Industrial multi-shot gin manufacture : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Chemical and Bioprocess Engineering at Massey University, Manawatu, New Zealand

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This study investigates whether a concentrated gin ‘hotshot’ could be developed to increase production efficiency and still output. This concentrated ‘hotshot’ would also decrease transport costs and be later diluted to final strength. This ‘hotshot’ must have the same characteristics as the original gin once diluted with water and ethanol but, after distillation should be far more concentrated in flavour compounds. Recent literature published at the end of this study call this technique multi-shot gin. Since this was found at the end of this project the title and aim were renamed from gin ‘hotshot’ to ‘multi-shot’ gin to match industry standard. There are many different gas chromatography (GC) methods to analyse the volatile organic compounds (VOC) present in gin samples. An analytical method was developed to analyse the VOC via gas chromatography – flame ionization detector (GC-FID) and gas chromatography – mass spectrometry (GC-MS). This method utilised both internal and external standardisation techniques to determine the concentration of the key analytes within the gin. Out of the tested solvents, chloroform, hexane, dichloromethane and dimethyl sulfoxide it was found that hexane produced the highest extraction yield for the key analytes of interest. The highest yield was found using 1 mL of hexane to 3 mL of gin sample and extracted by gently agitating for 17 hours. GC-MS analysis was performed to identify 28 total volatile organic compounds within the gin. The key compounds of interest were found to be α-pinene, β-myrcene, limonene, γ-terpinene, and citronellal and their concentration in the original gin specimen was found to be 116 ± 5 mg/L, 57 ± 3 mg/L, 18 ± 1 mg/L, 8 ± 1 mg/L and 23 ± 1 mg/L respectively. During gin manufacture the complex flavour extraction process can be broken down into several smaller micro-processes that were focused on in this study: maceration, macerate distillation, condensed vapour percolation and vapour infusion. Analyte extraction parameters were investigated and as the botanical ratio increased, the concentration of the analytes in the distillate increased but with gradually declining effectiveness for maceration and the condensed vapour percolation. Vapour infusion had not yet reached the threshold of declining returns. The results from the research conducted for this project show that a concentrated ‘hotshot’ is possible. Vapour infusion was found to be the most efficient extraction process and can be combined with macerate distillation for a hybrid method to maximise analyte extraction.
Gin, Gas chromatography, Volatile organic compounds, Multi-shot, Distillation