纳米TiO_2改性低密度聚乙烯包装保持山核桃贮藏品质

Nano-TiO_2 modified low-density polyethylene packaging preserving storage quality of Chinese hickory(Carya cathayensis Sarg.)

为了探索纳米二氧化钛(titanium dioxide,TiO_2)改性低密度聚乙烯(low-density polyethylene,LDPE)薄膜对山核桃贮藏品质的影响,研究了普通LDPE薄膜和纳米TiO_2改性LDPE薄膜两种包装对20℃下山核桃贮藏品质的影响。结果表明:与对照组相比,纳米TiO_2改性LDPE薄膜可更快形成高CO_2低O_2气体环境,延缓过氧化值和己醛升高,抑制过氧化物酶、脂氧合酶和脂肪酶活性,减缓脂肪、可溶性总糖、总酚和总生育酚降低。贮藏180 d后,纳米TiO_2改性LDPE薄膜包装山核桃O_2比对照组低36.36%(P<0.05),CO_2比对照组高7.25%(P<0.05);过氧化值和己醛分别比对照组低35.32%和41.21%(P<0.05);总脂肪、可溶性总糖、总酚和总生育酚分别比对照组高4.07%、6.90%(P>0.05),11.37%和8.87%(P<0.05);过氧化物酶、脂氧合酶和脂肪酶活性分别比对照组低17.21%、8.96%和20.55%(P<0.05),表明纳米TiO_2改性LDPE薄膜有利于保持山核桃贮藏品质。研究结果为山核桃保藏包装的应用提供理论参考。

Nanoparticle usually has unique physical and chemical characteristics and has become attractive to researchers inrecent years. Chinese hickory is well known because of its high polyunsaturated fatty acid （PUFA） content. However, highPUFA content limits the shelf life of the products due to the susceptibility of PUFA to oxidation. Lipid oxidation decreaseseconomic value of walnuts during the storage. Oxidation resulting in an undesirable rancid taste makes Chinese hickoryunacceptable for the consumer. Oxygen concentration is one of the most important environmental factors affecting lipidoxidation. Lipid oxidation can be inhibited by using packaging material with low oxygen permeability. Improving barrierproperties through the use of nanocomposites is an important topic of research, especially for the food packagingindustry. Nano-titanium dioxide （nano-TiO2） is a kind of nano metallic oxide which has been researched in some academicfields. Adding nanoparticles to the polyethylene （PE） could significantly decrease the oxygen, water vapor permeability andlongitudinal strength, and inhibit spore germination. TiO2 has been the focus of photocatalysts because of its physical andchemical stability, low cost, ease of availability and non-toxicity. Nanoparticle composite material has revealed its importancein agricultural products preservation these years. In this study, nano-TiO2 modified low density polyethylene （LDPE） filmpackaging was prepared by blending LDPE with nano-TiO2. The effects of nanoparticle modified LDPE film packaging onboth physiology and quality of postharvest Chinese hickory stored under 20℃ were investigated. During the storage thephysical and chemical indicators included CO2 and 02 volume fraction in packing, oxidation value, hexanal, total fat, totalsoluble sugar, activities of peroxidase, lipoxygenase and lipase, total phenol and total tocopherol, which were detected every30 d to determine the Chinese hickory quality. Results showed that most physical and chemical indicators of Chinese hickoryin each group were significantly changed （P〈0.05） during the whole storage time. Compared with the control group, nano-TiO2modified LDPE film was more effective in forming high CO2 and low 02, delaying the increase of peroxide value and hexanal,slowing the decrease of fat, soluble sugar, total tocopherol and total phenols, and inhibiting the activities of peroxidase,lipoxygenase and lipase. After 180 d, 02 content of nano-TiO2 modified LDPE film was 36.36% lower and CO2 content was7.25% higher than that of the control. The results indicated that nano-TiO2 modified LDPE film had low gas permeability（P〈0.05）. Oxidation value and hexanal content were respectively 35.03% and 41.21% lower than that of the control （P〈0.05）.Total fat, soluble total sugar, total phenol and total tocopherol were respectively 4.07% （P〉0.05）, 6.9%, 11.37% and 8.87%higher than that of the control （P〈0.05）. Activities of peroxidase, lipoxygenase and lipase were respectively 17.21%, 8.96%,and 20.55% lower than that of the control （P〈0.05）. All these were maybe due to the lower gas permeability of nano-TiO2modified LDPE film. These results indicated nano-TiO2 modified LDPE film is effective in maintaining the quality andprolonging the storage life of Chinese hickory and has a potential application prospect in the packaging of postharvest Chinesehickory. This paper provides the reference for the application of nanoparticle modified composite film materials in thepreservation of Chinese hickory.