Woo-Cheul Han

Production of Lactosucrose from Sucrose and Lactose by a Levansucrase from Zymomonas mobilis

Lactosucrose (4(G)-beta-D-galactosylsucrose) is an oligosaccharide consisting of galactose, glucose, and fructose. In this study, we prepared lactosucrose from lactose and sucrose using a levansucrase derived from Zymomonas mobilis. Optimum conditions for lactosucrose formation were 23 degrees C, pH 7.0, 18.0% (w/v) lactose monohydrate, and 18% (w/v) sucrose as substrates, and 1 unit of enzyme/ml of reaction mixture. Under these conditions, the lactosucrose conversion efficiency was 28.5%. The product was purified and confirmed to be O-beta-D-galactopyranosyl-(1-->4)-O-beta-D-glucopyranosyl- (1-->2)-beta-D-fructofuranoside, or lactosucrose. A mixed-enzyme system containing a levansucrase and a glucose oxidase was applied in order to increase the efficiency of lactose and sucrose conversion to lactosucrose, which rose to 43.2% as s result.

Evaluation of physicochemical properties and fermenting qualities of apple wines added with medicinal herbs

To evaluate the possibility for development of apple wine containing medicinal herbs, we have prepared ‘Fuji’ apple (Malus domestica) wines containing pine (Pinus densiflora Siebold et Zuccarini) needle and hwanggi (Radix Astragali)/mistletoe (Viscum album). Normal apple wine was fermented rapidly, but after 40 days fermentation/maturation, the final ethanol content, pH, total acidity, and contents of sugar/organic acid showed similar levels in 3 kinds of apple wines. In other hands, the total phenols content, antocyanins content, and brightness were higher in apple-pine wine and apple-herb wine than in normal apple wine. Apple-herb wine had higher values in total phenol contents, brightness, free amino acid contents, and quenching activity for ABTS free radicals than normal apple wine, and had similar sensory evaluation values with normal apple wine. Taken together, it is supposed that hwanggi and mistletoe might provide functional components to normal apple wine and might be applied to development of functional apple wines.

Quality Evaluation of Vinegar Manufactured using Rice and Rosa rugosa Thunb.

In order to prepare rice vinegar, takju fermentation was performed, using two different compositions; cooked rice supplemented with Rosa rugosa Thunb. (CR-R) and uncooked rice supplemented with Rosa rugosa Thunb. (UR-R). After ethanol fermentation, ethanol contents of takju were adjusted to 6.0%, and then acetic acid fermentation was carried out using Acetobacter aceti at 30 o C with 200 rpm for 9 days. Supplementations of 1% acetic acid to takju prior to acetic acid fermentation were a critical step in achieving a successful fermentation; final organic acid contents increased in a dose dependent manner. A higher content of organic acids, 1.6-6.9%, was found in UR-R vinegar. The level of free amino acid and GABA in UR-R vinegar was higher than that of CR-R vinegar, with glutamic acid and arginine, as the major amino acids. This finding demonstrates that heating process of rice prior to ethanol fermentation affects the quality of vinegar significantly.