textField : stringDefault: 'text'

    
 <select id="dropdown" width="200"></select>
 <script>
     $('#dropdown').dropdown({
         textField: 'newTextField',
         dataSource: [ { value: 1, newTextField: 'One' }, { value: 2, newTextField: 'Two' }, { value: 3, newTextField: 'Three' } ]
     });
 </script>