Let's cut right to the chase. TIP: when blogging, it's about quality NOT quantity. Don't think about it in terms of how many words. What matters, is the content within the blog. Are your readers intrigued? This food service blog post example from Eaton Marketing makes good use of keywords, pictures and has a Call-To-Action at the bottom giving the reading an opportunity to request more information.
At the end of the day, your blog posts should be as long as they need to be. It's that simple. Can you get your point across in a few hundred words? Great. But if your subject and topic requires a couple thousand words, that's fine too.
There is no policy here. You won't be penalized. Again, think about it from the readers perspective. Keep them interested. Blogging can definitely be frustrating and scary to those who are new to it. Don't be and don't worry about how many words. Just make the words you chose count.