The methionine precursor dl-2-hydroxy-(4-methylthio)butanoic acid protects intestinal epithelial barrier function

dl-2-hydroxy-(4-methylthio)butanoic acid (HMTBA) is a source of dietary methionine (Met) that is widely used in poultry nutrition. We have previously shown that HMTBA is preferentially diverted to the transsulfuration pathway, which gives antioxidant metabolites such as taurine and glutathione. Therefore, here we hypothesize that this Met source can protect epithelial barrier function in an in vitro model of intestinal inflammation of Caco-2 cells. The results show that HMTBA prevents the increase in paracellular permeability induced by H₂O₂ or tumour necrosis factor-α. This effect can be attributed to the increased production of taurine and reduced glutathione. Similar results were obtained for dl-Met, although the protective role of the amino acid was less pronounced than that of the hydroxy analogue. In conclusion, the diversion to the transsulfuration pathway means that this Met precursor is of greater value than previously thought, due to its capacity to improve intestinal homeostasis and the quality of poultry products destined for human consumption.     

超高浓酿造下抗葡萄糖阻遏啤酒酵母的筛选

根据高浓发酵下(16°P)发酵度的高低,挑选下面啤酒酵母C12作为出发菌株。经过2-去氧-D-葡萄糖的定向驯养、抗性平板分离初筛以及复筛验证等步骤,筛选出一株抗葡萄糖阻遏效应的菌株CM23。将该菌株在18°P麦汁15℃条件下进行3L的EBC小型啤酒发酵实验并测定发酵指标。结果表明:与出发菌株相比,CM23的降糖速度提高了37%,达到1.8°P/d,真正发酵度达到66%,且双乙酰还原能力以及啤酒中主要风味物质含量基本不变。CM23是一株具有工业应用前景的啤酒超高浓酿造酵母菌株。     

Characterization of starter-free Queso Fresco made with sodium-potassium salt blends over 12 weeks of 4°C storage

Development of reduced-sodium cheese to meet the demands of consumers concerned about sodium levels in their diet is challenging when a high-moisture, higher pH, fresh cheese, such as Queso Fresco (QF), depends on its NaCl salt content to obtain its signature flavor and quality traits. This study evaluated the effects of different Na-K salt blends on the compositional, sensorial, microbial, functional, and rheological properties of QF stored for up to 12 wk at 4°C. Queso Fresco curd from each vat was divided into 6 portions and salted with different blends of NaCl-KCl (Na-K, %): 0.75-0.75, 1.0-0.5, 1.0-1.0, 1.0-1.3, 1.0-1.5, and 2.0-0 (control). Within this narrow salt range (1.5 to 2.5% total salt), the moisture, protein, fat, and lactose levels; water activity; pH; and the textural and rheological properties were not affected by salt treatment or aging. The total salt, sodium, potassium, and ash contents reflected the different Na-K ratios added to the QF. Total aerobic microbial count, overall proteolysis, the release of casein phosphopeptides, and the level of volatile compounds were affected by aging but not by the salt treatment. Only the 1.0-1.3 and 1.0-1.5 Na-K cheeses had sensory saltiness scores similar to that of the 2.0-0 Na-K control QF. Loss of free serum from the cheese matrix increased steadily over the 12 wk, with higher losses found in QF containing 1.5% total salt compared with the higher Na-K blends. In conclusion, KCl substitution is a viable means for reduction of sodium in QF resulting in only minor differences in the quality traits, and levels of 1.0-1.3 and 1.0-1.5 Na-K are recommended to match the saltiness intensity of the 2.0-0 Na-K control. The findings from this study will aid cheese producers in creating reduced-sodium QF for health-conscious consumers.     

Electro-conductivity,bioactivity and UV protection of graphene oxide-treated cellulosic/polyamide fabric using inorganic and organic reducing agents

Here, graphene oxide (GO) was treated on the cellulosic/polyamide fabric reduced with various inorganic and organic compounds and compared the color changes, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, electrical resistivity, antibacterial/antifungal and ultraviolet protection properties. The graphite oxide was first synthesized using graphite and sonicated to obtain GO. It was then dissolved in distilled water along with cetyltrimethylammonium bromide (CTAB) to prepare a stable solution for long-time adsorbing more and uniform GO on cellulosic/polyamide fabric through exhaustion method. The GO-treated fabric was reduced to reduced graphene oxide (rGO) with inorganic and organic reducing agents including sodium dithionite with and without sodium hydroxide and dopamine hydrochloride at various temperatures. More fabricated GO reduced to rGO at higher temperature using dopamine produced lower electrical resistance. The antimicrobial activities of various samples were tested against two Gram-negative bacteria, E. coli and P. aeruginosa, two Gram-positive bacteria, S. aureus and E. faecalis and one eukaryotic fungus C. albicans. Ultraviolet protection was examined through reflectance spectra showed no UV transmittance from most of the treated fabrics. Further, CTAB was effective to load more GO on the fabric improved electrical resistance and higher antibacterial properties using both reducing agents.     

SPS措施影响中国禽肉出口的实证研究

基于1996—2011年间中国与日本、德国和沙特阿拉伯等主要禽肉进口国(地区)的面板数据,运用引力模型修正贸易零值的方法分析了SPS措施对中国禽肉产品出口的影响程度。研究表明,中国禽肉出口除了受进出口GDP变动、贸易距离、进口国关税等因素影响,还受到SPS措施的影响,国外红霉素最大残留量(MRLs)每严格1ppm,中国禽肉出口量就要减少0.408%。推进禽肉生产标准和发达国家标准接轨、实施严格的追溯制度、控制兽药残留水平是中国禽肉出口应对SPS措施的有效策略。     

啤酒酵母中还原型谷胱甘肽清除自由基能力的研究

选用啤酒酵母为原料,采用热水浸提提取还原型谷胱甘肽(GSH),经过高速离心分离、阳离子交换树脂纯化、等电点沉淀及真空浓缩干燥制备还原型谷胱甘肽。采用1,1-二苯基-2-苦肼基(DPPH)自由基反应体系,抗氧化性物质抗坏血酸作为参照物,根据DPPH·体系吸光值的变化研究GSH清除自由基的能力,DPPH·反应体系为5mL0.0817mmol/L DPPH·溶液+5mL样品溶液,反应时间30min。考察了不同浓度GSH和抗坏血酸与DPPH·自由基清除率的关系。结果表明,GSH比抗坏血酸抗氧化能力差一些,但GSH清除DPPH自由基能力与其浓度呈明显的量效关系,因此,啤酒酵母GSH有重要的抗氧化开发价值。     

食品中还原糖含量测量的不确定度评估

根据JJF1059-999《测定不确定度的评定与表示》和GB／T5009．7——2003食品中还原糖含量的测定原理，建立不确定度的数学模型。系统分析并计算食品中还原糖测量全过程的不确定度各分量、结果标准不确定度及扩展不确定度．此方法适用于评估食品中还原糖含量的不确定度。     

四探针Mapping自动测试仪中电阻率温度系数的规范化拟合多项式的应用

本文回顾了单晶硅及扩散硅的电阻率温度系数(TCR)的实验结果,认为美国ASTM的TCR曲线是比较完整,确切的.利用我们开发的规范化多项式拟合方法,可将它表示成五阶多项式.将它存入具图像识别四探针定位功能自动测试系统的计算机中后,可以立即得到折合到23℃的硅单晶断面的电阻率分布.本文阐述了规范化拟合的原理,给出了单晶硅的TCR的拟合结果.     

The Loss of Hydrophobic Polypeptides during Fermentation and Conditioning of High Gravity and Low Gravity Brewed Beer

The object of this study was to investigate the loss of hydrophobic polypeptides, which are important for foam quality and stability in finished beer. Loss of hydrophobic polypeptide due to fermenter foaming occurs during transfer of fermented wort since a gradient of hydrophobic polypeptides towards the surface is created during fermentation. Due to higher polyphenol levels in high gravity (20°Plato) wort, more hydrophobic polypeptides are lost due to cold break (cold trub) precipitation compared to low gravity (12°Plato) wort. Another important factor affecting the loss of hydrophobic polypeptides could be proteinase A activity during fermentation, especially in high gravity fermentation where the yeast is exposed the higher stress. During high gravity fermentation, where osmotic pressures are higher, ethanol levels become greater, and nitrogen‐carbohydrate ratios are lower, more proteinase A is released by the yeast. This release of proteinase A into fermenting wort could have implications for the foam stability of the finished product.     

Effects of alfalfa particle size and specific gravity on chewing activity, digestibility, and performance of Holstein dairy cows

Two experiments were carried out to test the effects of alfalfa particle size and functional specific gravity (FSG) on chewing activity, digestibility, rumen kinetics, and production of lactating dairy cows fed corn silage based rations. In experiment 1, water-holding capacity (WHC), insoluble dry matter, hydration rate, and FSG changes were determined in alfalfa hay (varying in particle size) and corn silage. Reduction of particle size increased bulk density, FSG, and the rate of hydration, and decreased WHC of alfalfa. In experiment 2, 9 midlactation Holstein dairy cows fed total mixed rations containing 3 sizes of alfalfa hay (with geometric mean 7.83, 4.04, and 1.14 mm) were used in a replicated 3 x 3 Latin square design. The diets contained 20, 20, 35, 7, 7.5, 10, 0.3, 0.1, and 0.1% of DM alfalfa, corn silage, barley, soybean meal, beet pulp, wheat bran, dicalcium phosphate, vitamin premix, and salt, respectively. The geometric means (GM) of rations were 3.34, 2.47, and 1.66 mm in long, medium, and fine alfalfa treatments, respectively. Reduction of particle size increased daily NDF intake (kg), but decreased the proportion of physically effective factor (pef) and physically effective NDF (peNDF) in the ingested rations. Reduction of particle size increased the FSG of rations and intake of DM but reduced digestibility of NDF and ash. Reduction of particle size decreased ruminal mean retention time (RMRT), but increased the ruminal particulate passage rate. Milk and FCM yield were not affected by treatments. The rumen pH, total chewing activity, rumination, eating time, and milk fat were reduced as particle size decreased, but milk protein increased. This study showed that reduction of forage particle size increased bulk density, FSG, and hydration rate of alfalfa and was the most influential factor affecting DMI, milk composition, and chewing behavior. Reduction of forage particle size had minimal impact on digestibility and milk production.