性。本文对多酚的结构与功能之间的关系,多酚与蛋白质、多糖三者相互作用的机理,多酚对二者功能性质及对改善乳化液性质的影响,进行了综述,以期为多酚在食品工业中的应用提供理论参考。     

内源多酚对松仁各组分蛋白理化性质、功能特性和结构的影响

以松仁粕（pine kernel meal，PKM）和脱酚松仁粕（dephenolized pine kernel meal，DPKM）为原料，利用碱溶酸沉法和Osborne分级法分别提取分离蛋白（protein isolates，PI）、球蛋白（globulin，Glo）、清蛋白（albumin，Alb）和谷蛋白（gluten，Glu），研究内源多酚对松仁各组分蛋白理化性质、功能特性和结构的影响。结果表明：脱酚处理后多酚含量、灰分以及碳水化合物显著降低，但蛋白质含量显著提高（P＜0.05）。DPKM各组分蛋白的总巯基含量、游离巯基含量显著高于PKM（P＜0.05），二硫键含量和表面疏水性均降低。与PKM相比，DPKM各组分蛋白的溶解性、乳化稳定性、起泡性、起泡稳定性显著提高，乳化性降低（P＜0.05）。脱多酚改变了松仁蛋白的二级结构，PKM与DPKM均有典型的蛋白吸收峰，并在酰胺I带和酰胺II带的位置发生偏移。DPKM各组分蛋白质β-折叠占总空间结构百分比增加，而α-螺旋、β-转角和无规卷曲结构相对含量降低。荧光光谱显示多酚物质对PI、Alb和Glu都有荧光猝灭作用，但对Glo影响不显著。脱多酚显著影响了松仁各组分蛋白的结构和性质，可以根据应用目的选择处理方式。     

基于铁蛋白纳米笼构建传感元件及其在食品检测中的研究进展

铁蛋白(ferritin)是由24个亚基自组装而成的中空笼形结构蛋白,具有良好的水溶性、稳定性、生物相容性和可逆自组装特性。在生物体内,铁蛋白在铁的吸收、转运、氧化和贮存中扮演重要角色,具有调节体内铁代谢平衡的功能。近年来,由于铁蛋白具有纳米尺度的笼形结构,而且容易通过化学和生物等方法进行结构改造和修饰,使得其被广泛用于检测传感元件的构建。该文对铁蛋白分子的结构与功能进行简要介绍,总结了铁蛋白在构建检测传感元件中的2种基本策略,并重点回顾了基于铁蛋白传感元件在食品真菌毒素、重金属离子、病毒、过氧化氢等有毒有害物质检测中的研究进展,以期为铁蛋白在食品检测领域的应用提供研究思路。     

植物多酚与食品蛋白质的相互作用

近年来食品中多酚与蛋白质的相互作用是食品化学领域的研究热点之一。蛋白质是食品中的重要组分,其结构和功能特性对食品品质具有重要影响。植物多酚具有抗氧化、抑菌等生物活性,它能够以氢键、疏水相互作用、共价键等方式与蛋白质发生结合,从而影响蛋白质的性质。文中主要综述了多酚与蛋白质的相互作用方式,二者相互作用对蛋白质的结构和功能特性以及对多酚生物活性的影响,以期为多酚在食品中的应用和改善蛋白质的功能特性提供参考。     

基于二维过渡金属碳化物的超疏水电磁屏蔽织物的制备及性能

超疏水电磁屏蔽材料具有优异的电磁屏蔽性能、自清洁性、高导电性、高耐久等性能,在人体和电子设备电磁防护中应用前景广阔。基于过渡金属碳化物（MXene）结合低表面能物质聚二甲基硅氧烷（PDMS）,采用简单的浸渍法制备了超疏水电磁屏蔽织物。结果表明,二维片状结构的MXene在涤纶织物（PET）表面均匀分布并构建了导电网络和微观粗糙结构,有利于实现超疏水电磁屏蔽协同性能。基于MXene制备的超疏水涤纶织物电磁屏蔽效能可达34 dB,水接触角可达156°,对橙汁、可乐等液体表现出拒液防污性,显示出优异的超疏水电磁屏蔽性能。     

Enumeration of total aerobic bacteria and Escherichia coli in minced meat and on carcass surface samples with an automated most-probable-number method compared with colony count protocols

An automated most-probable-number (MPN) system for the enumeration of total bacterial flora and Escherichia coli was compared with plate count agar and tryptone-bile-glucuronide (TBX) and ColiID (in-house method) agar methodology. The MPN partitioning of sample aliquots was done automatically on a disposable card containing 48 wells of 3 different volumes, i.e., 16 replicates per volume. Bacterial growth was detected by the formation of fluorescent 4-methylumbilliferone. After incubation, the number of fluorescent wells was read with a separate device, and the MPN was calculated automatically. A total of 180 naturally contaminated samples were tested (pig and cattle carcass surfaces, n = 63; frozen minced meat, n = 62; and refrigerated minced meat, n = 55). Plate count agar results and MPN were highly correlated (r = 0.99), with log MPN = -0.25 + 1.05 x log CFU (plate count agar) (n = 163; range, 2.2 to 7.5 log CFU/g or cm2). Only a few discrepancies were recorded. In two samples (1.1%), the differences were > or = 1.0 log; in three samples (1.7%), the differences were > or = 0.5 log. For E. coli, regression analysis was done for all three methods for 80 minced meat samples, which were above the limit of detection (1.0 log CFU/g): log MPN = 0.18 + 0.98 x log CFU (TBX), r = 0.96, and log MPN = -0.02 + 0.99 x log CFU (ColiID), r = 0.99 (range, 1.0 to 4.2 log CFU/g). Four discrepant results were recorded, with differences of > 0.5 but < 1.0 log unit. These results suggest that the automated MPN method described is a suitable and labor-saving alternative to colony count techniques for total bacterial flora and E. coli determination in minced meat or on carcass surfaces.     

Recovery of Escherichia coli Biotype I and Enterococcus spp. during refrigerated storage of beef carcasses inoculated with a fecal slurry.

Three beef front quarters/carcasses were inoculated with a slurry of cattle manure. During storage at 4 degrees C, two sponge samples from each of three sites (i.e., 100 cm2 from each of two fat surfaces and 100 cm2 from a lean surface) were taken from each of the three carcasses on days 0, 1, 3, 7, and 10 after inoculation. The initial numbers of Escherichia coli averaged 2.0 log10 CFU/cm2 (1.21 to 2.47 log10 CFU/cm2) using the Petrifilm method and 2.09 log10 most probable number (MPN)/cm2 (0.88 to 2.96 log10 MPN/cm2) using the MPN method. The initial numbers of enterococci averaged 3.34 log10 CFU/cm2 (3.07 to 3.79 log10 CFU/cm2) using kanamycin esculin azide agar. In general, an appreciable reduction in the numbers of E. coli occurred during the first 24 h of storage; for the Petrifilm method an average reduction of 1.37 log10 CFU/cm2 (0.69 to 1.71 log10 CFU/cm2) was observed, and for the MPN method an average reduction of 1.52 log10 MPN/cm2 (0.47 to 2.08 log10 MPN/cm2) was observed. E. coli were not detected (<-0.12 log10 CFU/cm2) using Petrifilm on day 7 of the storage period on two (initial counts of 1.21 and 2.29 log10 CFU/cm2) of the three carcasses. However, viable E. coli cells were recovered from these two carcasses after a 24-h enrichment at 37 degrees C in EC broth. Viable E. coli cells were detected at levels of -0.10 log10 CFU/cm2 on the third carcass (initial count of 2.47 log10 CFU/cm2) after 7 days at 4 degrees C. No significant difference in recovery of viable cells was observed between the MPN and Petrifilm methods on days 0, 1, and 3 (P > 0.05). However, viable E. coli cells were recovered from all three carcasses by the MPN method on day 7 at an average of -0.29 log10 MPN/ cm2 (-0.6 to -0.1 log10 MPN/cm2). On day 10, viable cells were recovered by the MPN method from two of the three carcasses at -0.63 and -0.48 log10 MPN/cm2 but were not recovered from the remaining carcass (<-0.8 log10 MPN/cm2). Similar to E. coli, the greatest reduction (average of 1.26 log10 CFU/cm2, range = 1.06 to 1.45 log10 CFU/cm2) in the numbers of enterococci occurred during the first 24 h of storage. Because of higher initial numbers and a slightly slower rate of decrease, the numbers of Enterococcus spp. were significantly higher (P < 0.017) than the numbers of E. coli Biotype I after 3, 7, and 10 days of storage. These results suggest that enterococci may be useful as an indicator of fecal contamination of beef carcasses.     

Comparison of different most-probable-number methods for enumeration of Listeria in poultry

To estimate levels of Listeria spp. in poultry and to select the most appropriate enumeration method for routine analysis, 40 naturally contaminated retail chicken carcasses were tested in Ponferrada (León, N.W. Spain) using the direct plate count technique and various most-probable-number (MPN) designs (UVM I [University of Vermont modified Listeria enrichment broth], Fraser enrichment broth, or both were used in 3-, 5-, and 10-tube MPN techniques). MPN estimation was obtained from the number of tubes with Listeria confirmed (after streaking on PALCAM and modified Oxford agars: "true" MPN) and from the number of dark Fraser broth tubes ("predictive" MPN). Samples were analyzed in duplicate. Low levels of Listeria were found (< 110 CFU/g). The direct plate count technique was totally ineffective for enumerating Listeria in poultry. The single-step (UVM I) and the two-step (UVM I-Fraser) MPN methods gave comparable estimations and a low number of significantly discrepant predictions. Using a single-step method with Fraser broth, lower true MPNs were obtained. The number of tubes used (3, 5, or 10) did not have a substantial influence on the results. Similar estimations, highly correlated (r = 0.538 to 0.968; P < 0.001), were found with (true MPN) and without (predictive MPN) plating confirmation when using the two-step MPN method. The statistical evaluation of the differential character of Fraser broth as part of the two-step MPN method showed high sensitivity (87.5 to 92.5%), specificity (95.2 to 98.6%), efficiency (94.2 to 97.6%), and predictive values (73.6 to 89.9% for a positive test and 98.0 to 98.9% for a negative test). Taking into account these results, we suggest the convenience of using a 3- or 5-tube two-step (UVM I-Fraser) MPN method with estimations obtained from the number of tubes with darkening, without confirmation, in order to achieve great savings in time and money.     

Efficient removal of heavy metal ions from aqueous systems with the assembly of anisotropic layered double hydroxide nanocrystals@carbon nanosphere

We report on the efficient removal of heavy metal ions from simulated wastewater with a nanostructured assembly. The nanoassembly was obtained via direct assembling the performed anisotropic layered double hydroxide nanocrystals (LDH-NCs) onto the surface of carbon nanospheres (labeled as LDH-NCs@CNs). It was found that the maximum adsorption capacity of the nanoassembly toward Cu(2+) was ～ 19.93 mg g(-1) when the initial Cu(2+) concentration was 10.0 mg L(-1), displaying a high efficiency for the removal of heavy metal ions. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Cu(2+) removal was found to follow pseudo-second-order rate equation. Furthermore, the as-prepared building unit of the assembly, including LDH-NCs, CNs, and the assembly, as well as Cu(2+)-adsorbed assembly, were carefully examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), nitrogen sorption measurements, and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Cu(2+) removal with the assembly of LDH-NCs@CNs was proposed. Comparison experiments show that the adsorption capacity of the resulting LDH-NCs@CNs assembly was much higher than its any building unit alone (CNs or LDH-NCs), exhibiting the deliberation of the assembly on water decontamination. This work provides a very efficient, fast and convenient approach for exploring promising nanoassembly materials for water treatment.     

Detection, isolation and enumeration of Yersinia enterocolitica from raw pork

The methods available for the isolation of Yersinia enterocolitica from foods are generally considered to be less than optimal, and methods for estimation of numbers are lacking. Such methods are needed to understand better the significance of foodborne yersiniosis and to provide data for exposure assessment. We describe a method for the detection and enumeration of Y. enterocolitica containing the pYV virulence plasmid (YeP+) in samples from pork surfaces. The method uses a multiplex PCR targeting the ail and virF genes to detect Y. enterocolitica after incubation of surface swabs in Yersinia enrichment broth according to Ossmer. Enumeration was achieved by adapting the enrichment to a most probable number (MPN) method format. A presumptive result was available within 24 h of sample receipt, and YeP+ isolates were confirmed within four days. The presence/absence and MPN methods were evaluated in a pilot survey of 34 packs of raw pork meat purchased from retail outlets in Christchurch, New Zealand. YeP+ was detected by PCR on meat from 32% of the packs, and YeP+ isolates were obtained from 18% of the samples. YeP+ were present at numbers ranging from 0.30 to 5.42 MPN/cm(2). This improved method for the detection and enumeration of YeP+ from meat samples can be used for microbiological surveys to obtain data for assessments of consumer exposure to virulent Y. enterocolitica, and in outbreak investigations.     

乳酸菌生物膜形成调控及在食品中的应用研究进展

乳酸菌生物膜是乳酸菌为了应对不良环境而聚集形成的一种状态,在许多情况下乳酸菌都是以生物膜的形式存在,因此有必要加深对乳酸菌生物膜的了解和研究。本文综述了乳酸菌生物膜的形成,碳源、金属离子、pH值、抗生素、有害菌和非生物表面对乳酸菌生物膜的影响,以及多种基因对乳酸菌生物膜的调控作用,并介绍了乳酸菌生物膜在食品抑菌和发酵中的应用情况,以期为乳酸菌生物膜今后的形成调控研究和在食品工业中的应用提供参考。     

Microbiological quality of fresh-squeezed orange juice and efficacy of fruit surface decontamination methods in microbiological quality

The aims of this study were to evaluate the microbiological quality of fresh-squeezed orange juice and to reduce the microbial population by using various chemical and physical fruit surface decontamination methods. In the first step of the study, polyethylene-bottled fresh-squeezed orange juice samples purchased in Ankara, Turkey, were examined. The average aerobic plate count (APC) and coliform count (CC) varied within the ranges of 3 to 5 log CFU/ml and 1 to 4 log MPN/ml, respectively. Ten of 60 samples contained various levels of Escherichia coli, while Salmonella spp. and E. coli O157:H7 were not detected in any of the samples. Comparing the efficacy of various fruit surface decontamination methods on microbial population of oranges, the best results were obtained following two applications of submersion in boiling water and 5% H(2)O(2) solution for both the uninoculated and inoculated samples. Orange juice samples obtained from surface-inoculated and decontaminated oranges were also examined. We showed that about 17.4% of the E. coli population was transferred to orange juice after extraction, indicating the separation of microbial contaminants from fruit peel during extraction. Finally, the levels of microbial contamination occurred throughout the extraction process on the inner surfaces of a commercial juice extractor at one of the sale points investigated. Significant (P < 0.05) increases in the APC and CC were determined in surface samples of the extractor after the extraction. Surface decontamination and extraction are critical steps in fresh juice production for preventing microbial contamination. Immersion in boiling water for 0.5 min, without using any chemicals, can be offered as an effective method to reduce microbial population on orange surfaces.     

Proteins and protein-rich biomass as environmentally friendly adsorbents selective for precious metal ions

Proteins exhibit specific interactions with various metal ions, which play important roles in a living cell. Here, we found that various proteins selectively adsorbed precious metal ions at a wide range of pH values. Studies on protein sequences and on synthesized peptides revealed that a histidine-containing sequence had specific interactions with precious metal ions (Au3+ and Pd2+). We then investigated a few types of protein-rich biomass as adsorbents for precious metal ions. In the presence of various transition metal ions, Au3+ and Pd2+ were also selectively adsorbed onto the biomass tested. The bound precious metal ions were recovered by aqua regia after charring the metal-bound biomass. Finally, we demonstrated the successful recovery of Au3+ and Pd2+ from a metal refining solution and a metal plating waste using the biomass. We propose an environmentally friendly recycling system for precious metal ions using protein-rich biomass.     

葡萄酒金属破败及防治

介绍了降低葡萄酒中金属离子含量的方法及具体操作,处理对改善酒质、提高稳定性起到良好作用.     

大肠菌群MPN计数法与CFU计数法相关性初探

大肠菌群是常见且重要的食品质量评价指标。如今,大肠菌群检验方法和各类产品国家限量标准值都存在MPN、CFU两种计数单位并行的现象,结合两种技术方法的原理与作者多年从事食品检验的经验,对MPN单位与CFU单位的相关性进行初步探讨。