Just a few extra thoughts. Some traditional foods have much symbolical suginficance, and even though they are time-consuming to prepare, the knowledge of how to cook them remains, because they cooked at special times of year - maybe Christmas among christians, and certainly throughout the month of Ramadan among muslims. So it is important to keep those traditions alive.
I think what is really at risk of being lost - knowledge which may become important again if climate change adaptation becomes of especial importance in the future - is knowledge of wild foods and of famine foods, and of food which grows in semi-arid environments. This kind of knowledge probably needs to be recorded in cheap reference guide-books, with drawing or photos of the relevant plants, the kind of habitat where they may be found, and the method of gathering and preparation.
We also need to be aware of the high diversity of land-races (locally bred food varieties) at risk of being lost. I read a PhD some years ago which recorded biodiversity on the farms of wealthier and poorer farmers around Mount Kenya. Poorer farmers kept a much wider range of land-races going than did richer farmers (sub-varieties adapted to particular conditions in particular bits of the farm). Richer farmers tended to buy standard seeds from the market and to grow more commercial crops and fewer subsistence varieties. These land-races are traditional foods very much under threat from Monsanto et al.
Dr. Gill Shepherd