md-select component loses ng-selected value - angularjs

Question

I work with Angular 1.5.4 & material 1.0.6. Everything of the following example is working fine if I use chrome. But if I use safari no value is preselected.
The template of the component looks like
<md-select ng-model="$ctrl.selectedFruit">
<md-option ng-repeat="fruit in $ctrl.fruits" ng-value="fruit" required
ng-selected="$first" >
{{fruit.name}} {{fruit.weight}}
</md-option>
</md-select>
the component looks like
.component('applicantAccount', {
// #ngInject
bindings: {
selectedFruit: "="
},
controller: function (accountService) {
var ctrl = this;
fruitService.initFruitBefore(function () {
ctrl.fruits= fruitService.getFruits();
});
},
templateUrl: 'views/templates/selectFruitTemplate.html'
});
fruitService:
var fruits = [];
var initFruits = function () {
return $http.get(configuration.apiUrl + "fruits")
.then(function success(response) {
fruits = response.data || []
return response;
})
};
var getFruits = function () {
var filterEx = {type: "fresh"};
return $filter('filter')(fruits , filterEx);
};
var initFruitBefore = function (callback) {
if (!areFruitsAvailable()) {
initFruits().then(callback);
}
else{
callback();
}
};
var areFruitsAvailable = function () {
return typeof fruits[0] !== 'undefined'
};
var getFreshFruit = function () {
var filterEx = {type: "fresh"};
var filtered = $filter('filter')(fruits, filterEx);
return filtered[0] || null;
};
controller:
fruitService.initFruitBefore(function () {
ctrl.selectedFruit = accountService.getFreshFruit();
ctrl.fruits = accountService.getFruits();
});
The odd thing(only safari) is, that ctrl.fruits gets initialized before selectedFruit is initialized (outside of the component). If this happens the value was shown for a short term.
Has anyone an idea whats going on? Why behaves the safari different?
Thank you & sorry for my bad english
The Solution
I added ng-model-options={trackBy:'$value.id'}.
Angular Material:
To determine whether something is selected, ngModelController is looking at whether $scope.selectedUser == (any user in $scope.users);;
Javascript's == operator does not check for deep equality (ie. that all properties on the object are the same), but instead whether the objects are the same object in memory. In this case, we have two instances of identical objects, but they exist in memory as unique entities. Because of this, the select will have no value populated for a selected user.
For futher description look at https://material.angularjs.org/latest/api/directive/mdSelect