Preparation Of Pumpkin-based Edible Wrapper

As people’s environmental and health care consciousness increase, theenvironmental friendly packaging materials which made of biomacromolecule arewidely used in food packaging. Vegetable wrappers which are made of fruit andvegetable purees are meaningful to the develoption of edible packaging and themultipurpose use of fruit and vegetable. The study of vegetable wrappers has becomea hotspot in the field food and packaging.Pumpkin has high nutritional and medical value. Pumpkin purees have lowfilm-forming property, for pumpkin purees can not be made into vegetable wrapperswithout additives. To modify the seriflux can improve the properties of thepumpkin-based edible wrappers. Therefore, it’s essential to do some research on theformulation and technology of the pumpkin-based edible wrappers.In this study, we added sodium alginate as thickener, glycerin as plasticizer,modified nano-TiO2as reinforcer and bacteriostat, to prepare edible pumpkinwrappers, and ultrasonic/microwave assisted treatment was used to modify thesolution. The formulation and technology was optimized. The results and conclusionsof this work were separated in five parts as follows:(1) Prepared the pumpkin-based edible wrapper. To evaluate the effect of massfraction of pumpkin, sodium alginate, and glycerin on the tensile strength (TS),elongation at break (E), water vapor permeability (WVP) and oxygen permeability(OP), oil permeability (Poil) of pumpkin-based edible wrapper. The appropriateadding ranges of the factors above were obtained. Based on the results, chose thesensory score as index and orthogonal experimental design was used to perform thestatistical analyses, through which we got the following results:①The maininfluence factor of the sensory quality of pumpkin-based edible wrapper was pumpkin＞glycerin＞sodium alginate.②The optimal technology parameters were: pumpkin15%(w/w), sodium alginate0.15%(w/w), glycerin0.1%(v/w).(2) Modifyimg the solution by ultrasonic and microwave separate and synergistictreatment. The modification treatments were carried out to study the influence onmechanical properties and barrier properties. Based on the single factor experimentresults, quadratic general rotation union test design was used to perform the statisticalanalyses. The optimal modifying parameters were: microwave treatment power was500W, microwave treatment time was20min, and ultrasonic treatment time was20min. In addition, ultrasonic/microwave assisted treatment provide further supportfor the properties of pumpkin-based edible wrapper, which were in agreement withthe changes in molecular interactions detected by SEM analysis of the surface morphology.(3) Ultrasonic-microwave assisted treatment has been used to modify nano-TiO2,and got modified nano-TiO2which that contained smaller particle size, larger surfacearea, and more free hydroxyls on the surface. Nano-TiO2and modified nano-TiO2were added to modify the pumpkin-based edible wrapper, which affected TS, E, WVP,OP and Poil. It was found that modified nano-TiO2has a better strengthen to themechanical properties and barrier properties of the pumpkin-based edible wrapper.When the additive amount of modified nano-TiO2(w/w) was0.15%-0.20%, the TS, E,WVP, OP and Poil were at a better range. The wrappers’ surface morphology wereobserved by SEM analysis. The pumpkin-based edible wrapper which added modifiednano-TiO2had the smoothest surface and dense structure.(4) Filter paper diffusion method was separately used to determine inhibitoryeffect, minimum inhibitory concentration and minimal bacteriocidal concentration ofnano-TiO2and modified nano-TiO2against Escherichia coli. The disk inhibition zoneassay was used to qualitatively evaluate the antimicrobial activity of thepumpkin-based edible wrapper.①Nano-TiO2and modified nano-TiO2could inhibit the growth of Escherichiacoli. The data show that the antimicrobial activities were in the following order:modified nano-TiO2> nano-TiO2. The CMBCof nano-TiO2and modified nano-TiO2were125μg/mL and250μg/mL.②Antimicrobial activities of modified pumpkin-based edible wrapper wentalong with the mass fraction of nano-TiO2; the antimicrobial activities of modifiednano-TiO2were stronger than that were not modified under the same concentration.(5) Response surface of design expert7.0software was used to perform thestatistical analyses. The mathematical models of the tensile strength (Y1), thepercentage elongation at break (Y2), water vapor permeability (Y3), oxygenpermeability (Y4) and the oil permeability (Y5) were obtained using mass fraction ofpumpkin (X1), mass fraction of sodium alginate (X2), mass fraction of modifiednano-TiO2(X3) and ultrasonic-microwave assisted treatment time (X4). The thesisgained the optimal technology parameters. The optimal technology parameters were:pumpkin21.48%(w/w), sodium alginate0.19%(w/w), modified nano-TiO20.11%(w/w), ultrasonic-microwave assisted treatment time32.5min. Under the condition,TS, E, WVP, OP and Poil had the optimal value:13.26MPa,24.36%,9.8010-11g·m-1·s-1·Pa-1,4.36cm3/cm2·24h·0.1MPa and3.23g·mm/m2·d. The verificationexperiment had proved the result feasible.