ABSTRACT Starch is the most natural polymer used in the food and non-food industry. Sweet potato is among the world’s most important, versatile and underexploited food crops; its composition depends on the planting strategy, climatic conditions, cultivar, geographic region, soil quality, and other. The physical-chemical characteristic and functional properties depends also of the amylose, amylopectin ratio and the molecular components of amylose and amylopectin. In this study, the structural and physicochemical properties of starches from four sweet potato genotypes cultivated in Brazil were compared. Starch granules of roots of sweet potato all exhibited oval and irregular shapes with granule sizes ranging from 8 to 30 µm. Amylose contents of roots of sweet potato starches differed from 9.7 to 15.1%. Ratios of 1045/1022 and 1022/995 cm-1 of Fourier transform infrared spectra varied in the range of 0.8114–0.8558 and 0.9046–0.9347, respectively, which means that the genotypes present different structure ordering. Also, the digestibility, swelling power, and solubility showed some differences between the starches, probably due to the differences in amylose and amylopectin contents and granules sizes. The different genotypes showed similar thermal stability. Our study indicated the sweet potato genotypes are greatly influenced the amylose content, structure order, the degree of short-range order, granule size, digestibility, swelling power and solubility of sweet potato genotypes.

ABSTRACT This work aimed to evaluate three different milling conditions, seeking the optimization of CNS isolation process. The paper sludge was chemically treated with detergent and H2O2, by two steps, to remove the noncellulosic contents (hemicellulose and lignin). After these treatments, the sample was milled with the variation of a liquid medium. The three liquids milling medium were: i) dry medium (CNS-D); ii) moist with water and (CNS-W) iii) moist with ethanol (CNS-E). The CNSs were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), zeta potential and dynamic light scattering (DLS). The milled samples presented different behavior, depending on the medium applied. The CNS-W presented low efficiency due to the formation of agglomerates around the ceramic ball, resulting in larger fiber sizes (microsizes). Although, the samples CNS-D and CNS-E presented similar behavior of sizes distribution, with average size 340 nm and 373 nm, respectively, determined by DLS. The CNS-E sample presented higher yield and electrostatic stability in solution, besides not presenting loss of crystallinity, as occurred with CNS-D, observed by FTIR analysis. Thus, the isolation with ethanol showed more efficient process among the three processes studied. This work achieved the isolation of CNS; besides, it proposed an environmentally friendly isolation method, and this may add value in the paper sludge.

The paper industry primary waste is usually deposited in landfills or incinerated. This material has a high content of lignocellulosic components, which could be converted to cellulose nanostructures (CNS). This study aimed to compare compositional (Fourier transform infrared spectroscopy), thermal (thermogravimetric analysis), morphological (scanning electron microscopy) and dimensional (dynamic light scattering and atomic force microscopy) properties of CNS obtained through chemical and mechanical isolation processes. The FTIR results showed similar chemical bonding for both nanostructures, which indicated presence of cellulose and lignin. Their average size was 170 nm and 209 nm for chemical and mechanical processes, respectively. The morphology of SEM images showed a compact structure and the chemical isolation presents smaller CNS agglomeration than mechanical. TGA results showed higher thermal stability for CNS-chemical than CNS-mechanical samples and AFM images indicate the CNS morphologies, which showed nanoroads for CNS-chemical and nanoneedles for CNS-mechanical.