•Size, cell shape and cellular architecture of mesocarp tissue control apple firmness•Stiffness and complexity of cell wall were the main biomechanics of apple tissues•Cellulose fibers and pectic ...agglomerate size explain some differences in apple firmness•Principal component analysis was successful in classifying the studied apple cultivars.•A simplified model for firmness prediction of some apples was obtained by multivariate analysis
A study of the physicochemical, structural, nanomechanical properties at macro, micro and nanometric scales was carried out to determine which features have the greatest influence on the firmness of selected apple cultivars (Golden Delicious, Granny Smith, Gala and Red Delicious). Physicochemical assays, microscopy techniques, image analysis, nanoindentation and spectroscopy were used to characterize the properties of the four selected apples. The data were analyzed using principal component analysis, Pearson analysis and multiple linear regression to classify apple cultivars. These techniques were also used to identify which physicochemical, micro, and nanostructural as well as nanomechanical features were most associated with apple firmness. This allowed for the creation of a mathematical model (R2 = 0.97) for the prediction of apple firmness from evaluated variables. It was determined that the cellular architecture, stiffness of cell walls and crystallinity index of cellulose fibers were the most important factors in explaining the variability of firmness in the studied apples. This research provides novel and valuable information for understanding the role of cellular architecture, micro and nanostructure, as well as nanomechanical properties in the firmness of the studied cultivars.
•Microstructure of nopal spines was characterized by microscopy techniques.•Distribution of cellulose and lignin in nopal spines was evidenced by microscopy.•Micromechanical properties are influenced ...by the structural arrangement of spines.•Nopal spines are harder than wood materials.•Nopal spines could be an alternative source of cellulose and lignin.
The aim of this work was to study the microstructure and micromechanical properties of spines obtained from nopal waste. Spines were obtained by drying at 40 °C then sieving. Physical and chemical assays and microscopy techniques were used to determine the role of microstructural arrangement in local micromechanical properties. Transversal (TS) and longitudinal sections (LS) of the spines were studied by indentation and microscopy. Environmental scanning electron microscopy was helpful for characterizing the overall structure of spines. Confocal laser scanning microscopy was used for determining the distribution of cellulose and lignin in spines, which was associated with their micromechanical properties. Atomic force microscopy showed that TS is less rough (Ra = 3.08 ± 0.75 nm) and more hard (0.57 ± 0.31 GPa) than LS (Ra = 24.56 ± 1.60 nm, 0.57 ± 0.31 GPa). In accordance with these results, the elastic modulus of LS (8.65 ± 3.18 GPa) is lower than that of TS (14.94 ± 7.09 GPa). The hardness and elastic modulus of libriform fibers and sclerified epidermis are influenced by their microstructures and as well as the distribution of cellulose and lignin in the spines. The microstructural arrangement and the distribution of cellulose and lignin in the TS provide greater hardness values than those of woods. The current study presents a novel structural characterization of nopal spines and their local micromechanical properties. This waste product could be a cheap and non-wood alternative resource of cellulose with good mechanical properties useful for designing novel biomaterials with applications in the agricultural sector.
Apart from its dietary use, Opuntia ficus-indica (OFI), also known as nopal, is widely used in diverse non-food areas given its multiple properties and health benefits. In Mexico City, each year ...de-thorning process of nopal generates around 40,000 tons of waste. This waste contains a huge amount of hemicellulose and cellulose that can be used as a new biodegradable nanocomposite. Therefore, the aim of this work was to purify nopal thorns to obtain cellulose nanoparticles by high impact milling or high-energy ball milling. Confocal laser scanning microscopy (CLSM) showed that thorns have two main polysaccharides arranged in parallel fibers: cellulose and lignin. Size of the obtained cellulose nanoparticles were ranged from 24 to 122 nm. Crystallinity, as well as the type of cellulose obtained, were analyzed by means of XRD to evaluate its potential use as nanocomposite.
In Mexico, agave constitutes a natural waste that comes from many different industries. This situation creates an opportunity area for the research, exploitation, and use of these agro-industrial ...wastes. Present work compared color, mechanical, and functional properties of PVA/cellulose/Alginate, PVA/cellulose/chitosan, and PVA films. Milox process and high-energy ball milling were used to purify agave waste for the later obtaining of cellulose nanoparticles (CNP). Addition of CNP to the films reinforced and increased the tensile strength of them.
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