2.  Enzyme assisted bio-chemical process that
results in the formation of brown pigments,
hence the name enzymatic browning
 Conditions required:
Exposure to air/oxygen, warm temperature,
enzyme: phenolase, pH : 5-7

3. FRUITS
Apple, Pear, Banana

4. Potato, Mushroom, Brinjal

5. Lobsters, Shrimps, Crabs

6. DESIRABLE
Tea, Coffee, Dried fruits
eg: Raisins, Figs etc
UNDESIRABLE
Fruits, Vegetables, Sea
foods etc

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
consumer acceptance
 Directly affects the quality of food (Quality
Indicator)
 Limits the shelf-life & decreases market value
of the product
 Contributes to post-harvest losses

9.  BLANCHING:
Mild heat treatment(70-100°C) for enzyme
inactivation;
Often used as a pre-treatment;
Types: Hot water, Steam, Microwave

10.  Sulphites (Sulphur dioxide) added as a
reducing agent
 Ascorbic Acid as an anti-oxidant

11.  Reduce the pH that impairs the enzyme
activity
 Enzyme activity is pH dependent
 Acids like citric acid, phosphoric etc may be
added

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
mechanical injury
(bruising)
 Cells are broken,
enzyme released, that
leads to browning
 It contributes to post-
harvest losses
 Also called melanosis
 Common in crustaceans
 Leads to discoloration
of the shell & the
muscle
 Decreases the market
value of otherwise
highly prized products

14. • Major concern for developing countries
like India
• 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
the day
 Harvest should be shifted to shade as early as
possible

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

18. MAILLARD
REACTION

19. INTRODUCTION

20. PROCESS

21. 3 BASIC STEPS

22. FACTORS AFFECTING MAILLARD
REACTION…
TEMPERATURE
– Generally, the higher the temperature, the greater the
browning
pH
– As pH goes down, so does browning.
Due to protonation of the reactive amino group, making it
unreactive

23. OXYGEN
– Seems to have little effect
METAL IONS
– 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
(e.g., EDTA).
WATER
0%MIN 30%MAX 100% MIN

24. WHY WORRY
ABOUT IT???
• – 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
AESTHETICS
•– 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
cereals.
NUTRITIONAL VALUE
•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.
MUTAGENICITY

25. PRODUCTS
 caramel made from milk and sugar
 the browning of bread into toast
 the color of beer, chocolate, coffee, and maple
syrup
 self-tanning products
 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
blackening.
Caramelization

28. what is caramelization
reaction
 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
as caramels.

29. WHAT HAPPENS DURING
CARAMELIZATION ??
 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:
 Caramelans (C24H36O18)
 Caramelens (C36H50O25)
 Caramelins (C125H188O80)

30.  CARAMELAN : they are the 1st polymers formed during
polymerization.
 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.

34. Process:
 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
(colour production).

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
muddy appearance.
 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.

41. REFERENCES
 http://www.slideshare.net/davidmbwiga1990/lect
ure-4-browning-reaction
 http://www.food-
info.net/uk/colour/enzymaticbrowning.htm
 CHEMICAL CHANGES IN FOOD DURING
PROCESSING by – O. Fennema
 isopaninsulation.com/technologies/fruit-ripening-
plants
 www.waterconf.org