Japanese brewer Asahi has launched Super Yeast Ever-Changing Draft Beer, a seasonal beer that uses two different types of yeast to offer consumers two separate tastes, depending on when they choose to drink the product.
The first bottom fermentation yeast (Asahi No. 787) is removed by filtration, and the second top fermentation yeast (Asahi No. 558) is added directly before bottling.
The second fermentation starts in the bottle during storage and distribution. For two to three months after bottling, the beer continues to ferment and its flowery, mellow flavour increases.
Most beers in Japan are launched in the summer when the heat increases consumers' thirst, but with this product, the second fermentation's optimum temperature is 10-20°C, so Asahi decided that it was better suited to the winter months.
The firm has shrink-wrapped the bottle so that consumers can view the yeast from the outside of the bottle, which has 5.5% ABV.
Continuing with the theme of yeast exploration, Asahi has also launched a four pack of 350ml beers, each containing a different yeast: 318 Yeast, used in the firm's Super Dry beer; 787 Yeast, used in Honnama Gold; 920 Yeast, featured in 2005's limited edition beer; and 111 Yeast, making its debut.
The firm runs an on-line survey updated every 30 minutes, where consumers can vote for their favourite beer.