The uniaxial‐stretched poly(ε‐caprolactone) (PCL) films were prepared by a twin‐screw extruder. PCL1 and PCL2 with different thickness about 27 and 46 µm, respectively, wereused for equilibrium‐modified atmosphere packaging of strawberries at 5°C. The permselectivity were evaluated as well as its effects on the shelf life of strawberries. The results showed that the PCL2 films has asuitable water vapor permeability about 775 g/m2·24 hr and CO2/O2 permeability ratio about 9.7 at 5°C. The inner atmosphere of PCL2 can be adjusted by permselectivity of films and respiration of strawberriesto a suitable steady‐state with 1.2–4.2% CO2 and 3–7% O2 and no condensation appeared in PCL2 packages, which maintain quality of strawberries. The strawberry in PCL2 package was marketable by day 22. Compared with PCL1, polyamides/polyethylene (PE) and PE film, PCL2 film greatly enhanced the shelf life of strawberries.
Practical applications
The biodegradable uniaxial‐stretched poly(ε‐caprolactone) (PCL) films with certain thickness has a suitable water vapor permeability and CO2/O2 permeability ratio was used for equilibrium‐modified atmosphere packaging of strawberries. The film is able to adjust package spontaneously through its perm‐selectivity and respiration of strawberries to a suitable steady‐state inner atmosphere and maintain quality of strawberries. Compared with polyamides/polyethylene and polyethylene film, PCL film greatly enhanced the shelf life of strawberries to 22 days. The environment friendly film can be mass produced and easy to use for daily life. In the future, the gas permeability can be adjusted through thickness and draw ratio and make it suitable for different fruits. Thus, it can replace the traditional fresh‐keeping film and modified atmosphere packaging. Just wrap the fruits or other fresh products in the film without gas filling, can keep freshness of food and decrease the production and transportation costs of fresh food.
Chilled" meat is more nutritional, healthy and hygienic than the meat kept at ambient temperature. "Poly(propylene carbonate) (PPC) and poly(vinly alcohol) (PVA) were used to prepare biodegradable three-layer PPC/PVA/PPC films with high barrier and tensile properties. The potential benefits of the developed films were also evaluated on the shelf life of chilled meat products. Compared to PPC film, using 20 wt % PVA as an intermediate layer in PPC/PVA/PPC film remarkably enhanced oxygen barrier performance at 0 and 50 RH % by about 500 times, tensile strength by about 8 times, and Young's modulus by nine times, but no beneficial effect on water vapor barrier performance has been observed. A new "sandwich" type of completely biodegradable material with high barrier was obtained. The application of PPC/PVA20/PPC film as the packaging material of chilled meat was effectively kept the total viable count (TVC) and total volatile basic nitrogen (TVB-N) to acceptable levels in chilled meats until 19th day of storage at 4 C, however, the spoilage occurred within 11th and 14th days of refrigerated storage in term of TVC and TVB-N, respectively, in the chilled meats packed with only PPC. Herein, we report that PPC/PVA/PPC three-layer film can be a promising well-defined biodegradable material with excellent potential in chilled meat packaging.
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