dishwasher air gap

Long time lurker here, first time posting... I'm trying to solve a smelly dishwasher problem. So far I've been focusing on the appliance itself without much success (cleaned interior and components thoroughly, checking rinse aid dispenser, changing detergent, running hot water at the sink...

When my dishwasher drains, there is a loud dishwasher drain noise. It's a gurgling sound emanating mostly from the airgap. The dishwasher drains to the airgap, which drains to a junction at the top of the disposal. Here's a YouTube link to the offending sound. At the end, I cover it to show...

Is it unnecessary to put in an air gap for a dishwasher now? Does putting a high loop in the drain tube work just as well or is an air gap better?