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TEA FERMENTATION

TEA FERMENTATION. tea manufacture is one of the oldest biotechnologies developed and practiced by mankind. Turkey : 160,000 ton black tea production and consumption. China Teas ( Camellia sinensis var. sinensis ) - slow-growing ( grow to a height of 4–6 m if unattended)

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TEA FERMENTATION

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  1. TEA FERMENTATION

  2. tea manufacture is one of the oldest biotechnologies developed and practiced by mankind. Turkey : 160,000 ton black tea production and consumption

  3. China Teas (Camellia sinensis var. sinensis) -slow-growing ( grow to a height of 4–6 m if unattended) - resistant to cold - in China, Japan,Turkey, Iran -to produce delicately flavored tea -low-yield Assam Teas (Camellia sinensis var. assamica) -faster-growing (12–15 m ) -larger glossy elliptical leaves -less resistant to cold -much higher-yield -less delicately flavored

  4. Types of tea green tea ( not fermented ) oolong and pouching teas ( partially fermented) black tea ( fully fermented) Differences=f(extent of fermentation) most tender portions of tea plants are used to produce best quality teas. Immature plant:less woody (i.e. Less lignified)

  5. Fresh tea shoot tips ( 78 % moisture) Constituent % of total dry weight -------------- -------------------- protein 15 ( including catechol oxidase) fiber 26 pigments 2 ( chlorophyll, caretones ) lipids 7 caffeine 4 polyphenols 30 ( mostly catechins ) amino acids 4 minerals 5 carbohydrate 7 volatile compounds 0.1

  6. approx. 32 % of its ingredients pass into the infusion. Tea contains: Caffeine (teine) / Tannins / Amino acids / Proteins Trace elements and minerals: fluoride, potassium, calcium, manganese / Vitamins: niacin, vitamin B1 and B2

  7. BLACK TEA MANUFACTURE WITHERING ( soldurma ) Shoot tips are picked by hand( plucking)( 78 % moisture)Withering 55 % Moisture permeability of plant cell membranes changes. ( air temp < 32 C, otherwise leafs break and burns) Batch system , Continuous system

  8. TISSUE MACERATION (ROLLING)(kıvırma )(breaking, squizing, bending). ruptures the leaf cell structure, exposing the polyphenols, oxidative and degradative enzymes, lipids, amino acids, etc., to oxygen. catechins come into contact with the polyphenol oxidase enzyme, initiating ‘tea oxidation,’ which is erroneously referred to as ‘fermentation.’

  9. MACERATION

  10. FERMENTATION (1.5 to 3 hours, RH: 90-95 % , 24-26 C, tunnel-continuous system) oxidation of tea catechins mediated by the tea catechol oxidase enzyme and all the secondary reactions associated with this primary oxidation. All the reactants except oxygen are endogenous to the tissues of the tea shoot tips.. the primary reactants ( i.e. the catechin in vacuoles of tanniferous cells, and the catechol oxidase enzyme within the cytoplasm) remain spatially separated until tissue maceration step.

  11. Withering destroys the semi permeable properties of the cellular membranes allowing the cell contents to become mixed under the action of tissue maceration process tea fermentation begins. Tea catechin orthoquinonestheaflavins (bright oxidized may condensered color with oneanotherfair solubility acts as oxidizing agent to oxidize others) gallic acid epithea flavic acid (Bright red oxidized condensedexcellent solubility) with oxidized catechin

  12. characteristic aroma of black tea is formed during fermentation. at ambient temp and the process takes from one to five hours to complete. During this time the tea plant material changes color from green to coppery red , and the aroma changes from grassy to sweet and flavory.

  13. Firing (Drying) to terminate fermentation and to dry tea for storage and transport. the temperature rises, some reactions are accelerated until the rise is adequate to denature the enzymes

  14. the color changes as a result of the transformation of chlorophyls to pheophytins and pheophorbides. Some caffeine is lost while the amount of volatile flavor compounds is reduced. The volatile flavor compounds that result from various pyrolytic reactions are formed during firing

  15. GRADING and STORAGE Mechanical sieving -----smallest fraction ( best) ----coarse fraction Screen numbers 8-10-12-20-32 ( # of openings in one inch square) 1st grade : 20/30 (completely fermented, best quality) 2nd grade: 12/20 (very little unfermented tea ) referred as --imalat kırığı 3rd grade : 10/12 ( little unfermented tea)

  16. tea collected under 30 ( pan----referred as toz çay) tea collected 8/10 mechanically rebroken ----referred as kırık çay) this tea is sieved again to obtain : 4th grade : 20/30 5th grade: 12/20 6th grade 10/20 7th grade Dust ( pan portion )

  17. Volume of tea One of the important quality criteria for tea is its density. Usually volume ( cc) of 100 gram tea is measured. Small volume ( in turn higher density indicates higher quality) Tea from fresh ( young ) tea shoots : density is high Tea from old leafs : density is low ( Because its cellulose content is high)

  18. Standards related with quality of tea: Grades ------------------------------------------------------------------------------------------------ 1 2 3 4 5 6 7 -------------------------------------------------------------------------------------------------- stems % max 1 2 3 4 5 5 4 -------------------------------------------------------------------------------------------------- unfermented piece max 2 2 3 4 8 8 4 ---------------------------------------------------------------------------------------------------- volume cc/ 100gr 360 500 650 360 480 580 280 ------------------------------------------------------------------------------------------------ Moisture contents in excess of 6.5% are extremely detrimental as this encourages rapid fungal and bacterial growth Conversely, teas that come out of the drier with moisture contents of 2.5%, or less, generally have a ‘smoky’ taint, if firing has been carried out using a conventional dryer.

  19. quality based on tea shoots(sürgün): 1st tea shoots 2nd tea shoots 3rd tea shoots volume cc/100grams 1st grade 310 320 320 2nd grade 420 440 440 3rd grade 520 540 540 tea must not be stored close to a strong smell due to its remarkable ability to pick up odors.

  20. Green tea no oxidation, especially that of the catechins. starts with steaming or roasting to deactivate polyphenol oxidase activity. made from tea plant varieties with a lower catechin The volatile components of green tea are basically those of the primary products.

  21. Oolong tea

  22. Pouchong tea (30 % fermented ) process is slightly different than for oolong. The leaf is withered in the sun (solar withering) for 15 min followed by indoor withering for 3 h The leaf is then pan-fried Low-grade pouchong tea is often scented by blending with jasmine flowers to enhance the flavor (jasmine tea).

  23. Earl Grey tea named for Charles Grey, prime minister to King William IV in the early 19th century. Earl Grey gets its elusive flavor from oil of bergamot ( bergamot orange) A small tree (Citrus aurantium subsp. bergamia) commercially grown chiefly in southern Italy for its aromatic oil

  24. Instant tea Tea extracts may be concentrated and spray dried directly to produce products that require hot water for redissolving Cold water soluble instant tea products are manufactured by chilling the tea extract, separating the insoluble caffeine/tea polyphenol complex An alkaline-air mediated oxidation of tea polyphenols is the most commonly used process, enzymatic treatment using the enzyme tannase has been also used.( for ice tea production)

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