BackgroundPanax ginseng Meyer is cultivated because of its medicinal effects on the immune system, blood pressure, and cancer. Major ginsenosides in fresh ginseng are converted to minor ginsenosides by structural changes such as hydrolysis and dehydration. The transformed ginsenosides are generally more bioavailable and bioactive than the primary ginsenosides. Therefore, in this study, hydrothermal processing was applied to ginseng preparation to increase the yields of the transformed ginsenosides, such as 20(S)-Rg3, Rk1, and Rg5, and enhance antioxidant activities in an effective way.MethodsGinseng extract was hydrothermally processed using batch reactors at 100–160°C with differing reaction times. Quantitative analysis of the ginsenoside yields was performed using HPLC, and the antioxidant activity was qualitatively analyzed by evaluating 2,2'-azino-bis radical cation scavenging, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, and phenolic antioxidants. Red ginseng and sun ginseng were prepared by conventional steaming as the control group.ResultsUnlike steaming, the hydrothermal process was performed under homogeneous conditions. Chemical reaction, heat transfer, and mass transfer are generally more efficient in homogeneous reactions. Therefore, maximum yields for the hydrothermal process were 2.5–25 times higher than those for steaming, and the antioxidant activities showed 1.6–4-fold increases for the hydrothermal process. Moreover, the reaction time was decreased from 3 h to 15–35 min using hydrothermal processing.ConclusionTherefore, hydrothermal processing offers significant improvements over the conventional steaming process. In particular, at temperatures over 140°C, high yields of the transformed ginsenosides and increased antioxidant activities were obtained in tens of minutes.

Adipic acid crystals grown from aqueous solutions have a hexagonal plate morphology with a dominant (100) face, where the hydrogen-bonding carboxylic acid groups are exposed. In the present work, the crystal morphology was investigated by interfacial structure analysis to obtain the relative growth rates for the spiral growth model. The concentration of effective growth units at the interface was found to be the key external habit-controlling factor by molecular dynamics simulations at the crystal−solution interface. The differences between the experimentally observed faces of ( 002), (100), and (011) and unobserved faces of (111̅ ), (102̅ ), and (202̅ ) were explained by two concepts from the interfacial structure analysis that determine the concentration of the effective growth units. The observed faces were characterized by larger values of both the surface scaling factor and molecular orientation factor, implying low anisotropic local concentrations at the interface and high free energy barriers for reorientation on these faces, respectively. Furthermore, the number of turns and the length of one complete spiral rotation and the number of unsaturated bonds were incorporated into the original approach. This consideration of the spiral geometry resulted in a close resemblance to the experimental morphology.

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Abstracts − The hydrolysis of defatted rice bran using near-critical water was performed, and the feasibility of consequent hydrolyzate as a growth medium was investigated by the cultivation of Saccharomyces cerevisiae. The near-critical water hydrolysis was carried out through a series of batch experiments, and the contents of total carbohydrates, disaccharides, and monosaccharides, total organic carbon (TOC), total nitrogen (TN), pH of products were measured. The growth rate of Saccharomyces cerevisiae was measured with optical density. The yield of total carbohydrates, TOC, and TN increased with temperature below 240 o C, however, decreased above 240 o C. The decrease of yields above 240 o C was caused by the formation of organic acids, and it agreed with the change of pH of products. The yield of glucose was a maximum at 200 o C and it decreased dramatically at higher temperature. The growth rate of Saccharomyces cerevisiae cultivated in the hydrolyzate was similar with that in the commercial medium under certain conditions. The growth rate was correlated with the content of glucose in hydrolyzate.