Polyphenol concentrations in apple processing by-products determined using electrospray ionization mass spectrometry

Liquid chromatography coupled with electrospray ionization and triple quadrupole mass spectrometry (ESI-MS/MS) was used to determine the concentrations of polyphenols in apple processing by-products collected from commercial juice and pie manufacturing plants. Apple pomace (cultivar Gravenstein) resulting from juice processing contained a total polyphenol concentration of 43 mg 100 g -1 dry matter (DM), and was mainly constituted of phloridzin and quercetin-3-O-galactoside. The major polyphenolic compound in apple seeds (cultivar Idared) was phloridzin (64 mg 100 g -1 DM), representing 84% of total polyphenols (76 mg 100 g -1 DM). The predominant polyphenolic compounds in apple cores (cultivar Idared) were phloridzin, chlorogenic acid, and epicatechin, which represented 77% of the total polyphenols (40 mg 100 g -1 DM). The total polyphenol concentrations in the skin of Northern Spy and Idared were 322 and 401 mg 100 g -1 , respectively. The major polyphenol sub-classes detected in apple skins were flavonols (151-154 mg 100 g -1 DM), dihydrochalcones (48-59 mg 100 g -1 DM), flavan-3-ols (32-38 mg 100 g -1 DM), phenolic acids (40-59 mg 100 g -1 DM) and anthocyanins (29-114 mg 100 g -1 DM). Key words: Malus × domestica, apple, polyphenols, flavonoids, by-products, LC-MS/MS