With the aim of achieving 'tailor-made' chitosan fi lms, the effects of several variables on the properties of chitosan fi lms were studied. These variables were chitosan concentration and molecular weight of thermally depolymerized chitosan, addition of lipids (palmitic acid, beeswax or carnauba wax) and plasticizer (glycerol). The water vapour transmission rate (WVTR) and mechanical properties of these fi lms were measured. The innovative feature of this study is that it provides specifi c information to support the design of tailor-made fi lms. These can only be formulated when the effects of the important variables are well understood. It was found that WVTR was reduced by 57% in fi lm made from chitosan that had been thermally treated for 7 h at 100°C (molecular mass 13.7 kDa), while in the emulsion fi lms, the WVTR was increased by incorporation of palmitic acid, beeswax or carnauba wax incorporation. The mechanical properties (tensile strength and elongation at break) were improved when glycerol was used as plasticizer, resulting in more elastic fi lms (increasing the elongation at break by 62%).
Four phytopathogenic fungi were cultivated up to six days in media containing chitooligosaccharide mixtures differing in average DP and F A . The three different mixtures were named Q3 (which contained oligosaccharides of DP2-DP10, with DP2-DP7 as main components), Q2 (which contained oligosaccharides of DP2-DP12, with DP2-DP10 as main components) and Q1 (which derived from Q2 and contained oligomers of DP5-DP8 with hexamer and a heptamer as the main components). The novel aspect of this work is the description of the effect of mixtures of oligosaccharides with different and known composition on fungal growth rates. The growth rate of Alternaria alternata and Rhizopus stolonifer was initially inhibited by Q3 and Q2 at higher concentrations. Q1 had a growth stimulating effect on these two fungi. Growth of Botrytis cinerea was inhibited by Q3 and Q2, while Q1 had no effect on the growth of this fungus. Growth of Penicillium expansum was only slightly inhibited by higher concentrations of sample Q3, while Q2 and Q1 had no effect. The inhibition of growth rates or their resistance toward chitooligosaccharides correlated with the absence or presence of chitinolytic enzymes in the culture media, respectively.
In this work, changes in the hyphal morphology due to chitosan treatment in some fungal species were studied. Scanning electron microscope (SEM) observations revealed that chitosans with molar fraction of acetyl groups (F A 0.16 and 0.18) and degree of polymerization (DP 1,089 and 1,242) had a direct effect on the morphology of the chitosan-treated fungi, reflecting its potential for causing a delay in the growth ofAlternaria alternata (500 µg × mL -1 ), Botrytis cinerea (1,000 µg × mL -1 ), Penicillium expansum (1,000 µg × mL -1 ) and Rhizopus stolonifer (500 µg × mL -1 ). Mycelial aggregation and structural changes such as excessive branching, swelling of the cell wall and hyphae size reduction were observed in the micrographs.
ResumoEste trabalho tem como objetivo a caracterização de três amostras comerciais de quitosana de baixo grau de acetilação, bem como a preparação e caracterização de filmes comestíveis a partir dessas amostras, com vistas a posterior aplicação desses filmes em recobrimento de frutos. As amostras foram caracterizadas pela massa molar, grau de acetilação, análise elementar, espectroscopia de infravermelho e análise térmica, enquanto os filmes pela análise térmica, espectroscopia de infravermelho, sólidos totais e permeabilidade ao vapor de água. As amostras comerciais mostraram diferentes massas molares que variaram de 132 a 245 kDa, graus de acetilação de 5,8 a 6,3% e apresentaram análise elementar próxima a fórmula C 6 H 11 O 4 N para a unidade de repetição. Os filmes produzidos apresentaram espessuras de 3,7 a 6,8 μm, sólidos totais de 2,0 a 6,3 g m -2 e permeabilidade ao vapor de água de 170,1 a 180,2 g dia -1 m -2 . Os filmes de quitosana com maior teor de sólidos e menor massa molar foram menos permeáveis ao vapor de água. Nas análises de infravermelho e termogravimetria foram observados, respectivamente, os mesmos grupos funcionais e curvas semelhantes de decomposição, para as amostras e para os filmes produzidos. Palavras-chave: caracterização, filmes comestíveis, quitosana. AbstractThe objective of this study is to characterize three commercial samples of chitosan with low degree of acetylation, as well as the preparation and characterization of edible films from these samples, aiming the subsequent application of these films in fruit coatings. The samples were characterized by molar mass, degree of acetylation, elemental analysis, infrared spectroscopy and thermal analysis, while the film was characterized by thermal analysis, infrared spectroscopy, total solids and water vapor permeability. The commercial samples showed different molar masses, which ranged from 132 to 245 kDa, degrees of acetylation from 5.8 to 6.3% and presented an elemental analysis next to the formula C 6 H 11 O 4 N, for the repeating unit. The films produced had thicknesses from 3.7 to 6.8 μm, total solids from 2.0 to 6.3 g m -2 and water vapor permeability from 170.1 to 180.2 g day -1 m -2. The chitosan films with a higher content of solids and a lower molar mass were less permeable to water vapor. Infrared and thermogravimetric analyses showed the same functional groups and similar decomposition curves, respectively, for the samples and for the films produced.Keywords: characterization, edible films, chitosan. IntroduçãoOs polímeros quitina e quitosana têm sido bastante estudados devido ao elevado potencial de aplicações em indústrias alimentícias, farmacêuticas, cosméticas e na agricultura [1][2][3] . Esses polímeros são constituídos de cadeias lineares dos carboidratos 2-acetamido-2-deoxi-D-glicopiranose e 2-amino-2-deoxi-D-glicopiranose unidos por ligações glicosídicas β (1-4) e, podem ser distinguidos por suas solubilidades em solução aquosa de ácido acético 1%. Quitina, contendo um número ≥ 40% de N-acetil-D-glicosamina é in...
The inhibitory effects of fifteen chitosans with different degrees of polymerization (DP) and different degrees of acetylation (FA) on the growth rates (GR) of four phytopathogenic fungi (Alternaria alternata, Botrytis cinerea, Penicillium expansum, and Rhizopus stolonifer) were examined using a 96-well microtiter plate and a microplate reader. The minimum inhibitory concentrations (MICs) of the chitosans ranged from 100 μg ×mL-1 to 1,000 μg ×mL-1 depending on the fungus tested and the DP and FA of the chitosan. The antifungal activity of the chitosans increased with decreasing FA. Chitosans with low FA and high DP showed the highest inhibitory activity against all four fungi. P. expansum and B. cinerea were relatively less susceptible while A. alternata and R. stolonifer were relatively more sensitive to the chitosan polymers. Scanning electron microscopy of fungi grown on culture media amended with chitosan revealed morphological changes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.