Physicochemical Properties Of Pectin/Chitosan Films And Their Applications As Coating For Apple

Today,the food industry's important challenges are to develop environmentally friendly,green,and intelligent food packaging materials to avoid environmental problems caused by the use of synthetic polymer packaging materials.Edible coating of biodegradable materials is considered the most trusted technique for storage fruit and vegetables,excellent alternative way to chemically synthesized preservatives,more effective in prolonging various agricultural products' shelf life and inhibiting disease growth on the fruit surface.Biodegradable materials have several characteristics,including biocompatibility,biodegradability,renewability,non-toxicity.Therefore,in recent times the researches are focused on edible packaging as a substitute material to minimize or avoid non-biodegradable packaging.Chitosan and pectin are considered promising biomaterials in developing edible films and eco-friendly due to their various characteristics such as films-forming,biodegradable,and non-toxic,although pure CH or PE have apparent drawbacks such as weak barriers and unsatisfied mechanical properties.Based on the facts mentioned above,the present study focused on the effect of high methoxyl apple pectin(64%esterification degree)and two types of chitosan and their blend as edible films and thereof application to protect the apple fruits from the gray mold diseases during the storage.The main parts of this study are as follows:Studying the physicochemical characteristics for edible films from high-methoxyl apple pectin and chitosan and their blends at different mass ratios;Tuning the physicochemical properties of apple pectin films by incorporating chitosan/pectin fiber;Studying the effect of pectin,chitosan,and their blend as a coating for apple fruits to prevent the gray mold disease.The main findings for this study as follow:(1)The effect of the blend films of CH with a lower degree of deacetylation(67.9%DD)and apple pectin at varying mass ratios comparing with pure PE and CH films were studied;the results showed the following;Structurally,numerous small pores evenly distributed in PE film while,there are big cavities unevenly scattered in CH film,and CH film was shown semi-crystalline structure but PE and blend films are totally amorphous structure,the two individual films presented comparable values in water content and solubility to blend films.The CH film showed lower water vapor permeability and surface wettability.These blend films' parameters decreased with the CH level;the blend films(PE1-CH1)and(PE1-CH2)exhibited high transparency 2.54 and 2.82 mm-1,respectively.In contrast,the PE film showed lower transparency(1.76 mm-1).Mechanically,the PE film presented higher values in stretchability and tensile strength than the CH film.Moreover,in different blending ratios,synergistic effects were found with several CH/PE blend film characters,especially in transparency and mechanical properties.These synergistic effects were ascribed to the intermolecular electrostatic interactions between CH and PE;From the above results for this studying,the best blend was PE1-CH1 for the combination than the others,which can be used as edible film/coating to prolonging the storage life and preserving the quality of the fruit and vegetables during the storage.(2)The natural fibers were produced from apple pectin and chitosan(80-95%DD).The feasibility of incorporating these fibers into the pectin films was explored to overcome pectin films' defects and enhance its different properties.Micron-scale novel artificial CH/PE fibers in needle,spindle,or whisker shape with a diameter around 25?m were fabricated via a shearing regime in virtue of electrostatic complexing.The incorporation of CH/PE fiber(mixture)and its size-fractioned portions(small and large)substantially changed PE films in diverse ways;the results observed the following;Structurally,the fiber-incorporated films were heterogeneous with the fibers concentrated in the upper layer,although they presented similar FT-IR spectra and XRD pattern to PE film.Regarding the film performance,the incorporation of CH/PE fibers,especially the small portion,rendered the PE film with higher values in water-proof ability,thermal stability,break resistibility,stretchability,and UV blocking capacity.More importantly,this work provided an innovative strategy that can enhance and improve edible films' performance.(3)The study carried to compare the effect of both pectin and chitosan and their blend as a coating for apple fruits;The results showed that the gray mold began to grow after 10 days from the inoculation,and the growth continued until the end of storage,all the coating treatments(PE,CH,and PE/CH)used before the inoculation by B.cinerea showed significant differences in all parameters and worked as barrier for the gray mold disease compared to control samples(inoculated by B.cinerea only),.The PE/CH blend coating before the inoculation by B.cinerea showed the better performance to prevent the gray mold than pure pectin and chitosan coating;also a significant reduction of the weight loss(13.12%)and respiration rate for CO2 production and maintaining the apple firmness(16.24 N)followed by the CH coating(12.93 N).These result showed that the interaction between the pectin and chitosan not only improve the performance of the films but also helpful to the prolong the shelf life of fruits and inhibits the microbial growth than the pure chitosan or pectin coating,therefore the PE/CH blend coating could be used for prevention the gray mold disease caused by B.cinerea and maintaining the internal quality for the fruits.Based on the above results,the combination of the pectin and chitosan showed a good effect as edible films and protecting the apple fruits from the gray mold diseases than the pure chitosan and pectin as a coating;also,the pectin incorporated with chitosan can produce natural fiber that used to boost the properties of the edible films.