Development and characterization of intelligent cellulose acetate-based films using red cabbage extract for visual detection of volatile bases

Development of xanthan gum intelligent oil-in-water ink and its application in pork freshness preservation

To optimize the stability of oil-based inks and ensure their wide application in freshness indication, new natural indicator inks were prepared using a stable oil-in-water structure. This study selected natural Lycium ruthenicum anthocyanin as the dye and glucose as the pigment carrier. Soybean oil was introduced as a linker and xanthan gum as a thickener, and an oil-in-water ink with the function of freshness indication was successfully developed. In ensuring the safety of ink labels for use on food packaging, particular attention is paid to the origin and properties of the materials used. All ingredients are of food-grade or bio-friendly provenance, thereby ensuring the safety of the product when in direct contact with food. We measured the viscosity, particle size and fineness of the ink for micro characterization and evaluated its macro printing performance by its printing effect on A4 paper. According to the experimental results, when the water-oil ratio of the ink is 10:5, the average particle size of the emulsion system is 822.83 nm, and the fineness reaches 5 μm. These values are relatively low, which indicates that the stability of the ink system is high at this time, and the ink shows excellent rheological and printing characteristics. With this water-to-oil ratio, the ink can show the best results when printed on A4 paper, clearly displaying image details. In addition, in fresh pork applications, inks with a 10: 5 water-to-oil ratio provide an accurate and highly sensitive indication of the freshness of pork. When the freshness of the pork changes, the ink color responds promptly. This high sensitivity makes the ink ideal for use as a food freshness indication tool, providing consumers with an intuitive and reliable reference for pork freshness. As a further innovation, combining this ink-printed label with a WeChat app not only allows consumers to know the freshness of the food in real-time but also tracks the supply chain information of the food, providing a more comprehensive application prospect for freshness-indicating products.

Characterization and performance evaluation of colorimetric pH-sensitive indicator based on Ҡ-carrageenan/quince seed mucilage hydrogel as freshness/spoilage monitoring of rainbow trout fillet

The aim of research was to fabricate a novel indicator by using κ-carrageenan and quince seed mucilage (QSM) hydrogels and red cabbage anthocyanin. The porosity of the hydrogel was controlled using different ratios of κ-carrageenan(C):QSM(Q) (C90:Q10, C70:Q30, and C50:Q50). The hardness of hydrogels decreased from 28.6 ± 0.3 N for C90Q10 to 11.0 ± 1.0 N for C50Q50 sample. However, according to field emission scanning electron microscopy (FE-SEM) analysis, the C50R50 sample had the best morphology with smooth surface and uniform interconnected porous network. Hydrogen bonding interactions among anthocyanins, QSM, and κ-carrageenan were confirmed by Fourier transforms infrared (FT-IR) spectroscopy. The indicator showed a color variation from red to yellow over the pH range of 2-12. Also, the indicator exhibited high sensitivity to ammonia vapors (SRGB = 115%) and good color stability. The C50QRA indicator was used for monitoring rainbow trout fillet spoilage and revealed a visually-detectable color change from red to green upon detecting total volatile basic nitrogen (TVB-N) content produced throughout storage at 4 °C. Generally, the halochromic hydrogel developed in this research can be suggested as a more sensitive and accurate freshness indicator than conventional indicator solid supports.

Development of pH-freshness smart label based on gellan gum film incorporated with red cabbage anthocyanins extract and its application in postharvest mushroom

Novel colorimetric films based on gellan gum (GG) containing red cabbage anthocyanins extract (RCAE) were prepared as pH-freshness smart labels for real-time visual detection of mushroom freshness. The GG/RCAE films had excellent pH and ammonia sensitivity. The GG/RCAE-0.2-0.3 films had the highest sensitivity to acetic acid. The SEM micrographs, AFM images, FT-IR and XRD spectra demonstrated that RCAE were successfully combined into the film-forming substrate. The incorporation of RCAE resulted in the increase of thermal stability, opacity and surface hydrophobicity of films. Meanwhile, the GG/RCAE-0.2 film exhibited stronger tensile strength and excellent color stability at 4℃. The color changes of GG/RCAE-0.2 film were visually easier to distinguish during the storage of mushroom. The results showed the GG/RCAE films could be used as pH-freshness smart labels to detect the freshness of fruits and vegetables.

Sodium-alginate-based indicator film containing a hydrophobic nanosilica layer for monitoring fish freshness

In this study, hydrophobic sodium alginate/anthocyanin/cellulose nanocrystal indicator films were fabricated by incorporating nanosilica (NS) as a waterproofing layer. The concentrations and formation methods (spraying (S), coating (C), and impregnation (I)) of the NS layer (denoted as NSS, NSC, NSI, respectively) were optimized. The results indicated that the optimum concentration of the NS layer was 5 % at a water contact angle (WCA) 110.5°. Further, Fourier transform infrared spectra showed the presence of SiOSi and SiCH3 groups in the NSS, NSC, and NSI films, and X-ray diffraction spectra indicated that original structures of these films were disordered. Moreover, the surface morphology, mechanical properties, and light transmission were affected by the NS layer, and the optimal layer was found to be NSI. After 10 days of storage at 100 % humidity, the NSI film exhibited low water vapor adsorption (37.22 g) and permeability (0.1484 g/m·s·Pa·10-11) and a high WCA (110.2°). In addition, the NSI film exhibited a visible color shift with an increasing pH of the buffer solution. A monitoring test of fish freshness showed that the NSI film displayed a distinctive color change corresponding to fish spoilage during 14 days of storage. This indicates that NSI has high potential in indicator film applications.

Fabrication of green colorimetric smart packaging based on basil seed gum/chitosan/red cabbage anthocyanin for real-time monitoring of fish freshness

Novel green intelligent films based on basil seed gum (BSG)/chitosan containing red cabbage extract (RCA) (0, 2.5, 5, and 10, % (v/v)) as a colorimetric indicator for food freshness detection were fabricated by casting method. The physicochemical, barrier, mechanical, and antioxidant characteristics, as well as sensitivity to pH and ammonia gas of smart edible packaging films, were investigated. The interaction of anthocyanin extract as a natural dye with biopolymers in films characterized by FTIR spectroscopy and SEM images revealed their suitable compatibility. The film with maximum anthocyanin content (10% (v/v)) appeared robust color changes against various pH and ammonia gas levels. The color of indicator films when exposed to alkaline, neutral and acidic buffers are indicated with green, blue, and red colors, respectively. The DPPH radical scavenging activity of smart BSG/chitosan films improved from 23% to 90.32% with increasing RCA content from 2.5 to 10% (v/v). Generally, the incorporation of RCA in film structure enhanced their solubility, WVP, ΔE, turbidity, and flexibility, and reduced tensile strength. The observations successfully confirmed the efficacy of pH-sensitive indicator smart film based on BSG/chitosan for evaluation of fish spoilage during storage.

Cross-linked CMC/Gelatin bio-nanocomposite films with organoclay, red cabbage anthocyanins and pistacia leaves extract as active intelligent food packaging: colorimetric pH indication, antimicrobial/antioxidant properties, and shrimp spoilage tests

Multifunctional food packaging films were produced from crosslinked carboxymethyl cellulose/gelatin (CMC/Ge) bio-nanocomposites incorporated with Ge-montmorillonite (OM) nanofiller, anthocyanins (ATH) from red cabbage as colorimetric pH-indicator, and pistacia leaves extract (PE) as active agent. The influence of additives on the structural, physical, and functional properties of the films was investigated. The results showed that ATH and PE caused color alteration and reduced transparency. However, they improved the UV light barrier ability by 98 %, with less impact from OM, despite its well-dispersed state in the matrix. Increasing PE content in the bio-nanocomposite films caused an increase in compactness and surface roughness, reduction in moisture content (15.10-12.33 %), swelling index (354.55-264.58 %), surface wettability (contact angle 80.1-92.49°), water vapor permeability (7.37-5.69 × 10¹⁰ g m^-1s^-1Pa^-1), and nano-indentation mechanical parameters, without affecting the thermal stability. ATH-included films demonstrated color pH-sensitivity with improved ATH color stability through the ATH-Al³⁺ chelates formation. PE-added films exhibited effective antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, reaching 93 % of inhibition, and antimicrobial properties with biocidal effects for PE-rich film. The shrimp spoilage test showed that the T-1.5PE film offered the strongest active intelligent response. The CMC/Ge-based bio-nanocomposite films endowed with antioxidant/antimicrobial properties and colorimetric pH-sensitivity have promising potential for food packaging application.

pH-sensitive smart indicators based on cellulose and different natural pigments for tracing kimchi ripening stages

Five natural pigments including water-soluble [butterfly pea (BP), red cabbage (RC), and aronia (AR)] and alcohol-soluble [shikonin (SK) and alizarin (ALZ)] were extracted, characterized, and loaded onto cellulose for preparing pH-sensitive indicators. The indicators were tested their color response efficiency, gas sensitivity, response to lactic acid, color release, and antioxidant activity. Cellulose-water soluble indicators showed more obvious color changes than alcohol-soluble indicators in lactic acid solution and pH solutions (1-13). All cellulose-pigment indicators exhibited prominent sensitivity to ammonia compared to acidic vapor. Antioxidant activity and release behavior of the indicators were influenced by pigment type and simulants. Kimchi packaging test was carried out using original and alkalized indicators. The alkalized indicators were more effective in showing visible color changes during kimchi storage than the original indicators, and cellulose-ALZ displayed the most distinct color change from violet (fresh kimchi, pH 5.6, acidity 0.45 %) to gray (optimum fermented kimchi, pH 4.7, acidity 0.72 %), and to yellow (over fermented kimchi, pH 3.8, acidity 1.38 %) which followed by BP, AR, RC, SK respectively. The findings of the study suggest that the alkalization method could be used to show noticeable color changes in a narrow pH range for application with acidic foods.

The production of pH indicator Ca and Cu alginate ((1,4)- β -d-mannuronic acid and α -l-guluronic acid) cryogels containing anthocyanin obtained via red cabbage extraction for monitoring chicken fillet freshness

In recent days, intelligent food packaging has gained attention due to consumers' needs and monitoring of the freshness of food. Biopolymers are used to produce matrix parts and dye chemicals, because of their unique properties, such as biodegradability and biocompatibility. In this study, alginate molecules and anthocyanins were used to produce to monitor chicken fillet freshness via pH response characteristics. Anthocyanins' color and UV characteristics at different pHs were investigated. The obtained anthocyanin solution showed visible color response at different pH level. In the red cabbage extract, the anthocyanin concentration was as 0.65 ± 0.03 mg/g. Alginate and extracted anthocyanins from red cabbage were mixed at the solution phase, then metal alginate hydrogels were synthesized via crosslinking Ca²⁺ and Cu²⁺ with alginate molecules. Due to the porous structure of the cryogels, hydrogels were freeze dried at -80 °C for 24 h at vacuum atmosphere. The obtained cryogel indicated significant color changes from pH 4 to pH 10, and at a basic environment, the color change was observed with the naked eye. The porosity amounts and sizes of the produced cryogels were examined, the average pore amount of cryogels was found to be 85.46 ± 4.36 %, and the average pore size 97.98 ± 26.20 μm. Furthermore, it was seen that the color change was not directly related to the porosity, but the interaction of anthocyanin and metal alginate matrix effected color changes degree of cryogels. Due to the electronegativity of Cu²⁺ ions, and the use of a low amount of anthocyanin was found to be more suitable for color change. The color was changed to blue-purple while total volatile basic nitrogen content increased to 46.67 mg/100 g from 14.00 mg/100 g. As a result, prepared cryogels should be a better candidates for use as a freshness indicator and intelligent packaging.

Novel Features of Cellulose-Based Films as Sustainable Alternatives for Food Packaging

Packaging plays an important role in food quality and safety, especially regarding waste and spoilage reduction. The main drawback is that the packaging industry is among the ones that is highly dependent on plastic usage. New alternatives to conventional plastic packaging such as biopolymers-based type are mandatory. Examples are cellulose films and its derivatives. These are among the most used options in the food packaging due to their unique characteristics, such as biocompatibility, environmental sustainability, low price, mechanical properties, and biodegradability. Emerging concepts such as active and intelligent packaging provides new solutions for an extending shelf-life, and it fights some limitations of cellulose films and improves the properties of the packaging. This article reviews the available cellulose polymers and derivatives that are used as sustainable alternatives for food packaging regarding their properties, characteristics, and functionalization towards active properties enhancement. In this way, several types of films that are prepared with cellulose and their derivatives, incorporating antimicrobial and antioxidant compounds, are herein described, and discussed.

Anthocyanins of Açaí Applied as a Colorimetric Indicator of Milk Spoilage: A Study Using Agar-Agar and Cellulose Acetate as Solid Support to Be Applied in Packaging

Food that is still fit for consumption is wasted in the domestic environment every day, so food packaging technologies are being developed that will monitor the quality of the products in real time. Highly perishable milk is currently one of the products that suffers most from this waste, due to its short shelf life. Active use-by date (AUBD) indicators have been shown to discriminate between fresh and spoiled milk. Colorimetric indicators undergo characteristic changes in their chemical structure, causing abrupt color changes. Among the polymeric materials studied that may function as solid support are cellulose acetate (CA) and agar-agar (AA). The AA colorimetric indicator proved to be more suitable as a solid support due to its ability to maintain the color change properties of the anthocyanin and its high colorimetric performance. The technique was shown to be capable of indicating, in real time, changes in milk quality.

Dietary polyglycosylated anthocyanins, the smart option? A comprehensive review on their health benefits and technological applications

Over the years, anthocyanins have emerged as one of the most enthralling groups of natural phenolic compounds and more than 700 distinct structures have already been identified, illustrating the exceptional variety spread in nature. The interest raised around anthocyanins goes way beyond their visually appealing colors and their acknowledged structural and biological properties have fueled intensive research toward their application in different contexts. However, the high susceptibility of monoglycosylated anthocyanins to degradation under certain external conditions might compromise their application. In that regard, polyglycosylated anthocyanins (PGA) might offer an alternative to overcome this issue, owing to their peculiar structure and consequent less predisposition to degradation. The most recent scientific and technological findings concerning PGA and their food sources are thoroughly described and discussed in this comprehensive review. Different issues, including their physical-chemical characteristics, consumption, bioavailability, and biological relevance in the context of different pathologies, are covered in detail, along with the most relevant prospective technological applications. Due to their complex structure and acyl groups, most of the PGA exhibit an overall higher stability than the monoglycosylated ones. Their versatility allows them to act in a wide range of pathologies, either by acting directly in molecular pathways or by modulating the disease environment attributing an added value to their food sources. Their recent usage for technological applications has also been particularly successful in different industry fields including food and smart packaging or in solar energy production systems. Altogether, this review aims to put into perspective the current state and future research on PGA and their food sources.

Ionic Strength of Methylcellulose-Based Films: An Alternative for Modulating Mechanical Performance and Hydrophobicity for Potential Food Packaging Application

The growing environmental concern with the inappropriate disposal of conventional plastics has driven the development of eco-friendly food packaging. However, the intrinsic characteristics of polymers of a renewable origin, e.g., poor mechanical properties, continue to render their practical application difficult. For this, the present work studied the influence of ionic strength (IS) from 0 to 500 mM to modulate the physicochemical properties of methylcellulose (MC). Moreover, for protection against biological risks, Nisin-Z was incorporated into MC’s polymeric matrices, providing an active function. The incorporation of salts (LiCl and MgCl2) promoted an increase in the equilibrium moisture content in the polymer matrix, which in turn acted as a plasticizing agent. In this way, films with a hydrophobic surface (98°), high true strain (85%), and low stiffness (1.6 mPa) can be manufactured by addition of salts, modulating the IS to 500 mM. Furthermore, films with an IS of 500 mM, established with LiCl, catalyzed antibacterial activity against E. coli, conferring synergism and extending protection against biological hazards. Therefore, we demonstrated that the IS control of MC dispersion presents a new alternative to achieve films with the synergism of antibacterial activity against Gram-negative bacteria in addition to flexibility, elasticity, and hydrophobicity required in various applications in food packaging.

Application of Red Cabbage Anthocyanins as pH-Sensitive Pigments in Smart Food Packaging and Sensors

Anthocyanins are excellent antioxidant/antimicrobial agents as well as pH-sensitive indicators that provide new prospects to foster innovative smart packaging systems due to their ability to improve food shelf life and detect physicochemical and biological changes in packaged food. Compared with anthocyanins from other natural sources, red cabbage anthocyanins (RCAs) are of great interest in food packaging because they represent an acceptable color spectrum over a broad range of pH values. The current review addressed the recent advances in the application of RCAs in smart bio-based food packaging systems and sensors. This review was prepared based on the scientific reports found on Web of Science, Scopus, and Google Scholar from February 2000 to February 2022. The studies showed that the incorporation of RCAs in different biopolymeric films could affect their physical, mechanical, thermal, and structural properties. Moreover, the use of RCAs as colorimetric pH-responsive agents can reliably monitor the qualitative properties of the packaged food products in a real-time assessment. Therefore, the development of smart biodegradable films using RCAs is a promising approach to the prospect of food packaging.

Characterization and Release Kinetics Study of Active Packaging Films Based on Modified Starch and Red Cabbage Anthocyanin Extract

Active packaging films were prepared by adding red cabbage anthocyanin extract (RCAE) into acetylated distarch phosphate (ADSP). This paper investigated the influence of the interaction relationship between RCAE and the film matrix on the structure, barrier, antioxidant and release properties of active films. Sixteen principal compounds in RCAE were identified as anthocyanins based on mass spectroscopic analysis. Micromorphological observations indicated that the RCAE distribution uniformity in the films decreased as the RCAE content increased. When the concentration of RCAE was not higher than 20%, the moisture absorption and oxygen permeability of films decreased. The stability of RCAE in the films was enhanced by the electrostatic interaction between RCAE and ADSP with the formation of hydrogen bonds, which facilitated the sustainability of the antioxidant properties of films. The release kinetics of RCAE proved that the release rate of RCAE in active films was the fastest in distilled water, and Fickian’s law was appropriate for portraying the release behavior. Moreover, the cytocompatibilty assay showed that the test films were biocompatible with a viability of >95% on HepG2 cells. Thus, this study has established the suitability of the films for applications in active and food packaging.

Development and Investigation of Zein and Cellulose Acetate Polymer Blends Incorporated with Garlic Essential Oil and β-Cyclodextrin for Potential Food Packaging Application

The obtainment of new materials with distinct properties by mixing two or more polymers is a potential strategy in sustainable packaging research. In the present work, a blend of cellulose acetate (CA) and zein (60:40 wt/wt CA:zein) was manufactured by adding glycerol or tributyrin as plasticizers (30% wt/wt), and garlic essential oil (GEO), complexed (IC) or not with β-cyclodextrin (βCD), to produce active packaging. Blends plasticized with tributyrin exhibited a more homogeneous surface than those containing glycerol, which showed major defects. The blends underperformed compared with the CA films regarding mechanical properties and water vapor permeability. The presence of IC also impaired the films’ performance. However, the blends were more flexible than zein brittle films. The films added with GEO presented in vitro activity against Listeria innocua and Staphylococcus aureus. The IC addition into films, however, did not ensure antibacterial action, albeit that IC, when tested alone, showed activity against both bacteria. These findings suggest that the mixture of CA and plasticizers could increase the range of application of zein as a sustainable packaging component, while essential oils act as a natural bioactive to produce active packaging.

Red cabbage anthocyanins: Stability, extraction, biological activities and applications in food systems

Red cabbage anthocyanins are of great interest as natural food colorants in the food industry; as they represent the color over a broad range of pH-values compared to anthocyanins from other natural sources. It is important to select an appropriate technique with high recovery of anthocyanins from red cabbage, among which extraction with organic solvents is the most applied extraction method. Currently, novel extraction techniques are employed as an alternative to the solvent extraction method, providing advantages such as higher anthocyanin recovery in a shorter time, lower solvent utilization, and minimum quality degradation. However, the incorporation of extracted anthocyanins into foodstuffs and pharmacological products is limited due to their low bioavailability and relative instability toward environmental adverse conditions, such as pH, temperature, enzymes, light, oxygen and ascorbic acid. In addition to increased structural stability of anthocyanins through glycosylation and acylation, their stability could be improved by copigmentation and encapsulation.

Immobilization of roselle anthocyanins into polyvinyl alcohol/hydroxypropyl methylcellulose film matrix: Study on the interaction behavior and mechanism for better shrimp freshness monitoring

The roselle anthocyanin extracts (RAE) were immobilized into polyvinyl alcohol (PVA)/hydroxypropyl methylcellulose (HPMC) film matrix, their interaction behavior and mechanism was fully understood for better shrimp freshness monitoring. Structural characterizations revealed RAE was firmly immobilized PVA/HPMC matrix by hydrogen bonds. With increasing RAE contents, dramatic increases of film thickness (from 15.90 ± 0.14 to 23.20 ± 3.35 μm), tensile strength (from 45.66 ± 1.07 to 56.98 ± 0.24 MPa), light barrier and active properties (increased by 83.18% for antioxidant and 146.91%, 59.18% for antibacterial activity against E. coli and S. aureus) were observed, while hydrophobic properties decreased significantly. Owing to great ammonia-sensitive ability, the PVA/HPMC/RAE (PHR) films were applied on shrimp freshness qualitative monitoring and greater visible color variations were identified with increasing RAE contents. Furthermore, mathematical models were established for quantitative monitoring. In conclusion, with the increasing RAE contents, the tighter interaction between RAE and PVA/HPMC matrix contributed to the better functional properties and freshness monitoring effects of PHR films.

Chitosan-poly(vinyl alcohol) intelligent films fortified with anthocyanins isolated from Clitoria ternatea and Carissa carandas for monitoring beverage freshness

Biodegradable chitosan-poly(vinyl alcohol) films containing natural anthocyanin-rich extracts were prepared using solvent casting method and employed as intelligent indicators for monitoring beverages freshness. The surface and cross-sectional scanning electron micrograph indicated a compact structure for the intelligent films, whereas the atomic force micrograph indicated a 16.22 and 20.31 nm increase in surface roughness for Clitoria ternatea and Carissa carandas extract incorporated films, respectively. Moreover, the test films demonstrated enhanced radical scavenging efficacy. The extracts and anthocyanin incorporated films presented excellent colorimetric changes at pH 2 to 8. In addition, the C. ternatea test films showed changes in color for juice stored at 25 °C after 72 h. Photo-degradability results indicated stability of test films stored in dark at 4 °C and 25 °C, whereas leaching study indicated the release of ≤2.0% anthocyanin after 24 h. The cytocompatibilty assay showed that the test and control films were biocompatible with a viability of >80% on HaCat cells. The results demonstrated that the incorporation of anthocyanins-rich extracts into chitosan-poly(vinyl alcohol) did not significantly interfere with the films properties (p > 0.05). The natural anthocyanin incorporated films demonstrated good pH sensing property that could be further explored for monitoring of beverages freshness.