Influence of pitanga (Eugenia uniflora L.) leaf extract and/or natamycin on properties of cassava starch/chitosan active films

Highlights

• Active films present high barrier to UV light and antioxidant properties.

• Rheological properties of the FFS were not affected by the additives.

• Structural heterogeneities due to Natamycin caused brittleness in active films.

• Cassava starch/chitosan active films with Natamycin present antifungal activity.

Abstract

Active edible coatings and films produced by addition of plant extracts and antimicrobial compounds are of interest for food packaging. The aim of this work was to develop and characterize film-forming solution and film based on blends of cassava starch/chitosan (CS/CH) incorporated with pitanga (Eugenia uniflora L.) leaf extract (PE) and/or natamycin (NA), produced by casting, and studying their effect on selected physical properties, and antioxidant and anti-fungal activities of films. The addition of PE did not affect the film mechanical properties, whereas NA significantly decreased the flexibility of films due to changes in biopolymer behavior from ductile to brittle. Structural analyses by FTIR and XRD indicated interaction among the components particularly with presence of new CO vibration peaks and shift in the characteristic CS/CH blend wave numbers. The antioxidant activity of films increased significantly with PE although the combination of additives resulted in activity reduction. Positive anti-fungal effect of NA containing films was observed against Aspergillus flavus and Aspergillus parasiticus, indicating potential for active food packaging applications.

Introduction

Edible films, based on natural biopolymers, are extensively researched as potential carriers for antioxidant and/or antimicrobial compounds with particular interest regarding active packaging (Kechichian, Ditchfield, Veiga-Santos, & Tadini, 2010; Sanches-Silva et al., 2014). Moreover, with the growing consumer concerns regarding synthetic additives, researchers are focusing on potential use of natural or nature-derived components, such as plants essential oils, like clove bud, thyme, rosemary, cinnamon, oregano, among others (Balaguer et al., 2014; Bonilla, Poloni, Lourenço, & Sobral, 2018; Otoni, Pontes, Medeiros, & de F. F. Soares, 2014). However, the use of essential oils is limited by the fact that they impart the flavor to food products which can contribute to negative organoleptic characteristics (Heras-Mozos et al., 2019). In this context, hydrophilic extracts of some plants, usually rich in phenolic compounds, can be a potential solution to the problem due to aroma or flavor migration from the active film to the packaged food (Bajić et al., 2019; Bonilla & Sobral, 2016, 2017).

Among the various plant extracts, pitanga (Eugenia Uniflora L., also known as Brazilian cherry) leaf extracts are gaining importance for food and active films applications due to their bioactive characteristics, being odorless after freeze dried (Bonilla & Sobral, 2016; Vargas, Arantes-Pereira, da Costa, de Melo, & Sobral, 2016). Their phenolic content was found to be very high, about 300 mg GAE/g, with a range of compounds like hydroxycinnamic acids (cinnamic and caffeic acids, avenanthramides, and conjugated forms of gallic acid and hydroxybenzoic acids), flavonoids (flavan-3-ols and flavones, anthocyanins and

dibenzobutyrolactone lignans), others phenolics compounds (tyrosols, alkylmethoxyphenols, hydroxycoumarins and hydroxyphenylpropenes), among others (Lorenzo et al., 2018). These diverse components were found to contribute to the antioxidant, antibacterial and antifungal effects in in vivo and in vitro tests (dos Santos et al., 2018; Lorenzo et al., 2018; Vargas et al., 2016) making pitanga leaf extract a favorable component to be tested for potential antifungal and antioxidant applications.

In consideration of antifungal activity, natamycin is a commercially known anti-mycotic and a polyene macrolide agent with applications in cheese, yoghurt and sausages for surface treatments, having generally recommended as safe (GRAS) status by FDA and natural preservative status by EU (E235). Some studies evidenced its activity in edible films to improve shelf life of cheese or strawberries (Balaguer et al., 2014; Cé, Noreña, & Brandelli, 2012; Duran et al., 2016).

Furthermore, combination of two active components in a biopolymer matrix can change films properties, being necessary to characterize the material to observe if both components presented synergistic or antagonism effects on the film’s properties (Silva-Weiss, Ihl, Sobral, Gómez-Guillén, & Bifani, 2013).

In this context, the objective of the present work was to evaluate the effect of pitanga leaf ethanolic extract and/or natamycin on selected rheological, physicochemical, antioxidant and antifungal characteristics of film-forming solutions (FFS) and films based on blends of cassava starch/chitosan for active packaging application.