Search seems to not working

in my ojs (last version, if i search by publication date or authors there is no results.
Some results are displayed only if i search with a word (or keyword) that exist in pdf text, but NOT if i search a word contained in abstract (or title).

In config.php i have this
index[application/pdf] = “path/to/pdftotext -enc UTF-8 -nopgbrk %s - | /usr/bin/tr ‘[:cntrl:]’ ’ '”

If i comment this line and run rebuildSearchIndex.php no results are displayed at all.

It seems that ojs search only in extracted pdf text and not in metadata (title, abstract, authors).

I’have no error, but only some warnings in php log.

What i can do?