Naked Science Forum

Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: chris on 20/03/2015 08:13:01

Title: Why do cut avocados go brown in salads?
Post by: chris on 20/03/2015 08:13:01

Why do cut avocados go brown in salads? Is this similar to the chemistry that turns a cut mushroom a black colour?

Title: Re: Why do cut avocados go brown in salads?
Post by: evan_au on 20/03/2015 10:31:36

Cut avocados react with oxygen in the air.
Some people recommend rubbing with lemon juice to reduce the browning effect.

Title: Re: Why do cut avocados go brown in salads?
Post by: chris on 22/03/2015 22:28:05

Do you know the chemistry of the avocado browing reaction, Evan?

Title: Re: Why do cut avocados go brown in salads?
Post by: chiralSPO on 22/03/2015 22:52:47

I'm fairly certain it has to do with the oxidation of the amino acid tyrosine, which is a phenol, so it is easily oxidized. Before the avocado is opened not enough oxygen can get in to complete the reaction, but once it is exposed to the air the reaction is fairly swift. Acid can slow the reaction down (I have my theories as to why, but I am not certain, and I don't want to present misinformation...)

It's the same thing with apples, and similar with mushrooms. Some mushrooms contain hydroquinones (very similar to phenols, but more reactive) which react to turn dark blue when the mushroom is damaged (

Title: Re: Why do cut avocados go brown in salads?
Post by: evan_au on 24/03/2015 09:39:41

Browning is caused by enzymes in the fruit, when it is cut (polyphenol oxidase or PPO is one of them).
See: http://en.wikipedia.org/wiki/Browning_%28food_process%29

Or "Activity, Electrophoretic Characteristics and Heat Inactivation of Polyphenoloxidases from Apples, Avocados, Grapes, Pears and Plums"
http://www.sciencedirect.com/science/article/pii/S0023643897903029

Title: Re: Why do cut avocados go brown in salads?
Post by: chris on 26/03/2015 22:12:56

Thank you; lovely answer.