Rice ratooning is the cultural practice that easily produces secondary rice from the stubble left behind after harvesting the main crop. ‘Daol’ is an extremely early growing rice variety. Planting this variety early allows for an additional ratoon harvest after the primary rice harvest. The plant growth and yield of ratoon rice were very low compared to those of main rice. Protein, amylose content, and head rice rate were higher in ratoon rice than in main rice. The distribution by the rice flour particle size of main and ratoon rice was similar. The damaged starch content in ratoon rice was relatively high at 6.1%. Ratoon rice required a longer time and higher temperature for pasting than main rice. Compared to the original rice, peak viscosity (PV), hot paste viscosity (HPV), cool paste viscosity (CPV), and breakdown (BD) were very low, and setback (SB) was high. As a result of analyzing the gelatinization properties of main and ratoon rice using differential calorimetry, it was found that the onset (To), peak (Tp), and conclusion (Tc) of ratoon rice starch were processed at a lower temperature than those of main rice. The gelatinization enthalpy of both samples was similar. The distribution of amylopectin short chains in ratoon rice was higher than that in main rice.

재래벼와 잡초벼 등 국내 고유 유전자원을 밥쌀용 벼 품종 개발에 활용하기 위한 기초자료를 얻기 위하여 전분 호화특성 분석과 함께 식미 관련 물리·화학적 특성의 연차 간 변이를 분석하여 환경 변화에 대한 안정성을 검토하였다. 1. 76개 유전자원을 이용하여 전분 호화특성 및 식미관련 특성에 대한 조사를 연차간 수행하여 그 변이를 상관분석으로 비교한 결과 고도로 유의한 상관관계를 확인하였다. 2. 수집 특성에 따라 유전자원을 4그룹으로 나누고 조사항목의 연차간 평균값을 비교한 결과 상관계수와 관계없이 기상 변화에 따라 항목별로 연차간 유의한 차이를 확인하였다. 3. 호화특성 기반의 군집분석 결과 76개 자원이 6개의 그룹으로 각각 분류되었으며, 약 55% 이상의 유전자원이 III, IV 그룹에 분포되었고, 국내 품종(C그룹)과 국내 잡초벼(B그룹) 유전자원의 경우 군집분석결과 5개의 그룹에 걸쳐 가장 넓게 분포하였다. 4. 전분 호화특성 및 식미특성을 기준으로 밥윤기치가 높았던 국내 재래벼 2품종(왜도와 구도)과 국내 잡초벼 3품종(달성앵미10-2, 남제주앵미6, 완도앵미6) 우량품종으로 선발되었다. 5. 특히, 완도앵미6의 경우 밥윤기치 평균 값이 85.1로 매우 높았으며, 이화학적 특성 등이 수광 수준으로 양호하였는데, 이는 국내의 고유 유전자원으로부터 우수한 자원을 확보하여 유용 유전자를 도입하는 육종연구에 활용가치를 높일 수 있을 것으로 생각된다.

식품첨가물등급의 protease를 이용하여 쌀가루로부터 쌀 전분을 분리하는 효소적 쌀전분 분리·정제법을 구축하기 위해 protease의 반응시간, 반응온도와 농도를 요인으로 하여 변형된 23 완전요인설계법에 따라 protease 반응조건들을 설계하고 이에 따른 쌀전분들의 수율을 조사하였다. 설계된 반응조건들에 따라 제조된 쌀전분들의 수율들에 기초한 반응표면분석을 통해 쌀전분 수율에 대한 protease 반응조건들의 영향을 조사하였다. 또한 효소적 분리·정제법에 의한 쌀전분들의 상업적 활용도를 평가하기 위해 알칼리침지법에 의해 제조된 쌀전분(대조군)과 물리화학적 특성을 대해 비교 분석하였다. Protease를 이용한 효소적 분리· 정제법에 의한 쌀전분들의 수율은 대조군보다 낮았지만 그 상대적 순도는 높은 수준을 나타내었다. Protease에 미량 함유되어 있는 amylase 계통의 효소들에 의한 쌀전분의 부분적인 손상이 예상됨에도 1.5% protease를 이용하여 15℃에서 24시간 동안 처리하여 제조된 쌀전분(RST2)의 아밀로오스 함량은 대조군의 것과 유의적인 차이를 보이지 않았다. 용해도는 효소적 분리·정제법에 의한 쌀전분들이 대조군보다 유의적으로 높은 수준을 나타내었다. 팽윤력은 RST2와 0.5% protease를 이용하여 15℃에서 24시간 동안 처리하여 제조된 쌀전분(RST3)이 대조군과 유의적인 차이를 보이지 않았다. 호화온도는 대조군에 비해 효소적 분리 ·정제법에 의한 쌀전분들이 높은 수준을 나타내었으나 호화엔탈피는 유의적으로 낮은 수준이었다. 페이스팅 점도는 대조군에 비해 효소적 분리·정제법에 의한 쌀전분들이 모든 온도프로파일에 있어 낮은 수준을 나타내었다. 이와 같은 결과들은 효소적 분리·정제법에 사용된 protease에 미량 함유되어 있는 amylase 계통의 효소들에 의한 쌀전분의 부분적인 손상과 protease 처리하는 동안 쌀전분에 있어 annealing이 진행된 결과인 것으로 생각된다. 그럼에도 본 연구에서 효소적 분리·정제법에 의해 제조된 쌀전분들은 높은 고형분 함량을 요구하며, 페이스트의 겔화 또는 노화의 진행이 지연되는 특성을 가공식품의 원료로 적합한 것으로 판단된다. 따라서 효소적 분리·정제법에 의한 쌀전분들은 기존의 알칼리 침지법에 의한 쌀전분과는 다른 특성을 보유한 쌀전분 소재로서 활용가능성이 있을 것으로 생각된다. 또한 효소적 분리·정제법은 알칼리 침지법에 비해 쌀전분의 제조 시간을 단축할 수 있으며, 고농도의 염용액을 배출하지 않아 경제적인 방법인 것으로 판단된다.

Rice starch is a natural source of polysaccharides that can be used as a stabilizer, thickener, binder and fat mimetic in various foods. However, untreated starch possesses limited functionality due to its poor water solubility with a densely packed granular structure of amylopectin and amylose chains. Also, it shows weak complexing ability as the only amylose participates in complex formation with a chemical compound. The objective of this study is to improve complexation ability and water solubility of rice starch by 4-α-glucanotransferase (4αGTase) treatment. Complex forming capacity was examined by fully dissolving the 4αGTase-treated rice starch in 90% DMSO by mechanical stirring and mixing with iodine solution with following UV/Vis spectrophotometer measurements. Water solubility of the starch was measured by dissolving in distilled water (5% w/v) with mechanical stirring at 25 °C and 60 °C, and drying the supernatant after centrifugation. The complexing ability of starch was enhanced after the 4αGTase treatment. The absorbance at a peak wavelength increased, as well as the peak wavelength was shifted leftward, indicating that the type of molecules got involved in the complexation was changed. Alteration in the molecule composition and starch composition during the enzyme treatment may be due to disproportionation and cyclization by the 4αGTase. The water solubility (%) of the starch at 25 °C and 60 °C increased by 28-fold with the 4αGTase treatment regardless of the treatment time. The untreated starch showed solubility of 0.15 %, while the solubility of the 4αGTase-treated starch was about 4 - 4.5 % (w/v). It may be due to heat treatment and recrystallization which melted a granular structure and made it easier to be solubilized in water. Moreover, the increased solubility might be attributed to increase in the number of short branched chains and decrease in molecular weight.

The relationship of in vitro starch digestibility and gel strength was investigated at various concentrations (10-30%) of rice cultivars with different amylose contents (27.9, 17.9, and 5.2%). As the rice flour concentration increased, predicted glycemic index decreased, but gel strength increased regardless of amylose contents. Gel strength correlated strongly with amylose content, whereas in vitro starch digestibility was more highly affected by rice flour concentration than by amylose contents. Moreover, the impact of degree of gelatinization on in vitro starch digestibility of high amylose rice was also examined in terms of structural features and rheological properties. The digestion rate of fully gelatinized flour was 1.7 times higher than that of native flour, while the disrupted structure with a different gelatinization degree during starch digestion was visually demonstrated through the X-ray diffraction and molecular distribution analysis. The rice flour changed from an A-type to a V-type pattern and showed difference in crystalline melting. The low molecular weight distribution increased with increasing degree of gelatinization during starch digestion. The apparent viscosity also increased with degree of gelatinization. These results demonstrated that the starch digestibility of rice was more affected by concentration than by amylose content, as well as by the degree of gelatinization due to structural difference.

Curcumin is an active polyphenolic compound with antioxidant, anti-inflammatory and antitumor properties. Curcumin, however, is highly unstable under physiological conditions due to its low stability in acidic and alkaline conditions. Therefore, the objective of this study was to investigate the effects of enzyme-treated rice starch as a wall material on the stability of curcumin in oil-in-water emulsion under different pH conditions. The rice starch was treated using 4-a-glucanotransferase for different time periods and their molecular weight distribution was measured by HPSEC. Curcumin was encapsulated within lipid droplets of O/W emulsion prepared with Tween 20 and the modified rice starch in the aqueous phase at different concentrations (0, 2.5, 7.5 and 10 wt%). The temperature and pH stability of the system were determined respectively by measuring particle size, zeta potential and retention of the curcumin loaded in the emulsion after one-week storage in the solutions with different pH and temperature conditions. The average molecular weight of the modified starch decreased with treatment time. The 96h treated rice starch had the lowest molecular weight while the 1h treated starch mainly consisted of high molecular weight components. The storage temperature did not significantly influence the stability of curcumin emulsion. However, the particle size of the emulsion with modified starch slightly increased when stored at acidic pH condition, which might be attributed to starch aggregation. The curcumin retention was higher for the samples with the modified starch than the control at all concentrations. The pH stability of the curcumin was also higher than the control at all pH conditions. Specifically, the 1h treated starch showed the best performance regarding curcumin protection in emulsion, which might be attributed to the high viscosity that retarded the curcumin release. Further research needs to be conducted on the mechanism.

With increasing interests on health issues, whole grains are getting focus with their various beneficial effects along with unique characteristics. Studies on whole grains, however, are mostly focused on whole wheat grains, no systematic researches on whole rice grain has been attempted. In this study, we tried to characterize the starches in whole rice grain including morphology, molecular weight distribution and its side chain structures for further application. Early harvested whole rice grains, named as green whole rice (GWR) was coarsely grounded and starch fraction was separated through alkaline steeping method and dried for the analysis. Morphology of starch particles of GWR was investigated with scanning electron microscopy (SEM) and no significant differences was observed compared to the control rice starches. Pre-treatments such as dehulling and steaming also did not affect overall shape of starches in rice. Molecular weight distribution of GWR starch was analyzed with gel permeation chromatography (GPC) and compared with normal rice starch. GPC analyses revealed that the relative ratio of higher molecular weight fractions in GWR was significantly higher than normal rice. In addition, side chain structures of amylopectin molecules in GWR starch was analyzed with high performance size exclusion chromatography (HPSEC). The average number of DP in GWR was shorter with higher ratio of shorter side chain fractions than normal rice starch. These findings on GWR starch would be useful basement for following research and application of green whole rice.

This study was aimed to develop a gruel using rice extrudates and to evaluate physicochemical properties of Tarakjuk (milk porridge; MP) prepared with milk (M) and rice powder (RP, control), rice extrudate (RE), or enzyme treated rice extrudates (ETR). Pasting property of ETR was significantly different from those of RP or RE with significantly low peak viscosity, breakdown and setback values in the ETR sample. Viscosity of MP prepared with ETR was also significantly low, as compared to that of control (> 900 cP). The total solids and spreadability of MP with ETR was higher than those with RP or RE. Hunter color values varied significantly depending on enzyme treatment levels in ETR samples with enzyme dose-dependent increase in b-value. Average starch digestibility of ETR sample was higher by 10.2% than that of control sample. DPPH radical scavenging activities of ETR samples were greater than those of RE or RP. These results indicated that ETR could be beneficial for preparing easy-drink and diet food with higher starch digestibility and fluidity, especially for gastric tube-fed patients.