2. Enzyme assisted bio-chemical process that
results in the formation of brown pigments,
hence the name enzymatic browning
Exposure to air/oxygen, warm temperature,
enzyme: phenolase, pH : 5-7
7. Phenolic substrate acted upon by the enzyme is
converted to quinones, which in turn
polymerise to form dark brown-black,
insoluble polymers called melanins
Involves a series of bio-chemical reactions
POLYPHENOL QUINONES MELANINS
8. Discolored foods are unappealing & low on
Directly affects the quality of food (Quality
Limits the shelf-life & decreases market value
of the product
Contributes to post-harvest losses
Mild heat treatment(70-100°C) for enzyme
Often used as a pre-treatment;
Types: Hot water, Steam, Microwave
11. Reduce the pH that impairs the enzyme
Enzyme activity is pH dependent
Acids like citric acid, phosphoric etc may be
12. Food subjected to ionizing radiations eg:
gamma rays, x-rays
Enzymes are inactivated
Low consumer acceptance
13. FRUITS AND
VEGETABLES SEA FOOD
During transport &
warehouse storage, F &
V subjected to
Cells are broken,
enzyme released, that
leads to browning
It contributes to post-
Also called melanosis
Common in crustaceans
Leads to discoloration
of the shell & the
Decreases the market
value of otherwise
highly prized products
14. • Major concern for developing countries
• 50% F & V wasted every year
• Losses that occur between harvest and the
moment of human consumption i.e during
handling, transport, storage etc.
15. HARVESTING & FIELD HANDLING
Harvesting should be done in cooler parts of
Harvest should be shifted to shade as early as
16. Harvested crop should reach a packing-house
Cleaning, grading, packing etc unit operations
are carried out
This concept of packing house can reduce post-
harvest losses considerably
17. Cold storage to be set up in F & V producing
regions & in major consumption centres
Optimum temperature to be maintained (so as
not to cause chill injury)
This also ensures supply round the year
– Seems to have little effect
– Cu(I), Cu(II) and Fe(II), Fe(III) speed up thereaction. Other metals
seems to have little effect. Can control the with metal chelators
0%MIN 30%MAX 100% MIN
24. WHY WORRY
• – Overly browned foods are not aesthetically attractive and may not be accepted
•– Also, due to the pyrazines produced by the Strecker degradation, these highly
browned foods may have odd, off flavors and also not be accepted
•– Amino acids that participate in the Maillard reactions are lost from a nutritional
point of view.
•This may be especially important where the amino acid is very reactive and in foods
where it is already in very low concentration. This would be the case for L-lysine in
•Some researchers find mutagenic products in browned model systems, others do not. But
there is still the possibility that highly browned food may contain potential mutagens.
caramel made from milk and sugar
the browning of bread into toast
the color of beer, chocolate, coffee, and maple
the flavor of roast meat
the color of dried or condensed milk
27. is one of the most important types of
browning processes in foods.
Carmelization leads desirable color and
flavor in bakery's goods, coffee,
beverages, beer and peanuts.
Undesirable effects of caramelization are
for example burned sugar smell and
28. what is caramelization
As no enzymes are involved in the caramelization
process, it is a non-enzymatic browning reaction.
Sugars in a dry condition or in concentrated form
when heated undergo a series of reaction leading
to the formation of brown color pigment called
29. WHAT HAPPENS DURING
During caramelization several flavor
compounds as well as polymeric
compounds are produced. Caramels
are complex mixture of various high
molecular weight components. They
can be classified into three groups:
30. CARAMELAN : they are the 1st polymers formed during
They are soluble in water as well as in alcohol. They are
significantly bitter in taste , on further heating these they
get converted into Caramelen.
CARAMELEN: these are dark brown in color &bitter in
taste . They are not soluble in water but soluble in alcohol.
CARAMELIN: these are almost black brown in color and
very bitter in taste . It is completely insoluble in water
&partially soluble in alcohol.
32. Diacetyl is an important flavor compound, produced
during the first stages of caramelization. Diacetyl is mainly
responsible for a buttery or butterscotch flavor.
Besides diacetyl hundreds of other flavor compounds are
produced for instance furans which have a nutty flavor .
Maltol has a toasty flavor.
Esters and lactones have a sweet rum like flavor.
The process of caramelization starts with the
melting of the sugar at high temperatures, followed
by foaming (boiling). At this stage sugar
decomposes into glucose and fructose. This is
followed by a condensation step, in which the
individual sugars lose water and react with each
other to form dimers eg: difructose-anhydride. The
next step is the isomerization of aldoses to ketoses
and further dehydration reactions. The last series of
reactions include both fragmentation reactions
(flavor production) and polymerization reactions
38. This process is often used in cooking in order to evoke
richer and more complicated flavors from food.
It is also critical in making of candy and is responsible for
the flavor, texture, and appearance of caramel.
Caramel is used to enhance the attractiveness of baked
goods by supplementing the inadequate and irregular
coloring power of refined ingredients.
Sausage casings are commonly dipped in solutions of
caramel color to give them the desired tone.
In chocolate milk , caramel colors can create an almost
In cookies, very pleasing dark shades can be achieved
by caramel color
40. Decomposition of sucrose: in which one molecule of
sucrose has to break down into fructose and glucose.
Decomposition of fructose and glucose into aroma
molecules: producing typical aroma flavor.
Oligomerization of fructose and glucose: in which 2
sugar molecule dimerize to form a new molecule.