Prevention of degradation of the natural high potency sweetener (2R,4R)-monatin in mock beverage solutions.

Exposure of the naturally-occurring sweetener monatin to light and metal ions results in loss of both parent monatin and total indole (monatin plus monatin lactone/lactam) in mock beverage solutions, with an accompanying decrease in sweetness. In this study potential protective strategies to prevent degradation were investigated. Metal ion chelating resin, or the chelators EDTA and desferrioxamine decreased monatin and indole loss for solutions kept either in darkness or exposed to light. Tannic acid and Chinese bayberry extract both afforded protection, but this did not arise from a light filtering effect. Plastics with defined absorbance characteristics provided protection with this being wavelength dependent; yellow transparent PET plastic was most effective. The contribution of these interventions (metal ion removal/binding; antioxidant; light absorption) was additive, with combinations providing the greatest protective effect against monatin and indole loss. These results indicate that it is possible to minimise monatin degradation by appropriate choices of treatments, additives and container.

Mechanisms of degradation of the natural high-potency sweetener (2R,4R)-monatin in mock beverage solutions.

The sodium, potassium, or mixed sodium/potassium salt of the naturally occurring high-potency sweetener (2R,4R)-monatin, also known by the common name arruva, degrades over time in model beverage solutions in the presence of light. By use of UHPLC, LC-MS/MS, and peroxide assays, it has been demonstrated that degradation is accelerated by UV/visible light and the presence of trace metal ions. Data are presented that are consistent with a role for singlet oxygen (¹O2), free radicals, and peroxides (both H2O2 and organic peroxides) in monatin oxidation. Separation of degradation products by UHPLC/HPLC or LC-MS/MS provided evidence for the formation of hydroxylated and peroxide species formed on the indole ring (mass increases 16 and 32, respectively) as well as multiple ring and side-chain oxidation and scission products. Model oxidation systems using the photosensitizer Rose Bengal as a source of ¹O2 support the proposed photodegradation pathways.