Jackrabbit OAK and plain/text

[Yuri Simione]

Hello to everybody.

I am trying to index nt:file instances with plain/text mime type but it seems 
that standard lucene index does not index this file type; I tried to create a 
custom Lucene index configuration with a tika a different configuration files 
(one of these, below) but it did not work.

<properties>
  <parsers>
    <parser class="org.apache.tika.parser.defaultParser">
     <mime>text/plain</mime>
    </parser>  
    <parser class="org.apache.tika.parser.EmptyParser">
      <!--<mime>application/pdf</mime>-->
      
<mime>application/vnd.openxmlformats-officedocument.spreadsheetml.sheet</mime>
      <mime>application/vnd.ms-excel.sheet.macroenabled.12</mime>
      
<mime>application/vnd.openxmlformats-officedocument.spreadsheetml.template</mime>
      <mime>application/vnd.ms-excel.template.macroenabled.12</mime>
      <mime>application/vnd.ms-excel.addin.macroenabled.12</mime>
      <mime>application/vnd.ms-excel</mime>
      <mime>application/vnd.ms-excel.sheet.binary.macroenabled.12</mime>
    </parser>
  </parsers>
</properties>

How can Lucene indexes .txt files in a Oak 1.42.0 /Sling 12 instance?

Thanks in advance.
Yuri Simione