Identifying marker compounds for elevated storage temperature in orange juice using untargeted LC-Orbitrap analysis

• Untargeted LC Orbitrap study of marker compounds in orange juice after 40 °C storage. • Significant increase of flavonoids (Tangeretin and Nobiletin) in all sample types. • Flavonoids offer practical advantages over the established marker compounds. • Flavonoid increase correlated to the % of orange juice concentrate in the beverage. • Results advance the published mechanism for release of flavonoids during heating. In this study Untargeted LC Orbitrap analysis is used to identify marker compounds which can be used to identify when orange juice beverages have been stored at elevated temperature. Orange juice (OJ) products, with varying levels of Concentrate % and Pulp %, were held at 40 °C for one week to replicate the effects of improper storage. Using untargeted analysis, it was found that this temperature results in a significant increase of flavonoids tangeretin and nobiletin in all sample types measured. Further analysis shows that the increase in flavonoid concentration is closely correlated to the % of orange juice concentrate in the beverage. Further discussion details how these results support and enhance previous studies which have proposed a mechanism for the release of phenolic compounds during heating. It is also shown that the flavonoid compounds hesperidin and naringin did not exhibit repeatable changes following 40 °C storage, in comparison to control samples stored at 4 °C. The contrasting behaviour of hesperidin and naringin compared to tangeretin and nobiletin is also discussed. Potential benefits for using tangeretin and nobiletin as analytical markers for elevated storage temperature, along with the effectiveness of LC Orbitrap for untargeted analysis are also discussed.