I am thinking of baking biscuits for presents for Christmas.
However, the recipe calls for baking soda, and I cook from scratch fairly rarely, so I'm worried the leftover bicarb will go strange in my cupboard. And since people use it for all sorts of purposes, it's one of those products generally not available in the small quantities called for in cooking.
If I do buy a packet, how long is an expected shelf-life for it? Based on this question I probably should find an airtight container to store it in, which may assist.
(Note if relevant: I live in Sydney Australia; Christmas here is mid-summer, and often fairly high-humidity and 35-40 degree C heat.)