The potential for a novel alcoholic drink prepared from the New Zealand native plant Cordyline australis (ti kōuka)

Patel, Minaxi
Young, Owen
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Doctor of Philosophy
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Auckland University of Technology

Some New Zealand indigenous plants may offer unique qualities that can be used to secure an exclusive niche in the alcoholic drinks market in the same way that Scotch whisky and tequila are strongly identified with the country of origin, Scotland and Mexico. Tequila is a spirit distilled from a fermented agave, dry adapted lily. Agave is in the family Agavaceae, a notable New Zealand member of which is the common cabbage tree or ti kōuka (Cordyline australis). Similarly, to the agave having a fermentable core, ti kōuka has carbohydrate (inulin) content in its young stems and roots that can be hydrolysed in acidic suspensions or by enzyme hydrolysis to yield fructose. The main objective of this thesis was to systematically research the feasibility of the production of a tequila-like spirit from ti kōuka stem, profiling the chemical properties of the spirit with a view of future commercial production of an iconic New Zealand spirit. The initial stage of the thesis focused on extracting inulin from the ti kōuka stem and hydrolysing (by both acid and enzyme) it to yield reducing sugar. The sugar concentration yielded was too low (~ 10 to 15%) to be fermented and distilled economically. Rather, the ti kōuka extract was evaporated to produce flavoured products by the Maillard reaction, a reaction between amino acids and sugars. The flavoured compounds were then infused with potable ethanol. In outline, the dried stem was hydrolysed with an inulinase at 60°C for 1 hour. The pH was adjusted to 10 with sodium hydroxide and evaporated at 60°C for 65 hours. The dried extract was reconstituted with water, centrifuged and the supernatant infused with portable ethanol to yield final different concentrations of 80, 67, 57 and 50%. The ethanol treatments simultaneously extracted flavour and colour to varying degrees. Next, sugars and amino acids were analysed in the ti kōuka stems by liquid chromatography. The most abundant sugar present in the ti kōuka after inulinase hydrolysis was fructose and the dominant amino acids were arginine, leucine, lysine, and aspartic acid/aspargine and glutamic acid/glutamine. Amino acids and reducing sugar were also analysed at different stages of the spirit production. The reducing sugar content decreased during each step of the process. The relative concentrations of arginine, leucine and lysine decreased while that of aspartic and glutamic acids increased during the whole process of making the spirit. Model systems were then used to simulate the reactions taking place between the amino acids and reducing sugar present in the ti kōuka extract. The colour of the models became darker as a function of time, accumulating more brown pigment containing the flavoured compounds. Increasing the pH and concentration of the amino acids in the reaction mixture also increased the browning pigment formation. Dichloromethane and n-pentane and diethyl ether solvent extraction of the spirits and analysis of volatiles by gas chromatography- mass spectrometry revealed that the chemical profiles of the spirits were different from those of the commercial spirits, gin, tequila and whisky. Sensory evaluation was performed on four variations of the spirit, and demonstrated that the creations were consumer-acceptable. The costs and other issues involved in producing and marketing such a spirit were identified, the major selling point being geographical exclusivity.

Cordyline australis , Maillard reaction
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