Inhibition by thiol compounds of off-flavor formation in stored orange juice. 2. Effect of L-cysteine and N-acetyl-L-cysteine on p-vinylguaiacol formation

The formation of p-vinylguaiacol (PVG), a major off-flavor in citrus products, was reduced by 30-80% in model solutions of orangejuice (MOJ) and in single-strength orangejuice (SSOJ) fortifiied by L-cysteine and stored at 45 o C. The fortification by 2.5 mM N-acetyl-L-cysteine was also effective in reducing PVG content. Experiments with MOJ samples indicated that, concomitant with the inhibition of PVG formation due to the fortification by L-cysteine, vanillin production and ferulic acid degradation were accelerated. It is concluded that although off-flavors in citrus products such as PVG and 2,5-dimethyl-4-hydroxy-3(2H)-furanone are formed by different routes, their production may be reduced by a common approach, namely application of minor amounts of naturally occurring thiol compounds such as L-cysteine