Elsevier

Food Hydrocolloids

Volume 28, Issue 1, July 2012, Pages 189-199
Food Hydrocolloids

Physico-mechanical and antimicrobial properties of gelatin film from the skin of unicorn leatherjacket incorporated with essential oils

https://doi.org/10.1016/j.foodhyd.2011.12.003Get rights and content

Abstract

Gelatin films incorporated with bergamot (BO) and lemongrass oil (LO) at various concentrations as glycerol substitute were prepared and characterised. Incorporation of BO and LO at 5–25% (w/w protein) resulted in the decreases in both tensile strength (TS) and elongation at break (EAB) of the films. Water vapour permeability (WVP) were decreased in LO incorporated films, while it was increased in film added with BO at level higher than 5% (P < 0.05). Film solubility and transparency values decreased, and the films had the lowered light transmission in the visible range when BO and LO were incorporated. Films incorporated with LO showed inhibitory effect in a concentration dependent manner against Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella typhimurium, but BO added film inhibited only L. monocytogenes and S. aureus. Films containing both BO and LO did not inhibit Pseudomonas aeruginosa. Significant change of molecular organisation and higher intermolecular interactions among gelatin molecules were found in the film structure as determined by FTIR. Thermo-gravimetric analysis (TGA) demonstrated that films added with BO and LO exhibited enhanced heat stability with higher degradation temperature, compared with control film. Scanning electron microscopic (SEM) images revealed the presence of micro-pores in the essential oil incorporated films, which contributed to physical properties of the resulting films. Thus, gelatin films incorporated with BO and LO can be used as active packaging, but the properties could be modified, depending on essential oil added.

Graphical abstract

Highlights

► Bergamot and lemongrass oil as glycerol substitute affected the mechanical properties of gelatin film. ► Gelatin film incorporated with bergamot and lemongrass oils had antimicrobial activity. ► Properties and antimicrobial activity of gelatin film were governed by essential oils.

Introduction

Nowadays, eco-friendly materials from natural polymers have gained increasing attention for the development of packaging to reduce environmental pollution and ecological related problems caused by non-biodegradable plastic packaging (Petersen et al., 1999). Packaging is widely used for the protection of food quality, thereby ensuring hygiene and extending the shelf life of perishable items, especially those susceptible to oxidative and microbiological deterioration (Coma, 2008). Proteins, lipids and polysaccharides are employed for the preparation of bio-based packaging for food industry (Bao, Xu, & Wang, 2009). Gelatin is one of the versatile biomaterial obtained from collagen by the controlled hydrolysis of the fibrous insoluble collagen present in the bones and skin generated as waste during animal slaughtering and fish processing (Ahmad, Benjakul, Ovissipour, & Prodpran, 2011). It has been known for the excellent film forming ability (Hoque, Benjakul, & Prodpran, 2010). Gelatin-based film used for coating or packaging could maintain the quality of foods during storage, due to its barrier to oxygen, light and prevention of dehydration and lipid oxidation (Jongjareonrak, Benjakul, Visessanguan, & Tanaka, 2011). Several properties of gelatin film, such as mechanical properties, permeability, light absorption, transparency, antimicrobial activity and antioxidant ability, are influenced by the addition of active substances (Pires et al., 2009). Essential oils derived from natural sources have been added to the film as antimicrobial agent (Pereda, Ponce, Marcovich, Ruseckaite, & Martucci, 2011).

Essential oils categorised as GRAS (generally recognised as safe) by U.S. Food and Drug Administration (Persico et al., 2009) can be considered as the potential alternatives to synthetic additives (Valentao et al., 2002). Essential oils especially from bergamot and lemongrass appear as interesting natural compounds with great potential use in foodstuffs preservation. In vitro studies have revealed significant antimicrobial effects of these essential oils (Lv, Liang, Yuan, & Li, 2011; Naik, Fomda, Jaykumar, & Bhat, 2010). Thus the incorporation of bergamot essential oil and lemongrass essential oil into gelatin films offers the possibility not only of imparting antimicrobial activity, but also improving the physicochemical properties. In general, essential oils, the odorous volatile products of an aromatic plant's secondary metabolism, are well-known as antimicrobial agents that could be used to control food spoilage and food-borne pathogenic bacteria (Kalemba & Kunicka, 2003). Essential oil-based antimicrobial packaging has high potential for food applications (Emiroglu, Yemis, Coskun, & Candogan, 2010). The antimicrobial activity of essential oils is assigned to a number of small terpenoids and phenolic compounds (thymol, carvacrol, eugenol) (Oussalah, Caillet, Saucier, & Lacroix, 2007). Terpenes have the ability to disrupt and penetrate into lipid structure of the cell wall of bacteria, leading to denaturation of proteins and destruction of cell membrane, cytoplasmic leakage, cell lysis and eventually cell death (Emiroglu et al., 2010). The decrease in pH that occurs due to cell membrane disruption resulted in a loss of control of cellular processes such as DNA transcription, protein synthesis and enzyme activity (Oussalah et al., 2007). Essential oils also penetrate into mitochondrial membrane, leading to the greater permeability of organelle and the K+ ion leakage process (Oussalah et al., 2007).

Unicorn leatherjacket (Aluterus monoceros) is one of the marine tropical fish, which is harvested in large quantities throughout the world. This species has been used for fillet production in Thailand, in which a large quantity of skin has been produced as by-product (Ahmad & Benjakul, 2010). Due to its thick skin, it can be a potential source for gelatin production (Ahmad & Benjakul, 2011). As a consequence, the increased revenue for processors can be achieved. Furthermore, gelatin from unicorn leatherjacket skin can be used for smart film/packaging with antimicrobial activity. Selected natural antimicrobial agents, especially essential oils can be incorporated into films to provide their preventive role. Therefore, the objectives of this investigation were to prepare and characterise the gelatin film from unicorn leatherjacket skin and to assess the antimicrobial property of film added with bergamot and lemongrass essential oils.

Section snippets

Chemicals

Essential oils of bergamot (BO, Citrus bergamia) and lemongrass (LO, Cymbopogon citratus) were purchased from Botanicessence essential oils (Suanlung, Bangkok, Thailand). Bovine serum albumin (BSA) and high molecular weight protein markers were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Glycerol, phosphoric acid, p-dimethylaminobenzaldehyde and tris(hydroxymethyl) aminomethane were obtained from Merck (Darmstadt, Germany). Sodium dodecyl sulphate (SDS), N,N,N′,N′-tetramethyl

Thickness

Thickness of gelatin films incorporated with bergamot (BO) and lemongrass oil (LO) at various concentrations is shown in Table 1. Thickness of films incorporated with BO (5–25%) increased in comparison with the control (P < 0.05). It ranged from 0.045 to 0.048 mm. However, no significant difference in thickness was observed between films incorporated with BO in the range of 10–25% (P > 0.05). The results suggested that peptide chains of gelatin could not form the compact film network in the

Conclusion

The properties of gelatin films were affected by the addition of BO and LO. The BO and LO incorporated films with porous structure showed the decreased tensile performance (i.e., tensile strength and elongation at break). Both BO and LO affected the film differently due to the different modes of action determined by compounds presented in essentials oils. Films incorporated with LO exhibited more antibacterial activity than BO added films against microorganisms studied. The films were generally

Acknowledgements

The authors would like to express their sincere thanks to the TRF senior research scholar program and Graduate School, Prince of Songkla University for the financial support.

References (58)

  • M.J. Fabra et al.

    Tensile properties and water vapor permeability of sodium caseinate films containing oleic acid-beeswax mixtures

    Journal of Food Engineering

    (2008)
  • M.S. Hoque et al.

    Effect of heat treatment of film-forming solution on the properties of film from cuttlefish (Sepia pharaonis) skin gelatin

    Journal of Food Engineering

    (2010)
  • M.S. Hoque et al.

    Properties of film from cuttlefish (Sepia pharaonis) skin gelatin incorporated with cinnamon, clove and star anise extracts

    Food Hydrocolloids

    (2011)
  • M. Jackson et al.

    Beware of connective tissue proteins: assignment and implications of collagen absorptions in infrared spectra of human tissues

    Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease

    (1995)
  • F. Lv et al.

    In vitro antimicrobial effects and mechanism of action of selected plant essential oil combinations against four food-related microorganisms

    Food Research International

    (2011)
  • M.I. Naik et al.

    Antibacterial activity of lemongrass (Cymbopogon citratus) oil against some selected pathogenic bacteria's

    Asian Pacific Journal of Tropical Medicine

    (2010)
  • P. Nuthong et al.

    Characterization of porcine plasma protein-based films as affected by pretreatment and cross-linking agents

    International Journal of Biological and Macromolecules

    (2009)
  • B. Ouattara et al.

    Antibacterial activity of selected fatty acids and essential oils against six meat spoilage organisms

    International Journal Food Microbiology

    (1997)
  • B. Ouattara et al.

    Inhibition of surface spoilage bacteria in processed meats by application of antimicrobial films prepared with chitosan

    International Journal of Food Microbiology

    (2000)
  • M. Oussalah et al.

    Inhibitory effects of selected plant essential oils on the growth of four pathogenic bacteria: E. coli O157:H7, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes

    Food Control

    (2007)
  • M. Pereda et al.

    Chitosan-gelatin composites and bi-layer films with potential antimicrobial activity

    Food Hydrocolloids

    (2011)
  • K. Petersen et al.

    Potential of bio-based materials for food packaging

    Trends in Food Science and Technology

    (1999)
  • A.G. Ponce et al.

    Antimicrobial and antioxidant activities of edible coatings enriched with natural plant extracts: in vitro and in vivo studies

    Postharvest Biology and Technology

    (2008)
  • Y. Pranoto et al.

    Physical and antibacterial properties of alginate-based edible film incorporated with garlic oil

    Food Research International

    (2005)
  • T. Prodpran et al.

    Properties and microstructure of protein-based film from round scad (Decapterus maruadsi) muscle as affected by palm oil and chitosan incorporation

    International Journal of Biological Macromolecules

    (2007)
  • S. Rattaya et al.

    Properties of fish skin gelatin film incorporated with seaweed extract

    Journal of Food Engineering

    (2009)
  • H.W. Robinson et al.

    The Biuret reaction in the determination of serum protein: I. A study of the condition necessary for the production of the stable color which bears a quantitative relationship to the protein concentration

    Journal of Biological Chemistry

    (1940)
  • M. Rodriguez et al.

    Combined effect of plasticizers and surfactants on the physical properties of starch based edible films

    Food Research International

    (2006)
  • L. Sanchez-Gonzalez et al.

    Effect of hydroxypropylmethylcellulose and chitosan coatings with and without bergamot essential oil on quality and safety of cold-stored grapes

    Postharvest Biology and Technology

    (2011)
  • Cited by (0)

    View full text