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Subject: Processing and Food Engineering × Author: Bhat, Mohd Ishfaq × End date: 2024 × Start date: 2020 × Type: Thesis ×
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    ThesisItemOpen Access
    Ultrasound assisted nanocellulose extraction from microwave pre-treated rice straw to develop bio-nanocomposite for active packaging of horticultural produce
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2022-04) Bhat, Mohd Ishfaq; Shahi, Navin Chandra
    Lignocellulosic biomass (especially agricultural residue) is a sustainable feedstock for production of value-added materials through specific processing techniques and sequences as per the desired end-product. The present study aimed to utilize one such agro-residue viz. rice straw by converting it into high crystalline nanocellulose to develop a bifunctional bio-nanocomposite for active packaging of horticultural produce. The first objective involved the application of a modified microwave assisted sodium chlorite pretreatment for intensive and quick delignification of rice straw. The effect of four critical process parameters on the delignification percentage of the rice straw was studied. The delignification was manifested by characterization using Fourier transform infrared spectroscopy, x-ray diffraction and scanning electron microscopy. Using a Box-Behnken experimental design (BBD), the effect of four critical process parameters, viz. microwave power (480-800 W), microwave treatment time (4-12 min), bleaching solution concentration (0.4-3.0 %), and bleaching time (1-5 h) on the delignification (%) was investigated, and the process was optimised using response surface methodology (RSM). The experimental data best fitted a quadratic model with an R2 of 0.9964. The optimized value of process parameters in aforementioned sequence was found to be 671 W, 8.66 min, 2.67 %, and 1h respectively, for the best delignification of 93.51 percent. The absence of lignin peaks (1516 and 1739 cm-1) was corroborated by deconstructed morphological structure and higher crystallinity index in the optimised delignified sample (53.7 %). The optimized delignified rice straw powder was then subjected to ultrasound assisted acid hydrolysis for nanocellulose extraction, preceded by the removal of hemicellulose and silica. The effect of sulfuric acid concentration (40-70%), ultrasonic treatment time (30-120 min) and ultrasound power (150-250 W) on the crystallinity index (%) and the mean particle size (nm) of the nanocellulose crystals, was studied through BBD and optimized through RSM. The optimum process parameters were obtained as 51.62 % sulfuric acid concentration, 48.55 min ultrasonic treatment time and 238. 80 W ultrasound power. The mean particle size and the crystallinity index at these optimum parameters were 69.01nm and 89.72 %, respectively. The spectral characterization revealed the increased intensity of peaks corresponding to the cellulose. The transmission micrograph of the nanocellulose revealed a rod like structure with average length and width of 190 ± 6 nm and 35 ± 3 nm, respectively. The nanocellulose crystals at 1, 5 and 10% concentration levels were used for reinforcement of chitosan biopolymer along with the addition of the titanium dioxide (TiO2) nanoparticles at its 1, 3 and 5% concentration levels. The overall performance of the developed bio-nanocomposite was measured in terms of thermal, mechanical, water vapor permeability (WVP) and water sensitive properties. Thickness of the developed films varied from 0.12 to 0.17 mm. The WVP and the tensile strength were reduced and increased by 27 % and 78 %, respectively for bio-nanocomposite with 10 % cellulose nanocrystals and 3% TiO2 concentration. The thermal stability of the developed bio-nanocomposite was better as compared to neat chitosan film in terms of higher glass transition and melting temperature. The best bio-nanocomposite was used for storage study of fresh-cut apple slices. The developed bio-nanocomposite showed promising results in terms of preserving the firmness, color and the radical scavenging activity of fresh-cut apple slices for a storage study period of 11 days.