a study of the quality of a local herbal tea and volatiles of parinari ...

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During fermentation, enzymatic oxidation of catechins takes place leading to the formation of theaflavins and thearubigins which are responsible for the characteristics of black tea infusions (Liang et al., 2005a). Thus, depending on the extent of fermentation the colour of teas will vary accordingly, leading to the colour difference between different samples of tea types, such colour differences could be used to differentiate between various teas irrespective of the type of processing (Liang et al., 2005a). Confirmation was been obtained that theaflavin content is an extremely important factor in determining quality in black tea (Robert and Smith, 1963). Separate studies have shown that theaflavins are useful black tea quality parameters, which when used properly, can give objective estimate of plain black tea quality irrespective of geographical area of production (Okinda Owour, 2005). Theaflavins and thearubigins contribute to the astringency/ brightness/ briskness and colour/strength/mouthfeel respectively of black tea (Sud and Baru, 2000). Theaflavins, found predominantly in black tea, combine with caffeine to form a substance known as cream thereby modulating the bitterness and stringency of the individual compounds and giving tea its flavour (Hamilton-Miller, 1995). Theaflavin (together with its mono- and di-galloyl derivatives) are constituents of the polyphenol content of tea not only influencing its colour but also contributing to the characteristic taste (Charlton et al., 2000). Caffeine (1,3,5-trimethylxanthine), a mild addicting drug though used for medicinal purposes is the active ingredient that makes tea valuable to humans (Wanyika et al., 2010). Caffeine, theophylline and theobromine are important quality factors in green and black teas (Schulz et al.,1999; Sharma et al., 2004). Caffeine is present in tea at an 8
average level of 3 % along with very small amounts of the other common methylxanthines (theobromine and theophylline)(Graham, 1992). Caffeine has a bitter taste (Charlton et al., 2000). The amino acid theanine (5-Nethylglutamine) is unique to tea (Graham, 1992). It is the main amino acid component in tea and usually constitutes between 1 and 2 % of the dry weight of the tea leaves (Ekborg-Ott et al., 1997). Free amino acids in tea leaves are important chemical constituents that considerably influence the quality of tea, especially that of green tea (Ruan et al., 1998). Theanine is as prevalent in tea as all the other free amino acids combined and both enantiomers of theanine were found to have similar sweet taste with little or no aftertaste (Ekborg-Ott et al., 1997). Volatile components make up a very small fraction of flush and tea leaf (10 to 20 ppm) but play an important part on its flavour (Hamilton-Miller, 1995). These flavour components are one of the most important factors to influence the flavour, taste and quality of Pu-erh tea (Liang et al., 2005b). Volatile constituents of green tea gyokuro (C. sinensis) were investigated; seventy-nine compounds were positively identified. Major constituents were identified as 2,6,6-trimethyl-2-hydroxycyclohexanone, linalool, geraniol, cis-jasmone, β-ionone and cyclohexanone, 5,6-epoxy-β-ionone, indole, and caffeine (Yamaguchi and Shibamoto,1981). In fennel tea (Foeniculum vulgare Mill.), fenchone and trans-anethole were demonstrated to play an important role in the tea flavour (Zeller and Rychlic, 2006). 9
Page 1 and 2: A STUDY OF THE QUALITY OF A LOCAL H
Page 3 and 4: DECLARATION BY THE CANDIDATE I the
Page 5 and 6: DEDICATION I dedicate this thesis t
Page 7 and 8: ABSTRACT This study concerned the q
Page 9 and 10: TABLE OF CONTENTS DECLARATION BY TH
Page 11 and 12: 2.6.5 F. ancylantha Schweinf ......
Page 13 and 14: 3.10.1 GC and GC-MS conditions for
Page 15 and 16: LIST OF TABLES Table 4.1: Quality p
Page 17 and 18: 1.1 Background CHAPTER 1: INTRODUCT
Page 19 and 20: Considering the benefits associated
Page 21 and 22: A local herbal tea made from F. anc
Page 23: green tea, partly because of the ox
Page 27 and 28: alcohols, aldehydes, esters, ethers
Page 29 and 30: Scheme 2.1: : Enzymatic degradation
Page 31 and 32: In Scheme 2.2 linolenic acid is tra
Page 33 and 34: alkylating agent. DMAPP possesses a
Page 35 and 36: cinnamaldehyde and coumarin (cinnam
Page 37 and 38: mixing and agitating a liquid or so
Page 39 and 40: method whose isolation efficiency d
Page 41 and 42: immersed directly into the sample s
Page 43 and 44: (1958) as a parameter for identifyi
Page 45 and 46: natural product was identified. The
Page 47 and 48: (Larkcom, 2007). Taro leaves and le
Page 49 and 50: 2.6.5 F. ancylantha Schweinf F. anc
Page 51 and 52: 2 cm broad, valvate, with 1-3 subgl
Page 53 and 54: Fruits and vegetables were placed i
Page 55 and 56: 3.4 Preparation of chemicals and re
Page 57 and 58: and SII (Robert and Smith, 1963). T
Page 59 and 60: Where the (E(1cm)0.02 %) value for
Page 61 and 62: Distillation was carried out for 4
Page 63 and 64: done to remove particles of Na2SO4.
Page 65 and 66: 3.8.6 Hydrodistillation and solvent
Page 67 and 68: experiment was continued for 57 min
Page 69 and 70: 3.10 Identification of volatile con
Page 71 and 72: CHAPTER 4: RESULTS AND DISCUSSION 4
Page 73 and 74: Significant (p
Page 75 and 76:
Using the hydrodistillation and sol
Page 77 and 78:
4.3 Volatile constituents of S. coc
Page 79 and 80:
The SPME method identified 11 compo
Page 81 and 82:
Esters constituted (83.3 % %) while
Page 83 and 84:
Table 4.6: Compounds identified aft
Page 85 and 86:
4.4.2 Identity of volatile flavour
Page 87 and 88:
Table 4.9: Compounds identified aft
Page 89 and 90:
Seven compounds made up oof f carbo
Page 91 and 92:
CHAPTER 5: CONCLUSIONS AND RECOMMEN
Page 93 and 94:
5.2 Recommendations In order to exp
Page 95 and 96:
Chalton, A.J., Davis, A.L., Jones,
Page 97 and 98:
G1Innovations. (2003). Innovations
Page 99 and 100:
sims F.Flavicarpa Degner) as determ
Page 101 and 102:
agricultural and Pastoral communiti
Page 103 and 104:
Reineccius, G., and Heath, H.B. (20
Page 105 and 106:
Sawamura, M. (Ed.). (2010). Citrus
Page 107 and 108:
Vas, G., and Vekey. K. (2004). Soli
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