Comparative performance of two domestic spirit stills
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The Turbo 500 still produced by imake Limited was designed to make home-distilled alcoholic beverages on a 23 L volume scale. The objectives of this study were to analyse the distillation performance of the Turbo 500 still, and to compare it with a competitor still, the essencia. The distillate fractions from the imake-recommended 60 to 65°C water outlet temperature treatment contained stable and high ethanol concentrations of around 90% (v/v), although the other distillation properties (distillation time, percent total recovery) were usually not as good as with a warmer 75 to 80°C cooling treatment. The stills performance comparison was done with a 15% ethanol wash. The essencia still generally produced distillates with lower ethanol concentrations and lower total ethanol recoveries. The essencia’s performance was more affected by the cooling treatment than that of the T500 still. The mean theoretical plates value of the T500 was 5.08, which was higher than that of the essencia still (4.92). The gas chromatograph (GC) results of the distillates fractions from a 15% synthetic wash containing seven congeners showed essencia’s recovery curves were more scattered from the ethanol recovery curve when compared with the equivalent curves of the T500 still. Ethyl acetate and acetaldehyde were better resolved than those of the other congeners by both stills. 2-Methylpropan-1-ol was be better resolved by the essencia still. The GC-mass spectrometer (GCMS) results indicated that more esters were found in essencia’s distillates from one of two fermentation recipes (Recipe B as recommended by imake). The reason for this is unknown. Sensory trials showed that, numerically, more panellists preferred the essencia distillate from Recipe B than the T500 distillate, but the difference was statistically insignificant (29 of 50, where 33 of 50 was P = 0.05). No differences were observed for Recipe A. The copper saddles (T500) and brass scourers (essencia) turned black after distillation. The results from scanning electron microscopy showed that copper, and copper and zinc (brass), became surface oxidised during distillation. Sulphur was also detected, and could be smelt after the materials were acid treated. Overall the T500 appeared to be the better still in distillation performance, but some recommendations for improvement of the T500 have been suggested.