Aim: To conduct cut out analysis of canned fruits and vegetables products..
Theory: Cut out examination of canned products is conducted to evaluate the product whether conforming to FPO standards or not. Canned fruit and vegetables are evaluated for presence of vacuum or pressure in the can, drained weight, total soluble solids, presence or absence of preservative, internal condition of can product contents and presence or absence of fermentation for ensuring microbiological safety.
Reagents/glassware/apparatus required
1. Can opener
2. Balance for estimating drained weight
3. Head space gauge
4. Vacuum cum Pressure gauge
5. Thermometer
6. Refractometer, hydrometer or salometer
7. Sieve of 20.3 cm having o8meshes per 2.5cm.
Procedure for cut out analysis
A. External/physical examination of unopened can
1. Note the gross weight of the can.2. Note the label information from the label of the can. Compare the label with requirement as per FPO. 3. Note the external condition of can like dents, rusty spots, scratches, leakage around seams and condition of ends as per following classification.
- Flat: A can where both ends are concave. The vacuum is high enough to maintain the ends concave. (Flat can is considered optimum condition of can).
- Flipper: A can where vacuum is so low that mechanical shock will produce distortion of one or both ends. (Not desirable)
- Springer: A can in which one end is distorted and the other end is flat and pressure on the convex end will cause the flat end to spring out when pressed. (Not desirable)
- Swell: A can in which both ends are convex i.e. in which there is a sufficient pressure to cause permanent distortion of both ends. (Not desirable and should be discarded)
4. Note vacuum/pressure in the can by inserting vacuum/pressure gauge. (Can with good vacuum is desirable, can showing pressure is not desirable).
1. Open the can with a can opener2. Note the appearance on the surface.
- See for under filling and over filling of cans.
- Cloudiness in syrup: Note colour, clarity and flavour of syrup or brine.
- Use refractometer for measuring 0B and salometer for percent salt
- Note appearance of the material filled, record as satisfactory or unsatisfactory
3. Gross head space: Measure with seam checking gauge or head space gauge.
- Net weight or volume of contents
- Net volume of contents in relation to capacity of can
- Vacuum/ pressure: No positive pressure at sea level
- Head space: Not more than 1.6 cm (0.63 inch)
- Internal appearance of can Examine the internal surface of can after emptying and washing. See for evidence of corrosion, blistering, defects in lacquer, scratching, discoloration, leaks etc.)
- Tin content: Not more than 250 ppm (Determine using standard method)
- Examination of spoilage: No sign of swelling when cans are incubated at 37ºC for fruits and 55ºC for vegetables for 7 days.
- Fruit/ vegetable contents: Evaluate the sensory parameters like colour, firmness, flavour and overall acceptability.
Vacuum/pressure determination
- Use gauge which indicates both vacuum and pressure.
- Pierce the hollow pointed end of the gauge through the lid so that rubber gasket makes a gas tight seal and prevents the loss of vacuum.
- Moisten the rubber before applying the gauge and pierce the can with the gauge towards one edge.
- The vacuum or pressure is indicated by a needle on the dial of the gauge.
- Note the vacuum in (inches of Hg) and pressure (lb/in2) or kg/cm2.
- Do not measure pressure of swollen cans.
- The vacuum varies with altitude, storage temperature and head space volume.
- Generally cans should not show any positive pressure at sea level.
Drained weight: The sample is drained on a standard mesh size sieve and weighed. The drained weight is the weight of the sieve and the contents after draining minus the weight of the dry sieve.
Net weight of contents: Wash the inside of the can with water, dry and note the tare weight of the empty can. Subtract the tare weight from gross weight to get the net weight of contents.
Procedure for determining drained weight
- Weigh the unopened can; open and pour the entire contents on a circular sieve without disturbing the product, incline the sieve to facilitate draining of syrup/brine.
- In case of products with a cavity such as peach, apricot, guava, pear halves, invert the cups /halves down on the screen so that the liquid can drain out but the product should not be disturbed. (Use circular sieve containing 8 meshes to 2.5 cm i.e. 0.097 inch openings. For A 2 ½ (401×411) size can use sieve of 8 inches in diameter. For A 10 can use sieve of 12 inch in diameter. For tomatoes, use sieve containing 12 meshes to an inch i.e. 0.446 inch opening.
- Drain for five minutes.
- Weigh the drained product from the sieve.
- Empty the can and take the tare weight of can including ends.
- Calculate net weight and % drained weight as under:
Drained weight
Drained weight (%) = --------------------------- x 100
Net weight of content
Net weight of contents = Gross weight of can - Tare weight of empty can
Estimation of vegetable contents in sauce
- Empty the contents of the can on the sieve
- Wash the contents with water to make free of sauce
- Note the weight of the sieve and washed vegetable
- Subtract the weight of the dry sieve and calculate the vegetable content as percentage of the net weight of the contents of can.
Estimation of foreign matter in cans
- Note for presence of foreign matter such as flies, ants, maggots, leaves, straw, hair etc. in the can. Their presence indicates gross carelessness and working under un-hygienic conditions.
- The micro-organisms growing at 37oC usually cause spoilage accompanied by the production of gas (CO2) which causes the cans to become ‘springers’ or ‘hard swell’.
- A can which swells at 370C indicates presence of living mesophilic organism usually caused by leakage.
- At 55oC, cans do not generally swell. Spoilage causing micro-organisms are flat sour type and they do not grow at low temperature.
|
Participants