🍎 Stability of canned meat — the thermostatic test (incubation at 37 °C or 55 °C, assessment of blowing)

Food chemistry PN-A-82055-5

Overview

The standard specifies the testing of the stability of canned meat by the thermostatic method: the manner of taking and preparing the samples, the course of the test, the interpretation of the results and the handling of the cans tested. The text of the standard was not available to us — the description is based on a handbook of meat processing technology (Olszewski 2007, after Encyklopedia Zarządzania), on teaching materials about canned goods and on the branch booklet of the QAFP system, which names PN-A-82055-5:1994 alongside the testing of the tightness (PN-A-82055-4) in the testing procedures for canned goods; before implementation the details have to be checked in the standard.

The test consists in incubating the cans in an incubator at a temperature of 37 ± 1 °C or 55 ± 1 °C: cans of a gross mass of up to 1 kg — for 7 days (168 h), of a mass above 1 kg — for 10 days (240 h), cans for export to tropical countries — at 55 ± 1 °C for 5 days (120 h), and pasteurised cans — at 37 ± 1 °C for 3 days (72 h), if the contract with the receiver does not provide otherwise. The raised temperature favours the development of the microorganisms which survived the heat treatment and reveals the defects of the can. The finding of blowing, of a failure to set (where the setting is laid down by a standard) or of leakage gives a positive result; a can without those defects — a negative result. In sterilised cans one positive result calls for a repeat test, and a positive result in the repeat means that the batch does not comply with the requirements of stability.

Blowing is the deformation of a can as a result of processes of decomposition or of technological irregularities: biological (gases from the decomposition of the contents by microorganisms; there is also a gasless variety, in which the contents liquefy), chemical (gases from the reaction of the contents with the material of the can) and physical (pseudo-blowing — overfilling, faulty operation of the seaming machines, expansion of the contents, freezing). The effectiveness of the sterilisation of cans that are sterilised and stable at ambient temperature is measured by the sterilisation value F0 (minutes equivalent to sterilisation at 121.1 °C), and the plan of testing cans covers the taking of samples, the testing of the tightness, the organoleptic and physical examination and the testing of the stability (the thermostatic test).

Method principle

Samples of cans from a batch are placed in an incubator (thermostat) at a temperature of 37 ± 1 °C or 55 ± 1 °C for a time depending on the mass and the kind of can (3, 5, 7 or 10 days). During the incubation the cans are observed daily in order to exclude positive results, and cans with liquid contents are shaken or turned over every 2 days. After the end of the thermostatic treatment the cans are cooled to the temperature laid down for the organoleptic examination and assessed: blowing (a bulging of the bottom or of the lid), a failure of the contents to set and leakage qualify the result as positive. A batch of sterilised cans is regarded as not complying with the requirements of stability when in the repeat test even one can gives a positive result.

Applications

• Control of the stability of sterilised and pasteurised canned meat before the release of a batch
• Assessment of the effectiveness of the sterilisation and pasteurisation and of the tightness of the packaging (together with PN-A-82055-4)
• Testing of cans for export to tropical countries (thermostatic treatment at 55 °C)
• The QAFP guaranteed food quality system — a testing procedure for canned goods
• Veterinary and sanitary laboratories — lists of methods of testing canned goods

Key parameters

Standard

Standard number

PN-A-82055-5:1994

Title (PL)

Mięso i przetwory mięsne — Badania mikrobiologiczne — Badanie trwałości konserw metodą termostatową

Title (EN)

Meat and meat products — Microbiological examinations — Testing of stability of canned products by thermostatic method (working translation)

Step-by-step procedure

1. Taking the samples

   Take from the batch samples of cans in accordance with the plan of testing (the taking of samples, the testing of the tightness, the organoleptic and physical examination, the testing of the stability); record the gross mass and the kind of can (sterilised, pasteurised, for export).

2. Choice of the conditions

   Sterilised cans: 37 ± 1 °C for 7 days (≤ 1 kg) or 10 days (> 1 kg); export to tropical countries: 55 ± 1 °C for 5 days; pasteurised ones: 37 ± 1 °C for 3 days — unless the contract with the receiver provides otherwise.

3. Incubation

   Place the cans in the incubator and maintain the set temperature for the whole period of the test.

   ⏱ Time: 3–10 days • 🌡 Temperature: 37 ± 1 °C or 55 ± 1 °C

4. Observation

   Check the cans daily in order to exclude positive results; shake or turn over cans with liquid contents every 2 days.

5. Cooling

   After the end of the thermostatic treatment cool the cans to the temperature laid down for the organoleptic examination.

6. Assessment

   Establish the presence of blowing, of a failure to set (where the setting is laid down by a standard) or of leakage — each of those defects gives a positive result; the absence of defects — a negative result. Distinguish biological, chemical and physical blowing (pseudo-blowing).

7. Decision on the batch

   For sterilised cans: one positive result → a repeat thermostatic test; if in the repeat even one can is positive — the batch does not comply with the requirements of stability. Cans with a positive result are not fit for consumption.

8. Test report

   Give the identification of the batch, the number of cans tested, the temperature and the time, the daily observations, the result for every can and the assessment of the batch.

Required equipment and apparatus

Health and safety (OHS)

• Blown cans may contain bacterial toxins and gases under pressure — do not open them outside a fume hood, do not taste them, dispose of them as waste
• The incubator at 55 °C and hot cans — gloves when taking them out
• The sharp edges of cans during the testing of the tightness and the opening — protection of the hands

Frequently asked questions