Elsevier

LWT

Volume 117, January 2020, 108613
LWT

Fish gelatin films containing aqueous extracts from phenolic-rich fruit pomace

https://doi.org/10.1016/j.lwt.2019.108613Get rights and content

Highlights

  • Gelatin films with selected berry fruit extracts were developed.

  • The film with blue-berried honeysuckle extract had the highest antioxidant activity.

  • All films with increased volume of extract revealed antimicrobial activity.

  • None of the used extracts affected the water barrier properties of the films.

  • Extracts enhanced the mechanical strength of films plasticized with glycerol at 20%.

Abstract

The aim of the work was to study the feasibility of using aqueous extracts from rowanberry, blue-berried honeysuckle, and chokeberry pomace for the formulation of fish gelatin films with antioxidant and antimicrobial activity as well as improved mechanical and water barrier properties. The predominant phenolic components in rowanberry and chokeberry extracts were hydroxycinnamates, and in blue-berried honeysuckle extract anthocyanins. Although the gelatin film itself showed antioxidative activity, addition of blue-berried honeysuckle extract increased it 3-fold. Unlike the films containing 1.2 mL of extract, the films with increased extract volume possessed strong antimicrobial properties against E. coli, P. fluorescens, S. aureus, L. innocua. Films plasticized with glycerol at 15 and 17.5% did not increase the mechanical strength in the presence of all extracts tested, but at 20%, a positive effect of each extract on mechanical strength was observed. None of the extracts affected the water barrier properties of the films.

Introduction

Nowadays, there is not only a considerable interest in the use of natural polymers for environmentally friendly food packages as an alternative for non-biodegradable plastics, but also due to the possibility of obtaining active packaging materials. That latter can be achieved by incorporation into the polymer matrices natural additives displaying variety of valuable features, including antioxidant and/or antimicrobial properties.

The bioactive compounds can be extracted from many plant origins. The borage seeds and leaves (Gómez-Estaca, Giménez, Montero, & Gómez-Guillén, 2009b), oregano and rosemary (Gómez-Estaca, Bravo, Gómez-Guillén, Alemán, & Montero, 2009a; Gómez-Estaca, Montero, Fernández-Martín, Alemán, & Gómez-Guillén, 2009c), green tea (Hong, Lim, & Song, 2009; Li, Miao, Wu, Chen, & Hang, 2014), cinnamon, clove, star anise (Hoque, Benjakul, & Prodpran, 2011), ginger (Li et al., 2014), ginseng (Norajit, Kim, & Ryu, 2010), seaweed (Rattaya, Benjakul, & Prodpran, 2009) extracts rich in polyphenolic compounds, as well as various essential oils were incorporated into protein and polysaccharide films and their activity and functional properties were studied. By-products of agro-food industry can also be a source of bioactive compounds. Due to health benefits of fruit products, their consumption is steadily rising, creating a substantial amount of fruit by-products. Especially in the winemaking industry, a large mass of solid by-products is produced and some papers on the properties of polymeric films enriched with commercial extracts from grape seeds (Li et al., 2014; Sivarooban, Hettiarachchy, & Johnson, 2008) and wine grape pomace (Cerruti et al., 2011; Corrales, Han, & Tauscher, 2009; Deng & Zhao, 2011; Ferreira, Nunes, Castro, Ferreira, & Coimbra, 2014) have been published. Other fruit pomaces, for instance these from berries processing can also be used as source of bioactive compounds. According to Struck, Plaza, Turner, and Rohm (2016), the processing of berries into juice results in approximately 70–80% of target product and 20–30% of by-product. Due to the high level of polyphenolic compounds in berry pomaces (De Ancos, Colina-Coca, González-Peña, and Sánchez-Moreno (2015) they can be effectively used. However, reports on the films incorporated with them are rather scarce.

Polyphenolic compounds of various plant species include simple phenolic, phenolic acids, lignans, lignins, coumarins, flavonoids, stilbenes, flavonolignans, and tannins (Dewick, 2002). Polyphenolic composition of fruits, especially fruit berries, is different from that from other plant materials, as it is rich in bioactive polyphenols belonging to the anthocyanin group (Burdulis et al., 2009; Cisowska, Wojnicz, & Hendrich, 2011), which have been considered the most valuable components.

In the presence of plant extracts, mechanical and barrier characteristics of biopolymeric films can be changed as a result of interactions between biopolymer and polyphenolic compounds. Data on improving (Hong et al., 2009; Hoque et al., 2011; Sivarooban et al., 2008), worsening or on lack of changes (Gómez-Estaca et al., 2009b; Gómez-Estaca et al., 2009c; Gómez-Guillén, Ihl, Bifani, Silva, & Montero, 2007; Kim et al., 2006) of tensile strength of the films containing plant or herb extracts were reported. Different directions of changes of water vapour permeability (WVP) of these films were also evidenced (Gómez-Guillén et al., 2007; Hong et al., 2009; Hoque et al., 2011). Thus, in the formulation of active packaging films their functional properties must be taken in to account.

Waste from the food industry can constitute the source of polymers for food packages. Among proteins, gelatin obtained from fish offal like skins is very often used as the main component of polymer matrix (Alfaro, Balbinot, Weber, Tonial, & Machado-Lunkes, 2015; Staroszczyk, Pielichowska, Sztuka, Stangret & Kołodziejska, 2012). However, due to the hydrophilic character of gelatin, the functional properties of gelatin films are poorer than of those obtained from traditional synthetic polymers (Krochta & de Mulder-Johnston, 1997), so their application as packaging materials is still limited.

The purpose of the presented work was to study the possibility of using extracts from the pomace of some berry fruits for the formulation of gelatin films with antioxidant activity as well as improved mechanical and water barrier properties. It has been assumed that interactions of gelatin with polyphenolic compounds from fruit extracts will exert a positive effect on the functional properties of the films.

Section snippets

Materials

Fish gelatin was obtained from Norwegian farmed salmon skins as described by Kołodziejska, Skierka, Sadowska, Kołodziejski, and Nieciowska (2008). Rowanberry (Sorbus aucuparia L.), blue-berried honeysuckle (Lonicera caerulea L. var. edulis) and chokeberry (Aronia melanocarpa) came from local plantations. HPLC grade methanol, formic acid (98–100%) and Folin−Ciocalteu phenol reagent (FC) were obtained from Merck (Darmstadt, Germany). Quercetin-3-O-galactoside, cyanidin-3-O-glucoside, l-ascorbic

Characterisation of the antioxidant composition and activity of fruit pomace extracts

Plant pomace is usually composed of remaining carbohydrates, dietary fibre, and small amount of proteins. Besides, numerous studies have shown that fruit pomace is also a rich source of polyphenolic compounds, therefore making them a good source of natural antioxidants (De Ancos et al., 2015).

Three standard tests were applied to assess the antioxidant activity of aqueous extracts of pomace obtained from rowanberry, blue-berried honeysuckle, and chokeberry, namely ABTS assay, DPPH assay and FC

Conclusion

In our work we point to the potential of compounds contained in the troublesome waste products from the fish industry and fruit industry. They are usually thrown away, but can be successfully processed into valuable products. Gelatin obtained from fish offal like skins could be used as the main component of polymer matrix of food packaging materials, and fruit pomace received from the fruit processing - as a carrier of bioactive ingredients of these materials. Although in such a complex mixture

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the Polish national research budget [grant number NN 312255638].

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