Bioactive compounds of potato (Solanum tuberosum L.) juice: from industry waste to food and medical applications

Potatoes (Solanum tuberosum L.), consumed daily by millions of people around the world, are one of the most important food crops. Potato juice (PJ) is a by-product of the starch production process and contains all the constituents of potato tubers except starch and fiber. A large volume of PJ is produced annually during the starch campaign. Currently, it can, at best, serve as a source of protein for animal nutrition. The proteins are isolated using an acidification and thermal treatment, and the remaining liquid fraction is generally considered a problematic waste. Literature reports indicate that PJ is a valuable raw material not only because of its high nutritional value but, above all, due to the biological activity that can facilitate the treatment of certain gastrointestinal tract diseases. Medicinal use of PJ in folk medicine dates back to the beginning of the 19th century when it was used to alleviate the symptoms of gastrointestinal tract dysfunctions. Currently, the compounds responsible for this activity have been identified, and their mechanism of action is known. Additionally, many more compounds were found in potato which are responsible for invoking various health-benefiting effects. This manuscript provides an overview of the data published on the production of potatoes and the accompanying PJ. First, the chemical characteristics of the protein and nonprotein fractions are described together with the conventional methods for the handling of this by-product. Second, novel technologies of PJ processing are presented with emphasis on the separation of protein and its hydrolysis, and various potential applications in food technology and biotechnology. Finally third, the medical potential of PJ is reviewed. This includes antimicrobial, antioxidant, anti-inflammatory, anticancer, antiobesity, antidiabetic, antihyperlipidemic, antihypertensive activities of various constituents of the juice. The wide range of potential applications and a vast spectrum of beneficial properties make PJ a substance well worth the attention of researchers and industry.