Effect of packaging film on oxidative deterioration of fatty food packaged in plastic casings

Studies were made to investigate the relation between characteristics of packaging film and the oxidative deterioration of oil in packaged food. Four kinds of polyvinylidene chloride (PYDC) films were used; these had different oxygen gas transmission rates and optical transmittances. Raw fish meat paste containing about 6-7% of oil was put into casings made of the above film. The samples were sterilized at 120°C for 20minutes, then either stored in an incubator kept at 30°C without light or exposed to daylight, for 60-90days. Samplings were done every 30 days to determine the peroxide value (POY) of the extracted oil. The results obtained were as follows. (1) Oxygen gas transmission rate of these films were increased by heating at 120°C for 20minutes. (2) POY of oil extracted from samples stored in the incubator kept at 30°C without light increased slightly with the lapse of storage time, but no difference in POY was observed among samples packaged in casings having different characteristics. (3) On the other hand, in the case of samples exposed to daylight, the changes in POY of oil extracted from the samples which were packaged in casings having high oxygen gas transmission rates were significant. It was supposed that both the oxygen and the light which permeated through these casings enhanced the oxidation of oil in such foods.