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Aseptic integrity and microhole determination of packages by electrolytic conductance measurement
Author(s) -
Axelson Lena,
Cavlin SÖRen,
Nordstrom Jan
Publication year - 1990
Publication title -
packaging technology and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.365
H-Index - 50
eISSN - 1099-1522
pISSN - 0894-3214
DOI - 10.1002/pts.2770030305
Subject(s) - penetration (warfare) , materials science , conductance , aseptic processing , length measurement , electrolyte , mechanics , composite material , optoelectronics , optics , mechanical engineering , chemistry , condensed matter physics , physics , engineering , electrode , operations research
An aseptic packaging should, in principle, provide protection against any kind of bacteriological penetration. This means that any microholes present in the packaging walls or seams must not have a diameter greater than about 0.5μm In practice, the tolerance limit probably lies higher owing to the fact that the length and surface properties of the holes obstruct penetration. The time factor, the concentration of microbes and their growth possibilities in the vicinity of the hole are of course also of crucial importance as to what practical tolerance limit should be set. This report clarifies to what extent and under which circumstances it is possible to determine the size of microholes by measuring the electrolyte conductance. The results establish that this measuring method is capable of indicating holes as small as 0.8 μm in diameter, provided that no hole is longer than 1 mm and direct current is used for the measurement. The accuracy of the method is reduced with increasing hole length. If, for example, the length of the hole is 10 mm, as it could be in a defective seal, the method only distinguishes holes that have diameters in excess of 3 μm. The analysis also shows that the accuracy of the method in measuring the hole diameter depends upon the accuracy in determining the hole length. An underestimation of the hole length results in an underestimation of the hole diameter and vice versa. The method also detects holes that do not completely penetrate the packaging material, e.g. cracks in the inner layer of the wall material, provided that the wall material is laminated with aluminium foil. Where such defects are present, a galvani‐cally generated current occurs, the size of which reveals the size of the defect in question. The method has also been applied to a number of aseptic packagings/products bought at random. It was found that microholes and other defects were surprisingly frequent — about 40% of the packagings had detectable microholes/defects, most of them having a diameter of 10 μm, assuming the hole length to be 15 μm. Despite this, no evident infection or quality deterioration of the product could be established. The practical tolerance of microholes would therefore be even higher in the cases studied. The measuring method can be recommended for determination of microholes — their size and frequency — in packagings and it can be used as a measure of the aseptic integrity of the packagings.