Green tea cateachins (GTC). namely (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate (EGCG), have been studied extensively for their wide-ranging biological activities. The goal of the present study was to examine the stability of GTC as a mixture under various processing conditions. The stability study demonstrated that GTC was stable in water at room temperature. When it was brewed at 98 degrees C for 7 h, longjing GTC degraded by 20%. When longjing GTC and pure EGCG were autoclaved at 120 degrees C for 20 min, the epimerization of EGCG to (-) gallocatechin gallate (GCG) was observed. The relatively high amount of GCG found in some tea drinks was most likely the epimerization product of EGCG during autoclaving. If other ingredients were absent, the GTC in aqueous solutions was pH-sensitive: the lower the pH, the more stable the GTC during storage. When it was added into commercially available soft drinks or sucrose solutions containing citric acid and ascorbic acid, longjing GTC exhibited varying stability irrespective of low pH value. This suggested that other ingredients used in production of tea drinks might interact with GTC and affect its stability. When canned and bottled tea drinks are produced, stored, and transported, the degradation of GTC must be taken into consideration.

Degradation of green tea catechins in tea drinks.

Extraction of active ingredients from green tea (Camellia sinensis): Extraction efficiency of major catechins and caffeine

The chemistry and biotransformation of tea constituents.

The three main categories of tea: green, black and oolong, result from different processing procedures In recent years tea has attracted more and more attention because of reported health benefits, in particularly as an antioxidant, but also as an anticarcinogenic and antiarteriosclerotic agent It is generally believed that flavonoids are mainly responsible for these actions Tea is now consumed throughout the world not just as a popular beverage, but, because its extracts have been prepared in a variety of physical forms, for example, strong infusions, soft extracts and powders, it is now widely available in a range of food, beverage, and toiletry and cosmetic products

Tea flavonoids: their functions, utilisation and analysis

Green tea catechins during food processing and storage: A review on stability and detection

Stability of tea catechins during heat processing was examined. Effects of pH and temperature on reaction kinetics of degradation of tea catechins were investigated. Reaction of – EC was accelerated at pH higher than 6.0, inhibited at those lower than 5.0. A dominant reaction of – EC in slightly acidic media was isomerization. The apparent first order reaction proceeded in slightly acidic media under sterilization conditions. A similar reaction proceeded for – EC, – EGC, – ECg, and – EGCg in green tea infusion at temperatures below 95°C. A turning point temperature on an Arrhenius plot was observed at 82°C. A great difference of apparent activation energies was observed lower and higher than 82°C. The reaction rate constant of catechins in slightly acidified tea infusion was less than half as much as the constant in the original infusion. The stability of catechins in green tea infusion was subject to the turning point temperature.

/pdf/effects-of-ph-and-temperature-on-reaction-kinetics-of-58krxuy2o3.pdf

Effects of pH and Temperature on Reaction Kinetics of Catechins in Green Tea Infusion

Studies on Preservation of Constituents in Canned Drinks. Part II. Effects of pH and Temperature on Reaction Kinetics of Catechins in Green Tea Infusion.

茶類飲料の機能性成分のうち,特に重要なカフェインおよびカテキン類に着目し,茶類飲料缶詰の市販品についてその含有量の実態調査を行うとともに,飲料缶詰製造時における有効成分の変化を緑茶を中心に調査した.実態調査の結果,茶類飲料缶詰のカフェイン濃度は,標準的な入れ方の2/3程度であり,カテキン類の濃度は1/2～2/3程度であった.また, pHの低い方が概ねカテキン類の残存率は高かった.試作缶詰と標品を用いた実験より以下の結果を得た.カテキン類はカフェインと比較して熱に不安定であった.加熱殺菌により殆んどのカテキン類は減少したが,二次生成物である+Cが著しく増加した. +Cの増加は一ECの異性化に由来すると推定した.クエン酸添加の弱酸性条件下で加熱処理することにより+Cの生成は抑制され,カテキン類の安定化が計れた.従来,茶類飲料缶詰の製造工程では炭酸水素ナトリウムの添加により, pHをやや高めに調整して抽出することが推奨されているが,カテキン類の保護の観点からは浸出液のpHをむしろ微酸性側に保持することが望ましいと言える.

Effects of pH on Stability of Constituents in Canned Tea Drinks

PURPOSE: To provide canned green tea beverages prepared by controlling an extracted amount of components relating to taste, especially astringency and a puckery taste, in a range suitable to low temperature taste, in canned green tea beverage such as SENCHA (Japanese steeped green tea of middle grade) for low temperature drinks, etc., vended at temperature below the normal temperature and production thereof. CONSTITUTION: In an extraction process of tea leaves, when an extraction is carried out at lower temperature range of ≥20°C to <60°C (preferably ≤50°C) than usual using deaerated water having ≤1ppm dissolved oxygen concentration to obtain canned green tea beverage at the normal temperature, the extraction is carried out within an extraction time to obtain 20mg/100ml ≤ total concentration of catechins (total of 4 kinds) ≤40mg/100ml and 30% ≤ concentration of gallic acid ester type catechins (two kinds) over concentration of total catechins ≤40% and the extract thus obtained is used to make the canned green tea beverage. COPYRIGHT: (C)1994,JPO

Canned green tea beverage and its production

PURPOSE: To obtain the subject drink containing natural catechins in desirable state and having excellent taste, flavor and color by extracting tea leaves such as green tea leaves with extraction water of acidic pH range, filling the extract in a container and sterilizing the product. CONSTITUTION: Leaves of green tea such as middle-grade green tea, low-grade green tea or roasted green tea are extracted with extraction water of pH 4.5-5.5, preferably 4.8-5.3 and the extract is filled in a container and thermally sterilized or, after thermally sterilizing, the extract is filled in a container in an aseptic atmosphere. The extraction water is preferably incorporated with an organic acid and/or its salt such as L-ascorbic acid and the dissolved oxygen content of the extraction water is preferably decreased before adjusting the pH of the water. COPYRIGHT: (C)1993,JPO&Japio

Preparation of green tea drink packed in container

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