Error while uploading image and JSON object from Angular to Spring Boot

I am using Angular 8 and spring boot. If I upload image and object from Postman, it successfully uploads. If I try the same from Angular it fails and error is

[org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/octet-stream' not supported]

If I set headers to following in Angular

var options = { headers: new HttpHeaders().set('Content-Type', 'application/json;charset=UTF-8') };
    return this.http.patch(`${environment.apiUrl}products/`, data, options);

I still get the error

[org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/json;charset=UTF-8' not supported]

Here is the controller in Spring Boot

@PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    @PreAuthorize("hasRole('USER')")
    public ResponseEntity<?> create(
            @RequestPart(value = "file", required = false) MultipartFile file,
            @RequestPart(value = "product") @Valid ProductDTO productDTO) throws IOException

In Angular this is file upload input

<input type="file" id="file" (change)="handleFileInput($event.target.files)" accept="image/*">

In component

fileToUpload: File = null;

This is file upload function

handleFileInput(files: FileList) {
    this.fileToUpload = files.item(0);
}

In Submit method

const formData = new FormData();
    formData.append('file', this.fileToUpload);
    formData.append('product', this.form.value);

This is all happening in Angular and Spring, but in Postman it is successfully updating.

In Postman