We are gratefull to Ranga Bedi for his input analysis of equipment to manufacture Tea and hopefully this will start some interesting discussions on the subject. Please send you comments to the Editor at [email protected]
SOME THOUGHTS ON TEA MANUFACTURE IN THE
TWENTY FIRST CENTURY
there are three parts to go to
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One, Two
Three
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One
LEAF PROCESSING : Case history
From the last quarter of the 19th century when commercial tea manufacture began, to mid 1930’s, the Orthodox Roller was the only machine known to the industry. These R ollers varied in hood size from 30’’ (66 cm ) to 48’’ (105 cm ). The action of the orthodox Roller was to twist withered leaf in the same way as you would roll a cotton wick between the palms of your hands. Minimum leaf breakage and a tight twist were criteria for good rolling. Three to five rolls with a sift between each roll was the norm. Apart from aerating rolled leaf, the purpose of the sift was to separate leaf that had been adequately rolled.
Productivity :
On a three roll system the rolling time would be from 90 minutes to 120 minutes ( 30 / 40 minutes each ). With a Roller charge of around 275 kilograms. Process output of 180 / 200 kgs per hour. Connected H.P. 50, output 4 kgs rolled leaf per H.P. / hour.
SIXTY YEARS LATER : Advent of C.T.C
Sixty years after existence of rollers the C.T.C machine was introduced in the mid thirties.
ROLL / CTC
This process involved a conditioning 30 minutes roll followed by three C.T.C cuts (2 cuts in some cases). The 48’’ C.T.C machine had a throughput of around 900 kgs rolled leaf per hour. Each line required 2 x 36’’ orthodox rollers for conditioning.
Productivity :
Rollers : 30 H.P, C.T.C’s : 85 H.P total 115 H.P.
This system gave an output of 7.5 kgs per H.P./hour.
C.T.C manufacture was a revolutionary concept in tea production. Cutting, Tearing and Curling was sacrosanct while crushing was blasphemy.
C.T.C tea was not only different in size and appearence, it had totally different cup characteristics. This form of manufacture had all the liquoring attributes minus aroma. Lets bear in mind that aroma was the most important component of liquor at that point of time. It was not conceivable that tea would be saleable minus its aromatic character. Yet the additional cuppage that C.T.C tea offered could not be ignored . In a nutshell, C.T.C manufacture took off.
25 YEARS AFTER C.T.C
Advent of the Rotorvane :
The early sixties witnessed introduction of the Rotorvane as a pre – conditioner to replace Orthodox Rollers that were a batch process. To achieve preconditioning objectives the Rotorvane crushed the hell out of withered shoots. The Rotorvane proved that there was nothing blasphemous about crushing. If anything liquor, sizing and appearance were better. The fact that Rotorvane/ C.T.C became a continuous process was a bonus.
The sixties also saw introduction of L.T.P’s and other substitutes for C.T.C’s, these did not make a dent in popularity of the C.T.C process. C.T.C’s were also introduced in sizes varying from 24’’ to 36’’. Quadrants were replaced by sliding block adjustments resulting in more precise cutting.
Productivity : Rotorvane 20 H.P 3 cut C.T.C 55 H.P total 75 H.P.
Output : 10.5 kg per H.P / hour.
20 YEARS AFTER ROTORVANE
The tea industry witnessed introduction of FLUIDISED BED DRIERS in the EIGHTIES. These high output machines cut drying cost by half, gained rapid popularity and hailed the SECOND REVOLUTION after the
C.T.C. with due respect, the Rotorvane did not produce an end product, was designed as an aid to productivity, it therefore does not qualify to be revolutionary. An applaudible new concept.
The last ten years have seen a lot of fermenting machines make an appearance. Most of these would not stand up to scientific scrutiny. The industry is so desperate to automate that anything warrants a try.
In brief the Industry’s track record over 125 year period reads as follows :
Late 1800’s Orthodox Roller mechanised Tea processing.
1930’S C.T.C machine invented.
1960’S Rotorvane and trough withering.
1980’S Fluidised Bed drying.
In 1998 we are still using the Rollers from 1875 and C.T.C machines from 1935. Changes if any, can only qualify the saying “Old Salads in new dressings”. Leaf processing hasn’t seen a new concept.A dismal track record by any standards. My apologies, we did get an Infra Red moisture meter in the 50’s.
IS ANYONE WORKING ON NEW CONCEPTS
IN TEA MANUFACTURE ?
LEAF PROCESSING (C.T.C) :
The most widely practiced forms are Rotorvane/C.T.C or L.T.P manufacture.
The function of these machines is to cause cell rupture and size withered leaf. This objective has been successfully achieved by using a Rotorvane and three C.T.C machines in tandem. Four and Five cuts are also used. However , let a 30 inch Triplex be the standard.
A Rotorvane is made of gun metal or stainless steel, the C.T.C’s use stainless steel, cast iron, alloy steels (gear boxes), copper/brass (motors) and mild steel. The 15 inch Rotorvane weighs 2,000 kg and a 30 inch Triplex weighs 8,000 kg (including conveyors).
This gives us a Rotorvane/C.T.C line up weighing 10,000 kg (10 tonnes) using all descriptions of expensive steel. After one hour of consistent and supervised operation, we process 700 kg (North East India) shoots per hour or 12 kg withered leaf per minute - 10 tones of precious steel to cause cell damage and size 12 kg of succulent shoots. Enough connected horse power to get a bi–plane airborne!
Recent trials have established that a Rotorvane / Triplex C.T.C combination, if the C.T.C ROLLERS ARE SHARP AND PERFECTLY MESHED, ruptures no more than 70% of the cells. If these findings are anything to go by,10 tonnes of steel processes 12 kg of shoots per minute and exploits only 70% of liquor potential.
A NEW CONCEPT :
CELL RUPTURE AND SIZING MUST BE VIEWED AS TWO DISTINCTLY SEPERATE OPERATIONS.
Bedi & Bedi, Bangalore, set about this task in 1991 and made some startling findings. The first experiments were carried out with ultra sound, which achieved 98% cell rupture. This line of experimentation was given up as air is not a conducive medium for the conveyance of ultra sound. Experiments were conducted by submerging withered leaf in water. This was not a practical option and was abandoned.
The next line of approach was to freeze withered leaf at temperatures substantially below freezing point. Thawed shoots recorded cell rupture exceeding 95%. The percentage difference of cell rupture in leaf and stem was insignificant. Having achieved 95% cell rupture in the shoot (in its whole form), only a sizing operation was required.
B&B trials involved conveying withered leaf through a freezing chamber to freeze the shoots. Freezing time will vary according to refrigeration equipment installed. This can be from two to six hours. Shorter the period higher the capital and operational cost. Withered leaf comes out in the form of frozen whole shoots. These are thawed and surface moisture removed in perforated high speed spinners. These shoots, with 95% cell rupture, are fed into a sizing machine. Various types of sizing machines are available that will size the leaf according to the setting. The sizing process is 80% efficient. If you wish to make 80% brokens, Fannings or Pekoe Dust the setting will do it. In other words you can dictate grade percentages without worrying about liquors.
BENEFITS :
Exploiting 95% of leaf liquor potential.
Heating of leaf in C.T.C cutting process or L.T.P’s eliminated. After freezing there is no latent heat in the leaf. Sizing machines have a clean cut action, there is no hammering or crushing / squeezing of leaf.
Due to even particle size Fermentation and Drying are even. Sorting is virtually eliminated, grades are totally even in density.
Lack of handling in the sorting room preserves liquor characteristics.
IF CIGARETTE TOBACCO CAN BE SIZED THE WAY IT IS, SHOOTS CAN ALSO BE CONVERTED TO A GRADE OF YOUR CHOICE.
You will miss the fibre and tea waste! Precision sizing machines do not pulverize and skin the stem like Rotorvanes, C.T.C’S and L.T.P’S.
A FEW LIKELY POSERS
- What is the tea like? It gives substantially higher cuppage per kg. How can it be
different? 95% of the cells have been exploited instead of 70%. The bio–chemical composition of the leaf has not been altered in any way.
- What will the market reaction be? Leaf appearance and make will depend on the
type of sizing equipment used. In any case, did C.T.C look like Orthodox? With the additional cuppage per kg, the buyer/blender should pay a premium for it.
Ranga Bedi
Bedi & Bedi Pvt Ltd
Bangalore, India
PATENT HOLDERS May 1985 Return to Top
-TWO
TEA MANUFACTURE
At the expense of repeating myself I would like say that as far as development of Tea PrReturn to mTopocessing machinery is concerned. Industry and Government funded Tea Research establishments have concentrated on the field while corporate R&D work has remained in house in terms of achievement and application. Tea Machinery manufactures have made little or no contribution. In India our slogan since the seventies has been “1000 million kgs of Tea by 2000 AD”. In 1998 we may hit the 800 million mark if AL NINO does not focus on us. It was amusing to be told at a seminar, that 1000 million was still achievable if the Industry had the will and took crash measures. This was in 1997, who else but a politician in power could make such a statement? A crop increase of 200 million kgs in 2 1/2 years. Where is the equipment to handle this volume ? Be it as it may, can Tea Manufacture continue in its archaic tracks? Who is going to bring about the Revolution?
SOME THOUGHTS ON TAKING TEA MANUFACTURE INTO
THE TWENTY FIRST CENTURY.
WITHERING
Trough Withering with minor variations is an accepted norm and universally adopted. This form was introduced in the early fifties, 50 years ago. Leaf is loaded into troughs to a depth of 20 cm (8”) and ambient / warm air applied to dehydrate the shoots. It has been scientifically established that, if liquor potential is to be adequately exploited, there must be an interval of at least 12/15 hours between a shoot being plucked and it being processed. Chemical withering is the term to define this interval. It has also been accepted that chemical wither occurs at a constant rate and cannot be accelarated by any form of physical or chemical intervention. As pre process moisture reduction ( physical wither ) is an equally important factor, this is obtained by applying ambient / hot air into troughs during the chemical wither retention period. In other words chemical and physical wither progress concurrently. In the present system it is the logical thing to do.
It is my belief that CHEMICAL and PHYSICAL withering cannot be treated as a single activity. These are two separate entities and must be treated as such. Chemical wither has a consistent rate while physical wither is totally variable. This apart, physical wither
carried out over 12/15 hours is uneconomical, uneven, detrimental to quality and above all totally dependent on the human factor of supervision.
ALTERNATIVE:
OBTAIN CHEMICAL WITHER FIRST:
Modify your existing trough side walls to accommodate a loading depth of 24”(52 cm). Load your trough to this depth and run your fan on ambient air for a period of 2/3 hours to expel all latent heat from the leaf bed. Choke fan intakes by 50% or more, hold leaf for desired period of chemical wither, 12 to 15 hours. Leaf is now in storage and no physical wither, whatsoever, will take place – THAT IS THE OBJECTIVE. In fact, every endeavor should be made to keep leaf as FRESH AS POSSIBLE.
THEN PHYSICAL WITHER
PICTURE
The two drums are fitted with precisely placed internal flights. Chemically withered leaf is fed into the first drum on a continuous basis in accordance with rated capacity of the drum. Hot air is induced co – currently. The internal flights, in the slowly roatating drum, cause the leaf to be gently lifted and showered REPEATEDLY from the internal apex of the drum into the path of the hot air in a thin curtain formation. The leaf exits from the first drum and is fed into a second drum where the process is once again repeated. The degree of WILT (physical) is controlled by varying time required to obtain withers of upto 65% is 1 hr 20 minutes.
In conventional troughs Hygromatric difference must not exceed 6/8 deg F. HD beyond this causes, leaf at the bed to crispen and condensation occurs in the leaf bed. However, in the drum HD upto 30/35 deg F can be applied. Shoots fall in a curtain formation and are not in contact with hot air constantly – hoots do not heat up as would be expected. Expelled Moisture on the shoot surface has a cooling action while being carried up by the flights on the drum walls.
Two drums have to be used. After a specific travel distance in the drum the hot air gets saturated with moisture. By transfering to the second drum leaf is once again subjected to hot air with a high hygromatric difference. Evaporative efficiency criteria dictate the use of two drums.
BENEFITS IN QUALITATIVE TERMS:
- In conventional troughs wither obtained is an average. A handful of shoots from
the bottom 2” of the leaf bed will have a different wither to similar samples drawn from the middle and top. Wither obtained is an average of these three samples. This is applicable to all troughs including enclosed and reversible. In the case of the drum each shoot is treated individually while it repeatedly falls in the path of the hot air. If a sample of shoots is drawn at any stage of the process all shoots will be identically wilted. Wither percentage of leaf can be dictated. This is not so in troughs, there is no control, what so ever, on shoot to shoot variation. In Drum wilting you can dictate the wither you want as 9
- air volume(cfm) inlet temperature
(H.D) and stay time (duration) are variable. These features are appreciated when handling rain soaked leaf with surface moisture.
- In the trough withering process bruised and damaged leaf oxidizes and changes
colour while physical wither is being obtained over a 12/15 hour period. This discoloured leaf goes through the manufacturing process, adds to quantity , but adultrates quality produced troughs, latent heat is expelled in the first 2/3 hours whereafter there is hardly any air passing through the leaf bed. Due to lack of Air/Oxygen no oxidization or discoloration takes place. Bruised and damaged shoots remain totally green. Wilting process in the drum takes a maximum of one hour 20 minutes – In this period hardly any bashing it gets, takes over an hour to ferment. The drum process gives a GREEN WITHER. There is no such thing as discoloured or damaged leaf.
In quality terms, a damaged / lacerated green withered shoot will contribute to liquor in the same measure as an undamaged shoot. Drum wilting gives an even and green wither to a dictated percentage. Once this degree of control is achieved at the withering stage, it goes without saying that, it will follow through in processing and show spectacular eveness in fermentation and drying. Are liquors and quality not assured?
- BENEFITS IN COMMERCIAL TERMS:
Calculations are based on a medium size existing factory with eighteen troughs (100’x5’ each – capacity 1600/1700 kgs Green leaf)
Out put 1200 kgs withered leaf per hour (by weight)
TROUGH DRUM SAVING
WITHERING WITHER
a) Trough space (including passages) 15000 sq.ft 6800 sq.ft 55%
(Troughs 6000 Sq.ft. including Passages + Wilter Layout 800 sq.ft )
b) Connected Electrical HP 135 HP 70 HP 49 % (2 Wilter 25 HP 6 Storage troughs 45 HP)
c) Power consumption *12/15 hrs Wilter continues till 48% minimum end of manufacture. 6 Trough fans at 3 Hours full load
d) Heat Source common to both Varies according to local practices
Labor saving to be quantified under local conditions.
‘A Trough fan is normally shut of when unloading takes place. Power savings shown under ( c) will be substantially greater as calculation is based on all trough fans being switched off after desired chemical wither is achieved (12/15 hrs)
OTHER BENEFITS:
Leaf handling is substantially reduced, apart from labor saving this labour saving this is desirable from liquor point of view.
Troughs are used on the principle of FIRST IN FIRST OUT – for this reason Chemical wither has a common time factor for leaf, harvested from seed plantation, clonal plantation, young or old Tea. The primary reason has been that facilities have never been available to differentiate between any type of green leaf. It is logical that we apply the same chemical wither criteria irrespective of leaf type? With drum wilting this is possible. Ideal chemical wither period for any type of leaf can be determined by a series of simple experiments. First in First out does not apply as leaf in all troughs is maintained in fresh condition. You can determine ideal chemical wither timing for clones, seed, young or old tea.
Substantial reduction in capital cost of withering facility in a new factory.
66% troughs in existing factories would become surplus to requirement even in peak cropping periods.
RANGA BEDI
Founder Director
BEDI & BEDI Pvt Ltd
BANGALORE, INDIA
August’1998 Return to Top ************************************************************************ Three
Calling 100!
Emergency In The Indian Tea Industry
Numerous Estates Locked out, closed, even abandoned, others squealing under mandatory default and debt !!
WHO DONE IT?
Callous and Unsympathetic Government, Owners siphoning out resources, Uncooperative labour unions fomenting trouble, Conniving brokers and Rigged Auctions?
PASS the BUCK, point accusing fingers. Our bureaucrats are masters of this art no longer, the TEA PRODUCER snatched the crown and what’s more embellished it with a halo. Don’t blame anybody. Take a deep breath, a hard long look at YOURSELF, your Tea Research Institutes and last but not least the jewel in the crown, the great Indian Tea Board.
12My association with the industry began in 1956 as a Brown Sahib planter. Moved to Kolkata in 1974 and observed the workings of tea buying, blending, packaging, brokers and traders for six years. Moved to Bangalore in 1980 to start my own enterprise with the prime motive of developing Tea Processing Machinery based on new concepts. On the 50th anniversary of my association with the industry I have accorded myself the right to let THE CAT AMONGST THE PIGEONS.
A Thumb Nail assessment of the Industry’s revered Institutions:
You, Production Institution, Tea Research Institutes and the Indian Tea Board, You will be dealt with - Last but not least. 13
TEA RESEARCH INSTITUTES:
These temples of Tea learning priested by eminent Scientists have worked tirelessly, at their own pace , analyzed and atomized structure of our regional soils, introduced vegetative propagation with commendable results, in terms of quality and crop. The devotees of these temples were fed the ‘Prasad’ of their achievements through discourses in dribs and drabs. YOU assigned your junior assistants and anyone conveniently spareable to bring home what was imbibed during a few days of learning and frolicking. Shlokas chanted by Temple priests are well above the understanding or comprehension of the devotees. Similarly, discourses of eminent Scientists replete with Botanical, Biological and Technical jargon bolstered by statistics echoed in the auditorium for lack of absorption. They went like this:
“Tea leaves contain a number of bioactive molecules, which confer health properties on tea. Polyphenols or flavonoids, most prominent of which are catechins and their derivatives, are the most abundant, biologically most reactive moleculars and are responsible for most of the health-giving properties of tea. Other bioactive molecules are amino acids like theanine, proteins, caffeine, vitamin C, carbohydrates, polysaccharides, and lipids. In a tealeaf, catechins reside in the cell sap while oxidative enzymes are located in the cell wall.”
On return from these refreshing discourses the now enlightened planter viewed his tea sections as Sunflower fields. Undeniable achievements all around. Let us ask ourselves, did the average farmer who brought in the Green Revolution and Operation Flood know anything about the genetics of the Seed or the biological workings of the Cow ?
With quality and crop on a canter what happened to manufacture/tea processing? A critical aspect of tea production, was it lost in the aura of sunflower fields? Mckercher, a company Engineer, spent years developing the C.T.C machine established the Cut, Tear and Curl cuppage per kilo mantra. C.T.C. Tea gained rapid acceptance in the forties. 14
Twenty years later our temples of Tea learning produced the Mctear Rotorvane that CRUSHED (not CUT) the hell out of leaf, lacerated the stem to produce super raw-material for fiber. Adding insult to injury, the Rotorvane was recommended as a preconditioner for C.T.C. Abundant Fiber content in Rotorvane/C.T.C. Tea resulted in prolific use of winnowers and fiber extractors. Did it occur to You, that every handling results in loss of bloom and is detrimental to liquor. If the CUT element of the Cut, Tear and Curl mantra was ignored, was it on grounds of Quality, Cutting capacity per hour or the financial advantage the Rotorvane brought by eliminating the batch process of rolling?
Was the Rotorvane accepted at the expense of quality? Ask YOURSELF! Suffice to say that top quality producers like Jorehaut, Amguri, Dekari and numerous others didn’t touch it with a barge pole for years till economic considerations forced them to compromise quality.
Where did the concept of Rotorvane come from?
In the early fifties the London Tea Association commissioned WILLIAM TULL an Engineer (unconnected with tea) as a Consultant with a specific brief: suggestions on “Automation Of Tea Manufacture and New Concepts”. The Rotorvane fell squarely in the Automation category.
Orthodox Rollers of various designs and dimensions, Continuous Tray Driers, Sorters et al, old salads in new dressings, were dished out from our Tea research altars. The first truly New Concept Driers came from private enterprise in the early Eighties. Have YOU ever questioned or been concerned about zero developments during the last twenty-five years or the preceding twenty years?
15 :
In 2006 your Tea Processing Equipment designs date back a century almost to the days of the Boston Tea Party. Heaters: 46% heat transfer efficiency, a national waste of precious and expensive mineral resources, Jackson type Orthodox Rollers: a close competitor, CTC’s: circa 1940 vintage.
One Line of Rotorvane/CTC consumes enough energy (H.P) to get an aircraft airborne. This power and fuel wastage at crippling cost and YOU have the gall to point a finger? The measures you took to overcome have resulted in India losing its status as the BEST QUALITY TEA PRODUCER IN THE WORLD. It is amusing, you still think you are. Wake up my friend and accept that you are victim of your own follies.
IT IS NEVER TOO LATE: I reiterate that our Research Institutions have done a commendable job in the field albeit compromises have been made to suit economic feasibility. A Research establishment is meant to find the Goose that lays the golden egg then work towards sustaining it. Cost accounting and Research are two paradigms. It is embarrassing to mention their contribution to New Concept Tea Processing Equipment.
INDIAN TEA BOARD: Just a few sentences to enumerate achievements of this Institution would be adequate. Suffice to say that promotion of Indian Tea should be taken away completely to lighten its burdens. Let it perform the task of correlating statistics, issuing licences, granting scholarships and disbursing subsidies.
Tea promotion should be handled by professionals not relegated officialdom to whom foreign jaunts are a prized perquisite. The Indian stall at the International Tea Convention at Hangzhou, China, in September 2005 should be enough to convince the powers that be.
I venture to make a few suggestions for your consideration:
16 :
Constitute a panel of Tea Manufacture Gurus and invite anybody that has New Concepts in Tea manufacture to bare the principle before them. Be it a mechanic in Howrah, or a multinational - provide a level playing field. Let the panel assess the Concept and if accepted, fund its development BY THE CONCEPTUALISER. Members of the C.C.P.A. should fund this exercise.
In the meanwhile some thoughts on the subject of practical manufacture:
WITHERING: Grant you the right to practice the standard of plucking of your choice. Much has been said about leaf handling in the pluckers fist, transportation field to factory, handling at the factory to avoid leaf damage (crushing, tearing or otherwise disfiguring). To me any leaf in its fresh and green stage is not damaged even if it is crushed, torn or disfigured. Let us keep it in this state. Our institutions of Tea learning have scientifically established that a 14 to 16 hour chemical wither is essential to adequately exploit the liquoring characteristics of the leaf. Let us accept this as a gospel. Take your existing trough, load it 24 inches, blow ambient air to remove latent heat for 2 to 3 hours, throttle airflow to levels that will ensure no physical wither takes place. Store the leaf in this manner and you will find that crushed, damaged, torn leaf will not oxidize. At the end of the chemical wither period 14/16 hours you will have a trough of fresh green leaf with insignificant discolouration of what today constitutes damaged leaf. This will not be even 1% of the weight of the leaf stored.
Develop a Wilting Machine on a Rotary principle to wilt the leaf to desired levels within one hour using high hygrometric differences. In Rotary principle high hygrometric differences do not necessarily lead to inordinate rise in leaf temperature. Experiments have shown that condensation on the leaf surface takes care of this. Loosely fed leaf into a Rotary principle ensures each shoot comes in for individual treatment resulting in an even wither/wilt.
17
6/ LEAF PROCESSING: Experience has shown that a well-maintained efficient Orthodox Roller after 3 rolls achieves no more than 55% cell rupture. In the case of Rotorvane/CTC cell rupture under ideal conditions does not exceed 77% in the leaf and 48 to 50% in the stem.
In this day and age, can we look at means other than brute force to cell-rupture targetting 95%. Let us not forget that the tea crop does not necessarily have to be measured in terms of kilos. Price is determined by cups per kilo. Let us for a change treat cups per kilo as an objective. If an aircraft breaking the sound barrier can shatter windowpanes, surely we can find scientific ways to rupture cells in a Tea Shoot.
DRYING: There exist any number of recognized principles of moisture expulsion. The fact that we have to follow a specific drying curve to exploit the liquor and aromatic characteristics of tea should not deter us from exploring other avenues, conforming to or contradicting this age old guideline.
There is no time for recrimination and postmortems and passing the buck. Let us get on with it with a sense of urgency for Your sake and India’s. Over the years You have invoked the Lord and all the deities that represent HIM. If He could speak He would have told you to enlist an exorcist.
Let the Presidents and Chairmen of the various Tea Associations take a chapter out of London Tea Association book and look for a William Tull. In the meanwhile, for enlightenment, peruse his report and the numerous suggestions he gave on New Concepts in Tea Manufacture.
NOTE :
I have fortified myself against brick bats that this view may attract.
Ranga Bedi Bangalore. 17th February 2006
[email protected]
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