Fabrication And Applications Of Fresh-keeping Edible Coating Based On Host-guest Layer-by-layer Self-assembly Technology

Along with people's further attention to the high quality of life,edible fresh-keeping coating is developing rapidly.Several coatings were fabricated with chitosan based on layer-by-layer self-assembly technology.The structure,morphology,mechanical properties,transparency and gas barrier properties of the coatings were characterized.Investigation was made on the effects of the preharvest coating on the postharvest storage property,release performance of the antibacterial agent,and sensing applications of coatings.The main contents were as following:1)Edible coatings based on sodium chitosan(CS)and dialdehyde starch(DS)were employed on apples before the harvest and discussed the postharvest storage property.Coating can effectively reduce the weight loss of apple,about 59%less than the control ones.At the same time,signs of mould almost never happen.2)Edible self-healing coatings based on sodium alginate(SA)and l-menthol-beta-cyclodextrin-graft-chitosan were developed.Their mechanical properties and morphological studies indicated that the addition of l-menthol resulted in a transparent,smooth,and dense coating with better mechanical features and self-healing properties.The self-healing efficiency of the coatings containing l-menthol was about 59%and the tensile strength was about 63%higher than the control ones.In addition,the coatings realized a controlled liberation property owing to the liberation of l-menthol incorporated in?-cyclodextrin.The coatings effectively retained fruit firmness and reduced the weight loss of coated apples throughout a 30 d storage.Although the coating we prepared can reduce the weight loss of peaches during preservation period,peaches becomed putrid easier.3)The preservation effect of figs based on CS/DS coating with l-menthol was analyed.Weight loss of the coated figs increased with the content increasing of l-menthol in the coating.Effects of bagging on figs appearance and postharvest characteristics were studied.The results showed that bagging would make the figs rot easier.(4)We have demonstrated the fabrication of CD-X film based on Lb L technique.The morphological and structural features,mechanical properties,and barrier performance of oxygen and carbon dioxide of coatings are investigated.The incorporation of l-menthol to the films decreased the maximum force of films fracture and the displacement of maximum force point.Transmittances of all the films at wavelength of 600 nm were more than 95%.Furthermore,transmittances of ultraviolet light were low which is advantageous for protecting fruits from harm.The O₂ and CO₂ barrier performances of CD-0.1 films and CD-0.2 films were better compared with other two ones.The gas barrier performance of films could slow down the intensity of fresh fruit respiration.These results indicated that CD-0 film and CD-0.4 film slow down the cell wall degradation,fruit ripening,and softening more effectively during shelf-life of banana.5)The CD-Al sensor based on CS/DS to monitoring the electromechanical properties during fruit ripening was exploited.The electromechanical properties monitored by CD-Al sensor was in accordance with the respiration rate and ethylene production.This type of gas-film-Al sensor provides a promising idea for low-cost and portable sensing device.