Green tea processing

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  1. GREEN TEA PROCESSING USING INFRARED AND MICROWAVE HEATING 2. TEA OVERVIEW Tea is globally one of the most popular and cheapest beverages with major production…
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  • 1. GREEN TEA PROCESSING USING INFRARED AND MICROWAVE HEATING
  • 2. TEA OVERVIEW Tea is globally one of the most popular and cheapest beverages with major production centres in India, China, Kenya, Sri lanka, Turkey & Vietnam. The tea industry is one of the oldest organized industries in india with a large network of tea producers, retailers, distributors, auctioneers, exporters and packers. On an average, during the last two decade in the production front, India contributed 28% of the world tea production closely followed by china (25%), Sri lanka (9%) – being green tea producer and Kenya (9%) – ctc producer. 23 % world tea is produced by other countries. The global productivity during 1991 was 1026 kg/ha which climbed to mere 1100 kg /ha in 2000. In the first decade of 21st century, global tea productivity hovered between 1100-1160 kg/ha. SOURCE: ONICRA (onicra credit rating agency of India)
  • 3. TEA OVERVIEW On an average during the last two decade, in the export front, both kenya and sri lanka lead the world each with 20% of their contribution followed by china (17%), india (14%) and others (25%). Currently, india produces 23% of total world production and consumes about 21% of total world consumption of tea – nearly 80% of the tea produced is consumed within india. SOURCE: Basu Majumder A., Bera B. and Rajan, A. 2010. Tea Statistics: Global Scenario.
  • 4. TEA OVERVIEW Green tea • Green tea, known as unfermented tea, is a popular beverage in the world. • The more important of green tea is the flavor and smell. • Chlorophyll content of green tea is around 1.2-1.5 mg/gm of tea leaves. • Green tea is also recognized as herbal medicine. • Green tea is reputed to be benefit in some areas like cancer, infection, high cholesterol and impaired immune function.
  • 5. CHEMISTRTY OF GREEN TEA Contents % Dry weight Proteins 15-20 Amino acids 1-4 Fiber 26 Carbohydrates 7 Lipids 7 Pigments 2 Minerals 5 Phenolic Compounds 30 Oxidized Phenolic Compounds 0
  • 6. CHLOROPHYLL CONTENT of some leaves SAMPLE CHLOROPHYLL (a) mg / gm of leaves CHLOROPHYLL (b) mg / gm of leaves TOTAL CHLOROPHYLL mg / gm of leaves Tulsi leaves 1.6486 1.0466 2.7348 Henna (mehndi) leaves _ _ 2.7812 Mint leaves 4.0965 2.0788 6.1743 Curry leaves 5.4534 3.6581 9.1090 Neem leaves 6.0157 5.0268 11.0692 Vasaca leaves 11.86 12.51 20.50
  • 7. PROCESSING OF GREEN TEA Plucking(harvesting) Enzyme de-activation /fermentation stopping (by steaming or hot water pouring) Fixation Rolling Drying  High temperature drying  Low temperature drying (may include flavouring)
  • 8. PROCESSING OF GREEN TEA Classification(grading) Final roasting Packaging and labeling Metal detection Storage / dispatch
  • 9. GREEN TEA PROCESSING STEPS Plucking :  This is the process of harvesting green tea leaves from the tea plants.  Young and tender material is collected for a high quality green tea.  It is devided into three groups as : o Imperial > bud+ 1 leaf oFine > bud + two leaves o Course > bud + 3 or more leaves COURSE PLUCK FINE PLUCK IMPERIAL PLUCK
  • 10. GREEN TEA PROCESSING STEPS De-enzyming / ezyme de-activation >> The goal is to heat the tea to stop fermentation. If the fermentation is not completely stopped, the tea liquor will be red.  In this process of enzyme de-activation , the tea leaves are steamed so that enzymatic degradation will be stopped.  In some countries the boiling water is also used for de-enzyming.
  • 11. GREEN TEA PROCESSING STEPS FIXATION>> Important step in green tea primary processing, critical to obtain high quality. In this way, enzymatic oxidation of tea polyphenols is prevented as well as unnecessary changes of leave inclusions. While fixing tea leaves will soften for a good rolling, while the moisture content is reduced and the fragrance fixed. After fixation, the leaves should be spread in thin layers on clean spaces for natural or forced cooling.
  • 12. GREEN TEA PROCESSING STEPS FIXATION PROCESS>>
  • 13. GREEN TEA PROCESSING STEPS ROLLING>> Rolling is a crucial step for shaping the appearance. It is often carried out in a rolling machine. The tea leave quantity, time and pressure, are major technical factors during rolling. Tea leaves should look brightly green instead of yellowish and they should smell fragrant instead of stuffy.
  • 14. GREEN TEA PROCESSING STEPS ROLLING MACHINES / EQUIPMENT>>
  • 15. GREEN TEA PROCESSING STEPS  DRYING OF GREEN TEA>>> Traditional drying Conventional drying Microwave drying Infrared drying Hybrid drying processes
  • 16. DRYING OF GREEN TEA TRADITIONAL DRYING o SUN DRYING This is the same thing that most civilizations have done with their food since before written history: laying down the produce to dry under the sun for preserving to use later. Tea was not any exception. Since prehistory, the chinese has had an especially strong heritage of the use of dried plant materials and tea began as one of the medicinal herbs. o Moisture is reduced upto 4-6 %.
  • 17. DRYING OF GREEN TEA oSHADE DRYING: In this method of drying the green tea leaves are kept away from direct contact of sun to avoid loss of overall quality by providing required amount of heat from sun.
  • 18. DRYING OF GREEN TEA oCONDUCTION DRYING>>  In this type of drying the tea leaves are dried by directly roasting on the heated metal of non-metal surface.  The parameters which controls the drying phenomena are temperature,time&amount of green tea leaves to dried.  The final quality of green tea obtained by this drying method has darker color and low sensory attributes.  This is heating of green tea leaves on the metal plate above fire.
  • 19. DRYING OF GREEN TEA Rotatory drum dryers are one of the dryers which are used in tea drying for small scale production of green tea. Controlling parameters for drum dryers are drum rotation speed,drum internal temperature&processing time. ROTATING HANDLE FUELS HOT AIR OUTLETSGROES FOR MIXING TEA LEAVES
  • 20. DRYING OF GREEN TEA CONVECTIONAL DRYING METHODS>> CONVENTIONAL AIR DRYER:  In this method of drying the green tea leaves are dried by using heated air with different arrangements of drying sections.  This includes cross flow, concurrent,cocurrent,circulatory and forced circulatory etc. Types of dryer mechanisms.  The controlling parameters in this type of drying are air inlet and exhaust temperature ,drying time, feed rate .  The quality obtained by this method was bit improved from conduction type of drying.
  • 21. DRYING OF GREEN TREE LEAVES FLUIDIZED BED DRYER FOR DRYING OF GREEN TEA LEAVES>> WHAT IS FLUIDIZATION??  When air is passed through the bed of granular particles of suitable size, shape and specific weight under suitably controlled conditions the particles can be made to float in the air stream to behave like a fluid, under these conditions it is said to be fluidized and this phenomena is known as fluidization. In fluidized bed dryers the solids make direct contact with air resulting in higher rate of drying. The improved thermal contact between tea particles and air resulted in uniform drying of each particles with higher efficiency and with lower cost. This leads to a better quality of dried green tea leaves. The process controlling parameters are minimum fluidization velocity, particle shape size, specific gravity, air temperature and retention time. In fluidized bed dryer the tea leaves can be fed at feed end and discharged at the dryer end. Till now there are several fluidized bed drying methods have been investigated and designed like the Sri lanka tri-ccc fluid-bed tea drier etc. .
  • 22. DRYING OF GREEN TREE LEAVES FLUIDIZED BED DRYER
  • 23. MICROWAVE DRYING OF GREEN TEA Microwave drying (MD) is a relatively new drying method. The fundamental mechanism of microwave heating is the agitation of polar molecules which oscillate under the influence of an oscillating electric and magnetic field. In the existence of an oscillating field, particles always try to orient themselves with the field. The activity of particles is restricted by resisting forces (for example electric resistance or interaction), which restrict the activity of particles and generate random movement, thus producing heat. The key advantage of the microwave heating over conventional heating method is the nature of fast internal heating by microwave energy.
  • 24. MICROWAVE DRYING OF GREEN TEA Microwave energy deposition in the dielectric loss mode of heating can cause spatially uniform heating. When applying microwave energy to tea, water and other polar molecules of tea are induced for simultaneous high-speed rotation due to microwave irradiation, leading to the surface and interior heating at the same time, and resulting in a large number of water molecules escaped from the tea (Lou, 2002). However crumple zone may be produced to affect the quality of tea due to high heating rate (Cai, 2005).
  • 25. MICROWAVE DRYING OF GREEN TEA LEAVES>> oGreen tea manufacture was standardized with respect to the inactivation of polyphenol oxidase (PPO), rolling, and drying for quality manufacture. Inactivation of PPO by parching, steaming, microwave heating, and oven heating was monitored in tea shoots. oFresh shoots of tea are very rich in polyphenols, especially the flavan-3-ol group (catechin and its derivatives), which are present at up to 30% on a dry weight basis.In processing younger tea shoots for green tea manufacture, polyphenol oxidase (PPO) inactivation is necessary to avoid the oxidation of catechins to form theaflavins and thearubigins. These catechins are responsible for the astringency and taste of green teas. oIn steam-inactivated and oven/microwave-dried teas, total phenol and catechin contents were intermediate between parched and sun-dried teas and microwave- inactivated and microwave-dried teas, and their infusions were bright with a umami taste.
  • 26. MICROWAVE DRYING OF GREEN TEA LEAVES Microwave energy is transported as an electromagnetic wave in certain frequency bands in the range between about 0.3 GHz and 300 GHz. When microwaves impinge on a dielectric material, part of the energy is transmitted, part reflected and part absorbed by the material where it is dissipated as heat. . Heating is due to `molecular friction' of permanent dipoles within the material as they try to reorient themselves with the oscillating (electrical) field of the incident wave. MICROWAVE HAS ANunique characteristics, which include the facts that no contact is required between the energy source and the target and that heating is volumetric, rapid and highly specific in nature.
  • 27. MICROWAVE DRYING OF GREEN TEA The major food components - water, carbohydrates, lipids, proteins and salts (minerals) - interact differently with MW. MW interactions with foods depend heavily on salt and moisture content. Water selectively absorbs the energy. In drier products, the dissolved salts are concentrated (in the remaining water); if the solids exceed saturation level and precipitate, their ionic conductivities are limited. However, the solids themselves do absorb energy.
  • 28. MICROWAVE DRYING OF GREEN TEA LEAVES
  • 29. DRYING OF GREEN TEA LEAVES INFRARED DRYING OF GREEN TEA LEAVES>> WHY INFRARED HEATING OF GREEN TEA LEAVES>  Infrared radiant heat transfer is often more efficient than convective heat transfer.  Large amount of controlled heat for heating tea leaves.  Uniform heating of the green tea leaves.  15-20 minutes to reduce mc upto 2% (if layer thickness is around 5- 10cm).  It takes about 1 minute in heating at 60 degree centigrate.
  • 30. IR DRYING OF GREEN TEA LEAVES TYPES OF INFRARED RADIATION: o NEAR INFRARED:: 0.75-1.4 micro meter :: 214-400THz:: 886-1653 meV o SHORT WAVELENGTH IR:: 1.4-3 micro meter::100-214THz::413-886meV o MID WAVE INFRARED:: 3-8 micro meter::37-100THz::155-413meV o LONG WAVE INFRARED:: 8-15 micro meter::20-37THz::83-155meV o FAR WAVE INFRARED(FIR):: 15-1000 micro meter:: 0.3-20THz :: 1.2-83meV
  • 31. ADVANTAGES OF IR HEATING OF GREEN TEA LEAVES • REDUCTION IN DRYING TIME. • FAST RESPONSE TIMES ALLOW EASY AND RAPID PROCESS CONTROL. • NO DIRECT CONTACT WITH MATERIAL IS REQUIRED AS IN CONDUCTION DRYING. • BETTER COLOR AND FLAVOUR RETENTION THAN CONVENTIONAL DRYING. • POSSIBILITY OF SELECTIVE HEATING
  • 32. INFRARED GREEN TEA DRYING INFRARED CATALYTIC GAS BURNER
  • 33. COMPARISSION OF DIFFERENT DRYING TECHNOLOGIES ON THE FINAL QUALITY OF GREEN TEA EFFECT ON REHYDRATION RATIO: 2.54 2.8 2.88 3.07 0 0.5 1 1.5 2 2.5 3 3.5 AD VD MD MVD rehydrationratio different drying methods Rehydration ratio (g.(g)^-1) Vs different drying methods
  • 34.  COMPARISSION OF DRYING RATE
  • 35. COMPARISION OF NUTRITIONAL COMPONENTS DRYING METODS POLYPHENOLS AMINO ACIDS WATER SOLUBLE SUGAR PROTIEN CAFFINE AD 24.92 3.17 3.19 1.80 4.25 VD 24.34 3.43 4.07 1.95 4.43 MD 21.58 3.60 2.72 2.08 4.48 MVD 22.0 3.76 2.84 2.54 4.66
  • 36. COMPARISSION OF PHENOL-AMINO ACID RATIO 7.87 7.09 6 5.86 0 1 2 3 4 5 6 7 8 9 AD VD MD MVD Phenoltoaminoacidratio Different drying methods phenol to amino acid ratio Vs different drying method
  • 37. COMPARISSION OF SENSORY ATTRIBUTES DRYING TECHNIQUE SENSORY SCORE (OUT OF 100 ) AD 87.70 VD 89.55 MD 90.97 MVD 93.15
  • 38. ADVANTAGES OF MODERN DRYING TECHNOLOGIES 1. The MVD drying technology is best in case of overall quality of green tea. 2. In some cases the microwave drying is better than conventional air drying. 3. But VD is also better than microwave in case of amino acid retention. 4. The MD&MVD are very fast drying techniques. 5. Better cell structure was maintained by MD with/without vacuum .
  • 39. DISADVANTAGES>> 1. Very huge capital investment. 2. High operating cost. 3. Problem of leakage with MD & MVD.
  • 40. REFERENCES 1. Cai, Y. 2005. Progress in the drying technology of tea. Fujian Tea, (3): 22–23. 2. Lou, L. 2002. Applications of microwave technology in the tea processing. Fujian Tea, (1): 23–25. 3. Xiao, H. 2006. The equipment development trend of mechanized green tea processing. China Tea, (3): 40–41. 4. Lee, S. C.; Kim, J. H.; Jeong, S. M.; Kim, D. R.; Ha, J. U.; Nam, K. C.; Ahn, D. U. Effect of far-infrared radiation on the antioxidant activity of rice hulls. J. Agric. Food Chem. 2003, 51, 4400-4403. 5. Gulati, A.; Rawat, R.; Singh, B.; Ravindranath, S. D. Applicationof microwave energy in the manufacture of enhanced-quality green tea. J. Agric. Food Chem. 2003, 51, 4764-4768. 6. LEE, S.C., KIM, S.Y., JEONG, S.M. and PARK, J.H. 2006. Effect of Far- infrared irradiation on catechins and nitrite scavenging activity of green tea. J. Agric. Food. Chem. 54, 399–403.
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