Active gellan gum/purple sweet potato composite films capable of monitoring pH variations

Intelligent pH-responsive ratiometric fluorescent nanofiber films for visual and real-time seafood freshness monitoring

In this study, polyvinyl alcohol (PVA)-based ratiometric fluorescence nanofiber films with salicylamide (SA) as the response signal, rhodamine B (RhB) as the internal reference were prepared using electrospinning technique, and reducing their water solubility by glutaraldehyde (G) crosslinked. The RhB and SA were successfully immobilized in the PVA substrate. Moreover, RhB and SA improved the water resistance, water vapor barrier, and mechanical strength of the nanofiber films, among the PVA nanofiber films containing RhB and 400 mg SA (PVA/RhB/4SA-G) showed the best packaging performance. Meanwhile, it exhibited high sensitivity to ammonia (limit of detection was 0.97 ppm), and could effectively distinguish the freshness states of shrimp stored at 4 and 25 °C by displaying a distinct shift from light pink to bright purple fluorescence. Moreover, the migration studies confirmed the safety of PVA/RhB/4SA-G. Therefore, the fabricated PVA/RhB/4SA-G can be utilized as a promising intelligent packaging for monitoring seafood freshness in real-time.

Development and investigation of a polysaccharide ternary nanocomposite based on basil seed gum/graphene oxide/anthocyanin for intelligent food packaging

A new pH-sensitive intelligent packaging system was developed composed of extracted and purified basil seed gum (BG) containing aqueous malva sylvestris extract (MS) and varying amounts of synthesized graphene oxide (GO). In the following, the characteristics of prepared films including spectroscopic, physio-mechanical, thermogravimetry, fracture-surface morphology, anthocyanin release, and pH and TVB-N sensitivity, were investigated. Our results revealed that the addition of 0.5 wt % MS into the BG matrix induced pH sensitivity to the film and resulted in a visible color change from pH 2.0 to 14.0; however, it reduced the thermal and physio-mechanical properties. In this regard, the effective presence of the optimum concentration of GO (0.25 wt%) in enhancing the mechanical and thermal properties of the BG-MS films was shown. Moreover, inspecting the release kinetics demonstrated a controllable release for BG-MS-GO film compared to the BG-MS film in 48 h. Furthermore, the total volatile basic nitrogen (TVB-N) content and pH value were shown to be highly correlated with the color changes of the freshness indicator film during the storage of salmon fillets at 25 °C for 36 h. Therefore, it was shown that BG-MS-GO film can be used as a highly effective freshness/spoilage indicator of proteinic products.

Recent Advances in Purple Sweet Potato Anthocyanins: Extraction, Isolation, Functional Properties and Applications in Biopolymer-Based Smart Packaging

Petroleum-based plastic packaging materials have negative impacts on the environment and food safety. Natural biopolymer-based food packaging materials are the proper substitutes for plastic-based ones, which is because biopolymers are nontoxic, biodegradable and even edible. The incorporation of bioactive and functional substances into a biopolymer-based film matrix can produce novel smart packaging materials. Anthocyanins, one class of natural colorants with potent antioxidant activity and pH-response color-changing ability, are suitable for producing biopolymer-based smart packaging films. The purple sweet potato is a functional food rich in anthocyanins. In the past decade, numerous studies have reported the extraction of anthocyanins from purple sweet potato and the utilization of purple sweet potato anthocyanins (PSPAs) in biopolymer-based smart packaging film production. However, no specific review has summarized the recent advances on biopolymer-based smart packaging films containing PSPAs. Therefore, in this review, we aim to systematically summarize the progress on the extraction, isolation, characterization, purification and functional properties of PSPAs. Moreover, we thoroughly introduce the preparation methods, physical properties, antioxidant and antimicrobial activity, pH sensitivity, stability and applications of biopolymer-based smart packaging films containing PSPAs. Factors affecting the extraction and functional properties of PSPAs as well as the properties of biopolymer-based films containing PSPAs are discussed.

pH-triggered bilayer film based on carboxymethyl cellulose/zein/Eudragit L100 with purple cabbage anthocyanin for monitoring pork freshness

A novel pH-triggered bilayer film was composed of zein (Z), carboxymethylcellulose (CMC), Eudragit L100 (L100), and purple cabbage anthocyanin (PCA), followed by casting for monitoring pork freshness during storage at 4 °C and 25 °C. This bilayer film was employed to encapsulate anthocyanins, preventing anthocyanins oxidation and photodegradation. Additionally, under pH 6, this film ruptures and releases anthocyanins, inducing a sudden color change in the indicator film, significantly reducing errors in freshness indications. Notably, the ZCLP8% film had excellent stability and pH response properties. The performance of the ZCLP8% film in monitoring pork freshness was evaluated. When the concentration of pork TVB-N reached 15.59 mg/100 g (pH = 6.35), the bilayer film was ruptured, and the release rate of PCA was 85.52 %, which was a significant change in the color of the bilayer film compared with that at pH = 5. Therefore, this work addresses the limitation that anthocyanin-based intelligent films are subject to judgment errors when applied, opening new possibilities for food freshness differentiation monitoring.

Advancements in Gellan Gum-Based Films and Coatings for Active and Intelligent Packaging

Gellan gum (GG) is a natural polysaccharide with a wide range of industrial applications. This review aims to investigate the potential of GG-based films and coatings to act as environmentally friendly substitutes for traditional petrochemical plastics in food packaging. GG-based films and coatings exhibit versatile properties that can be tailored through the incorporation of various substances, such as plant extracts, microorganisms, and nanoparticles. These functional additives enhance properties like the light barrier, antioxidant activity, and antimicrobial capabilities, all of which are essential for extending the shelf-life of perishable food items. The ability to control the release of active compounds, along with the adaptability of GG-based films and coatings to different food products, highlights their effectiveness in preserving quality and inhibiting microbial growth. Furthermore, GG-based composites that incorporate natural pigments can serve as visual indicators for monitoring food freshness. Overall, GG-based composites present a promising avenue for the development of sustainable and innovative food packaging solutions.

A comparative study on the structure, physical property and halochromic ability of shrimp freshness indicators produced from nine varieties of steamed purple sweet potato

Nine varieties of purple sweet potato were steamed and used for the production of shrimp freshness indicators. The impact of purple sweet potato's variety on the structure, physical property and halochromic ability of indicators was determined. Results showed different varieties of purple sweet potato had different starch, crude fiber, pectin, protein, fat and total anthocyanin contents. The microstructure, crystallinity, moisture content, water vapor permeability, tensile strength and elongation at break of indicators were affected by crude fiber content in purple sweet potato. The color, transmission and halochromic ability of indicators was associated with the total anthocyanin content in purple sweet potato. Freshness indicators produced from Fuzi No. 1, Ganzi No. 6, Ningzi No. 2, Ningzi No. 4, Qining No. 2 and Qining No. 18 of purple sweet potato were suitable to indicate shrimp freshness. This study provides useful information on screening suitable varieties of purple sweet potato for intelligent packaging.

Intelligent double-layer film based on gellan gum/modified anthocyanin/curcumin/sodium alginate/zinc oxide for monitoring shrimp freshness

In this study, intelligent double-layer films were prepared using modified black rice anthocyanin (MBRA)-curcumin (CUR)-gellan gum (GG) as the inner indicator layer and sodium alginate (ALG)‑zinc oxide (ZnO) as the outer antimicrobial layer. The bilayer films were successfully prepared, as revealed by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction measurements. The mechanical characteristics, moisture content, and water vapor resistance of GG-MBRA/CUR1@ALG-ZnO, GG-MBRA/CUR2@ALG-ZnO, and GG-MBRA/CUR3@ALG-ZnO films showed significant enhancement compared to GG-MBRA/CUR3 and ALG-ZnO films. The bilayer films exhibited excellent pH responsiveness and reacted effectively to ammonia. The outer layer significantly improved the antioxidant and antibacterial properties of the inner layer. When the films were applied to shrimp, it was found that the double-layer films not only monitored the freshness of the shrimp in real-time but also were influential in extending the shelf life of the shrimp by about 1 d. Therefore, the double-layer film demonstrated potential as a smart packaging material for real-time monitoring of meat product freshness.

Smart colorimetric indicator films prepared from chitosan and polyvinyl alcohol with high mechanical strength and hydrophobic properties for monitoring shrimp freshness

This work aimed to develop and characterize a colorimetric indicator films based on chitosan (CS), polyvinyl alcohol (PVA), and shikonin (SKN) from radix Lithospermi by casting method. The prepared films can serve as smart packaging for monitoring shrimp freshness which having excellent antimicrobial and antioxidant activity. The shikonin containing films have better hydrophobicity, barrier properties, and tensile strength. The release kinetics analysis shows that the loading amount causes a prolonged release of SKN from the prepared films. Increasing SKN in the CS/PVA film from 1 wt% to 2 wt% improved antibacterial effect for 24 h. Additionally, pH-sensitive color shifts from reddish (pH 2) to purple-bluish (pH 13) were visually seen in shikonin based solutions as well as films. The CS/PVA/SKN film detected shrimp deterioration at three temperatures (25, -20, and 4 °C) through color change. This study introduces a favorable approach for smart packaging in the food industry using multifunctional films.

High-compatibility properties of Aronia melanocarpa extracts cross-linked chitosan/polyvinyl alcohol composite film for intelligent food packaging

Although the active and intelligent properties of rich in anthocyanin extracts added to films have been extensively studied, there remains a sparsity of research pertaining to the miscibility of blended films. This work focused on the miscibility of the chitosan/polyvinyl alcohol (CP) film caused by the addition of Aronia melanocarpa extracts (AME), which are rich anthocyanins and phenolic acids, and its effect on physicochemical and functional properties. AME facilitated the amidation reaction and ionic interaction of chitosan in CP films, leading to loss of the crystallinity degree of chitosan. Furthermore, the crystal disruption promoted the formation of hydrogen bonds with polyvinyl alcohol (PVA) with the promoted miscibility. CP film incorporated with 8 % AME possessed the highest tensile strength (26.79 MPa), and elongation at break (66.38 %) as well as excellent ultraviolet-visible (UV-vis) light barrier property, water vapor barrier properties, due to its high miscibility degree. Moreover, this film also showed excellent antioxidant, antibacterial activity, and pH response function, which could be used to monitor the storage of highly perishable shrimp. Hence, the AME provided extra functionality and improved miscibility between chitosan and PVA, which showed great potential for the preparation of high-performance bioactive-fortified and intelligent food packaging films.

Fabrication of multifunctional ethyl cellulose/gelatin-based composite nanofilm for the pork preservation and freshness monitoring

In this study, an active and intelligent nanofilm for monitoring and maintaining the freshness of pork was developed using ethyl cellulose/gelatin matrix through electrospinning, with the addition of natural purple sweet potato anthocyanin. The nanofilm exhibited discernible color variations in response to pH changes, and it demonstrated a higher sensitivity towards volatile ammonia compared with casting film. Notably, the experimental findings regarding the wettability and pH response performance indicated that the water contact angle between 70° and 85° was more favorable for the smart response of pH sensitivity. Furthermore, the film exhibited desirable antioxidant activities, water vapor barrier properties and also good antimicrobial activities with the incorporation of ε-polylysine, suggesting the potential as a food packaging film. Furthermore, the application preservation outcomes revealed that the pork packed with the nanofilm can prolong shelf life to 6 days, more importantly, a distinct color change aligned closely with the points indicating the deterioration of the pork was observed, changing from light pink (indicating freshness) to light brown (indicating secondary freshness) and then to brownish green (indicating spoilage). Hence, the application of this multifunctional film in intelligent packaging holds great potential for both real-time indication and efficient preservation of the freshness of animal-derived food items.

Anti-bacterial films developed by incorporating shikonin extracted from radix lithospermi and nano-ZnO into chitosan/polyvinyl alcohol for visual monitoring of shrimp freshness

In recent years, the utilization of smart colorimetric packaging films for monitoring food freshness has garnered significant concentration. However, their limited tensile strength, hydrophobicity, antioxidant, and antibacterial properties have been substantial barriers to widespread adoption. In this study, we harnessed the potential of biodegradable materials, specifically chitosan/polyvinyl alcohol, alongside shikonin extracted from Radix Lithospermi and ZnO nanoparticles, to create a novel colorimetric sensing film. This film boasts an impressive tensile strength of 82.36 ± 2.13 MPa, enhanced hydrophobic characteristics (exemplified by a final contact angle of 99.81°), and outstanding antioxidant and antibacterial properties. It is designed for real-time monitoring of shrimp freshness. Additionally, we verified the effectiveness of this sensing film in detecting shrimp freshness across varying temperature conditions, namely 25 °C and 4 °C was validated through the measurement of total volatile basic nitrogen (TVB-N). Visual inspection unequivocally revealed a transition in color from dark red to purple-light blue and finally to dark bluish providing a clear indication of shrimp spoilage, which demonstrated a strong correlation with the TVB-N content in shrimp measured through standard laboratory procedures. The colorimetric sensing film developed in this study holds great promise for creating smart labels with exceptional antioxidant and antibacterial properties, tailored for visual freshness monitoring of shrimp.

Preparation and characterization of smart indicator films based on gellan gum/modified black rice anthocyanin/curcumin for improving the stability of natural anthocyanins

In order to improve the stability of natural anthocyanins in intelligent packaging materials, this work first modified black rice anthocyanins (BRA) by acylation with acetic acid, then modified the acylated BRA by co-coloring with different ratios of curcumin (CUR), and finally added the mixed indicator to gellan gum (GG) to develop intelligent packaging films with good stability. The UV spectroscopy results showed that acetic acid had successfully modified the BRA, while the thermal, photostability and pH stability of the modified black rice anthocyanin (MBRA) were significantly enhanced. The indicators of BRA, MBRA and MBRA mixed with CUR showed excellent pH sensitivity in different buffer solutions. The SEM, FT-IR and XRD results indicated apparent crystalline aggregates on the surface of the films added with a high concentration of CUR. Compared with GG-BRA film, GG-MBRA film improved all properties except for antioxidant performance. Notably, the GG-MBRA/CUR series composite films exhibited significant improvements over the GG-BRA and GG-MBRA films in terms of optical characteristics, mechanical properties, water vapor barrier, oxidation resistance, and color stability; meanwhile, all films exhibited excellent pH sensitivity. Considering all the properties of the films, GG-MBRA/CUR3 film has tremendous potential as a smart indicator film for improving freshness accuracy.

Preparation of an elderberry anthocyanin film and fresh-keeping effect of its application on fresh shrimps

A smart packaging film was developed employing the pH-indicating activity of elderberry anthocyanins to solve the problem of refrigerated food freshness monitoring. The effect of elderberry anthocyanins on the properties of gellan gum, gelatin composite films and preservation of fresh shrimp as an indicator of freshness was investigated. The results showed that the elderberry anthocyanin-gellan gum/gelatin film had improved on film thickness (7.8×10-2 mm), TS (tensile strength) (14.57×103 MPa), WVP (water vapor permeability) (36.96×10-8 g/m·s·Pa), and a reduced EAB (elongation at break) (17.92%), and water solubility (water-soluble time of 60.5 s). SEM (scanning electron microscopy) and FTIR (infrared spectrum analysis) showed excellent compatibility between its components. Moreover, the elderberry anthocyanin film exhibited good mechanical properties and pH indication effects. Therefore, the film can be considered suitable for maintaining the quality of fresh shrimp. The results could provide a reference for research and development into new active intelligent packaging films.

A Novel Indicator Based on Polyacrylamide Hydrogel and Bromocresol Green for Monitoring the Total Volatile Basic Nitrogen of Fish

An intelligent indicator was developed by immobilizing bromocresol green (BCG) within the polyacrylamide (PAAm) hydrogel matrix to monitor the total volatile basic nitrogen (TVB-N) content of fish. The FTIR analysis indicated that BCG was effectively incorporated into the PAAm through the formation of intermolecular hydrogen bonds. A thermogravimetric analysis (TGA) showed that the PAAm/BCG indicator had a mere 0.0074% acrylamide monomer residue, meanwhile, the addition of BCG improved the thermal stability of the indicator. In vapor tests with various concentrations of trimethylamine, the indicator performed similarly at both 4 °C and 25 °C. The total color difference values (ΔE) exhibited a significant linear response to TVB-N levels ranging from 4.29 to 30.80 mg/100 g at 4 °C (R2 = 0.98). Therefore, the PAAm/BCG indicator demonstrated stable and sensitive color changes based on pH variations and could be employed in smart packaging for real-time assessment of fish freshness.

Development of a pH-sensing indicator for shrimp freshness monitoring: Curcumin and anthocyanin-loaded gelatin films

An intelligent pH-sensing indicator containing Roselle (Hibiseus sabdariffa L.) (RS) anthocyanin and curcumin (CR) was developed and characterized as on-package indicator tags to check the freshness of shrimp during the storage at 4°C. FE-SEM and FT-IR analysis showed that RS and CR were successfully immobilized in the gelatin-glycerol film-forming substrate. The addition of various natural dyes increased the thickness and antioxidant action of the colorimetric film. To assess the response to changes in the pH, the colorimetric film was immersed in different buffers. Based on volatile amines secreted by shrimp, a test application of a colorimetric film containing natural dyes at a ratio of CR:RS = 1:4 (v/v) was conducted in shrimp at 4°C. The total volatile basic nitrogen (TVB-N) and the pH of shrimp were monitored during refrigerated storage for 10 days, and the color changes of the indicator were recorded simultaneously. The results indicated that the designed colorimetric film could produce various colors, which are thought to be indicative of the freshness and spoilage of packaged shrimp. Therefore, the target film can be utilized as a promising smart packaging material for monitoring the freshness of shrimp and aquatic products in real time.

Biopolymer-Based Sustainable Food Packaging Materials: Challenges, Solutions, and Applications

Biopolymer-based packaging materials have become of greater interest to the world due to their biodegradability, renewability, and biocompatibility. In recent years, numerous biopolymers-such as starch, chitosan, carrageenan, polylactic acid, etc.-have been investigated for their potential application in food packaging. Reinforcement agents such as nanofillers and active agents improve the properties of the biopolymers, making them suitable for active and intelligent packaging. Some of the packaging materials, e.g., cellulose, starch, polylactic acid, and polybutylene adipate terephthalate, are currently used in the packaging industry. The trend of using biopolymers in the packaging industry has increased immensely; therefore, many legislations have been approved by various organizations. This review article describes various challenges and possible solutions associated with food packaging materials. It covers a wide range of biopolymers used in food packaging and the limitations of using them in their pure form. Finally, a SWOT analysis is presented for biopolymers, and the future trends are discussed. Biopolymers are eco-friendly, biodegradable, nontoxic, renewable, and biocompatible alternatives to synthetic packaging materials. Research shows that biopolymer-based packaging materials are of great essence in combined form, and further studies are needed for them to be used as an alternative packaging material.

A double-layer smart film based on gellan gum/modified anthocyanin and sodium carboxymethyl cellulose/starch/Nisin for application in chicken breast

In order to overcome this challenge of poor stability of natural anthocyanins in intelligent packaging materials, roselle anthocyanin (RA) was first modified by acetic acid, and then a double-layer smart indication antimicrobial film was developed using modified roselle anthocyanin (MRA)-gellan gum (GG) as the inner layer and sodium carboxymethyl cellulose (CMC)-starch (ST)-Nisin as the outer layer. UV spectra revealed that acetic acid was successfully grafted onto RA, which dramatically improved their thermal stability, antioxidant capabilities, photostability, and pH stability. The bilayer films were successfully prepared, as revealed by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction measurements. In comparison to GG-MRA and CMC-ST-Nisin films, the water content, water solubility, mechanical characteristics, water vapor barrier, oxygen barrier, and hydrophobicity of GG-MRA@CMC-ST-Nisin films were significantly enhanced. The presence of the outer layer films significantly enhanced the UV-vis light barrier, opacity, antioxidant and antibacterial properties of the inner layer films. When the films were applied to chicken breast, it was found that the indicator films not only monitored the freshness of the chicken in real-time but also that the GG-MRA film and the double-layer film were effective in extending the shelf life of the chicken by 1 and 2 days, respectively, compared to the control group.

A collagen-based theranostic wound dressing with visual, long-lasting infection detection capability

Continuous wound monitoring is one strategy to minimise infection severity and inform prompt variations in therapeutic care following infection diagnosis. However, integration of this functionality in therapeutic wound dressings is still challenging. We hypothesised that a theranostic dressing could be realised by integrating a collagen-based wound contact layer with previously demonstrated wound healing capability, and a halochromic dye, i.e. bromothymol blue (BTB), undergoing colour change following infection-associated pH changes (pH: 5-6 ➔ >7). Two different BTB integration strategies, i.e. electrospinning and drop-casting, were pursued to introduce long-lasting visual infection detection capability through retention of BTB within the dressing. Both systems had an average BTB loading efficiency of 99 wt% and displayed a colour change within 1 min of contact with simulated wound fluid. Drop-cast samples retained up to 85 wt% of BTB after 96 h in a near-infected wound environment, in contrast to the fibre-bearing prototypes, which released over 80 wt% of BTB over the same time period. An increase in collagen denaturation temperature (DSC) and red shifts (ATR-FTIR) suggest the formation of secondary interactions between the collagen-based hydrogel and the BTB, which are attributed to count for the long-lasting dye confinement and durable dressing colour change. Given the high L929 fibroblast viability in drop-cast sample extracts (92 %, 7 days), the presented multiscale design is simple, cell- and regulatory-friendly, and compliant with industrial scale-up. This design, therefore, offers a new platform for the development of theranostic dressings enabling accelerated wound healing and prompt infection diagnosis.

Preparation of an indicator film based on pectin, sodium alginate, and xanthan gum containing blueberry anthocyanin extract and its application in blueberry freshness monitoring

An active pH-sensitive film based on pectin-sodium alginate-xanthan gum composite film (PAX) was prepared, containing blueberry anthocyanin extract (BAEs), to monitor the freshness of blueberries. The effects of different contents of BAEs on the microstructure and physical properties of intelligent polysaccharide films were comprehensively evaluated. It was found that 75-BAEs-PAX film had a solid response to pH value and showed different and easily distinguishable colors at different pH values. In addition, when the freshness of blueberries stored at different temperatures (-1 °C, 4 °C, 10 °C, 15 °C, 25 °C) was monitored, the color of 75-BAEs-PAX film changed from purple to light pink from neutral to acidic environment, which was consistent with the change of pH value of blueberries from fresh to spoilage. The Arrhenius equation verified that the difference between the activation energy of the indicator film and the blueberry quality was less than 25 kJ/mol. Therefore, the 75-BAEs-PAX film can be used as an indicator film for blueberries freshness monitoring. In this study, the freshness of blueberries was monitored by BAEs, and the purpose of using ontology to monitor ontology was achieved. The freshness of blueberries was visualized during storage and transportation, which could effectively reduce the waste of blueberries. In the future, the method of ontology monitoring ontology could be extended to other foods.

Progress and opportunities in Gellan gum-based materials: A review of preparation, characterization and emerging applications

Gellan gum, a microbial exopolysaccharide, is biodegradable and has potential to fill several key roles in many fields from food to pharmacy, biomedicine and tissue engineering. In order to improve the physicochemical and biological properties of gellan gum, some researchers take advantage of numerous hydroxyl groups and the free carboxyl present in each repeating unit. As a result, design and development of gellan-based materials have advanced significantly. The goal of this review is to provide a summary of the most recent, high-quality research trends that have used gellan gum as a polymeric component in the design of numerous cutting-edge materials with applications in various fields.

Preparation and characterization of an intelligent film based on fish gelatin and Coleus scutellarioides anthocyanin to monitor the freshness of rainbow trout fish fillet

In this study, a pH-sensitive indicator based on fish gelatin and Coleus scutellarioides anthocyanin extract (CSAE) was prepared and characterized. Films were prepared using the solvent casting method and different levels of CSAE, including 10 ml (CSG1), 20 ml (CSG2), and 30 ml (CSG3), and 0 ml (CSG0) as a control sample. The mechanical, optical, and pH sensing of active films and the release of anthocyanins from the films were investigated. The relationship between the total volatile basic nitrogen (TVB-N) of fish fillets and a* color index of films was studied. By incorporation of CSAE, the flexibility of films increased, while the tensile strength and UV-Vis light transmittance through the films decreased (p < .05). The films containing the CSAE had a darker, yellowish, and reddish color than the control film. There was a significant relationship between the pH variation and the film color. The films had a purple color at acidic pH, and their color changed to green at an alkaline pH, indicating the sensitivity of the produced films to pH changes. There was a significant relationship between the TVB-N value of fish fillets and the a* index of the film during the 16 h storage time. The results showed that by increasing TVB-N values of the fillets, the a* color index decreased, and the films' color changed from purple to colorless. In summary, the active films prepared with fish gelatin and CSAE could be used as pH-sensitive intelligent packaging to display the freshness of fishery products.

Bilayer pH-sensitive colorimetric indicator films based on zein/gellan gum containing black rice (Oryza sativa L.) extracts for monitoring of largemouth bass (Micropterus salmoides) fillets freshness

Anthocyanins as natural pH-sensitive material can be used to determine the freshness of largemouth bass (Micropterus salmoides) fillets. However, it is easily degraded. Using zein as the protective layer to improve the light blocking ability of the film, gellan gum (GG) and black rice extracts (BRE) as the sensing layer, a bilayer colorimetric indicator film for monitoring fish spoilage was developed. The functionality and stability of bilayer film and GG single film were compared. As compared to GG single film, Zein/GG bilayer film had stronger intermolecular interactions, higher mechanical properties, and higher optical barrier properties. Notably, Zein/GG-8 % BRE bilayer film exhibited higher stability than GG-8 % BRE film when the films were exposed to room temperature for 30 days. Zein/GG-8 % BRE bilayer film were further used to monitor freshness of largemouth bass fillets during storage. Zein/GG-8 % BRE bilayer film demonstrated a noticeable color change from red to brown when largemouth bass fillets spoiled. Moreover, the ∆E of films showed a good correlation with TVB-N of largemouth bass fillets (R² = 0.985). Our research results show that the Zein/GG-BRE bilayer indicator film has great potential application prospects in monitoring fish freshness.

Colorimetric Indicators Based on Anthocyanin Polymer Composites: A Review

This review explores the colorimetric indicators based on anthocyanin polymer composites fabricated in the last decade, in order to provide a comprehensive overview of their morphological and compositional characteristics and their efficacy in their various application fields. Notably, the structural properties of the developed materials and the effect on their performance will be thoroughly and critically discussed in order to highlight their important role. Finally, yet importantly, the current challenges and the future perspectives of the use of anthocyanins as components of colorimetric indicator platforms will be highlighted, in order to stimulate the exploration of new anthocyanin sources and the in-depth investigation of all the possibilities that they can offer. This can pave the way for the development of high-end materials and the expansion of their use to new application fields.

Development of gelatin/PVA based colorimetric films with a wide pH sensing range winery solid by-product (Vinasse) for monitor shrimp freshness

Anthocyanins were extracted from a winery solid by-product (Vinasse) and added to fish gelatin (FG) and polyvinyl alcohol (PVA) matrices to create freshness monitoring labels. Three different colorimetric indicator smart films [PWE = polyvinyl alcohol with wine extract (WE), FWE = fish gelatin with WE, and PFWE = polyvinyl alcohol and FG blended film with WE] were generated and examined for their suitability to monitor the freshness of shrimp. The mechanical and optical properties, ammonia sensitivity, and colorimetric analysis of smart films were determined. Fourier transform-infrared spectroscopy (FTIR) was used to evaluate the interaction of anthocyanins with FG and PVA and changes in the film's chemical composition with storage. The film surfaces were characterized with atomic force microscopy (AFM). The incorporation of WE enhanced the films' flexibility by providing plasticizer and surfactant properties. The PWE film showed the best color stability. The FWE film showed the least amount of total color change with exposure to ammonia gas and was deemed suitable for refrigerated food packaging. The color of all indicator films showed significant changes suggesting that PWE, FWE, and PFWE films can be utilized in the intelligent packaging application for protein-rich foods to detect spoilage.

Monitoring dynamic changes in chicken freshness at 4 °C and 25 °C using pH-sensitive intelligent films based on sodium alginate and purple sweet potato peel extracts

A pH-sensitive intelligent indicator film was developed and used for monitoring dynamic changes in chicken freshness at 4 °C and 25 °C by immobilizing 0.2 %-1.0 % purple sweet potato peel extracts (PPE) with sodium alginate (SA). The films presented a wide range of colors from red-pink to green-yellow at 2-13, and the films with less PPE were more sensitive to ammonia. The color of films with 0.6 % PPE changed from pink to blue when used in monitoring chicken freshness at 4 °C (5 d) and 25 °C (60 h), which corresponded to changes in total volatile base nitrogen from 5.35 (5.35) mg/100 g to 16.2 (19.9) mg/100 g. Scanning electron microscopy and X-ray diffraction revealed that PPE improved the compactness and crystallinity of SA films, while Fourier transform infrared spectroscopy revealed hydrogen bonds between SA and PPE. Compared to SA films, the water vapor and light barrier abilities of films with 0.6 % were significantly improved (P < 0.05), there was no significant effect on tensile strength (P > 0.05), and the elongation of 0.6 % PPE films (P < 0.05) was decreased. Thus, PPE can serve as an excellent indicator of intelligent films for monitoring the freshness of meat products.

Development of Intelligent Gelatin Films Incorporated with Sappan (Caesalpinia sappan L.) Heartwood Extract

This study aimed to develop intelligent gelatin films incorporated with sappan (Caesalpinia sappan L.) heartwood extracts (SE) and characterize their properties. The intelligent gelatin film was prepared through a casting method from gelatin (3%, w/v), glycerol (25% w/w, based on gelatin weight), and SE at various concentrations (0, 0.25, 0.50, 0.75, and 1.00%, w/v). The thickness of the developed films ranged from 43 to 63 μm. The lightness and transparency of the films decreased with the increasing concentration of SE (p < 0.05). All concentrations of gelatin films incorporated with SE exhibited great pH sensitivity, as indicated by changes in film color at different pH levels (pH 1−12). Significant decreases in tensile strength were observed at 1.00% SE film (p < 0.05). The addition of SE reduced gelatin films’ solubility and water vapor permeability (p < 0.05). The chemical and physical interactions between gelatin and SE affected the absorption peaks in FTIR spectra. SE was affected by increased total phenolic content (TPC) and antioxidant activity of the gelatin film, and the 1.00% SE film showed the highest TPC (15.60 mg GAE/g db.) and antioxidant activity (DPPH: 782.71 μM Trolox/g db. and FRAP: 329.84 mM/g db.). The gelatin films combined with SE could inhibit S. aureus and E. coli, while the inhibition zone was not observed for E. coli; it only affected the film surface area. The result suggested that gelatin films incorporated with SE can be used as an intelligent film for pH indicators and prolong the shelf life of food due to their antioxidant and antimicrobial activities.

Active/intelligent packaging films developed by immobilizing anthocyanins from purple sweetpotato and purple cabbage in locust bean gum, chitosan and κ-carrageenan-based matrices

Active/intelligent packaging films were developed by incorporating purple sweetpotato anthocyanins (PSA) and purple cabbage anthocyanins (PCA) in locust bean gum/polyvinyl alcohol (LP), chitosan/polyvinyl alcohol (CP) and κ-carrageenan/polyvinyl alcohol (KP) film matrices. The joint effect of anthocyanins' source and polysaccharides' nature on the structure and functionality of the films was determined. Results showed PSA and PCA interacted with film matrices through hydrogen bonds and/or electrostatic interactions, resulting in improved film uniformity. PSA and PCA did not remarkably alter the water vapor permeability and tensile strength of the films; however, significantly improved the light barrier ability, antioxidant activity, pH-sensitivity and ammonia-sensitivity of films. For the films containing the same anthocyanins (PSA or PCA), LP-based films had relatively higher light barrier ability and storage stability, while CP-based had relatively weaker color changeable ability. When PSA and PCA were immobilized in the same film matrix, the films containing PCA had higher light barrier ability and antioxidant activity than the films containing PSA. Among the films, LP-PCA film exhibited a good potential to monitor the freshness of shrimp. Results suggested the structure and functionality of the films were influenced by the source of anthocyanins and the nature of polysaccharides.

A Comprehensive Review of the Development of Carbohydrate Macromolecules and Copper Oxide Nanocomposite Films in Food Nanopackaging

Background. Food nanopackaging helps maintain food quality against physical, chemical, and storage instability factors. Copper oxide nanoparticles (CuONPs) can improve biopolymers’ mechanical features and barrier properties. This will lead to antimicrobial and antioxidant activities in food packaging to extend the shelf life. Scope and Approach. Edible coatings based on carbohydrate biopolymers have improved the quality of packaging. Several studies have addressed the role of carbohydrate biopolymers and incorporated nanoparticles to enhance food packets’ quality as active nanopackaging. Combined with nanoparticles, these biopolymers create film coatings with an excellent barrier property against transmissions of gases such as O2 and CO2. Key Findings and Conclusions. This review describes the CuO-biopolymer composites, including chitosan, agar, cellulose, carboxymethylcellulose, cellulose nanowhiskers, carrageenan, alginate, starch, and polylactic acid, as food packaging films. Here, we reviewed different fabrication techniques of CuO biocomposites and the impact of CuONPs on the physical, mechanical, barrier, thermal stability, antioxidant, and antimicrobial properties of carbohydrate-based films.

Ixiolirion tataricum anthocyanins-loaded biocellulose label: Characterization and application for food freshness monitoring

A new intelligent pH-sensitive colorimetric label was fabricated by immobilizing Ixiolirion tataricum anthocyanins (ITA) into biocellulose (bacterial nanocellulose; BNC) film and was then studied to determine how it can be used as a label for monitoring freshness/spoilage of shrimp during storage at 4 °C. The formation of new interactions between ITA and BNC film and disruption of crystalline structure of BNC after anthocyanins immobilization were approved by FT-IR and XRD analyses, respectively. According to FE-SEM observations, the porosity of the BNC network decreased after ITA incorporation. The fabricated BNC-ITA label showed a distinct color change from violet to green over the pH range of 4-12. The pH, total volatile basic nitrogen (TVB-N), total psychrophiles count (TPC), and the quantity of biogenic amines (histamine, cadaverine, putrescine, and tyramine) in the shrimp samples and their correlation with color changes on the label were measured over a 4-day storage period. Consistent with changes in levels of TVB-N, TPC, pH, and biogenic amines, a visually distinguishable color change occurred on the BNC-ITA label as blue (fresh), dark green (medium fresh), and kelly green (spoiled). This research showed that ITA as a novel pH-sensitive dye is a promising candidate for developing pH labels for seafood intelligent packaging.

Antimicrobial and indicator properties of edible film containing clove bud oil-loaded chitosan capsules and red cabbage for fish preservation

For safe preservation and consumption of fish, freshness monitoring and antimicrobial control is crucial. Edible films comprising natural antimicrobial and spoilage indicator agents represent a convenient method for such preservation. Edible chitosan-based films were prepared using red cabbage (RC) and clove bud oil (CBO)-loaded chitosan/carrageenan capsules as spoilage indicator and antimicrobial agents, respectively. CBO-loaded capsules were prepared by the ionic gelation of chitosan and carrageenan. Films containing CBO capsules exhibited significantly higher antimicrobial activity than films containing non-encapsulated free CBO, as confirmed by minimum inhibitory concentration and time-kill assays. The highest antimicrobial activity was observed in the largest capsules (1.7 μm). After incubation for 48 h, the pH of fish peptone agar containing Pseudomonas fluorescens increased from approximately 6.0 to 9.0, and a color change from purple to deep blue was clearly observed during the growth of fish-spoiling bacteria. Thus, our results suggested that edible films containing CBO-loaded capsules and RC showed the potential to inhibit microbial growth in fish and to visibly indicate fish freshness.

A novel sensor based on bead-counting of purple sweet potato tapioca pearl for freshness monitoring of shrimp

A novel sensor based on bead-counting of purple sweet potato tapioca pearl for freshness monitoring of shrimp was proposed. The sensor was prepared from commercially available tapioca pearls with purple sweet potato as a natural colorant by using a similar procedure as to prepare "Thai Saku dessert". A novel concept of using five tapioca pearls stacked in a pipette tip was proposed to observe the color change of the pearls by bead counting approach. The color of the tapioca pearl changed from purple to greenish-blue upon the detection of volatile amines and then to green on prolonged exposure to volatile amines. This color change was observed from the first bead and gradually observed on the next beads according to the concept of distance-based colorimetric measurement. This work is the first to demonstrate the use of bead counting as a novel, low-cost sensor technology for estimating the freshness of shrimp.