Effectiveness of some crown compounds on inhibition of polyphenoloxidase in model systems and in apple

Enzymatic browning is (in most cases) an undesirable reaction which usually impairs the sensory properties and chemical changes in raw fruits and vege tables after mechanical operations (such as peeling, coring or slicing). A great emphasis is put on research to develop new methods to prevent enzym atic browning especially in fresh-cut (minimally processed) fruits and vege tables. The inhibition effect of crown compounds, macrocyclic ethers, benzo-18-crow n-6 with sorbic acid and benzo-18-crown-6 with potassium sorbate, on polyph enoloxidase (PPO) activity was studied. The effectiveness of these compound s was evaluated by using 3,4-dihydroxy phenylalanine (L-DOPA), and chloroge nic acid (3-o-caffeoyl-D-quinic acid), the most widespread natural PPO subs trates in fruits and vegetables, as well as browning inhibition substances on the cut surface of apples. Results showed that crown compounds used in this study were effective, both as inhibitors of the oxidation of phenolic compounds (PPO substrates) in m odel solutions and as inhibitors of enzyme discolorations of real systems ( fresh-cut apples). In the earlier published papers (VUKOVIC et al., 1999) the synthesis of cro wn compound used in this study was presented.