Effect of poly(L-lactic acid)/poly(ethylene glycol)-poly(L-lactic acid) block copolymer blend film on preservation of Chinese winter jujube (Ziziphus Jujuba Mill. cv. Dongzao)

Abstract

The effect of poly(L-lactic acid)/poly(ethylene glycol)-poly(L-lactic acid) block film on preservation of Chinese winter jujube (Ziziphus Jujuba Mill.cv.Dongzao) was investigated. Eight arm poly(ethylene glycol)-poly(L-lactic acid) block copolymer (8-PEG/PLLA) and net structure 8-PEG/PLLA (NET-PEL) were successfully synthetized by ring-opening polymerization, and different percentages (5, 10, and 20 %) of them were blended with PLLA to prepared blends films. Mechanical properties, modulated different scanning calorimetry (MDSC), gas and water vapor permeability results showed that 8-PEG/PLLA and NET-PEL block copolymer greatly increased the toughness of blend films, could be decrease PLLA segment glass transition temperature (T_g)from 59.5 °C to 41.6-46.7 °C and cold crystallization temperature(T_cc)from 89.4 °C to 73.5-77.7 °C, and increased the oxygen (O₂), carbon dioxide (CO₂), and water vapor transmission rate. The an appropriate gas concentration [O₂ (2.56-3.51 %), CO₂ (5.05-5.56 %)] was created inside the PLLA/NET-PEL20% (NEPEL20)group, which could restrain increase of total soluble solids (TSS), malonaldehyde content. The firmness, color luminosity (L*), total phenols, and ascorbic acid were maintained at higher level，and kept its commercial value after 40 days of storage. The present data indicated that treating post-harvest winter jujubes with NEPEL20 MAP packaging was an effective method for preservation of postharvest winter jujube.

Keywords: Chinese winter jujube (Ziziphus Jujuba Mill.cv.Dongzao); Modified atmosphere packaging; Poly(L-lactic acid).