Some ideas you've probably already considered:
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Nitrates and nitrites: in pretty much every commercial sausage. May be listed in the ingredients as curing salt or Prague powder.
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Onion or garlic powder
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Breadcrumbs
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Emulsifiers: in any kind of hotdog or Weiner where it's all blended and looks smooth, as opposed to a sausage where you can actually see little pieces of fat and meat. Listed in the ingredients as some kind of gum or some kind of glyceride.
The oil painting filter in gimp would do this in about one second.