Development and Characterization of Films with Propolis to Inhibit Mold Contamination in the Dairy Industry

Abstract

Due to the number of polyphenols with multiple biological activities, propolis has high potential to be used as an active agent in food protective films. Therefore, this study aimed to develop and characterize a sodium alginate film with ethanolic extract of propolis (EEP) for its potential use as protective active packaging against filamentous fungi in ripened cheese. Three different concentrations of EEP were analyzed: 0, 5 and 10% w/v. The films obtained were characterized, assessing thermal and physicochemical properties, as well as the concentration of polyphenols in the EEP and antifungal activity of the active films. The incorporation of EEP in the films generated thermal stability with respect to the loss of mass. Total color values (ΔE) of the films were affected by the incorporation of the different concentrations of EEP, showing a decrease in luminosity (L*) of the films, while the chromatic parameters a* and b* increased in direct proportion to the EEP concentration. Antifungal activity was observed with a fungistatic mode of action, stopping the growth of the fungus in cheeses without development of filamentous molds, thus increasing the shelf life of the ripened cheese under the analytical conditions, over 30 days at room temperature. Overall, EEP can be used to prevent growth and proliferation of spoilage microorganisms in cheese.

Keywords: active coating; active film; antifungal activity; fungi; propolis; ripened cheese; sodium alginate.

Figure 1

Minimum inhibitory concentration (a) control sample; (b) 1% w/v ethanolic extract of propolis (EEP), (c) 1.5% w/v ethanolic extract of propolis (EEP); (d) 2% w/v ethanolic extract of propolis (EEP); (e) 3% w/v ethanolic extract of propolis (EEP).

Figure 2

Thermogravimetric analysis of the control film (Alginate) and the EEP films (A/P) (a). Derivatives of thermal degradation curves of the films (b).

Figure 3

Micrographs of film surfaces; control film (a), alginate film with 5% EEP (b) and alginate film with 10% EEP (c).

Figure 4

FTIR spectra of alginate films containing ethanolic extract of propolis (EEP).

Figure 5

Antifungal activity of films. (a) Control film; (b) 5% EEP film; (c) 10% EEP film.

Figure 6

Antifungal activity on samples of ripened and fresh cheese. (a) Immersion coated ripened cheese. (b) Ripened cheese covered by brush painting. (c) Immersion coated fresh cheese. (d) Fresh cheese covered by brush painting.