Bundling and minification are two techniques you can use to improve request load time.
Bundling and minification are enabled or disabled by default by setting to true or false the Compilation element.
To change this behavior use the BundleTable.EnableOptimizations property and set to true to enable bundling and minification.
You can use any logic you want or, for a simple scenario, use a app settings key.
BundleTable.EnableOptimizations = bool.Parse(System.Configuration.ConfigurationManager.AppSettings["EnableOptimizations"]);
Place this code in your BundleConfig class inside method RegisterBundles.