Developing an Index of Quality for Australian Tea
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Developing an index of quality for Australian tea By Nola Caffin Bruce D’Arcy Lihu Yao Gavin Rintoul The University of Queensland May 2004 RIRDC Publication No. 04/033 RIRDC Project No. UQ-88A © 2004 Rural Industries Research and Development Corporation. All rights reserved. ISBN 0 642 58743 4 ISSN 1440-6845 Developing an index of quality for Australian tea Publication No. 04/033 Project No. UQ-88A The view expressed and the conclusions reached in this publication are those of the authors and not necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any perso who relies in whole or in part on the contents of this report. This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone 02 6272 3186. Researcher Contact Details Nola Caffin School of Land and Food Sciences The University of Queensland St Lucia, QLD 4072 Phone: 07 3346 9187 Fax: 07 3365 1177 Email: [email protected] In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form. RIRDC Contact Details Rural Industries Research and Development Corporation Level 1, AMA House 42 Macquarie Street BARTON ACT 2600 P Box 4776 KINGSTON ACT 2604 Phone: 02 6272 4819 Fax: 02 6272 5877 Email: [email protected] Website: http://www.rirdc.gov.au Published in May 2004 Printed on environmentally friendly paper by Canprint ii Foreword Although the production of black tea is currently small in Australia, compared to some of the main tea producing countries, the availability of suitable land and increasing experience of cultivation and processing should permit the rapid development of a viable tea industry. The tea industry in Australia has significant potential for import replacement. Current production supplies only 5-10 % of current consumption in Australia. Quality has been recognised as a very important factor in maintaining the competitiveness of Australian grown and made tea. The Australian tea industry needs data to assist with improving tea quality. As the health benefits of drinking tea become more firmly established the Australian tea industry also needs data to assist with effectively promoting its tea as overseas tea companies are already doing with their tea. The production line and relevant technology for the processing of black tea in Australia have been modified from those currently employed in other tea producing countries. Thus, it is necessary to understand the changes in chemical composition occurring during the growing and processing of Australian tea, if quality improvements in tea are to be achieved. However, no published data are available relating the chemical composition, including phenolic compounds, to the growing and processing of Australian tea. Therefore, an investigation into the types and contents of flavonoids and other polyphenols in Australian grown tea at various growing seasons and made tea during different processing steps was carried out to provide the Australian tea industry with information to assist with maximising the quality of its black tea. Areas where quality could be improved were also identified. This project was funded from RIRDC Core Funds which are provided by the Australian Government. This report is an addition to RIRDC’s diverse range of over 1000 research publications, forms part of our New Plants Products R&D program, which aims to to facilitate the development of new industries based on plants or plant products that have commercial potential for Australia. Most of our publications are available for viewing, downloading or purchasing online through our website: • downloads at www.rirdc.gov.au/fullreports/index.htm • purchases at www.rirdc.gov.au/eshop Simon Hearn Managing Director Rural Industries Research and Development Corporation iii Acknowledgments We would like to express our sincere thanks and appreciation to the following: • Mr Bill Benson (General Manager and Director), Mr Tony Santarossa (Field and Workshop Manager) and Mr Tony Poyner (Factory Manager) of Glen Allyn Tea Estates, Malanda, North Queensland for providing the tea samples that enabled this work to be done and for all their help and advice throughout this study. • Mr Andrew Weavers (General Manager) and Mr Peter Jeffery (Operations Manager) of Nerada Tea Pty. Ltd. (Brisbane) for their assistance throughout this study. • Mr Masayuki Suzuki and Mr Kazuaki Kida of Tokyo Food Techn Co. Ltd. (Mitsui Norin Co. Ltd.), Japan; Dr Jun Kato of Hokkaido Central Agricultural Experiment Station, Japan and Mr Xu Liu of Tea Research Institute, Hangzhou, China, for providing some of the tea standard compounds for this study. • Mr Graham Kerven (Manger of Analytical Services of the School of Land and Food Sciences) and Miss Katherine Raymont for their technical assistance and Mr Alan Lisle for his assistance with the statistical analysis of the data. iv Contents Foreword iii Acknowledgments iv List of tables viii Abbreviations xi Executive summary xiii 1 Introduction 1 1.1 Tea flavonoids 1 1.2 Aim and objectives of this project 2 2 Literature review 3 2.1 Flavonoids 3 2.2 Tea 11 2.3 Summary 33 3 Agronomic aspects of the tea farm and the on-site processing of black tea 34 3.1 Introduction 34 3.2 Tea farm 34 3.3 Weather data 36 3.4 Tea factory at Glen Allyn Tea Estate 37 3.5 Conclusions 40 4 Methodology for the analysis of flavonoids and other polyphenols in Australian tea 41 4.1 Measuring phenolic compounds in teas from Australian markets 41 4.2 Development of methods for the analysis of flavonoids and other polyphenols in Australian tea 43 4.3 Analysis of flavonoids and other phenolic compounds in fresh Australian grown tea leaves 51 4.4 In-line analysis of flavonoids and other polyphenols during the processing of Australian black tea 56 4.5 Development of an on-line method for assessing optimum fermentation of black tea 62 5 Results and discussion 64 5.1 Measuring phenolic compounds in teas from Australian markets 64 5.2 Development of methods for the analysis of flavonoids and other polyphenols in Australian tea 68 5.3 Analysis of flavonoids and other phenolic compounds in fresh Australian grown tea leaves 82 5.4 In-line analysis of flavonoids and other polyphenols during the processing of Australian black tea 118 5.5 Development of an on-line method for assessing optimum fermentation of black tea 151 6 Summary, conclusions and recommendations 157 6.1 Summary 157 6.2 Main findings and conclusions 158 6.3 Recommendations for further work 160 7 Implications and intellectual property 161 8 Publications from project 162 9 Appendix 163 10 References 166 v List of figures Figure 2.1 Structure and dietary occurrence of the main classes of flavonoids 4 Figure 2.2 Structure of EC, ECG, EGC and EGCG. 8 Figure 2.3 Structures of tea catechins. 23 Figure 2.4 Structures of representative phenolic acids and flavonol glycosides in tea 24 Figure 2.5 Structure of four major theaflavins in black tea. 26 Figure 2.6 Structures of some nitrogenous tea phytochemicals 32 Figure 3.1 Tea Farms in North Queensland, Australia. 35 Figure 3.2 Processing flow of the black tea manufacture at the Glen Allyn Tea Estates. 39 Figure 4.1 Sampling points on the black tea processing line at the factory of Glen Allyn Tea Estates, Malanda, North Queensland 59 Figure 5.1 Comparison of Total Polyphenol Content of Black Tea 64 Figure 5.2 HPLC chromatogram of Australian grown fresh green tea leaves monitored at 280 nm (eluted in the first 40 minutes). 68 Figure 5.3 PDA UV spectrum of theogallin. 69 Figure 5.4 Photodiode array UV spectrum of theobromine. 70 Figure 5.5 Photodiode array UV spectra of quinic acid derivatives. 71 Figure 5.6 Photodiode array UV spectra of the principal green tea polyphenol 72 Figure 5.7 Photodiode array UV spectra of the flavonol glycosides. 74 Figure 5.8 HPLC chromatogram of an Australian black tea liquor monitored at 280 nm. Mobile phase. 75 Figure 5.9 The superimposed photodiode array UV/VIS spectra of the four theaflavins in Australian black tea. 75 Figure 5.10 A seasonal variation of EGCG in hand plucked tea leaves. 88 Figure 5.11 A seasonal variation of ECG in hand plucked tea leaves. 90 Figure 5.12 A seasonal variation of EGC in hand plucked tea leaves. 91 Figure 5.13 A seasonal variation of total catechins in hand plucked tea leaves. 93 Figure 5.14 A seasonal variation of total catechin gallates in hand plucked tea leaves. 94 Figure 5.15 A seasonal variation of the combined catechins and catechin gallates in hand plucked tea leaves. 95 Figure 5.16 A seasonal variation of total phenolic compounds in hand plucked tea leaves. 96 Figure 5.17 A seasonal variation of EGCG in mechanically harvested green leaves. 98 Figure 5.18 A seasonal variation of ECG in mechanically harvested tea leaves. 99 Figure 5.19 A seasonal variation of EGC in mechanically harvested tea leaves. 100 Figure 5.20 A seasonal variation of total catechins in mechanically harvested green leaves. 101 Figure 5.21 A seasonal variation of total catechin gallates in mechanically harvested tea leaves. 103 vi Figure 5.22 A seasonal variation of combined catechins/catechin gallates in mechanically harvested tea leaves. 104 Figure 5.23 A seasonal variation of total phenolic compounds in mechanically harvested tea leaves. 105 Figure 5.24 Comparison of seasonal variations of EGCG in hand plucked (Field) and mechanically harvested (Bin) tea leaves. 107 Figure 5.25 Comparison of seasonal variations of ECG in hand plucked (Field) and mechanically harvested (Bin) tea leaves.