Abstract
ABSTRACT Background: During de-pulping of acai (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 acai 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/H2O2 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: Acai 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, acai fibers subjected to 21 cycles in grinder provide films suitable for water-resistant packaging, ideal for secondary coatings of papers and paperboards.
Highlights
The Euterpe oleracea Mart. palm, commonly known as açaizeiro, produces bunches with many açai edible fruits (Santos et al, 2019)
Sequential bleaching steps (Bc_1x2h and Bc_2x3h) decreased fiber mass by 34% and 36%, respectively, indicating lower but continuous removal of noncellulosic compounds compared to alkaline pretreatment
Effective removal of lignin depends on the additional activity of H2O2 during bleaching, which degrades its tridimensional structure into soluble fragments (Barneto et al, 2011)
Summary
The Euterpe oleracea Mart. palm, commonly known as açaizeiro, produces bunches with many açai edible fruits (Santos et al, 2019). Palm, commonly known as açaizeiro, produces bunches with many açai edible fruits (Santos et al, 2019). The pulp of this fruit is vital to the economic, social, and cultural contexts of the Amazonian region, where it is incorporated into typical gastronomy. Surface fibers comprise about 3 wt.% of the açai waste (Bufalino et al, 2018), indicating that approximately 3,590 t of cellulose-rich feedstock were available in the same year. 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. 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
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