“…Besides protein nitrogen (PN), NPN represents an important fraction in product that determines protein quality (Periago, Ros, Martinez, & Rincon, 1996). The NPN involves a wide group of components, including urea, ammonium salts, single amino acids, small peptides, amines, amides and nucleotides (Goedhart & Bindels, 1994) and all of them end in ammonium as the final chemical form. Conesa, Periago, Ros, and Lopez (2005) noted that industrial processing such as severe heating (>70 C) led to a significant increase in NPN (P 0.01).…”