Influence of High Pressure Processing on the Reversibility of LDPE and PA6 Food Packaging Materials
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Abstract:
This study investigated the tensile strength, heat-sealing properties, thermal properties, barrier properties, and reversibility of LDPE and PA6 films under different conditions of high-pressure processing (HPP) compared to control samples processed at atmospheric pressure. The results showed that the effects of pressure, dwell time, and storage time on the heat-sealing properties of LDPE and PA6 materials were not significant, but the tensile strength of LDPE and PA6 samples increased significantly as the pressure increased; When the pressure was lower than 300 MPa, the water vapor transmission rate (WVTR) of LDPE increased gradually, while the WVTR gradually decreased when the pressure was higher than 300 MPa. For PA6 samples, when the pressure was higher than 100 MPa, the WVTR decreased from 10.13 g/(m2?day) (0.1 MPa/10 min) to 6.79 g/(m2?day) (200 MPa/10 min), but the reduction was not significant with increasing pressure. The melting enthalpy of LDPE and PA6 samples increased under HPP treatment, which was recovered after storage for 24 h. Compared with 0.1 MPa, the permeation of p-cymene through LDPE and PA6 films was reduced by about 50% and 58%, respectively, under different HPP treatments, but returned to levels observed at atmospheric pressure almost immediately when the pressure was released. The results show that the properties of LDPE and PA6 films are reversible under HPP treatment, hence both are suitable for HPP.
