Browsing by Author "Bueno, C."
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- Activity of chitosan films against different microorganismsPublication . Sanches-Silva, A.; Maia, C.; Furtado, R.; Ribeiro, T.; Paseiro, P.; Sendón, R.; Rodríguez-Bernaldo de Quirós, A.; López-Cervantes, J.; Sánchez-Machado, D.I.; Bueno, C.; Soto Valdez, H.; Angulo, I.; Aurrekoetxea, G.P.; Bilbao, A.; Costa, H.S.Chitosan is a hydrophilic polysaccharide which derives from chitin by deacetylation. It has several applications, namely as a film that can be applied to preserve the quality and increase the shelf-life of food. Chitosan is insoluble in most solvents but it is soluble in dilute organic acids such as formic acid and acetic acid[1]. The properties of chitosan depend on the degree of deacetylation (DA) and molecular weight (MW). A broad antimicrobial activity has been attributed to chitosan, either for gram-negative, gram-positive bacteria and fungi. The aim of the present study is to evaluate the antimicrobial activity of a chitosan film prepared by casting. The chitosan was obtained from shrimp waste collected from shrimp processing factories of South Sonora (Mexico). Four bacteria (Bacillus cereus; Escherichia coli; Staphylococcus aureus and Listeria monocytogenes) and one fungus (Botrytis cinerea) were evaluated. Although L. monocytogenes and B. cinerea growth was not inhibited by the chitosan film, results showed a clear growth-inhibitory effect, at the two bacteria concentration levels tested, for B. Cereus, E. coli and S. aureus. Different antibacterial mechanisms have been proposed to explain chitosan antimicrobial activity[2-3]: i) chitosan may form an external barrier which inhibits essential nutrients adsorption; ii) chitosan can also penetrate the microbial cell, disturbing the metabolism of the cell by inhibiting the mRNA and protein synthesis; iii) chitosan may have an ionic surface interaction with the bacteria originating wall cell leakage. Although these mechanisms may take place simultaneously, the antimicrobial activity may also depend on the properties of chitosan (DA and MW).
- Characterization of chitosan meant for antimicrobial food packagingPublication . Sendón, R.; Rodríguez Bernaldo de Quirós, A.; Bueno, C.; Pereira, D.; Sanches-Silva, A.; Costa, H.S.; Sánchez-Machado, D.I.; Soto Valdez, H.; Angulo, I.; Aurrekoetxea, G.P.; López-Cervantes, J.; Paseiro, P.Chitosan (CAS nº 9012-76-4) is a natural polysaccharide obtained by the partial deacetylation of chitin. It is a linear polymer of β (1-4) 2-acetamido-2-deoxy-D-glucose and 2-amino-2-deoxy-D-glucose in different proportions. Chitin is the most abundant polysaccharide after cellulose and the main source is the shells of crustaceans. It has been demonstrated that some important properties are directly related to the antimicrobial activity of chitosan. Some of these properties are the molecular weight (Mw), the degree of polymerisation (DP) and the degree of deacetylation (DD). In this work several analytical techniques (FTIR (Fourier-transform Infrared Spectroscopy), NMR (Nuclear Magnetic Resonance Spectroscopy) and SEM (Scanning Electron Microscopy)) were attempted to characterize two different samples obtained from shrimp waste. It can be concluded that sample 1 should be more suitable to be added as an active agent to a film.
- Preparation, characterization and evaluation by FTIR and NMR of antimicrobial activity of chitosan active filmsPublication . Lago, M.A.; Sendón, R.; Rodríguez-Bernaldo de Quirós, A.; Bueno, C.; Sanches-Silva, A.; Costa, H.S.; Sánchez-Machado, D.I.; Soto Valdez, H.; Angulo, I.; Aurrekoetxea, G.P.; López-Cervantes, J.; Paseiro, P.One of the main causes of food spoilage is the development of microorganisms. In order to inhibit or retard the growth of microorganisms and consequently, improve food security and extend the shelf life of food products, in the past years, active packaging and particularly films with antimicrobial properties have attracted the attention of the scientists. One of the approaches used is to add chitosan to the film. Due to their excellent properties, non-toxic, biodegradable, biofunctional and biocompatible with others antimicrobials, chitosan is one of the antimicrobial agents most appropriate for the development of active materials [1]. Chitosan (CAS nº 9012-76-4) is a polysaccharide, with the structure of a linear polymer of (1-4)-linked 2-amino-deoxy-β-D-glucan, obtained by the partial deacetylation of chitin, one of the most abundant polysaccharides in nature, found in shells of crustaceans [2]. Shrimp waste (heads and cephalothorax) samples were collected from local shrimp processing factories in South Sonora, Mexico. The waste was minced, fermented and centrifuged. After the treatment, three fractions were obtained: chitin rich fraction, protein rich liquor and lipid fraction. In this work, Fourier Transformed Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) were used to characterize three different samples of chitosan. Moreover, 100% chitosan-based films and films of polyamide with chitosan incorporated were also evaluated. The degree of acetylation (DA) values obtained may change, depending on the nature and level of impurities, source and polymer morphologies [3]. To evaluate the DA, FTIR and NMR were used. The samples were prepared as a thin pellet made from a mixture of KBr and the chitosan powder. To evaluate the DA in films, Fourier Transform Total Reflection infrared Spectroscopy (FTIR-ATR) was used. All spectra were recorded in the range of 400-4000 cm-1. Nuclear Magnetic Resonance (NMR) was also employed to evaluate the DA. Two experiments were tentatively carried out: 1H NMR and 13C NMR. In both cases approximately 5 mg of each sample were diluted in 1 % (v/v) CD3COOD in D2O. All data were compared with three commercially available standards submitted to the same experiments as samples. The sample 1 corresponding to chitosan obtained from shrimp waste and with high viscosity presented the lowest DA, therefore had higher antimicrobial activity. Both techniques; FTIR and NMR, led to the same conclusion.