Steps involved in canning of fruits and vegetables 1. Preparation of fruit and vegetables: Preparation of food commodity for canning consists of washing, sorting, grading, peeling, halving, blanching etc. 2. Raw material selection/receiving: For canning, fruits should be ripe but firm, evenly matured, free from blemishes, insect damage and malformation. Thus, harvesting at proper maturity is an important step in selection of raw material for canning.
- Most fruits are harvested at soft ripe stage. However, apple, pear, peach and banana harvested at mature stage are preferred for canning.
- Over ripe fruits yield poor quality product, while under ripe/immature fruit generally shrivel or toughen on canning.
- Vegetables except peas, beans etc are harvested at mature stage to enable them to withstand cooking during sterilization.
- Vegetables like green beans, green peas, ladies finger should be tender and free from soil, dirt etc.
- Tomatoes should however, be firm, fully ripe and uniformly deep red in colour.
The specific requirements for canning of fruits and vegetables are given under Table 7.2 and 7.3.Table 7.2 Specific requirement for canning of fruits
Fruits
|
Preparation
|
Syrup
Strength (oB)
|
Exhaust
|
Processing time at 100oC A2½ can) minutes
|
Type of can
|
Apricot
|
Use whole or halves, peel by dipping in boiling lye solution (2% NaOH) for 30 seconds to 1 minute, dip in cold water, cut two halves, remove pit, keep immersed in 2%salt solution until filled in can.
|
40 + 0.1 % citric acid
|
Exhaust can at 82-100oC for 6-10 minutes or until temperature in can center reaches 79oC.
|
20-25
|
Plain
|
Peach
|
Use whole fruit ,peel by dipping in boiling lye solution (2% (NaOH) for 30 seconds to 1 minute dip in cold water, cut two halves, remove pit, keep immersed in 2% salt solution until filled in can.
|
40
|
-do-
|
25
|
Plain
|
Banana
|
Peel, cut in to slices 12mm thick
|
30
|
-do-
|
25
|
plain
|
Grape fruit
|
Dip fruit in hot water at 93oC-96oC for 3-5 minutes, remove skin. Dip the peeled whole fruit in 2% hot lye, wash and separate the segments, fill segments in can.
|
60
|
Exhaust can at 82-87oC for 25-30 minutes or until temperature at center of can reaches 79oC.
|
30-40
|
Plain
|
Guava
|
Peel, cut into pieces, remove seeds and keep in 2% brine to prevent browning and fill in can.
|
40
|
-do-
|
20
|
plain
|
Litchi
|
Peel by hand, remove pits.
|
40+0.5% citric acid
|
-do-
|
25
|
plain
|
Pineapple
|
Peel, core and slice fruit, punch circular rings (5.6-8.8 cm diameter)
|
40
|
-do-
|
25
|
plain
|
Pear
|
Peel by hand, cut longitudinally into two halves, core and keep in 2% brine to prevent browning until filled in cans.
|
40+0.1%citric acid
|
-do-
|
20-25
|
plain
|
Jack fruit
|
Cut fruit into pieces, remove bulbs, separate seed from bulbs, use whole, halves or quarters.
|
50 + 0.5-0.75%
citric acid
|
-do-
|
20-25
|
plain
|
Loquat
|
Cut into halves
|
40
|
-do-
|
25
|
plain
|
Mango
|
Peel ,cut into slice, dip in 2% salt solution until filled in can.
|
40+0.3%citric acid
|
-do-
|
25
|
plain
|
Papaya
|
Peel, cut into slices, discard seed
|
45+ 0.5%
citric acid
|
-do-
|
25
|
plain
|
Table 7.3 Specific requirement for canning of vegetables.
Vegetable
|
Preparation
|
Brine strength (%)
|
Exhaust
|
Processing
(A2½ can) at 121oC (0.7 kg/cm2 steam pressure)
|
Type of can
|
Asparagus
|
Wash, grade, cut lengthwise into pieces of desired size, blanch for 2-3 min.
|
2.25%
|
Exhaust can at 90-100oC for 7-10 minutes, (79oC in can center)
|
24
|
Plain /sulphur resistant
|
Beans
|
Use tender, stringless beans, slice 2.5cm length, blanch and fill in can.
|
2.25
|
-do-
|
40
|
Plain/ sulphur resistant
|
Cabbage
|
Shred cabbage, blanch in 1% citric acid boiling solution for 5-6 min, cool in 2% brine prevents discolouration fill in cans
|
2.0
|
-do-
|
40
|
Plain
|
Cauliflower
|
-do-
|
2
|
-do-
|
20
|
Plain
|
Carrot
|
Wash, scrape and blanch for 5-10 minutes in boiling water
|
2
|
-do-
|
25
|
Plain
|
Mushroom
|
Use tight buttons, blanch for 4-5 minutes, immerse in 2% salt solution, fill in cans.
|
2.0+ 0.3 % citric acid+ 1% sugar
|
-do-
|
25
|
Plain
|
Peas
|
Shell, grade, boil for 3-5 min
|
2+2.5% sugar
|
-do-
|
45
|
Sulphur resistant
|
Potato
|
Peel, keep in 2% brine, blanch in boiling water for 2-3 min, keep in 2.5% CaCl2 for 1 hour, wash and fill in cans.
|
2
|
-do-
|
45
|
Plain
|
Okra
|
Tender whole, blanch in boiling water for 1-2 minutes, cool in brine solution of 1-2% for 10 minutes, fill in can.
|
2 or in tomato sauce
|
-do-
|
35
|
Plain
|
|