Base wine production
The process begins with a base wine, typically made from red grapes. The choice of grape variety depends on the producer, but many tonic wines use robust, full-bodied reds that can support the additional flavours imparted by fortification and botanicals.
The grapes are harvested, crushed, and fermented in the traditional manner. Yeast converts the sugars in the grape juice into alcohol, creating a dry or semi-sweet wine depending on when fermentation is halted.
Fortification
Once the base wine has been produced, it undergoes fortification. This involves adding a neutral spirit, such as brandy or grape spirit, to increase the alcohol content. The fortification not only raises the ABV to between 15% and 20% but also acts as a preservative, extending the wine's shelf life.
The timing of fortification can influence the final sweetness of the wine. If spirit is added before fermentation is complete, residual sugars remain, producing a sweeter product. This is often the case with tonic wine, which tends to have a rich, syrupy character.
Botanical infusion
The defining feature of tonic wine is its infusion with botanicals. Herbs, roots, and spices are steeped in the fortified wine, imparting complex flavours and aromas. The exact blend of botanicals is usually a closely guarded secret, varying from producer to producer.
Common ingredients may include gentian root, angelica, quinine, and various warming spices such as cinnamon and clove. These botanicals not only contribute to the flavour but also hark back to the drink's origins as a medicinal tonic.
Caffeine addition
Many tonic wines contain caffeine, which can be derived naturally from ingredients such as kola nut or added separately. The caffeine content gives tonic wine its stimulating quality, distinguishing it from other fortified wines.
The amount of caffeine varies by brand, and few producers publish it. Buckfast, the best-known example, declares 30 mg per 100 ml on its label: about 37.5 mg in a 125 ml glass, roughly a third of a cup of instant coffee, or about 225 mg in a 75 cl bottle, just over two cups (NHS caffeine guide). This combination of alcohol and caffeine has contributed to tonic wine's reputation as an energising drink.
Blending and maturation
After fortification and botanical infusion, the wine may be blended to achieve a consistent flavour profile. Some producers also age their tonic wine in barrels or tanks, allowing the flavours to meld and mature over time.
The final product is then filtered, bottled, and labelled. Because of the high alcohol content and sugar levels, tonic wine has a long shelf life and does not require refrigeration until opened.
Quality control
Reputable tonic wine producers adhere to strict quality control standards, ensuring consistency in flavour, alcohol content, and safety. Regulations around fortified wines vary by country, but in the UK, tonic wine must meet standards set by HM Revenue and Customs and comply with labelling requirements.