| Fruits and vegetables are human’s important source of vitamins and minerals; however, fresh fruits and vegetables are perishable after harvest. So the method of how to prolong the storage period is necessary. Propolis contains a lot of antibacterial sterilization and antioxidant substances, nano-Si O2 has unique surface and interface effect, small size effect and quantum tunnel effect, gelatin can form film easily. Technological parameters using gelatin, propolis and nano-silica as base materials to make evenly spread nanometer propolis composite film were optimized, both ultraviolet irradiation and ultrasonic treatment were applied for film modification. In this study, propolis/nano-silica is used in the storage and preservation of cherry tomatoes. The process and results of relevant experiments about cherry tomato’s quality and its ability of anti aging and softening are as follows:1. The preparation and performance study of composite film. The influence of the added amount of gelatin, propolis and nano silica on tensile strength(TS), elongation(E), transmittance(T), water vapor permeability(WVP), oxygen permeability(OP) and carbon dioxide permeability(CP) of the composite film were firstly investigated by single factor experiments, and the data were then analyzed by the methd of principal component analysis. The results indicate that excellent comprehensive performance of the film was obtained by the formula that the added amount of gelatin, propolis and nano silica were 2 g/100 m L, 1.5 g/100 m L and 0.03 g/100 m L, respectively.2. Optimize the performance of propolis/nano-Si O2 composite film. Due to the main film-forming material of propolis/silica film is hydrophilic, therefore, the WVP of film is higher. To improve the performance of the film, ultraviolet and ultrasonic treatment were adopted to improve the overall performance of the membrane, respectively.The results show that TS and S of those films increased to a maximum and subsequently declined, E and OP decreased gradually and picked up again, T and WVP reduced first and bottomed out gradually with irradiation. When the UV treatment time is 16 h, there is an increase of 5.68 in S compared with the untreated control, and decreases of 2.88%, 4.33%, 5.26%, 2.13 g/cm·s·Pa and 0.5 cm3/(m2·24h·0.1MPa) in E, T, S, WVP and OP, respectively. Therefore, the composite films had good overall performance when the irradiation time was 16 h.Ultrasonic treatment could significantly improve the quality indexes of nano-propois film. Treatment with 200 W ultrasonic power for 15 min obtained, within the experimental range, the best quality film with TS as 13.00 MPa, E as 3.99%, T as 89.00%, S as 33.58%, WVP as 3.92 g/cm·s·Pa and OP as 1.13 cm3/m2·24h·0.1MPa.3. The impact of composite coating on the properties of cherry tomatoes. The laws for the development of physicochemical indexes and texture and sensory properties of cherry tomatoes coated by different coatings during 4℃ storage were studied. The results show that cherry tomatoes decay rate, weight loss, respiration rate(RR), softening, change of color, sensory properties in nano coating were notably inhibited. The activities of superoxide dismutase(SOD), peroxidase(POD), polygalacturonase(PG), pectinesterase(PME) and cellulose(CE) increased first and then decreased, however, the activities of polyphenol oxidase(PPO) gradually increased. Nano-propolis coating could keep a higher activities of free radical scavenging enzyme, and inhibit the activities of enzyme causing browning and softening. |
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