Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23F—COFFEE; TEA; THEIR SUBSTITUTES; MANUFACTURE, PREPARATION, OR INFUSION THEREOF
  • A23F3/00—Tea; Tea substitutes; Preparations thereof
  • A23F3/06—Treating tea before extraction; Preparations produced thereby
  • A23F3/12—Rolling or shredding tea leaves

Definitions

• the present invention relates to a process for manufacturing green leaf tea products. More particularly the present invention relates to green leaf tea products obtained from fresh tea leaves which are comminuted whilst comprising active endogenous enzymes.
• tea consumed in the Western World is so-called black tea which is obtained by harvesting leaves of the plant Camellia sinensis and withering, rolling, enzymatically oxidizing (fermenting), firing and sorting them.
• the leaves can be processed without the fermentation step to produce what is known as green tea.
• Such tea is widely consumed in parts of the People's Republic of China, Japan, North Africa and the Middle East.
• oolong tea is prepared by partial fermentation. Tea leaves contain a large number of enzymes, biochemical intermediates and structural elements normally associated with plant growth and photosynthesis together with substances that are responsible for the characteristics of tea itself.
• flavanols include flavanols, flavanol glycosides, polyphenolic acids, caffeine, amino acids, mono- and polysaccharides, proteins, cellulose, lipids, chlorophylls and volatiles.
• the amino acid theanine is unique to tea in the plant kingdom and has been associated with several benefits including enhancing mental performance.
• Flavanols or more specifically flavan-3-ols tend to constitute up to 30% of the dry weight of freshly picked tea leaves and are known as catechins. Green tea retains most of the catechins, but their content in black tea is greatly reduced due to both chemical and enzymatic oxidations taking place during fermentation to give theaflavins and thearubigins.
• a thermal treatment e.g. steaming or pan firing
• Sosoft Patent application published as SU 1 400 589 A1 discloses a green tea production method which involves cutting leaves in lengthwise and transverse directions prior to treatment with superheated steam and drying. According to this method the processing of the leaves up to the fixing stage eliminates any damage to the leaves.
• Tea for the purposes of the present invention means material from Camellia sinensis var. sinensis and/or Camellia sinensis var. assamica.
• Leaf tea for the purposes of this invention means a tea product that contains tea leaves and/or stem in an uninfused form, and that has been dried to a moisture content of less than 30% by weight, and usually has a water content in the range 1 to 10% by weight (i.e. "made tea”).
• Green tea refers to substantially unfermented tea. Green tea comprises polyphenols, wherein the polyphenols comprise catechins in an amount of at least 60% by weight of the polyphenols, preferably at least 70%, most preferably from 80-100%. “Green tea” also includes the so-called “white teas”.
• “Fermentation” refers to the oxidative and hydrolytic process that tea undergoes when certain endogenous enzymes and substrates are brought together, e.g., by mechanical disruption of the cells by maceration of the leaves. During this process colourless catechins in the leaves are converted to a complex mixture of yellow and orange to dark- brown polyphenolic substances.
• “Fresh tea leaves” refers to tea leaves and/or stem that have never been dried to a water content of less than 30% by weight, and usually have a water content in the range 60 to 90%.
• the total polyphenol content of a sample is determined using the Folin-Ciocalteu method as detailed in the International Standard published by the International Organization for Standardization as ISO 14502-1 :2005(E).
• catechins is used as a generic term for catechin, gallocatechin, catechin gallate, gallocatechin gallate, epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, and mixtures thereof.
• tea leaves are said to undergo a process under "aerobic conditions" this means that the tea leaves are in contact with an atmosphere comprising gaseous oxygen.
• the atmosphere comprises at least 10% v/v oxygen, more preferably from 15 to 100% v/v oxygen.
• the atmosphere is air.
• steaming means contacting fresh tea leaves with steam at a temperature of 100 °C or more for a period of 1 minute or more thereby to deactivate the endogenous fermentation enzymes.
• pan firing means contacting fresh tea leaves with a hot surface which is at a temperature greater than 200 °C for a period of 5 minutes or more thereby to deactivate the endogenous fermentation enzymes.
• spray drying means spreading fresh tea leaves on a metal surface and then heating (preferably with hot air) to a temperature greater than 70 °C but less than 150 °C to reduce the moisture content of the tea leaves.
• CTC comes from the words “crush, tear and curl”.
• CTC machines and processes are well-known to those skilled in black tea manufacture (see, for example, “Tea: Cultivation to Consumption”, K.C. Willson and M.N. Clifford (Eds), 1st Edn, 1992, Chapman & Hall (London), Chapter 14, pp. 483-485, which is hereby incorporated by reference in its entirety). Where reference is made to at least one CTC process or machine, this means at least one pass through a pair of CTC rollers.
• leaf particle size is characterised by sieve mesh size using the following convention:
• a "+" before the sieve mesh indicates the particles are retained by the sieve.
• a "-" before the sieve mesh indicates the particles pass through the sieve.
• the particles will pass through a 5 mesh sieve (particles smaller than 4.0 mm) and be retained by a 20 mesh sieve (particles larger than 841 ⁇ ).
• the leaves are preferably dried prior to sieving. Miscellaneous
• any particular upper concentration can be associated with any particular lower concentration or amount.
• the present invention provides a process for manufacturing a green leaf tea product, the process comprising the steps of:
• the present invention provides a leaf tea product obtained and/or obtainable by the process.
• a leaf tea has the high catechin content of conventional green teas but has modified infusion properties afforded by the process such that it produces infusions which are low in organic acids, such as gallic acid and quinic acid, have an unexpectedly mild taste and which have substantial amounts of theanine.
• Fresh tea leaves are employed in the process of the present invention.
• the fresh leaves are comminuted without withering.
• the fresh tea leaves are withered, it is preferred that the fresh tea leaves are withered to a moisture content of less than 75% by weight, more preferably to a moisture content in the range of 63 to 73 wt%.
• the leaves are not withered prior to comminution.
• the leaves are not withered and so have a moisture content of at least 75 wt% when comminuted, more preferably from 76 to 80 wt%.
• Comminution of the fresh tea leaves occurs under aerobic conditions as this appears to allow limited fermentation-like reactions to occur in the tea leaves leading to a mild flavour in tea beverage prepared from the final leaf tea. It is preferred that the leaves are comminuted to significantly reduce the leaf particle size. In particular it is preferred that at least 50 wt% of the comminuted fresh tea leaves have a particle size of -5 mesh, more preferably at least 70 wt% and most preferably from 90 to 100 wt%. The comminution is preferably not such as to reduce the leaf particle size excessively as then fermentation may be accelerated in the leaves.
• At least 50 wt% of the comminuted fresh tea leaves have a particle size of +20 mesh, more preferably at least 70 wt% and most preferably from 90 to 100 wt%.
• the fresh leaves comprise active endogenous enzymes, such as oxidases, peroxidises or a combination thereof, during comminution.
• active endogenous enzymes such as oxidases, peroxidises or a combination thereof.
• the comminution is relatively severe and results in significant disruption of the leaves as evidenced by bruising of the leaves. Such damage may be suitably achieved by passing the fresh tea leaves through at least one CTC process.
• the fermentation-like reactions must not be allowed to destroy the majority of the catechins, otherwise the final product would not have green-tea character.
• the degree of fermentation is conveniently judged by the proportion of oxidised catechins.
• a quantity, Co which is the amount of catechins in the fresh tea leaves prior to comminution in percent by dry weight of the fresh leaves.
• CF which is the amount of catechins in the comminuted fresh tea leaves after the enzyme deactivation step in percent by dry weight of the comminuted leaves.
• R the degree of fermentation
• the fermentation is arrested by enzyme inactivation to substantially prevent fermentation.
• the enzyme deactivation occurs to prevent the content of catechins in the fresh tea leaves falling below 60% of the content of catechins of the fresh tea leaves prior to comminution on a dry weight basis, i.e. before R falls below 60%.
• the endogenous enzymes in the comminuted fresh tea leaves are inactivated to prevent the content of catechins in the fresh tea leaves falling below 70% (most preferably 80%) of the content of catechins of the fresh tea leaves prior to comminution on a dry weight basis.
• enzyme deactivation occurs when the content of catechins in the fresh tea leaves is below 95% of the content of catechins of the fresh tea leaves prior to comminution on a dry weight basis (i.e. R is less than 95%). More preferably enzyme deactivation occurs when the content of catechins in the fresh tea leaves is below 90% of the content of catechins of the fresh tea leaves prior to comminution on a dry weight basis, most preferably below 85%.
• the final leaf tea product is obtained by drying the comminuted fresh tea leaves.
• the enzyme deactivation can be effected simultaneously with drying thus removing any need for a separate enzyme deactivation step such as steaming or pan firing.
• the enzyme deactivation may be achieved by tray drying and/or fludized bed drying the comminuted fresh tea leaves to yield the green leaf tea product.
• the final leaf tea product may be sorted according to particle size.
• the final product is sorted to recover a fraction wherein at least 50 wt% of the leaf tea has a particle size of -5 +20 mesh, more preferably at least 70 wt% and most preferably at least 90 wt%.
• the leaf teas prepared by the process have a relatively high gallic acid content but nevertheless produce infusions with acceptable amounts of gallic acid and less metallic aftertaste.
• the leaf teas may have a gallic acid content of at least 0.4 mg per g of dry leaf, more preferably at least 0.5, more preferably still at least 0.6 and most preferably from 0.7 to 2.0 mg/g.
• This example demonstrates the effect of process variation on the composition of beverages made from the resulting green leaf teas.
• Samples were prepared from a China clone of var. sinensis, a Yabukita clone of van sinensis or with material from var. assamica. Sample Preparation
• Freshly-plucked tea leaves were collected. The fresh leaves were steamed to inactivate the enzymes, comminuted in a CTC process and then fluid-bed dried to yield the green leaf tea.
• SAMPLE 2
• Freshly-plucked tea leaves were collected.
• the fresh leaves were comminuted (without any enzyme deactivation) in a CTC process and then fluid-bed dried to yield the green leaf tea.
• the green leaf tea was prepared in an identical manner to sample 2 except that prior to comminution, the fresh leaves were withered to a moisture content in the range 66-70 wt%.
• Freshly-plucked tea leaves were collected and withered to a moisture content in the range 66-70 wt%.
• the withered leaves were then comminuted (without any enzyme deactivation) by passing them through a vegetable cutter and then tray dried. The dried leaves were then crushed to reduce particle size.
• Sample 1 is similar to conventional steamed green tea
• Sample 4 is similar to the leaf teas produced by the process of SU 1 400 589 A1
• Samples 2 and 3 are leaf teas made according to the present invention.
• composition of the leaf teas (determined by HPLC analysis of extracts obtained by exhaustive extraction with methanol) are given in the table below.
• Source Sample Amount (mg / g) by dry weight of leaf R (%) No. Gallic Theogallin Caffeine Total
• samples made without an enzyme deactivation step prior to comminution generally produced infusions with significantly lower amounts of theanine, caffeine, quinic acid and gallic acid than those from Sample 1.
• samples comminuted by CTC withering prior to comminution reduced these effects (i.e. Sample 3 was most similar to Sample 1 ).
• Sample 4 produced infusions with much reduced levels of the desirable amino acid theanine (i.e. delivering only around half of the theanine of infusions of Sample 1 ).
• This example demonstrates the sensory properties of beverages made from the leaf teas.
• Leaf tea from a China clone of var. sinensis was prepared using a process identical to that for Sample 2 described in Example 1.
• the leaf tea was dosed into tea bags in an amount of 1.3 g per bag.
• a commercially available green leaf tea blend was also dosed into tea bags in an identical amount.
• 5 bags of each leaf tea were brewed in a litre of freshly boiled commercially-available spring water (2 min static brew, stir once, and then strain).
• the resulting brews were stored in vacuum flasks and then subjected to quantitative testing by a trained sensory panel. Significant differences were found between the infusions prepared from the sample according to the invention compared with those prepared from the conventional blend.
• the brew from the leaf tea of the present invention was found to deliver:

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• Polymers & Plastics (AREA)
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• 2011
  • 2011-08-10 IN IN615MUN2013 patent/IN2013MN00615A/en unknown
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