Physicochemical and molecular analysis of cell wall metabolism between two navel oranges (Citrus sinensis) with different mastication traits

BACKGROUND: FJ72‐1 navel orange and its bud mutant FJWC exhibit differences in melting texture character which are influenced mostly by cell wall metabolism. Here we compared the contents of water soluble pectin (WSP), protopectin, total pectin (TP), cellulose, and hemicellulose, activities of polygalaturonase (PG), pectin methylesterase (PME), pectate lyases (PL), cellulase (Cel) and gene expression levels of PG, PME, PL and Cel between the two cultivars. RESULTS: The content of cellulose and hemicellulose decreased progressively during fruit ripening. At the harvest time (230 DAF), the content of cellulose and hemicellulose in FJWC were obviously higher than those in FJ72‐1; the WSP content, PG activities and its gene expression level in FJWC was lower than those in FJ72‐1. Moreover, gene expression levels of PME and Cel in FJWC were only one‐quarter of those in FJ72‐1 at 230 DAF. CONCLUSION: The present work showed that the inferior melting character of FJWC attributed to the lower WSP, higher TP or protopectins, higher cellulose and hemicellulose than those in the pulp of FJ72‐1 at harvest time. Lower expression levels of PG, PME and Cel at harvest time might be associated with the inferior melting character. Copyright © 2010 Society of Chemical Industry     

热烫拉伸温度对Mozzarella干酪蛋白降解及质构特性的影响

不同的热烫拉伸温度对Mozzarella干酪的组织结构、凝块中微生物以及酶的活性有很重要的影响,进而会影响其成熟过程中蛋白质的降解以及最终品质的形成,该研究对不同热烫拉伸温度的Mozzarella干酪成熟过程中的蛋白降解及质构特性指标进行测定。结果表明,同一成熟期内,随着热烫温度（对照、70 ℃、90 ℃）的提高,干酪的pH 4.6可溶性氮（SN）显著下降（P＜0.05）,12%三氯乙酸-可溶性氮（TCA-SN）有所下降（P＞0.05）,而干酪的硬度、咀嚼性均显著增大（P＜0.05）,弹性增大而黏附性有所下降（P＞0.05）,融化性、油脂析出性均显著下降（P＜0.05）。因而采取70 ℃的热烫拉伸温度更有利于干酪成熟后形成良好的质构特性及充分的蛋白降解。     

Modification of pork-skin jelly by enzymatic cross-linking: melting resistance and quality improvement

Improvements of melting resistance and quality by modification of pork-skin jelly through enzymatic cross-linking were studied, and the mechanism of quality improvement was discussed in this work. Gel strength, springiness and chewiness of modified gel increased significantly (P < 0.05). Transglutaminase (TGase) also improved the viscoelasticity, stability and melting resistance of gel system, as proved by rheological analysis. Sensory evaluation showed that increase in texture need to be moderate and the utilisation of 0.6% TGase was the most appropriate for pork-skin jelly. Significant effects of TGase on inducing protein cross-link and aggregation were confirmed by determining rheology during enzyme treatment and cross-linking extent of pork-skin soup. Correlation analysis showed TGase could improve melting temperature and texture by facilitating cross-linking. Covalent interaction based on ε-(γ-glutamyl)-lysine induced by TGase could play the main role in these improvements. This study suggested that TGase could be applied to design gelatin-based food for tailored quality properties through enzymatic cross-linking.     

L-半胱氨酸盐酸盐对曲奇中4种有害醛类形成的抑制作用及其品质的改善效果

该研究将L-半胱氨酸盐酸盐添加到面团中制作曲奇,研究了不同添加量（0.3、0.6、1.0、1.5 g/kg）L-半胱氨酸盐酸盐对4种有害醛类含量、曲奇外观和挥发性物质的影响。结果表明：添加后,曲奇的接受度高于未添加对照组,且4种有害醛类的含量显著降低。当L-半胱氨酸盐酸盐添加量为1.5 g/kg时,曲奇中5-羟甲基糠醛、3-脱氧葡萄糖醛酮、乙二醛和丙酮醛含量分别降低28.75%、62.73%、46.27%、36.59%。微固相萃取-气质联用结果显示：添加后,曲奇的挥发性醛、醇和吡嗪类物质含量增加,大部分酮类物质含量减少。细胞毒性实验结果显示：添加L-半胱氨酸盐酸盐的曲奇水提取物添加对人胃粘膜上皮细胞活力有促进作用。结合实验分析,曲奇最适L-半胱氨酸盐酸盐添加量为1.0 g/kg。     

Heterogeneous reactions of polymers: 4. Melting behaviour of heterogeneously chlorinated and sulphonated polyethylenes

The melting behaviour of heterogeneously chlorinated and sulphonated high-density polyethylene was studied by differential scanning calorimetry. It was found that an increase in T_m takes place at high degrees of substitution in the amorphous phase. For sulphonated polyethylenes the increase in T_m was also dependent on the type of the counterion. The effect is interpreted as a decrease in configurational entropy upon fusion due to the restraints that the highly chlorinated and sulphonated amorphous regions impose on the adjacent crystallites.     

Complexation of poly-2,5-dimethyl-4-vinylethynilpyperidol-4 hydrochloride with transition metal ions in solution

The interaction of transition metal ions with poly-2,5-dimethyl-4-vinylethynilpyperidol-4 hydrochloride in solution have been investigated potentiometrically, spectroscopically and viscometrically. influence of ionic strength, composition of solvent and various metal ions nature on the viscosity of polyelectrolyte-metal complexes are discussed.     

The morphology of poly(aryl-ether-ether-ketone)

The morphology and related properties are described for the aromatic thermoplastic poly(aryl-ether-ether-ketone) (PEEK) [C₆H₄OC₆H₄OC₆H₄CO]_n. Topics covered include crystallinity, crystallization and melting behaviour, Iamellar thickness and spherulitic structure. The data are used to derive the following material parameters $\text{T1}{}_{\mathrm{<mtext>m</mtext>}}\text{= 395°}\text{C}$, σ_e = 49 erg cm^?2, σ_s = 38 erg cm^? and ΔH_F = 130 kJ kg^?1. PEEK is closely analogous to poly(ethylene terephthalate) in its crystallization behaviour except that the main transitions occur about 75°C higher.     

从失效催化剂中回收钌的研究进展

总结了从失效催化剂中回收钌的多种方法和工艺,重点介绍了常用的熔融氧化蒸馏法。熔融氧化蒸馏法由于工艺繁杂、步骤冗长、对设备要求高等缺点,近年来不同学者和行业专家先后提出了还原沉淀法、直接氧化法和活泼金属置换法等方法,但尚未有工业化应用的报道。简化工艺流程、提高钌的回收率是目前钌回收研究工作并实现其工业化生产的重点和难点。     

镍闪速熔炼新渣型的物化性质研究

金川镍铜渣中铁的还原性差、难以作为炼铁炉料直接入炉冶炼。提出了提高渣中CaO含量、降低SiO2含量为后续提铁创造条件的工艺设想,并利用FactSage计算模拟软件对金川镍闪速熔炼渣主要成分的相图进行模拟计算,通过试验考察了不同炉渣组分对熔渣物化性质影响的规律。结果表明,合适的新渣型为Fe/SiO2=1.5,CaO 10%～15%,MgO 9%。     

不同类型石墨坩埚对钢中氮分析影响的探讨

从熔融状态、加热电流和释放峰形等方面考察了套坩埚和标准坩埚对钢中氮分析的影响,并探讨了套坩埚结构特点对氮分析改善的原因。结果发现,在相同的分析功率下,套坩埚的电流较小,温度稍低;但使用两种坩埚熔样时,套坩埚的熔样效果好,且氮峰释放平缓。对两种有证参考物质分别采用两种坩埚进行试验,发现使用套坩埚时的分析精度明显优于标准坩埚。所以,虽然套坩埚的加热温度稍低,但在保证样品完全熔融的前提下,有利于提高氮的分析精度。