You can't really do this unless you build them yourself in an ng-repeat.
<select ng-model="foo">
<option ng-repeat="item in items" value="{{item.code}}">{{item.name}}</option>
</select>
BUT... it's probably not worth it. It's better to leave it function as designed and let Angular handle the inner workings. Angular uses the index this way so you can actually use an entire object as a value. So you can use a drop down binding to select a whole value rather than just a string, which is pretty awesome:
<select ng-model="foo" ng-options="item as item.name for item in items"></select>
{{foo | json}}