The effect of steaming on the free amino acid contents and antioxidant activity of Panax ginseng

This study was carried out to investigate changes in the free amino acid contents and antioxidant activity of Panax ginseng induced by steaming at different temperatures. For this purpose, white ginseng (WG), red ginseng (RG, ginseng steamed at 100 °C) and ginseng steamed at 120 °C (SG) were prepared using an autoclave. Most free amino acids were decreased significantly by steam treatment, with the greatest reduction observed in SG. Total content of free amino acids, 17.9 mg/g in WG was reduced to 12.2 mg/g in RG and 2.79 mg/g in SG. As for Arg which is the most predominant amino acid in ginseng, the content, 10.4 mg/g in WG, decreased significantly to 1.38 mg/g in SG. In particular, β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), a well-known neurotoxin, was reduced by 92.9% in SG. In contrast, the level of Maillard reaction products (MRPs) increased with steam treatment, which indicates that the reduction of most amino acids is attributed to the extent of the Maillard reaction. Based on MRPs being useful antioxidants, we assayed the scavenging activity against free radicals produced by 2,2′-azobis-(2-amidinopropane) dihydrochloride (AAPH). The radical scavenging activity of a ginseng extract increased with steam treatment, with the most potent activity in SG. Further, MRPs-rich fraction in SG showed powerful antioxidant activity, which indicates MRPs are major contributors to antioxidant activity enhanced by steam treatment.     

Frequency-Dependent Properties of the Hyperpolarization-Activated Cation Current,If, in Adult Mouse Heart Primary Pacemaker Myocytes

A number of distinct electrophysiological mechanisms that modulate the myogenic spontaneous pacemaker activity in the sinoatrial node (SAN) of the mammalian heart have been investigated extensively. There is agreement that several (3 or 4) different transmembrane ionic current changes (referred to as the voltage clock) are involved; and that the resulting net current interacts with direct and indirect effects of changes in intracellular Ca²⁺ (the calcium clock). However, significant uncertainties, and important knowledge gaps, remain concerning the functional roles in SAN spontaneous pacing of many of the individual ion channel- or exchanger-mediated transmembrane current changes. We report results from patch clamp studies and mathematical modeling of the hyperpolarization-activated current, I_f, in the generation/modulation of the diastolic depolarization, or pacemaker potential, produced by individual myocytes that were enzymatically isolated from the adult mouse sinoatrial node (SAN). Amphotericin-mediated patch microelectrode recordings at 35 °C were made under control conditions and in the presence of 5 or 10 nM isoproterenol (ISO). These sets of results were complemented and integrated with mathematical modeling of the current changes that take place in the range of membrane potentials (−70 to −50 mV), which corresponds to the ‘pacemaker depolarization’ in the adult mouse SAN. Our results reveal a very small, but functionally important, approximately steady-state or time-independent current generated by residual activation of I_f channels that are expressed in these pacemaker myocytes. Recordings of the pacemaker depolarization and action potential, combined with measurements of changes in I_f, and the well-known increases in the L-type Ca²⁺ current, I_CaL, demonstrated that I_CaL activation, is essential for myogenic pacing. Moreover, after being enhanced (approximately 3-fold) by 5 or 10 nM ISO, I_CaL contributes significantly to the positive chronotropic effect. Our mathematical model has been developed in an attempt to better understand the underlying mechanisms for the pacemaker depolarization and action potential in adult mouse SAN myocytes. After being updated with our new experimental data describing I_f, our simulations reveal a novel functional component of I_f in adult mouse SAN. Computational work carried out with this model also confirms that in the presence of ISO the residual activation of I_f and opening of I_CaL channels combine to generate a net current change during the slow diastolic depolarization phase that is essential for the observed accelerated pacemaking rate of these SAN myocytes.     

HXD蒸气喷射量对叶丝膨胀效果及卷烟内在质量的影响

分别在不同起始干燥含水率条件下进行了不同蒸气喷射量对叶丝膨胀及卷烟内在质量的综合影响因素研究。结果表明:采用相对较低起始干燥含水率进行干燥时,随着蒸气喷射量的增加,叶丝填充值逐渐增加,烟支的卷制重量逐渐下降;采用相对较高起始干燥含水率进行干燥时,蒸气喷射量对叶丝在线膨胀的影响不明显,随着蒸气喷射量的增加,叶丝填充值及烟支卷制重量差异不大;在气流干燥过程中,根据配方档次及起始干燥含水率的不同,需要的蒸气喷射量也不同,对相对较低起始干燥含水率的中高档卷烟宜不加或少加蒸气;对相对较高起始干燥含水率的低档卷烟适当加大蒸气量,有利于卷烟内在质量的改善。     

Effect of steam cooking on distribution of paralytic shellfish toxins in different tissue compartments of scallops Patinopecten yessoensis

This study investigated the effect of steam cooking on distribution of paralytic shellfish poisoning toxins (PSP-toxins) in scallops Patinopecten yessoensis. Toxins analysis by high-performance liquid chromatography showed that most of the PSP-toxins (>70%) were accumulated in viscera and adductor muscle of the raw scallops. Steam cooking induced significant loss (p < 0.05) of PSP-toxins from viscera (16%), adductor muscle (24%), gill and mantle (11%) while 32% of the toxins were retained inside viscera and adductor muscle. Overall, 51% of PSP-toxins leaked out from scallop tissues during steam cooking. However, there was no significant loss (p > 0.05) of PSP-toxins from gonad. Consumption of viscera was the most significant risk factor for causing PSP, while gonad and scallop soup were the second most significant. A rapid PSP test further verified detectable levels of PSP-toxins in all samples. However, possible interfering substance(s) in adductor muscles and gonads might potentially affect the results from this test.     

宰后电刺激与肌肉嫩化研究及其在肉类工业中的应用

本文阐述了肌肉的嫩化机制及宰后电刺激促进嫩化的机理,介绍了该领域的最新研究成果,并对电刺激在宰后嫩化中的应用进行了讨论。     

细菌Enterobacter dissolvens的直流电解刺激过程

以葡萄糖为唯一碳源,研究了细菌Enterobacter dissolvens在直流电条件下的生长和代谢过程. 实验结果表明,当使用盐桥屏蔽电极反应时,细胞生长曲线和葡萄糖代谢速率基本不受电流强度的影响,而当采用铂丝电极时,反应体系中发生水解反应,采用10 mA电流通电12 h后,菌液中细胞的脱氢酶比活力和葡萄糖降解率分别为对照的1.98倍和1.48倍,细胞生长亦有所加快,但在其活力下降时出现大量死亡. 扫描电镜照片显示细胞结构受到明显破坏,并发生细胞膜穿孔现象,这表明可能受到了过氧化氢等阳极水解中间产物的刺激作用.     

Hydrogen and syngas yield from residual branches of oil palm tree using steam gasification

Wastes produced during oil palm production from agro-industries have great potential as a source of renewable energy in agriculturally rich countries, such as Thailand and Malaysia. Clean chemical energy recovery from oil palm residual branches via steam gasification is investigated here. A semi-batch reactor was used to investigate the gasification of palm trunk wastes at different reactor temperatures in the range of 600 to 1000 °C. The steam flow rate was fixed at 3.10 g/min. Characteristics and overall yield of syngas properties are presented and discussed. Results show that gasification temperature slightly affects the overall syngas yield. However, the chemical composition of the syngas varied tremendously with the reactor temperature. Consequently, the syngas heating value and ratio of energy yield to energy consumed were found to be strongly dependent on the reactor temperature. Both the heating value and energy yield ratio increased with increase in reactor temperature. Gasification duration and the steam to solid fuel ratio indicate that reaction rate becomes progressively slower at reactor temperatures of less than 700 °C. The results reveal that steam gasification of oil palm residues should not be carried out at reactor temperatures lower than 700 °C, since a large amount of steam is consumed per unit mass of the sample in order to gasify the residual char.     

Production of hydrogen by ethanol steam reforming over catalysts from reverse microemulsion-derived nanocompounds

In the present work, hydrotalcite-like compound precursor for preparing mixed oxide catalyst was successfully synthesized by a novel method, which was a combination of the reverse microemulsion and coprecipitation methods. It was observed that the precursor obtained from the above method possessed superior characteristics for preparing mixed oxide catalyst used in ethanol steam reforming (ESR). Furthermore, for comparison, catalysts prepared from conventional coprecipitation and impregnation methods had been characterized together with the catalyst prepared from the new method. Besides ICP, BET, X-ray diffraction (XRD), temperature-programmed reduction (TPR), H₂-TPD, TG, and TEM analytic techniques, catalytic performance for ESR was also investigated. The results of XRD and TPR indicated that a solid solution phase existed in the catalysts obtained from reverse microemulsion and coprecipitation methods, while spinel phase together with solid solution were observed in the catalyst obtained from the impregnation method. The high BET surface area of the catalyst obtained from the reverse microemulsion method enhanced the dispersion and the surface area of nickel, which improved the catalyst performance. From TEM images, the aggregated Ni could be found in the catalyst obtained from the impregnation method, while the hydrotalcite-like compound precursors prepared from reverse microemulsion and coprecipitation methods produced homogeneously distributed active Ni metal species. The catalyst obtained from reverse microemulsion exhibited the best activity, stability, and least carbon deposition because of the formation of hydrotalcite-like compound precursor, uniform dispersion of active Ni metal species, and much more surface area supporting the active Ni metal sites.     

Steam reforming on Ni-samaria-doped ceria cermet anode for practical size solid oxide fuel cell at intermediate temperatures

Direct internal and external reforming operations on Ni-samaria-doped ceria (SDC) anode with the practical size solid oxide fuel cell (SOFC) at intermediate temperatures from 600 to 750 °C are carried out to reveal the reforming activities and the electrochemical activities, being compared with the hydrogen-fueled power generation. The cell performance with direct internal and external steam reforming of methane and their limiting current densities were almost the same irrespective of the progress of reaction in the methane reformate at 700 and 750 °C. The durability test for 5.5 h at 750 °C with direct internal reforming operation confirmed that the cell performance did not deteriorate. The operation temperature of the cell controlled the reforming activities on the anode, and the large size electrode gave rise to high conversion due to the slow space velocity of the steam reforming. Direct internal steam reforming attained sufficient level of conversion for SOFC power generation with methane at 700 and 750 °C on the large Ni-SDC cermet anode.