Senka Popović

Edible films and coatings: Sources, properties and application

In order to extend product shelf life while preserving the quality scientific attention focused to biopolymers research that are base for edible films and coatings production. Another major advantage of this kind of food packaging is their eco-friendly status because biopolymers do not cause environmental problems as packaging materials derived from non-renewable energy sources do. Objective of this work was to review recently studied edible films and coatings - their sources, properties and possible application. As sources for edible biopolymers were highlighted polysaccharides, proteins and lipids. The most characteristic subgroups from each large group of compounds were selected and described regarding possible physical and mechanical protection; migration, permeation, and barrier functions. The most important biopolymers characteristic is possibility to act as active substance carriers and to provide controlled release. In order to achieve active packaging functions emulsifiers, antioxidants and antimicrobial agents can also be incorporated into film-forming solutions in order to protect food products from oxidation and microbial spoilage, resulting in quality improvement and enhanced safety. The specific application where edible films and coatings have potential to replace some traditional polymer packaging are explained. It can be concluded that edible films and coatings must be chosen for food packaging purpose according to specific applications, the types of food products, and the major mechanisms of quality deterioration.

In vitro study on digestion of pumpkin oil cake protein hydrolysate: Evaluation of impact on bioactive properties

In this work, a simulated gastrointestinal digestion of pumpkin oil cake protein hydrolysate prepared by alcalase (AH) was studied to evaluate the impact of the main gastrointestinal proteases on its antiradical and angiotensin I-converting enzyme (ACE) inhibitory activity. The in vitro digestion was performed in a model system under optimized reaction conditions, first by pepsin and then with α-chymotrypsin and trypsin, simultaneously. The treatment with the gastrointestinal proteases led to a significant increase of the degree of hydrolysis, up to 55.95 ± 3.1% in the final digest. After the digestion, the 2,2-azinobis3-ethylbenzo-thiazoline-6-sulphonic acid radical cation activity of AH was increased from 7.59 ± 0.1 to 10.25 ± 0.3 mM trolox equivalent antioxidant coefficient/mg (p < 0.05), while the ACE inhibitory activity was not affected, being 74.29 ± 1.25% (IC50 = 0.404 ± 0.014 mg/ml) (p>0.05) in the final digest. These results showed an advantage of AH to increase the antiradical and resist ACE inhibitory activity during digestion by main gastrointestinal proteases, appearing as promising bioactive food ingredient.

Characterization of Starch Edible Films with Different Essential Oils Addition

Abstract This study investigated properties of starch-based edible films with oregano and black cumin essential oil addition. Essential oils addition positively affected film swelling (decreased due to essential oil addition), mechanical properties (tensile strength decreased while elongation at break increased), and water vapor barrier properties (decreased along with essential oils addition). Control film did not have any biological activity, which proves the need for essential oils addition in order to obtain active packaging. Oregano oil was more effective in terms of biological activity. Endothermal peak, above 200°C, represents total thermal degradation of edible films. Diffraction pattern of control film showed significant destruction of A-type crystal structure. Addition of essential oils resulted in peak shape change: diffraction peaks became narrower. Principal Component Analysis has been used to assess the effect of essential oils addition on final starch-based edible films characteristics with the aim to reveal directions for the film characteristics improvement, since the next phase will be optimal film application for food packaging.

Biopolymer Packaging Materials for Food Shelf-Life Prolongation

Abstract In order to increase sustainability in the food industry, while maintaining product quality, the use of biopolymer packaging materials presents an attractive, ecofriendly alternative to synthetic polymers due to availability, low cost, and renewable raw materials and agroindustrial waste (biomass) usage. Materials used for biopolymer preparation are polysaccharides, proteins, or lipids, based on the compositional units. In order to improve biopolymer material properties, they can be laminated or formed as composites. In addition, biopolymer materials can be edible and/or active with strong antioxidant and/or antimicrobial properties. Numerous studies have been conducted with the aim of widening successful implementation of biopolymer packaging for a range of food products. It is very important to be familiar with properties of biopolymer packaging materials prior to application, as well as to produce biobased materials in terms of specificity of the product intended to be packed. The aim of this chapter is to review the possibility of biopolymer packaging material application for packing dairy, meat, fruits, and vegetable products.

Mono- and bilayer biopolymer films: Synthesis and characterisation

The purpose of this paper is to improve the properties of biopolymer protein monofilms and produce a novel bilayer biopolymer film on the basis of the monofilms analyzed. Biopolymer monolayer films, based on pumpkin oil cake (PuOC) and zein, and a bilayer film, based on PuOC and zein (PuOC/Zein), were produced as a result of the study. The visual, mechanical, physicochemical and structural properties of the films were evaluated. The results obtained showed that the PuOC film exhibited the highest elongation at break, followed by the bilayer film, whereas the zein film showed the lowest elongation at break. However, the zein film showed the highest tensile strength, followed by the PuOC film. The tensile strength of the bilayer PuOC/Zein film was almost 3 times lower than that of the PuOC film, and almost 4 times lower than that of the zein film. The physicochemical properties recorded indicate that the hydrophobic zein film is the least sensitive to moisture, affecting the moisture sensitivity of PuOC film by reducing the moisture content, swelling and total soluble mater of the bilayer PuOC/Zein film. Based on the FTIR spectra, it could be concluded that there are no significant differences between the two sides of the bilayer PuOC/Zein film. Both sides of the bilayer film examined indicated characteristic peaks for protein biopolymer films in the FTIR spectrum.

Biopolymer films synthesis and characterisation

In this study, three biopolymer films were synthesized: zein (protein), gelatin (protein), and starch (polysaccharide) films and characterized by determining mechanical and physico-chemical properties. Gelatin films proved to be the strongest (tensile strength 84 N/15 mm), while the zein were most flexible (elongation at break 41.6 %). Moisture content was higher in starch films, which is a result of the hydrophilic nature of the polysaccharide films. Swelling degree was 22.5 % for zein, 90.9 % for gelatin, while the highest average value was recorded in starch film samples (840.6 %). Starch films had highest value of solubility degree (36.5 %), while zein film had 27.9 % and gelatin film had 11.85 %.Obtained characterization results are consequences of the different structure of the raw materials and synthesis routes. All undesirable characteristics could be improved by optimizing the composition of the film, as well as synthesis of composite/laminated films.

Antimicrobial activity of composite chitosan biofilms with beeswax and caraway essential oil

In this paper, influence of increasing concentrations of beeswax on the antimicrobial activity of chitosan-caraway essential oil biofilm was investigated. Selected microorganisms for the test were Salmonella Typhimurium and Listeria monocytogenes. Reduction of S. Typhimurium and L. monocythogenes viable counts in bacterial suspension in the presence of chitosan films with or without added beeswax amounted over 80 % after 24 h contact time, and over 95 % after 3 h of contact time, respectively and influence of added beeswax on growth reduction was not detected. However, when number of S.Typhimurium viable cells was analyzed (log CFU/ml), it was shown that addition of beeswax led to increased activity of films, especially for the films with 36 kg/m and 54 kg/mof beeswax. When films were transferred, after 24 h in bacterial suspension, onto Petri dishes with nutrient agar and incubated for 24 h on 37 °C, results also showed beeswax contribution to growth inhibition of S.Typhimurium.

Improvement of Water Vapor Barrier Properties of Chitosan-Collagen Laminated Casings using Beeswax

Collagen casings are commercially used in sausage production. In this paper, collagen film that is used for sausage casings was laminated with chitosan film to produce barrier casing film. Chitosan coating was prepared by dissolving chitosan powder in 1% acetic acid. After dissolving chitosan, caraway essential oil, wetting agent Tween 20 and different amounts of beeswax, from 0 to 25 g were added to the solution. The solution was coated on collagen film surface in three layers, using a sponge brush to make laminated films. Films were air dried at temperature t =23 °C ± 2 °C. Uncoated collagen film was used as reference. Film thickness, water vapor barrier properties and FTIR spectra were determined. With growing amount of beeswax added to the chitosan layer, film thickness grew from 112 μm for laminated film with 5 g of beeswax to 225 μm for film with 25 g of beeswax, compared to 83 μm for collagen film. Water vapor barrier properties improved with growing amount of beeswax in chitosan layer, ranging from 130.71 g/m24h for laminated film with added 5 g of beeswax to 66.96 g/m24h for the film with 25 g of beeswax, compared to 290.64 g/m24h for collagen film. Addition of beeswax showed great potential in lowering water vapor permeability of laminated collagen-chitosan film. FTIR spectra could be used to determine quantitative law dependency between added amount of beeswax and spectra absorption values,as well as to prove compactness of chitosan-beeswax layer.

Optimization of Enzymatic Hydrolysis of Cucurbitin Using Response Surface Methodology: Improvement of the Functional Properties

Optimization of enzymatic hydrolysis of cucurbitin, extracted from pumpkin (Cucurbita pepo) oil cake with bromelain, was carried out by response surface methodology (RSM). Second-order polynomial model (R2=0.791) has been proposed for the effect of time (t), and enzyme/substrate ratio (E/S) on degree of hydrolysis (DH). Conditions for obtaining maximal value of DH were determined (E/S= 0.0132 (w/w), t= 42 min). Furthermore, according to the regression equation, conditions for production of hydrolysates with target DH values were chosen. Comparison of the functional properties of cucurbitin and its hydrolysates (DH= 10%, 20% and 30%) were carried out. The solubility of the hydrolysates gradually increased with the increase of DH, in pH range of 6–8. The hydrolysate with DH=10% had the best emulsifying properties (EA=0.632 ± 0.02 A500nm, ES= 44.2min), and extent of hydrolysis decreased both emulsifying activity and emulsifying stability. All studied hydrolysates exhibited higher oil-holding capacity and have improved foaming properties compared to the original protein. DH has influence on foam capacity. The highest foam capacity has hydrolysate with DH=20% (150.3±3.66 %). Obtained results suggest that limited protease hydrolysis of cucurbitin with bromelain produces the hydrolysates with improved functional properties and indicate their possible use in different food systems.