Seung-Hyun Ahn

Difference of Starch Characteristics of Sweetpotato (Ipomoea batatas (L.) Lam) by Cultivated Regions

We investigated out the effect of cultivation region on the physicochemical characteristics of starch in six sweetpotato cultivars. The following sweetpotato cultivars were analyzed: Daeyumi, Shingeonmi, Jinhongmi, Shinyulmi, Yulmi, and Yeonhwangmi. Samples were cultivated in Muan, Iksan, Nonsan, Boryeong and Hamyang. The soil texture was found to be sandy loam in Muan, Iksan, and Boryeong, sandy clay loam in Nonsan, and loam in Hamyang. The starch content of the sweetpotato was higher in Muan than in Hamyang. The amylose content was 22.3-30.9%, and the highest amylose content was found in samples from Iksan. Rapid viscosity analysis showed that the samples from Hamyang had the lowest values of pasting temperature, while samples of the Daeyumi cultivar had the highest values. Thermal analysis with a differential scanning calorimeter showed that the Muan samples had the highest values of onset temperature, maximum peak temperature, and completion temperature, and the samples from Hamyang had the lowest values. There was no difference between the cultivation regions or the cultivar in the X-ray pattern of the starch or its appearance in scanning electron micrographs. Therefore, the results of this study confirm that cultivation region and cultivar play an important role in determining the quality of sweetpotato and the physicochemical characteristics of sweetpotato starch.

Synthesis of oligosaccharide-containing orange juice using glucansucrase

Orange juice is a well-accepted fruit juice, and is a natural source of various vitamins, especially vitamin C, as well as sugar, potassium, thiamine, folate, flavonoids and antioxidants. The respective fructose, glucose, and sucrose concentrations were 9.3, 22.9, and 48.1 g/L in the original orange juice used in this study, and 183.4, 170.1, and 142.8 g/L after concentration. Over 97% of the sucrose in the juice was enzymatically converted to glucooligosaccharides upon addition of 3 U/mL dextransucrase, prepared from Leuconostoc mesenteroides 512FMCM, at 16°C. The synthesized oligosaccharides comprised 35.0% of the total saccharides in the concentrated juice and 31.7% in the original juice. The optimum conditions for oligosaccharide synthesis using the concentrated juice were 35.2 × 10−1 U/mL dextransucrase and 1% Ca(OH)2. The calories in the original and modified concentrated orange juices were 325.4 and 246.7 kcal/L, respectively. Compared to the original concentrated juice, the enzyme-modified concentrated juice prevented the formation of 62.7% of the insoluble glucan resulting from addition of mutansucrase, produced by Streptococcus mutans.

Weeding Effect of Using Soybean Cake and Cultivating Weeder Together in Rice Bran Farming

ABSTRACT This study was conducted to improve weeding effect by rice bran farming technique. In the weeding effect experiment by application timing control of rice bran and soybean cake, weeding efficacy was the highest at the treatment of conventional application of rice bran. The treatment of soybean cake with rice bran was unfavorable, but Echinochloa crus-galli occurred little at the treatment of soybean cake at 5 days after transplanting, so it is thought that further study about inhibitor of early E. crus-galli occurrence in soybean cake is necessary. Cultivating weeder was effective at the treatments of rice bran and soybean cake together, of which weed occurrence was more than conventional rice bran, and precise experiments about cultivating weeding time and method will be necessary.Key words: cultivating weeder; rice bran; soybean cake; weeding effect. 서 언 최근 친환경농업에 대한 관심이 높아짐에 따라 농업 환경에 대한 부하를 최소화하려는 노력이 점점 증가하고 있다. 우리나라는 2013년까지 2003년 대비 화학비료와 농약 사용량을 40% 줄인다는 계획 하에 종합병해충 관리시스템 도입과 화학비료 줄이기 및 친환경농업 확대 등 다양한 시책을 시행하고 있다(농촌진흥청 2004). 그 중에서 주목받고 있는 방법 중 하나가 쌀겨농법이다. 이것은 일본에서 유기농 쌀 생산 농가들에 의해서 시작된 농법으로, 유기농의 가장 큰 문제인 잡초제거를 이 농법으로 일정부분 해결할 수도 있다는 점에서 도입하는 농가가 증가하고 있다(농업과학기술원 2005).

Physicochemical Characteristics of Sweetpotato (Ipomoea batatas (L.) Lam) Starch Depending on Cultivation Periods

This study was performed to understand the effect of cultivation periods on the physicochemical characteristics of the starch of five sweetpotato cultivars, cultivated in Muan, Korea. Starch, protein, and ash contents increased with increased cultivation period, whereas amylose content decreased. Rapid viscosity analysis showed that the pasting temperature, peak viscosity, breakdown, setback and final viscosity increased with increased cultivation period. However, trough and final viscosity decreased. Although the onset temperature and peak temperature values increased, the conclusion temperature did not show any consistent patterns by differential scanning calorimetry. X-ray diffraction showed that the starch samples had C-type crystallinity irrespective of the cultivation period and cultivar. The starch granules were dominantly round and oval, or polygonal irrespective the cultivation period. The bigger the particle size was, the longer the cultivation period was.

Improved Carbon Counter Electrodes for Dye Sensitized Solar Cells

We fabricated improved carbon counter electrodes to improve conversion efficiency of dye sensitized solar cells (DSSCs). Unlike conventional carbon counter electrodes, we added small quantity of TiO2 nano powder and used chemical sintering methodology developed by Park’s group to make surface morphology of the electrodes to change. Through these methods, we could observe change of surface morphology of carbon electrodes and influences on short circuit current density (JSC) and conversion efficiency.