Apples a chain reaction called oxidative stress. Antioxidants stop

Apples contain a variety of
phytochemicals, including quercetin, catechin, phloridzin and chlorogenic acid,
all of which are strong antioxidants which reduce free radicals in our body.1 Free radicals are highly reactive molecules
that have a deficit of electrons. These free radicals react with nearby cells
in an attempt to replace the missing electron. When the attacked molecule loses
its electron to the free radical, and becomes a free radical itself. This can
trigger a chain reaction called oxidative stress. Antioxidants stop the chain reaction leading to oxidative
stress by donating one of their electrons to the free radicals, however, the
antioxidant nutrient itself does not become a free radical on donating one
electron. Yet, in most cases these free radicals outnumber the antioxidants. As
free radicals are not only produced during all metabolic reactions, but also by
pollution, radiation, cigarette smoke, herbicides, lack of sleep and lack of
exercise, all commonalities in today’s world. Thus, we need an external source
of antioxidants to keep the free radicals in our bloodstream in check.


Vitamin C or
Ascorbic acid is a natural antioxidant which slows down the enzymatic browning
of Apple juice as it reacts with atmospheric oxygen that enters the fruit when
it is cut, and only when all the Ascorbic acid is reacted will the oxygen react
with polyphenol oxidase enzymes and cause browning to occur. Polyphenol
oxidase works best when the pH level is between 5.0 and 7.0. However, below a
pH level of 3.0, the enzyme becomes inactivated. The pH of Ascorbic Acid is
around 2.4, making it very effective against oxidation.2

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Apples (Malus
domestica) was chosen because to research on in this experiment because apple
is a very common fruit used in the food industry and is always included in our
daily diet for its high nutritional value. Moreover, apples brown rapidly after
being bruised due to their high polyphenolic compound contents. The pale
coloration of apples gives an easily observable and clear indication of the
amount of browning. Thus, qualitative observations could be made, based on the
difference in colour of apples before and after being cut and also after adding
different concentrations of ascorbic acid to it.