1. Hub is not a blog (its work as webpage whose name is completely unique or sub domain). So, if you want write about other topic start new hub & publish.
2. In hubpages 300-400 words necessary but if your hub is less than this range then hub unpublished for lack of content. So, if you want make your hub more searchable in google or in other gaint search engines then 600-800 words is good.
More words = More keywords = More visitor
3. If you want keep your hub high hub score then updating it regularly with latest information (but your 1st hub topic is cooking so it is difficult for updating new information) or publish more hub & interlinking them.
4. Advertise your hub in different sites through commenting, helping or other thing ( this is completely free of cost)
If you want success in hubpages then always remember " Keep Learning"