Checking selected checkboxes only

I’m building a list of checkbox items like this:

      <ion-item *ngFor="let listitem of checkdetail.contents; let i=index">
        <ion-label class="mainitem" *ngIf="listitem.flavour === 'item'" text-wrap>{{listitem.content}}</ion-label>
        <ion-checkbox color="primary" checked="false" *ngIf="listitem.flavour === 'item'" [(ngModel)]="cucumber[i]" (ionChange)="updateCucumber(i)"></ion-checkbox>
        <ion-label class="subitem" *ngIf="listitem.flavour === 'subitem'" text-wrap>{{listitem.content}}</ion-label>
        <ion-checkbox color="secondary" checked="false" *ngIf="listitem.flavour === 'subitem'"></ion-checkbox>

When the items are all checked I want to detect that, so I can alter the page colour.

I can detect if they are all checked with a loop, but how can I check only the items, and not the subitems?

If these were bespoke lists it’d be fine and I’d hardcode it, but the data is pulled from an array and the pages conducted on the fly.