Soak in cold water overnight, then rub with some good old fashioned soap. Wash in cold water. If it still doesn't work then when it is wet pour some bicarb on the stain and after 15 minutes scrape it off, wet it more and add more bicarb. Do this for an hour and then wash as normal. Or you can soak in a bucket of water with a cup of bicarb and a cup of vinegar over night and wash as normal. Apparently meat tenderiser works if in a paste but if you don't have any just use pineapple juice (dab it on) as the enzymes are similar to meat tenderiser.