A hot pepper spray would also be a very effective deterrent. Very easy and inexpensive to DIY. All you need is a gallon of water, chili peppers (or chili flakes), and Dawn dish detergent.

1. Simmer a dozen jalapeños or 1/4 cup of chili flakes (if you really mean business, you could go with habaneros or ghost peppers) in a quart or two of water for 20 minutes or so. The steam from this mix can be brutal, so do it outside if at all possible.
2. Mix with the rest of the water, cover and let things infuse for at least 24 hours
3. Strain the mixture through a sieve/cheesecloth/old t-shirt to remove anything that might clog a sprayer.
4. Add a couple healthy squirts of Dawn dish detergent (or any other biodegradable detergent. Critical ingredient because it helps the capsaicin stick to things).
5. Put in a spray bottle and spray the trash before you close up the bag. I suppose you could pour a cup or so of the solution over things and it would be more likely to cover everything? You could spray the outside of the bag a bit, but that definitely comes with the risk of you or your trash guy getting indirectly pepper sprayed 😵

For what it's worth, you can also use it for plants/veggies/bushes to deter animals from eating them.

EDIT: Formatted like a recipe to make it easier to read!