Changes in polyphenol profile of dried apricots containing SO₂ at various concentrations during storage

Changes in polyphenols have important effects on the quality (especially color) and health benefits of dried apricots. SO₂ concentration, storage and the activities of polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were factors which had significant effects on polyphenols. Polyphenol profile and activities of PPO and PAL in sulfured dried apricots (SDAs, 0, 451, 832, 2112 and 3241 mg SO₂ kg^-1 ) were monitored during storage at 4, 20 and 30 °C for 379 days for the first time.

Even the lowest SO₂ concentration (451 mg kg^-1 ) was sufficient to inactivate PPO during the entire storage period. However, while SO₂ led to the increase in PAL activity of the samples (r = 0.767) before storage, PAL activities of SDAs decreased during storage. After 90 days of storage, PAL activity was determined in only non-sulfured dried apricots (NSDAs) and dried apricots containing 451 mg SO₂ kg^-1 . Although the major polyphenol in NSDAs was epicatechin (611.4 mg kg^-1 ), that in SDAs was chlorogenic acid (455-1508 mg kg^-1 ), followed by epicatechin (0-426.8 mg kg^-1 ), rutin (148.9-477.3 mg kg^-1 ), ferulic acid (23.3-55.3 mg kg^-1 ) and gallic acid (2.4-43.6 mg kg^-1 ). After storage at 30 °C for 379 days, the major polyphenol in SDAs was gallic acid (706-2324 mg kg^-1 ). However, the major polyphenol in NSDAs did not change after storage. The highest total polyphenol content was detected in SDAs containing 2112 mg SO₂ kg^-1 and stored at 30 °C.

To produce dried apricots having high polyphenol content, ∼2000 mg SO₂ kg^-1 should be used. Low storage temperature (<30 °C) was not necessary for the protection of polyphenols. © 2017 Society of Chemical Industry.