SOP: Determination of Total Solids in Canned Products

GIFSQ — Global Institute for Food Safety & Quality

Principle

Total solids are determined gravimetrically by drying the prepared sample on diatomaceous earth in a vacuum oven at 70 °C; the method is an alternate to minimum drained weight in canned mature processed peas, and the result is converted to total solids as a percentage of the water capacity of the container.

Apparatus required

• Flat-bottom metal dish with tight-fitting lid
• Water bath
• Hot air oven
• Vacuum oven
• Desiccator
• Weighing balance

Reagents

a. Diatomaceous earth such as Supercel, Kieselguhr or Celite — at the rate of 15 mg/sq cm.

b. Water — for diluting, if necessary, to facilitate distribution.

Sample preparation

Prepare the sample as described earlier in the book (after determining the drained weight of the canned fruit or vegetable: if only the solid portion is required for analysis, blend the material; if a composite sample of solid and liquid portion is required, blend the entire contents of the can; thoroughly mix the portion used).

Procedure

Take the diatomaceous earth at the rate of 15 mg/sq cm in the flat-bottom metal dish having a tight-fitting lid, and dry at 110 °C for 30 min

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Cool in a desiccator and weigh

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To each dish, add enough sample to leave a dry residue of 9–30 mg/sq cm, and weigh without delay so no moisture is lost

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Stir in the filter aid and spread the mixture evenly across the bottom of the dish, adding a little water if needed to get an even layer

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Drive off moisture to roughly the halfway point by drying on a water bath or in a hot air oven at 70 °C

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Once the samples look dry, finish the drying in a vacuum oven for 2 hr at 70 ± 1 °C

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Cool the dried sample in a desiccator and weigh it promptly once it is back at room temperature, then calculate the per cent total solids

Calculation

% Total solids = (weight of dried residue / weight of sample) × 100

Convert the percentage of total solids found to total solids on a percentage of water capacity as follows:

Total solids as a percentage of water capacity = (% total solids × net contents) / water capacity

Precautions

• Weigh the sample as rapidly as possible to avoid moisture loss.
• Weigh the dried sample as soon as possible after it reaches room temperature.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.

Association of Official Analytical Chemists, Official Methods of Analysis, 12th edn., Washington D.C., p. 597 (1975) — cited in the book.