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SBK3023FoodScience andNutrition
GROUP 3BROWNINGPREVENTION
NORFAZILAHBT
ZAINUL
(D20091035128)
AZIRENSANTHARAN
(D20091035141)
TUANZAKIAHBTTUAN
MAHMOOD
(D20091035112)
NURULIZZATIBT
MUSA20091035121
)
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WHY SOME
FRUITS ANDVEGETABLES TURN
BROWN WHENCUT PEELED ????
?
??
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This is due tobrowning
enzymaticreaction!!
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When fruits or vegetable
are peeled or cut,
enzymes in the plant
tissue, POLYPHENOL
OXIDASE are exposed tothe air.
In the presence of
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METHOD use to PREVENT browning enzymaticreaction..
Several methods can be applied to avoid enzymatic browning, based onINACTIVATING THE ENZYME (heat) or by REMOVING ESSENTIALCOMPONENTS (most often oxygen).
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SET A (CHANGE PH)
HERE, WE HAVE USED 3 DIFFERENT BROWNINGPREVENTING AGENT WHICH ARE LEMON JUICE,VINEGAR AND SALT SOLUTION.
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ACTIVITY:1)CUT THE LEMON AND SQUEEZE THEM
2)PREPARE THE SALT SOLUTION
3) MEASURE 20 ML OF THE LEMON JUICE, VINEGAR AND
SALT SOLUTION BY USING THE MEASURING CYLINDER.
4)PUT EACH OF THE MEASURED SOLUTION INTO 4
LABELLED BOWL A,B ,C AND D RESPECTIVELY.
5) CUT THE APPLE INTO 4 SLICE.
6)SOAK THE APPLE SLICE INTO THE 3 LABELLED BOWL
RESPECTIVELY TAKING ONE AS A CONTROL FOR 20
MINUTES.
7) TAKE OUT THE APPLE SLICE AND SEE THE TIME
TAKEN FOR IT TO TURN BROWN.
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APPLE SLICES BROWNING
PREVENTING
AGENT
COLOUR CHANGE
AFTER 1 NIGHT
A LEMON JUICE WHITEB VINEGAR BROWN
( DUE TO
DAMAGE)
C SALT WATER SLIGHTLY BROWN
D (CONTROL) - DARK BROWN
RESULTS
ACTIVITY 1
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HOW LEMON JUICE KEEP APPLE FROM
BROWNING?
Lemon juice helps keep the apple from browning, because it is full of ascorbic
acid (Vitamin C) and it has a low (acidic) pH level.
Low pH levelPolyphenol 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 lemon juice is in the 2.0 range, making it very
effective against browning.
Antioxidant
Ascorbic acid (vitamin C) acts as an antioxidant.Oxygen is more likely to react with the ascorbicacid, rather thanwith the phenolic compounds inthe fruit or vegetable.Browning does not proceeduntil most of the ascorbic acid is used up in the
reaction.
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HOW VINEGAR WORKS ON APPLE?
Like lemon juice, vinegar prevent browning of apple by loweringthe pH of the
Although vinegar can prevent the browning of
apple, but too large amount of it will cause
damage to the apple.
Why did this happen?
As vinegar undergoes the fermentation process,
it is a lot stronger when compared with lemonjuice. So, it is actually the mildness of acid in
lemon juice that is the key to prevent apples
from turning brown.
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SET 2(DEHYDRATION)
WE ARE GOING TO USE THE SALT SOLUTION OF 3 DIFFERENT
CONCENTRATION.
ACTIVITY:1)PUT THE SALT INTO A MEASURING CYLINDER UP TO 1 ML.THEN PUT 20 ML OF
WATER AND STIR THEM.
2)REPEAT STEP 2 BY REPLACING THE 1 ML LEVEL WITH 3 ML AND 6 ML.
3) PUT THE THREE SOLUTION INTO 3 DIFFERENT LABELLED BOWL.
4)CUT THE APPLE INTO 4 SLICES
5)SOAK THE APPLE SLICE INTO THE 3 LABELLED BOWL RESPECTIVELY TAKING
ONE AS A CONTROL FOR 20 MINUTES.
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HOW SALT WATER PREVENT BROWNING OF
APPLE?
The Polyphenol Oxidase enzyme needs sufficient water
to be active. Salt water will lower water activity in the
apples by adding water-binding chemicals (sodium
chloride). But dehydrating the apple, will only inhibited
the enzyme but not destroy it.
APPLE SLICES CONCENTRATION OF SALTWATER
IN 20 ml WATER
COLOUR CHANGEAFTER 1 NIGHT
A Salt(up to 1 ml of measuring
cylinder)
LIGHT BROWN
B Salt(up to 3 ml of measuringcylinder)
WHITE
C Salt(up to 6 ml of measuring
cylinder)
WHITE
D (CONTROL) - DARK BROWN
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.THE END