Miniaturization of cellulose fibers and effect of addition on the mechanical and barrier properties of hydroxypropyl methylcellulose films

Antifungal edible coatings for fruits based on zein and chitosan nanowhiskers

Fresh produce have a more limited shelf life than processed ones. Their sensory attributes such as appearance and surface texture are important features in consumer perception and liking. The decomposition of fresh produce, which is caused by enzymes, chemical reactions, and microbial infections, often caused by Colletotrichum species, is inevitable. However, it can be slowed down. Several materials have been developed for this purpose, with an emphasis on active coatings using nanomaterials. In this study, the protective effects of a zein coating containing chitosan nanowhiskers (CSW) for the maintenance of fruit quality were investigated using guava (Psidium guajava L.) as a model fruit. CSW were previously characterized, and their antifungal effects against distinct Colletotrichum species (Colletotrichum asianum, Colletotrichum tropicale, Colletotrichum gloeosporioides, and Colletotrichum brevisporum) were proven. Coatings were characterized by thermogravimetric analysis, optical profilometry, and mechanical properties. Total soluble solids, pH, mass loss, and visual inspection of uncoated and coated guava fruits were also verified during 9 days. Results show that CSW length and aspect ratio decreased for longer extraction times. A similar behavior was found for x-ray diffraction in which peak intensity decreases under the same conditions. CSW degradation (ca. 250-400°C) also depends on extraction time in which more crystalline whiskers are the most thermally stable ones. The addition of CSW did not significantly (p < 0.05) modify the homogeneity and continuity of coating but prevented microbial growth assuring fruit quality during storage. In summary, coatings protected guava fruits from post-harvest spoilage while preserving quality and extending shelf life. PRACTICAL APPLICATION: Fresh foods such as fruits and vegetables have a more limited shelf life than processed ones.

Valorization of Cellulose-Based Materials from Agricultural Waste: Comparison between Sugarcane Bagasse and Rice Straw

Sugarcane bagasse and rice straw are major agricultural byproducts often discarded or burned as waste after cultivation, leaving their untapped potential for utilization. In this work, cellulose fibers were extracted from sugarcane bagasse and rice straw using a simple procedure: alkaline treatment with sodium hydroxide, bleaching with sodium hypochlorite, and acid hydrolysis. The obtained cellulosic materials were successfully prepared into milky white and transparent films, of which the transparency slightly decreased with the addition of glycerol. The surface of all the films appeared homogeneous with a random orientation of fibers. The rice-straw (RS) film had a more fragile texture than the sugarcane-bagasse (SBG) film. The FTIR analysis clearly indicated the functional groups of cellulose, as well as glycerol for the films mixed with glycerol. Thermal analysis showed that the native SBG film decomposed at 346 °C, higher than the native RS film (339 °C). The presence of glycerol in the films resulted in slightly lower maximum decomposition temperature (Td,max) values as well as mechanical properties. Regarding water susceptibility, the RS film had a higher percentage than the native SBG and glycerol-mixed SBG films. The extracted cellulose from both sources could form almost spherical-shaped cellulose particles. Thus, through the simple extraction method, sugarcane bagasse and rice straw could serve as excellent sources of cellulose materials for preparing cellulose films and particles, which would be advantageous to the development of cellulose-based materials.

Smart edible coating films based on chitosan and beeswax-pollen grains for the postharvest preservation of Le Conte pear

Smart edible coating films can be used in food packaging. For this application, they must have good physical and mechanical properties. Herein, chitosan–beeswax based film is used to preserve Le Conte pears postharvest. The chitosan–beeswax films were characterized using XRD, FT-IR, and SEM analysis. Moreover, all films showed good self-healing aptitudes ranging from 86.7 to 96.3. The film treated with pollen grains showed an enhanced water contact angle compared with the chitosan film. The chitosan–beeswax/pollen grain film exhibited a two-fold lower WVTR value compared to the chitosan film, and showed the tendency to increase the stiffness of the film. The elongation% at break was reduced from 35.81 to 14.09. Fruit quality parameters were determined in cold storage for 105 days during shelf life after a simulated marketing period of 7 days. All coated fruits successfully showed decrease in weight loss, decay and rate of softening. Therefore, chitosan–beeswax/pollen grains can be considered safe and effective coating for the fruit preservation.

Smart edible coating films can be used in food packaging.

Starch-based nanocomposites with cellulose nanofibers obtained from chemical and mechanical treatments

Cellulose nanofibers (CNFs) were isolated from unripe banana peel by acid hydrolysis, with different acid concentrations (0.1%, 1.0% and 10% v/v), followed by mechanical treatment with high-pressure homogenizer. Banana starch-based films added with CNFs (0.2% w/w) as a reinforcing agent were produced by the casting method. The rheological behavior of aqueous dispersions of CNFs (1.0% w/w) and their effects on the properties of nanocomposite films were investigated. All aqueous dispersions of CNFs showed gel-like behavior and, when incorporated to the films, CNFs improved their water barrier properties and mechanical resistance as demonstrated by the increase in tensile strength and Young's modulus. Moreover, CNFs were well dispersed in the composite matrix. CNFs prepared at higher concentration, followed by mechanical treatment (FNM1 and FNM10), formed films with low moisture (13.66%) and solubility in water (24.1%). Whereas, CNFs prepared at the lowest acid concentration without mechanical treatment (FN0.1) led to films with high elongation at break (30.6%) and good tensile strength (12.3 MPa). Regardless of the used CNFs, all the nanocomposites displayed lower UV/light transmission than control film. The nanocomposite has potential use in food packaging, since the use of CNFs can promote improvements on barrier, optical and mechanical properties. Cellulose nanofibers isolated from agro-industrial residues offer the potential to reinforce composites of biodegradable polymers, producing a value-added material.

Banana starch nanocomposite with cellulose nanofibers isolated from banana peel by enzymatic treatment: In vitro cytotoxicity assessment

The potential use of cellulose nanofibers (CNFs) as a reinforcing agent in banana starch-based nanocomposite films was investigated. CNFs were isolated from banana peel (Musa paradisiaca) by enzymatic hydrolysis. Banana starch-based nanocomposite films were prepared with CNFs using the casting method. CNFs effect on cell viability and on nanocomposite films properties' was investigated. The cytotoxicity of CNFs was assessed on Caco-2 cell line. CNFs were not cytotoxic at 50-2000 μg/mL. However, CNFs above 2000 μg/mL significantly decreased cell viability. Topography analysis showed that the incorporation of CNFs modified the film structure. The nanocomposites exhibited a complex structure due to strong interactions between CNFs and starch matrix, promoting a remarkable improvement on mechanical and water barrier properties, opacity and UV light barrier compared to the control film. CNFs can offer a great potential as reinforcing material for starch-based nanocomposite films, producing a value-added food packaging from a waste material.

Preparation and Tribological Study of Biodegradable Lubrication Films on Si Substrate

A novel method for preparing eco-biodegradable lubricant based on hydroxypropyl methylcellulose (HPMC) via hydration process is demonstrated. The smooth and homogeneous HPMC coating has a uniform thickness (~35 μm). It has been demonstrated that the preparation parameters play a critical role in controlling the lubricating behavior of the coating; in addition, excess HPMC and water concentration suppress the tribology properties. Nevertheless, a remarkable friction-reduction and anti-wear performance has been obtained. Impressively, the preparation parameter of 5% HPMC + 30 mL water significantly improves lubricant performance and durability. A simple approach for the water-degradability evaluation of HPMC is proposed.