Qingfeng Yang

The water absorption of polyvinyl alcohol (PVA) freeze-dried porous polymer is critically influenced by its molecular structure. The hydrolysis degree and molecular weight of PVA were identified as key factors in the design of freeze-dried porous polymers for enhanced structure and stability. The complex interactions between water absorption and structural characteristics in freeze-dried porous polymers were investigated. This was achieved by varying the degree of hydrolysis and molecular weight of the PVA. The results indicate that as the degree of PVA hydrolysis increases, the water absorption and structural stability of the freeze-dried porous polymer are significantly improved. These performance enhancements are attributed to the synergistic effects of hydrogen bonding interactions and molecular chain entanglement between PVA-sodium polyacrylate (PAAS) chains and PVA-PVA chains, collectively forming a denser and more stable three-dimensional network structure. Additionally, the incorporation of high molecular weight PVA significantly reduced the water absorption capacity of the freeze-dried porous polymer. However, freeze-dried porous polymers prepared using low molecular weight polyvinyl alcohol exhibit poor structural stability. Specifically, when the PVA molecular weight is 7200-8100, and the degree of hydrolysis is 99%, the freeze-dried porous polymer exhibits a maximum porosity of 92%, a density of 82 mg/cm³, and a water absorption capacity of 38 g/g. Overall, this work provides the theoretical basis and technical support for its application in absorbent pads.

To address spoilage and quality deterioration, this study evaluated the synergistic effects of the electrostatic field (EF) combined with packaging (polyethylene, PP; vacuum, VP; modified atmosphere, MAP) on the preservation of Yorkshire pork (hind leg) during controlled freezing-point storage (−2.0 ± 0.5 °C) for 32 days. The results showed that EF treatment significantly enhanced the water-holding capacity of PP-packaged pork, reducing storage loss by approximately 37.89% by day 32 (p < 0.05), and inhibited microbial growth, maintaining total viable counts below 6.00 log₁₀ (CFU/g) (p < 0.05). EF also reduced the relative abundance of spoilage organisms such as Pseudomonas. A synergistic effect between EF and VP/MAP was observed in the optimization of the microbial community structure. Spearman correlation analysis revealed that Pseudomonas abundance was positively correlated with TVB-N and storage loss, linking it mechanistically to quality deterioration. Furthermore, VP and MAP alone were superior in delaying lipid oxidation (TBARS < 0.5 mg MDA/kg) and maintaining color stability. This study provides key process parameters and a theoretical basis for applying EF-coupled packaging in the industrial cold chain.