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ABSTRACT

   Some of the change's occurring during storage of tea are described.
     Teas are often subject to varying periods 3-6 months of storage from the time of production to reaching consumers. The changes which occur during storage have been studied by several workers, who have identified factors which affect the characteristics of tea.  Among these are the increase of moisture accompanied by growth of microorganisms (1), increase in thearubigins and extractable caffeine, and decline in theaflavin levels (2-4). An important factor in the decline of theaflavin leavels in stored tea is the residual polyphenol oxidase and peroxidase activity in processed black tea. It was also shown that storage of tea under extreme conditions of low temperature, low moisture, and low oxygen availability, as well as acid treatment of tea during the fermentation stage of manufacture, led to a maarked reduction in residual enzyme activity and a decrease in the rate of deterioration of the theaflavin during storage.
      Studies of chemical changes occurring during storage (5) showed that storage led to a loss of flavor and astringency, and the development of undesirable characteristics. These changes were accompanied by lipid hydrolysis; loss of theallavins, amino acids, sugar, and photosynthetic pigments; and an increase in nondialysable pigments. These changes were accelerated by high moisture and elevated temperatures. Different tea clones showed variations in the rate as well as extent of the theaflavin degradation. It was observed that teas made during the hot and humid season in Malawi deteriorated more rapidly in theaflavin content.
       Dougan et al. (6) reported that the decline in the value of tea during a storage period of 6 months was attributable to the effect of temperature and moisture on theaflavin content, briskness, strength, color of infused leaf, and flavor. About half the loss of value was the result of the decrease of theaflavin content and other udidentified compounds which were affected equally by changes in moisture content and temperature.
       Relationships were studied between chemical composition, acceptability, time of storage, temperature, and moisture content. Tea was stored for varying times at temperatures of 15
℃,25℃,and 35℃, under relative humidities of 33%, 57%, and 75%. In this study, theaflavins, catechins, thearubigins, total soluble solids, and moisture content, as well as changes in the composition of volatile compooounds, were determined.
   Studies of the changes in chemical constituents of nonprocessed tea leaves during storage in different mixtures of nitrogen, oxygen, and carbon dioxide showed differences in oxygen uptakeand carbon dioxide output, and marked changes in ascorbic acid and amino acids, but hardly any changes in  tannin and caffeine (7).
   Microbiological change during storage of tea (8) with free access to air and moisture consisted of steady increase in fungal growth; the bacterial count, how ever,  remained constant. The bacterial count stabilized at about 10 microorganisms per gram, which suggests the bacteriostaatic property of tea.
   An investigation of the polyphenolic constituents of liquors prepared by brewing black tea in boiling water (9) showed that exposure to high temperatures during storage led to a decrease in theaflavin content and resulted in an off taste. In this study, it was also  found addition of antioxidants, such as ascorbic acid, or the addition of antimicrobial reagents, such as benzoatess, was helpful in preserving the quality of tea liquors.
   Investigations of the aroma components of various teas during storage (10) revealed the occurrence of chemical changes in nonfermented sencha green teaa, semifermented pouchong tea, and in black tea. Development during storage of 2,4 heptadienal, hexanoic acids, and ionone-related compounds was common to all types of tea although specific trends were different. Yamanishi (11) reported that deterioration of quality of green tea was accompanied by:
   
   1.Reduction in vitamin C content.
   2.Change in color from bright green to olive green to dull 
     brownish-green
   3.Change in color of tea liquor from bright yellow or
     slightly greenish to brownish-yellow.
   4.Change in aroma from leafy and refreshing to dull and
     heavy.
   5.Change of well-balance taste of astringency and
     bitterness to "flat" taste.

    As in the case of black tea, these changes during storage of green tea are accelerated by moisture, oxygen, elevated temperatures, and exposure to light.
    The basis understanding of factors which bring about changes during the storage of tea may be useful for devising means for preserving tea in its freshly processed form, which would overcome some of the difficulties in the proposed establishment of a tea buffer stock for stabilizing market prices.
    
    EFFECTS OF THE TIME AND INTENSITY OF ROOT PRUNING ON ROOT REGENERATION IN TEA PLANTS.

    Masataka Yamashita, Kurume Branch, National Research Institute of Vegetables, Ornametal Plants and Tea. 14041 Beppu, Makurazaki-shi, Kagoshima, 898 Japan
   
    It has been pointed out that root systems play important roles to shoot growth, yield and quality. But, there are a few researches on roots or root systems because the influences of roots on the yield and quality are indirect, the observation of roots requires much labour and time and direct managements to roots are difficult. The roots, however, support the nutrient and water uptake, and biosynthesis of some hormons and useful chemical components. Therefore, the development and functions of root systems could greatly control the shoot growth, yield and quality.
    On basis of this conception, the rejuvination of the tea plants by the root pruning technique has been studied. It has experientially known that the technique was affected by many factors such as time, intensity and frequency of pruning, manuaring, variaties, plant age, plant vigour and relationship between the root regeneration, and the time and intensity of the root pruning were discussed.
   

 



 

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