Yoshiko Hibi

Roles of Water-Soluble and Water-Insoluble Carbohydrates in the Gelatinization and Retrogradation of Rice Starch

The rules of water-soluble carbohydrates leached from starch granule and water-insoluble ones left in starch granule in the gelatinization were studied relating to gel hardness in the retrogradation. In the case of whole starch gel, hardness of rice starch gel was lower in the presence of lipids than it was in the absence of lipids, and an increase in hardness during storage at 5 °C was retarded by the presence of lipids. The characteristic of water-insoluble fraction paste of gelatinized normal rice starch was the opposite to that of whole starch gel. This seems to be due to the shortage of amylose in the paste. When the proportion of amylose was high in the mixture of normal rice starch and waxy one, both the water-solubility and the gel hardness were strongly affected by lipids. On the contrary, the effects of lipids were hardly seen when the proportion of amylopectin was high in the mixed starches. Amylopectin of rice starch in the presence of amylose showed a considerable increase in complex formation.

Effect of Retrograded Waxy Corn Starch on Bread Staling

Waxy corn starch pastes (10%) were stored at 5 °C for up to 35 days, and the powder specimens of retrograded starches thus obtained were added to wheat flour for bread baking at a level of 5%. The effect of retrograded starch on the staling of bread was determined. The loaf which contained retrograded waxy corn starch, which was prepared by storing the 10% paste at 5 °C for 7 days, showed an increase in specific volume and the results of the sensory evaluation showed that it was very acceptable. During the storage of bread, the increase in firmness and decrease in degree of gelatinization were suppressed by adding retrograded waxy corn starch. The moisture content of bread crumbs did not relate to firmness. Added retrograded waxy corn starch decreased the final viscosity of flour. The crystalline region of retrograded waxy corn starch used for bread baking included longer chains from amylopectin which in raw starch occurred in the amorphous region.

Pasting Properties of Various Retrograded Starches Isolated with Ethanol

The pasting properties of various retrograded starches were studied by means of RVA. Most retrograded starch pastes showed a low-temperature peak which did not appear in the viscograms of any raw starch sample: for wheat and rice starches, both a high-temperature peak shown in the viscogram of their raw samples and a low-temperature peak appeared, while for other cereal starches and potato starch, only a low-temperature peak was detected in the retrograded paste. The low-temperature peak began to appear when the degree of gelatinization decreased below 60-70%. The viscosity of both peaks tended to increase to a maximum value and then decrease during storage.

The Effects of Chemical Compounds Contained in the Tea Leaves on the Foamability of Matcha.

茶の起泡性に影響を与える茶の成分を明らかにするため,クロロホルム,ヘキサン,エーテルを用いて脱脂し,それぞれの脱脂茶の成分量の変化と起泡性を調べた.脱脂茶の起泡性と泡の比重は脱脂しない抹茶に比べて,それぞれクロロホルム脱脂茶では5.4倍と1.4倍,エーテル脱脂茶では3.8倍と1.8倍,n-ヘキサン脱脂茶では4,6倍と1.5倍であり,いずれも脱脂しない抹茶との間に差が認められた.また,クロロホルム脱脂茶,エーテル脱脂茶,n-ヘキサン脱脂茶それぞれ相互間で起泡性に差が認められた.エーテル脱脂茶では,脂質やカフェインの残存量がn-ヘキサン脱脂茶よりも少ないにもかかわらず起泡性ではエーテル脱脂茶の方が低かったことから考えると,ペクチン,脂質,カフェイン以外にも抹茶の起泡性低下に関与するなんらかの成分が含まれている可能性が示唆された.

Preference for Steamed or Roasted Green Tea in Young and elder Females

1993-1994年に, 若年層 (19-20歳, 183人) と中高年層 (40-70歳, 74人) を対象に蒸し製緑茶と釜妙り製緑茶について色, 香り, 味に関する官能検査および緑茶, 紅茶, コーヒーのいずれの飲物を好むかについてのアンケート調査を実施した.茶抽出液は熊本産の茶葉3gを100m1の熱湯で3分間抽出した.中高年層では蒸し茶の方が色, 香り, 味ともに好ましいとしているが, 若年層では香りは釜妙り茶の方が好ましいと答えた.結論として, 蒸し茶の総合評価には茶の味が関与することが, 釜妙り茶では味と同様に香りも関与することが明らかになった.また, アンケート調査の結果から中高年層では71%の者が緑茶を好み, 若年層では緑茶と同様に紅茶やコーヒーを好むことが明らかになった.