Parse JSON Object in Typescript

I am new to both Angular and building services using spring boot. Hence please excuse if the question below is very simple one.

I have the following JSON response from a spring rest service. I am trying to map this service response to Angular material data table.

However, as I still new to Angular, Typescript and parsing json objects, can you please help me with pointers on how to map the json response listed below to my Interface.

JSON response

{
    "content": [
        {
            "id": "1000",
            "name": "R&D IN",
            "location": "IN",
            "costCenter": "RD-001"
        }
    ],
    "last": false,
    "totalElements": 10,
    "totalPages": 10,
    "size": 1,
    "number": 1,
    "sort": [
        {
            "direction": "ASC",
            "property": "name",
            "ignoreCase": false,
            "nullHandling": "NATIVE",
            "ascending": true,
            "descending": false
        }
    ],
    "first": false,
    "numberOfElements": 1
}

I need to map the following two attributes in the json response above -> content and totalRecords

I have the following service code in Angular

department.service.ts

getAllDepartments(filter: string, sortOrder: string, pageNumber: number, pageSize: number): Observable<DepartmentList>{

    return this.http.get<DepartmentList>(this.API_URL + '/api/department/', {
      params: new HttpParams()
          .set('filter', filter)
          .set('sort', 'name')
          .set('page', pageNumber.toString())
          .set('size', pageSize.toString())
    });
  }

department.component.ts

this.deptService.getAllDepartments(filter, sortDirection,pageIndex, pageSize)
      .pipe(
          catchError(() => of([])),
          finalize(() => this.loadingSubject.next(false)))
      .subscribe(
          departments => {
            let obj = JSON.stringify(departments);
            console.log('Department List :: ', departments);
            console.log(obj.content);
            this.departmentSubject.next(departments.content);
            this.departmentRecCount.next(departments.totalElements);
          });

However, last two lines show error in my angular. However, the code works despite the errors

Errors are seen in the below two lines -

this.departmentSubject.next(departments.content);
this.departmentRecCount.next(departments.totalElements);

Error Message - error TS2339: Property 'content' does not exist on type 'any[] | DepartmentList'. Property 'content' does not exist on type 'any[]'.

Department.model.ts

export interface DepartmentList {
    content: Department[];
    totalElements: number;
  }

  export interface Department {
    id: string;
    name: string;
    location: string;
    costCenter: string;
  }

How do I resolve the above issues.

Please excuse if this has already been explained in any other thread.