It is soya protein if it was the mince you used I presume.
Sorry I stand corrected it is
Quorn is made with mycoprotein, a nutritious member of the fungi family, which is naturally low in fat.
http://www.quorn.co.uk/CMSPage.aspx?ssbid=68&pid=74
It is all to do with soya and fermenting fungus
http://www.vegsoc.org/info/soya.html