SOP: Determination of Fill of Container for Frozen Fruits
GIFSQ — Global Institute for Food Safety & Quality
Principle
The fill of the container is determined by comparing the volume of the frozen fruit, measured by displacement in cold mineral oil, with the water capacity of the outer container.
Apparatus required
- Overflow can: a watertight stainless steel tank, 23 cm (H) × 20 cm (D), with an overflow spout of copper tubing of approximately 0.5 cm internal diameter. The tubing is soldered to an opening on the side of the can approximately 1.3 cm from the bottom, bent upward parallel to the side of the can, and bent again about 5 cm below the top to form an inverted U. The bend at the upper part of the spout is big enough in radius to let a beaker be placed beneath it to catch the overflow. A lowering device of a 1.3 cm metal frame, 14.6 cm square, with 1.3 cm mesh screening attached on one side to a perpendicular handle 30 cm long, bent outward at the top. (The can need not be exactly of the dimensions given, but it must be large enough to admit a beaker beneath the spout and made of fairly rigid metal so that its volume cannot change from outside pressure during measurement.)
- Low temperature cabinet or box with a top opening (a room held at 0°F may be used instead)
- Polyethylene bags, 20 × 25 cm, remaining pliable at 0°F and capable of holding vacuum
- Refined light mineral oil (white oil or white kerosene)
Sample preparation
Remove the frozen sample from the container and any inner wrapping and place it in a polyethylene bag. Remove excess air from the bag (as for indirect water thawing), close the bag by twisting, hold the twist with a pinch clamp, and trim off the loose end.
Procedure
Fill the can with oil and cool to 0°F
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Add sufficient oil cooled to 0°F until at least 200–300 ml of the oil overflows, producing a syphon effect; collect the overflow in a beaker
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Place an empty clean beaker or a graduated cylinder under the spout
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Immerse the bagged frozen sample completely in the mineral oil using the lowering device and let it rest at the bottom
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Record the volume of overflow collected in the beaker or graduated cylinder to the nearest ml (A)
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Repeat the operation to check the reproducibility of the result
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Determine the displacement of the empty bag and the pinch clamp in the same way (approximately 7 ml) (B)
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Determine the volume of the outer container: for regular rectangular cartons, multiply width, length and height in cm (if measured in inches, multiply by 16.39 to convert to millilitres); for packages with curved edges, irregular shapes or cup containers, fill with water to capacity or to the measured head-space and measure the volume directly in a graduated cylinder
Calculation
Net displacement of frozen product (ml) = A − B
Fill of the container, % = (Net displacement of frozen product / Water capacity of outer container) × 100
- Where,
- A = volume of oil displaced by the bagged frozen sample, ml
- B = volume of oil displaced by the empty bag and pinch clamp, ml (approximately 7 ml)
- Water capacity of outer container = volume of the outer container determined with water, ml
Note: the printed expression ends with the numeral “199” in this copy, presumed an OCR misread of the percent multiplier; the standard percent expression × 100 is carried here, flagged for checking against the printed book.
Precautions
- Keep the oil at 0°F throughout the displacement measurement.
- Immerse the sample completely and let it rest at the bottom of the can before reading the overflow volume.
- Repeat the displacement to ensure reproducibility before accepting the result.
References
Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition. Official Methods of Analysis, Association of Official Analytical Chemists, 12th edition, 1975.