you can write the orientation property to cover the original one
[imagePropertiesDictionary setObject:[NSNumber numberWithInt:orientation] forKey:@"Orientation"];
but make sure imagePropertiesDictionary is NSMutableDictionary
// case UIDeviceOrientationLandscapeLeft: return 1; // Top, left
// case UIDeviceOrientationPortrait: return 6; // Right, top
// case UIDeviceOrientationLandscapeRight: return 3; // Bottom, right
// case UIDeviceOrientationPortraitUpsideDown: return 8; // Left, bottom