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Isolation and characterization of cellulose nanocrystals from garlic skin for films reinforcement uses

Josue David Hernandez Varela, Felipe Cervantes Sodi and Macario Vicente Flores

Some industrial residue that have non-reused is garlic skin. This product become one of the promising materials to obtained cellulose microfibers (CMF) and cellulose nanocrystals (CNC) due its own composition. Garlic (Allium sativum L.) has been widely used for its culinary and medicinal attributes in various regions of the world such as Asia, the Middle East, northern Africa, southern Europe, and parts of South and Central America. In Mexico, garlic production in 2018 was established in 90,303 tons with an estimated consumption of 1.5 pounds per person. The aim of this study was comparing the utilization of garlic skin residues as source to produce cellulose nanocrystals (CNC) by ball milling. GS was pre-treated using chemical alkali extraction and bleached treatments to obtain cellulose microfibers (CMF). Cellulose nanocrystals by ball milling (CNC-BM) were obtained using a high-energy micro mill planetary and the milling time was optimized. The chemical composition of GS was determined according to TAPPI standards and showed composition of 34.26±2.66 %wt cellulose, 21.88±0.53 %wt hemicelluloses and 24.88±1.12 %wt lignin, among other components (Fig. 2). CMF and CNC were extracted and characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The FTIR spectra showed changes in the peaks at 1250, 1740, 1640 and 3400-3200 cm−1, indicating that the alkali treatment partially removed hemicelluloses and lignin from the fiber surface with a final elimination in the bleached treatment. Atomic force microscopy (AFM) and electron microscopy (SEM and TEM) techniques were used to investigate the morphology of the produced CNC. The crystallinity index of the GS was 65%, and it decreased to more than 35% after ball milling. The most promising results proved a revalue of this by-product (GS) to isolate and produce CNC. CNC-BM have a potential use as reinforcement in the preparation of biodegradable nanocomposites for storage of food products and to increase the shelf life-time.