Hikashop search plug-in set searchphrase default to "Exact Phrase"

I have no problem, just a question.
I am building a new webshop for a friend, it's going well and working ok so far.
We have a search box based on Joomla standard search and Hikashop search plug-in.
It works fine, no problems so far
The default for searchphrase is "All" and we would like to have it at "Exact". We tried the usual (Joomla) way, but that did not seem to work, default stayed on "All".
Is it possible to change this searchphrase default and if so can you explain how?
Thank you very much for your help.
Cheers, André

Thanks a lot Nicolas,

I searched long, but did not come accross the override tip.
The other options is what I usually do, but this did not work in this case and I suspected that maybe the interfacing between Hika and Search might have something to do with this.
The tip from Toivo (override) works great, am very happy

Cheers,
André