Application of an ultrasound-assisted extraction method to recover betalains and polyphenols from red beetroot waste

Abstract

Agriculture and food industries generate substantial quantities of waste material with a huge potential for bioactive ingredients to be recovered and converted into high-value chemicals. Red beetroot, known for its high content in betalains, natural red pigments, as well as polyphenols, fiber, and nitrate, is experiencing increasing demand, in particular as juice, which is leaving behind large amounts of waste. The present study focused on the recovery of betalains and polyphenols from dried whole beetroot and wet and dried beet pulp waste from the juicing industry. As part of an ultrasound-assisted extraction, ethanol/ water-based solvent mixtures were used as they were found to be more effective than single solvents. Enzyme-assisted extraction was initially examined in the case of wet pulp but was not able to retain betalains. Betalains appear to be more stable in dried pulp. Ultrasound-assisted extraction was found to be more suitable to effectively extract both betalains and polyphenols with a high bioactive yield from dried pulp. The total betalain and polyphenol profiles as well as storage stability and antioxidant capacities were evaluated over a period of four weeks after extraction from the dried waste. During the four-week storage, betalains quickly degraded at room temperature in contrast to −20 °C, whereas polyphenols and antioxidative activity were much less influenced by temperature. When compared, dried samples from the beetroot juicing industry demonstrate good betalain and polyphenol extractability; thus, these data indicate that dried beet waste can serve as a good source of betalains for the color industry and other technological sectors.