Optical, structural, mechanical and thermal characterization of antioxidant ethylene vinyl alcohol copolymer films containing betalain-rich beetroot

Plant betalains-mixed active/intelligent films for meat freshness monitoring: A review of the fabrication parameters

The plant pigments called betalains are nutritionally safe polar compounds. They are subdivided into betaxanthins (having orange to yellow hues) and betacyanins (purple to red violet hues). Betacyanins change color with a change in pH, particularly in the range 6-8 and 9-11. Perishable foods like fish, chicken, beef, pork, and others tend to release total volatile base-nitrogen (TVB-N) during storage or deterioration, which leads to a change in the pH of pH-sensitive materials in the vicinity. pH-sensitive pigment-incorporated polymeric films with inherent active properties (or active/intelligent films) are increasingly being studied as an alternative to synthetic pH indicators to detect the accumulation of TVB-N by changing its color to indicate the stage of perishable food spoilage. There are many methods of developing such films under different conditions using different bio-based biodegradable polymer(s) and biocompatible plasticizer combinations. Among the reported methods, solution casting method has been the preferred one in most studies covered in this review. This method can be carried out under mild conditions. As such, betacyanins-incorporated polymeric films essentially require mild processing conditions because of their heat sensitivity, which will invariably affect the performance in food freshness monitoring. In this review, film fabrication parameters like temperature and duration of dissolution of polymers, plasticizer concentration, pH of the film-forming solution, film drying, and conditioning/aging, have been critically appraised based on the available literature. The lack of studies on the safety of active/intelligent films has been systematically highlighted in this review to focus future studies on this area.

Graphical abstract

Betalains as promising natural colorants in smart/active food packaging

Betalains are water-soluble nitrogen pigments with beneficial effects, including antioxidant, antimicrobial, and pH-indicator properties. The development of packaging films incorporated with betalains has received increasing attention because of pH-responsive color-changing properties in the colorimetric indicators and smart packaging films. As such, intelligent and active packaging systems based on biodegradable polymers containing betalains have been recently developed as eco-friendly packaging to enhance the quality and safety of food products. Betalains could generally improve the functional properties of packaging films, such as higher water resistance, tensile strength, elongation at break, and antioxidant and antimicrobial activities. These effects are dependent on betalain composition (about its source and extraction), content, and the kind of biopolymer, film preparation method, food samples, and storage time. This review focused on betalains-rich films as pH- and ammonia-sensitive indicators and their applications as smart packaging to monitor the freshness of protein-rich foods such as shrimp, fish, chicken, and milk.

Stable smart packaging betalain-based from red prickly pear covalently linked into cellulose/alginate blend films

Smart materials based on biomaterials have been shown growing interest by researchers. This paper investigated pH-indicator film with less leaching containing betalain molecule extracted from red prickly pear fixed in the cellulose-alginate blend as a matrix. Herein, the film was manufactured from a blend containing covalently bounded cellulose with betalain via the creation of a Fischer esterification (FE) to solve the leaching problem of dyes in contact with food. The structural, thermal, morphological optical, and mechanical properties and the pH-sensitive properties of films were examined. The FTIR and color analysis confirmed the fisher esterification. The fisher esterification led to a pH-indicator film with less leaching with significant color stability against UV light. The smart film changes colors with the pH values, where it goes from purple at a pH below 10 to yellow color at a pH above 10. All those proprieties with contact angles helped this film to be used as an intelligent film for monitoring salmon spoilage.

Research Progress in Hemicellulose-Based Nanocomposite Film as Food Packaging

As the main component of agricultural and forestry biomass, hemicellulose has the advantages of having an abundant source, biodegradability, nontoxicity and good biocompatibility. Its application in food packaging has thus become the focus of efficient utilization of biomass resources. However, due to its special molecular structure and physical and chemical characteristics, the mechanical properties and barrier properties of hemicellulose films are not sufficient, and modification for performance enhancement is still a challenge. In the field of food packaging materials preparation, modification of hemicellulose through blending with nanofibers or nanoparticles, both inorganic and organic, has attracted research attention because this approach offers the advantages of efficient improvement in the expected properties and better cost efficiency. In this paper, the composition of hemicellulose, the classification of nanofillers and the research status of hemicellulose-based nanocomposite films are reviewed. The research progress in modification of hemicellulose by using layered silicate, inorganic nanoparticles and organic nanoparticles in food packaging is described. Challenges and outlook of research in hemicellulose-based nanocomposite film in food packaging is discussed.

Developing Core/Shell Capsules Based on Hydroxypropyl Methylcellulose and Gelatin through Electrodynamic Atomization for Betalain Encapsulation

Betalains are bioactive compounds with remarkable functional and nutritional activities for health and food preservation and attractiveness. Nevertheless, they are highly sensitive to external factors, such as oxygen presence, light, and high temperatures. Therefore, the search for new structures, polymeric matrices, and efficient methods of encapsulation of these compounds is of great interest to increase their addition to food products. In this work, betalains were extracted from red beetroot. Betacyanin and betaxanthin contents were quantified. Subsequently, these compounds were successfully encapsulated into the core of coaxial electrosprayed capsules composed of hydroxypropyl methylcellulose (HPMC) and gelatin (G). The effect of incorporating the carbohydrate and the protein both in the core or shell structures was studied to elucidate the best composition for betalain protection. Morphological, optical, and structural properties were analyzed to understand the effect of the incorporation of the bioactive compounds in the morphology, color, and chemical interactions between components of resulting electrosprayed capsules. The results of the thermogravimetric and encapsulation efficiency analysis coincided that the incorporation of beetroot extract in G in the core and HPMC in the shell resulted in the structure with greater betalain protection. The effectiveness of the core/shell structure was confirmed for future food applications.

Novel Active Food Packaging Films Based on Gelatin-Sodium Alginate Containing Beetroot Peel Extract

Currently, the exploration of natural colorants from vegetal waste has gained particular attention. Furthermore, incorporation of these natural sources into biopolymers is an encouraging environmentally friendly approach to establishing active films with biological activities for food packaging. The present study developed bioactive antioxidant films based on gelatin-sodium alginate (NaAlg) incorporated with aqueous beetroot peel extract (BPE). Firstly, the effects of combining gelatin-NaAlg and BPE at 0.25, 0.5, and 1% on the mechanical, physical, antioxidant, and antibacterial properties of the films were analyzed. With increasing BPE, mechanico-physical properties and antioxidant and anti-foodborne pathogen capacities were enhanced. Likewise, when added to gelatin-NaAlg films, BPE remarkably increased the instrumental color properties. Moreover, during 14 days of storage at 4 °C, the impact of gelatin-NaAlg coating impregnated with BPE on microbial and chemical oxidation and on the sensory characteristics of beef meat samples was periodically assessed. Interestingly, by the end of the storage, BPE at 1% limited the microbial deterioration, enhanced the instrumental color, delayed chemical oxidation, and improved sensory traits. By practicing chemometrics tools (principal component analysis and heat maps), all data provided valuable information for categorizing all samples regarding microbiological and oxidative properties, sensory features, and instrumental color. Our findings revealed the ability of gelatin-NaAlg with BPE as an antioxidant to be employed as food packaging for meat preservation.

Beetroot as a novel ingredient for its versatile food applications

Beta vulgaris, also known as Beetroot, is a member of a family of Chenopodiaceae and is widely used as a natural food colorant. It gets its distinctive color due to nitrogen-containing water-soluble pigments betalains. Beetroot is an exquisite cradle of nutrients, including proteins, sucrose, carbohydrates, vitamins (B complex and vitamin C), minerals, fiber. They also contain an appreciable amount of phenolic compounds and antioxidants such as coumarins, carotenoids, sesquiterpenoids, triterpenes, flavonoids (astragalin, tiliroside, rhamnocitrin, kaempferol, rhamnetin). Recent studies evidenced that beetroot consumption had favorable physiological benefits, leading to improved cardiovascular diseases, hypertension, diabetes, cancer, hepatic steatosis, liver damage, etc. This review gives insights into developing beetroot as a potential and novel ingredient for versatile food applications and the latest research conducted worldwide. The phytochemical diversity of beetroot makes them potential sources of nutraceutical compounds from which functional foods can be obtained. The article aimed to comprehensively collate some of the vital information published on beetroot incurred in the agri-food sector and a comprehensive review detailing the potentiality of tapping bioactive compounds in the entire agriculture-based food sector.

Hot-Melt-Extruded Active Films Prepared from EVOH/Trans-Cinnamaldehyde Blends Intended for Food Packaging Applications

In this work, novel active films based on ethylene vinyl alcohol copolymer (EVOH) and cinnamaldehyde (CIN) were successfully obtained employing a hybrid technique consisting of a two-step protocol involving the preparation of a polymeric EVOH-CIN masterbatch by solvent-casting for its further utilization in the preparation of bioactive EVOH-based films by melt extrusion processing. The influence of CIN over the EVOH matrix was studied in terms of optical, morphological, thermal, and mechanical properties. Optically transparent films were obtained and the incorporation of cinnamaldehyde resulted in yellow-colored films, producing a blocking effect in the UV region. A decrease in the glass transition temperature was observed in the formulations containing cinnamaldehyde, indicating a plasticizing effect. This phenomenon was confirmed by an increase in the elongation at break values of the extruded films. Results from thermogravimetric analysis determined a slight decrease in the thermal stability of EVOH provoked by the vaporization of the bioactive compound. Bioactive properties of the films were also studied; the presence of residual cinnamaldehyde in EVOH after being subjected to an extrusion process conferred some radical scavenging activity determined by the DPPH assay whereas films were able to exert antifungal activity in vapor phase against Penicillium expansum. Therefore, the present work shows the potential of the hybrid technique employed in this study for the preparation of bioactive films by a ready industrial process technology for food packaging applications.

Development of active and smart packaging films based on starch, polyvinyl alcohol and betacyanins from different plant sources

In this study, active and smart packaging films were prepared by individually adding betacyanins-rich plant extracts (red pitaya flesh extract (RPFE), prickly pear fruit extract (PPFE), red beetroot extract (RBRE), globe amaranth flower extract (GAFE) and red amaranth leaf extract (RALE)) into starch/polyvinyl alcohol. The structural, physical and functional properties of the films containing betacyanins from different plant sources were compared for the first time. Results showed betacyanins from RPFE, PPFE and RBRE were betanin-type betacyanins. Betacyanins from GAFE and RALE were gomphrenin-type and amaranthin-type betacyanins, respectively. The films containing RPFE and PPFE presented more uniform cross-sections and had the highest water vapor barrier (9.37 and 9.26 × 10^-11 g m^-1 s^-1 Pa^-1) and mechanical strength (8.26 and 7.87 MPa). However, the film containing GAFE presented the lowest light transmittance but the highest 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (EC₅₀ = 0.47 mg/mL). All the films containing betacyanins are sensitive to pH 8-12 buffer solutions and volatile ammonia. Notably, the film containing RPFE exhibited distinct color changes (from purple-red to pink) when shrimp spoiled. Our results suggest the structural, physical and functional properties of betacyanins-rich films are closely related to the source and type of betacyanins.

Biological Properties and Applications of Betalains

Betalains are water-soluble pigments present in vacuoles of plants of the order Caryophyllales and in mushrooms of the genera Amanita, Hygrocybe and Hygrophorus. Betalamic acid is a constituent of all betalains. The type of betalamic acid substituent determines the class of betalains. The betacyanins (reddish to violet) contain a cyclo-3,4-dihydroxyphenylalanine (cyclo-DOPA) residue while the betaxanthins (yellow to orange) contain different amino acid or amine residues. The most common betacyanin is betanin (Beetroot Red), present in red beets Beta vulgaris, which is a glucoside of betanidin. The structure of this comprehensive review is as follows: Occurrence of Betalains; Structure of Betalains; Spectroscopic and Fluorescent Properties; Stability; Antioxidant Activity; Bioavailability, Health Benefits; Betalains as Food Colorants; Food Safety of Betalains; Other Applications of Betalains; and Environmental Role and Fate of Betalains.

Melt-Processed Bioactive EVOH Films Incorporated with Ferulic Acid

In this work, antimicrobial and antioxidant films based on ethylene vinyl alcohol (EVOH) copolymer containing low amounts of ferulic acid (FA) were successfully developed by melt extrusion. Optically transparent films were obtained, and the presence of FA provided some UV blocking effect. The characterization of the thermal and barrier properties of the developed films showed that the addition of FA improved the thermal stability, decreased the glass transition temperature (Tg) and increased the water vapor and oxygen transmission rates when ferulic acid was loaded above 0.5 wt.%, associated with its plasticizing effect. Mechanical characterization confirmed the plasticizing effect by an increase in the elongation at break values while no significant differences were observed in Young's modulus and tensile strength. Significant antioxidant activity of all active films exposed to two food simulants, 10% ethanol and 95% ethanol, was also confirmed using the 2,2-diphenyl-1-pricylhydrazyl (DPPH) free radical scavenging method, indicating that FA conserved its well-known antioxidant properties after melt-processing. Finally, EVOH-FA samples presented antibacterial activity in vitro against Escherichia coli and Staphylococcus aureus, thus showing the potential of ferulic acid as bioactive compound to be used in extrusion processing for active packaging applications.

Hemicellulose-Based Film: Potential Green Films for Food Packaging

Globally increasing environmental awareness and the possibility of increasing price and dwindling supply of traditional petroleum-based plastics have led to a breadth of research currently addressing environmentally friendly bioplastics as an alternative solution. In this context, hemicellulose, as the second richest polysaccharide, has attracted extensive attention due to its combination of such advantages as abundance, biodegradability, and renewability. Herein, in this review, the latest research progress in development of hemicellulose film with regard to application in the field of food packaging is presented with particular emphasis on various physical and chemical modification approaches aimed at performance improvement, primarily for enhancement of mechanical, barrier properties, and hydrophobicity that are essential to food packing materials. The development highlights of hemicellulose film substrate are outlined and research prospects in the field are described.