When free amines nucleophilically attack oxidized cholorogenic acid (CGA), a natural green trihydroxy benzacridine (TBA) pigment forms. Besides the loss of CGA, this oxidation induced greening can be undesirable in products such as refrigerated sunflower butter dough, as it can intensify to a deep olive-green color with time. Since thiols competitively react with oxidized CGA to lower greening in a concentration dependent manner and simultaneously increase antioxidant capacity, two thiol-containing antioxidants (cysteine and glutathione), were studied as a mitigation strategy for more aesthetically pleasing green cookies with higher antioxidant capacity. Cysteine and glutathione (0 – 5 mM) were tested in sunflower butter cookie doughs formulated with all-purpose (AP) or gluten-free (GF) flours. The doughs were stored at refrigerated temperature for 5 d. The overall surface Hunter L, a, b color changed till day 5 and then plateaued. The individual and interaction effects of time, thiol concentration, type of thiol and type of flour all significantly affected overall color change. Water activity and dough texture after 5 d were not affected by the type of thiols and flours while pH and Folin-Ciocalteau reducing capacity (FCRC) were affected. Greening in AP doughs were moderately correlated with texture, pH, and FCRC, while weakly correlated in GF doughs after 5 d storage. The results suggested that thiol-containing antioxidants can prevent the dark olive-green coloration in favor of a more pleasant green color. The simultaneously formed thiol-CGA conjugates are able to compensate for antioxidant loss in the formation of green TBA.
