| In recent years, current industries have shown an increasing interest in replacingnon-degradable materials by renewable source-based environmental-friendly ones,without impairing their properties. Edible packaging appears as an excellentalternative to synthetic materials because it is abundant, renewable, low cost andbiodegradable. The objective of this study is to prepare chitosan/modifiedmicrocrystalline cellulose edible peanut shell membrane. First, the extraction ofpeanut shell cellulose and determination of cellulose’s basic parameters was studied,and the process conditions parameters of peanut shell cellulose’s extraction was alsooptimized. Secondly, peanut shell microcrystalline cellulose was prepared throughacid hydrolysis, and their basic parameters were measured, such as particle size, thusoptimal process parameters of peanut shell microcrystalline were obtained. Thirdly,etherification modification for peanut shell microcrystalline cellulose was done, andthe effect of different etherification conditions on modified peanut shellmicrocrystalline cellulose’s substitution degree was determined. Finally, modifiedpeanut shell microcrystalline cellulose/chitosan films were prepared, and the effect ofdifferent conditions on the edible films’ properties was studied. Specific researchcontents and conclusions are as follows:(1) Acid-alkali method for preparation of peanut shell cellulose was used. Theinfluence factors included mass fraction of alkali, alkaline solution temperature,alkaline hydrolysis time, acid hydrolysis temperature, acid hydrolysis time, and theindex included yield of peanut shell cellulose, swelling capacity and water holdingcapacity, process condition of preparation of peanut shell cellulose and optimumprocess parameters were studied; Orthogonal experimental design and analysis wereapplied to optimize the conditions for the preparation of peanut shell cellulose. Theresults showed that the optimized parameters were alkali mass fraction (2.5%), alkalitemperature (70°C), alkali time (1h), acid temperature (50°C), acid time (2h). Underthe conditions, its yield was52.8%, SWC was5.17mL/g, WHC was6.63g/g, thecellulose had a high activity.(2) The mechanism of acid hydrolysis was discussed. Select acid mass fraction,acid solution temperature and time of acid hydrolysis as influencing factors, yield,degree of polymerization, swelling capacity, water holding capacity,median-particle-size and content as indicators, investigate the technology conditionsof the preparation of peanut shell microcrystalline cellulose; Orthogonal experimentaldesign and analysis were applied to optimize the conditions of peanut shell cellulosemodified by acid. The results showed that the optimized parameters were acid massfraction (6%), acid temperature (60°C), acid time (1.5h). Specific parameters were asfollows: yield was61.3%, degree of polymerization was135, swelling capacity was 13.64mL/g, water holding capacity was15.16g/g, median-particle-size was44.67μm,content was85.01%.(3) SEM results showed peanut shell microcrystalline cellulose was stubbycylindrical shape, part of microcrystalline cellulose aggregated, the surface areaincreased, while the surface can be observed random cracks; FT-IR results showed themicrocrystalline cellulose has the same characteristic peaks and strong absorptionpeaks as cellulose, it did not introduce new functional groups, but there was a hugechange in physical and chemical properties.(4) Under microwave irradiation, the modified peanut shell microcrystallinecellulose was prepared by the two-stage alkali addition process. Select microwavepower, the amount of monochloroacetic, proportion of alkali and etherificationtemperature as influencing factors, the DS of the modified peanut shellmicrocrystalline cellulose as an indicator, analyze that how different conditionseffected DS. Using the response surface experiment design, the results showed thatthe optimized parameters were microwave power (195W), the amount ofmonochloroacetic (3.49g), proportion of alkali (2.61:1) and etherification temperature(71℃), under the conditions, DS was0.886.(5) SEM results showed the modified peanut shell microcrystalline cellulosewas easily aggregated, The hydrogen of molecular structure was replaced bycarboxymethyl, the surface turned rough and had folds, cracks, breakage; FT-IRresults showed that the modified peanut shell microcrystalline cellulose appeared astrong absorption peaks of carbonl nearby1623.8cm-1, it proved peanut shellmicrocrystalline cellulose occurred etherification.(6) This paper combined modified peanut shell microcrystalline cellulose andchitosan to make preparation of edible films, and chose glycerin as plasticizer. Theresults showed modified peanut shell microcrystalline cellulose can significantlyincrease the TS of edible films and WVP. Glycerin can reduce the TS of edible filmsand WVP, but increase the E of edible films. With the use of response surfaceexperiment design, the preparation of chitosan/modified peanut shell microcrystallinecellulose edible films can be optimized. This paper adopted three influencing factors,concentration of modified peanut shell microcrystalline cellulose, concentration ofchitosan, concentration of glycerin. The TS, E and WVP are experimental indexes toget the optimized parameters on preparation of edible films, while draw a conclusionthat concentration of modified peanut shell microcrystalline cellulose was0.40%,concentration of chitosan was1.57%, and concentration of glycerin was1.03%.According to the calculation of software, the maximum of TS was13.03MPa, themaximum of E was80.93%and the minimum of WVP was2.67×10-11g/m·s·Pa.Innovation of this paper:(1) This paper did the preparation of peanut shell cellulose and microcrystallinecellulose by chemical method, optimized the preparation conditions, and comparedthe basic physical and chemical properties of peanut shell cellulose andmicrocrystalline cellulose.(2) This paper did chemical modification of peanut shell microcrystallinecellulose by etherification reaction, explorerd the effects of different modification conditions on DS of modified peanut shell microcrystalline cellulose, obtainedmodified peanut shell microcrystalline cellulose with high degree of substitution andhigh activity. |
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