Valorization of Rice Straw into Cellulose Microfibers for the Reinforcement of Thermoplastic Corn Starch Films

Abstract

In the present study, agro-food waste derived rice straw (RS) was valorized into cellulose microfibers (CMFs) using a green process of combined ultrasound and heating treatments and were thereafter used to improve the physical properties of thermoplastic starch films (TPS). Mechanical defibrillation of the fibers gave rise to CMFs with cumulative frequencies of length and diameters below 200 and 5–15 µm, respectively. The resultant CMFs were successfully incorporated at, 1, 3, and 5 wt% into TPS by melt mixing and also starch was subjected to dry heating (DH) modification to yield TPS modified by dry heating (TPSDH). The resultant materials were finally shaped into films by thermo-compression and characterized. It was observed that both DH modification and fiber incorporation at 3 and 5 wt% loadings interfered with the starch gelatinization, leading to non-gelatinized starch granules in the biopolymer matrix. Thermo-compressed films prepared with both types of starches and reinforced with 3 wt% CMFs were more rigid (percentage increases of ~215% for TPS and ~207% for the TPSDH), more resistant to break (~100% for TPS and ~60% for TPSDH), but also less extensible (~53% for TPS and ~78% for TPSDH). The incorporation of CMFs into the TPS matrix at the highest contents also promoted a decrease in water vapor (~15%) and oxygen permeabilities (~30%). Finally, all the TPS composite films showed low changes in terms of optical properties and equilibrium moisture, being less soluble in water than the TPSDH films.

Lamination of starch/polyesters by thermocompression for food packaging purposes

“…The obtained tensile parameters of the lm monolayers are in the range of those previously reported for the same polymers. 3,4,11,37,39 In the case of PHBV, a decrease in the TS and EM values was observed due to the plasticising effect of the PEG1000, although no increase in the lm stretchability was observed, as reported by other authors. 37,39 As expected, the starch lms exhibited the highest values of water vapour permeability (WVP) and water vapour transmission rate (WVTR); however, a marked reduction in this property was promoted by the DH modication process, as also reported by other authors analysing corn and cassava starch lms.…”

“…37,39 As expected, the starch lms exhibited the highest values of water vapour permeability (WVP) and water vapour transmission rate (WVTR); however, a marked reduction in this property was promoted by the DH modication process, as also reported by other authors analysing corn and cassava starch lms. 11,12 The DH treatment affects the molecular interaction, favouring the tendency towards molecular re-association 22 due to the hydrogen bonds between the formed carbonyl and hydroxyl groups, 40 which modify the water interactions with the polymer. Lower values of WVP and WVTR were observed for all polyester materials, where the incorporation of PEG reduced the water vapour barrier capacity of the PHBV lms; this was expected as the increase in the matrix polarity and molecular mobility promotes both the solubility and diffusion of water molecules in the matrix and, so, the permeation rate.…”

Active poly (lactic acid) films with rice straw aqueous extracts for meat preservation purposes

“…The cups were placed into desiccators at 25°C and 53% RH (Mg(NO 3 ) 2 over-saturated solution) containing a fan placed on top of each cup to decrease the resistance to water vapour transport. The cups were weighed every 1.5 hours with an analytical balance (± 0.0001 g) throughout 48 h. Finally, the WVP was calculated from the slope of the weight loss-time curves (Freitas et al, 2021). For each formulation, the analysis was carried out in triplicate.…”

“…Given its renewability, availability, cheapness, and richness in lignocellulosic fractions (~ 70% dry matter), several environmentally-friendly approaches have been proposed to valorise and exploit its potential (Goodman, 2020). Obtaining bioactive extracts from RS, using green and sustainable extraction processes, is of great interest given the notable antioxidant and antimicrobial properties (Menzel, 2020;Freitas et al, 2021) of some of its components, such as ferulic, gallic, protocatechuic or p-coumaric acids (Karimi et al, 2014;Menzel et al, 2020). The process extraction e ciency and the pro le of active extract compounds depend on factors, such as temperature and time, kind of solvent, pressure or sample pre-treatments (Alara et al, 2021;Herrero et al, 2012).…”

Synergistic Reinforcement of Cellulose Microfibers from Pineapple Leaf and Ionic Cross-Linking on the Properties of Hydrogels

“…To further improve the mechanical properties, the DN hydrogel was incorporated with many kinds of reinforcement, especially inorganic materials, for example, multiwalled carbon nanotubes (MWCNTs), nanoclays (NC), nanosilica (NS), glass fibers, and cellulose. ,,, Among these, cellulose fiber (CF), a green material derived from plants, has drawn a lot of attention due to its low density, high surface area, good biocompatibility, and remarkable mechanical properties. ,, The comparative studies of three different nanocelluloses, that is, cellulose nanocrystals (CNC), bacterial cellulose (BC) nanofibers, and 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO) radical-oxidized cellulose nanofibers (TOCN), as reinforcing fillers for DN hydrogels were reported . It was found that BC with a high aspect ratio can strengthen the DN hydrogel almost 7 times higher than that of the neat one.…”