This is an interesting concept from my stand-point. Interesting in that you intend to bring out some flavor profiles I hadn't considered, even for a marinade.
A few of our resident educated chefs can probably give you some better info on the actual flavor intensity you could expect, and how to go about formulating for proper acidity of the marinade, but I'll take a stab at it to get the ball rolling from my more limited marinating experience and hopefully we can get some good ideas flowing from there.
Not sure about the horseradish on pork, as it may be a bit intense for the milder pork flavor...generally considered a good condiment for certain cuts of beef. If you like it a lot and that's what's bringing up this part of your experiment, then by all means go for it. Cranberry, if not too intense with the finished product could be a very good and unique flavor for pork ribs. If it's too intense, the pork will not be the main focus, so it could throw your dining experience into a tail-spin of sorts...(the "woah, that's not what I wanted from this" expression on your face). I hadn't thought about doing this myself, so I may have missed threads using cranberry, and haven't seen it elsewhere, but there may be a recipe or two floating around somewhere that you could reference.
If you want a true marinade for the ribs, the cranberry will add some of the acidity needed, but it will depend on the particle size and overall moisture content in regards to being a viable marinade if you're considering fresh cranberries (run through a food processor, or added to a small amount of juice in a blender) . The meat needs to be completely covered in the liquid prior to cooking, or at least turned and/or brushed several times with it in order to have it evenly applied so you get an even reaction with the food (veggies can be marinated as well). If the marinade is a heavier paste (low liquid, high solids content), it may not react as quickly, and possibly not as evenly, due to the acidity being "tied-up" in more solids than free-liquids. Don't marinate for too long, as the acidity will begin to cook the meat at some point (and could result in less smoke penetration/reaction), with marinating time depending on the acid concentration (%), or pH value. Thing is, with a newly developed recipe and procedure, you won't know how long is too long to marinate, so be cautious and conservative for the best trial results. You can always go longer the next time you try it, or use several batches for the same run, with the same blend of marinade, but longer marinating time for one or two separate batches for comparison of flavor and texture after the smoke (all batches smoked at the same time). That would give you the best side-by-side comparisons.
If you used a natural cranberry juice, it should have an adequate amount of acidity (not sure what%, and that will vary depending if it's fresh-homemade, or store-bought bottled) and if you add the horseradish to the juice and let it soak for a day or so in the fridge, the horseradish will have some time to impart it's flavors into the juice (if they will react with each other, as horseradish is acidic also, if I recall), which would then allow for more flavor from the horseradish to be imparted into the the meat during marinating.
If you're wanting to use the cranberry-horseradish as a glaze, then you would apply it with a brush or spatula after the ribs have smoked awhile, but before they are completely finished cooking. This would allow the glaze to firm up while the ribs finish on open grates (with 3-2-1 or variants, apply it during the final stage).
As a finish sauce, just apply like you would for glazing, only allow just enough time for it to heat through before removing the ribs from the smoker...say 15 minutes, maybe more if you apply a very heavy/thick coating. You could also leave the sauce on the side, hot or cold, for dipping.
Add additional spices to the marinade mix per your preferences to mellow, intensify or add subtle back-ground flavors to the overall profile of the cranberry/horseradish base. Fresh minced garlic and/or (edit) onion to add some extra depth to the stronger flavors, cracked black pepper for bit of snap up front, cayenne pepper for some background heat, rosemary, sage, oregano or sweet basil to add a more earthy background, maybe some sweetness from brown sugar to mellow it all out? Just some thoughts for enhancement of the base....
Anyway, that's all the basics I can think of right now, and I'm sure I don't have them all covered. There's an art and some science behind marinating, just like there is for smoking or curing meats.
Any commercial chefs want to take it from here? (without giving up your trade secrets and recipes, of course...LOL!!!) Or, maybe someone knows of a tried and true recipe already published, similar to what Gene is looking for that could give more insight?
I'll be watching this one! Sounds like a fun ride to me, Gene!
Edited by forluvofsmoke - 4/12/12 at 8:06pm