Bong Kyung Koh

Rice varieties in relation to rice bread quality

BACKGROUND It is difficult to predict rice bread quality only from the amylose content (AC) or dough characteristics of new lines produced by rice breeding programmes. This study investigated the AC relative to bread baking quality of rice varieties developed in Korea, and identified specific characteristics that contribute to rice bread quality. RESULTS Manmibyeo, Jinsumi, Seolgaeng and Hanareumbyeo were classified as low AC, YR24088 Acp9, Suweon517, Chenmaai and Goamibyeo as intermediate AC and Milyang261 as high AC. Suweon517, Milyang261 and Manmibyeo had a high water absorption index (WAI), while Goamibyeo, YR24088 Acp9, Jinsumi, Seolgaeng, Hanareumbyeo and Chenmaai had a low WAI. The gelatinisation enthalpy of flour varied from 9.2 J g(-1) in Milyang261 to 14.8 J g(-1) in YR24088 Acp9. After 7 days of storage the rate of flour retrogradation and crumb firmness were weakly correlated, with the exception of Jinsumi. Bread volumes of Jinsumi, Chenmaai, YR24088 Acp9 and Goamibyeo were comparable to that of wheat flour, but the rest were unsuited to bread making because of their low volume and hard crumb texture. CONCLUSION Based on volume, texture and crumb firmness ratio, Chenmaai and Goamibyeo were the most appropriate varieties for making bread. An intermediate AC and low WAI were the primary indicators of rice bread flour quality.

Effects of Ferulic Acid and Transglutaminase on Hard Wheat Flour Dough and Bread

ABSTRACT The effects of ferulic acid and transglutaminase (TG) on the properties of wheat flour dough and bread were investigated. Ferulic acid and TG were blended with hard wheat flour at levels of 250 and 2,000 ppm of flour weight, respectively. The addition of ferulic acid reduced the mixing time and mixing tolerance. The addition of TG did not obviously affect the mixing properties. Significant effects of ferulic acid plus TG on the rested dough texture were observed for overmixed dough. The maximum resistance (Rmax) of the dough was significantly reduced with the addition of ferulic acid but increased with the addition of TG. The addition of TG with ferulic acid restored the Rmax reduced by ferulic acid alone. The proportion of SDS-soluble high molecular weight proteins in the dough increased with the addition of ferulic acid and decreased with TG, when assessed with size-exclusion HPLC fractionation. Although the addition of TG improved the handling properties of the dough made sticky with added fer...

The Effects of Germination, Fermentation, and Fermentation Additives on the Phytate Content of Rice Flour

The phytate contents in nine rice cultivars (Oryza sativa cv.) grown in Korea were investigated and the effects of germination, fermentation, and fermentation additives on the phytate content of rice flour were studied. In nondehulled paddy rice, the phytate content was the highest in Goamibyeo and the lowest in Hanareumbyeo. In milled rice, the phytate content was the highest in Suweon517 and the lowest in Manmibyeo. For Goamibyeo, which had high phytate contents both before and after milling, there was a significant (p<0.05) reduction in the phytate content of paddy rice after germination. The phytate content reduction occurred when germinated paddy flour was fermented at 50°C for 24 h. Paddy rice phytate was completely removed when ammonium sulfate was added to germinated paddy rice flour, which was then allowed to ferment at 50°C for 24 h.

Textural properties of Frozen stored Garaetteok supplemented with Agar and Casein

ABSTRACT The effects of agar and casein on the textural characteristics of frozen stored Garaetteok, a traditional Korean rice cake, were investigated over a 20-d storage period. Garaetteok was made from rice flour with and without the addition of agar (GA), casein (GC), and a mixture of agar and casein (GAC). The moisture content of control Garaetteok (G) significantly (P < 0.001) decreased during frozen storage, whereas those of GA and GAC showed no significant decrease, although GC showed less of a decrease than G. Although the hardness and retrogradation rate of all uncooked Garaetteoks significantly (P < 0.05) increased during frozen storage, the retrogradation rate of GC did not significantly increase. After cooking, GC was the least hard and had relatively low adhesiveness and no significant (P < 0.05) difference in cohesiveness and springiness regardless of frozen storage time. These results indicated that casein was an effective additive for frozen stored Garaetteok with relatively minimal impact on textural properties compared with G. However, although agar maintained the moisture content, it was not an effective additive because of the increase in the hardness and adhesiveness of cooked Garaetteok regardless of frozen storage time.