The default Google product feed consists of the product data from the regular X-Cart product fields displayed in the storefront. However, the Google product feed might include the information that you don't want to show in the storefront not to tire your store's customers with unnecessary details, like google_product_category.
The attributes that you don't need to show to the customers in your online store but need to submit to Google in the feed can be defined through the global attribute of a hidden field type.
To assign hidden attribute values to your products:
First, create hidden attributes as described here.
Suppose you sell cars and need to add a "google_product_category" attribute to the feed. In this case, you should use '916' as a hidden attribute value that corresponds with the "916 - Vehicles & Parts > Vehicles > Motor Vehicles > Cars, Trucks & Vans" Google product category according to Google product taxonomy.
Assign hidden attributes to your products using the Bulk Editing tool.