Preparation of an intelligent pH film based on biodegradable polymers and roselle anthocyanins for monitoring pork freshness

Updated insights into steady-modified anthocyanin food packaging: Novel strategies, characterization, application and future challenges

Rising attentions on food safety and quality as well as disadvantages of conventional plastic food packaging motivates extensive study in anthocyanin-based food packaging. However, anthocyanins are susceptible to environmental conditions, resulting in easily-degradable properties of anthocyanin-based food packaging. Therefore, steady-modified anthocyanin-based food packaging are highly demanded for further deeper application. Based on this, thorough insights into steady-modified anthocyanin-based food packaging are provided in the current review. The degradation phenomenon and factors affecting stability of anthocyanin-based film during long-term storage were investigated. Novel steady-modification strategies to improve film stability were systemically summarized. Also, their effects on film physical (structure/mechanical/hydrophobic) properties and functional (pH-responsive, antioxidant and antibacterial) properties were explored. Meanwhile, application cases of steady-modified anthocyanin-based film regarding freshness monitoring and quality maintenance were comprehensively discussed. Finally, major challenges and future prospects were also proposed for further development.

Multifunctional chitosan-based indicator films containing composite pigments stabilized by extracellular and cell wall polysaccharides from Auricularia cornea var. Li. waste for visualization of salmon freshness

Smart packaging can indicate the meat freshness through color variations of natural pigments within the films, whose instability have hindered their industrial application. This study developed multifunctional indicator films (CS-ACPS-CB) that possessed ultraviolet resistance, antioxidant properties, and pH sensitivity by incorporating extracellular and cell wall polysaccharides from Auricularia cornea var. Li waste (ACPS) into chitosan (CS) matrix with curcumin/betalain as indicators. Results revealed the extracellular component was acidic heteropolysaccharides, while the cell wall comprised glucose, mannose, xylose, rhamnose and galactaric acid. The electrostatic interactions and hydrogen bonding between cell wall polysaccharides and CS strongly stabilized composite pigments, allowing for controlled release at pH above 8.0. Additionally, CS-ACPS-CB demonstrated color changes corresponding to increases in total volatile basic nitrogen values, effectively signaling the progressive spoilage of salmon. These findings offer an environmentally friendly solution for utilizing Auricularia cornea var. Li waste and a sustainable application for ACPS in smart packaging materials.

pH-responsive zein/chitosan composite film containing cinnamon essential oil-loaded Pickering emulsion and black wolfberry anthocyanin: Physicochemical properties, and application in packing salmon

With the rapid development of smart packaging, traditional systems that only extend shelf life or monitor freshness no longer meet consumer demands. This study developed a pH-responsive zein/chitosan composite film incorporating cinnamon essential oil-loaded Pickering emulsion (CEOP) and black wolfberry anthocyanins (BWAN) to extend salmon shelf life and monitor freshness. The composite films' structure, physical properties, pH sensitivity, antioxidant, and antimicrobial characteristics were evaluated. Incorporating 1 % CEOP enhanced the film's mechanical strength (from 11.44 MPa to 25.49 MPa), antioxidant capacity (from 61.9 % to 85.6 %), and antimicrobial effects. FTIR, XRD, and SEM confirmed strong molecular interactions between CEOP, BWAN, and the film matrix, improving stability. The composite film extended salmon's shelf life by 6 days and exhibited dynamic color changes, providing real-time freshness monitoring. This multifunctional film offers an innovative solution for food preservation with intuitive indicators of food quality.

Antioxidant pH-sensitive films incorporating CMC/SA/starch, anthocyanins, and tea polyphenols for monitoring freshness of pork

It is important to find an intelligent packaging which can monitor pork freshness immediately and extend its shelf life in food science. The aim of this study was developing a novel pH sensitive film with high antioxidant activity based on sodium carboxymethylcellulose (CMC), sodium alginate (SA), and cassava starch (CS) incorporating Lycium ruthenicum anthocyanins (LRA), and tea polyphenols (TP). The pH response, physical properties, color stability, antioxidant activity, and the ability to monitor the freshness of pork of the films were analyzed. The results indicated that LRA was sensitive in the solution of pH 1-14. After the addition of LRA and TP, the thickness of the films was increased, the mechanical properties were affected, and the water content, and WVP were decreased. LRA and TP significantly improved the light-resistance performance. Fourier transform infrared spectroscopy revealed that CMC, SA, and CS had good compatibility, and LRA and TP were successfully incorporated into the film. TP significantly increased the antioxidant activities of the film as determined by DPPH, and FRAP methods. In addition, the film showed remarkable color change in response to the increase of volatile basic nitrogen content in pork during spoilage. The films containing 0.2 % TP obviously inhibited lipid oxidation, and extended the shelf life of pork. Our findings suggested that CSC/LRA/TP films could be applied as antioxidant materials with freshness monitor effect for pork packaging. This research provides an alternative for the visual intelligent packaging of pork.

Characterization, grass carp (Ctenopharyngodon idella) freshness monitoring and preservation effects of active films incorporated with Solanum nigrum L. anthocyanins

This study investigated the characterization, grass carp freshness monitoring and preservation effects of active films containing Solanum nigrum L. anthocyanins (SNA). Compared to the composition of SNA, the amounts of cyanidin, delphinidin, malvidin and rutin in the SNA composite film decreased, while those of quercetin, isorhamnetin and kaempferol increased. SNA was effectively integrated into the polyvinyl alcohol /fish gelatin (PVA/FG) film via hydrogen bonding but reduced the film's structure integrity and thermal stability. Interestingly, 0.2 % SNA improved the mechanical properties of the PVA/FG film, enhancing its responsiveness to pH fluctuations and NH3 environments. Whereas, PVA/FG-0.3 %SNA and PVA/FG-0.4 %SNA films exhibited stronger antioxidant capability and higher active compounds migration efficiency. The PVA/FG-0.2 %SNA film monitored grass carp freshness by transforming from pink to light pink, eventually becoming colorless. Meanwhile, the PVA/FG-0.3 %SNA film significantly inhibited increases in pH, total viable count, thiobarbituric acid reactive substance, and total volatile base nitrogen levels in grass carp.

High loading of anthocyanin on chitosan films by acrolein for sensitive monitoring of meat freshness

As a natural pigment, anthocyanins show different colours in a wide pH range and can be used to prepare pH-responsive smart packaging films. However, free anthocyanins have obvious disadvantages, including easy degradation under light and easy migration into foods. This study used acrolein (ACR), a highly reactive β-unsaturated aldehyde, to cross-link anthocyanin and chitosan (CS). This technique enabled loading of up to 26.18 mg/g of anthocyanin on CS, increasing the stability and preventing migration. Furthermore, acrolein substantially enhanced the mechanical strength of the film while reducing its swelling ability, water-vapour transmission and water contact angle. The film exhibited a broad range of colour shifts across pH levels ranging from 2 to 13. In ammonia simulation experiments, the film demonstrated exceptional sensitivity and quick response to volatile ammonia, exhibiting a 48.5 % colour change within 1 min. Pork freshness test also showed that when the total volatile basic nitrogen content is below 15 mg/100 g (indicating meat deterioration), the film undergoes a substantial colour change (SRGB > 40 %). Concurrently, the cross-linked anthocyanins improved the antioxidant and antibacterial activities of the membrane. Therefore, it can be concluded that the CSAP-2 film can detect pork freshness and has great application prospects in the field of smart meat packaging films.

Intelligent double-layer pads containing blueberry anthocyanins/citric acid/tricolor lake for chilled pork real-time freshness monitoring

In this paper, an intelligent pH-sensitive pad was well designed using blueberry anthocyanin (BA) mixed with citric acid (CA) and yellow lake (Y), as composite indicator with significant color change (ΔE) from pink to yellow to green at pH 6.0-7.0 under tricolor principle. The double-layer poly(vinyl alcohol)/glycerol/gelatin (PGG)-CA/PGG-CA-BA-Y pad exhibited an excellent colorimetric pH/NH3-response, water-absorption ability, mechanical properties and preservation performance. Applied into the freshness monitor of chilled pork, the pad color change was detected from red (fresh) to orange (semi-fresh) and then to green (spoiled) by both naked eye visually and mobile APP rapidly, as the correlation coefficients (R2) of ΔE and SRGB significantly correlated with pH (0.99 and 0.98) and TVB-N (0.96 and 0.96), respectively. In summary, intelligent pH-sensitive double-layer hydrogel pads could preciously monitor food freshness and prevent the spoilage, by improving anthocyanin stability and increase the sensitivity of color in response to a narrow pH range.

Fast response and stable dyed cellulose nanofibrous films for shrimp spoilage detection

In this study, the electrospun cellulose acetate (CA) nanofibrous films were hydrolyzed and then dyed with a synthetic dye of 1-hydroxy-4-[4-(ethylsulfurate sulfonyl)-phenylazo]-naphthalene (HESPN). The physicochemical properties of the dyed films were similar to the unmodified films. Due to the covalent bonds formed between dye and cellulose molecules, the dyed films showed high stability with almost no dye leakage in acidic solutions and minimal leakage (0.4 %) in alkaline solutions. In addition, the dyed films exhibited rapid responsiveness to ammonia gas and could transit from yellow to brown within 20 s due to the nanofibrous structure of the films and quick color change of the dye. The dyed films can be used to monitor the spoilage of shrimp with a color change from yellow to brown. The nanofibrous cellulose films dyed with HESPN can be potentially applied as indicators to be used in smart packaging.

Designing the pH-sensitive indicator based on starch nanoparticle with bromocresol green for monitoring meat spoilage

The starch nanoparticle, combined with bromocresol green (BCG), served as a pH-sensitive indicator to monitor meat quality throughout an 8-day refrigerated storage period. The meat samples were sealed in package which the pH-sensitive indicator attached to the interior part of packaging lid. The changes in meat quality were evaluated by total volatile base nitrogen (TVBN), pH, total viable count (TVC), sensory analysis, and color in interval of 0, 3, 5, 7, and 8-days storage at 4°C. Initial TVBN values were recorded at 19.6 mg/100 g, increased to 26.6 mg/100 g by the end of storage period. The pH value was significantly increased after 8 days storage at 4°C. The observed color variation in the indicator from yellow to blue was attributed to the concurrent increases in TVBN, TVC, and pH. The indicator color changes had significant correlation with analyzed chemical quality of stored meat. Therefore, the designed BCG pH-sensitive indicator could be effective in monitoring the meat spoilage during storage.

Smart bacteria cellulose facial mask for sensing and recovering skin pH

The utilization of skin care products and cleansers is a prevalent method for maintaining facial skin health. However, excessive use of these products is an unnoticed factor that can result in serious skin problems. Currently, there are no products on the market to provide users with skin acclimatization and restoration services. Herein, we introduce a facial mask with a smart pH sensor to monitor and repair facial skin. Specifically, bacterial cellulose fragments were mechanically dispersed, co-mingled with carboxymethyl cellulose and hydroxypropyltrimethylammonium chloride chitosan, with anthocyanin added as a pH-indicating reagent. The composite mask was then prepared by hot air drying. This mask exhibited notable anti-hornification effect, robust water absorption, water retention, wet strength, and antibacterial and antioxidant properties, making it suitable for a high-end facial mass base material with an excellent pH sensitivity within the range of 2.0-12.0, which could be observed directly through colorimetry with the naked eye.

Preparation of edible films from pectin/carboxymethyl chitosan incorporating polyphenol-rich roselle leaf extracts for food packaging applications

This study aimed to design an innovative antioxidant and antibacterial film for functional and health-promoting food packaging materials using food-grade polysaccharides incorporated with polyphenol-rich roselle leaf extracts (RLE). The films were fabricated using the casting method of pectin (P), carboxymethyl chitosan (CMC), and RLE. Six sets of films; 3 control films such as pectin (P-0), carboxymethyl chitosan (CMC-0), pectin plus carboxymethyl chitosan (PCMC-0), and 3 treated films such as pectin (PR-3), carboxymethyl chitosan (CMCR-3), (PCMCR-3) with 3 % RLE were prepared respectively to study the effects of RLE on the properties and function of prepared films. The water vapor permeability of the films ranged from 4.16 ± 0.04 g mm/h·m2·kPa to 6.93 ± 0.07 g mm/h·m2·kPa, with RLE-incorporated samples exhibiting lower permeability than the control sample. The maximum tensile strength (53.00 ± 1.07 MPa) and elongation of break (85.83 ± 2.81 %) were observed at PCMCR-3 containing 3 % RLE. The highest water contact angle (109.4 ± 0.16) was also noted in the PCMCR-3 film. The incorporation of RLE decreased the roughness of the film microstructure. The addition of RLE film CMC-R and PCMCR-3 notably enhanced the antibacterial and antioxidant properties of the edible film. Overall, the PCMCR-3 films extended the shelf life of fresh fish preserved at 4 ± 1 °C, offering promising innovative food preservation packaging materials for preserving perishable food products.

Curcumin: A Magical Small Molecule with a Large Role in Active-Intelligent Degradable Food Packaging

Curcumin exhibits antioxidant, antibacterial, antitumor, and anti-inflammatory biological properties. Its dual functionality as both a food additive and a pH-sensitive colorant has led to extensive applications in meat products and other food systems, thereby garnering significant research interest. In recent years, curcumin-loaded active-intelligent food packaging films have emerged as a promising innovation due to their multifunctional capabilities: not only do they prevent microbial contamination and extend food shelf life, but they also enable real-time freshness monitoring through visual colorimetric responses. This paper first delineates the molecular structure and fundamental biological mechanisms of curcumin. Subsequently, it systematically reviews the strategies for curcumin incorporation (including encapsulation techniques and composite formulations) and advanced fabrication methodologies for developing active-intelligent biodegradable films. Finally, the current applications of curcumin in polymer-based smart packaging systems are critically analyzed, with prospective research directions proposed to address existing technological limitations.

Colorimetric films of carboxymethyl cellulose and sodium alginate incorporating Spirulina extract (phycobiliproteins) and gallic acid for real-time shrimp freshness monitoring

This study developed edible colorimetric films by incorporating 1 % ultrasonic-assisted aqueous extract of Spirulina platensis (UAAESP; 76.83 % protein), and 0.125-0.250 % gallic acid (GA) into 2 % carboxymethyl cellulose (CMC) and sodium alginate (SA) matrices. The films were evaluated for structural, optical, mechanical, antimicrobial, antioxidant, and calorimetric properties. UAAESP exhibited a blue-grey colour at pH 3-9 and yellowish-green at pH 10, reflecting higher UV-visible absorption. The addition of 1 % UAAESP and 0.25 % GA reduced moisture content (7.73 %), water solubility (12.06 %), and water vapor and oxygen permeability, while increasing film thickness (10.97 %) and tensile strength (38.53 %). Film opacity increased due to the blue colour of UAAESP. SEM showed homogeneous surfaces, with minor cracks in cross-sections, while FTIR confirmed strong physical interactions between CMC, SA, UAAESP, and GA. Antioxidant activity improved with UAAESP and higher GA levels, while 0.25 % GA expanded inhibition zones by 74.25 % and 81.09 % against S. aureus and E. coli. The GA not only improve the antioxidant and antimicrobial activities but also sensitize the UAAESP incorporated in the matrices to better sense the spoilage levels. The films' colour changes (blue, bluish-grey, dark grey) corresponded shrimp spoilage levels. Thus, UAAESP-GA films offer real-time freshness indicators and sustainable, recyclable alternatives to plastic packaging.

The fabrication and intelligent evaluation for meat freshness of colorimetric hydrogels using zein and sodium alginate loading anthocyanin and curcumin: Stability and sensitivity to pH and volatile amines

Intelligent packaging designed to detect food spoilage is receiving increasing attention, and pH-sensitive colorimetric hydrogels show great potential for monitoring food spoilage. The pH-sensitive colorimetric hydrogels incorporating dual indicators of anthocyanin (BA) and curcumin (CUR) were fabricated via the interactions of zein and sodium alginate (SA) to assess meat freshness. The effects of the addition ratios of BA and CUR on zein/sodium alginate hydrogels were characterized by morphological observation, structural analysis and cumulative release profiles, and the sensitivity of the colorimetric hydrogels was also evaluated. The zein/sodium alginate hydrogel (zein/SA/Mix2), which incorporated the mixture of BA and CUR at a ratio of 70:1, exhibited the smallest particle size (1152.67 nm) and displayed a more homogeneous and dense gel structure compared with other treatments. FTIR and XRD results indicated that the interactions between sodium alginate and zein were primarily governed by hydrogen bonds and electrostatic forces, and the zein/SA/Mix2 hydrogel exhibited the weakest peak intensity at 3422 cm-1 and at 2θ = 28.25°, indicating the highest degree of crosslinking among these treatments. The zein/SA/Mix2 hydrogel rapidly responded to volatile amines within 2 min, and the release rates of BA and CUR remained below 26 % and 5 % in 95 % ethanol solution within 96 h, respectively, indicating its high stability and sensitivity. During the storage of air-dried goose meat and chilled chicken meat, the zein/SA/Mix2 hydrogel transitioned from yellow to green, and finally to dark brown, effectively distinguishing meat freshness, which was further confirmed by partial least squares regression analysis.

Rhododendron arboreum Sm. anthocyanin-infused starch, chitosan, and polyvinyl alcohol based composite films: Comparative analysis of physical, UV barrier, antioxidant and intelligent behavior

Rhododendron arboreum Sm. is found abundantly in the Himalayan region of Nepal and other Asian countries, and anthocyanins extracted from its flower were utilized to develop intelligent food packaging films. The films were synthesized by blending chitosan (CS) with starch (ST), CS with polyvinyl alcohol (PVA), and ST with PVA, incorporating anthocyanin from R. arboreum. A comparative analysis was conducted to evaluate their potential applications in food packaging. Analytical techniques like FESEM, IR spectroscopy, XRD, and TGA confirmed strong interactions between the polymer matrix and anthocyanins through hydrogen bonding and electrostatic attraction. All samples containing anthocyanins exhibited effective UV light barrier properties, with the PVA/ST/ACNs films showing UV blocking up to 450 nm and exhibiting superior antioxidant properties. The pH sensing ability, antioxidant properties, and ammonia sensitivity depend both on anthocyanin and the composition of the polymer matrix. Ammonia sensitivity was highest for PVA/ST/ACNs (70.1 %), followed by PVA/CS/ACNs (47.8 %) and CS/ST/ACNs (5.6 %). Chicken meat packaged with PVA/ST/ACNs films for 48 h showed TVB-N at 46.39 mg/100 g, pH 8.6, and film color changed from reddish pink to greenish-yellow, signifying spoilage. These findings suggest potential for the film as intelligent packaging to monitor meat freshness, correlating TVB-N, pH, and film color.

Preparation and characterization of chitosan / corn starch based films loaded with Vaccinium vitis-idaea anthocyanin nanocomplexes and the application in shrimp preservation

In this experiment, the nanocomposite film prepared by adding of nanocomplexes (ACNs-CHC/CMC-WPI) of Vaccinium vitis-idaea anthocyanins encapsulated with carboxymethyl chitosan (CMC), chitosan hydrochloride (CHC), and whey protein isolate (WPI) to chitosan/corn starch (CTS/Corn) blend matrix for food packaging. The functionality and stability of anthocyanin-loaded nanocomplexes and anthocyanin-containing films were determined and compared. Good encapsulation was observed by transmission electron microscopy. The freshness preservation effect of the prepared films on shrimp was investigated. Scanning electron microscopy results showed that ACNs-CHC/CMC-WPI was uniformly dispersed in chitosan-corn starch matrix, indicating the formation of a stable CTS/Corn-anthocyanin nanocomplex film (CTS/Corn-AN film). Although CTS/Corn-free anthocyanin (CTS/Corn-FA film) had better antioxidant activity in the short term, the CTS/Corn-AN film could better maintain the antioxidant activity and original color after 28 days of light exposure. In summary, the CTS/Corn-AN film possessed better mechanical property with elongation at break at 88.67 %, oxidation resistance with DPPH scavenging of 28.71 % at 28th, and other physicochemical properties than those of the CTS/Corn-FA film. Finally, the CTS/Corn-AN film showed effective freshness preservation of shrimp at 4 °C for 10 days compared to the control group due to durable antibacterial and antioxidant properties. Therefore, CTS/Corn-AN film was promising active packaging material in shrimp preservation.

pH-responsive composite konjac glucomannan/xanthan gum film incorporated lysozyme fibril for the monitoring of chicken breast freshness

A pH responsive composite film was developed by incorporating cyanidin (CY) and egg white lysozyme fibril into konjac glucomannan (KGM) and xanthan gum (XG) matrix to monitor the chicken breast freshness in this work. The physicochemical properties of the films, especially pH sensitivity, evaluated by color difference and visual color change under different pH values, were first explored. The freshness changes of chicken breast sealed with the composite films were also analyzed. Hydrogen bonding and electrostatic interaction formed between the components of the composite film. Moreover, the characterizations of pH responsiveness, thermal stability, and barrier property indicated the benefits of incorporating CY and lysozyme fibril into KGM/XG films. The KGM/XG/lysozyme fibril/CY (KXLCY) film showed superior biodegradability in soil. KXLCY composite film reduced the weight loss and delayed the spoilage and fat oxidation rate of chicken breast. In addition, the color of KXLCY film changed from purple red to purple and then to blue during the storage of the packaged chicken breast, indicating a real-time freshness monitoring effect. This work provided a solid scientific foundation for the development of active pH intelligent colorimetric films and their application in food freshness evaluation.

Açaí powder-enriched biodegradable starch films: Characterization, release in food simulants and protective effect in photodegradation system

Açaí is an important source of natural pigments with antioxidant capacity, such as anthocyanins. Among the various possibilities for its application is its incorporation into biodegradable films, which can act as carriers of these bioactive compounds. The objective of this study was to develop biodegradable films based on starch with different açaí powder concentrations (5 % and 15 %). The films were developed using the casting technique and evaluated in relation to barrier properties, physicochemical, biodegradability, release to food simulants, and protective effect against photodegradation of β-carotene. The addition of the natural antioxidant led to the development of films with greater color intensity and improved light barrier and mechanical properties (tensile strength and elongation). The retention of açaí powder in the polymer matrix was identified in the FTIR analysis through the intensification of some regions in relation to the control film. The cohesion and interaction between film:active compound showed an improvement in water-related properties, such as reduced permeability and water absorption. Furthermore, the active films showed sustained release of anthocyanins into the food simulant (maximum of 3.04 mg cyanidin 3-glycoside/100 g and 8.06 mg cyanidin 3-glycoside/100 g for films AP5% and AP15%, respectively) and better protection against photodegradation of the β-carotene solution (35-50 % retention when exposed to high light intensity). The rapid biodegradability, thermal stability, and stability at different pH may indicate potential application as packaging for foods susceptible to photodegradation.

Emerging chitosan systems incorporated with polyphenols: Their applications in intelligent packaging, active packaging, and nutraceutical systems - A comprehensive review

Chitosan, a biodegradable anionic polysaccharide, has been increasingly investigated for food packaging and nutraceutical applications. In recent years, chitosan has been combined with polyphenols, a group of health promoting bioactive compounds, to enhance their physicochemical, functional, and biological properties. The synergistic functional attributes of chitosan and polyphenols have led to the development of several novel food packaging materials and nutraceuticals. Despite, several investigations being conducted on chitosan-polyphenol materials (e.g., films, coating, nanoparticles, complexes, emulsion gels), currently there is a lack of studies that comprehensively evaluate the combined effect of chitosan and polyphenol in development of both food packaging materials and nutraceuticals. Therefore, in this review, novel packaging materials and nutraceuticals developed employing chitosan-polyphenol in recent years (2018-2024) are thoroughly investigated. This review initiates with the source, production strategies, and techniques employed to improve the functionality of chitosan. Secondly, the findings associated with important intelligent packaging materials, including pH indicator, time-temperature indicator, and freshness indicator, developed using chitosan-polyphenol is investigated. Following that, the applications of chitosan-polyphenol materials in active food packaging (i.e., antimicrobial, antioxidant, oxygen scavenger, ethylene scavenger, and moisture scavenger) are explored. Notably, chitosan-based delivery systems that are employed to improve the chemical stability, bioaccessibility, and biological properties of polyphenols for nutraceutical applications are summarized. Finally, the challenges associated with the industrial application of chitosan-polyphenol materials are addressed. Overall, this review would benefit a wide range of scientists from food packaging to ingredient sectors by providing the current knowledge associated with chitosan-polyphenol materials.

Review of Recent Advances in Intelligent and Antibacterial Packaging for Meat Quality and Safety

Intelligent and antimicrobial packaging technologies are transforming meat preservation by enhancing food safety, enabling real-time quality monitoring, and extending shelf life. This review critically examines advancements in intelligent systems, including radio frequency identification (RFID), gas sensors, time-temperature indicators (TTIs), and colorimetric indicators for continuous freshness assessment. A key focus is natural compound-based chromogenic indicators, which establish visual spoilage detection via distinct color transitions. Concurrently, antimicrobial systems integrating inorganic compounds, organic bioactive agents, and natural antimicrobials effectively inhibit microbial growth. Strategic incorporation of these agents into polymeric matrices enhances meat safety, supported by standardized evaluation protocols for regulatory compliance and quality assurance. Future research should prioritize optimizing sensitivity, cost-efficiency, and sustainability, alongside developing biodegradable materials to balance food safety with reduced environmental impact, advancing sustainable food supply chains.

Smart pH-sensitive indicators based on rice starch/pectin/alginate loading Lambrusco pomace extract and curcumin to track the freshness of pink shrimps

This research is focused on the formulation and testing of green visual pH-sensitive indicators based on natural extracts from Curcuma Longa (CUR) and Lambrusco wine pomace (LAM), an Italian wine variety, incorporated into rice starch/pectin/alginate matrixes for non-destructively detecting shrimps freshness in real-time. The effect of the mixed indicators and their synergic combination on the properties and performances of indicators was investigated. Both the extracts and their combination showed pronounced pH responsiveness. Films were widely characterized in terms of morphological, barrier, spectroscopic, thermal and mechanical properties. The presence of extracts slightly reduced the transparency of the films while the film with both the extracts exhibited the highest Young's modulus (14.17 MPa), lowest moisture content (27.67 %) and a WVP value (0.79 g m m-2 s-1 Pa-1) intermediate between the Lambrusco extract loaded film and the curcumin based one. Moreover, the pH-sensitive systems showed a noticeable antioxidant activity (96 % for LAM/CUR film) and enhanced antibacterial activity toward E. coli and S. aureus compared to pristine films. Besides, the mixed indicator-based film showed high sensitivity to ammonia (68 %) determining an ΔE value easily detectable by the human eye. Finally, the films were applied as cheap visual indicators for monitoring the freshness of packaged fresh shrimps over time stored at T = 4 °C and T = 25 °C through the colourimetric variation induced by pH changes. The TVB-N value, which was correlated to the microbial count for shrimps over time, reached the rejection limit at 33 h for T = 25 °C and 54 h for T = 4 °C. The colour changes were recorded simultaneously and the turning to deeper colours indicated the decomposition of proteins to organic amines and the spoilage of food. Results show that the produced films provide easily detectable colour changes during food spoilage proving that, being fabricated from natural sources, they represent novel and sustainable tools for multi-purpose intelligent food packaging applications.

Development and evaluation of pH-sensitive Euryale ferox starch-based films containing nano-SiO2 and Chinese rose (Rosa chinensis) extract for freshness monitoring of chicken breast meat

In this study, smart films of EFS, EFS-SiO2 and EFS-SiO2-CRE were successfully developed by using Euryale ferox starch (EFS), nano-SiO2 and Chinese rose extract (CRE). The Chinese rose flower had a high content of anthocyanins (1.73 mg/g) and CRE exhibited different colors in varying pH buffers (2-13). The addition of nano-SiO2 decreased tensile strength (TS) (41.08 to 16.75 MPa) and elongation at break (EAB) (6.71 to 2.69 %) of the EFS film. Incorporation with CRE could significantly increase water vapor permeability (4.47 to 5.35 10-11 g m-1 s-1 Pa-1), TS (16.75 to 26.19 MPa) and EAB (2.69 to 4.62 %) of the EFS-SiO2 film. Incorporation of nano-SiO2 and CRE significantly enhanced the thermal stability and light barrier performance of the EFS film. The EFS-SiO2-CRE films showed excellent pH and ammonia sensitivities with different colors varying from red to blue. The EFS-SiO2-CRE-III film displayed strong antioxidant activity with a maximum DPPH scavenging rate of 96.54 ± 0.44 %. When employed for monitoring freshness of chicken breast meat, the EFS-SiO2-CRE-III film showed the most significant visible color changes at 24 h when the TVB-N content was 21.7 mg/100 g. Findings supported the application of this strategy in fabrication of the EFS-SiO2-CRE-III film for smart packaging.

Strong, tough, antibacterial, antioxidant, biodegradable multi-functional intelligent hydrogel film for real-time detection and maintenance of salmon freshness

In this study, we prepared a new multi-functional intelligent hydrogel preservation film using soy hull nanocellulose (SHNC), polyvinyl alcohol (PVA), chitosan (CS), and anthocyanin (Anth) as raw materials. The physicochemicals of the hydrogel preservation film, and its role in monitoring the freshness and freshness of salmon was evaluated. The results showed that the monomers were crosslinked by hydrogen, ester bonds, and electrostatic interactions in the hydrogel film, and there were three-dimensional pores in the hydrogel film. Meanwhile, SHNC/PVA/CS/Anth-3 exhibited excellent mechanical properties (elongation: 345.26 %; tensile strength: 26.84 MPa; compressive strength: 139.27 MPa) and excellent biodegradation performance. Additionally, the hydrogel film displayed excellent antioxidant and antibacterial properties (90.59 %). The preservation experiment showed that, at 4 °C, the hydrogel film could not only inhibit the growth and reproduction of bacteria on the surface of salmon meat, but it could also detect the freshness of salmon meat in real time, Meanwhile, the film could extend the shelf life of salmon meat from 6 d to 14 d. This study provides a new perspective for constructing a multi-functional intelligent hydrogel preservation film.

Advances in 3D and 4D Printing of Gel-Based Foods: Mechanisms, Applications, and Future Directions

This review examines recent advancements in gel-based 3D and 4D food-printing technologies, with a focus on their applications in personalized nutrition and functional foods. It emphasizes the critical role of tunable rheological and mechanical properties in gels such as starch, protein, and Pickering emulsions, which are essential for successful printing. The review further explores 4D food printing, highlighting stimuli-responsive mechanisms, including color changes and deformation induced by external factors like temperature and pH. These innovations enhance both the sensory and functional properties of printed foods, advancing opportunities for personalization. Key findings from recent studies are presented, demonstrating the potential of various gels to address dietary challenges, such as dysphagia, and to enable precise nutritional customization. The review integrates cutting-edge research, identifies emerging trends and challenges, and underscores the pivotal role of gel-based materials in producing high-quality 3D-printed foods. Additionally, it highlights the potential of Pickering emulsions and lipid gels for expanding functionality and structural diversity. Overall, this work provides a comprehensive foundation for advancing future research and practical applications in gel-based 3D and 4D food printing.

Waterborne polyurethane with curcumin moieties for rapid responsive warnings and emergency antimicrobial action: Application in crab freshness preservation

The ideal smart food-packaging film exhibits responsive color warnings and antimicrobial properties when food metamorphism starts. However, in practical applications, these film responses are slow, usually taking several days, which is not conducive to effective antimicrobial effects. In this study, natural plant-derived curcumin was introduced into waterborne polyurethane (WPU) dispersions through two modes: free-state and end-capping. During the film-forming process, under the influence of surface tension, the capped-end curcumin migrated to the surface and further immobilized free curcumin through π-π interactions. Consequently, curcumin accumulated on the film surface, preventing flipping in moist or hydrophobic environments, in addition to acting as a color indicator for the rapid detection of crab spoilage, thus generating ammonia for a real-time response (of approximately 60 s). Simultaneously, the curcumin degraded, producing water-soluble antimicrobial curcumin-degradation products. This study significantly advances the practical application of curcumin in smart food packaging.

Effects of different white nanomaterials on pH response ability and physicochemical performance of anthocyanin-loaded carboxymethyl cellulose-polyvinyl alcohol films

The anthocyanin-loaded films based on natural polymers as pH-responsive indicator are widely applied in the food preservation. However, the low mechanical strength and storage stability limited their practical application, there is an urgent demand to improve the performance of anthocyanin-loaded films. In order to avoid affecting the color indication of anthocyanins, we explored the effect of eight kinds of white nanomaterials on improving the performance of films. The results revealed that some nanomaterials showed capability in improving the polymer molecular interactions and enhancement in mechanical properties, barrier ability, and antioxidant activity. However, nanomaterials containing Zn was not suitable for anthocyanin-loaded film modification, because it could destroy the pH responsiveness of anthocyanin. The nano Al2O3 could increase the sensitivity of anthocyanin-loaded film in pH-response, which achieved the highest performance score during pork storage. This investigation will provide theoretical support for the development of more optimized pH-responsive anthocyanin-loaded films in the future.

Recent advances in chitosan-based active and intelligent packaging films incorporated with flavonoids

Biopolymer-based films are promising packaging materials to maintain food quality, reduce food waste and ensure food safety. Chitosan, a biopolymer with excellent film-forming ability, can act as the carrier for plant-derived bioactive compounds. In the past decade, several studies have reported chitosan-based films incorporated with different classes of flavonoids, including flavones, flavanones, isoflavones, flavonols, flavanols and anthocyanidins. These films, based on their functionality, can be divided into chitosan/flavonoid active packaging films and chitosan/anthocyanin (the glycosylated anthocyanidin) intelligent packaging films. This paper presents a comprehensive review on active and intelligent packaging films prepared from chitosan and different classes of flavonoids, with special attention being paid to the preparation, physical and functional properties, stabilization, and application of the films. Factors affecting the physical and functional properties of the films are summarized. In addition, the challenges for the commercial production and application of the films in active and intelligent packaging fields are discussed.

Recent advances in research on biomass-based food packaging film materials

Although traditional petroleum-based packaging materials pose environmental problems, biodegradable packaging materials have attracted extensive attention from research and industry for their environmentally friendly properties. Bio-based films, as an alternative to petroleum-based packaging films, demonstrate their significant advantages in terms of environmental friendliness and resource sustainability. This paper provides an insight into the development of biomass food packaging films such as cellulose, starch, chitosan, and gelatine, including their properties, methods of preparation (e.g., solution casting, extrusion blow molding, layer-by-layer assembly, and electrostatic spinning), and applications in food packaging. Through these preparation methods, the paper analyzes how the properties of the films can be effectively tuned and optimized to meet specific packaging needs. It was found that biomass film materials for food packaging not only possess functional properties such as antimicrobial, preservation, and indication, but also that their continued material innovation and technological improvements offer promising prospects for their use in commercial applications. These advances could help advance the global sustainable development goals, while showing great potential for improving food safety and extending shelf life. Future research will further explore new functions and applications of biomass films, providing additional solutions for environmental protection and sustainability.

Preparation of vanillin nanoparticle/polyvinyl alcohol/chitosan film and its application in preservation of large yellow croaker

The novel polyvinyl alcohol/chitosan films incorporated with vanillin/zein/κ-carrageenan nanoparticles (VZCNPs) were developed. The polyvinyl alcohol/chitosan/vanillin nanoparticles (PVA/CS/NPs) films had exhibited enhanced tensile strength, hydrophobicity, antioxidant activities and antimicrobial efficacy, all of which varied with the different concentrations of VZCNPs. Notably, the PVA/CS/NPs-10 film exhibited exceptional performance, with a reduced Moisture Content of 15.68 ± 0.46 %, an increased water contact angle of 65.75°, and improved ABTS scavenging rate of 77.39 ± 0.54 %, demonstrating outstanding antioxidant activity and antimicrobial properties. The PVA/CS/NPs films were further applied to the packaging of large yellow croaker (Pseudosciaena crocea) to evaluate their preservation capability at 4 °C. The results indicated that the PVA/CS/NPs films effectively inhibited microbial growth and lipid oxidation, thereby delaying the spoilage of large yellow croaker. High-throughput sequencing study showed that the films effectively inhibited spoilage bacteria, including Comamonas, Pseudomonas, and, Burkholderia and affected the distribution of bacterial populations during storage. This study provides new insights into prolonging the shelf life of fresh-frozen large yellow croaker and developing advanced preservation methods for the future development of the aquatic product.

A novel carboxymethyl cellulose/gum xanthan and citric acid-based film that enhances the precision of blackcurrant anthocyanin-induced color detection for beef spoilage tracking

Leveraging blackcurrant anthocyanin (BC) as an indicator and carboxymethyl cellulose (CMC), gum xanthan (GX), and citric acid (CA) as film fabricating materials, an innovative amine-responsive beef freshness intelligent film, known as CGC-BC, was successfully created. It was found that the physical characteristics, sensitivity to the biogenic amine reaction, and original color of the film were all highly influenced by the pH of the film-forming solutions. The film's freshness monitoring ability was assessed at 4, 25, and 35 °C, and various color changes were employed to monitor beef deterioration. ΔE values and the visual color difference of the low-concentration (SCG-BC-0.08 and SCG-BC-0.16) ammonia-sensitive indicator films demonstrated significant color changes than the high-concentration (SCG-BC-0.24 and SCG-BC-0.32) films. The films biodegradation (37.16 to 51.49%) ability was enhanced with increase in the proportions of BC. As the TVB-N and pH values of beef increased with the different temperatures and time and different color changes were observed from red to pink, black to brown, and yellow.

Pectin/zinc alginate films containing anthocyanins from dragon fruit peel as intelligent pH indicators for shrimp freshness monitor

The novel incorporation of dragon fruit peel extract (DE), rich in anthocyanins, Zn2+ (from Zinc Alginate) and pectin was applied to create active and intelligent food packaging composite films. These films were characterized for their microstructure and properties. Various levels of anthocyanin extracts (1 %, 3 %, and 5 %) were evaluated for their impact on the films' physical and functional properties, incorporating microstructure, mechanical strength, barrier properties, pH sensitivity, and bacteriostatic effectiveness. The films exhibited a significant antibacterial rate of up to 99.99 % against common foodborne pathogens, enhanced flame retardancy with an enhancement of 32.7 %, and a broad pH sensitivity range, indicating their adaptability to various conditions. The results demonstrated that the prepared indicator film achieved a 50 % reduction in water vapor permeability. Additionally, the mechanical properties were enhanced, with only a slight decrease of 12.2 % in tensile strength and 14.0 % in elongation at break. In tests monitoring shrimp freshness, pectin/ZA/DE films showed notable color changes correlating with shrimp quality. These specific values highlight the pectin/ZA/DE films' potential for real-world applications, suggesting that they have potential applications as smart packaging materials in the food industry.

Preparation of Physalis alkekengi L. calyx total flavonoids-chitosan composite film and its effect on preservation of chilled beef

In the present study, Physalis alkekengi L. calyx total flavonoids (PCTF) were extracted using the ultrasound-assisted ethanol method and separated and purified using macroporous resin AB-8. Physalis alkekengi L. calyx total flavonoid-chitosan (PCTF-CS) composite films containing 0.05 %, 0.10 % and 0.15 % PCTF were prepared using the purified PCTF laminated with chitosan (CS) and compared with single CS films, respectively, to investigate their mechanical properties, barrier properties, optical properties, microstructure, crystallography, thermal stability, water contact angle, particle size and zeta potential, antioxidant property, antimicrobial property, and preservation effect on chilled beef. The PCTF-CS films with PCTF additions had darker colors and higher mechanical and barrier properties than the CS films. In addition, the addition of PCTF improved the antioxidant and antimicrobial properties of the CS films. It enhances the freshness retention of fresh beef, and effectively inhibits the rise of weight loss, pH, total bacteria, total volatile basic nitrogen, and thiobarbituric acid reactive substances in beef, prolonging the shelf life of beef. These results indicate that the addition of PCTF can provide CS films with superior functional properties and bioactivities and that PCTF-CS composite films are a potential and promising packaging material for food preservation.

Fabricating a high-loading smart film to monitor pork freshness via adsorption of anthocyanins on simultaneously etched, anionized and bleached wood cell wall

In this paper, wood cell walls were simultaneously roughened, carboxylated, and bleached via NaOH/H2O2 treatment and roughened-poplar film (RPF) was obtained. Compared with the untreated film, the carboxyl group content increased 8 times to 1.92 mmol/g, and the pore growth rate reached 11.24%. Afterwards, a pH-indicator wood film (CTA-RPF) was prepared by self-adsorption of anthocyanins on RPF. It rapidly changed from purple to green within 7 s in 0.25 mL of ammonia at 53% RH and the initial color could restore in the air. When anthocyanins adsorption capacity reached 1.95 mg/g, only 0.36 cm2 of the film could accurately indicate the quality change of 300 g pork. Currently, CTA-RPF is the smallest smart film that can track the maximum mass of pork after comparing with other researches, therefore, promising to be used as a smart indicator label to track the freshness of pork in real market circulation.

Antimicrobial activities of natural flavonoids against foodborne pathogens and their application in food industry

The application of natural alternatives as food preservatives has gained much attention due to the escalating negative perception of synthetic preservatives among consumers and the spread of drug-resistance foodborne pathogens. Natural flavonoids have the potential to be employed for food safety due to their antimicrobial properties against a wide range of foodborne pathogenic microorganisms. In this perspective, we reviewed the antimicrobial activities of natural flavonoids, the mechanism of action, as well as their application for food safety and quality. Various strategies for the incorporation of flavonoids into food products were highlighted, including direct addition to food formulations, encapsulation as micro or nanocarriers, and incorporation into edible or active films and coatings. Furthermore, we discussed the current challenges of industrial application of flavonoids, and proposed future trends to enhance their potential as natural preservatives. This review provides a theoretical foundation for the further development and application of flavonoids for food safety.

Preparation of soybean isolate protein/xanthan gum/agar-Lycium ruthenicum anthocyanins intelligent indicator films and its application in mutton preservation

The preparation of intelligent indicator films containing anthocyanins and their utilization for real-time monitoring of meat freshness represents a prominent research topic of food packaging. In this study, anthocyanins (ALR) were extracted from Lycium ruthenicum (LR) using solvent extraction. Subsequently, these anthocyanins were incorporated into films composed of soybean isolate protein (SPI), xanthan gum (XG) and agar, resulting in SPI/XG/Agar-ALR pH-responsive intelligent indicator films. The physical properties, structural characterization and application in mutton preservation were evaluated to identify the intelligent indicator films with the optimal addition ratio of ALR. The results indicated that the SPI/XG/Agar-5 % films exhibited exceptional performance in terms of thickness, mechanical properties, water vapor transmission rate, oxygen transmission rate and light transmission rate. Scanning electron microscope observations revealed that the SPI/XG/Agar-5 % films possessed a smooth and flat surface, while fourier transform infrared spectroscopy analysis confirmed their excellent compatibility. The DPPH radical scavenging rate of the SPI/XG/Agar-5 % film reached 80.75 ± 0.63 %. When applied to the preservation of mutton, the SPI/XG/Agar-5 % film significantly extended the shelf life and effectively monitored the freshness of the meat. This study not only broadens the application scope of Lycium ruthenicum anthocyanins but also provides a foundation for the development of smart packaging materials.

Sustainable Smart Packaging from Protein Nanofibrils

Smart packaging technologies are revolutionizing the food industry by extending shelf life and enhancing quality monitoring through environmental responsiveness. Here, a novel smart packaging concept is presented, based on amyloid fibrils (AM) and red radish anthocyanins (RRA), to effectively monitor food spoilage by color change. A protein nanofibrils biofilm is developed from whey protein, which is functionalized with RRA to endow the resulting films with advanced monitoring capabilities. A comprehensive characterization, including pH responsiveness, water vapor permeability, thermal and mechanical testing, and colorimetric responses, demonstrates the superiority of AM/RRA films compared to control films based on whey monomer building blocks. The findings indicate that the AM/RRA films can effectively monitor, for example, shrimp freshness, showing visible changes within one day at room temperature and significant alterations in color after two days. Furthermore, these films exhibit high antibacterial and antioxidant activities, reinforcing their suitability for efficient food packaging. By integrating bio-based materials from whey and natural anthocyanins, this research presents a biodegradable, sustainable, and cost-effective smart packaging solution, contributing to eco-friendly innovations in food preservation.

Smart and Sustainable 3D-Printed Nanocellulose-Based Sensors for Food Freshness Monitoring

Annually, about one-third of the food produced around the world is wasted due to spoilage. Food contamination and spoilage, along with the use and disposal of nondegradable packaging materials, impact human health and have huge economic and sustainability implications. Achieving sustainability within the food system requires innovative solutions to reduce the environmental footprint. Herein, we describe the formulation, scalable manufacturing, and characterization of three-dimensional (3D)-printed sensors prepared from a mixture of edible biopolymer hydrogels, 8% alginate, and 10% gelatin and nanocellulose (CNC) as a reinforcement filler. We demonstrate that incorporating CNC improves the overall mechanical performance of the printed film and enables the stabilization of pH-responsive dyes for monitoring the release of total volatile basic nitrogen (TVB-N), an indicator of food freshness. Mechanical performance enhancement includes increases of 43% in load-depth indentation, 28.2% in hardness, and 17.4% in elastic modulus. This enhancement facilitates its use as a smart label technology, enabling the visual assessment of spoilage when placed inside packaging over a period of 3 days at room temperature. The 3D-printed film exhibits excellent durability, flexibility, shape memory, and robustness, along with pH responsiveness, showing distinctive color changes over the pH range of 2 to 13. These performances are demonstrated in packaged meat and fish, enabling monitoring over several days and illustrating potential as a real-time freshness indicator. The material formulations developed in this work are biodegradable, eco-friendly, and inexpensive, making them suitable candidates for smart and sustainable food packaging.

Blueberry extract loaded into rice milk/alginate-based hydrogels as pH-sensitive systems to monitor the freshness of minced chicken

Hydrogel beads from rice milk and blueberry (BB) skins were fabricated as novel bio-based pH-sensitive devices. The encapsulation of BB into rice milk/alginate beads was achieved through a simple methodology. The colourimetric response of beads in different pH media was evaluated along with the proof of reusability, showing appropriate reversibility. The evaluation of the stability of BB-loaded beads in accelerated ageing conditions (4, 25 and 40 °C and under visible/UV light) showed high stability of beads (up to 28 days) even in the presence of harsh conditions. The half-time of cyanidin-3-glucoside decreases at high temperatures and under UV light exposure. The sensitivity to ammonia (NH3) and trimethylamine (TMA), as main spoilage volatiles of protein food products, was evaluated. The detection limits (LOD) for NH3 and TMA were 22.4 ppm and 72.1 ppm, respectively. Finally, the hydrogel beads were applied to monitor the spoilage of minced chicken breast. The colour of the beads, changing from dark reddish to green/yellowish and indicative of a high level of amine, could be detected by the naked eye after 3-5 days. This research proposes a sustainable, low-cost, and simple method to fabricate BB-loaded hydrogel beads as a promising tool for intelligent packaging applications.

The latest research progress on polysaccharides-based biosensors for food packaging: A review

In recent years, polysaccharide-based biosensors have emerged as promising technologies for intelligent food packaging, offering innovative solutions to enhance food quality and safety. This review highlights advancements in designing, developing, and applying these biosensors, particularly those utilizing polysaccharides such as chitosan, cellulose and alginate. Engineered with nanomaterials like ZnO, silver, and carbon nano-tubes demonstrated high sensitivity in real-time monitoring of food spoilage indicators, including pH changes, volatile nitrogen compounds and microbial activity. We discuss the electrochemical properties of these biosensors, highlighting how the integration of electrochemical methods significantly improves their detection capabilities within packaging environments, leading to sensor sensitivity enhancement, greater accuracy, and spoilage detection, ultimately extending the shelf life of perishable food products. Additionally, the review addresses the practical challenges of industrial implementation and explores future research directions for optimizing sensor functionality and scalability. The findings underscore the potential of polysaccharide-based intelligent packaging as a sustainable and effective alternative to conventional methods, paving the way for broader commercial adoption.

Anthocyanin-rich grape pomace extract encapsulated in protein fibers: Colorimetric profile, in vitro release, thermal resistance, and biological activities

Red wine grape pomace is an important source of bioactive compounds with biological activities of interest. Grape pomace extract can be encapsulated in ultrafine fibers using the electrospinning technique. Encapsulation is used to increase stability and protect the phenolic compounds in the extract. In this study, zein fibers were developed for encapsulation of grape pomace extract (0 %, 5 %, 10 %, and 15 % w/w). The extract was evaluated for colorimetric profile, whereas the ultrafine zein fibers carrying the extract were assessed for morphology, loading capacity, in vitro release profile, thermal and thermogravimetric properties, thermal resistance, hydrophilicity, and antioxidant and antimicrobial activities. The grape pomace extract changed color depending on pH, ranging from pink (pH 1) to yellow (pH 13 and 14). The fibers presented a smooth and uniform structure, with diameters of approximately 450 nm and a loading capacity of up to 82 %. The membranes of ultrafine fibers demonstrated hydrophilic behavior, and the in vitro release profile was dependent on the concentration of the added extract. Furthermore, the fibers were observed thermally protect the encapsulated compounds and maintain their antioxidant and antimicrobial activities. These findings indicate that the produced material has potential applications in the development of active and intelligent packaging for the food industry.

Rapid-response nanofiber films against ammonia based on black wolfberry anthocyanins, polyvinyl alcohol and sodium alginate for intelligent packaging

To develop novel intelligent indicator films, the mixture of anthocyanin (BWA), polyvinyl alcohol (PVA) and sodium alginate (SA) were spun into PVA/SA/BWA nanofiber films with BWA concentration of 0 %, 5 %, 10 %, and 15 % (based on PVA and SA) via electrospinning technology. The results showed that the BWA was sensitive to pH and was controlled release from films. With increasing BWA concentration, the fiber diameter, tensile strength, and elongation at break gradually decreased, while water contact angle, thickness, moisture content, and antioxidant properties gradually increased. The electrospinning films exhibited high sensitivity to ammonia with rapid color changes in 1 s and excellent color reversibility and color stability within 21 d. The application for shrimp packaging showed that the colorimetric response of the films was closely related to the changes in pH, total volatile basic nitrogen (TVB-N), and total viable count (TVC) of shrimp. This suggests that the prepared films are promising in application for intelligent packaging.

In situ growth of curcumin-loaded cellulose composite film for real-time monitoring of food freshness in smart packaging

Visual pH-responsive packaging material is particularly important in food supply chain safety monitoring due to their non-destructive monitoring method and intuitive result. However, it has always been limited by the instability performance of pH-response components and carriers, which further hinders its wide food safety application. To address these challenges, we selected cellulose with remarkable biocompatibility and mechanical properties as the carrier, and high pH-responsive curcumin to develop a smart packaging material (RC/GC composite film) with real-time food safety monitoring. Compared with pure cellulose film, the RC/GC composite film exhibited excellent mechanical properties (4-fold enhancement) and thermal stability (100 °C increasing). Meanwhile, based on the first reported strategy of curcumin in-situ growth during cellulose film formation, the RC/GC composite film exhibited exceptional antioxidant activity (89.2 %), antimicrobial property (91.6 %), and significant pH-responsive sensitivity (within 15 s). This innovative approach offers a new strategy for easy-to-use and effective monitoring of food spoilage in packaging materials.

Enhanced pH-sensitive anthocyanin film based on chitosan quaternary ammonium salt: A promising colorimetric indicator for visual pork freshness monitoring

An intelligent pH response indicator film is an easy-to-use device for the real-time monitoring of meat freshness during transport and storage. Therefore, a novel pH-sensitive anthocyanin indicator film composed of polyvinyl alcohol-blueberry anthocyanin (BA)-2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) called PAH-2.0 with 1.2 mg/mL HACC to monitor meat freshness using HACC as the colorimetric enhancer has been developed. BA and HACC were mixed and immobilized in the polyvinyl alcohol matrix by hydrogen bonds, as confirmed via Fourier-transform infrared spectroscopy and X-ray diffraction. The inclusion of HACC improved the color stability and antioxidant and antibacterial properties of the PAH-2.0 film. When applied to pork for freshness monitoring at 4 °C, three freshness stages, including fresh, sub-fresh, and spoiled, could be clearly distinguished based on the color variations of the PAH-2.0 film. The distinct hierarchical color change from purple to blue-violet and finally to grayish-blue was highly correlated with the indicators of pork freshness: pH values, total volatile basic nitrogen, and total viable count. This study provides a simple and promising approach for fabricating meat freshness indicator films with high color recognition accuracy, thereby offering new possibilities for visual meat freshness monitoring.

Fast and sustainable production of smart nanofiber mats by solution blow spinning for food quality monitoring: Potential of polycaprolactone and agri-food residue-derived anthocyanins

The shelf life of perishable foods is estimated through expensive and imprecise analyses that do not account for improper storage. Smart packaging, obtained by agile manufacturing of nanofibers functionalized with natural pigments from agri-food residues, presents promising potential for real-time food quality monitoring. This study employed the solution blow spinning (SBS) technique for the rapid production of smart nanofiber mats based on polycaprolactone (PCL), incorporating extracts of agricultural residues rich in anthocyanins from eggplant (EE) or purple cabbage (CE) for monitoring food quality. The addition of EE or CE to the PCL matrix increased the viscosity of the solution and the diameter of the nanofibers from 156 nm to 261-370 nm. The addition of extracts also improved the mechanical and water-related properties of the nanofibers, although it reduced the thermal stability. Attenuated total reflectance Fourier-transform infrared spectroscopy confirmed the incorporation of anthocyanins into PCL nanofibers. Nanofiber mats incorporated with EE or CE exhibited visible color changes (ΔE ≥ 3) in response to buffer solutions (pH between 3 and 10), and ammonia vapor. Smart nanofibers have demonstrated the ability to monitor fish fillet spoilage through visible color changes (ΔE ≥ 3) during storage. Consequently, smart nanofibers produced by the SBS technique, using PCL and anthocyanins from agro-industrial waste, reveal potential as smart packaging materials for food.

Evaluation of low-temperature ultrasonic marination of pork meat at various frequencies on physicochemical properties, myoglobin levels, and volatile compounds

This study aims to evaluate the pork meat quality after ultrasonic brining at different frequencies, thereby providing a more comprehensive understanding of the effects of ultrasound marination on meat. The texture profile analysis showed that ultrasonic curing at various frequencies significantly improved the textural properties of samples, especially at 26.8 kHz, resulting in a reduction of tenderness, hardness, and chewiness values by 44%, 43%, and 44%, respectively. The cooking loss of samples marinated by ultrasound decreased from 27% without ultrasonic treatment to 22%, indicating a significant improvement in water-holding capacity, while the changes in pH had only a subtle impact on pork quality. Meanwhile, the color of pork became more rosy hue due to decreased L⁎ values and increased a⁎ values, which was mainly attributed to an elevated proportion of oxymyoglobin and reduced metmyoglobin content. Additionally, ultrasonic marination did not exert a negative impact on the oxidation of pork protein and lipids. After roasting, samples marinated by ultrasound exhibited a significantly higher abundance of volatile flavor compounds compared to static marinated meat (with an increase of 16 flavor substances) and fresh pork (with an increase of 24 flavor substances), demonstrating the efficacy of ultrasonic marination in enhancing the overall flavor and taste profile of pork. Consequently, the application of ultrasonic technology holds great potential for the "home kitchen type" rapid marination.

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 and application of visual fish freshness indicator film incorporated with anthocyanins encapsulation by whey protein-propylene glycol alginate nanoparticles

Intelligent indicator packaging has gained increased attention in meeting the demand for reducing food waste and mitigating the risk of food poisoning. This study focused on the preparation, characteristics, and application of freshness indicator films based on polyvinyl alcohol (PVA) and anthocyanins (ACNs)-encapsulated whey protein (WP)-propylene glycol alginate (PGA) nanoparticles. The successful encapsulation of ACNs by WP-PGA nanoparticles improved the stability of ACNs and their encapsulation efficiency (EE) reached 95.34 %. The incorporation of nanoparticles into the structure of the PVA films was justified by SEM, XRD, and ATR-FTIR, and resulted in a decrease in water vapor permeability (WVP) from 15.76 (×10-7 g·m-1·Pa-1·h-1) to 8.40 (×10-7 g·m-1·Pa-1·h-1) and an increase in scavenging rate of DPPH radical from 1.47 % to 18.92 %. The light-blocking property and mechanical properties of the films were also improved, and they showed visible color change in response to pH 2-12 and high color stability after 14 days of storage at 4 °C and 25 °C. Furthermore, the freshness indicator films underwent a noticeable transformation from rosy red to gray at bighead carp head spoilage. Therefore, the encapsulation of ACNs using WP-PGA nanoparticles provides a promising non-destructive and real-time freshness indication of aquatic products during both storage and transportation processes.

Intelligent Packaging Systems with Anthocyanin: Influence of Different Polymers and Storage Conditions

With the aim of meeting the growing demand for safe food, intelligent packaging has emerged, which monitors the conditions of the food and informs the consumer about its quality directly at the time of purchase. Among intelligent packaging options, colorimetric indicator films, which change color in response to changes in the food, such as the release of volatile compounds, have been widely studied. Among them, pH indicator films composed of dyes sensitive to small variations in the pH value of the food surface have received greater attention in recent years. Anthocyanins, which are natural pigments, have stood out as one of the most commonly used sources of dyes in the production of these indicator films. In this context, the present review aims to present an updated overview of research employing anthocyanins in indicator films, including their stability under different storage conditions, the influence of different polymers used in their production, and alternative techniques for maintaining stability.

A sensing label or gel loaded with an NIR emission fluorescence probe for ultra-fast detection of volatile amine and fish freshness

A simple benzopyran-based fluorescence probe DCA-Apa detection of volatile amine has been synthesized. DCA-Apa can recognize volatile amines by dual channel mode (changing from blue to light yellow in sunlight, and from weak pink to orange under 365 nm) in pure water system. DCA-Apa has the advantages of ultra-fast response (∼6 s), NIR emission (655 nm), and a good fluorescence response for many amines. The sensing label or gel loaded with DCA-Apa was prepared by the dipping or mixing method using filter paper or gelatin as solid carriers, which can identify volatile amine vapor and monitor the freshness of salmon by colorimetric and fluorescent dual channels. When the color of the label changes to light yellow-green or the fluorescence of the label becomes orange fluorescence (365 nm UV lamp), it indicates that the fish has rotted. The two-channel method makes up for the deficiency of the single colorimetric method, and establishes a theoretical foundation for more precise assessment of fish freshness.

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.