Drying ginger And Preserving 6-gingerol Content by LiZhuo Li Supervisor: Dr Robert Driscoll Co-supervisor: Dr George Srzednicki A thesis submitted in fulfilment of the requirements for the degree of Masters by Research School of Chemical Engineering, Faculty of Engineering The University of New South Wales Sydney, Australia July 2017 ORIGINALITY STATEMENT 'I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.' Signed Date Abstract Ginger rhizome (Zingiber officinale Roscoe) is widely used as a spice or a folk medicine. 6-gingerol is the major bioactive component in fresh ginger and has numerous physiological effects. 6-gingerol is heat sensitive while cooking and drying will transform 6-gingerol to 6-shogaol. Therefore, 6-gingerol content is used to determine the quality of ginger after drying. A drying model called the Two layer model was tested for prediction of drying ginger and compared with a single layer model. In this study, two layer model was used to describe ginger drying process. 6-gingerol content was measured by using HPLC method. Several factors which could affect 6-gingerol content were reviewed and a 6-gingerol prediction model was established from the experimental data. The results showed that the two layer drying model gave no significant improvement to describing the ginger drying process compared with the single layer model. Drying time and relative humidity (ranging from 10% to 40%) impacted 6-gingerol content, although drying temperature (ranging from 30°C to 60°C) had less effects on 6-gingerol content. It was found that 6-gingerol content was highly variable in fresh ginger, which making conclusions on models difficult. Keywords: Ginger, 6-gingerol, thin layer drying, two layer model, 6-gingerol perdition Content Chapter 1 Literature Review: ......................................................................................... 1 1.1 Ginger Introduction .......................................................................................... 1 1.1.1 Background of Ginger........................................................................... 1 1.1.2 Diversity of Ginger ............................................................................... 1 1.1.3 Uses of Ginger and Relative Products .................................................. 2 1.1.4 Global Ginger Production ..................................................................... 3 1.1.5 Global Trade in Ginger ......................................................................... 3 1.2 Chemistry of Ginger......................................................................................... 5 1.2.1 Composition of Ginger.......................................................................... 5 1.2.2 Essential Oil .......................................................................................... 5 1.2.3 Gingerol and Shogaol............................................................................ 6 1.2.4 Medicinal use of Ginger........................................................................ 7 1.2.5 Pharmacological use of Ginger ............................................................. 9 1.3 Drying Theory ................................................................................................ 10 1.3.1 Purpose of Drying ............................................................................... 10 1.3.2 Drying of Ginger ................................................................................. 10 1.3.3 Thin Layer Drying .............................................................................. 11 1.3.4 The Limitation of Existing Thin Layer Drying Models ...................... 15 1.3.5 Two Layer Diffusion Model for Changed Drying Condition ............. 16 1.4 Separation and Identification Methods .......................................................... 18 1.4.1 Chemical Separation Technology ....................................................... 18 1.4.2 Chromatography.................................................................................. 18 1.4.3 Chromatography-Mass Spectrometry Method .................................... 19 1.4.4 High-Performance Liquid Chromatography Method.......................... 19 Chapter 2 Materials and Methods ................................................................................ 21 2.1 Raw materials, Chemicals and Equipment used ............................................ 21 2.2 Drying Preparation ......................................................................................... 21 2.3 Drying Procedure ........................................................................................... 22 2.4 Drying Conditions .......................................................................................... 23 2.5 Extract Preparation......................................................................................... 24 2.6 Instrumentation and Chromatographic Conditions ........................................ 24 2.7 Data Analysis Procedure ................................................................................ 25 Chapter 3 Results and Discussion ................................................................................ 26 3.1 Individual Model Fitting ................................................................................ 26 3.2 Global Model Fitting...................................................................................... 27 3.3 HPLC Analysis of 6-gingerol Content and Predictive Modelling ................. 28 3.3.1 6-gingerol Content .............................................................................. 28 3.3.2 6-gingerol Predicting Model ............................................................... 33 3.3.3 Humidity Effect on 6-gingerol Preservation ....................................... 35 3.4 Optimum Drying Condition ........................................................................... 36 Chapter 4 Conclusion ................................................................................................... 38 Bibliography ................................................................................................................ 39 Appendix ...................................................................................................................... 45 Acknowledgements I am indebted to Dr Robert Driscoll and Dr George Srzednicki for their support during whole experiment and thesis writing period, to Ms Kitty Tang for her support in the HPLC analysis. Ginger supply supports by Mrs Pam Fielder from Buderim Ginger in Yandina Qld. Laboratory support by the School of Chemical Engineering are gratefully acknowledged. Chapter 1 Literature Review: 1.1 Ginger Introduction 1.1.1 Background of Ginger Ginger is a kind of universal spice which is widely cultivated and used in the world, particularly in Asia for example China and India. Ginger is consumed in various forms. In Asia, it is normally used in cooking as a spice, while ginger drinks, ginger oil, as well as dried ginger products are sold on the market in Europe and America. Ginger root is used as a tonic to treat common ailments in India and ancient China. Ginger, also named as Zingiber Officinale Rosc, is classified as a member of the tropical and sub-tropical family Zingiberaceae, and originated in tropical rainforests in southern Asia before spreading to Mediterranean regions by the 1st century. In ancient Rome, ginger was a popular spice used to make delicacies (sweets) in medieval times. Throughout the history of global trade, ginger has been traded longer than most other spices. It was regarded as a costly herb for its medicinal merits and nutritional value in the ancient world, and in the14th century, it cost the same as a piece of livestock (Katie, P. 2011). 1.1.2 Diversity of Ginger Over the long history of ginger trading around the world, ginger has been planted on almost all of the continents. Given different growing environment, ginger has developed into several species. Table 1 lists some important ginger species in the business market (Kizhakkayil et al, 2011). In business trading, the product ginger often being marked by the country where it is from, such as Chinese ginger, Indian ginger, Australian ginger and Jamaican ginger (Pakrashi & Pakrashi, 2003). However, ginger actually has an even more extensive cultivar diversity, so that even in a country, there could be dozens of cultivars. Generally, one cultivar often comes from a specific growing place, and so people have often named the growing place of the ginger before the cultivar to distinguish different cultivars (Ravindran & Babu, 2005). 1 Table 1. Some of the economically important Zingiber species (Kizhakkayil et al 2011). Species/subspecies Occurrence Use Z. officinale Roscoe Tropical countries, China, USA Spice, condiment, medicinal Z. officinale