Full Idea
As Aristotle uses the term 'essence', only those properties which are mentioned in or relatively close to the starting points of the science will be essential.
Gist of Idea
Aristotelian essences are properties mentioned at the starting point of a science
Source
report of Aristotle (Posterior Analytics [c.327 BCE]) by Joan Kung - Aristotle on Essence and Explanation II
Book Reference
-: 'Philosophical Studies' [-], p.365
A Reaction
I take this to be the correct way to understand Aristotelian essence - as something understood by its role in scientific explanations. We may, of course, work back to the starting point of a science, by disentangling the mess in the middle.