Sulfur brightens the brew.
Tea, like other crops, requires the full and balanced complement of nutrients. These include Nitrogen (N), Potassium (K), Phosphorous phos·pho·rous
Of, relating to, or containing phosphorus, especially with a valence of 3 or a valence lower than that of a comparable phosphoric compound. (P), Sulfur (S), Magnesium (Mg), Manganese (Mn), Zinc (Zn), Copper (Cu) and Iron (Fe). However, tea has a particular need for sulfur, over and above its function as a major nutrient for rapid healthy growth and development.
Sulfur is important as a soil amendment chemical to generate and maintain a favored low pH for the acid-loving tea bush. The most important commercial function lies in its close association with specific tea chemicals that give the liquor its sought after taste, color, brightness, strength and body. It seems strange that the quality of a fine aroma beverage like tea should depend heavily on an unpleasant smelling chemical like sulfur. But there is a lot more to sulfur than meets the eye.
Sulfur is one of the oldest known elements and referred to in antiquity as "biblical brimstone brimstone: see sulfur. ." It is widely abundant in the earth's crust and closely associated with volcanic activity and hot water springs. As a yellow solid that burns with a pungent smell, sulfur has long been associated with all things evil. But there is an aesthetic and health-giving side to sulfur that comes through strongly in the cupped infusion of tea.
Sulfur has long been used in ointments ointments,
n.pl semisolid, non–water-based treatments that are not water-soluble and that create protective films to prevent dehydration of the skin. to cure skin complaints and featured strongly in some the very first drugs (sulfa drugs sulfa drugs
a group of chemical compounds used as antibacterial agents; called also sulfonamides. ) used as antibiotics, indeed, tea was first consumed as a medicine in the Yangtze Kiang kiang: see ass. Valley of China around 2700 BC. And today after water, tea is the most heavily consumed drink in the world because of its health giving, dietetic dietetic /di·e·tet·ic/ (di?ah-tet´ik) pertaining to diet or proper food.
1. Of or relating to diet.
2. and even therapeutic properties.
For many years farmers and growers were indulged with free sulfur as non-costed "rider" impurities in NPK NPK Nitrogen, Phosphorous, Potassium
NPK Non-Player Killer fertilizers. As byproducts of industry, it was spewed out and spread over the land by coal-fired power stations and factory, chimneys.
But forward-thinking governments backed using modern technology to clean up and "green-up" the environment. And with it came the progressive "de-greening" of crops when sulfur deficiency started to show as leaf yellowing or chlorosis chlo·ro·sis
A form of chronic anemia, primarily of young women, characterized by a greenish-yellow discoloration of the skin and usually associated with deficiency in iron and protein. Also called chloremia. .
The early signs in many crops were confusing because the leaf yellowing of sulfur deficiency symptoms is not unlike that for nitrogen. Nitrogen deficiency Nitrogen (N) deficiency in plants can occur when woody material such as sawdust is added to the soil. Soil organisms will utilise any nitrogen in order to break this down, thus making it temporarily unavailable to growing plants. shows first in older leaves, while sulfur deficits affect the youngest leaves. Eventually scientists began to look at the role of sulfur in the growth, development and quality, of crops, and none more so than Camellia camellia (kəmēl`yə) [for G. J. Kamel, a Moravian Jesuit missionary], any plant of the genus Camellia in the tea family, evergreen shrubs or small trees native to Asia but now cultivated extensively in warm climates and in Sinensis--the tea plant.
Sulfur Requirements for Tea
Sulfur requirement for tea is very high at 16 to 26 kg/hectare/year. But this should come as no surprise since tea grows naturally on soils of volcanic origin, created by the very same geological processes that create elemental sulfur in large amounts.
The sulfur content of fresh green tea leaves should be maintained at 8% to 2% on a dry matter basis to achieve maximum yields of fresh leaves which can be processed into high quality tea products. In order to produce one ton of finished tea, the factory requires five tons of freshly picked leaves that will have extracted no less than 10 kg of sulfur from the soil. And tea production by its very nature, with regular plucking of the youngest and most nutrient-rich foliage, will exhaust soil nutrients including sulfur if fertilizer applications are not made.
When averaged out over the whole tea bush, the sulfur content of leaves is way down in the list of nutrients. But when nutrient analysis is targeted on the third youngest unfurled leaf, sulfur shoots up to rank equal third with phosphorus.
These figures are clearly important given the selection of new shoots during picking for processing terminal buds (golden tips) and young leaves into the finest grade teas. Plucking the terminal bud plus three leaves gives the highest yield of quality shoots some 25% more than bud plus two leaves. And finished tea products based on shoots picked to include this third leaf are premium teas, with high concentrations of two important tea chemicals, polyphenols (tannins tannins,
n.pl polyphenolic phytochemicals whose name derives from their use in tanning animal skins. Used as astringents, antioxidants, and styptics; treats burns, relieves diarrhea. ) and theine The´ine
n. 1. (Chem.) See Caffeine. Called also theina ltname>. (tea caffeine).
Up to 40% of the sulfur absorbed by tea roots will be recycled into the soil as fallen mature leaves and pruning waste, but there is still a considerable shortfall. A tea harvest weighing in at 3000 kg will have removed some six to nine kg of sulfur/hectare/year from the soil, say researchers at the internationally famous Tocklai Experimental Station in Jorhat India, home of the famous Assam teas. Field trials showed soils in the tea-growing areas of North Eastern India become seriously depleted de·plete
tr.v. de·plet·ed, de·plet·ing, de·pletes
To decrease the fullness of; use up or empty out.
[Latin d of sulfur through continuous picking, unless suitable fertilizer application programs are in place.
Sulfur shortfalls on tea estates are nothing new. Indeed sulfur deficiency symptoms in tea bushes, called "sulfur yellows" or "yellow disease," have long been recognized in East and Central Africa. Sulfur is central to plant nutrition Plant nutrition is the study of the chemical elements that are necessary for plant growth. There are several principles that apply to plant nutrition.
Some elements are essential, meaning that the absence of a given mineral element will cause the plant to fail to complete . It is needed for synthesis of sulfur containing essential amino acids essential amino acid
An alpha-amino acid that is required for protein synthesis but cannot be synthesized by humans and must be obtained in the diet. like cysteine cysteine (sĭs`tēn), organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of mammalian protein. and methionine methionine (mĕthī`ənēn), organic compound, one of the 20 amino acids commonly found in animal proteins. Only the L-stereoisomer appears in mammalian protein. and for the manufacture of chlorophyll pigments. When in short supply, chloroplasts break down and with it the normal dark green color of tea foliage.
Young leaves are the hardest hit by an unhealthy looking pale yellow color, and general yellowing of the inter-veinal areas. New shoots are smaller and internodes (distance between leaves) shorter due to a slow down in growth that is followed by general shoot necrosis if sulfur deficiency persists.
Consequences for yield and tea quality are severe; new shoots comprising bud and two to three leaves are selected for the finest grade tea. To make matters worse, leaf yellowing symptoms are exacerbated by lower temperatures, the very conditions experienced at night on the hillsides where tea is typically grown. Indeed sulfur is known to enhance frost resistance of tea bushes.
"Sulfur yellows" are an ongoing problem in countries such as Kenya, Uganda, Malawi and Zambia to a degree that demands remedy with sulfur fertilizer. Originally there was no such thing as a dedicated sulfur fertilizer. The tea estates applied sulfur through nitrogen and potassium fertilizers such as ammonium sulfate ammonium sulfate, chemical compound, (NH4)2SO4, a colorless-to-gray, rhombohedral crystalline substance that occurs in nature as the mineral mascagnite. It is soluble in water and insoluble in alcohol or liquid ammonia. and potassium sulfate that have sulfur in the molecule.
Now with universal need for sulfur for crops in general, the industry has responded with new and dedicated sulfur fertilizers. Products containing yellow elemental sulfur as pastilles or prills are widely used and especially on tea. The sulfur is degraded in the soil by Thiobacillus bacteria to form soluble sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). that is absorbed by the root system of the tea bush.
But selective use of traditional fertilizer with a sulfur component is still important. For instance, Tocklai researchers report increased problems with sulfur deficiency following replacement of ammonium sulfate (a sulfur containing nitrogen fertilizer) and single super phosphate (a sulfur containing phosphate fertilizer). These were substituted with urea and rock phosphate rock phosphate
a mined mineral used as a fertilizer and as a dietary phosphorus supplement for animals. Some deposits of the mineral contain high levels of fluorine and its use as a feed supplement leads to poisoning in the livestock. See also fluorosis. , respectively, neither, of which have sulfur in the molecule.
Sulfur fertilizers are additionally used as soil amendment products, to increase soil acidity in tea estate rehabilitation. Trials by the Tea Research Foundation of Kenya on the Kapchorua Tea Estate using a water degradable de·grad·a·ble
That can be chemically degraded: degradable plastic wastes.
de·grad sulfur pastille pas·tille or pas·til
1. A small medicated or flavored tablet; a troche.
2. A tablet containing aromatic substances that is burned to fumigate or deodorize the air. called "Brimstone 90" (90% elemental sulfur) showed real benefits. This dedicated sulfur fertilizer reduced soil pH from 6.3 to 5.5, a feat not achieved by the normally used aluminum sulfate. The tea bush demands an acid soil with a pH between 4.5 and 5.5, and performs poorly in soils that are too compact or alkaline.
Sulfur and Tea Quality
Everyone knows that correctly dosed and balanced fertilizer improves crop. The benefits are generally difficult to pin down, but tea is different. The fresh green leaves are put through a series of exhaustive processes, including withering, rolling, fermentation and firing. This generates and consolidates a group of all-important chemicals that combine to determine tea quality through flavor and aroma, body, strength, color and brightness of the liquor. Tea processing ends with the infusion to leach out the chemicals into hot water for assessment by expert tasters. And results from this ultimate test can be used to pin-point the effect of growing conditions including soil nutrient status.
This is exactly what has been done at Tocklai, where tea agronomists, food scientists and tasters have identified the significance and exact role of sulfur in tea quality. Field trials over a six-year period using a variety of sulfur sources, including gypsum gypsum (jĭp`səm), mineral composed of calcium sulfate (calcium, sulfur, and oxygen) with two molecules of water, CaSO4·2H2O. It is the most common sulfate mineral, occurring in many places in a variety of forms. (calcium sulfate), ammonium sulfate and micronized elemental sulfur gave positive responses but only up to a certain level. Tea yields increased with application of sulfur up to 40kg hectare/year, with 20 kg/hectare/year being the most cost-effective treatment.
The color, brightness, strength, body, taste and favor of the tea liquor are adversely affected by sulfur-deficiency. But the Tocklai trials went farther and related changes in these parameters to levels of specific chemicals in leaves.
The tea was produced by CTC CTC - Cornell Theory Center (crushing, tearing and curling), the most commonly used method of rolling in the indian tea industry. Key tea chemicals were measured using biochemical analysis and HPLC HPLC high-performance liquid chromatography.
high performance liquid chromatography.
HPLC High-performance liquid chromatography Lab instrumentation A highly sensitive analytic method in which analytes are placed (High Performance Liquid Chromatography High-performance liquid chromatography (HPLC) is a form of column chromatography used frequently in biochemistry and analytical chemistry. It is also sometimes referred to as high-pressure liquid chromatography. ) of black tea liquors, and tasters from J. Thomas & Co Limited in Calcutta were used to assess organoleptic or·gan·o·lep·tic
1. Relating to perception by a sensory organ.
2. Involving the use of sense organs.
Tasters' scores at 74.0 for tea produced with 20kg sulfur/hectare were by far the highest, 13.7 higher than no sulfur and a full 10.0 higher than 40kg sulfur/hectare. Objective quality factors showed the same trend with brightness and total color responding positively to sulfur fertilizer.
Two groups of chemicals called theaflavins and thearubigins are responsible for body, strength, taste, odor and the bright amber/red color of quality liquor were key to the quality equation. They were found in higher concentrations following sulfur application, with 20kg sulfur/hectare giving the best overall result (Table 3). Marginal increases in the flavonol glycosides such as rutin Ru´tin
n. 1. (Chem.) A glucoside resembling, but distinct from, quercitrin. Rutin is found in the leaves of the rue (Ruta graveolens and quercetin quer·ce·tin
A yellow powdered crystalline compound produced synthetically or occurring as a glycoside in the rind and bark of numerous plants, used medicinally to treat abnormal capillary fragility. Also called meletin. are thought to have contributed to brighter color and enhanced flavor.
The contribution of sulfur to the bright, amber-red color of quality black tea liquor is particularly interesting. Sulfur in its common solid state is a yellow powder. On heating its melts to give a bright amber liquid which crystallizes on cooling to produce amber crystals with a color and shine uncannily similar to that of quality black tea liquor.
These findings can be related to original concentrations of polyphenols in fresh leaves. Because theaflavins and thearubigins are produced by enzyme controlled oxidative reactions on polyphenols during fermentation. Polyphenols are heavily concentrated in the youngest growth, terminal bud (28%), smallest (first) leaf (28%), second leaf (21%) and third leaf (18%).
In summary, sulfur deficiency hits hard at young growth (terminal buds and first three unfurled leaves) selectively plucked for the fine grade teas. These have the highest concentration of polyphenols converted during fermentation by polyphenol oxidase enzymes into the all important tea chemicals responsible for quality liquor.
Nutrient levels over all leaves on the tea plant Nitrogen 4.00 to 5.00% Potassium 1.50 to 2.00% Phosphorus 0.40 to 0.90% Calcium 0.30 to 0.90% Magnesium 0.30 to 0.05% Sulfur 0.08 to 0.20% Nutrient levels in the third youngest leaf on tea shoots Nitrogen 5.00% Potassium 3.00% Sulfur 0.50% Phosphorous 0.50% Calcium 0.35% Magnesium 0.30% Sulfur and tea liquor quality * Sulfur Rate Theaflavin Thearubigin Brightness Total Color (kg per ha) (%) (%) (%) (Score) 0 2.6 13.0 37.7 7.6 20 2.7 13.9 38.5 7.9 40 2.7 13.0 39.1 7.7 60 2.6 12.8 0.39 7.4 * From: Barbora, 1995
Twin Boost for Tea with SOP
Sulphate of potash (potassium sulphate or SOP) tips the balance in favor of tea says Kali und Salz (K+S), producer of quality fertilizers at Kassel in Germany. K+S offer a wide range of fertilizer products based on SOP, including those that are custom-designed for low and virtually zero levels of chloride for chloride sensitive crops like tea.
Tea requires potassium and sulfur too, so SOP offers a twin boost for tea crops to give fast growth and healthy development. Many years of intense tea production in traditional tea growing areas has reduced the natural fertility of soils on many estates. But balanced fertilizer programs using SOP will sustain a high yield level of freshly picked leaves. Research on green tea in China showed sulfur rich SOP to give a general increase in the free amino acid amino acid (əmē`nō), any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins. content of leaves and a boost to tea quality.
Additional tea quality benefits provided sulfur rich SOP, also demonstrated in China, were recorded in black tea, green tea and oolong oo·long
A dark Chinese tea that has been partially fermented before drying.
[Chinese (Mandarin) w tea. Of key importance, says K+S, is the beneficial affect of SOP on polyphenols (tannins) in the fresh leaves. And on the aroma, color and body producing chemicals like theaflavin, thearubigin and theabrown, that are produced by oxidation of polyphenols during the processing of black tea.
For more information, contact Dr. Marcus Ross, Tel: (49)561-9301-2417, Fax: (49)561-9301-1416, E-mail: firstname.lastname@example.org