Functional characterisation and antimicrobial efficiency assessment of smart nanohydrogels containing natamycin incorporated into polysaccharide-based films

The potential application of polysaccharide-based films containing smart nanohydrogels for the controlled release of food preservatives is demonstrated here. Smart active packaging is the most promising alternative to traditional packaging as it provides a controlled antimicrobial effect, which allows reducing the amount of preservatives in the food bulk, releasing them only on demand. This work evaluates the usefulness of smart thermosensitive poly(N-isopropylacrylamide) (PNIPA) nanohydrogels with or without acrylic acid (AA) incorporated into polysaccharide-based films (GA) to transport natamycin and release it as a response to environmental triggers. Release kinetics in liquid medium from GA films containing PNIPA/AA nanohydrogels (GA-PNIPA(5) and GA-PNIPA-20AA(5)) presented a characteristic feature regarding the films without nanohydrogels that was the appearance of a lag time in natamycin release, able to reach values of around 35 h. Another important feature of natamycin release kinetics was the fact that the release from GA-PNIPA/AA films only occurred when temperature was increased, so that the natamycin release was restricted to when there is a risk of growth of microorganisms that cause food spoilage or the development of pathogenic microorganisms. Additionally, it could be observed that the relative fraction of natamycin released from GA-PNIPA/AA films was significantly (p<0.05) higher than that released from GA films loaded with the same amount of free natamycin. It can be hypothesised that the encapsulation of natamycin into nanohydrogels helped it to be released from GA films, creating reservoirs of natamycin into the films and, therefore, facilitating its diffusion through the film matrix when the nanohydrogel collapses. In a solid medium, the low water availability limited natamycin release from GA-PNIPA/AA films restricting the on/off release mechanism of PNIPA/AA nanohydrogels and favouring the hydrophobic interactions between natamycin and polymer chains at high temperatures. Despite the low natamycin release in solid media, antimicrobial efficiency of GA-PNIPA(5) films containing natamycin in acidified agar plates was higher than that obtained with GA films without natamycin and GA films with free natamycin, probably due to the protecting effect against degradation when natamycin was included in the nanohydrogels, allowing its release only when the temperature increased.Clara Fucinos and Miguel A. Cerqueira are recipients of a fellowship (SFRH/BPD/87910/2012 and SFRH/BPD/72753/2010, respectively) from the Fundacao para a Ciencia e Tecnologia (FCT, POPH-QREN, and FSE Portugal). The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the project "BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes", Ref. NORTE-07-0124-FEDER-000028 co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER and the project from the "Ministerio de Educacion y Ciencia" (Spain) "Nanohidrogeles inteligentes sensibles a cambios de pH y Temperatura: Diseno, sintesis y aplicacion en terapia del cancer y el envasado activo de alimentos", Ref. MAT2010-21509-C03-01

Natamycin release from alginate/pectin films for food packaging applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Single and composite films based on alginate and pectin containing natamycin as active agent were prepared and the release behavior in water and the diffusion coefficients were evaluated. The influence of natamycin on physical attributes of the films was also investigated. Addition of natamycin promoted an increase in soluble matter in water, in the water vapor permeability and in the opacity and a decreased in tensile strength when compared to films without the added anti-microbial agent. The natamycin mass released by immersion of the film in water fitted well to Fick's second law diffusional model, with effective diffusivity values ranging from 3.2 x 10(-9) (single pectin films) to 9.2 x 10(-12) cm(2)/s (single alginate films). The values of the diffusional exponents ranged between 0.5 and 1.0, suggesting that the transport process had non-Fickian (anomalous) characteristics. The single alginate films exhibit more suitable attributes for application in packaging than the single pectin and the composite films. (C) 2011 Elsevier Ltd. All rights reserved.11011825Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2005/55499-3, 2008/52830-9

Modelling natamycin release from alginate/chitosan active films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In antimicrobial active films, the active agent is incorporated in the polymeric matrix and is released from the film to the product surface where most deterioration processes take place. In this study, films structured solely by alginate and by blends of alginate:chitosan (82.5:17.5 and 65:35) were obtained by casting. The film formulations received natamycin (4 and 8 g/100 g biopolymer) as antimicrobial agent. Films were characterised according to their thickness and morphology. Diffusion experiments in water indicated very slow release kinetics of the antimicrobial, being markedly hindered in the alginate and chitosan composite films, probably due to electrostatic interactions between chitosan and natamycin. Fickian diffusion prevailed and the diffusion coefficients found for the films varied from 2.6 x 10-11 to 2.5 x 10-12 cm2 s-1.474740746Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [Proc. n. 2005/55499-3

Influence of Drying Conditions on Physical Properties of Alginate Films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The effect of drying conditions of the film-forming solution on thickness, moisture content, water vapor permeability, and tensile properties of alginate films were investigated. A long period of constant rate was observed in all conditions and the model proposed by Wang and Singh was able to adjust the drying data. As expected, there was a clear effect of temperature on drying kinetics; that is, increasing the drying temperature decreased the drying time. Considerable glycerol losses were observed when alginate gel was oven dried at temperatures above 40 degrees C. Compared to other drying conditions, films oven dried at 60 degrees C were thinner, had lower moisture content, and were less flexible.3017279Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [Proc. 2008/52830-9

Effect of calcium and/or barium crosslinking on the physical and antimicrobial properties of natamycin-loaded alginate films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The preparation of alginate films with suitable properties requires a two-step contact with reticulating agents: initially a weakly structured pre-film is formatted which is further crosslinked in a second stage by immersion in a more concentrated solution. The present work evaluated the effects of a combined crosslinking procedure using calcium and barium ions on the physical and morphological properties of alginate-based films containing natamycin as antimicrobial agent. The release behavior of natamycin in water was evaluated as well as the antimicrobial activity against four target microorganisms, which are common cheese product contaminants. Films attributes were affected by the type of ion used in the second stage while the natamycin release rate and the antimicrobial activity were influenced by the ion used in the first stage. Films crosslinked with Ba2+ in the first and Ca2+ in the second stage (Ba-Ca films) exhibited physical properties very similar to films crosslinked with calcium in both stages. Release kinetics of natamycin in water fitted well to Fick's second law diffusional model, with effective diffusivity values ranging from 0.40 x 10(-11) to 1.74 x 10(-11) cm(-2)/s. Ba-Ca films presented the lowest natamycin diffusion coefficient and the smallest inhibition zone diameter against the four microorganisms tested. (C) 2014 Elsevier Ltd. All rights reserved.572494501Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Programa Ciencia (Portugal)COMPETE (Portugal) [PEst-C/EQB/UI0102/2011]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)COMPETE (Portugal) [PEst-C/EQB/UI0102/2011

Influence of natamycin loading methods on the physical characteristics of alginate active films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Natamycin, an antimicrobial agent sparingly soluble in water, was incorporated into alginate films in order to produce antimicrobial packaging, using three different approaches: the conventional loading method, when natamycin is added directly to the polymeric aqueous film-forming solution; the immersion procedure, by which a previously prepared films is contacted with natamycin solution, and by the supercritical solvent impregnation (SSI) method, with loading tests performed in CO2 containing natamycin, with and without addition of cosolvent (ethanol, 10% molar). The loading capacities were evaluated, as well as the influence on physical attributes of the films and on the release behavior of natamycin in water. The conventional method led to films heterogeneities with high surface roughness, and the immersion technique evinced several disadvantages like low incorporation yields, and negative influence on water vapor permeability and on the swelling degree of the film. The supercritical method showed that longer contact times and the use of ethanol as a cosolvent increased the natamycin loading yields and led to homogeneous films, where SSI (CO2 + EtOH) process produced visually attractive and tranlucent films. (C) 2013 Elsevier B.V. All rights reserved.767482Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq