Freezing technology has made green peas available throughout the year. How are these peas frozen? Get to know more about the varieties and the technology behind 'Freezing of Green Peas' through this presentation..

1. FREEZING OF GREEN PEAS
Moksha Chib
13FET1003

2. Why freezing ?
▪ Canning has extensively been used as a preservation technique for green peas
▪ Canned peas even though retain their nutritive value, but no one claims that they taste like freshly cooked
green peas. It still leaves much room for enhancement in the flavor and color standpoint
▪ Freezing preservation, if properly carried out, comes much closer to retaining the natural fresh flavor
▪ If the peas are properly blanched, quickly frozen & then stored at a sufficiently low temperature, the colors of
the vegetable are retained perfectly
QUALITY
ATTRIBUTES
FROZEN FOODS
(% score)
CANNED FOODS (%
score)
DRIED FOODS
(% score)
OTHERS
( % score)
Freshness 71 14 5 10
Taste 56 30 7 7
Appearance 62 28 3 7
Nutritive value 51 20 11 18
Value of money 47 29 10 13
Ease of preparation 40 52 3 3

3. INDIVIDUAL QUICK
FREEZING OF PEAS

4. Individual Quick Freezing (IQF)
▪ Freezing of solid foods/pieces/grains like peas, cut beans to a very low temperature (-18°C)
rapidly
▪ Rapid lowering of temp makes it possible to pass quickly below the critical temp of 0-5°C at
which intracellular liquids i.e. water freeze and forms ice crystals
Advantages over Slow Freezing:
1. Ice crystals formed are much smaller which causes less damage to the cell structure & texture
2. Shorter freezing period, which means less time is allowed for the diffusion of salts & the
separation of water in the form of ice
3. Product is quickly cooled below the temp, at which no microbial growth occurs, preventing
decomposition of food during freezing
4. Inherent speed & greater output and hence, greater capacity for the commercial freezing plants
with the resultant cost reduction

5. Process chart for quick freezing of green peas
Peas Size Grading
Washing/
Dry Cleaning
Peeling/
Preparation
Blanching
Pre-cooling or
chilling to 5-
7°C
Freezing (IQF)
at -18°C
Weighing &
Packaging
Frozen Peas

6. Selection of varieties suitable for freezing
▪ Proper varieties at optimum maturity & freshness are selected
▪ Variety must yield well (high insect resistance, high edible part recovery, resistance to unfavorable climatic
conditions & uniformity of quality) & have a growth habit which will permit harvest by a mowing machine
▪ Must be tender & sweet at optimum maturity
▪ Must turn to a brilliant green color on blanching
▪ Must not have a tendency to split during blanching, cooling & packaging and easily podded
▪ Must not tend to develop off-flavors during preparation for freezing
Varieties of peas commonly used for canning, the Alaska, Surprise, Perfection etc. do not yield
particularly desirable frozen products as they are relatively light in color & small-seeded as
compared to varieties commonly grown in market gardens & for shipment during off-season.
Most retail markets demand large seeded, tender peas, high in sugar and low in starch.

7. Suitable varieties
The following varieties are recommended by IRAI for commercial scale cultivation and processing. Garden pea
varieties are grouped into i) Smooth or soft seeded and, ii) Wrinkle seeded. The latter are sweeter. Each group
has a) Early b) Mid Season and c) Late Varieties, divided according to their period of maturity.
GROUP VARIETY DESCRIPTION
Early Asauji Smooth seeded variety suitable for early sowing, takes 60-65 days to be ready
for green pod harvestMeteor
Early Badger Wrinkle seeded, high yielding, dwarf variety which takes 65 days for harvest
Arkel Wrinkle seeded, high yielding, dwarf variety, takes 60 days to be ready for
harvesting
Mid- season Bonneville Wrinkle seeded, double podded, medium tall variety, takes 85 days to be
ready for harvesting
Late season N.P 29 Plants tall, wrinkle seeded, takes about 100 days to harvest maturity
For hilly areas Early Giant Earle, tall plants, dark green pods with wrinkled seeds
Alderman Early, tall plants, pods more or less straight, 9cm in length

8. SIZE GRADING
Is done by grading drums.
These screen drums,
revolving, allow the immature
peas to drop into a waste bin
& sort the others into 3 sizes:
Large , small and medium
WASHING OF PEAS to remove
any field contamination
PEELING OF PEAS to separate
the peas from the pod
Largest starchy peas and
smallest peas lacking
‘body’ are eliminated

9. Blanching
Purpose of blanching:
1. The inactivation of enzymes (catalase, peroxidase, oxidase) to prevent any enzymatic
activity which may lead to off-flavors & odors during cold storage & thawing
2. Secondary benefits:
▪ Destroys vegetative cells of microorganisms on the surface, complementing the action of
washing
▪ Fixes or enhances the green color
▪ Eliminates any remaining insecticide residues
▪ Eliminates the off-flavors produced by gases & other volatile substances that may have
formed during the time between harvesting & processing
The duration of blanching varies according to the method employed, product type & variety,
product size, degree of ripening & the blanching temperature.

10. Heat
Treatment in
water at 98°C
(Time)
Residual Enzyme Activity (%) Quality Evaluation after
one year’s storage
Color Flavor
Lipoxygenase Catalase Peroxidase
None (Control) 100 100 100 Discolored Strong off-
flavor
2.5 sec 80 36 65 Discolored Off-flavor
5 sec 62 28 52 Discolored Good
10 sec 6 2 34 Good Good
15 sec 1 0.3 23 Good Good
3 min - - 0.3 Good Good
Relationship between the Heating Time, Residual Enzyme Activity &
Quality Retention of Frozen Peas
It is found that the quality of frozen peas after undergoing blanching was superior if a
certain level of peroxidase activity remained at the end of the blanch. Total absence
of peroxidase indicates over-blanching. Peas must be blanched until 2-6.3% of
peroxidase activity is retained.
Most optimum
temperature range for
blanching of peas was
found to be 76.6-
87.77°C.
• Below this temp did
not entirely inhibit
the formation of off-
flavor
• Above this temp
resulted in loss of
fresh flavor &
formation of
‘cooked’ flavors
Blanching time in water at
100°C is 1-1.5 min

11. Individual Quick Blanching (IQB)
▪ Drying the peas with warm air followed by spreading them in a single layer on
belt & heating with steam
▪ These are then held in a multi-layer chamber for thermal equilibrium
▪ Pros: Faster & more uniform blanching with improved color retention , reduced
nutrient losses & less leaching of soluble giving better yield & giving increased
energy savings

12. Pre-Cooling followed by IQF
PRE-COOLING
▪ Peas are dropped into a shaker washer where they are cooled by cold water spray (5-7°C)
▪ Peas can also be cooled with a fine fog of water, most of which evaporates or is absorbed
INDIVIDUAL QUICK FREEZING
▪ Fluidized belt freezers are used
▪ The product is kept in suspension using a sufficiently powerful stream of cold air (-79°C)
which is forced up through the layer of the food
▪ Since each piece is kept loose & free flowing by air pressure, freezing time is far less than usual
air blast freezing
▪ Peas generally fluidize easily and freeze in about 4 minutes!

14. Fluidization causes products to behave like fluid because they are suspended
by refrigerated air that flows from underneath the perforated belt or tray.
The air pressure is equal to the weight of the product.
The airflow is evenly distributed rather than being concentrated in one
section. Through fluidization, products are separated from one another and
frozen more quickly. This preserves the product’s flavor and texture, while
minimizing dehydration which tends to occur with slower freezing rates.
The product enters the infeed and proceeds to 2 freezing zones:
1. Initial Freezing Zone: here the airflow is higher. The product is
rapidly crust-frozen, locking in moisture so the product’s
weight, appearance and quality are preserved before it proceeds
to the next and final stage of the freezing process.
2. Final Freezing Zone: The temperature is lower, so the product
becomes fully frozen.
A weir, or retaining plate, separates the two zones, and ensures the
proper holding time for products in each zone.

15. Evaporators: They continously remove moisture from
the cold air
3D Airflow system: This system blasts air at differnet
speeds & in different directions, separating snow &
residual moisture form the air stream
Agitators/ Pulsators: Gently shake the product back
and forth horizontally & vertically in order to prevent
any formation of holes & helps in maintaining a
uniformly fluidized bed
Trays: Their size and pattern are customized to
accommodate peas so that they do not fall through the
perforations during the freezing process
Air Modulator Sheets: Adjust the airflow and the
temperature. These are present underneath the tray or
the belt

16. Packaging & Cold Storage
▪ Airtight containers which are moisture-vapor-proof & cold
resistant are preferred. Metal containers need not be
lacquered
▪ Parchment bags or wraps enclosed in cartons may also be
used for dry frozen peas. Liquid pack with 2% brine can be
added to cover the product in order to produce highest
quality peas
▪ Cold storage at -18°C is preferred with -9°C as the highest
permissible limit
▪ Special refrigerating equipment can be used to produce
single-frozen or glazed peas rather than a solid mass
Storage Temp -12°C -18°C -24°C
Storage life of Frozen Peas 6 months 24 months >24 months

17. References
▪ Freezing Preservation of Fruits, Fruits juices and Vegetables
by Tressler, Donald Kiteley, 1894-; Evers, Clifford F
▪ Quick Freezing Preservation of Foods: Foods of plant origin by J. S.
Pruthi
▪ “Fluidization and FLoFREEZE IQF freezers: the revolution
continues” by FMC FoodTech