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.     

大豆种皮多糖在甘露聚糖酶修饰下力学行为的演变

利用β-甘露聚糖酶限制性水解大豆种皮多糖,探讨不同水解时间对大豆种皮多糖流变性质及凝胶强度的影响。结果表明:随着β-甘露聚糖酶作用时间的延长,多糖粘度有下降趋势;酶修饰对胶凝行为的影响则更复杂,修饰作用表现出时间依赖性,在不同的处理时间,多糖的力学行为给予各自独特的响应,原因可能是酶处理时间不同,从多糖分子中游离出来的单糖及寡糖组分的区别造成了分子间相互作用及对环境响应的差异,进而影响多糖分子的力学行为。     

辽宁沿海城市海鱼和贝类中重金属含量的测定及评价

经微波消解处理样品,采用石墨炉原子吸收光谱法(GFAAS)测定辽宁沿海城市常见海鱼和贝类中镉、铬、铜、铅、铁、锌六种元素的含量。其相对标准偏差(RSD)0.53%～4.01%,加标回收率90.0%～110.0%。结果表明:不同地区、不同鱼贝种类中重金属的分布存在差异,所检测鱼贝类中铬、铜、锌含量低于国家限量标准,部分样品中镉、铅含量超标,但低于暂定每周可耐受摄入量(PTWI)。因此辽宁沿海城市市售所检测的鱼贝类可食用,但仍有必要降低摄入量。     

胡萝卜汁添加对乳化肠食用品质的影响

研究了胡萝卜汁添加对乳化肠色泽、质构特性、保水性以及感官品质的影响。基于最优基础配方,实验通过控制胡萝卜汁的添加量(0%、5%、10%、15%),探索其对于乳化肠食用品质的影响。结果表明:添加胡萝卜汁组与对照组(胡萝卜汁添加量0%)的色差、质构以及感官方面存在显著差异(P0.05)。随着胡萝卜汁添加量的增加,红度值、硬度都呈显著下降趋势,而蒸煮损失、黏聚性和弹性与对照组没有显著差异。胡萝卜汁添加量为10%的样品组的硬度、咀嚼性和胶着性最好,且通过感官评定得知该组各项指标综合评定结果最好,本实验得出10%是胡萝卜汁较优的添加量。     

贮藏温度对大平顶枣品质的影响

为探究贮藏环境对大枣品质的影响,以朝阳大平顶枣为原料,在0℃、4℃、10℃、20℃温度下进行贮藏试验。通过测定贮藏过程中失重率、硬度、还原糖含量、可滴定酸含量的变化。结合低场核磁共振技术测定贮藏中水分的迁移,研究大枣的水分动态s变化的微观过程。结果表明:0℃和4℃低温贮藏能显著延缓大枣硬度的变化,抑制大枣贮藏期间失重率的增加。随着贮藏温度的降低,还原糖含量开始下降的时间延后。贮藏35 d时,0℃贮藏的大枣中可滴定酸含量分别比4℃、10℃、20℃的含量高9.90%、44.10%、54.50%。采用低场核磁共振技术检测大枣中水分迁移情况,测得自由水幅度下降顺序为20℃>10℃>4℃>0℃,温度越高,自由水在贮藏中的损失越多,下降的速率越快,从微观角度初探了大枣贮藏过程中变化机理。     

离子液体1-甲基-3-乙基咪唑四氟硼酸盐和1,2-二甲基-3-乙基咪唑四氟硼酸盐的热力学和电导性质研究

在室温下合成了离子液体1-甲基-3-乙基咪唑四氟硼酸盐([Emim]BF4)和1,2-二甲基-3-乙基咪唑四氟硼酸盐([Dmeim]BF4),通过红外光谱对其进行了结构表征。分别测定了两种离子液体在不同温度下的密度、表面张力、粘度和电导率,发现当咪唑环2位碳上增加甲基取代基后其密度、表面张力和电导率均呈下降趋势,而粘度呈上升趋势且变化较大,如在298.15 K时[Emim]BF4的粘度为842 mPa.s,[Dmeim]BF4的粘度为8 293 mPa.s。并根据特定的经验方程估算了两种离子液体的热膨胀系数、摩尔体积、标准熵和晶格能等重要的性质参数。     

超高压处理对冷藏鲈鱼品质的影响

研究了不同超高压条件(0、100、200、300 MPa,保压处理10 min)对鲈鱼冷藏过程中感官、p H值、白度、质构特性和持水性的影响。结果表明:鱼肉的感官评分、硬度、弹性和咀嚼度随贮藏时间的延长逐渐降低,白度逐渐升高,p H值先下降后上升,而持水性先上升后下降。超高压处理可显著提高鱼肉的硬度和咀嚼度(P0.01),同时提高了鱼肉的p H值和持水能力,增加了白度,200 MPa处理组的细菌总数低于对照组和其他2个处理组。此外,300 MPa的超高压处理对鲈鱼鱼肉品质的影响最大。综合感官和理化测定结果可知,超高压在改善鲈鱼肉质方面具有潜在的应用前景。     

芹菜苹果醋饮料抗氧化功能的研究

芹菜中含有营养保健作用的多酚物质,但由于芹菜本身具有的风味并不为大众人群所接受,所以用芹菜为原料制作出芹菜苹果醋可同时提高两者的应用价值。以芹菜和苹果为原料,制成蔬菜水果醋饮料,芹菜苹果醋饮料配方:苹果醋:芹菜汁为10:3(V/V),蜂蜜6%,白砂糖8%。对芹菜苹果醋中多酚进行含量分析,多酚含量达到412mg/dL。     

Effect of tea polyphenols on the physical and chemical characteristics of dried-seasoned squid (Dosidicus gigas) during storage

The effects of tea polyphenols (TP) dip treatment on the physical and chemical characteristics of dried-seasoned squid (Dosidicus gigas) during storage at 25 °C were assessed. After the storage, the b* value increased significantly, while the free amino acids (FAA) including Ser, Gly, Arg, Tyr and Lys, and the dominant reducing sugar (RS), lactose, decreased remarkably, which revealed the occurrence of browning reaction in dried-seasoned squid. The progressive conversion of trimethylamine oxide (TMAO) and production of thiobarbituric acid (TBA) and total volatile basic nitrogen (TVB-N) were found during the entire period of storage. Furthermore, the advantages of reducing moisture loss, inhibiting oxidation of lipids, depressing TMAO breakdown and TVB-N accumulation were observed, while the browning reaction exhibited no significant decrease for the TP samples. These results indicated that the addition of TP could maintain quality of dried-seasoned squid.     

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.