Lecture 8 Flashcards
Where does tea come from?
All tea comes from the plant camellia sinensis its soley the processing that is different.
Who produces the most tea and what is the value of tea?
China is the leading one but India and Sri Lanka produce a signifincant amount, about 9.5 billion USD and is increasing in how much is produced.
HOw much tea is consumed by the world?
3 billion cups per day as it is the second most popular beverage on average in the world
Briefly discuss the history of tea.
first cultivated in China and orginally consumed as food. The emergance of match created a distinct culture, it would be broken down or pressed into cakes and hot water was added. The conversion of tea from china to japan led to loose leaf tea and the dutch brought it towards britian.
What are the 4 types of tea based on processing and briefly describe them.
- White tea: least proccesed, which comes from leaves harvested before the buds open, have a sweet, grassy aroma and fruit qualities
- green tea: more processed, coming from leaves that are dried as soon as they are harvested to minimize oxidation, keep them fresh and the polyphenols, creating a grassy and vegtable quality
- Oolong tea: comes from leaves that are gently rolled after harvest to achieve slow oxidation, darkening the tea and adding more layers of complexity, has array aromos of liliac to orange, sweet to dark and nutty to full
- black tea: highly processed tea that have a dark color resulting from complete oxidation and have a more defined flavour from the compounds released during processing
Ther are 5 catechins which are the major flavonoids in the tea plant, what are they?
- catechin (c)
- epicatechin (EC)
- epigallocatechin (EGC)
- epicatchin Gallate (ECG)
- Epigallocatechin Gallate (EGCG)-most common in green tea and is the plants defense mechainsm acting as an antioxidant
Outline the general steps of tea manufactoring for the 4 types of tea.
- white tea: tea leaves—>dryed—>product
- Black tea: tea leaves—>withering—>rolling—>fermentation aeration—>drying—>product
- oolong: same as black
- green:
- tea leaves—>steamed—>rolled—>dryed—>product
- tea leaves—>pan fried—>rolled—>dryed—>product
What are the major polyphenols in black tea?
- catechin (end up converting to theaflavins through oxygen and produce co2)
- epicatechin
- epigallocatechin
- epicatcehcine gallate
- epigallocatechine gallate
- gallic acid
- caffeoylquinic acid
- theaflavins
In depth describe the process of black tea production:
- withering
- rolling
- fermination
- drying
- storage
- process conducted in light or shade which affects the outcome but the following is what occurs: loose of 50% of moisture, packaging flavour precoursers and results in the release of enzymes due to partial hydrolysis of cell wall
- through manual or mechincal methods the cell wall is further ruptured so there is contact with the air, essential for fermintation, and speeds up reaction
- the enzymatic oxidation of polyphenolics by PPO and perzodiase which forms aroma and color compounds and converts astringent compounds to non and therefore decreases astringency without decreasing bitterness
- to reduce humidty and stabilize parts of tea for longer storage
- storage is important in perventing microbial activity so stored in an airtigh, lightproof container that is away from odors and moisture
In depth describe the steps of green tea production:
- steaming
- rolling
- drying
- treated with heat @ around 100 degrees for 30-45 seconds which deactives the enzymes in plant cells, eliminating the fermintation stage
- rolling: for similar purposes of black tea
- hardly affects polyphenol composition, aroma or taste since the enzymes are deactivated and fermintation didnt occur
What does the taste of tea depend on?
- chemical composition of dry leaves used in production
- physical condition of tea leaves
- processing conditions
- process of perparing tea
How does the perpation of tea work and what is it affected by?
through hot water infusion the extraction of phenolic compounds results within aorund 3 minutes and is affected by particle size, tea/water ratio,brewing time and temp
What are the extracts after 2 minutes of inufsion,..after 3?
after 2 less than have the catechins and more than 70% of the glycosylated flavonoids and more than 90% of the caffine but after three all are extracted
What are other tea products and describe them?
- decaf teas: removal of theine through extracting it with moistned tea leaves and organic solvents or CO2 technique, can affect taste and aorma properties
- instant tea: extracted tea on an industrial scale through evaporation of solvents and drying to recover a highly water soluble extract powder and coating them so they are soluble
What are the health effects of the compound EGCG in tea?
- anti cancer, cardiovascular, allergic,obese,diabetic,oxidant
- gut health
- neuroprotection
