| High pressure processing(HPP) is a new technology of cold sterilization. Has good protection for food’s original quality, especially for heat-sensitive vitamin. In order to further strengthen the sterilizing effect, high pressure and heat sterilization are combined. Pressure-assisted thermal processing(PATP) have been studied at home and abroad. The secondary pollution caused by the packaging process can be avoided for pre-packaging and then sterilizing. At the same time, study effects of HPP on packaging materials will be critical. The research subject was Effect of PATP on PA/PE Material. Distilled water, olive oil, 3%(volume fraction) acetic acid and 15%(volume fraction) ethanol were chose as food simulants. 200 MPa, 300 MPa, 400 MPa assisted 10℃, 30℃, 50℃ were as processing conditions. The structure, mechanical properties and barrier properties were studied. Analyzed through DSC and XRD testing to verify the changes of the thermal properties of PA/PE under PATP. Protective properties and structural changes were studied. The main research results are as follows:1. Obvious bubbles and delamination appeared on distilled water packaging, olive oil packaging had no visible damage, and the other two were less affected. Material damage was related to the amount of residual air, the solubility of the residual air in stimulants and material condition. After a month of storage, obvious changes appeared on 15% ethanol packaging. The migration of ethanol to the material was found by electron microscope analysis.2. Assisted temperature has great effect on sealing strength. The heat sealing strength decreased significantly(P < 0.05), when HPP assisted 50℃. Delamination and root fracture appeared in the testing specimens. The mechanical strength of PA/PE decreased obviously(P < 0.05). HPP conditions and stimulants had little effect on tensile strength and elongation at break(P > 0.05). After a month of storage, the mechanical properties decreased and the value trend to similar; the olive oil and 15% ethanol packaging had larger degree of decline for plasticizing effect.3. WVTR of PA/PE increased most in distilled water packaging. The barrier properties of distilled water packaging increased significantly when HPP assisted 10℃, affected by material damage(pinholes and stripes). Assisted temperature had great effect on barrier properties. The WVTR of 4 kinds of simulants packaging increased significantly(P < 0.05), when HPP assisted 50℃. The WVTR were close to control when HPP assisted 30℃, and the WVTR of olive oil packages decreased slightly. The changes of OTC were similar to WVTR. The OTC of olive oil packages reduced slightly when HPP assisted 10℃ and 30℃. Analyzed the reason for barrier properties changes through DSC and XRD. Crystallinity increasing were found, which would be the reason of barrier properties enhanced. After a month of storage, WVTR and OTC of 15% ethanol packages increased significant(P < 0.01), especially WVTR. The packaging material PA/PE is not suitable for alcoholic products for ethanol being adsorbed into PA/PE material.4. Analyzed the DSC of PA/PE after HPP assisted 30℃, the melting enthalpy of PA increased with the increasing of pressure, for PE material, in addition to 15% ethanol packages, the same changes were found. The melting enthalpy of PE affected by stimulants for adsorption. Analyzed the DSC of PA/PE after 400 MPa assisted different temperature, the melting enthalpy of both materials have changed significantly(P < 0.05), stimulants affected slightly(P > 0.05). Assisted temperature were significant impact, melting enthalpy have maximum increase when 400 MPa assisted 30℃, but have less increase when 400 MPa assisted 50℃. Assisted temperature would be bad for crystallinity increasing when the temperature is higher than a certain value. Did the FT-IR detection to PA and PE surfaces of PA/PE materials after a month storage, no structure changes of PA and PE materials were found by analysis. |
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