Evaluation of a chitosan-based edible film as carrier of natamycin to improve the storability of Saloio cheese

TLDR: In this article, the effects of chitosan coating containing natamycin on the physicochemical and microbial properties of semi-hard cheese were evaluated, and the results showed that the coating increased O2 and CO2 permeability, increasing from 7.12 to 7.68, and from 10.69 to 64.58.

About: This article is published in Journal of Food Engineering.The article was published on 2010-12-01 and is currently open access. It has received 233 citations till now. The article focuses on the topics: Natamycin & Food coating.

Figures

Fig. 4. Weight loss of cheeses during storage time. To facilitate reading, error bars are not shown. Cheeses samples coated with chitosan (s) or with chitosan containing 0.50 mg mL 1 of natamycin (d).

Fig. 3. Natamycin fractional release (NTR) from the film to the cheese calculated with Eq. (1) at 4 C. NTR is expressed in g of natamycin in PBS at time i/g of natamycin released at time zero. (s) Experimental data. The solid line represents the best fit of Eq. (2) to the experimental data.

Table 1 Values of water vapor, O2 and CO2 permeabilities and opacity of chitosan films and chitosan containing 0.5 mg mL 1 of natamycin.

Table 2 Model parameters obtained from fitting Eq. (2) to experimental natamycin release data, along with their standard deviations.

Fig. 2. Natamycin release kinetics from films of chitosan into PBS solution at 4 C. Mt/Meq is expressed in g of natamycin released from the film at time t/g of natamycin released at equilibrium. (s) Experimental data. The solid line represents the best fit of Eq. (2) to the experimental data.

Fig. 1. Inhibition of A. niger growth with chitosan-natamycin coating after incubation at 25 C during 7 days. Uncoated cheese (a) and cheese coated with chitosan containing natamycin at 0.12 mg mL 1 (b), 0.25 mg mL 1 (C) and 0.50 mg mL 1 (D).

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Evaluation of a chitosan-based edible film as carrier of natamycin to improve the storability of saloio cheese" ?

The purpose of this study was to evaluate the effects of the application of chitosan coating containing natamycin on the physicochemical and microbial properties of semi-hard cheese. This study demonstrated that chitosan-based coating/films can be used as release system containing natamycin to create an additional hurdle for moulds/yeasts in cheese thus contributing to extend its shelf-life. 

Q2. What is the benefit of mathematical modeling?

The benefit of mathematical modeling consists in the possibility of predicting parameters of the release system aiming at providing information about the mechanisms that control drug release. 

Q3. What software was used to fit Eq. (2) to the experimental data?

Statistica software (Statistica for Windows, StatSoft, Tulsa, OK, USA) was used to fit Eq. (2) to the experimental data in order to determine natamycin diffusion parameters of the model. 

Q4. What is the method of protecting cheese from moulds?

In order to protect cheese surface from mould growth, natamycin is usually applied in a polyvinyl acetate base (Reps et al., 2002). 

Q5. What is the main reason why chitosan is used as an edible film?

Having antimicrobial properties against many bacteria, filamentous fungi and yeast (Rabea et al., 2003) chitosan application as edible film and coating is very attractive. 

Q6. What is the role of edible coatings in the treatment of cheese surfaces?

Edible coatings can act as effective carriers of antimicrobials for treating cheese surfaces which are a likely location of microbial contamination. 

Q7. What wavelength was selected for natamycin absorbance measurements?

The 319 nm wavelength was selected for natamycin absorbance measurements in order to avoid interferences with absorbance spectrum of chitosan. 

Q8. What is the effect of natamycin on chitosan?

Although natamycin has been used for many years, the incorporation of natamycin on chitosan-based films could act as an additional post-processing safety measure, once the inhibitory effect on microbial growth of both components (natamycin and chitosan) is expected to provide protection against a broad spectrum of microorganisms. 

Q9. What is the main cause of the release of natamycin from the film?

The main cause of this behavior is the abrupt decrease in water activity of the release medium, therefore a small amount of water diffused into the film, resulting in negligible swelling effects (Siepmann and Siepmann, 2008). 

Q10. What is the effect of natamycin on the release of chitosan?

Before application on cheese, the authors studied natamycin diffusion from chitosan film to a liquid medium (PBS solution) aiming at determining the maximum release efficiency of the compound. 

Q11. How did Türe et al. (2008) calculate the MIC?

Türe et al. (2008) used films with a thickness ranging between 0.23– 0.69 mm to calculate the MIC by means of the agar disc diffusion assay. 

Q12. What is the effect of natamycin on the cellulose film?

Dos Santos Pires et al. (2008) found that films of cellulose show a heterogeneous structure due to the presence of natamycin larger size and bulky shape crystals, which can produce holes in the film. 

Q13. How long did the cheeses remain in the refrigerator?

All cheeses were placed on plastic trays and then incubated up to 37 days at 4 C and 85% RH to reproduce as much as possible the typical shelf life storage conditions of cheese. 

Q14. What was the reason for the decision to analyze only mesophilic bacteria in the subsequent sampling?

it was decided to analyze only mesophilic bacteria in the subsequent sampling times since these bacteria could be used as an indicator of contamination during production and ripening of cheese. 

Q15. What was the MIC of the natamycin in the cheeses?

The cheeses coated with chitosan + 0.5 mg mL 1 natamycin did not present contamination after inoculation with mould and stored at 25 C during one week, instead of uncoated cheeses which presented a noticeable contamination. 

Q16. How thick were the films cast on the agar disc?

The average thickness of control films ranged between 0.045 to 0.050 mm for the films cast on 90 mm and 57 mm diameter plates, respectively. 

Q17. What could be the reasons for the observed discrepancy?

changes in film preparation methodology, film porosity and water content in the biopolymer could also justify the observed discrepancy. 

Q18. What was the method used to determine the oxygen transmission rate through films?

an oxygen permeation analyzer (Mettler–Toledo, Switzerland) was used to measure the oxygen transmission rate through films. 

Q19. What was the effect of direct contact with PBS solution on the release of nata?

The direct contact with PBS solution was not going to provide sufficient insight into the release process of natamycin because of the very rapid diffusion kinetics of natamycin from the film under these circumstances.