Mi-Ra Yoon

Changes in Quality Properties of Brown Rice after Germination

The objective of this study was to evaluate quality properties, including amylose, alkali digestion value (ADV), and amylogram, of brown rice and germinated brown rice of some cultivars in Korea for rice processing products. The protein content of brown rice was significantly higher than those of germinated brown rice. The amylose content of the samples ranged from 17.09 to 18.85%. Alkali digestion value (ADV) of brown rice and germinated brown rice were described as a grade of 2-5 and 4-7, respectively. In a rapid visco analyzer (RVA) examination, pasting temperature of brown rice and germinated brown rice was 67.93-68.05℃. In addition, the pasting characteristics of brown rice were significantly higher than those of germinated brown rice. A texture analysis test showed that germinated brown rice Haiami had the lowest hardness and germinated brown rice Samkwang had the highest adhesiveness.

The lipid composition of rice cultivars with different eating qualities

Lipid composition of three rice varieties (Koshihikari, Dongjin, and Singeumo) with varying palatability was investigated. Results from both Toyo taste and sensory analyses indicated that Koshihikari, Dongjin, and Singeumo have high, medium, and low eating qualities, respectively. Koshihikari was also found to have better texture properties and higher Mg/K ratio, indicating a better eating quality. Major fatty acids found in both starch and nonstarch lipids of rice were linoleic, oleic, and palmitic acids. Dongjin contained the highest non-starch lipid content, but also had the lowest starch lipid level. Oleic acid concentrations were higher in both the high-palatable Koshihikari and low-palatable Singeumo than in Dongjin, whereas Dongjin showed high levels of palmitic and linoleic acids. Squalene, campesterol, and cycloartenol contents were substantially higher in Koshihikari than in the rice varieties with lower palatability. These findings demonstrate that rice concentrations of plant sterols, particularly cycloartenol and squalene, appear to have a positive effect on its palatability.

Morphological and starch characteristics of the Japonica rice mutant variety Seolgaeng for dry-milled flour

Producing good-quality, fine rice flour is more difficult than wheat flour because the rice grain is harder. The non-glutinous Japonica-type variety Seolgaeng, derived from N-methyl-N-nitrosourea (MNU) mutagenesis, and four other varieties, representing a range of amylose contents, were evaluated in this study. Dry-milled Seolgaeng rice flour exhibited an average particle size that is <70 μm, a more uniform particle-size proportion than other varieties. Moreover, we noted significant differences in the damaged starch content in flour from Seolgaeng compared to the other varieties (p<0.05). Seolgaeng flour showed a round starch structure, which would lead to better friability, finer particle size, and less damage to the endosperm during dry milling. Indeed, among all varieties evaluated in this study, dry-milled Seolgaeng flour had the finest particle size (averaging <70 μm) and exhibited less damaged starch. With its round starch granules, Seolgaeng is a suitable candidate for drymilled rice flour.

Content and characteristics of resistant starch in high amylose mutant rice varieties derived from Ilpum.

This study was conducted to analyze the starch characteristics of three rice cultivars, Goami 2, Goami 3 and Goami 4 with high amylose content and resistant starch. These rice varieties were developed by mutation breeding based on N-methylN-nitrosourea (MNU) treatment in a japonica variety, Ilpum. Resistant starch contents of three high amylose mutant rice varieties and Ilpum were 11.87~13.69% and 0.36%, respectively. The X-ray diffraction patterns of starches of three varieties, Goami 2, Goami 3 and Goami 4 displayed B-type pattern. The proportion of amylopectin short chains of 6 to 12 in DP of the high amylose mutant rice varieties was significantly lower than that of Ilpum. Resistant starch contents had positive correlation with the amylose content, total dietary fiber content, medium length chains of 13 to 24, long chains of ≥ 25 in DP of amylopectin, pasting temperature and setback viscosity.

A study on the lipid components of rice in relation to palatability and storage

AbstactFor better understanding of the relationship between palatability and lipid components of rice, seven Korean rice varieties (Samkwang, Gopum, Chucheong, Ilpum, Palgong, Samnam, and Dobong), with a wide variation in palatability, were selected and analyzed for their lipid composition, including starch lipids, non-starch lipids, plant sterols, and lipase and lipoxygenase activities, as well as changes in the lipid properties of rice during storage. Samkwang and Dobong were shown to have the highest (77.2) and lowest (54.2) palatability scores, respectively, The rice varieties with high palatability scores showed significantly higher starch lipid and linoleic acid contents. Furthermore, they contained higher cycloartenol and lower concentrations of campesterol and stigmasterol. Low-palatable varieties exhibited higher activities of lipase and lipoxygenase. The palatability of all samples deteriorated after storage, which could be attributed to decreased concentrations of non-starch lipid and linoleic acid, increased oleic acid and palmitic acid contents, and increased amounts of squalene and phytosterols. These findings suggest that new lines of rice with enhanced palatability could be developed by modifying specific components in the lipid fraction of rice.

Contrasting tocol ratios associated with seed longevity in rice variety groups

Vitamin E (tocols) is a key metabolite for efficient scavenging of lipid peroxy radicals that cause membrane breakdown during seed ageing. However, in rice, this hypothesis has been tested for very few lines only and without considering intraspecific variation in genomic structure. Here, we present a correlation study between tocols and seed longevity using a diverse rice panel. Seeds of 20 rice accessions held in the International Rice Genebank at the International Rice Research Institute, representing Aus, Basmati/Sadri, Indica, temperate Japonica and tropical Japonica variety groups, were used for tocols analysis (quantification of α-, β-, γ- and δ-tocopherol/tocotrienol by ultra-performance liquid chromatography) and storage experiments at 45°C and 10.9% seed moisture content. To examine the effects of DNA-haplotype on the phenotype, the 700 K high-density single-nucleotide polymorphism marker dataset was utilized. Both seed longevity (time for viability to fall to 50%; p 50 ) and tocols content varied across variety groups related to the heterogeneity in the genetic architecture. Among eight types of tocol homologues, α-tocopherol and γ-tocotrienol were significantly correlated with p 50 (negatively and positively, respectively). While temperate Japonica varieties were most abundant in α-tocopherol, Indica varieties recorded 1.3- to 1.7-fold higher γ-tocotrienol than those of other groups. We conclude that the specific ratio of tocol homologues rather than total tocols content plays an important role in the seed longevity mechanism.

Identification of novel mutations in the rice starch branching enzyme I gene via TILLING by sequencing

Starch branching enzymes (SBEs) incorporate α-1,6-branched glucosidic linkages into α-1,4-glucan chains. Rice has three SBE isoforms (SBEI, SBEIIa, and SBEIIb), which differ in the amylose chain lengths that they transfer to amylopectin. SBEI mutants characterized to date have had little or no effect on starch structure or content. In this study, TILLING by sequencing was employed to identify SBEI mutations in a population of chemically induced mutants of the cultivar Nipponbare (n = 4096), resulting in the detection of 37 putative mutations. After removing mutations in introns or predicted to be synonymous, Sanger sequencing of M2 and M3 generation mutants confirmed six mutations and homozygous lines for four of these mutations were isolated. Only one line, NM-4936, exhibited a visible grain phenotype and produced sufficient M4 seeds for morphological and physicochemical analyses. In contrast to Nipponbare, NM-4936 grains are opaque due to rounded, loosely packed starch granules, and consequently, grain hardness was significantly reduced. NM-4936 grains exhibited significantly reduced width and thickness, which is reflected in reduced grain weight. Physicochemical analysis revealed significant differences in apparent amylose content (15 vs. 19%) and protein content (9.2 vs. 4.8%). Amylopectin chain-length distribution analysis indicated that the mutant has a slight but significant decrease in B3 chains [degree of polymerization (DP) ≥ 37, P < 0.01] and a very slight but significant increase in B1 chains (DP 13–24; P < 0.05). Identification of novel SBEI mutations will be useful in elucidating its function and may provide useful germplasm for breeding novel quality traits.

Effect of rice variety on the processability for preparing rice cookies

This study aimed at investigating the influence of different rice varieties (Palbangmi, Saegoami, Mimyeon, Dasan-1, Hanarm, Boramchan, and Baegjinju) on the preparation process of rice cookies. Rice grains were pulverized by dry milling and subsequently screened using a 100-mesh sieve. Dasan-1, Hanarm, and Palbangmi flours showed low water absorption index (WAI) compared to other rice flours. The spread ratios of the cookies prepared with Dasan-1, Hanarm, and Palbangmi flours reached higher values than those obtained with other rice varieties. As a result, the hardness of the cookies prepared with Dasan-1, Hanarm, and Palbangmi flours was relatively low. On the contrary, cookies prepared with Saegoami, Boramchan, and Baegjinju flours showed inadequate qualities because they contained relatively high levels of damaged starch, which increased water absorption in the cookie dough. The WAI value of rice flour could be the most important indicator to determine the quality of rice cookies.

Comparative Analysis on Quality and Bread-making Properties by Particle Size of Dry-Milled Rice Flours of Rice Varieties

This study was conducted the comparative analysis on quality and rice bread process suitability properties by four particle size classification of dry-milled flours for four rice varieties. Dry-milled rice flours were prepared by dry milling and classified according to particle size using 100, 150, 200, and 250 mesh sieves. The mean particle size by four particle size classification of 60 ~ 100 mesh, 100 ~ 150 mesh, 150 ~ 200 mesh, 200 ~ 250 mesh exhibited 118.9 μm, 87.4 μm, 65.3 μm, 46.1 μm, respectively. The particle size of dry-milled rice flours was the finer, the damaged starch content was the higher (r = − 0.570*). The particle size also had significant negative correlation with the water absorption index (r = − 0.533*, r = − 0.593*), and water solubility index (r = − 0.857**, r = − 0.584*). Dry-milled rice flours with particle size of 60 ~ 70 μm, passed through 150 and 200 mesh sieves exhibited the highest specific volume of rice bread. Whereas, the dry-milled rice flour with finer particle size above 200 mesh showed the lowest specific volume of rice bread. These results will be applied as a quality standard to aid in the selection of the most suitable dry-milled rice flour for baking.

Quality Properties of Makgeolli Brewed with Fiber-rich Rice Cultivars

Goami2, Goami3 and Goami4 were identified as fiber-rich rice cultivars which were developed by mutation breeding with Ilpum. The purpose of this study was to develop a method for producing Makgeolli with the fiber-rich rice cultivars, Goami2, Goami3, Goami4, and to investigate the characteristics of Makgeolli during the fermentation process. Makgeolli was produced herein by fermentation steamed rice (SR), raw rice flour (RF), and steamed rice flour (SF) from Goami2, Goami3, Goami4, Ilpum and Sealgaeng rice cultivars. The physicochemical characteristics including alcohol and sugar content, pH, total acidity, TDF (total dietary fiber), and color of the Makgeolli samples were analyzed. Makgeolli produced with Ilpum and Sealgaeng showed satisfactory fermention characteristics in alcohol and sugar content when SR, RF and SF were used. In the case of Goami2, Goami3, and Goami4, the use of SF resulted in 17.2~20.1% alcohol content, whereas only 10% alcohol was produced by SR. The sugar contents in the SF-makgeolli samples were also higher (9~10 °Brix) than in the SR-makgeolli (5.35~5.44 °Brix) for Goami2 and Goami4 cultivars. The dietary fiber contents of the Makgeolli samples produced using SF from the fiber-rich rice cultivars were higher (1.35~1.52 g/100 mL) than those produced with Ilpum and Sealgaeng (0.74~0.87 g/100 mL). From these results, it may be suggested that SF would be an appropriate material to brew Makgeolli using fiber-rich rice cultivars to obtain better physicochemical and functional qualities.