Abstract:

Objective Fruits, vegetables and foods are easily contaminated by Escherichia coli, Staphylococcus aureus, mold and other common microorganisms. To extend the shelf life of fruits, vegetables and foods, it is of practical significance and application value to develop advanced packaging materials with antibacterial and fresh-keeping effects. In this paper, the feasibility of preparing antibacterial food-wrap membrane by electrospinning from gastrodia elata polysaccharides (GEP) and medical grade polyvinyl alcohol (PVA) was explored, which laid the foundation for the development of GEP nanofiber membrane with low-cost, green, antibacterial and fresh-keeping properties.

Method GEP was extracted by hot water extraction and aqueous two-phase extraction. The dry gastrodia elata blume was soaked in water, heated and extracted twice by induction cooker, and then the extract was cooled to room temperature, and the precipitate was collected after ethanol precipitation, and the GEP was extracted in ethanol/ammonium sulfate aqueous two-phase system, and the lower supernatant was taken out after standing for 24 h, and the crude polysaccharide of gastrodia elata blume was obtained by vacuum filtration, dialysis and freeze-drying. The purity, chemical structure, crystal structure, morphology and antibacterial properties of GEP were tested and analyzed. The GEP/PVA nanofiber membranes(with a GEP addition amount of 1.0%) were prepared by electrospinning under different voltages, and their antibacterial properties, surface morphology, fiber fineness, tensile properties, and fresh-keeping effect on strawberry were tested and analyzed.

Results The extraction rate of GEP obtained using a combination of hot water extraction and aqueous two-phase extraction is 2.0%, with a content of 82.22%, and it exhibits a typical infrared spectrum curve of polysaccharides. The GEP show that it has amorphous structure and smooth surface. The antibacterial property of GEP was tested by agar plate diffusion method, and 200 mg/mL GEP solution had good antibacterial performance against Escherichia coli and Staphylococcus aureus. The antibacterial performance of GEP/PVA spinning solution was tested by absorption method, and the antibacterial rate of GEP/PVA(1.0% GEP) spinning solution against Escherichia coli was more than 99%. When the electrospinning voltage is 18 kV, the GEP/PVA nanofiber membrane is well formed, the average fiber diameter is about 320 nm, and the tensile breaking strength of the membrane is up to 247.59 cN when the membrane thickness is 0.09 mm; The preservation effect of GEP/PVA nanofiber membrane was the best and the weight loss rate was the lowest at 5 ℃ in the refrigerator environment. The preservation effect of GEP/PVA nanofiber membrane could extend the shelf life of strawberry for 3 d at room temperature.

Conclusion In this paper, the dry gastrodia elata blume was used as raw material to extract crude polysaccharide by hot water extraction and aqueous two-phase extraction, and the GEP/PVA nanofiber membrane was successfully prepared by electrospinning technology with PVA as the film-forming carrier. When the electrospinning voltage was 18 kV, the GEP/PVA nanofiber membrane was well formed. GEP/PVA nanofiber membrane has good fresh-keeping effect, which can effectively slow down the evaporation and loss of water, and prolong the shelf life of strawberries for 3 d at room temperature. The successful preparation of GEP/PVA nanofiber membrane not only realizes the application feasibility of GEP in fruit and vegetable preservation, but also contributes to the development of plant polysaccharide fruit and vegetable and food packaging materials with low-cost, green environmental protection, antibacterial preservation and excellent performance.

Key words: gastrodia elata polysaccharide, aqueous two-phase extraction, electrospinning, nanofiber membrane, antibacterial property, food-wrap membrane, polyvinyl alcohol