I know this is an old post but thought i would mention that since the .properties file expects a key value, you may not be able to use friendly names in this list. In order to have a friendly name displayed in the dropdown menu from the User Interface, you will also have to add the language key and a friendly display string to a language hook. this also gives you the benefit of translating the string per language.
For example, in the portal-ext.properties, if you add journal.article.types=announcements,blogs,general,news,press-release,quarterly-newsletter
then in your language hook, you'll need to add
quarterly-newsletter=Quarterly Newsletter
and then your content editors may be a bit more happy with a friendly string in the content editor dropdown and the search form dropdown.
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