Browning - D Y Patil DHTS

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Transcript Browning - D Y Patil DHTS

Browning
Compiled by:
Mrs. Vandana Mahajani
What is browning?
Browning is a common colour change seen
in food during prepreperation, processing
or storage of food.
 Colour may range from cream or pale
yellow to brown and black.
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Browning –desirable or undesirable
In some cases the brown colour may add
to aroma ,flavour and colour as brown
crust of bread, roasted nuts, coffee beans
, caramel peanut brittle etc.
 Undesirable effects are seen in milk,
cream, eggs dry fruits, coconut,citrus
fruits and canned juice concentrates and
milk
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Types of browning
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Enzymatic browning occurs in fruits when cells
are disturbed when cut or bruised. This is due to
the oxidative enzymes present on phenolic
substances present in plant tissues.
Eg. Apples, brinjals, bananas, pears and potatoes
Phenolic compounds------oxygen---------Quonines
Enzymatic browning reaction
Prevention of EB
-by inactivating enzymes by heat, salt, ph levels,
and low temp.
-by avoiding contact with oxygen
Non enzymatic browning
Maillard was the first tp observe browning . The
reaction is also called protein sugar reaction.
 Conditions favouring millard reaction
 High temperature
 Increase in alkalinity
 Concentration and type of amino acid and sugar
present (lysine and glucose)
 Presence of catalyst (such as copper and iron)
 Desirable changes are seen as in roasting of
coffee beans and nuts and quality of baking bread
 Undesirable changes like off-odour, off-colour ,
off-flavour can be prevented by low temp and low
ph.
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Caramalization
Sugars are caramalized at 163 deg C to
170 deg C.
 This reaction occurs in sugar alone.
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high temp
Sucrose---------------------------------------caramel * acid
decomposition
dehydration
polymerization
Ascorbic acid browning and lipid browning
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Ascorbic acid browning occurs in strawberry and cocum
where original red colour changes to brown. The
ascorbic acid present in these fruits undergoes oxidation
causing browning.
Lime juice cordial and other preserves see this kind of
browning.
Lipid browning occurs when amino acids present in fats
react with aldehydes and reducing sugars causing
browning.
It is an undesirable reaction
Role of browning in food preperation
All browning reactions can be controlled.
 Enzymatic browning is undesirable especially in
cut fruits and salads.
 Natural browning during preparation of food is
desirable.
 Brown colour, aroma and right texture imparted
to food while browning occurs, is desirable.
 Detrimental effects of browning
. Poor colour.
loss of nutrients
loss of ascorbic acid.
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