Effects of thiols on browning reactions and antioxidant activity of potato

In this study, fresh-cut potatoes were treated with different concentrations (%0,5; %1,0; %2,0) of thiol solutions [glutathione (GSH), cysteine (CYS) and N-acetylcysteine (NAC)] and stored for 48 hours at room temperature. The effects of thiols on the enzymatic browning reaction which occured during the storage were examined. Potassium metabisulphite (%1,0) was used to compare effectiveness of thiol compounds. In addition, thiol-treated potatoes were deep fried for 6 minutes at 180oC and the effect of heat treatment on non-enzymatic browning was determined. Color, residual thiol content, antioxidant activity, total phenolic content and ascorbic acid analysis were applied to potatoes during the storage and frying process. Moreover, polyphenol oxidase (PPO) enzyme activity of fresh-cut potatoes and acrylamide content of fried potatoes were investigated. When the results of the analysis were evaluated, the thiol solutions used in different concentrations affected the color values of the potatoes and reduced the PPO enzyme activity. The 1,0% and 2,0% of CYS (CYS1.0, CYS2.0) concentrations completely stopped the enzyme activity, but GSH treatment was not effective on preventing enzymatic browning. It was detected that the amount of residual thiol was high in the samples immersed in CYS and NAC solutions and low in GSH treated ones. Thiol solutions increased the antioxidant activity and provided significant preservation in ascorbic acid contents. Darkening of fried potatoes was prevented in CYS1.0, GSH2.0, CYS2.0 and NAC2.0 samples. During frying process, the amount of residual thiol decreased in the CYS and NAC groups, however it increased in GSH group. While the untreated control sample had very high acrylamide content, there was a 62-70% reduction in GSH2.0, CYS0.5, NAC2.0, CYS2.0 and CYS1.0 samples. In summary, this study has shown that thiol solutions can effectively protect the enzymatic browning of fresh-cut potatoes during 48 hours of storage and also increase the antioxidant activity, thiol and ascorbic acid content of the samples. In addition, it has been determined that approximately 70% reduction can be achived in acrylamide which is classified as potential carcinogen and found high amounts in fried potatoes. The most important outcome of this research is that CYS and NAC, which are commercially accessible and inexpensive, can be used as potential sulphite substitutes to prevent browning reactions in potatoes.