Tecnologia de Alimentos
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11783
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Item Insights on physicochemical aspects of chitosan dispersion in aqueous solutions of acetic, glycolic, propionic or lactic acid(International Journal of Biological Macromolecules, 2019-05-01) Soares, Lucas de Souza; Perim, Rayza Badiani; Alvarenga, Elson Santiago de; Guimarães, Luciano de Moura; Teixeira, Alvaro Vianna Novaes de Carvalho; Coimbra, Jane Sélia dos Reis; Oliveira, Eduardo Basílio deChitosan is a polysaccharide well-known for its applicability as a biocompatible, biodegradable, and non-toxic material to produce drugs excipients and food coatings. Acidic media are required to disperse chitosan, and aqueous solutions of acetic acid have been typically used for this purpose. However, this acid has several sensory drawbacks. In this study, chitosan was dispersed [0.1 g·(100 mL)−1] in aqueous media containing acetic (AA), glycolic (GA), propionic (PA), or lactic (LA) acid, at 10, 20, 30, 40, or 50 mmol·L−1. The increase of acid concentration reduced pH and viscosity of the dispersions, and |ζ potential| of dispersed particles. Conversely, it increased electrical conductivity and density of the dispersions, and hydrodynamic diameter of dispersed particles. At a given concentration, these effects were slightly more pronounced for dispersions formed with GA or LA, compared to AA or PA. FT-IR data suggested more intense attractive interactions of chitosan chains with glycolate and lactate anions, than with acetate and propionate. Chitosan chains interacted more strongly with hydroxylated acids counter-anions than with their non-hydroxylated counterparts, leading to slight quantitative changes of physicochemical properties of these systems. Then, in physicochemical terms, GA, LA or PA are suitable to replace AA when preparing aqueous chitosan dispersions for technological applications.Item Rheological and physicochemical studies on emulsions formulated with chitosan previously dispersed in aqueous solutions of lactic acid(Food Biophysics, 2017-01-18) Soares, Lucas de Souza; Faria, Janaína Teles de; Amorim, Matheus Lopes; Araújo, João Marcos de; Minim, Luis Antonio; Coimbra, Jane Sélia dos Reis; Teixeira, Alvaro Vianna Novaes de Carvalho; Oliveira, Eduardo Basílio deChitosan, a natural, cationic polysaccharide, may be a hydrocolloid strategic to formulate acidic food products, as it can act as both bio-functional and technofunctional constituent. Typically, acetic acid is used to disperse chitosan in aqueous media, but the use of this acid is limited in food formulations due to its flavor. In this study, chitosan was firstly dispersed (0.1% m/V) in lactic acid aqueous solutions (pH 3.0, 3.5 or 4.0), and then evaluated regarding its thickener and emulsion stabilizer properties. O/W emulsions were prepared and characterized in terms of rheological properties, droplets average diameters and droplets ζ-potential. Emulsions containing chitosan were 3 times more viscous than controls without chitosan, and presented storage modulus (G’) higher than loss modulus (G”). Furthermore, they displayed two different populations of droplets (average diameters of 44 and 365 nm) and positive ζ-potential values (+50 mV). Droplets average diameters and ζ-potential did not present significant changes (p > 0.05) after storage at 25 °C during 7 days. This study showed that i) food organic acids other than acetic acetic acid can be used to disperse chitosan for technological purposes, and ii) chitosan dispersed at very low concentrations (0.1 m/V %) had relevant effects on rheological and physicochemical aspects of food-grade emulsions.Item Physicochemical aspects of chitosan dispersibility in acidic aqueous media: effects of the food acid counter-anion(Food Biophysics, 2016-12) Amorim, Matheus Lopes; Ferreira, Gabriel Max Dias; Soares, Lucas de Souza; Soares, Wanessa Aparecida dos Santos; Ramos, Afonso Mota; Coimbra, Jane Sélia dos Reis; Silva, Luís Henrique Mendes da; Oliveira, Eduardo Basílio deDifferences in formation of colloidal dispersions of chitosan in aqueous solutions of citric acid or lactic acid (25, 50 or 100 mM) were quantitatively studied. Protonation enthalpies, electrical conductivity and ζ-potential measurements were additionally undertaken, aiming at better understanding these differences at a molecular level. In dispersion kinetics assays, experimental data were well fitted (R2 > 0.9; MAPE < 4 %) by a first-order kinetics model with two terms - one accounting for the fast, direct dispersion of biopolymers chains and another accounting for the slow dispersion of chains from lumps. In all cases, maximal dispersibility was reached after about 20−30 min of stirring. For both acids, the higher the acid concentration in the medium, the higher was the chitosan dispersibility. At a given acid concentration, chitosan showed higher dispersibility in lactic acid than in citric acid solutions. Protonation of chitosan -NH2 groups was strongly exothermic, with ΔH values three times higher for citric acid (triprotic) than lactic acid (monoprotic) (ΔH = −120 kJ∙mol- 1 and ΔH = −40 kJ∙mol- 1, respectively), indicating that chitosan -NH2 protonation itself was not dependent on the type of acid. However, the electrical conductivity of suspensions of powdered chitosan in water evolved differently as these systems were titrated with citric or acid lactic. With citric acid, electrical conductivity remained virtually constant for acid concentration < of 15 mM, and then increased linearly as the acid concentration increased until 75 mM. Instead, with lactic acid, electrical conductivity progressively increased with increasing of acid concentration from 0 to 75 mM. The ζ-potential of chitosan dispersed particles was +28.5 mV and +52.1 mV in dispersions containing 10 mM of citric and lactic acids, respectively. The conjoint analysis of data from physicochemical analyses suggested that, contrarily to lactate anions, citrate anions bind more strongly on the electrical double layer of protonated, positively charged chains of chitosan, diminishing the inter-chains electrostatic repulsion, thus leading to a lower dispersibility of this polysaccharide in aqueous solutions of citric acid, compared to equimolar solutions of lactic acid.