Starch-Based Films Reinforced And Functionalized With Different Rigid Particles

Packaging plays a key role in food processing and preservation.It protects food from harsh environmental conditions and contaminations.It also helps in extending shelf life and enhancing the quality of the product.Edible films have been applied in the food industry as a new packaging material as an antimicrobial and antioxidant for food safety and nutritional improvement.These packaging materials acting as a barrier for gases and volatile compounds,water,and inhibit the growth of a pathogenic microorganism in the vicinity of the packaging materials.Starch-based edible films have gained attention in filmmaking industries due to its worldwide availability,processability,and low cost.It has been considered a good polymer having the potential to produce edible and biodegradable films.Different methods are used to develop starch based films such as film casting method,injection or blow molding techniques.Many studies have been reported on the application of starch from different sources as a raw material for edible film formulation and formation.However,its hydrophilic nature hindering its application to use as a matrix to develop starch based films.Owing to hydrophilic nature and affinity to moisture uptake film shows poor mechanical and barrier properties particularly tensile strength and water vapor permeability.To overcome these limitations starch matrixes reinforced with different organic or mineral filler.These filler reinforced bio-polymeric matrixes lead to the development of films with improved properties due to the synergic effect between the components.Application of nanoparticles from different resources also shows efficiency in improving the thermomechanical and physiochemical properties of starch based films.The present study was designed to evaluate the effect of different fillers(micro starch,and cellulose crystals,corn and wheat hulls,pomegranate peel,and apricot and walnut shells)from agricultural byproduct on the hydroxypropyl starch matrix in the presence of polyethylene glycol as a plasticizer.Starch based films were prepared by solution casting method after gelatinization at 99 ~oC the fillers from different sources were added in different percentages and dried in an oven at 37 ~oC.After drying the film materials were investigated through different techniques to determine the relationship between filler and matrix and the effect of filler on the microstructures and performances of the starch-based composite films.Effect of the different fillers,content and particle size on microstructure,mechanical,thermal,and barrier and water vapor resistant properties of the starch-based films were investigated through scanning electron microscope(SEM),optical microscope(OM),X-ray diffraction(XRD),water vapor transmission rate(WVTR),dynamic mechanical analysis(DMA)thermal gravimetric analysis(TGA)tensile testing and impact testing.The obtained results showed that the addition of all rigid particles increased modulus,tensile strength and impact strength of starch films.Corn and wheat hulls as a filler also improved the barrier properties particularly WVTR of the starch based films.OM observation showed that the geometric and crystalline structures of reinforced fillers remained same in the films after processing.Scanning electron microscopic observation indicated good compatibility between the starch matrix and the reinforcing fillers due to the same chemical units(glucose).Cellulose crystals have higher thermal stability than that of starch crystals;this provides better processability and superior mechanical properties to starch films filled with cellulose crystals.Since all the components used for the preparation of the films are from food resources,so the films can be used for edible purposes.After freeze-drying pomegranate peel was incorporated in the starch matrix and the antimicrobial activity,microstructure and performance of developed films were investigated.Pomegranate peel not only inhibited the growth of gram-positive(S.aureus)and gram-negative(Salmonella)bacteria,it also increased impact and tensile properties of the reinforced film.The apricot and the walnut shell reinforced film also showed reduced WVTR,improved tensile and UV barrier properties,XRD indicated that the apricot and walnut shell not only retained their crystalline structure in the film but they also strengthening the peak intensity of the film.This phenomenon can be used to explain the mechanism of mechanical reinforcement.Since all the components used in the preparation of the film are food graded ingredients so the film developed in this work can be used for food package.