Effect of pH on the effectiveness of whey protein/glycerol edible films containing potassium sorbate to control non-O157 shiga toxin-producing Escherichia coli in ready-to-eat foods

Potassium sorbate (PS) (0.5%, 1.0% and 1.5% w/w) was included into whey protein concentrate (WPC)/glycerol (Gly) edible films at pH 5.2 and 6.0. The films inhibited or retarded the growth of Shiga toxin-producing Escherichia coli (STEC) pathogens in both diffusion and barrier tests. Bacterial growth inhibition was dependent on PS content at both pH values. PS release was not affected by pH. Scanning electron microscopy (SEM) was used to analyze the microstructure of the films and gain a better understanding of their optical parameters. Acidic control films (pH 5.2) prepared without PS were the least transparent. SEM micrographs confirmed the greater structural heterogeneity of these films, coinciding with opacity. The incorporation of PS into WPC/Gly films improved transparency and produced a smoother surface than acidic control ones. The utilization of active packaging based on whey proteins and organic acids to control and prevent the dissemination of STEC pathogens may be an effective, safe, ecological and relatively inexpensive alternative to be used in the food packaging industry.     

Effect of thermochromic materials on physical and aging properties of SBS modified asphalt

Abstract

The effects of different types (red, black and blue color) and content (2% and 4%) of thermochromic powders on aging properties of styrene-butadiene-styrene copolymer (SBS) modified asphalt were investigated. Physical properties of the binders (ductility, penetration, viscosity and softening point) were tested before and after thermal-oxidative and ultraviolet radiation aging. The results showed thermochromic powders improved the deformability and weakened the high-temperature performance of SBS modified asphalt to some extent. Thermochromic powders could obviously improve the anti-aging properties of SBS modified asphalt. In addition, SBS modified asphalt with 2% thermochromic materials showed the best aging resistance under all aging modes.     

Development and performance of whey protein active coatings with Origanum virens essential oils in the quality and shelf life improvement of processed meat products

Active coating development for prevention and control of microbial contamination is an extremely challenging technology. In this field, the potential of plant-based compounds to be used as a complement or an alternative to the synthetic preservatives have drawn increasing attention from the food industry.In this study, an active coating containing Origanum virens essential oil (EO-WPC) was applied on the surface of two traditional Portuguese sausages (paínhos and alheiras) during industrial production. For 4 months, both products were regularly monitored for their physicochemical properties and total microbial load. Sensory evaluation was also carried out for each sausage type.The application of the EO-WPC caused little variations on the moisture content and texture profile. Higher acidity and protection against color fading was observed particularly in paínhos, while coated alheiras had a significant reduction of the lipid peroxidation. Inhibition of the total microbial load was observed for both coated sausages, resulting in an extension of the shelf life of approximately 20 and 15 days for paínhos and alheiras, respectively. Sensory analysis revealed an overall positive acceptance. These results support the great potential of O. virens EO to be used as food preservative in processed meat products.     

Effect of fat and salt reduction on the sensory quality of slow fermented sausages inoculated with Debaryomyces hansenii yeast

The inoculation of a Debaryomyces hansenii strain in dry fermented sausages with reduced fat and salt contents was evaluated in terms of chemical, microbial and consumer acceptability. The implantation of the inoculated yeast strain was confirmed by RAPDs of M13 minisatellite. A reduction of 17–20% salt and 10–16% fat content was achieved. These reductions affected the sausage quality by producing an increase in a_w, hardness and chewiness values and a decrease of staphylococci growth. However, D. hansenii inoculation compensated these changes although it was not able to modify neither the hardness of reduced fat batches nor the staphylococci growth decrease. In terms of sensory acceptability, different preferences patterns of consumers were found. Yeast inoculation improved the aroma and taste quality when fat or salt reductions were carried out in dry fermented sausages.     

Influence of emulsifier type on the antifungal activity of cinnamon leaf,lemon and bergamot oil nanoemulsions against Aspergillus niger

Only exiguous data are currently available on the antifungal properties of essential oil (EO) nanoemulsions against spore-forming microorganisms. The aim of this work is to develop physically stable nanoemulsion-based delivery systems for different EOs (cinnamon leaf, lemon, and bergamot), to exploit their antifungal properties against Aspergillus niger. The inhibition of mycelial radial growth and spore germination were used as indicators of antifungal activity of the nanoemulsions, which were prepared at 3 wt% EO, using non-ionic Tween 80 (T80) or anionic whey protein isolate (WPI) (1 wt%) as emulsifiers, and sunflower oil (1 wt%) as ripening inhibitor. The nanoemulsions were physically stable over seven days of accelerated aging at 35 °C.The minimal inhibitory concentration of free cinnamon leaf and of both citrus EOs were 0.35 and 5.50 μg/g, respectively. The encapsulation of cinnamon leaf EO in nanoemulsions significantly enhanced the inhibiting effect against A. niger mycelial growth and spore germination, with respect to the free EO. In contrast, for citrus EOs, the encapsulation in nanoemulsions generally decreased the antifungal activity, likely because of the nanoemulsion acting as a hydrophobic sink for the main constituents of citrus EOs. The emulsifier played a fundamental role in the resulting antifungal activity, with WPI-based nanoemulsions being more effective in inhibiting the mycelial growth and the spore germination of A. niger than T80-based ones. The antifungal action was correlated to the morphological alterations observed in A. niger, such as the loss of cytoplasm in fungal hyphae and hyphal tip. The results of this study show the importance of nanoemulsions design in the development of efficient and stable natural antifungal agents for food applications.     

Effect of pH,temperature and storage time on the stability of bovine myelin basic protein

Bovine central nervous system tissue (CNT) harboring highest levels of the infectious agent for prion diseases, has been banned from food and feed supplies. Effective detection of CNT in excessively processed meat and feedstuffs requires the assay based on a stable marker in CNT as the analyte. Myelin basic protein (MBP), the major central nervous system (CNS) myelin protein, was reported to be detectable up to 115 °C in the literature. This study further investigated the effects of pH, temperature and storage time on the stability of purified bovine MBP (18.5 kDa) in solutions. Purified MBP dissolved in 10 mM PBS was adjusted to pH 3.0, 7.2 and 10.5, respectively. Sample at each pH was subjected to three heat treatments, 100 °C, 121 °C, and 133 °C for 30 min. The unheated and 100 °C heated samples at pH 7.2 were stored at 4 °C for 19 days to study the storage stability of bovine MBP. The immunoreactivity of all samples was examined using indirect non-competitive enzyme-linked immunosorbent assay and immunoblotting with an anti-MBP monoclonal antibody. The protein degradation was observed by analyzing samples using SDS-PAGE. Results show that bovine MBP was most stable at pH 7.2 while the protein was least stable at pH 10.5. MBP started to degrade after heating at 121 °C for 30 min at pH 7.2. Storage up to 19 days at 4 °C did not significantly affect the immunoreactivity of unheated and heated samples. However, unheated MBP samples started to show degradation from day 8 of storage; while no degradation was observed in 100 °C heated samples over the storage time. This study demonstrated that bovine MBP can be a suitable marker for the detection of bovine CNT in highly processed food and feed supplies.     

胶莱盆地莱阳凹陷莱阳组低渗透砂岩储层特征及物性控制因素

以野外露头、岩心观察为基础,综合采用普通薄片、铸体薄片、阴极发光薄片、扫描电镜、物性分析、黏土矿物X射线衍射等多种测试手段,对胶莱盆地莱阳凹陷下白垩统莱阳组碎屑岩储层基本地质特征进行了分析。在此基础上,结合盆地构造活动、沉积特征、成岩特征研究了该碎屑岩储层物性的控制因素,探讨了低渗透砂岩背景下优质储层的形成条件。研究结果表明：胶莱盆地莱阳凹陷莱阳组砂岩以低成分成熟度、中等结构成熟度为特征,孔隙度一般小于10%,渗透率多小于1×10^-3 μm²,为特低孔隙度特低渗透率储层。沉积作用是形成低渗透储层的最根本因素,它决定了后期成岩作用的类型和强度,成岩早期强烈的压实作用和胶结作用对形成低孔隙度低渗透率储层起了决定性作用;优质储层的形成主要受有机酸溶蚀作用、早期碳酸盐胶结作用、绿泥石环边胶结作用和后期构造活动的控制。其中后期构造活动是影响低渗透砂岩中有效储层发育的关键因素,白垩纪末期-新生代的构造抬升使孔隙得以保存,同时构造活动产生的微裂缝不仅可以作为油气储集空间,而且还可以作为油气运移的通道并改善储层的渗滤特征。寻找裂缝性储层是该区下一步油气勘探的方向和突破点。     

三塘湖盆地马朗凹陷牛圈湖—牛东构造带上石炭统火山岩黏土矿物特征及其对储层物性的影响

三塘湖盆地马朗凹陷牛圈湖—牛东构造带上石炭统哈尔加乌组和卡拉岗组发育低孔、特低渗强非均质性火山岩储层.基于黏土矿物类型、含量、赋存状态、分布特征及其成因与转化的系统分析,讨论了黏土矿物对火山岩储层储集物性的影响.上石炭统火山岩储层为低孔、特低渗储层,主要发育气孔、半充填杏仁孔、晶间孔、粒间孔等原生孔隙和微晶溶孔、基质溶...     

渤南洼陷北部陡坡带沙河街组砂砾岩有效储层物性下限及其主控因素

结合研究区测井解释成果和油田试油资料,综合应用分布函数曲线法和试油法,确定了渤海湾盆地渤南洼陷北部陡坡带沙河街组不同深度段的砂砾岩有效储层物性下限,并拟合出物性下限与深度的关系式,在此基础上分析了岩性、沉积相、成岩阶段、地层压力等对砂砾岩有效储层发育的影响。研究结果表明:有效储层物性下限有随埋深增加而逐渐降低的趋势;有利的沉积相带是砂砾岩有效储层发育的关键因素,对储层质量起决定性作用。研究区有效储层主要分布于西部的滑塌浊积扇及中东部近岸水下扇的扇中亚相;其中近岸水下扇的扇中亚相最为有利,其次为滑塌浊积扇。成岩作用也在一定程度上影响有效储层物性。研究区砂砾岩体主要处于中成岩阶段A₁和A₂亚期,对应于有机质热演化的主要生油气阶段,有利于形成次生孔隙,其中溶蚀作用使得深部储层物性变好。研究区地层压力对有效储层物性的影响较小。