Cellulose nanostructured films from pretreated açaí mesocarp fibers: physical, barrier, and tensile performance

Abstract

Background: During de-pulping of açai (Euterpe oleracea) for juice production in the Amazonia, large amounts of fibrous waste are daily discarded, a promising substrate for production of high-value cellulose nanofibrils. Therefore, this study sought to evaluate the modifications of açai surface fibers submitted to chemical pretreatment steps and compare the quality of nanostructured films produced with different cycles of mechanical nanofibrillation. Results:A 2-hour pretreatment (at 5% of NaOH) followed by two NaOH/H 2 O 2 bleaching steps resulted in fibers with increased length and reduced diameter compared to raw fibers while preserving fiber integrity and cellulose I structure. The increase of fibers' grinding cycles from 3 (minimum to gel point) to 21 (maximum suspension thickness) resulted in nanofibril films with higher crystallinity properties, uniform thickness, compacted morphology, and smoother surface. Nanofibril films formed after different numbers of passages exhibited similar mechanical strength, but distinct barrier properties. Conclusion:Açaí waste films produced with fibers submitted to 3 grinding cycles can be recommended for packaging applications that demand easily dissolving, such as instantaneous food. Oppositely, açaí fibers subjected to 21 cycles in grinder provide films suitable for water-resistant packaging, ideal for secondary coatings of papers and paperboards.

Developing a Biodegradable Film for Packaging with Lignocellulosic Materials from the Amazonian Biodiversity

“…They are used only for decoration and handicrafts for regional producers. These lignocellulosic materials are still treated as waste in the production chain and end up being incorrectly dumped into the environment, becoming land and water pollutants when, for example, they are discharged to the banks of springs, causing a reduction in dissolved oxygen in the water and eutrophication [13].…”

Valorização dos resíduos da agroindústria de beneficiamento do açaí: Uma revisão

“…Isso não apenas enriquece o valor nutricional, mas também aprimora o sabor, conferindo ao produto final uma textura mais robusta e agradável. Braga et al (2021) Analisar as alterações na superfície das fibras de açaí após passarem por processos de pré-tratamento químico e comparar a qualidade dos filmes nanoestruturados obtidos através de diferentes ciclos de nanofibrilação mecânica.…”

Does the Addition of Cellulosic Micro/nanofibrils Improve the Properties of Hydroxypropyl Methylcellulose Films?

“…However, agglomeration of these structures may occur, as seen in figure 1. As the MFC/NFC individualization intensifies, there is a significant increase in the specific material surface (Zhang et al 2018a;Silva et al 2021). Consequently, the number of hydrogen bonds between the celulose hydroxylic groups (-OH) with the reactive groups of the polymer matrix increases significantly.…”

“…Lago et al (2020) explained that films with the same mass, but varying the proportion matrix-MFC/NFC, tend to have smaller volumes and thicknesses when the suspensions present greater amounts of MFC/NFC. It is noteworthy that thickness is a relevant variable for characterization of biopolymer composites, because it is directly related to mechanical, optical properties, and barrier to water vapor and other gases (Zhang et al 2016;Gicquel et al 2017;Braga et al 2021).…”

“…On the other hand, with higher MFC/NFC contents in the HPMC matrix, formation of interfibrillary hydrogen bonds was favored (Silva et al 2021), which offer greater slip resistance than MFC/NFC, increasing the stiffness and mechanical strength of the films (Benítez et al 2013) (see Figure 10).…”