Thiol containing compounds as controlling agents of enzymatic browning in some apple products

A comparative study concerning the inhibition of the enzymatic browning in Red delicious apple slices and pulp stored for 24 h at 4, 25, and 35 °C was carried out between the thiol containing compounds; cysteine, glutathione and Maillard reaction products (MRPs) derived by heating aqueous solutions containing cysteine with glucose or ribose (Cys/G or Cys/R) and those commercially applied such as: sodium metabisulfite, ascorbic acid and 4-hexyl resorcinol. The efficiency of all antibrowning agents was followed in terms of absorbance and colour measurements. The obtained results confirmed the presence of a proportional relation between the concentration of antibrowning agents and their inhibitory effect, whereas the increase in storage temperatures showed an opposite trend. The inhibitory effect of the thiol containing compounds was comparable with 4-hexyl resorcinol and being significantly (P < 0.05) higher than ascorbic acid under all experimental conditions. The MRPs derived from cysteine/glucose model system were more active than their counterpart derived from cysteine/ribose model system. However, each of them could be considered as potential natural inhibitor having technological and commercial benefits to be applied in processed fruits.