Detection of acylated homoserine lactones in gram-negative proteolytic psychrotrophic bacteria isolated from cooled raw milk

Through a mechanism called quorum sensing, bacteria are able to express specific genes in response to population density. Cell-to-cell communication in bacteria is mediated by signal molecules such as acylated homoserine lactones (AHLs). This work aimed to detect AHL production in Gram-negative psychrotrophic bacteria isolated from raw milk. A total of 84.9% of the bacteria were identified as AHL producers eliciting a diversity of responses in the AHL-monitor systems. These results demonstrate that AHL-production is common among psychrotrophic bacteria isolated from milk, and indicate that quorum sensing may play an important role in the spoilage of this product.     

Synthesis and swelling properties of poly[acrylamide-co-(crotonic acid)] superabsorbents

Superabsorbent polymers of acrylamide (AAm)/crotonic acid (CA) were synthesized by foamed polymerization in an aqueous solution of AAm with CA as a comonomer, initiated by an initiator couple of ammonium persulfate and N,N,N′N′-tetramethylethylenediamine. A crosslinking agent N,N′-methylenebisacrylamide, a foaming agent sodium bicarbonate, and a foam stabilizer, a triblock copolymer of polyoxyethylene/polyoxypropylene/polyoxyethylene, were used in the polymerization. The influences of the relative contents of CA, crosslinking agent, and initiator, on the swelling properties of the superabsorbent polymer systems were examined. The superabsorbent polymer synthesized with an AAm/CA ratio of 98:2 by mole, 0.5 wt.% of N,N′-methylenebisacrylamide and 1 wt.% of ammonium persulfate at 250 rpm and 50 °C for 30 min of polymerization time produced the highest water absorption of 211 ± 9 times its dried weight and could absorb water up to 162 ± 4 g g⁻¹ of the dry copolymer within 10 min. The electrochemical reaction for acrylamide–crotonic acid polymerization was investigated by cyclic voltammetry. The anodic current indicated that acrylamide acting as an electron donor whereas crotonic acid performed as an electron receiver, then providing the cathodic current. The diffusion of water into the superabsorbent polymer was non-Fickian (case II and anomalous). Acrylamide–crotonic acid superabsorbents containing various crosslinker concentrations had a water swelling in the range of 79–289 g g⁻¹. The diffusion coefficients varied between 6.9 × 10⁻⁹ and 5.1 × 10⁻⁸ cm² s⁻¹. Adsorption of the basic dye by the superabsorbent was a monolayer evaluated by the Langmuir isotherm. The superabsorbents can thus be used to adsorb cationic dyes in textile industry.     

不同干燥方式下沙丁鱼干燥特性的比较

为了研究不同干燥方式对沙丁鱼干燥特性的影响,采取冷风、热风、微波真空、冷风-微波真空和热风-微波真空5种干燥方式对沙丁鱼进行处理,研究不同干燥方式对沙丁鱼色泽、质构、水分变化、微观结构和干燥后对蛋白质二级结构的影响。结果表明,不同干燥方式对干制鱼肉色泽影响差异显著(p<0.05),微波真空干燥有助于提高鱼肉的亮度,并与鲜肉最为接近,冷风-微波真空在色度方面表现良好;不同干燥方式对质构影响显著(p<0.05),干燥方式中,微波真空干燥方式有降低硬度、咀嚼度;微观结构中热风和冷风处理后的肌肉纤维紧密,冷风-微波真空处理后的肌肉呈现疏松且密集的网状;干燥使得不易流动水大量流失,水分发生迁移,微波真空与热风-微波真空、冷风-微波真空干燥使肌肉纤维疏松;同时,干燥破坏了蛋白质二级结构,使得α-螺旋向β-折叠、无规则卷曲转化,冷风干燥对其二级结构的影响程度最小,结果为沙丁鱼的生产加工提供理论依据。     

肽组学在食源性活性肽研究中应用的进展

肽组学作为食品科学技术领域一个新兴的重要研究方法,正逐渐应用到生物活性肽制备、纯化、结构鉴定以及构效关系研究中,涉及活性肽的定性与定量的各个方面的内容。本文综述了肽组学在食源性活性肽制备工艺优化、特定功能活性的活性肽筛选、活性肽与受体的作用机制以及构效关系等研究的国内外进展,以期为肽组学在活性肽中广泛深入地应用提供参考。     

副溶血性弧菌毒力因子及耐药机制研究进展

副溶血性弧菌是水产品中主要的致病菌之一,既可造成养殖水产品的疾病与死亡,也可引起人类的胃肠炎等疾病,不仅具有潜在的食品安全隐患,也对消费者健康造成潜在危害。该文主要阐述了副溶血性弧菌的毒力因子耐热直接溶血素(thermostable direct hemolysin, TDH)以及分泌系统T3SS1、T3SS2在菌株体内的作用机理,并对副溶血性弧菌产生耐药性的5种机制——产生生物被膜、质粒介导耐药、产生灭活酶或钝化酶类、外排泵主动排出抗菌药物、药物靶点发生改变进行了综述。     

Emulsifying properties of different soy hull pectin polysaccharides and application in mayonnaise

Food Science and Biotechnology - Soy hull pectic polysaccharide (SHPP) is a kind of biological macromolecule prepared from soy hull, which has certain thickening and gel properties. In present...     

膳食脂质肠道消化及吸收的研究进展

膳食脂质作为人类生活中一种必不可少的营养物质来源，为机体提供所需的必需脂肪酸和能量，维持人体正常的生理活动，其中肠道作为脂质最主要的消化场所及特定吸收场所，发挥了重要的作用。该研究在基于脂质肠道消化途径的基础上，从脂质自身形态、蛋白质与脂质相互作用下的形态、脂质构型变化、胆汁盐分泌、胰脂肪酶以及共脂肪酶等多角度论述了影响脂质肠道消化的主要因素，分析了影响脂质消化关键行为的界面作用，从转运因子调节、分子吸收路径以及肠道微生物间接调控吸收三个方面阐述了膳食脂质的肠道吸收机制，为深入开展膳食脂质的功能化修饰、高值化利用、创新性研发提供了理论依据。     

Applicability assessment of a real-time PCR assay for the specific detection of bovine,ovine and caprine material in feedstuffs

A TaqMan real-time polymerase chain reaction (PCR) method was developed for specific detection of bovine, ovine and caprine processed animal protein (PAP) in industrial feedstuffs. The method uses species-specific primers and probes targeting short mitochondrial D-loop sequences, and a positive amplification control based on 18S rRNA gene. The applicability of the real-time PCR protocol was assessed through analysis of 126 industrial feed samples that were manufactured to reproduce rendering processes of commercial feeds destined for farmed animals. The assay successfully classified samples as positive or negative according to the ruminant composition, enabling qualitative detection of banned material in feeds at levels as low as 0.1%. Although the method provides quantitative potential, results suggest that the real quantitative capability of the assay is limited by the existing variability in terms of composition and processing treatments of the feeds, which affect the amount and quality of amplifiable DNA.     

Effect of medium temperature setting on gelling characteristics of surimi from some tropical fish

Effects of setting at 25 °C on textural properties and cross-linking of myofibrillar proteins in surimi produced from threadfin bream (Nemipterus bleekeri), bigeye snapper (Priacanthus tayenus), barracuda (Sphyraena jello) and bigeye croaker (Pennahai macrophthalmus) were investigated. Increase in setting time (0–8 h) resulted in a higher breaking force and deformation for all surimi gels tested (P<0.05). Increased gel strength was associated with increase in non-disulfide bond formation and decreased heavy chain myosin. Proteins underwent degradation during setting; however polymerization occurred to a much higher extent, leading to a strengthened gel matrix. Therefore, setting at 25 °C, for an appropriate time, should be a promising means to improve gelling properties of surimi produced from tropical fish.