Enzymes play an important role in the juice extraction and processing industry. Pectinases and cellulases are commonly used enzymes that help break down cell walls and pectin in fruits to release more juice during extraction. Enzymes also help clarify juices by degrading pectins and starches that cause haze. Other enzymes like amylases and naringinase are used to reduce viscosity and bitterness. Careful control of enzyme levels and reaction times is needed to maximize juice yield while retaining flavor and quality.

1. Enzymes in
JUICE INDUSTRY

2.  Juice extracted from a wide variety of fruits such
as apples, pears, mango and berries is used to
produce natural beverages
 This can be done simply by squeezing the fruits
but it is more common to use enzymes to increase
the volume of juice produced and the speed of
extraction
 Extraction Processes depend upon following
parameters:
 Type of fruit
 Age of fruit
 Maturity of fruit

3. Role of Enzymes in juice processing
 Extraction involves maceration (a process of
softening tissues by soaking in liquid) followed by
pressing to separate the juice from the solids
 Enzymes can play a key role in these processes in
order to;
 Improve yield
 Clarify the juice
 Stability

4.  Enzymes break down cell walls within the
fruits and release liquids and sugars
 Pectinases in combination with other
carbohydrate degrading enzymes, specially
cellulases, are useful in breaking fruit tissues to
release more juice
 Enzymatic maceration can result in extraction
of more than 95% of the soluble solids from
the fruit
 Enzymes are also used to clarify & stabilize
the juices by degrading soluble pectins and
starches that would cause haze

5. Cell Wall
 Affects the extraction of juice
 Provides structure & rigidity to pulp
 Fruit is made up of cells linked by middle lamellae
which contain insoluble proto-pectins
 Pectinases break down the pectin chains & therefore
reduce their binding action
 Cell Wall mainly Consists of:
 Pectin
 Cellulose
 Hemicellulose
 Lignin and other components

6. Enzymes used in Fruit Processing
 PECTINASES
 Break pectin into simpler units
 Clear the juice and more yield is obtained

7. TYPES OF PECTINASES
 Polygalacturonase
Responsible for the random hydrolysis of 1,4-α-
D-galacturonic linkages
 Pectin lyase
Cleaves the pectin, by an elimination reaction
releasing oligosaccharides with non-reducing
terminal 4-deoxymethyl-a-D-galact-4-enuronosyl
residues without the necessity of pectin methyl
esterase action

8.  Pectin methylesterase
 Releases methanol from the pectyl methyl
esters, a necessary stage before the
polygalacturonase can act fully
 Increase in the methanol content of such
treated juice is generally less than the natural
concentrations and poses no health risk

9. Native Pectic Enzymes
 Apples and grapes contain pectic enzymes
which can lead to spontaneous clarification of
the juices and wines if they are permitted to
stand for a considerable length of time
 Significant amount of polygalacturonase and
pectin methylesterase are found in apple juice

10.  CELLULASE
 Cellulose is a polymer of β-(1-4)-D-glycopytanosyl
units
 Responsible for the cloudiness in juices
 Cellulase is the enzyme used to degrade the
cellulose in order to clarify the juice

11.  HEMICELLULASE (XYLANASE)
Mixture of hydrolytic enzymes including: xylan
endo-1,3-b-xylosidase, xylan 1,4-b-xylosidase,
and a-L-arabinofuranosidase, strictly not a
pectinase but its adventitious presence is
encouraged in order to reduce hemicellulose
levels

12.  AMYLASE
 The Amylases hydrolyze the glycosidic linkages in
polyglucans
 Combine action of amylases on polysaccharides reduces
the viscosity

13. Glucose Oxidase
 During juice processing a considerable air is
dissolved in the juice resulting in formation of
foam
 It is undesirable because it reduces the shelf life
 Glucose oxidase is used for the removal of
oxygen from fruit juices and soft drinks

14. Naringinase
 Bitter taste of the juice and peel of citrus fruits
is largely due to the presence of naringin
 Hydrolysis of naringin first leads to a mixture of
rhamnose and prunin
 Further hydrolysis leads to glucose and
naringenin
 Enzyme responsible for the decrease in naringin
concentration is called Naringinase

15.  Its optimum pH is 4 with a range of good
activity between pH 3 to 5
 Optimum temperature for naringinase is 60 °C
 0.6% of the commercial pectic enzyme
preparation is sufficient to hydrolyze 50% of the
naringin in 3 hr

16. Polyphenol Oxidase and Methyltransferase
 Browning reactions in juices takes place in the
presence of diphenols, oxygen and enzyme
polyphenol oxidase
 Browning is undesirable but in some instances such
as apple juice consumers like amber to brown color
 Browning is most common in fruits and potatoes
which are preserved by freezing or drying

17.  Heat inactivation of enzymes is possible but effects
the texture of fruit
 Methyltransferase is used to control the browning
action by modify the substrate in such a manner that
it will not be attacked by polypenol oxidase
 Most active at an alkaline pH
 A simple adjustment of the pH of fruits to alkaline
pH levels appears to have a cosiderable effect in
preventing the browning reaction even if no methyl
transferase is added to the system

18. Fruit Juice Extraction Process
 Washing & Mechanical Maceration
 Washing
 Removal of external surface dirt & chemical
residues
 Chopping & crushing
 As the breakdown of the fruit cells continues a
variety of polysaccharides are found within the juice
extract
 These can cause the juice to become cloudy and
reduce its market value

19.  Enzymatic Maceration
 Treatment of mashed fruit with macerating
enzymes
 Either directly into the crusher/pulper or after
dilution with water, to assist homogeneous
distribution through the pulp
 Separation of Juice and Solids
Juice separation from the remaining solids in a press
or in a decanter
 Secondary Extraction
To achieve maximum utilization of the raw material
by using further enzymes

20.  Clarification
 Cloudiness due to presence of pectins
 One liter of juice with a dry matter content of
13% can contain 2-5g of pectin
 Pectin can be associated with other plant
polymers & the cell debris and cause cloudiness
in the juice
 Cloudiness can only be removed by enzymatic
depectinization

21.  After pressing, the juice is transferred to a
stirred holding tank
 Pectinases are added to the juice and incubated
at 40-50 °C
 Reaction is allowed to continue until a negative
pectin test is obtained

22.  Pectic enzymes are used in fruit juice industry to
facilitate :
 Extraction of juice
 Clarification of juice
 Separation of flocculent precipitate by
sedimentation, filtration or by centrifugation
 Resulting juices have excellent stability against
hazing
Desirability Of Clarifying Juice

23.  Sometimes use of pectic enzymes is avoided when :
 A stable cloud should be maintained in the fruit
juice
 Fruit drinks of fairly high viscosity are desired
 Pectin content of the juice must be preserved for
subsequent production of fruit jellies
 The need for the use of enzyme varies with the
difficulties of production

24.  Apples may be readily pressed without use of
the enzymes while fresh prunes cannot be
pressed without the addition of pectic enzymes
to the fruit pulp
 Enzyme concentration and reaction time should
be precise in order to have good final product
 A lengthy enzyme treatment results in the loss
of highly volatile flavor constituents
 Presence of pectin and haze in the juice leads to
cooked flavors in the pasteurized juice

25.  Fining Agents
 Activity of pectinases is reduced by fining agents
like bentonite
 Enzyme activity is allowed to complete before
fining agents are used
 Concentration / Pasteurization
 To kill any microorganism that might be present
 Also helps to improve the overall clarity of juice
 Before filling the juice it may be further filtered
and given an additional heat treatment to ensure
safety

26. Flow Diagram

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