Egon Schnitzler

Thermal characterization of partially hydrolyzed cassava (Manihot esculenta) starch granules

Cassava starch, partially hydrolyzed by fungal a-amylase, was characterized using thermal analysis, light microscopy and X-ray diffraction. Thermal degradation was initiated at lower degradation temperatures after enzymatic treatment and the DSC (Differential scanning calorimetry) analysis showed almost similar range of gelatinization temperature, but the enthalpies of gelatinization were quite increased for the partially hydrolyzed starch granules. The results suggested that the partial degradation of the starch granules was concentrated in the amorphous regions.

Structural, physico-chemical, thermal and pasting properties of potato (Solanum tuberosum L.) flour

In this work, two varieties of potato flour (Ágata and IAPAR Cristina) were studied by simultaneous thermogravimetry–differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), rapid viscoamylographic analysis (RVA), and microscopy (NC-AFM) that were compared with conventional physico-chemical analysis, according different granulometry of each flour. Flours of IAPAR Cristina showed higher levels of starch, fiber, and phosphate and it showed higher thermal stability (TG–DTA), as well as higher pasting temperature and viscosity (RVA), and lower enthalpy of gelatinization (DSC) in the two granulometries. Flours of Agata showed higher gelatinization enthalpy (DSC) and lower pasting temperature (RVA). Atomic force microscopy—non contact method (NC-AFM), was important to check for protrusions and pores of the flour surfaces. The differences between cultivars can be attributed mainly to the genotypes and growth conditions of the tubers, which can modify the flour properties.

Thermoanalytical and starch content evaluation of cassava bagasse as agro-industrial residue

As fracoes nutricionais bem como as propriedades termicas e outras analises sao essenciais para a industria de alimentos e suas aplicacoes O bagaco de mandioca e um importante residuo agroindustrial e seu teor de amido foi avaliado por dois metodos alternativos. A caracterizacao por analise termica e microscopia ajudou na compreensao de como a hidrolise digere a fracao amilacea do bagaco de mandioca, O ponto de fusao foi de 170oC, a analise termogravimetrica (TG) mostrou apos a perda de umidade do material, duas principais perdas de massa em todas as amostras analisadas. Os resultados sugerem que a hidrolise enzimatica e menos eficiente na conversao total de amido no bagaco de mandioca. No entanto, o uso de acido sulfurico degradou ate mesmo a parcela fibrosa do material, afetando as condicoes de analise.

Equilibrium, Thermoanalytical and Spectroscopic Studies to Characterize Phytic Acid Complexes with Mn(II) and Co(II)

Potentiometric studies were carried out to determine the binding degree of phytic acid with Co(II) and Mn(II) ions, in the absence of dioxygen. Equilibrium constants for all major complexes formed are reported, and the results are presented in the form of distribution diagrams showing the concentrations of individual complexes as a function of pH. The formation constants of the complexes show higher values for the species in which the ligand was more deprotonated. Potentiometric data indicates that the species [MH4L]6-, was totally formed at pH 7.0 and the complexes were synthesized from this data. A solid state complex of Mn(II) and Co(II) with phytic acid was synthesized. Thermogravimetry, differential scanning calorimetry, and infrared spectroscopy were used to investigate and characterize the thermal behavior of these compounds. The results led to information on the composition, dehydration, thermal stability and thermal decomposition of the isolated complexes.

Brazilian Dioscoreaceas starches

Abstract Determination of the characteristics of native starches is crucial in order to select their best application in various industrial fields. Thus, two different types of non-traditional native starches from the Dioscoreaceas species (Dioscorea sp. and Dioscorea piperifolia Humb. var. Wild) were studied regarding their thermal, structural and rheological properties. The results were contrasted with traditional commercial starch sources (potato, cassava and corn). From the thermogravimetric results (TG/DTG), D. piperifolia starch obtained the highest thermal stability of the samples, except for potato starch. Furthermore, using differential scanning calorimetry and viscoamylograph profiles (RVA), it was found that the Dioscoreaceas starches presented a higher onset (To) temperature and susceptibility to retrogradation. They also showed lower values in relation to relative crystallinity, which was calculated from their X-ray patterns and tendency to white (L*) colour. The shapes of the Discoreaceas starch granules were determined using electron microscopy; it was found that as the potato starch the Dioscoreaceas starches showed a wide range of particle size.

Porous waxy maize starch

Starch is the most important storage reserve carbohydrate in plants, and it has wide uses in the industry. It is also the main energy-providing source in human nutrition. Waxy starch, in turn, is virtually composed by amylopectin, with very low levels of amylose. This corn starch variety was partially hydrolyzed in order to verify the granules behavior and to study thermal phase transitions by thermal analysis, such as differential scanning calorimetry and simultaneous thermogravimetry–differential thermal analysis. Morphological and structural studies were performed, such as scanning electron microscopy and X-ray diffractometry. It was verified that treated samples showed low variation of enthalpy levels and also a slight increase in gelatinization temperature, possibly due to higher granule resistance to degradation. X-ray diffractometry analysis is within that expected, showing pattern A-type. Treated samples showed low viscosity peak and tendency to retrogradation when compared to its native counterpart.

Caracterização físico-química de bagaço de mandioca in natura e após tratamento hidrolítico

A mandioca, uma materia prima cultivada e processada em paises tropicais para obtencao de amido, tem grande importância agroindustrial no Brasil. A tecnologia de processamento, entretanto, nao se desenvolveu completamente, necessitando de melhorias, pois ha geracao de residuos que ainda nao se constituem em co-produtos, sendo comumente descartados de forma inadequada. Um exemplo desses residuos e o farelo, bagaco ou massa de mandioca. Trata-se de um material fibroso e ainda rico em amido que pode ser hidrolisado com a conversao do amido e de parte da celulose em acucares fermentesciveis para a producao de etanol ou de outros bioprodutos. E o principal residuo solido e sai do processo com umidade superior a 80 %, dificultando a logistica de transporte e armazenamento, pois alem do volume, o material e muito perecivel. Nao ha, atualmente, um processo empregado em grande escala pelas empresas processadoras de amido de mandioca no Brasil que seja aceito como viavel do ponto de vista economico. A secagem, uma das principais limitacoes para a comercializacao e utilizacao do bagaco, foi abordada neste trabalho, incluindo a obtencao de isotermas de sorcao e algumas formas de secagem foram testadas. O bagaco foi caracterizado fisico-quimicamente e submetido a hidrolise enzimatica com o objetivo de avaliar a potencialidade para que se torne um co-produto do processamento industrial das raizes. Os resultados revelaram elevada concentracao de carboidratos (amido) no material e tambem o comportamento frente a secagem mecânica.

Thermal analysis as screening technique to assess spray-drying process of encapsulated “yacon” juice

Abstract“Yacon” is a plant from Andean region (South America) whence it has spread to other countries. It produces roots with high content of fructooligosaccharides, inulin, some phenolic compounds among others substances. With sweet taste and low-energetic value, these roots are considered prebiotic food due to some medicinal properties. The encapsulation process via spray drying was used in this work from a pilot plant with aim to obtain a juice from this root (YJ). Solid whey (W) and maltodextrin (MD) was added in different ratios. Optimisation conditions were determined, and the best encapsulation process was YJ with MD:W ratio 80:20, which results are in agreement with those obtained by thermogravimetry/derivative thermogravimetry, differential scanning calorimetry and confirmed by field emission gun scanning electron microscopy. Thus, thermoanalytical techniques are important tools that can be used in quality control of industrial encapsulation process.

Effect of acid–alcoholic treatment on the thermal, structural and pasting characteristics of European chestnut (Castanea sativa, Mill) starch

Starch modification studies have been carried out to overcome the shortcomings of native starches and to increase the usefulness of starch for industrial applications. The thermal, structural and pasting properties of starch from chestnut fruits (Castanea sativa, Mill), which were modified by mixtures of water–HCl, methanol–HCl and ethanol–HCl at different concentrations, were assessed. The thermogravimetry (TG) results showed that the chestnut starches had lower thermal stability when compared to starch from other botanic sources; however, after treatment, this stability increased. The differential scanning calorimetry results confirmed the gradual degradation of the amorphous areas of the starch granules by the acid–water mixture, which was enhanced by acid–ethanol treatment, leading to more crystalline residues that needed higher enthalpy to gelatinise. Using X-ray powder diffractometry, it was possible to observe a C-type starch and a reduction in relative crystallinity values when compared to native starch. In addition, the pasting viscosities decreased in all the modified starches, as was expected. However, obvious defects or signs of damage on the surface of the granules were not observed after treatment. This study is helpful to better understand the relationships between structure and functional properties in relation to the eventual industrial application of chestnut starches.

Characterisation of Cassava Bagasse and Composites Prepared by Blending with Low-Density Polyethylene

ABSTRACT The main objective of this study was to characterise the cassava bagasse and to evaluate its addition in composites. Two cassava bagasse samples were characterised using physicochemical, thermal and microscopic techniques, and by obtaining their spectra in the mid-infrared region and analysing them by using x-ray diffraction. Utilising sorption isotherms, it was possible to establish the acceptable conditions of temperature and relative humidity for the storage of the cassava bagasse. The incorporation of cassava bagasse in a low-density polyethylene (LDP) matrix was positive, increasing the elasticity modulus values from 131.90 for LDP to 186.2 for 70% LDP with 30% SP bagasse. These results were encouraging because cassava bagasse could serve as a structural reinforcement, as well as having environmental advantages for its application in packaging, construction and automotive parts. Key words: Manihot esculenta Crantz , residue, polymers * Author for correspondence: demiate@uepg.br