Transparent, flexible, and eco-friendly starch-based films for reversible optoelectronic noses for food spoilage monitoring in smart packaging.

A reversible optoelectronic nose is presented consisting of ten acid-base indicators incorporated into a starch-based film, covering a wide pH range. The starch substrate is odorless, biocompatible, flexible, and exhibits high tensile resistance. This optical artificial olfaction system was used to detect the early stages of food decomposition by exposing it to the volatile compounds produced during the spoialge process of three food products (beef, chicken, and pork). A smartphone was used to capture the color changes caused by intermolecular interactions between each dye and the emitted volatiles over time. Digital images were processed to generate a differential color map, which uses the observed color shifts to create a unique signature for each food product. To effectively discriminate among different samples and exposure times, we employed chemometric tools, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). This approach detects food deterioration in a practical, cost-effective, and user-friendly manner, making it suitable for smart packaging. Additionally, the use of starch-based films in the food industry is preferable due to their biocompatibility and biodegradability characteristics.

Starch-based films affected by the addition of collagen from Prochilodus magdalenae residues and HPMC: Application in Andean blackberry (Rubus glaucus Benth) coatings.

Starch-based films offer the advantages of biodegradability, edibility, barrier properties, flexibility, and adaptability. This study compared the physicochemical properties of starch-based films by adding raw fish collagen and hydroxypropylmethylcellulose (HPMC). The tensile properties were evaluated, and the interaction with water was analyzed. Barrier properties, such as water vapor and oxygen permeability, were examined, and optical properties, such as gloss and good internal transmittance, were evaluated. The films were evaluated as coatings on Andean blackberries (Rubus glaucus Benth) for 2 weeks at 85% RH and 25°C. The results showed that the inclusion of collagen caused a reduction in the tensile strength and elastic modulus of the films. Also, the formulation with the highest collagen concentration (F7) exhibited the lowest weight loss and water vapor permeability, also it had the highest collagen concentration and showed the highest reduction in Xw and WAC, with values of 0.048 and 0.65 g water/g dry film, respectively. According to analyzing the optical properties, F1 presented the highest bright-ness and transmittance values, with 18GU and 82 nm values, respectively. In general, the films and coatings are alternatives to traditional packaging materials to prolong the shelf life of these fruits.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse.

In this work, cellulose nanocrystals (CNCs), bleached cellulose nanofibers (bCNFs), and unbleached cellulose nanofibers (ubCNFs) isolated by acid hydrolysis from Agave tequilana Weber var. Azul bagasse, an agro-waste from the tequila industry, were used as reinforcements in a thermoplastic starch matrix to obtain environmentally friendly materials that can substitute contaminant polymers. A robust characterization of starting materials and biocomposites was carried out. Biocomposite mechanical, thermal, and antibacterial properties were evaluated, as well as color, crystallinity, morphology, rugosity, lateral texture, electrical conductivity, chemical identity, solubility, and water vapor permeability. Pulp fibers and nanocelluloses were analyzed via SEM, TEM, and AFM. The water vapor permeability (WVP) decreased by up to 20.69% with the presence of CNCs. The solubility decreases with the presence of CNFs and CNCs. The addition of CNCs and CNFs increased the tensile strength and Young's modulus and decreased the elongation at break. Biocomposites prepared with ubCNF showed the best tensile mechanical properties due to a better adhesion with the matrix. Images of bCNF-based biocomposites demonstrated that bCNFs are good reinforcing agents as the fibers were dispersed within the starch film and embedded within the matrix. Roughness increased with CNF content and decreased with CNC content. Films with CNCs did not show bacterial growth for Staphylococcus aureus and Escherichia coli. This study offers a new theoretical basis since it demonstrates that different proportions of bleached or unbleached nanofibers and nanocrystals can improve the properties of starch films.

Lipase immobilization on biodegradable film with sericin.

An ecofriendly and low-cost film composed by cassava starch, polyvinyl alcohol, and sericin blend (CS-PVA-SS) was synthesized, characterized, and applied as a novel support for Botryosphaeria ribis EC-01 lipase immobilization by enzyme-film-enzyme adsorption. Film revealed thickness between 230 and 309 µm and higher flexibility and malleability in comparison with film without SS. Based on p-nitrophenyl palmitate hydrolysis reaction, the activity retention of immobilized lipase was 987%. For optimal conditions, the yield in ethyl oleate was 95% for immobilized enzyme. Maximum yield was obtained at 49°C, molar ratio oleic acid:ethanol of 1:3, 1.25 g lipase film or 50 U (1.03 ± 0.03 mg protein) and 30 h. Even after seven cycles of use, immobilized lipase showed 52% reduction in ester yield. Biodegradable and biorenewable film is a promising material as a support to immobilize lipases and application in biocatalysis.

Essential oils as additives in active starch-based food packaging films: A review.

The production of sustainable food packaging from renewable sources represents a prominent alternative to the use of petrochemical-based plastics. For example, starch remains one of the more closely studied replacement options due to its broad availability, low cost and significant advances in improving properties. In this context, essential oils as additives fulfil a key role in the manufacture of renewable active packaging with superior performances. In this review, a comprehensive summary of the impact of adding essential oils to the starch-based films is provided. After a brief introduction to the fundamental concepts related to starch and essential oils, details on the most recent advances in obtaining active starch-based films are presented. Subsequently, the effects of essential oils addition on the structure-property relationships (from physicochemical to antimicrobial ones) are thoroughly addressed. Finally, applications and challenges to the widespread use of essential oils are critically discussed.

Antioxidant films and coatings based on starch and phenolics from Spondias purpurea L.

The objective of this study was to prepare, for the first time, active films and coatings from fruit starch (SPFS) and phenolic stem bark extract (SBPE) from Spondias purpurea L. Starch film formulations were prepared with different SBPE contents (5-20 wt% on starch), then cast and dried into films. SBPE showed higher antioxidant activity and antimicrobial activity against both Gram-negative and Gram-positive bacteria. Chemical, morphological, thermal, optical, mechanical, and barrier properties were studied for SPFS-SBPE films. In general, the phenolic extract caused significant changes in starch films (especially when in excess), such as gradual reduction of elastic modulus and tensile strength, increased elongation, opacity, and thermal properties (e.g. glass transition and melting enthalpy). On the other hand, SBPE provided the films with active properties (antioxidant and UV-absorbing). Coatings were applied to minimally processed mangoes (MPM), which were stored for 10 days at 12 °C. SBPE-containing coatings provided better protective action, reducing the total color difference (∆E⁎) and delaying the browning index (BI) during storage as well as reducing fungus attack. The active SPFS-SBPE films showed great potential as environmentally friendly active films and coatings.

Synergic antimicrobial properties of Carvacrol essential oil and montmorillonite in biodegradable starch films.

This work evaluated the synergic effect of carvacrol essential oil (EO) and montmorillonite (MMT) (named hybrid compound), incorporated in thermoplastic starch (TPS) films in different contents (4.5, 9, and 15 wt%). TPS films were characterized by FTIR, FT-Raman, DSC, XRD, and antimicrobial assay. FTIR and FT-Raman indicated new hydrogen bonds between hybrid and starch, altering the thermal properties and requiring more energy to destroy the TPS-hybrid bonds. XRD analysis showed slight crystallinity changes, and TPS-15 hybrid showed an amorphous structure that allows the diffusion of EO thought the films. TPS-hybrid films showed antimicrobial behavior against E. coli due to the synergistic effect of MMT and EO, which resulted in strong antimicrobial effects due to the destabilization and partial destruction of the bacteria cell membrane. The hybrid probably changed the E. coli cell permeability, respiration, and electron transport. TPS-15 hybrid sample presented the lowest crystallinity, facilitating the film's oil diffusion, maximizing the bacterium inhibitory effect, and acting as a biocidal agent. The results demonstrated that a hybrid compound is a good option for starch antimicrobial films for fresh food, such as fruits and vegetables.

Corn-Starch-Based Materials Incorporated with Cinnamon Oil Emulsion: Physico-Chemical Characterization and Biological Activity.

Active packaging represents a large and diverse group of materials, with its main role being to prolong the shelf-life of food products. In this work, active biomaterials based on thermoplastic starch-containing cinnamon oil emulsions were prepared by the compression molding technique. The thermal, mechanical, and antifungal properties of obtained materials were evaluated. The results showed that the encapsulation of cinnamon oil emulsions did not influence the thermal stability of materials. Mechanical resistance to break was reduced by 27.4%, while elongation at break was increased by 44.0% by the addition of cinnamon oil emulsion. Moreover, the novel material provided a decrease in the growth rate of Botrytis cinerea by 66%, suggesting potential application in food packaging as an active biomaterial layer to hinder further contamination of fruits during the storage and transport period.

Physical, Barrier, Mechanical, and Biodegradability Properties of Modified Starch Films with Nut By-Products Extracts.

Starch-based films with phenolic extracts could replace the use of petroleum-based plastics. In this study, octenyl succinate starch (OSS) films with pecan nutshell extract (PSE) or hazelnut skin extract (HSE) were prepared. The water resistance, as well as the optical, physical, mechanical, and biodegradable properties of these films, were investigated. The PSE and HSE improved the water resistance (decreasing the solubility to 17% and increasing the contact angle to 96.80°) and UV-light barrier properties of the films. For PSE and HSE, as their concentrations increased, the film rigidity decreased since these extracts acted as plasticizers. Micrographs obtained by scanning electron microscopy (SEM) depicted a homogeneous surface as a result of extracts dispersion through the polymeric matrix and the interactions between the phenolic compounds (PC) of the extracts and the OSS. The phenolic extracts from nut by-products and octenyl succinic anhydride (OSA) starch could be used to develop films to replace the conventional plastics.

Preparation and partial characterization of films made with dual-modified (acetylation and crosslinking) potato starch.

BACKGROUND: Starch is an alternative material for the production of biodegradable plastics; however, native starches have drawbacks due to their hydrophilic nature. Chemical modifications such as acetylation and crosslinking are used to broaden the potential end-uses of starch. Dual modification of starches increases their functionality compared to that of starches with similar single modifications. In this study, a dual-modified potato starch (acetylated and crosslinked) was used to produce films by casting. RESULTS: Changes in the arrangement of the amylopectin double helices of dual-modified starch were evident from X-ray diffraction patterns, pasting profiles and thermal properties. The degree of substitution for acetyl groups was low (0.058 ± 0.006) because crosslinking dominated acetylation. Modified starch film had higher elongation percentage (82.81%) than its native counterpart (57.4%), but lower tensile strength (3.51 MPa for native and 2.17 MPa for dual-modified) and lower crystallinity in fresh and stored films. The sorption isotherms indicated that the dual modification decreased the number of reactive sites for binding water, resulting in a reduction in the monolayer value and a decrease in the solubility and water vapor permeability. CONCLUSIONS: Dual modification of starch may be a feasible option for improving the properties of biodegradable starch films. © 2018 Society of Chemical Industry.

Potassium sorbate controlled release from corn starch films.

Active starch films with glycerol and potassium sorbate were obtained by casting. Native and acetylated corn starches, as well as the mixture of them in equal proportions were used and filmogenic suspensions with pH 4.5 were also prepared. Sorbate concentration decreased during film storage due to its oxidative degradation. Active films resulted more yellow and less transparent than films without sorbate. The minimum inhibitory concentration of sorbate resulted 0.3%, regardless of the starch type and the formulation pH. The use of antimicrobial package was more effective to prevent microbial growth on food surfaces than the use of conventional methods. Additive kinetic release was neither affected by the starch type nor by the formulation pH. Sorbate diffusion process was mathematically modeled satisfactorily. Active films were able to inhibit Candida spp., Penicillium spp., S. aureus and Salmonella spp. growth. Active films extended 21% the shelf life of refrigerated cheese, regardless of the formulation pH.

Film forming capacity of chemically modified corn starches.

Native starch can be chemically modified to improve its functionality and to expand its uses. Modified starches were characterized and the rheological behavior of filmogenic suspensions was analyzed. The film forming capacity of different chemical modified corn starches was evaluated. Acetylated starch was selected by the characteristics of the resulted films; its optimum concentration was 5% w/w since their films exhibited the lowest water vapor permeability (WVP, 1.26×10(-10)g/msPa). The effect of glycerol as plasticizer on film properties depend on its concentration, being 1.5% w/w those that allows to obtain the lowest WVP value (1.64×10(-11)g/msPa), low film solubility in water and a more compact structure than those of unplasticized films. Mechanical behavior of plasticized acetylated starch films depends on glycerol concentration, being rigid and brittle the unplasticized ones, ductile those containing 1.5% w/w of glycerol and very flexible those with a higher plasticizer content.