As one of the staple crops, rice has been widely applied to value-added products, giving the food industry new avenues of use. Although the quality attributes of various rice products have been reported, there is a lack of detailed information on the rheological behaviors of rice products during digestion that are related to their bioaccessibility in the human body. In this study, three rice varieties with different amylose contents were utilized to produce flours and extruded noodles. In-vitro methods simulating starch digestion processes were then established to monitor their oral-gastric-intestinal rheological behaviors. The rice flour with high amylose content exhibited lower values of water absorption index/swelling power and higher pasting parameters that were in good agreement with the Mixolab thermo-mechanical results. The extruded rice noodles showed lower cooking loss and higher hardness with increasing levels of amylose. When the in-vitro viscosities of rice flours and noodles were measured using a rotational rheometer with the custom-made starch cell, their viscosities had a tendency to decrease as the in-vitro digestion progressed. Specifically, the rice samples with high amylose content exhibited higher viscosity than those with low amylose content under the simulated oral, gastric, and intestinal conditions. Hence, this study was conducted to investigate the physicochemical and in-vitro rheological properties of rice flours and extruded noodles with different amylose content. The results provided a promising opportunity for the food industry to study in-vitro digestion of rice-based products with the advantages of being more rapid and less expensive.

The baking properties of gluten-free rice bread with different percentages of corn starch and waxy corn starch were investigated. The specific gravity and color (L, a, b) of the dough as well as the appearance, color (L, a, b) and texture of the rice bread were analyzed. Replacement of rice flour with 1, 2.5, 5, 7.5 and 10% corn starch did not have a significant effect on the specific gravity and color of the dough. The volume and specific volume of the rice bread showed an increasing trend as the amount of added corn starch increased. The chewiness, gumminess and hardness of the rice bread showed a decreasing trend as the amount of added corn starch increased. Replacement of rice flour with 1, 5 and 10% waxy corn starch did not have a significant effect on the specific gravity and color of the dough. The color of the rice bread showed an increasing trend as the amount of added waxy corn starch increased. These results suggest that replacement of rice flour with 7.5% corn starch or 1% waxy corn starch is effective for gluten-free rice bread.

쌀 전분을 포함하는 크림수프 배합비에 친수성 콜로이드인 구아검(guar gum)의 첨가가 수프의 품질특성에 미치는 영향을 조사하였다. 쌀 전분에 구아검을 일부(10~30%) 대체하여 배합한 크림수프의 페이스트 특성을 신속점도측정기(RVA)를 사용하여 측정한 결과 구아검의 사용에 호화개시온도가 낮아지고 최고점도, trough 점도, 최종점도가 증가하였다. 크림수프의 수분 함량은 쌀 전분에 구아검을 10~30% 수준으로 대체한 크림수프에서 약간 높게 나타났으며 색도는 구아검의 대체수준이 증가함에 따라 명도가 약간 감소하였다. 쌀 전분 크림수프의 점도는 옥수수 전분을 첨가한 수프보다 약간 높은 반면에 감자, 고구마, 밀, 타피오카 전분을 사용하여 제조한 크림수프에 비해서는 다소 낮게 나타났으며, 쌀 전분에 구아검의 부분적인 대체에 의해 점도의 상승효과를 나타내었다. 쌀 전분 크림수프는 쌀 전분에 구아검을 일부 대체한 혼합사용에 의해 크림수프의 외관, 향, 맛, 입안의 감촉 등 관능적 기호성을 향상시킬 수 있음을 제시해 주었다.

연구에서는 전분질 원료를 달리한 18종류의 입국을 제조하고 당화력을 측정, 각각의 입국과 동일한 원료를 첨가하여 제조한 막걸리의 품질 특성과 관능검사 및 저장성 실험 결과를 분석하였다. 각각의 입국으로 제조한 막걸리의 에탄올 함량은 9-13%까지 고루 분포되었으며 제조한 막걸리 No. 5(현미) 군에서 13%로 가장 높게 측정되어 막걸리의 에탄올 생성에 있어 현미군이 유리할 것으로 사료된다. 막걸리의 총 당량은 막걸리 No. 6(찹쌀) 군이 11.3%, 환원당 또한 마찬가지로 4.8의 가장 높은 수치를 보여 막걸리의 당 생성에 있어 찹쌀군이 유리할 것으로 사료된다. pH는 막걸리 No. 2(밀+보리) 군이 3.6으로 가장 낮게 측정되었으며 총산은 6.0-9.1 사이로 고루 분포하였으며, 막걸리를 5oC에 보관 하였을 때 산도의 증가는 크지 않았으며 28oC에서 보관 하였을 때 3일 동안 총산이 급격하게 증가 하였지만 전분질 원료간의 특징적인 차이는 보이지 않았다.

국내 벼 품종 중 아밀로스 함량과 아밀로펙틴 조성이 다양한 품종의 막걸리 특성을 분석하여 막걸리 품질 고급화 및 다양화를 위한 자료를 제공하고자 본 실험을 수행한 결과는 다음과 같았다. ‘고아미2호’, ‘고아미3호’, ‘고아미4호’는 품종별 전분 특성과 호화 특성 분석 결과, 낮은 아밀로펙틴 단쇄 비율과 높은 아밀로스 함량에 기인하여 점성이 낮게 나타남을 확인할 수 있었고, 높은 호화개시온도로 인해 가열흡수비와 팽창용적이 각각 2.09~2.13, 25.02~26.78 ㎤로 다른 품종에 비해 유의하게 낮아, 막걸리 발효에 적합한 전분의 호화가 이루어지지 않음을 확인할 수 있어, 막걸리 제조를 위해 호화를 증진시키기 위한 가공 방법 연구가 필요할 것으로 판단되었다. 품종별 막걸리의 품질 특성은 ‘설갱’, ‘백진주’, ‘일품’의 알코올 함량은 17.3~18.0% 범위로 통계적인 유의차는 없었으나, ‘고아미2호’와 ‘고아미3호’, ‘고아미4호’는 10.0~10.5%로 상대적으로 낮은 알코올 함량을 나타내었고, 당도 또한 ‘설갱’, ‘백진주’, ‘일품’에 비해 절반 가까이 낮았으나, pH와 산도는 품종 간 유의한 차이를 나타내지 않았다. 또한 원료곡에서 높은 난소화성 다당류 함량을 지닌 ‘고아미4호’ 등은 막걸리에서도 역시 난소화성 다당류 함량이 유의하게 높아, 향후 막걸리 제품으로 이용 시 건강 기능성에 기여할 가능성이 높을 것으로 기대되었다. 결과적으로 아밀로펙틴 조성과 난소화성 다당류 함량에서 차이를 보인 ‘고아미2호’, ‘고아미3호’, ‘고아미4호’ 막걸리의 높은 제조수율과 난소화성 다당류 함량 및 낮은 알코올 함량과 당도를 확인하였으며, 지속적인 발효 공정 연구를 통해 국내 기능성 품종을 이용한 고품질 막걸리 개발이 필요할 것으로 판단된다.

가공식품의 원료로 널리 사용되고 있는 옥수수, 감자, 고구마 전분에 멥쌀 및 찹쌀로부터 분리한 전분을 일부(10-30%) 대체하여 신속점도측정기(RVA)로 호화특성을 조사하였다. 쌀 전분은 호화개시온도가 옥수수, 감자, 고구마전분에 비해 낮았고 페이스트 점도가 타 전분에 비해 낮은 경향이었다. 멥쌀 전분의 호화개시온도는 찹쌀 전분에 비해높았으며 최고점도, breakdown이 보다 높게 나타났다. 옥수수 전분에 멥쌀 및 찹쌀 전분을 10-30% 대체하여 RVA 호화양상을 측정한 결과 쌀 전분의 첨가는 RVA 최고점도, trough 점도를 증가시켰으나 최종점도에는 큰 증가세를 보이지 않아 setback은 다소 감소하는 경향이었다. 찰옥수수 전분에 쌀 전분의 첨가는 옥수수 전분과는 달리 RVA 최고점도를 감소시켰으며 최종점도는 증가세를 나타내 setback이 증가하는 것으로 나타났다. 감자 전분에 쌀 전분의 첨가는 최고점도, trough 점도, 최종점도를 다소 감소시켰으나 여전히 높은 점도를 유지하는 것으로 나타났으며setback 역시 여전히 낮게 유지됨을 보여주었다. 고구마 전분에 쌀 전분의 첨가는 전분 paste의 최고점도, trough, 최종점도가 감소하는 결과를 초래하였다. 밀가루에 쌀 전분을 대체시에 멥쌀 전분은 밀가루의 페이스트 점도를 증가시키는 반면에 찹쌀 전분은 전반적으로 점도를 감소시키는 것으로 나타났다.

The quality characteristics of Korean rice cakes (Karedduk) with a mixture of maltooligosaccharide and OSA (octenyl succinic acid starch) added, after 2 and 24 hr of storage at 5℃, was analyzed. A central composite design was used for arrangement of treatment. The two independent variables selected for retarding retrogradation analysis were amounts of maltooligosaccharide (x) and OSA (y). Maltooligosaccharide was added at 0, 3, 6, 9, and 12% levels, and OSA added at 0, 0.3, 0.6, 0.9, and 1.2% levels, to dry rice flour. The texture properties analysis using a Texture Analyzer revealed that the springiness and cohesiveness (p<0.01), chewiness, gumminess and hardness (p<0.001) were significantly different after 24 hr of storage at 5℃. The effect of retarding retrogradation of Korean rice cakes with added mixtures of maltooligosaccharide and OSA showed an increasing trend as the amount of maltooligosaccharide increased. Overall, the instrumental texture properties were highly correlated with the sensory characteristics. These results suggest that adding a mixture of 6% maltooligosaccharide and 0.6% OSA to Korean rice cakes (Karedduk) is effective for retarding retrogradation.

Male weanling Sprague Dawley rats were used to evaluate the effect of dietary rice starch with different particle size on growth performance, intestinal function and proliferation. There were two dietary treatment: rice starch (RS), ultra finely pulverized rice starch with less than 15μm size (PRS). They were eight rats per treatment. In vitro digestibility, body weight change and organs weight were evaluated. Serum GPT, GOT and blood urea nitrogen were analyzed. Transit time, short chain fatty acid contents of cecum, and cell proliferation of duodenum and jejunum were measured. In vitro digestibility of PRS was higher than that of RS. Rats fed ultra finely pulverized rice starch for 3 weeks grew faster than rats fed rice starch. PRS group has higher weights of liver, kidney, spleen and epididymal fat pad, perhaps as a result of increased digestibility. GPT and GOT were not different between two groups. Blood urea nitrogen was higher in RS-fed rats than that of PRS-fed rats. Feeding ultra finely pulverized rice starch resulted in a proliferation of duodenum significantly. These results suggest that ultra finely pulverized rice starch increases the growth performance in weanling animals with reduced number of cells in the cell cycle of small intestine.

Tarakjuk with different amylose content was made up using roasted rice flours that consisted of the highest enzyme-resistant starch (RS), while differential scanning calorimetry (DSC) was also utilized to measure the gelatinization temperature of these roasted rice flours in order to establish cooking temperature of tarakjuk. The following qualities of tarakjuk with different amylose content were studied: color, viscosity, spreadability, starch fractions involving total starch (TS), rapidly digestible starch (RDS), slowly digestible starch (SDS) and RS, in vitro starch digestibility (IVSD) and sensory properties. During experimentation, it was found that as the amylose content of the rice flour decreased, the L value of tarakjuk decreased, whereas a value increased significantly (p〈0.05). Also, while viscosity showed to increase significantly (p〈0.05), on the opposite end, the property of spreadability decreased. TS ranged from 15.95~17.31%, RDS 9.36~10.16%, SDS 5.46~6.91% and RS 0.33~1.07%, on a dry basis. Although the amylose content of rice flours decreased, IVSD increased, however showing no significant difference. When testing the sensory properties of tarakjuk, color and viscosity increased, whereas clumpiness decreased. Ilpum tarakjuk showed the highest score for nutty taste and overall acceptance levels. In fact a high correlation was shown between nutty taste and overall acceptance level (p〈0.01), which leads one to believe that nutty taste is a prime factor that greatly influences overall acceptance. Furthermore, viscosity was positively correlated with both a and b values, however negatively correlated with L value (p〈0.05). Moreover, roasted nutty taste and overall acceptance were positively correlated with a value (p〈0.05), respectively. In conclusion, the above results suggest that tarakjuk could be made by choosing the appropriate rice flour based on the nutritional or sensory purpose.

Male rats were fed a purified diet containing one of 3 experimental diets, gelatinized rice starch that was not modified physically (RC), gelatinized physically modified rice starch using ultrasonic homogenizer(RU), gelatinized physically modified rice starch using hydroshear homogenizer(RH) during 28 days. RC was used as the rice starch control. Feeding a physically modified rice starch (RU) caused an increase in liver weight and RH increased RNA and protein contents in kidney significantly although there were no differences in food intakes compared to feeding a RC diet. The wet weight of liver, kidney and heart were higher in RU. The wet weights of fecal output of the rats fed RH was greater than in rice control group. The gut transit time was longer in the rats fed RH than in the rice control group significantly. Serum GOT, GPT, total bilirubin concentration were tended to be lower and blood urea nitrogen was significantly lower in RH group. The maturation index of kidney was higher in RU than in RC. These results suggest that physically modified rice starch improved growth performance and physiological functions in organs of growing rats.

The relationship between mean air temperature after heading and starch characteristics of colored rice grains was investigated using three colored rice cultivars. Pasting temperature within each rice cultivar with different harvest times differed. The pasting temperatures of two rice cultivars, Hongjinju and Joseongheugchal, reached the highest at 40 days after heading and decreased during the late harvest time. Distribution of amylopectin in the Hongjinju rice cultivar at the earlier harvest time contained a greater number of very short chains with the degree of polymerization (DP) between 6 and 12 and fewer chains with a DP from 13 to 24 than that of the later harvest time. However, there was little difference in the distribution of the longer chains of 25 ≤ DP ≥ 36 and 37 ≤ DP for latter harvest times compared to that of the earlier ones. It was suggested that the structure of amylopectin affected the varietal differences in patterns of chain length of amylopectin during grain filling. In addition, the control of ripening was different from that causing the pigment effects in the fine structure of amylopectin in the three colored rice cultivars. Larger starch granules were observed in the Joseongheugchal rice cultivar and smaller granules occurred in the Hongjinju rice cultivar. The present study revealed that later harvest times led to a clear increase in the mean granule size of starch in the three colored rice cultivars.

We investigated physicochemical properties of puffed snacks with intermediate and high amylose rice varieties. The intermediate amylose rice varieties ‘Sindongjin’ and high amylose rice varieties newly developed for food processing, ‘Dodamssal’ and ‘Goami4’ were tested for this study. The crude fat and crude protein contents of the rice cultivars ranged 1.47-3.08% and 6.30-7.63%, respectively. The resistant starch and amylose contents of Dodamssal and Goami4 were higher than those of Sindongjin. The hardness of rice was the highest in Sindongjin and Dodamssal. Also, Hardness of puffed snacks decreased by 72.07% for Sindongjin, 88.21% for Dodamssal and 66.67% for Goami4 compared to raw rice samples. The sensory evaluation showed that the highest scores in taste, texture and overall acceptability of puffed snacks were obtained in Dodamssal. The results of this study indicate that Dodamssal was suitable varieties for puffed snacks. Also, the physicochemical properties of Dodamssal were improved by the extrusion process. Therefore Dodamssal can be used for the industrial production of puffed snacks.

Three different transplanting dates for two rice cultivars grown in Daegu, Republic of Korea, were examined to identify the changes in growth, rice quality, and characteristics of amylopectin. An early transplanting date caused a reduction in the number of panicles in both rice cultivars compared to that in the optimal and late transplanting dates. The 1000-grain weight in the two rice cultivars was significantly increased in the late transplanting date. The rice cultivar tolerant to high temperatures, Donganbyeo, exhibited the lowest milky grain rate in the late transplanting date. The highest rate of head grain was observed in the late transplanting date in both rice cultivars. Regarding the pattern of pasting properties, peak viscosity increased with delayed transplanting dates. With respect to changes in the amylopectin branch-chain length distribution, the amylopectin structure of the translucent Dongan rice cultivar transplanted on April 25 was characterized by a significant increase in A chains with DP > 12, and a decrease in long chains DP ≥ 37 compared to that transplanted on June 25. In contrast, the amylopectin structure of the chalky Dongan rice cultivar transplanted on April 25 exhibited further decrease in 13 < DP < 19 than that transplanted on June 25. In the Ungwang rice cultivar, the amylopectin structure of the translucent Ungwang rice cultivar transplanted on April 25 and June 25 was characterized by a significant decrease in the lengths of total amylopectin chains. Furthermore, the amylopectin structure of the chalky Ungwangbyeo rice cultivar transplanted on April 25 was characterized by a significant increase in 7 < DP < 30, while a significant decrease was observed in that transplanted on June 25. These results indicate that the amylopectin structure is altered by different transplanting dates depending on the characteristics of the rice cultivar.

We investigated the physicochemical properties and starch structure of various rice varieties including 15 colored cultivars. NKHC showed the highest level of protein, lipid, and total dietary fiber levels. Reddish brown rice showed higher lipid content than that in black rice cultivars. Apparent amylose content of waxy and non-waxy colored rice varieties was within the range of 3~5% and 15~18%, respectively. IP exhibited the highest total starch (TS) content, whereas, NKHC and HJJ showed lower TS content than that in other cultivars. Pasting temperature of all colored rice cultivars, except IP, was about 68°C. Peak viscosity of IP, JJJ, Hong, and GGHM showed high values of 138, 130, 128, and 124, respectively. All the colored rice cultivars presented A-type X-ray diffraction pattern and polygonal shapes of starch granules were observed using scanning electron micrographs (SEM). Major groups of amylopectin chain lengths were B (12 < DP ≤ 24) and A (DP ≤ 12). SMHC showed the highest B chain content and the lowest A chain content (P < 0.05). These experimental results provided useful information for scientists and the food industry regarding colored rice starches.