| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系所 === 98 === "Purple jade" is belong to convolvulaceae as the new variety of sweet potato. “TNG73” announced by Agricultural Research Institute in Chia-yi on March 16 , 2007. The first one variety of purple sweet potato was bred in Taiwan. Purple sweet potato is a natural pigment formed by the anthocyanins and flavonoids. The natural pigment of the purple sweet potato is soluble in water and ethanol solution, but it is not soluble in oil and anhydrous ethanol. The stability of the pigment of purple sweet potato is affected by the pH. When the solution is acidic which shows a red or purple-red color, the neutral solution is blue color and the alkaline solution shows unstable color.
This experiment is divided into three stages: The first stage will be prepared for purple sweet potato into different states to make an angel cake, which is boiling mud, raw material powder, freeze-dried powder, hot drying power in 50℃, hot drying power in 80℃. Explore the taste of the impact for an angel cake into different methods and texture by sensory evaluation, experimental analysis shows that adding purple sweet potato freeze-dried powder to make an angel cake, which can identify the aroma of purple jade. The second stage is the purple sweet potato powder substitute of 20%, 30%, 40%, 50%, 60%, 70%, 80% of cake flour to produce an angel cake. The result shows when the addition of the purple sweet potato powder is increased and the viscosity is increased but the height is decreased. The production of an angel cake is no significant difference between the control group and the purple sweet potato flour instead of 20%、30% of cake flour. The color of cake change that shows the substitute of the purple sweet potato powder is increased, the color of cake with mush become deeper. Physical analysis shows the substitute of the purple sweet potato is increased, the cohesion, flexibility, plastic viscosity, adhesion is reduced and the hardness and chewiness is increased. The third stage is exploring the color change for adding different amounts of the tartar, tartaric acid powder, baking soda and alkaline water into the process of purple sweet potato for an angel cake to adjust the pH of the paste. The different pH value change which shows the effective of the color analysis, sensory evaluation, texture analysis and storage test. The result shows when the batter is alkaline, the color of an angel cake is distinctly green; when the batter is acidic, the color of an angel is pink.
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