| Summary: | 碩士 === 國立中興大學 === 食品暨應用生物科技學系所 === 97 === Abstract
Tea is the most general and popular healthy drink in recent years. As
changing of the social environment, consumer drinking habits of tea have
been changed from the traditional way in the past with a hot pot of tea to a
modern style with cold bottle ones. Thus, how to make a tasty and
delectable bottle tea drink has become one of the most important issues
among all drinking venders.
The objective of this research is to understand the effect of extraction
conditions on the physicochemical properties of bottled tea drinks. By
taking Yushan oolong tea as the experiment material, the following
extraction conditions were investigated:
1. pH value of water: 5, 7 and 9.
2. Temperature of water: 50°C, 70°C and 90°C.
3. Extraction duration: 5 minutes, 10 minutes and 20 minutes.
The physicochemical of various tea extracts were analyzed by different
physical and chemical analysis. In addition, both descriptive and consumer
sensory evaluation were investigated as well for selecting suitable control
factors and conditions for future tea drinks product research and
development. The result shows the brix, total polyphenol, caffeine,
catechins in Yushan oolong tea generally increased by increasing the
extraction temperature , and extraction duration, but decreased by
increasing pH value. Sensory evaluation results showed that Yushan
oolong tea will have a better aroma, taste and overall acceptance to
customers under a lower pH value (pH5) extraction. Furthermore the color
of tea infusions is bright and lighter. In contrast, the overall acceptance of
tea infusions is worse under a higher pH value (pH9) extraction. In addition,
the color of tea infusions is darker, redder with higher extent of browning
accompanied with higher total flavonoids . The pH value of water also
showed a pronounced influence on the compositions of catechins and
aroma compounds of Yushan oolong tea.
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