Do I need to use this in half dosage since it is double action?

No. Double action means that the baking powder acts twice during the process of baking to ensure that product gets good and consistent rise.

What is the difference between ECO SUPER DA2 and SUPER PREMIUM DA2 Baking powders?

ECO SUPER DA2 is economical double action baking powder suitable for most applications. SUPER PREMIUM DA2 is high strength (over 15% CO 2 Release) double action baking powder to be used in places where consistent results and uniform rise is most important. SUPER PREMIUM DA2 is also Aluminum free.

What is the shelf life of the baking powder?

Typically, if the baking powder is stored below 21ºC it has a shelf life of about 12 months from date of manufacture. Its strength will slowly start reducing once the product nears the end of shelf life period.