Delaying Enzymatic Browning Reaction in Gala Apples


  • Joy Du
  • Gary H.
  • Katherine L.


When an apple is injured (or cut into pieces), the plant tissue is exposed to oxygen. This
triggers an enzyme known as polyphenol oxidase (PPO) to oxidize polyphenols in the apple’s
flesh (Deutch 80). This produces new chemicals (o-quinones), which then react with amino
acids to produce brown-colored melanins. The objective of this work was to test what treatments
were effective in slowing down the enzymatic reaction and browning in gala apple slices. The
measured data was collected by comparing the color of the treated apple slices after 60 hours.
To quantify the colouring and browning of the apples, each slice was compared to an apple
browning scale by Van Cleve. The slices which take longer to turn brown were deemed a more
effective treatment at slowing down the enzymatic browning reaction. This paper tested how
some common household solutions, such as carbonated water, lemon juice, vinegar, saltwater,
rubber bands, and plastic wrap, could slow down the enzymatic process and oxidation in
apples. The results confirmed the hypothesis that if apple slices are soaked in saltwater, then
there will be less browning in comparison to other treatments. There was less browning in the
slices treated with saltwater due to the chloride ions which inhibit the polyphenol oxidase (PPO)
enzymes (Zhang and Liang).