Highly Efficient and Fully Solution‐Processed White Electroluminescence Based on Fluorescent Small Molecules and a Polar Conjugated Polymer as the Electron‐Injection Material

Highly efficient and fully solution‐processed white organic light‐emitting diodes (WOLEDs) based on fluorescent small molecules and a polar conjugated polymer as electron‐injection material are reported. The emitting layer in the WOLEDs is a blend of new blue‐, green‐, and red‐fluorescent small molecules, with a blending ratio of 100:0.4:0.8 (B/G/R) by weight, and a methanol/water soluble conjugated polymerpoly[(9,9‐bis(30‐(N,N‐dimethylamino)propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene)] (PFN) acts as the electron‐injection layer (EIL). All the organic layers are spin‐coated from solution. The device exhibits pure white emission with a maximum luminous efficiency of 9.2 cd A^?1 and Commission Internationale d'Eclairage Coordinates of (0.35, 0.36). PFN acting as the EIL material plays a key role in the improvement of the device performance when used in solution‐processed small‐molecule WOLEDs.     

Quantification of Listeria monocytogenes in minimally processed leafy vegetables using a combined method based on enrichment and 16S rRNA real-time PCR

Modern lifestyle markedly changed eating habits worldwide, with an increasing demand for ready-to-eat foods, such as minimally processed fruits and leafy greens. Packaging and storage conditions of those products may favor the growth of psychrotrophic bacteria, including the pathogen Listeria monocytogenes. In this work, minimally processed leafy vegetables samples (n = 162) from retail market from Ribeirão Preto, São Paulo, Brazil, were tested for the presence or absence of Listeria spp. by the immunoassay Listeria Rapid Test, Oxoid. Two L. monocytogenes positive and six artificially contaminated samples of minimally processed leafy vegetables were evaluated by the Most Probable Number (MPN) with detection by classical culture method and also culture method combined with real-time PCR (RTi-PCR) for 16S rRNA genes of L. monocytogenes. Positive MPN enrichment tubes were analyzed by RTi-PCR with primers specific for L. monocytogenes using the commercial preparation ABSOLUTE™ QPCR SYBR^® Green Mix (ABgene, UK). Real-time PCR assay presented good exclusivity and inclusivity results and no statistical significant difference was found in comparison with the conventional culture method (p < 0.05). Moreover, RTi-PCR was fast and easy to perform, with MPN results obtained in ca. 48 h for RTi-PCR in comparison to 7 days for conventional method.     

活性干酪乳酸菌再制干酪的工艺研究

建立了一种在再制干酪的加工过程中添加活性乳酸菌,生成新型再制干酪的方法,研究了不同形态的活性乳酸菌在再制干酪中的生存特性,和新工艺对再制干酪结构与质构特性的影响。通过对乳化后的再制干酪基料采取不同的搅拌与冷却方式,确定了加工过程中加入活性乳酸菌的关键工艺参数。实验表明,干酪经过乳化后,在60℃下保温30min,加入乳酸菌,然后冷却至4℃,干酪中的乳酸菌可达到109cfu/g,干酪于4℃贮藏30d后,活菌数密度保持稳定。采用该种方法生产的再制干酪与采用传统工艺生产的再制干酪在质构特性方面除硬度增加外,其他质构特性无明显差异变化。质构参数的这种差异变化主要是由新工艺的冷却方式引起的。再次搅拌工艺保持了干酪微观结构的一致性。     

番茄红素——新型加工肉制品添加剂

番茄红素是一种具有抗氧化性的天然色素,而且对人体有一定的保健功效。番茄红素这种脂溶性色素具有作为加工肉制品添加剂的潜力。作者对番茄红素在自然界中及人体内的分布,番茄红素的理化性质以及抗氧化性进行了综述,同时介绍了近年来番茄红素在保健功效和在加工肉类制品中应用的研究进展。     

Application of Kubelka–Munk analysis to the study of translucency in fresh-cut tomato

In order to assess the development of translucency in fresh-cut tomato (Lycopersicum esculentum cv. Belissimo) during refrigerated storage, two experiments were conducted. In the first one, tomato slices obtained from fruits at breaker and at red stage were stored at 5 ± 0.5 °C and monitored at regular intervals for 9 days. In the second one, slices obtained from fruits at the light-red stage were stored at 5 ± 0.5 °C, 9 ± 0.7 °C and 13 ± 0.7 °C for 4 days. Intact (control) fruits were stored at the same conditions and sliced immediately before the evaluations. In both experiments, translucency was assessed using Kubelka–Munk analysis and through visual evaluation using a scale from 0 to 4. The translucency of cut tomato slices increased during storage in both experiments. Fruits at red stage got translucent faster than fruits at breaker stage and the intensity of translucency was also higher for more ripe fruit. The storage temperature did not influence significantly the development of translucency, indicating that the water soaking of the pericarp tissue is not a result of chilling injury. The K/S (absorption coefficient/scattering coefficient) ratio increased during storage for cut fruits and remained practically constant for intact fruits, reflecting the effects of treatment observed visually. Additional experiments indicated that the removal of the locular gel combined or not with washing and drying the slice cut surface inhibited the development of translucency.

Industrial relevance

The development of translucency is a common alteration in the appearance of fresh-cut fleshy tissue after processing, which renders the product unappealing for consumption. It is of interest for the fresh-cut industry to be able to assess the development of translucency and then evaluate the effect of different procedures in its occurrence and intensity. This paper presents the use of Kubelka–Munk analysis, a technique of widespread use in other fields like printing and painting, to assess the development of translucency in sliced tomato and to study how this process is affected by storage temperature and maturity stage of the fruit.     

绞股蓝热处理产物中活性成分的纯化与鉴定及其对A549细胞的抑制活性

目的:提取、分离、鉴定绞股蓝热处理产物中抑制肺癌A549细胞的活性成分。方法:绞股蓝叶在温度125℃、压力0.24MPa条件下,加热处理3h,用80%乙醇加热回流提取3h,利用活性跟踪方法,通过大孔树脂HP-20及反相柱等分离手段,分离抑制肺癌A549细胞的活性成分,并用核磁共振波普(1H-NMR、13C-NMR)、电喷雾质谱(ESI-MS)等数据鉴定有效成分。结果:绞股蓝热处理产物中分离得到2个达玛烷类皂苷,分别为绞股蓝皂苷Gypenoside L和Gypenoside LI,而且它们对肺癌A549细胞具有质量浓度依赖性的抑制活性(P<0.05),其IC50值分别为(48.43±1.33)μg/mL和(34.35±0.88)μg/mL。结论:热处理绞股蓝产物可提高对肺癌A549细胞的抑制作用,其中有效成分为达玛烷类皂苷Gypenoside L和Gypenoside LI。     

Evaluation of minimally processed salads commercialized in Portugal

During the last decades food borne outbreaks associated with consumption of raw vegetables have been increasing and green leafy vegetables seem to be the most frequently implicated products.In order to determine the microbial quality and the incidence of the major food borne pathogens in Minimally Processed (MP) salads commercialized in Portugal, a survey was conducted in Lisbon Retail Markets, from July 2007 to August 2008, to determine microbial contamination loads and identify potential pathogenic bacteria.A total of 151 samples were purchased from 2 supermarkets: 38 romaine lettuce, 12 various spinach and 101 mixed salads with three or four different ingredients. The samples were tested for aerobic psychotropic micro-organisms (APM), Enterobacteriaceae, Escherichia coli, Listeria spp., presumptive Bacillus cereus, Aeromonas hydrophila and Clostridium perfringens counts as well as for presence of Salmonella spp., Listeria monocytogenes and E. coli O157. Samples were also evaluated for taste quality.The results showed that APM counts of romaine lettuce and mixed salads had a similar median, respectively, 6.2 and 6.5 log cfu/g and mixed spinach had the highest one (7.6 log cfu/g). The median value found for Enterobacteriaceae was 5.44 log cfu/g. Only four samples showed positive result for E. coli (2.65%) but just one (0.8%) had a slightly higher load of contamination. Although the percentage and levels of contamination loads were low, these mustn’t be ignored, for the reason that the strains in three of the samples belong to VTEC group (1.99%). E. coli O157, Salmonella spp. and C. perfringens weren’t detected in any sample. For the enumeration of Listeria spp., two samples (1.32%) had presence of Listeria innocua and L. monocytogenes had an incidence of 0.66%. A. hydrophila was identified in 11 samples (7.28%), and in 8 of them with considerable counts (>10⁵). Contamination with B. cereus was found in 22.7% of samples analyzed, though in small numbers, which doesn’t represent a major concern to food safety. All isolated strains were assessed for its potential toxin production and it was found that 40% of these strains had this ability. Results from sensory panel showed organoleptic differences in salads during its shelf-life period.     

Near-infrared techniques for fraud detection in dairy products: A review

The dairy products sector is an important part of the food industry, and their consumption is expected to grow in the next 10 years. Therefore, the authentication of these products in a faster and precise way is required for the sake of public health. This review proposes the use of near-infrared techniques for the detection of food fraud in dairy products as they are faster, nondestructive, environmentally friendly, do not require sample preparation, and allow multiconstituent analysis. First, we have described frequent forms of food fraud in dairy products and the application of traditional techniques for their detection, highlighting gaps and counterproductive characteristics for the actual global food chain, as longer sample preparation time and use of reagents. Then, the application of near-infrared spectroscopy and hyperspectral imaging for the detection of food fraud mainly in cheese, butter, and yogurt are described. As these techniques depend on model development, the coverage of different dairy products by the literature will promote the identification of food fraud in a faster and reliable way.     

Anion exchange polymeric sorbent coupled to high-performance liquid chromatography with UV diode array detection for the determination of ten N-nitrosamines in meat products: a validated approach

Among mechanisms and molecules presumably involved in the carcinogenicity induced by meat consumption, the N-nitrosamines (N-NAs) are a class of compounds characteristic of processed meats. In this work, an analytical method for the determination of ten N-nitrosamines (N-nitrosomorpholine, N-nitrosomethylethylamine, N-nitrosopyrrolidine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosodipropylamine, N-nitrosodimethylaniline, N-nitrosodibutylamine, N-nitrosodiphenylamine and N-nitrosodibenzylamine) in fresh meats and meat products was developed, optimised and validated. The method is based on optimised sample purification by solid-phase extraction (anion exchange polymeric sorbent) and separation/detection by high-performance liquid chromatography coupled to UV diode array detection. The validation procedure allowed to ascertaining good analytical performances in terms of sensitivity, selectivity towards interfering compounds, accuracy and robustness. The values obtained for precision (range: 4.3–14.4%) and recovery percentages (range: 80.8–95.1%) were compared to reference values indicated in the Decision No. 657/2002/EC, resulting as compliant. The measurement uncertainty (lower than 14.6%) was satisfactory for each N-NA as well.     

The effect of native and polymerised whey protein isolate addition on surface and microstructural properties of processed cheeses and their meltability determined by Turbiscan

The aim of this paper was to investigate the effect of whey protein isolate (WPI) and polymerised whey protein isolate (WPP) addition on physicochemical properties of processed cheese with partial fat replacement. Surface properties were determined by advancing (θ_a) and receding (θ_r) contact angles, apparent free surface energy (γ_s). Roughness measurements, cheese meltability and Turbiscan Stability Index (TSI) were evaluated by Turbiscan. Higher WPP concentrations produced the more hydrophobic surfaces of the samples. Conversely, increase in WPI addition promoted the hydrophilic cheese surfaces. The effect of roughness was much larger for samples containing WPI. The increase in protein addition caused a decrease in meltability and an increase in stability of cheeses. The optical and confocal images have proved that cheeses with WPP demonstrated more packed and denser structure in comparison to samples with WPI.