无火焰食品自加热器贮存性能下降机理与改进方法

Mechanism and Improvement Methods of Performance Degradation of Flameless Food Self-heaters during Storage

摘要:

该研究以Mg/Fe型无火焰食品自加热器为研究对象，探究其在高温高湿条件下（55 ℃、85% RH）加热性能变化，结合SEM-EDS和热重分析手段揭示性能下降机理，改进贮存方法。结果表明，高温高湿条件下，自加热器加热性能随贮存时间延长逐渐下降，贮存28 d，启动时间增加至68.34 s，高温维持时间降低至8.52 min。Mg粉颗粒崩解，表面疏松，有明显结晶，O元素相对含量增加至52.82%、反应前Mg粉损失程度增加至7.71%，水汽、氧气与Mg粉接触发生氧化和水合反应导致性能下降。相同包装材料下，添加干燥剂可延缓性能下降速率，贮存28 d时，启动时间为60.84 s，高温维持时间为9 min；高阻隔包装材料（B2，PET/氧化铝/PE）在贮存前期降低Mg粉氧化和水合速率，贮存42 d时，启动时间为43.83 s，高温维持时间为11.01 min，O元素相对含量为37.29%。综上，高温高湿条件下，水汽、氧气与Mg粉接触发生氧化和水合反应引起自加热器中活性镁含量下降，高阻隔包装材料（B2）及干燥剂，可延长使用寿命，上述内容可为自加热器的实际贮存方式提供理论基础。

Abstract:

To explore the heating performance changes under high temperature and high humidity storage Mg/Fe flameless food self-heaters were subjected to high temperature and high humidity (55 ℃, 85% RH) conditions SEM-EDS and thermogravimetric analysis to reveal the mechanism performance decline and improve storage method. The results showed that the heating performance of the self-heater decreased over time when stored under high temperature and high humidity condition. When stored for 28 d, the startup time was increased to 68.34 s, and the high temperature maintenance time was reduced to 8.52 min, Disintegrated particles, loose surfaces, and crystallization were observed in Mg powder. The relative content of O element and the pre-reaction loss of Mg powder were increased to 52.82% and 7.71%, respectively. The oxidation and hydration reactions of magnesium powder with water vapor and oxygen led to performance degradation of the self-heaters. Given the same packaging material, adding desiccant delayed performance degradation and resulted in a startup time of 60.84 s and a high-temperature maintenance time of 9 min. High-barrier packaging materials (B2, PET/alumina/PE) effectively delayed the oxidation and hydration rate further in the early storage period; when stored for 42 d, the startup time was 43.83 s, the high-temperature maintenance time was 11.01 min, the O element content was 37.29%. Therefore, the performance degradation of self-heaters is mainly attributed to the decrease of active magnesium content due to oxidation and hydration reactions of Mg powder with water vapor and oxygen. The shelf-life of self-heaters can be improved effectively by using high-barrier packaging materials (B2) and desiccants. The above findings can provide a theoretical basis for developing practical storage methods for self-heaters.