I would wash it in warm water with detergent and borax. Borax is a natural deodorizer that works great and will also boost laundry detergent. Hang the quilt outside even if it's cold. I find that hanging clothes out in cold weather whitens whites and the freezing does something for them, also. Bring it in and hang on a rack to finish drying. You could also add some vinegar to the rinse water.