Evaluation of changes in properties of PA/PE film used for vacuum-packed lactic acid cheese

The subject of research was to assess the changes of properties of PA/PE packaging film used for vacuum packing of lactic acid cheese. The research investigated the influence of storage time, low temperature and the presence of lactic acid produced by lactic fermentation bacteria on the packaging film features such as barrier properties towards water vapour and the degree of swelling. The assessment comprised period of 14 days of cheese storage at the temperature 4 +/- 2 degrees C. At the same time, the tests in model conditions were conducted, consisting of storage of the packaging film filled with solutions of lactic acid and distilled water at this temperature. The obtained results showed that during period of 14 days of lactic acid cheese storage, there had occurred the increase and decrease in the permeability of PA/PE packaging film coming from the stored cheese. The results achieved from the study revealed a difference in the permeability and the degree of swelling of the films coming from the cheese and from packaging of bags filled with lactic acid. The study revealed the influence of even a small fluctuation of acidity on the level of changes of permeability of the film regarding water vapour in the model conditions. In packages taken from the refrigerated lactic acid cheese a significant dynamic relation was discovered in the increased degree of swelling up to 7 days of storage in comparison to the results achieved in the model condition. The study shows that lactic acid is not the only factor determining the dynamics relation in the changes of permeability of the films during storage of the cheese.