Films Based on Biopolymers Incorporated with Active Compounds Encapsulated in Emulsions: Properties and Potential Applications-A Review.

The rising consumer demand for safer, healthier, and fresher-like food has led to the emergence of new concepts in food packaging. In addition, the growing concern about environmental issues has increased the search for materials derived from non-petroleum sources and biodegradable options. Thus, active films based on biopolymers loaded with natural active compounds have great potential to be used as food packaging. However, several lipophilic active compounds are difficult to incorporate into aqueous film-forming solutions based on polysaccharides or proteins, and the hydrophilic active compounds require protection against oxidation. One way to incorporate these active compounds into film matrices is to encapsulate them in emulsions, such as microemulsions, nanoemulsions, Pickering emulsions, or double emulsions. However, emulsion characteristics can influence the properties of active films, such as mechanical, barrier, and optical properties. This review addresses the advantages of using emulsions to encapsulate active compounds before their incorporation into biopolymeric matrices, the main characteristics of these emulsions (emulsion type, droplet size, and emulsifier nature), and their influence on active film properties. Furthermore, we review the recent applications of the emulsion-charged active films in food systems.

Rheological and Viscoelastic Properties of Chitosan Solutions Prepared with Different Chitosan or Acetic Acid Concentrations.

Chitosan (Ch) is a partially crystalline biopolymer, insoluble in pure water but soluble in acid solutions. It has attracted interest from researchers to prepare solutions using different acid types and concentrations. This research aims to study both the effect of chitosan (Ch) or acetic acid (Ac) concentrations, at different temperatures, on rheological and viscoelastic properties of Ch solutions. To study the effect of Ch, solutions were prepared with 0.5−2.5 g Ch/100 g of solution and Ac = 1%, whereas to study the effect of Ac, the solutions were prepared with 2.0 g of Ch/100 g of solution and Ac = 0.2−1.0%. Overall, all analyzed solutions behaved as pseudoplastic fluid. The Ch strongly affected rheological properties, the consistency index (K) increased and the index flow behavior (n) decreased as a function of Ch. The activation energy, defined as the energy required for the molecule of a fluid to move freely, was low for Ch = 0.5%. The effect of Ac was less evident. Both K and n varied according to a positive and negative, respectively, parabolic model as a function of Ac. Moreover, all solutions, irrespective of Ch and Ac, behaved as diluted solutions, with G" > G'. The relaxation exponent (n") was always higher than 0.5, confirming that these systems behaved as a viscoelastic liquid. This n" increased with Ch, but it was insensitive to Ac, being slightly higher at 45 °C.

Gelatin/chitosan based films loaded with nanocellulose from soybean straw and activated with "Pitanga" (Eugenia uniflora L.) leaf hydroethanolic extract in W/O/W emulsion.

Mechanical properties of biopolymer films can be a limitation for their application as packaging. Soybean straw crystalline nanocelluloses (NC) can act as reinforcement load to improve these material properties, and W/O/W double emulsion (DE) as encapsulating bioactive agents can contribute to produce active packaging. DE droplets were loaded with pitanga leaf (Eugenia uniflora L.) hydroethanolic extract. The mechanical, physicochemical, and barrier properties, and the microstructure of gelatin and/or chitosan films incorporated with NC or NC/DE were determined by classical methods. Film antioxidant activities were determined by ABTS and DPPH methods. The incorporation of NC/DE in gelatin and/or chitosan films (NC/DE films) changed the morphology of these films, which presented more heterogeneous air-side surfaces and cross-sections. They presented rougher topographies, notably greater resistance and stiffness, higher barrier properties to UV/Vis light and higher antioxidant activity than the NC films. Moisture content, solubility in water and water vapor permeability decreased due to the presence of DE. Overall, the NC/DE films improved all properties, when compared to the properties of NC films or those of films with only DE, from a previously published study. In spite of not having antimicrobial activity against the studied bacteria, NC/DE films did display a great antioxidant activity.

Echium oil with oxidative stability increased by emulsion preparation in the presence of the phenolic compound sinapic acid followed by dehydration by spray and freeze drying processes.

Echium oil is rich in omega-3, however, is unstable. The objective of this work was the co-encapsulation of echium oil and sinapic acid (SA) by emulsification using Arabic gum as emulsifier/carrier, followed by spray or freeze-drying. Eight treatments (S0, S200, S600 and S1000: particles spray dried with different concentrations of SA; L0, L200, L600 and L1000: particles freeze dried with different concentrations of SA) were analyzed in relation to microscopy, water activity (Aw), hygroscopicity, moisture, solubility, particle size, X-ray diffraction, thermogravimetry and accelerated oxidation. Particles of rounded shape and undefined form were obtained by spray and freeze-drying, besides ideal physicochemical properties for application (values from 0.091 to 0.365, 3.22 to 4.89%, 57 to 68% and 2.32 to 12.42 µm for Aw, moisture, solubility and particle size, respectively). All treatments protected the oil against oxidation, obtaining induction time of 5.31 h for oil and from 7.88 to 12.94 h for treatments. The better protection to oil was obtained with it emulsified and freeze-dried (L600); the encapsulation increased oxidative stability of the oil, besides facilitating its application over the fact the material is in powder form.

Influence of pitanga leaf extracts on lipid and protein oxidation of pork burger during shelf-life.

The effect of pitanga leaf extracts, as source of natural antioxidants, on physicochemical properties as well as lipid and protein oxidation of pork burgers during storage at 2 ±â€¯1 °C, packed under modified atmosphere, was assessed. Formerly, the in vitro antioxidant and antimicrobial activities as well as the phenolic profile of pitanga leaf extracts were also studied. Thereafter, five samples were prepared, including control (without antioxidants), commercial synthetic antioxidant (BHT at 200 mg/kg) and three concentrations of pitanga leaf extracts: PLL (at 250 mg/kg), PLM (at 500 mg/kg) and PLH (at 1000 mg/kg). The predominant phenolic compounds identified in pitanga leaf extracts were hydroxycinnamic acids, followed by tyrosol and other phenolics (alkylmethoxyphenols, hydroxycoumarins and hydroxyphenylpropenes). Pitanga leaf extracts showed a high antioxidant and antimicrobial in vitro activity. The addition of pitanga leaf extracts improved the redness of pork burgers during the whole display. On the other hand, the addition of natural antioxidants decreased the lipid oxidation from day 7 till the end of storage period. Burgers with antioxidant showed a similar protein oxidation level, observing an inhibition between 36% and 49% compared to control treatment. From the results, it can be concluded that pitanga leaf extract is a good alternative to commercial synthetic antioxidants to improve the quality and extend the shelf-life of pork burgers.

Guarana seed extracts as a useful strategy to extend the shelf life of pork patties: UHPLC-ESI/QTOF phenolic profile and impact on microbial inactivation, lipid and protein oxidation and antioxidant capacity.

The antioxidant and antimicrobial effects of guarana seed extracts (GSE) added to pork patties were evaluated for 18 days storage at 2 ±â€¯1 °C. Five treatments were prepared: i) without natural antioxidant [control (negative control)], ii) with BHT at 200 mg/kg (positive control), and iii) with three different concentrations: 250  mg/kg (guarana seed low dose-GSL), 500  mg/kg (guarana seed medium dose-GSM) and 1000  mg/kg (guarana seed high dose-GSH) of guarana extracts, respectively. The pH, instrumental colour (CIE L*, a*, b*), total viable counts (TVC), Pseudomonas spp. counts and lactic acid bacteria (LAB) counts, 2-thiobarbituric acid reactive substances (TBARS) and carbonyl content were determined after 0, 7, 11, 15 and 18 days of storage period. The in vitro antioxidant activity together with the phenolic profile of GSE was also studied. Microbial analysis showed that GSE had no antimicrobial activity on pork patties. The untargeted UHPLC-ESI-QTOF approach confirmed the wide phenolic composition of GSE able to explain the antioxidant power (28.2 g/kg of phenolic equivalents). Low doses (GSL) of GSE were able to preserve the values of colour parameters, obtaining higher L*, a* and b* values during storage, which is reflected in the lowest colour differences during storage (ΔE*0-18 = 4.56). TBARS and carbonyls values in GSE added samples were lower than control and BHT ones. GSL and GSM provided better results than the synthetic antioxidant (0.08 and 0.07 vs 0.18 mg MDA/kg; 2.47 and 3.13 vs 3.23 nmol/mg, for GSL and GSM vs BHT, respectively). These findings show that GSE are very effective against colour deterioration, lipid and protein oxidation in pork patties and possessing the potential to be used as natural antioxidants.

Microstructure and physical properties of nano-biocomposite films based on cassava starch and laponite.

The aim of this research was to study the effects of laponite concentrations on some properties of nano-biocomposite films based on cassava starch, focusing mainly the relation between the properties of the surface microstructure and roughness, water contact angle and gloss. Nano-biocomposite films were produced by casting. We analyzed gloss, color, opacity, water contact angle, crystallinity by X-ray diffraction, and microstructure by scanning electron microscopy and atomic force microscopy. Texture parameters (energy, entropy and fractal dimension) were extracted from micrographs. We observed a great impact of laponite in the morphology of nano-biocomposite films. Texture parameters correlated with surface heterogeneity and roughness. Finally, surface roughness affected the surface hydrophilicity of nano-biocomposite films. Laponite platelets were exfoliated and/or intercalated with amylose and amylopectin chains. This research reports new information on the effects of laponite concentrations on the morphological, optical and wetting properties of nano-biocomposite films aiming future industrial applications.

Properties of gelatin-based films incorporated with chitosan-coated microparticles charged with rutin.

The aim of this study was development an active film based on gelatin incorporated with antioxidant, rutin carried into microparticles. The complexation between oppositely charged lecithin and chitosan was applied to prepare the chitosan-coated microparticles. The generated microparticles had an average size of 520±4nm and a span of 0.3 were formulated by a rotor-stator homogenize at the homogenization speed 10,000rpm. Composite films were prepared by incorporating chitosan-coated microparticles, at various concentrations (0.05, 0.1, 0.5, or 1% (based on the weight of the gelatin powder)) in the gelatin-based films. For the prepared films, the results showed that obtained physicochemical, water vapor barrier, and mechanical were compared with native gelatin film with a slight decrease for chitosan concentration higher than 0.5%. The microstructure studies done by scanning electron microscopes, revealed different micropores embedded with oil resulting from the incorporation of the microparticles into the gelatin matrix. Moreover, the calorimetric results were comparable to those of gelatin control film with Tg value 45°C and increased crystallinity percentage with increasing incorporation of microparticles. This original concept of composite biodegradable films may thus be a good alternative to incorporate liposoluble active compounds to design an active packaging with good properties.

Properties of active gelatin films incorporated with rutin-loaded nanoemulsions.

Physico-chemical, mechanical, barrier, release profiles and antioxidant properties of composite gelatin based-films incorporated with rutin-loaded oil-in-water nanoemulsion, at various concentrations (5, 10, 15, or 20% (based on the weight of the gelatin powder)) were studied. All the gelatin/rutin-loaded nanoemulsion films displayed higher tensile strength and higher elongation at break than the gelatin control film. The composite films did not show significant differences in thickness, color, brightness and transparency. The structural properties evaluated by FTIR showed that the rutin-loaded nanoemulsion achieved complete miscibility within the gelatin matrix. All the gelatin/nanoemulsion films exhibited compact and homogenous microstructure. In addition, these films showed high antioxidant activities monitored by DPPH radical scavenging and reducing power activities. The Korsmeyer-Peppas model described well the rutin release profile. Rutin release was mainly governed by Fickian diffusion with simultaneous interfering swelling and disintegration phenomena. These results indicate that nanoemulsions-in-gelatin systems can function as potential active packaging systems to enhance shelf life of food products and then to provide a high-quality products (fresh/safe).

Characterization of gelatin/chitosan scaffold blended with aloe vera and snail mucus for biomedical purpose.

Biologically active scaffolds used in tissue engineering and regenerative medicine have been generating promising results in skin replacement. The present study aims to test the hypothesis that the incorporation of Aloe vera and snail mucus into scaffolds based on gelatin and chitosan could improve their structure, composition and biodegradability, with a potential effect on bioactivity. Homogeneous pore diameter as well as pore walls in the composite scaffold could be seen in the SEM image. The pores in the scaffolds were interconnected and their sizes ranged from 93 to 296µm. The addition of Aloe vera and snail mucus enlarged the mean pore size with increased porosity and caused changes in the pore architecture. The FTIR analysis has shown good affinity and interaction between the matrix and the Aloe, which may decrease water-binding sites, so this fact hindered the water absorption capacity of the material. The mechanical properties could explain the highest swelling capacity of the snail scaffold, because the high percentage of elongation could facilitate the entry of liquid in it, generating a matrix with plenty of fluid retention. The real innovation in the present work could be the use of these substances (Aloe and snail mucus) for tissue engineering.

Water desorption of cassava starch granules: A study based on thermogravimetric analysis of aqueous suspensions and humid powders.

This work reports on water desorption from cassava starch in relation with the structure and conditioning of granules in suspensions or after equilibration in desiccators. The experimental work is performed by thermogravimetric analysis with isothermal and non-isothermal protocols and interpreted to derive the activation energies and desorption frequencies according to the humidity range with no adjustable parameter. The analysis points out the different types of water interacting with the starch granules and relates the drying coefficients to their microscopic structure. The work helps clarifying contradictory and partial results from the literature.