• KOREAN JOURNAL OF CROP SCIENCE
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• v.47
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• pp.15-32
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• 2002

The endeavors enhancing the grain quality of high-yielding japonica rice were steadily continued during 1980s-1990s along with the self-sufficiency of rice production and the increasing demands of high-quality rices. During this time, considerably great progress and success was obtained in development of high-quality japonica cultivars and quality evaluation techniques including the elucidation of interrelationship between the physicochemical properties of rice grain and the physical or palatability components of cooked rice. In 1990s, some high-quality japonica rice cultivars and special rices adaptable for food processing such as large kernel, chalky endosperm, aromatic and colored rices were developed and its objective preference and utility was also examined by a palatability meter, rapid-visco analyzer and texture analyzer, Recently, new special rices such as extremely low-amylose dull or opaque non-glutinous endosperm mutants were developed. Also, a high-lysine rice variety was developed for higher nutritional utility. The water uptake rate and the maximum water absorption ratio showed significantly negative correlations with the K/Mg ratio and alkali digestion value(ADV) of milled rice. The rice materials showing the higher amount of hot water absorption exhibited the larger volume expansion of cooked rice. The harder rices with lower moisture content revealed the higher rate of water uptake at twenty minutes after soaking and the higher ratio of maximum water uptake under the room temperature condition. These water uptake characteristics were not associated with the protein and amylose contents of milled rice and the palatability of cooked rice. The water/rice ratio (in w/w basis) for optimum cooking was averaged to 1.52 in dry milled rices (12% wet basis) with varietal range from 1.45 to 1.61 and the expansion ratio of milled rice after proper boiling was average to 2.63(in v/v basis). The major physicochemical components of rice grain associated with the palatability of cooked rice were examined using japonica rice materials showing narrow varietal variation in grain size and shape, alkali digestibility, gel consistency, amylose and protein contents, but considerable difference in appearance and texture of cooked rice. The glossiness or gross palatability score of cooked rice were closely associated with the peak, hot paste and consistency viscosities of viscosities with year difference. The high-quality rice variety "IIpumbyeo" showed less portion of amylose on the outer layer of milled rice grain and less and slower change in iodine blue value of extracted paste during twenty minutes of boiling. This highly palatable rice also exhibited very fine net structure in outer layer and fine-spongy and well-swollen shape of gelatinized starch granules in inner layer and core of cooked rice kernel compared with the poor palatable rice through image of scanning electronic microscope. Gross sensory score of cooked rice could be estimated by multiple linear regression formula, deduced from relationship between rice quality components mentioned above and eating quality of cooked rice, with high probability of determination. The $\alpha$-amylose-iodine method was adopted for checking the varietal difference in retrogradation of cooked rice. The rice cultivars revealing the relatively slow retrogradation in aged cooked rice were IIpumbyeo, Chucheongyeo, Sasanishiki, Jinbubyeo and Koshihikari. A Tonsil-type rice, Taebaegbyeo, and a japonica cultivar, Seomjinbyeo, showed the relatively fast deterioration of cooked rice. Generally, the better rice cultivars in eating quality of cooked rice showed less retrogradation and much sponginess in cooled cooked rice. Also, the rice varieties exhibiting less retrogradation in cooled cooked rice revealed higher hot viscosity and lower cool viscosity of rice flour in amylogram. The sponginess of cooled cooked rice was closely associated with magnesium content and volume expansion of cooked rice. The hardness-changed ratio of cooked rice by cooling was negatively correlated with solids amount extracted during boiling and volume expansion of cooked rice. The major physicochemical properties of rice grain closely related to the palatability of cooked rice may be directly or indirectly associated with the retrogradation characteristics of cooked rice. The softer gel consistency and lower amylose content in milled rice revealed the higher ratio of popped rice and larger bulk density of popping. The stronger hardness of rice grain showed relatively higher ratio of popping and the more chalky or less translucent rice exhibited the lower ratio of intact popped brown rice. The potassium and magnesium contents of milled rice were negatively associated with gross score of noodle making mixed with wheat flour in half and the better rice for noodle making revealed relatively less amount of solid extraction during boiling. The more volume expansion of batters for making brown rice bread resulted the better loaf formation and more springiness in rice breed. The higher protein rices produced relatively the more moist white rice bread. The springiness of rice bread was also significantly correlated with high amylose content and hard gel consistency. The completely chalky and large grain rices showed better suitability far fermentation and brewing. The glutinous rice were classified into nine different varietal groups based on various physicochemical and structural characteristics of endosperm. There was some close associations among these grain properties and large varietal difference in suitability to various traditional food processing. Our breeding efforts on improvement of rice quality for high palatability and processing utility or value-adding products in the future should focus on not only continuous enhancement of marketing and eating qualities but also the diversification in morphological, physicochemical and nutritional characteristics of rice grain suitable for processing various value-added rice foods.ice foods.

• Korean Journal of Food Science and Technology
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• v.23 no.5
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• pp.633-641
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• 1991

Mook, a traditional gel food in Korea, has been made from mainly acorn, buckwheat, and mungbean starches (Mook Starches). Corn, rice, wheat starches (Non-Mook Starches) are not used due to their weak gelation power. In order to know the effects of properties of starch on gelation, some physicochemical properties, molecular structure, and starch lipid of these six starches were investigated and compared with gel hardness. Both amylose content and gel hardness of starches were in order of mungbean, acorn, buckwheat, wheat, corn, and rice and these two parameters showed a very good correlation (r=0.95). The amyloses of Mook Starches had larger molecular size (${\overline}D.P._{n}=1,080{\sim}1,580\;vs\;670{\sim}1,120$ for Mook Starches and Non-Mook Starches, respectively), more average number of chain ($2.9{\sim}5.4\;vs\;1.7{\sim}2.5$), and shorter average chain length ($290{\sim}390\;vs\;390{\sim}450$) than those of Non-Mook Starches. Also, Mook Starches had longer average chain length ($22.2{\sim}22.6\;vs\;18.9{\sim}21.3$) of amylopectin and less starch lipid content ($0.12{\sim}0.49\;vs\;0.68{\sim}1.26%$) than Non-Mook Starches. These properties had good correlations with gel hardness (r=0.76-0.84). Consequently, the gelation power of Mook Starches was thought to be derived from their high amylose content and other properties of starches.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.9
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• pp.1300-1306
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• 2011

This study investigated the physicochemical characteristics of wet-milled rice flour treated with pectinase and cellulase in a steeping process. Enzyme treatments were used as follows: pectinase 0.05%, cellulase 0.05%, and mixed enzyme treatments 0.05~0.2%. For particle distribution, rice flour E-treated with mixed enzymes (pectinase 0.05% and cellulase 0.05%) was the finest at 48.3% particle distribution less than $53\;{\mu}m$. Protein contents and damaged starch were reduced by enzyme treatments. Damaged starch was the lowest (12.1%) in rice flour E compared with non-enzyme treatment (18.1%). Amylose content, water binding capacity, solubility, and swelling power all increased upon enzyme treatments, and their effects increased upon mixed enzyme treatment. For gelatinization characteristics of RVA, peak viscosity, final viscosity, breakdown, and total setback viscosity increased in rice flours treated with mixed enzymes. Especially, in steeping method with mixed enzyme treatment, pectinase 0.05% and cellulase 0.05% treatment was suitable for minimizing damaged starch and high fine particle distribution of rice flours compared with single enzyme treatment.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.8
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• pp.1076-1083
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• 2009

The physicochemical properties of rice flour produced by 3 different grinding methods using various steeping times (3, 6, 9, and 12 hrs) were investigated. Roller mill gave coarse rice flour; the pin mill, intermediate flour; and mixed when both (roller & pin mills) were used. With the increase of steeping times, the rice flours became finer and the contents of crude protein, crude fat and crude ash decreased. Damaged starch was noticeably high in rice flour by roller & pin mills compared to those by roller or pin mills alone. Amylose contents, solubility and swelling power increased as the steeping times increased. Water binding capacity was the highest in roller & pin mills, followed by pin mill. In scanning electron microscope (SEM), pin mill showed distribution of separated fine particles of rice flours. The physicochemical properties of rice flours showed many differences by steeping times of rice and grinding methods. With sufficient steeping times, the rice flours obtained from pin mill were relatively fine having less damaged starch.

• Korean Journal of Food Science and Technology
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• v.51 no.6
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• pp.509-516
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• 2019

In this study, the general components, particle size, starch content, hydrolysis index (HI), and estimated glycemic index (eGI) of 'Ilpum', a medium-amylose rice cultivar, were compared with those of 'Dodamssal', a high-amylose rice cultivar containing resistant starch. The volume weighted mean was significantly smaller in 'Dodamssal' than in 'Ilpum'. The resistant starch content of 'Dodamssal' was about 13% and there were no differences in terms of particle size. The HI and eGI were found to be significantly higher in 'Ilpum', and there were no statistical differences in 'Dodamssal' except for samples with an average particle size of less than 50 ㎛. Therefore, 'Dodamssal' was concluded to be valuable as a health-food material since it is easily ground evenly when processed into rice flour, contains resistant starch, and has a low glycemic index. These results could be used as basic data for developing processed 'Dodamssal' rice-based products.

• Food Science and Preservation
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• v.22 no.1
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• pp.63-69
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• 2015

The highly producible rice cultivars, hanareum and dasan 2, were prepared and investigated for their physicochemical properties, and the quality characteristics of frozen cookie dough with rice flour according to the thawing time were measured. The water, ash, crude protein, amylose, and damaged starch contents of rice flour, as well as its water holding capacity, particle size, and Hunter color value, were measured. The water, ash, and crude protein contents of the hanareum and dasan 2 rice flours were shown to range from 7.28 to 13.14%, from 0.35 to 0.39, and from 6.05 and 8.68%, respectively. The protein content of the control group was higher than that of hanareum and dasan 2 rice flours. The amylose contents of the hanareum and dasan 2 rice flour were 19.05 and 23.04%, respectively. The damaged starch content and water holding capacity of the control group were lower than those of the hanareum and dasan 2 rice flours. The particle sizes of the samples were $48.54{\sim}50.05{\mu}m$. The lightness values of the hanareum, and dasan 2 rice flour, and of the control were 93.72, 93.51 and 92.63, respectively. The quality characteristics of the gluten-free frozen cookie dough were investigated. The lightness of the cookie made with frozen cookie dough decreased according to the by thawing time, but the diameter of the cookie did not differ significantly. The hardness of the cookie made with rice frozen dasan 2 rice dough was lower than that of the cookie made with frozen hanareum rice dough.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.3
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• pp.184-192
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• 2017

Rice flours from five rice (Oryza sativa L.) varieties with different amylose content were prepared by both wet and dry milling processes. The moisture content of wet-milled rice flours (WMR) was approximately three-times higher than that of dry-milled rice flours (DMR). Water absorption index (WAI), water solubility index (WSI), and swelling power (SP) increased in proportion to temperature. The WAI, WSI and SP values of DMR were higher than those of WMR. Baeokchal (BOC), which is a waxy rice cultivar, had a significantly high WSI value. Pasting properties of DMR, except for the BOC cultivar, resulted in an increase in peak, trough, final, and setback viscosities. The levels of resistant starch in four cultivars, except for Dodamssal (DDS), were under 1%, irrespective of the milling process, whereas the resistant starch contents of DMR and WMR in DDS were 9.18% and 6.27%, respectively. In vitro digestibility of WMR was higher than that of DMR, and the estimated glycemic index of the rice flour varieties ranged from 57.6 to 81.3. Damaged starch content of WMR was less than that of DMR; in addition, a negative correlation was observed between the amylose and damaged starch contents of WMR. These results suggest that the properties of rice flour vary depending on the milling method and flour variety, and could be a reference for selecting the appropriate processing method.

• The Korean Journal of Food And Nutrition
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• v.34 no.5
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• pp.458-467
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• 2021

The effect of 16 cultivars on the quality of the rice porridge was investigated. The 'Geunnun' had the highest water absorption rate, but the 'Segyejinmi' yield (w/w) was the highest. The total sugar content of the rice porridge was 0.29~8.10%, showing significant variation among the cultivars. High amylose 'Dodamssal' and 'Hwaseonchalbyeo' glutinous rice displayed rotational viscosities of <20,000 cP. Rotational viscosities for boiled rice cultivars were 30,000~40,000 cP, representing an intermediate level, and the rotational viscosities of 'Geonyang2' and 'Hanareum4' were over 50,000 cP. These results suggest that the viscosity of rice porridge varies significantly among raw material cultivars. Among other variables affecting the texture profile of rice porridge, there were significant differences in hardness and gumminess among the cultivars. As a raw material, 'Baekokchal', a kind of glutinous rice, is known to be whiter than the non-glutinous rice, but after processing to porridge, it showed the lowest L value (71.1). Starch degrading enzyme activity was not significant in most types of rice porridges within 30 or 60 minutes. Therefore, enzymatic starch degradation is thought to be completed within 30 minutes. Among the tested raw materials, 'Miho' was 73.5 ㎍/mg, indicating the best digestibility in vitro.

• Korean Journal of Food Science and Technology
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• v.36 no.5
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• pp.765-772
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• 2004

Cooking condition of Tarakjuk (milk-rice porridge) was established based on gelatinization temperature using differential scanning calorimetry (DSC) of roasted Ilpum rice flour, which has highest enzyme-resistant starch (RS) content. Effect of cooking temperature and time on DSC characteristics, crystallity with X ray diffractogram, RS content, in vitro starch digestibility (IVSD), amino acid composition, and in vitro protein digestibility (IVPD) of Tarakjuk were determined. Tarakjuk was cooked at 50, 56.5, 64, and $69^{\circ}C$ for various durations. Rice flour ingredient used was Ilpum, previously roasted at $185^{\circ}C$ for 25 min. Tarakjuk cooked at 50 and $56.5^{\circ}C$ showed two thermal transitions between $63.7-125.2^{\circ}C$ as determined by DSC, corresponding to endotherms of starch gelatinization $(63.7-73.8^{\circ}C)$ and melting of amylose-lipid complex (AM-lipid complex, $97.7-125.2^{\circ}C$), whereas that cooked at 64 and $69^{\circ}C$ showed only AM-lipid complex melting transition between $96.9-127.6^{\circ}C$. As cooking temperature increased, RS content of Tarakjuk decreased, whereas IVSD increased. Total amino acid content was between 11,558-15,601mg/100g, depending on cooking condition used. Compared with conventionally made control, contents of essential amino acids, such as lysine and tryptophane, were higher at 50 and $56.5^{\circ}C$, and IVPD showed higher increase. Results reveal degree of gelatinization in Tarakjuk with high RS content as well as low IVSD and high IVPD, which are important from physiological and nutritional point of view, can be produced by controlling cooking condition.

• Applied Biological Chemistry
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• v.38 no.6
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• pp.554-562
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• 1995

Effect of the modification of rice protein by protease and 2-mercaptoethanol on physicochemical and gelatinization properties was investigated for the three cultuvars of rice. Total amylose contents of Chucheongbyeo(japonica type), Chosengtongilbyeo(tongil type, indica x japonica) and IR 36 (indica type) were in the range of $20{\sim}25%$. Total amylose and insoluble amylose content of IR 36 were higher than the others. The differential scanning calorimetric and X-ray diffraction results revealed higher relative crystallinity of IR 36 than the others. Water uptake was increased and amylographic viscosity was significantly decreased by 2-mercaptoethanol treatment. Amylographic viscosity was significantly decreased and hot water-soluble carbohydrate content was increased by protease treatment. The proportions of high molecular weight of soluble carbohydrate fractionated by gel filtration chromatography were increased by protease treatment. These effects were most significant in IR 36. This results suggested that starch gelatinization be accelerated by alteration of the protein with protease and reducing agent.