Hard liquors are distilled beverages from weaker fermentation broths containing less than 15% alcohol as further concentration cannot be achieved during yeast fermentation because of the inability of the microorganism to survive at higher alcohol levels. Only Beer and Wine are the major non-distilled beverages while the commonly known "Spirits" like Brandy, Gin, Rum, Tequila, Vodka and Whiskey have alcohol levels above 20%. Liqueurs are spirits with added sugar and flavorings. Distillation is a process known to mankind since second millennium and modern technology for efficient distillation has its origin in the 8th century.
Gin is a distilled alcohol beverage obtained mostly from neutral spirits derived from agricultural sources by yeast fermentation. Traditionally neutral alcohol is re-distilled after mixing with Juniper berries under ambient conditions. Over the years several changes have taken place in modifying the flavor of gin and to day there are gin products made with not only juniper berries but also with other aromatic ingredients like lemon, bitter orange peel, lime peel, grapefruit peel, coriander, nutmeg, cassia bark etc. In contrast cheap variety of gin is made by blending neutral alcohol with essences to resemble natural gin. Innovations so far were restricted to flavoring of gin but technology of making the product also has been improved to make a better quality product.
It was In 2007 that a patent was filed for a practical industrial method under which high quality product was obtained by distillation under sub-freezing temperatures. Unlike the traditional distillation, the new method was claimed to be able to produce gin with an aroma much closer to that of the original infusion of juniper, coriander, citrus peels and other botanicals with which gins are flavored. The liquor giant Bacardi started selling an English gin called Oxley that is distilled at a temperature around minus 4C which contains fresh citrus peels instead of the usual dried peels and the product is claimed to be much superior to industry standards with impressively intense, bright, almost sharp aroma. Though the precise information about this technology is not available due to patent protection, it is presumed to be a variant of the freeze distillation process known for a long time. When a blend of alcohol and water is frozen the material which freezes first is a dilute solution of alcohol in water. The liquid left behind is richer in alcohol. Freeze distillation enriches a solution by partially freezing and removing the frozen fraction that is poorer in dissolved material than the liquid left behind.
It is understandable that under low temperature conditions chemical reaction is extremely slow and most of the aroma chemicals, being aldehydes,can get oxidized under conditions when temperatures can reach 100C. Distillation under freezing conditions when the alcohol is still in liquid phase can confer distinct advantages in terms of aroma preservation. What is not known from the bare details of the process contained in the patent document, is whether the process is capable of reducing toxic artifacts of fermentation like methanol, fusel oil etc. In conventional distillation the distillate contains mostly alcohol and some flavoring substances from the base raw material used as sugar source. If the new process is superior to the thermal distillation process, it is possible that distillation under freezing temperature can improve the quality of other distilled beverages also such as brandy and whiskey.