It just looks like big glob of fat inside the leg where the muscles intersect. Your description made me think exactly of this.
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Oh ya, they have them and if they get into your grind if can get gamey fast.
If you handle them and then handle the rest of the meat before washing your hands you can get it on the other meat too.
There are fatty ones in the back legs, there are also tarsal glands on the lower legs, if you skin it then start butchering you can easily transfer some from those tarsal glands to the meat.
https://iamhunter.net/into-the-wild/...at-tastes-bad/
From my experience, bone-in venison (usually cut with either a handsaw or meat bandsaw) will give you a slightly gamey/off taste after about 10 months in the freezer when the marrow starts to oxidize. Bone-out is the only way to butcher in my opinion. Re: fat - there are three different types of fat on a deer - encasing hard tallow fat (the thick rind fat on the outside of the muscle) should be removed during meat prep as this type of fat will oxidize during storage and will give the meat an "old freezer burnt" taste after 10 months +. Bear meat is terrible as well if you don't trim this off. If you want to taste something really nasty, take a nice bear roast and leave the tallow fat on, then cook it after 10 months in the freezer. The inter-muscle (soft) fat and the interstitial fat (pretty much only found in the neck) should not be removed during butchering ! This is what makes your cut tender when it's cooked. This fat will not add any off taste to the meat from prolonged storage. I agree with what others posted - 2 year venison is fine to eat as long as you took care when butchering - tallow fat removed, wrapped in plastic with no air, then wrapped in waxed butcher paper. Must be kept at -18C in freezer and free from freezer wall contact (to avoid freezer burn). If you add pork fat to your grind, then make sure you eat it before 12 months or you will notice an off taste. Same with sausages if any pork meat and fat have been added.
Yes - I always put freezer goods in thick cardboard boxes so there is no chance of freezer wall contact, in addition to keeping things organized. I've never tried a vacume sealing machine due to cost and extra time involved, but it's very important to keep your wrapped meat free from air exposure. If using freezer bags for roasts or grind, I use a straw to suck air out before sealing. For steaks I usually put a tight layer of Saran Wrap on the meat. Then I wrap in waxed butcher paper and tape seal tight.