食品用塑料复合包装膜中残留甲苯迁移规律及迁移机理研究

发布时间：2018-05-11 11:03

本文选题：塑料复合膜 + 甲苯　；参考：《沈阳农业大学》2017年博士论文

【摘要】：食品用塑料复合包装膜是将两种或者两种以上材质的塑料薄膜通过胶黏剂复合在一起,同时具有各层薄膜的优良性质,是目前市场上最为理想的软包装材料。低密度聚乙烯(LDPE)和流延聚丙烯(CPP)具有独特的防潮性和热封性,常作为复合膜的内层膜基材,与食品直接接触。在生产过程中,油墨、胶黏剂及其稀释剂等有机溶剂夹在复合膜的中间层,如果含量较高或挥发不充分,可能会发生残留并迁移到食品中。残留溶剂通常是几种有机溶剂的混合体,其中主要为甲苯和乙酸乙酯等,而甲苯是公认的致癌物质,且吸附性较高、易发生残留。因此,本研究以食品用塑料复合包装膜为试验材料,系统研究了普通塑料复合膜和耐蒸煮塑料复合膜中残留甲苯向食品模拟液中的迁移规律,进一步研究了耐蒸煮塑料复合膜中残留甲苯向猪肉中迁移效果,探讨蒸煮条件对膜阻隔性能和机械性能的影响;建立迁移数学模型并对模型预测效果进行评价;采用红外吸收光谱、扫描电镜、差式扫描量热分析、热重分析等技术手段,研究迁移条件对塑料复合膜内层膜微观结构的影响,从而探讨甲苯迁移机理,为保障食品安全及建立相关法律法规提供理论依据。主要研究结果如下:(1)温度越高,塑料复合膜中残留甲苯向模拟液中的迁移率越高。迁移时间越长,甲苯迁移率越高,并最终趋于稳定值;模拟液对甲苯迁移率影响较为显著。普通塑料复合膜中甲苯向不同食品模拟液中的迁移率大小依次为:异辛烷50%乙醇3%乙酸10%乙醇。耐蒸煮塑料复合膜中甲苯向不同食品模拟液和调味品模拟液中迁移率大小依次分别为:橄榄油3%乙酸超纯水;3g/100mL氯化钠0.1g/100mL谷氨酸钠5g/100mL蔗糖;内层膜厚度越大阻隔性越好,甲苯向模拟液中的迁移率越低。普通塑料复合膜中,甲苯透过不同材质内层膜向模拟液中迁移率大小依次为:LDPE30LDPE50CPP30CPP50;不同微波加热条件对耐蒸煮塑料复合膜中甲苯迁移率产生一定影响。微波功率越大、加热时间越长,甲苯迁移率越高。无论是使用哪种功率进行微波加热,当模拟液加热到大约80℃时,甲苯迁移率差异不显著。(2)猪肉中甲苯的适宜提取条件为:异辛烷作为萃取溶剂,振荡萃取40 min,该条件下甲苯的回收率在80.3%～88.7%之间,相对标准偏差(RSD)在3.2%～6.1%之间;蒸煮温度越高、时间越长,甲苯迁移率越大,但在121℃和135℃温度下,蒸煮20 min后甲苯迁移率变化不显著;猪肉中脂肪含量越高,甲苯迁移率越大;接触食品的塑料表面积与猪肉体积之比(表面积-体积比)对甲苯迁移影响较小;高温蒸煮可使膜阻隔性能降低,蒸煮时间越长,膜的阻隔性能相对越弱。随着蒸煮温度的升高和时间的延长,膜的拉断力和断裂伸长率下降,尤其是断裂伸长率变化更为明显。(3)采用Brandsch经验模型和Fick定律推算模型计算塑料复合膜中甲苯迁移扩散系数经验值(Dexp)和Fick定律推算值(DFick)。结果表明,甲苯扩散系数Dexp和DFick均随着温度的升高而增大。大多数情况下,塑料复合膜中甲苯扩散系数经验值高于Fick定律推算值(Dexp㧐Dfick),仅CPP30样品在4℃～20℃迁移温度下,甲苯向异辛烷中迁移时的Dexp㩳DFick;无论选用何种模拟液,相同温度下甲苯扩散系数经验值(Dexp)均相同;利用分配系数定义式来计算迁移过程中塑料复合膜中甲苯分配系数(KP.F),KP.F 越小表明甲苯向模拟液中的迁移量越大。温度越高,甲苯向同种模拟液中迁移KP.F值越小。普通塑料复合膜中甲苯向不同模拟液中迁移的KP.F值大小依次为:3%乙酸10%乙醇50%乙醇异辛烷。耐蒸煮塑料复合膜中甲苯向模拟液中迁移的KP.F值大小依次为:超纯水3%乙酸橄榄油;建立单层迁移数学模型并对其简化,以Dexp和KP.F作为模型中重要参数,并将甲苯迁移量的模型推算值与试验值进行比较。结果表明,模型可以较好的预测甲苯迁移量的变化趋势。除了在4℃和20℃条件下,CPP30样品中甲苯向异辛烷中迁移量的模型值略小于试验值外,其他条件下,LDPE30、CPP30和RCPP70三种样品中甲苯迁移量的模型值均大于或约等于试验值。(4)经迁移条件处理后,普通塑料复合膜(LDPE、CPP)和耐蒸煮塑料复合膜(RCPP)三种样品红外吸收光谱中部分吸收峰均向低波长方向移动,说明膜内部分子间作用力下降;扫描电镜显示经处理后的样品断面微观结构出现褶皱、扭曲等现象,CPP膜微观结构变化略小于LDPE膜,异辛烷和橄榄油分别对普通膜和蒸煮膜微观结构影响较大;DSC分析表明样品经处理后膜的熔点和热焓值均下降,说明膜的热稳定性变差,结晶度降低,CPP膜变化幅度小于LDPE膜。未接触模拟液的RCPP样品在高温蒸煮后,膜的结晶度降低,但热稳定性变化较小;TG曲线显示经处理后的LDPE和CPP样品热分解温度降低,热稳定性下降,RCPP样品在高温蒸煮后,膜的热稳定性变化较小。
[Abstract]:Plastic composite packaging film for food is combined with two or more than two kinds of plastic film through adhesive. It is the most ideal soft packaging material in the market at the same time. Low density polyethylene (LDPE) and CPP have unique moisture resistance and thermal sealing. In the process of production, organic solvents such as ink, adhesives and their diluents are sandwiched in the middle layer of the composite membrane in the process of production. If the content is higher or less volatile, it may occur and migrate to the food. The residual solvent is usually a mixture of several organic solvents, mainly toluene and B While toluene is recognized as a carcinogenic substance, and its adsorbability is high, it is easy to remain residual. Therefore, this study has studied the migration of residual toluene in the common plastic composite film and the steamed plastic composite membrane with the plastic composite packaging film as the experimental material. The effect of residual toluene to pork in the membrane was studied, and the effects of cooking conditions on the membrane barrier property and mechanical properties were investigated. The migration mathematical model was established and the prediction effect was evaluated. The transfer conditions were studied by infrared absorption spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and other technical means. The mechanism of toluene migration is discussed in order to provide theoretical basis for guaranteeing food safety and establishing relevant laws and regulations. The main results are as follows: (1) the higher the temperature, the higher the mobility of residual toluene in the plastic composite membrane. The longer the migration time, the higher the transfer rate of toluene, and finally to a stable value. The migration rates of toluene to different food analog liquid in the ordinary plastic composite membrane are in turn: isooctane 50% ethanol 3% acetic acid 10% ethanol. The migration rates of toluene to different food analog liquid and seasonings in the steamed plastic composite membrane are respectively: olive oil 3% acetic acid super. Pure water; 3g/100mL sodium chloride 0.1g/100mL sodium glutamate 5g/100mL sucrose; the greater the thickness of the inner film thickness, the better the barrier property, the lower the mobility of toluene to the simulated solution. In the ordinary plastic composite membrane, the size of the transfer rate of toluene through the inner membrane of different materials is as follows: LDPE30LDPE50CPP30CPP50. The mobility of toluene in the composite membrane has a certain effect. The greater the microwave power, the longer the heating time, the higher the mobility of toluene. No matter which power is used for microwave heating, when the simulation solution is heated to about 80 C, the difference of toluene mobility is not significant. (2) the optimum extraction conditions for the toluene in pork are: isooctane as an extraction solvent, oscillation. The recovery of toluene was 40 min, the recovery rate of toluene was between 80.3% and 88.7%, and the relative standard deviation (RSD) was between 3.2% and 6.1%. The higher the cooking temperature, the longer the time, the greater the mobility of toluene, but at the temperature of 121 and 135 C, the change of toluene mobility was not obvious after 20 min, the higher the fat content in the pork, the greater the toluene mobility; contact with the higher the transfer rate of toluene. The ratio of plastic surface area to pork volume (surface area volume ratio) has little effect on the migration of toluene; high temperature cooking can reduce the membrane barrier performance and the longer the cooking time, the weaker the membrane barrier performance. With the increase of cooking temperature and time, the breaking force and elongation at break of the membrane decrease, especially the elongation at break. (3) the empirical value (Dexp) and Fick law calculation value of the toluene transfer diffusion coefficient (Dexp) and Fick law are calculated by the Brandsch empirical model and the Fick law calculation model. The results show that the toluene diffusion coefficient Dexp and DFick increase with the increase of temperature. In most cases, the diffusion coefficient of toluene in the plastic composite membrane has been found. The test value is higher than the Fick law calculation value (Dexp? Dfick). Only CPP30 samples at 4 ~ 20 C migration temperature, Dexp? DFick when toluene migrated into isooctane; no matter which analog liquid is used, the empirical value of toluene diffusivity (Dexp) is the same at the same temperature, and the toluene fraction in the plastic composite membrane during the migration process is calculated by the definition formula of distribution coefficient. The smaller the distribution coefficient (KP.F), the smaller the migration of toluene to the simulated solution. The higher the temperature, the smaller the KP.F value of toluene migrated to the same analogue liquid. The KP.F value of toluene migration to different analog liquid in the ordinary plastic composite membrane is 3% acetic acid 10% ethanol and 50% ethanol isooctane. The KP.F value of the transfer is in turn: ultra pure water 3% acetic olive oil; a single layer migration mathematical model is established and simplified. Dexp and KP.F are used as important parameters in the model, and the calculated value of toluene migration is compared with the experimental value. The results show that the model can predict the change trend of toluene migration well. Except at 4 degrees C The model value of the migration of toluene to isooctane in CPP30 samples at 20 C is slightly smaller than the experimental value. Under other conditions, the model values of toluene migration in three samples of LDPE30, CPP30 and RCPP70 are both greater than or approximately equal to the experimental values. (4) ordinary plastic composite membrane (LDPE, CPP) and steamed plastic composite membrane (RCPP) are treated by migration conditions. In the infrared absorption spectrum of the three samples, some absorption peaks move to the low wavelength direction, indicating that the intermolecular force in the membrane decreases. The scanning electron microscope shows that the microstructure of the sample section after treatment is wrinkled and distorted, and the microstructure changes of the CPP film are slightly smaller than that of the LDPE film, and the isooctane and the olive oil are micro to the ordinary film and the cooking membrane. DSC analysis showed that the melting point and enthalpy of the film decreased after the treatment, indicating that the thermal stability of the membrane became worse, the crystallinity decreased, and the change amplitude of the CPP film was less than that of the LDPE film. The crystallinity of the membrane in the RCPP sample without contact fluid was reduced, but the thermal stability was small, and the TG curve showed LD after treatment. The thermal decomposition temperature of PE and CPP samples decreased and the thermal stability decreased. The thermal stability of RCPP samples changed little after high temperature cooking.

【学位授予单位】：沈阳农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TS206.4

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