Preparation And Film-forming Characterizations Of Lentinus Edodes Stems Fiber

Edible mushroom can be regareded as a new source of dietary fiber,however,its by-products are usually discarded as the waste.Therefore,how to effectively utilize its by-products and expand the industrial production of edible mushroom fiber edible films will become a research focus.In this study,by following rough handling including soaking and grinding with colloid mill,and further processing including hot water(80℃,3 h)and NaOH solution(1%and 5%;room temperature for 12 h;80℃ for 3 h,respectively),five fibers were prepared from Lentinus edodes stems.The composition and constitutive properties were analyzed by HPLC,XRD,FTIR,and the functional properties were characterized by water-holding capacity,oil-holding capacity,swelling capacity.The results showed that five samples were same in the composition including insoluble fiber,rude protein,ash,and monosaccharide(glucose,amino glucose,mannose and galactose and rhamnose),but different in the proportion,where the sample prepared by hot water had the lowest proportion of insoluble fiber(63.83%±0.92%)but the highest proportion of crude protein and ash(12.68%±1.01%and 5.37%±0.07%,respectively).Moreover,the five samples have similar amorphous structure and low crystallinity.As the functional properties,the samples prepared by hot water had the best water-holding capacity with the oil-holding capacity of five samples all showing poor and swelling capacity not showing significant differences.In order to improve the colour of Lentinus edodes stems fibers,by choosing four decolorizers(hydrogen peroxide,sodium hypochlorite,chlorine dioxide,sodium hydrosulfite)with suitable concentration gradient,pH,fiber concentration,time and temperature,the bleached fibers were prepared from Lentinus edodes stems and characterized by the yield,whiteness,water-holding capacity,oil-holdng capacity and swelling capacity.The results showed that there was a negative relationship between the yield and the concentration of hydrogen peroxide,with the yield decreasing from 74.53%to 31.97%.On the contrary,there was a positive relationship between whiteness and the concentration of all decolorizers,thereinto with the concentrations of 5%and 6%of hydrogen peroxide showing the highest whiteness(17.94%±0.97%and 18.03%±0.52%,respectively).Besides the dried Lentinus edodes stems,the dried postmature Flammulina velutipes was choosed as the contrast material.By following colloid mill,PFI mill and 5%hydrogen peroxide,four edible mushroom fibers were successfully prepared,and further prepared to edible films by vaccum suction filtration.The performances of four edible films were investigated by the mechanical properties,water vapor permeability,oxygen barrier properties,film integrity and loss rate in water,transparency,colour and thermal stability.The results showed that the surface of the bleached fiber films was more compact with colour greatly improving but the transparency decreasing.Thereinto,the tensile strength of the Lentinus edodes stems bleached fiber film was up to 24.37±0.88 MPa with the elongation at break showing only 1.48%± 0.65%and the water vaporpermeability displaying 0.153 ±0.016 g·mm/m2·h·kPa.Moreover,the DSC and TGA indicated that the bleachingtreatment could improve the thermal stability of edible films.To sum up,by following grinding and bleaching,four edible mushroom fibers were successfully prepared from Lentinus edodes stems and Flammulina velutipes and further prepared to edible fiber film with certain mechanical strength and good barrier performance by vaccum suction filtration.This study not only improved the utilization of the edible mushroom by-products,but also provided technical support and theoretical basis with the industrial production of edible film.