On Ultrasphinx Associations

I am new to ultrasphinx and I am struggling with this issue.

I ve got a model with the following associations and is_indexed

class Item
has_many :keywords

is_indexed :fields => [‘id’, ‘collection_id’,‘subject_area’,
‘special_interest’, ‘notes’, ‘abstract’],
:concatenate => [{:association_name => ‘keywords’, :field =>
‘keyword’, :as => ‘keyword_text’}]

When I try this in the console:

@b=Ultrasphinx::Search.new(:query => “Immoral behavior”).run.results

I get 5 objects back, they do so because I know they match one of the
keywords in the :keywords assocations

[#<Item id: 329, collection_id: 117, notes: “”, size_scope: “25
items”, special_interest: “”, subject_area: “WIH”, abstract: “While
Evaline (Eva) Foster was in Malaysia from 189…”>,
#<Item id: 308, collection_id: 137, notes: “This letter originated
from: Crittenden Family Pape…”, size_scope: “16 pages”,
special_interest: “”, subject_area: “WIH”, abstract: “While his wife,
Clara Jones Crittenden, stayed with…”>, #<Item id: 1214,
collection_id: 110, notes: “”, size_scope: “35 letters
(approximately)”, special_interest: “”, subject_area: “A-A”, abstract:
“Of the Fenno-Hoffman Family papers, the letters wri…”>,
#<Item id: 271, collection_id: 319, notes: “M-3462.2”, size_scope: “1
page”, special_interest: “”, subject_area: “WIH”, abstract: “Joseph F.
Huntoon wrote this letter to his wife, Be…”>,
#<Item id: 1207, collection_id: 2, notes: “”, size_scope: “3 pages”,
special_interest: “”, subject_area: “A-A”, abstract: “Letter from
Oliver Swaine Taylor to an unidentified…”>]

The problem is that in the fields retrieved in each object I don’t see
the one I specified in the : concatenate options named ‘keyword_text’
which is the one causing the matching.

Any help on how I can have access to those fields?