First we need to open the Web Part Properties of your Advanced Search Web Part. Under Properties section, click on Properties (yeah quite redundant).
You should see something like this
Copy/Paste the code on an XML Formatter for easier editing (XML Formatter).
After that copy/paste the formatted XML on a Text Editor.
Under the "PropertyDefs" tag we need to defined the Managed Property we have defined on the first part. Remember that the Name for the PropertyDef should be the same with the Managed Property name we have defined.
After this you need to reference this on the Result Types
Copy/Paste the updated XML on the Properties Section of your Advanced Search Web Part.
You should now see the Product Category added on the drop down value of property restriction.
You could now use this property restriction to filter results based on a certain column.
In this intance, I have also created a Search Center to show my Result Set. I will create another topic for this.
For more information visit my blog post