Cristina Soltovski de Oliveira

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.

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.

Influence of the addition of hydrocolloids on the thermal, pasting and structural properties of starch from common vetch seeds (V icia sativa sp)

Belonging to the leguminous family, the common vetch seeds are a non-conventional starch source that can be exploited to attend the growing demand of the food industry. Thus, the aim of this study was to evaluate the influence of addition of hydrocolloids (5% of: carrageenan, carboxymethylcellulose (CMC), guar, jatahy, xanthan and pectin) on the thermal, pasting and structural properties of starch from common vetch (Vicia sativa) seeds. The interaction with the hydrocolloids was analysed by thermogravimetry and derivative thermogravimetry, differential scanning calorimetry (DSC), viscoamylographic analysis (RVA) and X-ray powder diffraction (DRX). From the thermogravimetry, a similar behaviour was observed for all the studied samples, with three well-defined mass losses and a thermal stability plateau. The addition of guar gum promoted an increase in its thermal stability, unlike the sample added of CMC. From the DSC analysis, it was possible to observe a decrease in onset temperatures with the addition of hydrocolloids, which can be correlated with the decrease in pasting temperatures obtained by RVA, except for the carrageenan gum, which increased these temperatures. By RVA an increase in peak viscosities was achieved, highlighting the addition of CMC, pectin and xanthan. Small variations in the degree of relative crystallinity were noted, but no changes in the diffraction pattern occurred for the samples from the XRD analysis. Although native starch has some limitations, the synergistic effect produced by the addition of gums can optimise its technological properties expanding the industrial use.

Organic amaranth starch: A study of its technological properties after heat-moisture treatment

Organic amaranth starch (Amaranthus caudatus) was studied after heat-moisture treatment (HMT) using different moisture contents and different times. The starch extracted by the aqueous method presented low lipid and protein content. After HMT, an increase in the thermal stability was identified. The onset and peak temperatures were higher with an increase in moisture content and the times used in the modification. The gelatinisation enthalpy varied due to the heterogeneity of the crystals formed after the structural reorganisation caused by HMT. The relative crystallinity was lower for the physically modified starches. An increase in the pasting temperature was accompanied by a decrease in the viscosity, setback and breakdown, which were proportional to the moisture and time used. The morphology of the HMT-modified samples was not altered; however, agglomerations were noted. Low levels of dispersion homogeneity and suspension stability were observed for the modified samples due to the strong presence of agglomerates.