Mint oil production: combining art and science

Dr Leo Cahill, owner of Australian Mint Oils & Flavours, says making mint oil is both an art and a science. Quality mint oil undergoes a second distillation or rectification, which requires the application of heat. However, too much heat damages the flavour and can leave burnt notes which detract from the quality of the product.

To overcome this, manufacturers can use ‘low temperature’ distillation. By employing a deep vacuum system, the distillation temperature is greatly reduced. At normal atmospheric pressure, water will evaporate as steam at 100°C; at the vacuum level employed by Australian Mint Oils, water would evaporate off at under 2–4°C. Australian Mint Oils distils at a maximum of around 50°C, which gives a high-grade quality and taste.

To achieve this quality, it is important to have a vacuum system that can control and maintain the right level of deep vacuum pressure throughout the extraction process. The vacuum pump needs to:

• pump down to the required vacuum pressure, in order to reach the desired evaporation point at each of the various stages throughout the distillation; and
• maintain the desired vacuum pressure so that the desired evaporation point is maintained.

Each system is unique, requiring specific engineering and systems design. The vacuum pump selection is also critical in terms of pump time and reliability.

Australian Mint Oils & Flavours selected a three-stage vacuum system from Swam Vacuum Systems. The SWVAS series system is a skid-mounted vacuum pump with a two-stage booster to speed up the pump downtime. The dry screw vacuum pump provides and maintains the deep vacuum pressures required.

The installation has been in production for just over 12 months and to date there has been no downtime or loss of product.