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Enzymes to imporove colour in teas and coffees
Transcript of Enzymes to imporove colour in teas and coffees
teas and coffees Daniela Rendon We have all seen enzymatic browning but may not have know biologically what it was called or what was occurring
Enzymatic browning is what causes both fruits and vegetables to turn a brown colour when ripening or cut.
To understand how these enzymes affect the colour of tea and coffee it is important to
first understand this process. Enzymatic Browning as soon as tea leaves are picked, if they are left without drying the polyphenol oxidase will begin to act and oxidize the leaf, naturally turning it brown
the color of the tea can be manipulated by controlling how much oxidation occurs in the leaf, by doing this not only is colour affected but so is taste Enzyme Browning in Tea enzymatic browning in coffee occurs with the Maillard Reaction
this reaction occurs during the roasting process. It is responsible for the flavor, aroma and colour of the coffee.
the last step of this reaction releases the polyphenol oxidase enzyme and creates the long brown polymer chains.
This is responsible for the colour of coffee Enzymatic Browning in Coffee enzymatic browning is an oxidation reaction, oxygen must be present for it to occur
the plant cells in a fruit or vegetable are ruptured by cutting through the cellulose tissue
the enzyme POLYPHENOL OXIDASE is released and creates natural phenols (catalyzes polyphenol its substrate and molecular oxygen as a co-substrate)
these turn the tissue into a long-chain of brown-colored polymer compounds How does enzymatic browning occur? The brown polymer produced during the enzymatic browning was found to be very toxic to bacteria
It is how the plant protects itself from any bacterial infections while it is ripening and is more vulnerable Why does this occur? apple before enzymatic browning after enzymatic browning examples many food companies try to stop enzymatic browning because it is seen as detrimental to the fruit or vegetables and to sales It is only seen as beneficial to a couple foods, these include coffee and tea. No oxidation occurs
As soon as the leaves are picked they are steamed or heated, by doing this it prevents the process of enzymatic browning from occurring Green Tea Partial oxidation occurs between 10%-80%
As leaves are rolled and crushed they are exposed to oxygen, and the polyphenol oxidase is allowed to act in controlled rates
It is one of the most expensive teas because it is the hardest to make, requires years of experience
results in varies shades of brown Oolong Tea the leaves for black tea are left to be completely oxidized
the polyphenol oxidase catalyzes the polyphenol substrates and oxygen co-substrates throughout the entire leaf Black Tea References Gizmodo (2010, Sept 23). Retrieved October 5, 2012,
from http://gizmodo.com/5645374/what-is-tea Rivera, Joseph (2008, April). Under the Microscope: Browning Reactions.
Retrieved October 5, 2012, from
_MarApr08_ScienceofBrowning.pdf Lincat (2008, July 14) . Retrieved October
5, 2012, from http://www.lincat.co.uk/uploads/files/
guide-to-world-teas.pdf What is Tea A Guide to World Teas Roast Magazine (Lincat, 2008) (Rivera, 2008) Lincat, 2008) (Lincat,2008) Lincat, 2008) (Gizmodo, 2010) Lincat, 2008) Lincat, 2008) Rivera, 2008)