Edible films based on chitosan, coix seed starch (CSS), nano zinc oxide (ZnO) and Artemisia annua essential oil (AO) were obtained through solvent casting method. Physico-chemical, biological properties and structures of the edible film were analyzed and the preservation effect of it on the quality of cold-stored pork was also investigated. Fourier-transform infrared spectroscopy (FTIR) indicated that some possible intermolecular interactions could exist between film matrix and ZnO or AO. Scanning electron microscope (SEM) and thermogravimetry (TG) showed that ZnO and AO had good compatibility with the film biopolymers, no any phase separation. Results suggested that appropriate content of ZnO could enhance the film's compactness. Tensile strength (TS), barrier properties and antibacterial activities of the film was significantly enhanced with 5% ZnO was added. Incorporation of AO into the edible film decreased the TS, but increased the flexibility, barrier properties, antibacterial and antioxidant activities. When content of ZnO and AO were 5% and 8%, the physico-chemical, biological properties of the edible film could reach optimum. For pork preservation, pH, thiobarbituric acid reactive substances (TBARS), total viable count (TVC), and total volatile basic nitrogen (TVB-N) values of the pork which treated with 5% ZnO-8% AO film were significantly lowest (p ≤ 0.05) than other groups. Therefore, this edible film system has potential as food packaging materials.
Various natural deep eutectic solvents (NaDESs) were synthesized and coupled with steam distillation to extract wormwood essential oil. Structural (Fourier-transform infrared) and physical (pH, conductivity, differential scanning calorimetry) characterizations of the DESs were performed. The binding sites, types and intensity of interaction forces of the NaDESs were analyzed using quantum chemical calculation. Wormwood essential oil was collected using NaDES-coupled steam distillation. The yield of essential oil was calculated according to the amount of essential oil collected. The types and area percentages of the peaks of the main active substances were analyzed using gas chromatography-mass spectrometry. Among the prepared NaDESs, l -carnitine-malic acid DES afforded the highest yield and the most active substance types (area percentage ≥ 2 %); the process was superior to steam distillation coupled with water, NaCl, and cellulase. Single-factor experiments showed that the distillation efficiency was optimal with a DES concentration of 50 wt%, solid–liquid mass ratio of 1:6, and distillation time of 10 h. Scanning electron microscopy was used to further explore the extraction mechanism. The structure of the plant cell wall was most severely damaged by l -carnitine-malic acid DES, which increased the extraction efficiency and the types of active substances (area percentage ≥ 2 %). Therefore, NaDES-coupled steam distillation is an efficient, green, feasible, and innovative method for extracting wormwood essential oil.
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