Inhibition of tyrosinase-induced enzymatic browning by sulfite and natural alternatives

Enzymatic browning of fruits and vegetables and derived products is caused by the enzyme polyphenol oxidase. The anti-browning agent sulfite has been used since antiquity, but its exact mechanism remained unknown.

Promovendus TFM (Tomas) Kuijpers MSc
Promotor H (Harry) Gruppen
Copromotor JP (Jean-Paul) Vincken
Organisatie Wageningen University, Laboratory of Food Chemistry

vr 25 oktober 2013 16:00 tot 17:30

Locatie Auditorium, building number 362
Generaal Foulkesweg 1
6703 BG Wageningen
Considering their wide distribution and presumed functions in the human body, the name ‘taste receptors’ should be reconsidered. (Nature, 2012, 486, S7-S9)
Tomas F.M. Kuijpers

By using liquid chromatography coupled to mass spectrometry it is now demonstrated that sulfite has a double inhibitory effect on enzymatic browning: initially sulfite traps enzymatic reaction products by formation of colorless adducts, while at the same time the enzyme polyphenol oxidase is inactivated in a relatively slow way. This inactivation is irreversible and is based on the formation of a covalent bond between sulfite and a histidine residue in the active site of the enzyme.