Why does apple flesh turn brown

In this case, the most common problem is due to how the apples were handled in storage after being harvested. UC Davis tells us:. This makes sense to me. I bought 3 bushels of Fuji's in late September at the farmers market. They were exceptionally large the size of softballs or grapefruit , and looked and felt perfect on the outside. When you look at this photo, understand that I took this picture with 90 seconds of cutting these apples.

This is NOT due to air exposure, where apples brown after being cut and exposed to oxygen. That takes longer than a minute or due, this is how the apples look the moment they are cut open. I cut a piece of the white portion of one of these apples and tasted it. It had a mealy, mushy texture and tasted bland..

Empire and McIntosh apples and presumably, Fuji, are susceptible when they are stored for too long in cold temperatures. It looks a lot like the browning caused by CO2issues shown above , affecting the core and flesh. A key difference is there is no clear boundary between the afflicted flesh and the undamaged areas; they blend together.

U of Maine says that it occurs more frequently when the apples are harvested late for the variety and a storage compound, 1-MCP, is used. The University of Maine has a page that shows and explains several apple browning problems, including "Soggy Breakdown. Compare the CO2 issue above with ordinary browning , or "enzymatic browning.

An enzyme in the apple called polyphenol oxidase PPO starts to oxidize compounds in the apple's flesh called polyphenols. The oxidized polyphenols are transformed into "o-quinones" , which then react with amino acids in the apples to produce the brown color.

Some apple varieties have more of the enzymes and the polyphenols which means they brown more. Some new varieties have been bred to have lower levels of these compounds and stay white after cut.

The browning does not affect flavor or even texture. Sure, if you leave cut apples out for a day , that would, but that's due to actual rotting, not a simple enzymatic color change.

This enzymatic browning also occurs in other fruit, most noticeably bananas, pears and eggplants. If you want to keep enzymatic browning to a minimum, see this page for simple tips that work! At right is a photo of ordinary air-exposed browning, top a fresh cut Fuji apple and bottom the same slice, 20 minutes later. See this page for a time lapse set of photos showing how an apple slice browns once cut.

If a female apple maggot lays an egg in a growing apple, it leaves a dimple or small spot where the egg is laid.

Once the egg hatches, the maggot eats some of the apple flesh. Since the slices will float to the top of the water, place a clean paper towel on top. Once the paper towel is wet, it will push the apples under the water's surface. Another technique is to put the apple slices in zip-lock bags with the air pressed out. Neither of these techniques call for additional ingredients, and both work great for keeping the apples from browning.

Then add in the apple slices, let them soak for a few minutes, then drain them. Give the slices a quick rinse in fresh water after you drain them, so your fruit won't taste salty. Stir two tablespoons of honey into one cup of water and soak your apple slices in the mixture for 30 seconds. This works because there is a compound in honey that stops the enzyme responsible for oxidation.

O-quinones then produce the well documented brown color by reacting to form compounds with amino acids or proteins, or they self-assemble to make polymers. One question that often accompanies yours is, "Why do some apples seem to brown faster than others? Well, nearly all plant tissues contain PPO, however, the level of PPO activity and concentration of substrate--here, the phenolic compounds--can vary between varieties of fruits say, Granny Smith versus Red Delicious.

In addition, a tissue's PPO level can vary depending on growing conditions and fruit maturity. One approach the food industry employs to prevent enzymatic browning is to select fruit varieties that are less susceptible to discoloration—either due to lower PPO activity or lower substrate concentration. This approach, however, may not be practical for the home "culinary scientist.

In the home kitchen enzymatic browning can be prevented by either reducing PPO oxidation activity or lowering the amount of substrate to which the enzyme can bind. Coating freshly cut apples in sugar or syrup can reduce oxygen diffusion and thus slow the browning reaction. Lemon or pineapple juices, both of which naturally contain antioxidants, can be used to coat apple slices and slow enzymatic browning.

In addition, both fruit juices are acidic and the lower pH that they bring about causes PPO to become less active.

Heating can also be used to inactivate PPO enzymes; apples can be blanched in boiling water for four to five minutes to nearly eliminate PPO activity.