Cysteine’s effects on chlorogenic acid quinone induced greening and browning: Mechanism and effect on antioxidant reducing capacity

• Published in: Food chemistry Vol. 309; p. 125697
• Main Authors: Liang, Yundi, Were, Lilian
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 30.03.2020
• Subjects: Antioxidant capacity; Antioxidants - chemistry; Benzoquinones - chemistry; Browning; Chlorogenic Acid - chemistry; Chlorogenic acid quinones; Chromatography, High Pressure Liquid; Color; Cycloaddition Reaction; Cysteine; Cysteine - chemistry; Greening; Hydrogen-Ion Concentration; Mass Spectrometry; Oxidation-Reduction; Antioxidant capacity; Greening; Browning; Cysteine; Chlorogenic acid quinones
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2019.125697

•Cysteine concentration, pH and incubation time affected color and antioxidant capacity.•Cysteine inhibited chlorogenic acid (CGA)-lysine greening primarily by reduction.•Cysteinyl thiols had a higher affinity for CGA quinones than lysyl ɛ-amines.•Lysyl amine-CGA conjugate was the main green trihydroxy benzacridine precursor ion.•The effect of CGA on CGA-amine greening and Maillard browning was decoupled. Formation of green trihydroxy benzacridine (TBA) derivatives when chlorogenic acid (CGA) quinones and amino acids react can be unappealing for some consumers. Cysteine was studied as an anti-greening strategy, given that cysteine-CGA conjugates are colorless. Buffered 2.55 mM CGA: 5.09 mM lysine: (0–5.09) mM cysteine solutions at pH 8 and 9 were prepared and incubated for a maximum of 48 h at 22 C. Color intensity and conjugate formation was monitored spectrophotometrically, and by HPLC and LC-MS respectively, while antioxidant capacity was measured by Folin-Ciolcateau and Trolox equivalent antioxidant capacity assays. Green TBA formation was promoted at higher pH and inhibited as cysteine concentration increased. Concentration-dependent cysteine inhibition of CGA-lysine greening was attributed to redox diphenol regeneration and formation of cysteinyl-CGA conjugates, which also contributed to antioxidant capacity. pH had a greater effect on antioxidant capacity than added cysteine. Results suggested a potential anti-greening approach for alkaline CGA quinone-amine greening.