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

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oils when the sum of partial pressures equals the external pressure (Self, 2005). Thus essential oil ingredients, for which boiling points normally range from 100 0 C to 300 0 C are evaporated at a temperature close to that of water (Sawamura, 2010). 2.5.1.2.1 Steam distillation Distillation using water vapour is called steam distillation (Hui et al., 2010). Water is heated in a separate boiler and steam generated is fed into the food sample in the distillation flask (Self, 2005). Volatile constituents pass with the steam into a condenser where both oil and steam will be cooled. Oil and water then separate, the oil which is less dense can be collected (Hay and Waterman, 1993). Essential oils are released from the plant material when the steam bursts sacs containing the oil molecules (Sawamura, 2010). Steam distillation can be used when the material to be distilled has a high boiling point or decomposition can occur if direct distillation is employed (Hui et al., 2010). Food aromas are steam distilled during the cooking process, thus steam distillation is used as an extraction medium for cooked flavour analysis (Self, 2005). 2.5.1.2.2 Steam distillation-solvent extraction The distillate from steam distillation can be a very dilute solution of volatile flavours and water. Flavour must be isolated from the aqueous solution. This is generally done by extracting the distillate with an organic solvent. The organic solvent containing the flavour isolate is dried via the addition of anhydrous MgSO4 or Na2SO4 filtered and concentrated for instrumental analysis. A major disadvantage of steam distillation-solvent extraction is that of an additional solvent step (solvent extraction of the distillate). A method whose isolation efficiency depends on volatility has been combined with a 22
method whose isolation efficiency depends on extraction efficiency. The second step adds additional selectivity and error to the method (Reineccius, 1998). 2.5.1.2.3 Hydrodistillation Plant material is immersed in the water which is kept boiling while contents are mechanically stirred (Heath, 1978). Steam from boiling water carries the volatile oils with it. Cooling and condensation subsequently separate the oil from the water (Sawamura, 2010). Condensation conditions are the similar to those of steam distillation but the condensate water may be returned to the still by way of a special trap (Heath, 1978). Apart from its slowness, the disadvantage of this technique is that both materials and scent deteriorate from constant heat exposure (Sawamura, 2010). Not all oils can be processed by hydrodistillation because boiling water and steam can have deteriorating influence upon delicate flavour substances, moreover, certain raw materials yield no oil during hydrodistillation (Hui et al., 2007). Hydrolysis of certain components of the essential oils and decomposition caused by heat are always present in the hydrodistillation process. As such, hydrodistillation cannot be applied to substances which, even at low temperatures react with water or are hydrolysed by water for example esters (Guenther, 2008). Although hydrolysis is an unavoidable reaction, typically the intensity of hydrolysis is low under the conditions normally used. Decomposition by degradation of some substances can cause interference with the obtained oil odour. Hydrodistillation to extract essential oils should be used keeping the temperature as low as possible (Hui et al., 2010). Solubility in water lowers the vapour pressure of the compound, reduces its capability for vaporisation and impedes the separation of the oil 23
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 and 24: green tea, partly because of the ox
Page 25 and 26: average level of 3 % along with ver
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: mixing and agitating a liquid or so
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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