Due to the increasing global population and climate change, new sustainable food sources are being intensively sought to replace less favorable livestock production. Especially new protein sources and their food applications are being focused on. In this paper, several selected protein sources that may have potential application in future functional foods, such as fermented foods, were examined and compared. These sources include single cell protein (SCP), Arthrospira platensis (Algae), Acheta domesticus (edible insect), potato, and rice protein. The above sources were compared to whey proteins. The parameters studied were total nutritional value, amino acid profile, fatty acid profile, the content of some elements, and the presence of toxins