Canning of horticultural products like Fruits & vegetables, process of Canning, and the factors that affects Canning process and the effect of microorganisms and chemicals in the canned products.

1. HOR 311
POST HARVEST MANAGEMENT
AND VALUE ADDITION OF FRUITS
& VEGETABLES CROPS (1+1)
PROCESSING OF
CANNED PRODUCTS
Pesented By…
Guhan.C, B.Sc.(Hons).Agri,
Id no :2018033029,
JKKMCAS, Erode, TN.

2. CANNING
☻ Process of sealing food stuffs hermetically(airtight) in containers and
sterilizing them by heat for long storage.
☻ FATHER OF CANNING - Appertizing
☻ In 1804, Appert in France invented Canning.
Principle:
Destruction of spoilage organisms within the sealed container
by means of heat.

3. General Process Of Canning…
Selection of fruits/vegetables
Grading
Washing
Peeling
Cutting
Blanching
Cooling
Filling and Syruping (or) Brining
Exhausting
Sealing
Processing
Cooling
Storage

4. Selection
☻ Fresh and free from dirt.
☻ Fruits should be ripe, but firm and uniformly mature.
☻ Over ripe fruits should be rejected.
☻ Unripe fruits should also be rejected.
☻ Vegetables should be tender except tomatoes.
☻ Tomatoes should be firm, fully ripe and deep red in colour.
☻ Free from blemishes, insect damage or mechanical injury.

5. Grading
☻ Graded according to size and colour to obtain uniform quality.
☻ Done by hand or by machines such as screw grader and roller grader.
Washing
• To remove the dirt, dust etc., by water.
• Root crops - washed - soaking in water - 25 to 50 ppm chlorine.
• Others washing may be done by spray washing, steam washing, etc.
• Washing in running water is preferable.

6. Peeling
☻ Peeling – removal of outer layer.
☻ Hand peeling - Fruits of irregular shape. e.g. mango, papaya.
☻ Steam peeling - Potatoes and tomatoes are peeled by steam.
☻ Mechanical peeling - Apples, peaches, pineapples, for
vegetable like carrot, turnips and potatoes.
☻ Lye peeling- Peaches, apricots, sweet oranges & vegetables
like carrots and sweet potatoes are
• Dipping in 1 to 2% boiling lye solution(NaOH) for 30 sec to
2 min.
• Then alkali is removed by running water or by dipping in
0.5% citric acid solution.
☻ Flame peeling - Garlic and onion which have a papery outer
covering. The skin is burnt off.

7. Cutting & Blanching
Cutting
☻ Fruits and vegetables are cut into uniform pieces for canning.
Blanching
☻ Exposing f&v to hot or boiling
water as a pretreatment before drying.
☻ Blanching also known as scalding or precooking.
☻ Fruits are not blanched generally.
☻ Vegetables are blanched in boiling water or steam for 2 - 5 min
followed by cooking.

8. Cooling
☻ Cooling after blanching, the vegetables are dipped in cold
water for keeping them in good condition.
Filling
☻ Before filling cans are washed and sterilized.
☻ In developing countries - done by jet of steam.
☻ In developed countries - large scale filling machines
automatically do this sterilization and filling of syrup or brine
with fruits or vegetables.
☻ India – Hand filling is common.
Cooling & Filling

9. Syrupping
☻ A solution of sugar in water is called as syrup.
☻ Sucrose syrup is used in canning.
☻ Syrup is added to improve the flavour and it is serving as heat transfer
medium.
☻ Syruping is done only for fruits.
☻ 20 to 55°Brix concentration is used in syrup.
☻ Strained hot syrup is poured on the fruit pieces.
☻ The syrup should be filled at about 79 to 82°C by leaving a head space
of 0.3 to 0.5 cm.
☻ Sometimes citric acid and ascorbic acid are also mixed with syrup to
improve flavour, shelflife & to enrich.

10. Brining
☻ A solution of salt in water is called brine.
☻ Only vegetables are brined.
☻ Common salt, free from iron should be used.
☻ Hot brine of 1 to 3% concentration is used for covering.
☻ Vegetables are placed in the can & filled with brine at 79 -
82°C, leaving head space of 0.3 to 0.5 cm.

11. Exhausting
☻ The process of removal of air from cans is known as
exhausting.
☻ This is done after lidding or clinching.
Advantage
» Minimizes discoloration.
» Retention of Vitamin-C.
» Reduces chemical reaction.
» Prevents excessive pressure.

12. Sealing & Processing
Sealing
☻ Immediately after exhausting the cans are sealed air tight by means of a
sealer.
☻ Temperature should not fall below 74°C.
Processing
☻ Heating & cooling of canned foods to inactivate bacteria.
☻ Bacterial spores are destroyed at pH 3.0 (fruits) than at pH 5.0 to 6.0
(vegetables except tomato).
☻ Bacterial spores do not grow below pH 4.5.

13. Cooling
☻ After processing the cans are cooled to about 39°C to stop
cooking process and to prevent stack-burning.
☻ Cooling is done by, dipping or immersing the hot cans in
tanks containing cold water.
☻ Exposing the cans to air.
Storage
☻ After labeling, they should be packed in strong wooden cases
or corrugated card board.
☻ Stored in cool and dry place.

14. Containers for packing
☻ Tin and glass containers are used
☻ Tin containers are mostly preferred.
☻ The inside of the can is to be coated with some material (lacquer),
which prevents corrosion and discolouration but does not affect
the flavour.
☻ This process is known as “Lacquering”.
Lacqer Types…
☻ Acid-resistant : Cans coated with it are called R- enamel or A.R.
Cans meant for acid fruits.
☻ Sulphur-resistant : Cans coated with it are called C- enamel or
S-R-meant for non acid foods.

15. Causes of spoilage
By 2 reasons…
1. Physical and chemical changes
2. Microorganisms.
1. Physical and chemical changes
☻ Swell : Can become bulged. Bulge is due to positive internal
pressure of gases.
☻ Under-exhausting : Cans suffer severe strain during heat processing
due to the large internal pressure of the gas present in it.
☻ Paneling : The body is pushed inward due to the high vacuum
inside.
☻ Rust : Rust of the cans should be thoroughly examined.
☻ Foreign flavour : Under unhygienic conditions products develop

16. 2. Microbial spoilage
Mesophilic organisms
☻ Spoilage by mesophilic organisms such as some species
of Clostridium bacillus, yeast and fungi is also
indicative of under processing.
Thermophilic bacteria
☻ Cans are stored without adequate cooling, the contents
remain at a temperature favourable for incubation with
the result that bacteria multiply and spoil the product.
Clostridium
Thermoplilic