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http://repositoriodigital.ipn.mx/handle/123456789/141
2024-03-28T22:02:08Z
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EFFECT OF OXIDATION LEVEL ON THE DUAL MODIFICATION OF BANANA STARCH: THE MECHANICAL AND BARRIER PROPERTIES OF ITS FILMS.
http://repositoriodigital.ipn.mx/handle/123456789/14309
Title: EFFECT OF OXIDATION LEVEL ON THE DUAL MODIFICATION OF BANANA STARCH: THE MECHANICAL AND BARRIER PROPERTIES OF ITS FILMS.
Authors: Bello Pérez, Luis Arturo
Abstract: Banana starch was oxidized at three different levels and then acetylated. The double-modified starch was used for film preparation. The physical, mechanical, and barrier properties were tested. The oxidation level increased the whiteness of the film, and the second modification (acetylation) did not affect this parameter. The solubility increased with temperature and oxidation level. However, acetylation decreased the solubility value. At the longest storage times, the solubility decreased because of starch reorganization inside the polymeric matrix. In general, oxidation increased the tensile strength of the films, and a slight increase was observed when the oxidized starch was acetylated. This effect was more noticeable at the longest storage time. The oxidation level decreased the percentage elongation at break, and a slight effect due to acetylation was observed. The film of oxidized–acetylated starch showed a higher elastic modulus value than its oxidized counterpart. The water vapor permeability increased with oxidation level, but the acetylation decreased this parameter. The oxidation increased the hydrophilic character of the starch because of the formation of carbonyl and carboxyl groups that showed more affinity for water molecules. When the oxidized banana starch was acetylated, a decrease in the water vapor permeability was found because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double-modified banana starch had some improved physical, mechanical, and barrier properties, and they may be used in specific applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009.
Description: http://onlinelibrary.wiley.com/doi/10.1002/app.29433/abstract
2013-03-05T00:00:00Z
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ANTIOXIDANT ACTIVITY AND CONTENT OF PHENOLIC COMPOUNDS AND FLAVONOIDS FROM JUSTICIA SPICIGERA.
http://repositoriodigital.ipn.mx/handle/123456789/14308
Title: ANTIOXIDANT ACTIVITY AND CONTENT OF PHENOLIC COMPOUNDS AND FLAVONOIDS FROM JUSTICIA SPICIGERA.
Authors: Sepúlveda Jiménez, Gabriela
Abstract: Aerial parts of Justicia spicigera are used in Mexican traditional medicine. Antioxidant activity of aqueous and methanolic extracts obtained from leaf, stem and flower of J. spicigera and their contents of phenolic compounds and flavonoids were evaluated in this study. Antiradical activity was proven for the capacity to scavenge the DPPH radical of each extract. The amount of total phenolic compounds was determined using the Folin-Ciocalteu reagent. Total flavonoid content was evaluated with aluminum chloride under basic conditions. For a same plant organ, extracts prepared with methanol possess a higher antiradical activity than those obtained with water. The antiradical activity of leaf and flower extracts was superior to that found for the stem extract prepared with the same solvent. Total phenolic content ranged from 1.33-5.01 g gallic acid equivalents/100 g dry weight. Leaf and flower extracts obtained with methanol or water had higher amounts of phenolic compounds than stem extract. Total flavonoid content is between 0.18 and 1.30 g catechin equivalents/100 g dry weight and the order for methanol extracts is leaf>flower>stem, whereas for the aqueous extracts this sequence is stem>flower>leaf. This is the first study describing the antioxidant activity from J. spicigera. Phenolic compounds and flavonoids contribute to this activity. The results suggest that J. spicigera is a source of antioxidant and support its use as an anti-inflammatory for the treatment of uterine cancer and against various free radical-related disorders.
Description: http://scialert.net/abstract/?doi=jbs.2009.629.632
2013-03-05T00:00:00Z
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VISCOELASTIC PROPERTIES OF RECONSTITUTED CASSAVA DOUGH.
http://repositoriodigital.ipn.mx/handle/123456789/14307
Title: VISCOELASTIC PROPERTIES OF RECONSTITUTED CASSAVA DOUGH.
Authors: Bello Pérez, Luis Arturo
Abstract: The influence of water (60–70%) and salt (1–2%) content on the viscoelastic properties of cassava dough, reconstituted from cooked flour, was studied using a controlled strain rheometer. Reconstituted cassava dough behaved as a solid-like material with the storage modulus (G′) predominant over the loss modulus (G″). As the water content was increased, G′ decreased and G″ increased; but tan δ was practically independent of the water content. This behaviour suggested that water had plasticising effects, but probably did not change dough structure. The effect of salt content on the dynamic rheological properties of cassava dough was not significant, except for G″ values at water contents close to 60%.
Description: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.2007.01695.x/abstract
2013-03-05T00:00:00Z
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PHYSICOCHEMICAL PROPERTIES OF BANANA STARCH OXIDIZED UNDER DIFFERENT CONDITIONS.
http://repositoriodigital.ipn.mx/handle/123456789/14305
Title: PHYSICOCHEMICAL PROPERTIES OF BANANA STARCH OXIDIZED UNDER DIFFERENT CONDITIONS.
Authors: Bello Pérez, Luis Arturo
Abstract: Starch isolated from unripe bananas was oxidized under different conditions and the physicochemical properties of the oxidized banana starches were characterized. It was found that pH was the dominating factor in the formation of carboxyl groups. Higher yields of carboxyl groups were found when oxidized starch was prepared at pH 11.5 as compared with 7.5. Longer reaction time also produced a higher carboxyl value. Maltese crosses were still visible in the polarized light micrographs of oxidized banana starch, indicating that the ordered arrangement of starch molecules was not altered. The diffraction pattern of both native and oxidized banana starches was a mixture of A- and B-types. No difference was noted in the absorbance ratio as measured by infrared spectroscopy between the oxidized banana starches at both pHs. The onset and peak gelatinization temperatures increased and gelatinization range decreased with increasing pH during the oxidation. For pasting properties, viscosity significantly decreased during heating and cooling with the most drastic reduction noted for the sample oxidized at pH 11.5. All starches showed a non-Newtonian shear-thinning behavior. The oxidation reaction that incorporated chemical groups produced a softer system in banana starch due to the possible incorporation of more water molecules in its structure.
Description: http://onlinelibrary.wiley.com/doi/10.1002/star.200800033/abstract
2013-03-05T00:00:00Z