用于杯装酸乳包装的不含铝复合材料封口膜特性

Charaterization of Aluminum-Free Composite Sealing Films for Yoghourt Cups

选取3种不含铝复合材料F1:聚乙烯/低密度聚乙烯·热封层(polyethylene/lowdensity polyethylene·ethylene-vinyl acetate copolymer,PE/LDPE·EVA)、F2:聚对苯二甲酸乙二醇酯/PE·热封层(polyethylene terephthalate/PE·EVA,PET/PE·EVA)、F3:PET/未拉伸聚丙烯·热封层(PET/cast polypropylene·EVA,PET/CPP·EVA)作为封口膜,对聚苯乙烯杯酸乳进行封杯。以封口膜材料特性、杯装酸乳货架寿命、杯装酸乳包装使用性能3个属性为出发点,综合比较和分析薄膜透氧量、杯装酸乳的感官评价、酸度以及贮存时间、杯装酸乳包装的封口盖膜揭开力和盖膜穿刺性能6项指标,其中测试杯装酸乳货架寿命属性时,产品贮存环境分为(30.0±1.5)、(25.0±1.5)、(4.0±1.5)℃。结果表明:同温度同湿度环境中,薄膜F3的透氧量最低,为46.602 cm^3/(m^2·24 h·0.1 MPa),氧阻隔性能最佳,薄膜F1最差。(4.0±1.5)℃时,温度对酸乳感官、酸度及贮存时间的影响没有(30.0±1.5)、(25.0±1.5)℃的显著,且贮存时间最长,可达7~8 d,此时酸度值超过87°T。相同的温度和贮存时间内,薄膜F3封装的酸乳酸度值最低,酸度值增长最慢、品质最佳。在杯装酸乳包装的使用性能中,只有薄膜F2、F3杯装酸乳的封口揭开力可以达到使用要求,同时F1杯装酸乳的盖膜易穿刺性能极差,而薄膜F3易穿刺性能容易率达85%,为最佳。综上,不含铝复合材料F3:PET/CPP·EVA最适于做聚苯乙烯预制杯装酸乳的封口膜,其最佳使用温度为(4.0±1.5)℃,可实现最长8 d货架寿命,而且该包装的使用性能亦能满足消费者需求。

Three kinds of aluminum-free composite sealing film： F1, polyethylene/low density polyethylene/ethylenevinyl acetate copolymer（PE/LDPE/EVA）; F2, polyethylene terephthalate（PET）/PE/EVA; and F3, PET/cast polypropylene（CPP）/ EVA were selected to package yoghurt in polystyrene（PS） cups. Comparison of material characteristics and packaging performance of composite films and the storage life of packaged yoghurt was carried out with respect to fim oxygen permeability, opening force and puncture resistance, and yoghurt sensory evaluation, acidity and storage life. The storage life of yoghurts packaged with F1, F2 and F3 was tested at（30.0 ± 1.5）,（25.0 ± 1.5） and（4.0 ± 1.5） ℃, respectively.The results showed that oxygen permeability of F3 was the lowest, 46.602 cm^3/（m^2·24 h·0.1 MPa）, among three kinds of films at the same temperature and humidity, and it had the best oxygen barrier property, while oxygen barrier property of F1 was the lowest. The storage temperature of（4.0 ± 1.5）℃ had less significant impact on the sensory evaluation, acidity or storage life of yoghurt than（30.0 ± 1.5） and（25.0 ± 1.5） ℃ and gave the longest storage life of 7 to 8 days, yielding an acidity higher than 87 °T at the end of the storage life. Under the same storage conditiuons（time and temperature）, yoghurt packaged with F3 had the lowest acidity and exhibited the loweest growth rate of acidity and the best sensory evaluation results. In terms of opening force, only F2 and F3 met the packaing requirements for yoghurt. F1 had very high puncture resistance while F3 was the easiest to puncture with an ease level of 85%. Together, the above fingdings demonstrate that PET/CPP/EVA film is the most suitable sealing film for packaging yoghurt in cups, which achieves the longest storage life of 8 days at（4.0 ± 1.5） ℃ and meets the packaging requirements for yoghurt.