Feijoa juice

omokoroa1, Apr 4, 11:55pm
ok i have peeled and juiced some feijoas......seems the juice has turned a darkish brown colour..........which is fine by me because im not goin to waste it.....the flavour is still the samejust the colour has changed but any body have any clue as to whythe juice has gone that colour??
pickles7, Apr 4, 11:59pm
mmmm dose your carrot juice stay nice and orange????
ursula4, Apr 5, 12:07am
Add a bit of lemon juice to it... like a banana
omokoroa1, Apr 5, 12:14am
pickles if i needed a sarky answer id ask
omokoroa1, Apr 5, 12:16am
Thank you Ursula ........i will definetly do that thank you again
pickles7, Apr 5, 1:14am
why would you do that????
Answer:
Apples and other produce (e.g., pears, bananas, feijoas, peaches, potatoes) contain an enzyme (called polyphenol oxidase or tyrosinase) that reacts with oxygen and iron-containing phenols that are also found in the apple. The oxidation reaction basically forms a sort of rust on the surface of the fruit. You see the browning when the fruit is cut or bruised because these actions damage the cells in the fruit, allowing oxygen in the air to react with the enzyme and other chemicals.
The reaction can be slowed or prevented by inactivating the enzyme with heat (cooking), reducing the pH on the surface of the fruit (by adding lemon juice or another acid), reducing the amount of available oxygen (by putting cut fruit under water or vacuum packing it), or by adding certain preservative chemicals (like sulfur dioxide). On the other hand, using cutlery that has some corrosion (as is seen with lower quality steel knives) can increase the rate and amount of the browning by making more iron salts available for the reaction.
omokoroa1, Apr 5, 11:55pm
ok i have peeled and juiced some feijoas.seems the juice has turned a darkish brown colour.which is fine by me because im not goin to waste it.the flavour is still the samejust the colour has changed but any body have any clue as to whythe juice has gone that colour!
pickles7, Apr 5, 11:59pm
mmmm dose your carrot juice stay nice and orange!
ursula4, Apr 6, 12:07am
Add a bit of lemon juice to it. like a banana
omokoroa1, Apr 6, 12:16am
Thank you Ursula .i will definetly do that thank you again
pickles7, Jul 22, 6:01pm
why would you do that!
Answer:
Apples and other produce (e.g., pears, bananas, feijoas, peaches, potatoes) contain an enzyme (called polyphenol oxidase or tyrosinase) that reacts with oxygen and iron-containing phenols that are also found in the apple. The oxidation reaction basically forms a sort of rust on the surface of the fruit. You see the browning when the fruit is cut or bruised because these actions damage the cells in the fruit, allowing oxygen in the air to react with the enzyme and other chemicals.
The reaction can be slowed or prevented by inactivating the enzyme with heat (cooking), reducing the pH on the surface of the fruit (by adding lemon juice or another acid), reducing the amount of available oxygen (by putting cut fruit under water or vacuum packing it), or by adding certain preservative chemicals (like sulfur dioxide). On the other hand, using cutlery that has some corrosion (as is seen with lower quality steel knives) can increase the rate and amount of the browning by making more iron salts available for the reaction.