The Effect Of Chitosan And Nano-TiO₂ On The Mechanical Strength And Barrier Properties Of The Starch Composite Film And The Application Of The Composite Film In The Reservation Of Fruits And Vegetables

Using potato starch as the film-forming substrate,chitosan and nano TiO₂ as the reinforcing phase,1%(w/w)chitosan acetic acid solution and 5%(w/w)potato starch gelatinization liquid were mixed by solution blending method,After mixing chitosan and starch uniformly according to the ratio of 4:6(w/w),adding 0.1%(w/w)nano TiO₂ to cast into a film,and prepare potato starch single film(P),potato starch/chitosan composite film(P+Ch),potato starch/nano TiO₂ composite film(P+TiO₂),potato starch/chitosan/nano TiO₂composite film(P+Ch+TiO₂).The structure and morphology of the composite film were characterized by SEM,FTIR and XRD,and the effect of chitosan and nano TiO₂ on the film-forming properties of potato starch was discussed;by determining the oxygen barrier,water vapor permeability,tensile strength and fracture of the composite film Elongation,analysis the effect of the compound addition of chitosan and nano TiO₂ on the barrier properties and mechanical properties of potato starch film;applying the compound coating to 7 kinds of fruits and vegetables,including cherry tomatoes,green peppers,radishes,broad beans,green beans,peas,and fresh slices of bamboo shoots,evaluating the property of composite coating film by measuring the changes in the nutritional indicators including peroxidase(POD)activity,weight loss rate,vitamin C,soluble sugar,titratable acid and malondialdehyde(MDA)content.Comparing the fresh-keeping effect of fruits and vegetables in the coating film group with the blank control group and PE film group to analyze the pros and cons of the coating film;finally,selecting the best combination by comparing the moisture permeability,mechanical strength and fresh-keeping effect of the four groups films.The results show that potato starch,chitosan and nano TiO₂ have good compatibility;the composite addition of chitosan and nano TiO₂ can effectively improve the water vapor permeability and oxygen barrier properties of the starch film,and increase its mechanical strength;Among the four groups of films,nano TiO₂/chitosan/potato starch composite film shows the best physical and chemical properties,and its oxygen barrier is better than potato starch single film(P)and potato starch/chitosan composite film(P+Ch),Potato starch/nano TiO₂ composite film(P+TiO₂)is 43.38%,7.56%,19.14%higher;water vapor transmission rate is 32.41%,39.18%,30.89%lower;moisture absorption is 58.07%,22.66%,60.91%lower;The mechanical strength is 47.68%,43.75%,45.89%higher.After 12 days of storage at room temperature 15?,the weight loss rate of the fruit and vegetable coating group was lower than that of the blank control group,the content of vitamins,soluble sugar and titratable acid were higher than that of the control group,and the content of malondialdehyde and POD activity were lower than that of the blank control group.Nano TiO₂/chitosan/potato starch composite coating(P+Ch+TiO₂)showed the best fresh-keeping effect in the coating treatment group.Conclusion:The blending of chitosan,nano TiO₂ and potato starch to make film can effectively improve the structure and performance of starch composite film,enhance the mechanical strength and barrier properties of starch film,and improve its storage and preservation effect;chitosan,nano TiO₂ together addition effect is better than the addition of a single component;among the four groups of films,the nano TiO₂/chitosan/potato starch composite film(P+Ch+TiO₂)has the best physical and chemical properties and the best fresh-keeping effect.