If they were in the freezer than I would think that the patties would still be ok. A couple of years back I actually had some global patties that sat in my garage for a year. I threw them on the hives and the bees ate them just as well. Although the amino acids had probably degraded significantly, but what else was I going to do with them.
It's my understanding that the nutritional aspects can break down over time, and any patty over 2 years old is unlikely to have much benefit. I don't know how much the freezer delays the nutritional breakdown.
If you are depending on the patty to make you money, I'd get new patties. If you aren't expecting a financial return by using patties, I'd say to go ahead and use them. Might as well try to get some good out of them, rather than wasting them.
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