Clearing md-radio-button selections in Angular 2 App

I have a sorting filter set up on my Angular app, that uses radio buttons via md-radio-group so that users can choose a preferred sorting method on a table display of data. The radio buttons are working as expected. However, I also have a "Restore Defaults" button that I want to use to clear all radio-button selections and return to default sorting. So far I'm having difficulty getting the radio buttons to clear.

This is what my view code looks like:

    <filter-option name="Sort"
            placeholder="Select Sorting Option"
            [usePlaceholder]="!value"
            [visible]="sortFilters.enabled">
        <filter-label>{{value | capitalize}}</filter-label>
        <filter-menu>
            <md-radio-group class="mat-radio-label-content">
                <md-radio-button value="alphabetical" class="vert-radiobox-list" (click)="onSortClicked(value = 'alphabetical')">
                    Alphabetical
                </md-radio-button>
                <md-radio-button value="reverse alphabetical" class="vert-radiobox-list" (click)="onSortClicked(value = 'reverse alphabetical')">
                    Reverse Alphabetical
                </md-radio-button>
                <md-radio-button value="numeric ID" class="vert-radiobox-list" (click)="onSortClicked(value = 'numeric ID')">
                    Numeric ID
                </md-radio-button>
            </md-radio-group>
            <button md-button class="restore-button" (click)="clearSortingFilters()">Restore Defaults</button>
        </filter-menu>
    </filter-option>

In my component I have this that initializes the filter:

sortFilters =
{
    enabled: true,
    value: false
};

And this is the function attached to the button to clear the sort filters:

clearSortingFilters()
{
    this.sendSort.emit(this.value = '');
}

Now, in the above function, this.sendSort.emit(this.value = '') accomplishes clearing the selection that was showing in the filter-label area. But how do I clear the md-radio-group radio button selections as well?