Colorimetric film based on polyvinyl alcohol/okra mucilage polysaccharide incorporated with rose anthocyanins for shrimp freshness monitoring

Multifunctional metal-organic framework-enhanced sodium alginate-based intelligent indicator: Mechanism and application for freshness monitoring

Intelligent food packaging has recently gained significant attention due to the heightened consumer awareness regarding food quality. Although anthocyanins avoid safety issues, the instability and leakage of anthocyanins restrict their utilization in freshness indicator labels. In this study, we introduced an innovative metal-organic framework (UiO-66-NH2) synergistic pH-colorimetric label with fast ammonia-responsive, incorporating sodium alginate, red cabbage anthocyanin, and UiO-66-NH2. The cross-linked sodium alginate substrate enabled the label to possess superior insolubility. The microscopic morphology of the labels was intricately analyzed, while their sensitivity was rigorously tested utilizing ammonia as a representative gas. Due to the remarkable UV absorption capability of UiO-66-NH2 and various molecular interactions with anthocyanins, the label exhibited good UV absorption, enhanced stability, and optimized performance in reducing anthocyanin leakage, ensuring the stability and effectiveness of the labels in practical applications. The prepared label exhibited good specificity for volatile amines and ammonia gases, and robust anti-interference properties, enabling visualization and early detection of shrimp spoilage during storage at different temperatures. The strategy employed in this study presents promising new possibilities for developing intelligent packaging solutions for food products.

Application of seed mucilage as functional biopolymer in meat product processing and preservation

Meat products consumption is rising globally, but concerns about sustainability, fat content, and shelf life. Synthetic additives and preservatives used for extending the shelf life of meat often carry health and environmental drawbacks. Seed mucilage, natural polysaccharides, possesses unique functional properties like water holding, emulsifying, and film forming, offering potential alternatives in meat processing and preservation. This study explores the application of seed mucilage from diverse sources (e.g., flaxseed, psyllium, basil) in various meat and meat products processing and preservation. Mucilage's water-holding and emulsifying properties can potentially bind fat and decrease the overall lipid content in meat and meat-based products. Moreover, antimicrobial and film-forming properties of mucilage can potentially inhibit microbial growth and reduce oxidation, extending the shelf life. This review emphasizes the advantages of incorporating mucilage into processing and coating strategies for meat and seafood products.

Preparation and characterization of intelligent and active bi-layer film based on carrageenan/pectin for monitoring freshness of salmon

This work aimed to develop and characterize a novel bi-layer film (BIF) for monitoring the freshness of salmon. The indicator layer consists of carrageenan (Car), pectin (PEC) and purple sweet potato anthocyanin (PSPA), and the antibacterial layer consists of Car and magnolol (Mag). The results showed that the Car/Mag2 had the optimal water resistance: the static water contact angle of 80.36 ± 0.92 °, moisture content of 31.38 ± 0.86 %, swelling degree of 92.96 ± 0.46 %, and water solubility of 40.08 ± 1.17 %, and showed excellent antibacterial properties against E. coli and S. aureus with antibacterial rate of 86.13 % ± 0.10 % and 97.53 % ± 0.02 %, respectively. Then BIFs with different PSPA concentration were tested. The morphology, mechanical and water vapor properties (WVP) of the BIFs were studied, and its application in salmon preservation was evaluated. The mechanical properties and WVP test results showed that the BIF0.2 had the optimal Tensile strength (TS) and WVP values. The BIFs showed distinguishable color changes between the pH ranges of 3-10. The shelf life of salmon packaged by BIF0.2 was prolonged by 2 days. Moreover, the BIF0.2 was able to effectively monitor salmon freshness. In conclusion, the BIF has great potential for monitoring salmon meat freshness.

Preparation of a colorimetric hydrogel indicator reinforced with modified aramid nanofiber employing natural anthocyanin to monitor shrimp freshness

The pH-responsive hydrogels have potential applications in food visualization detection, but their fragile mechanical properties limit their applicability. The excellent mechanical properties and thermal stability of aramid nanofibers (ANFs) can improve the structural stability of hydrogels. In this study, the surface properties of ANFs were enhanced through modification to improve their surface activity. The modified ANFs, designated as ANF-SN, were produced following treatment with a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3), which led to increased reactivity and dispersibility of the ANFs due to the proliferation of active groups on their nanofiber surface. The preferred anthocyanin extract from purple sweet potatoes (purple sweet potato extract [PSPE]) had significant color responses to pH (2-12) and ammonia vapor. A stable dual-network colorimetric hydrogel was fabricated by combining ANF-SN, polyvinyl alcohol/sodium alginate (PVA/SA), and PSPE through a two-step method (freeze-thawing and staining). Characterization analysis showed that the strong acid modification of ANFs effectively improved their chemical reactivity. ANF-SN was better than ANF in promoting the formation of hydrogen bond networks, enhancing hydrogel network structures, and improving the viscoelasticity of hydrogels. The optimal hydrogel indicator PVA/SA/ANF-SN/PSPE had good color responsiveness and sensitivity to ammonia. It can also be used to further determine shrimp freshness value using a smartphone and RGB color-picking software.

Sodium alginate-based indicator film with enhanced physicochemical properties induced by cellulose nanocrystals and monitor the freshness of chilled meat

Intelligent indicator films with colorimetric pH indicator properties were developed, incorporating black soybean seed coat anthocyanin (BA), cellulose nanocrystals (CNC), and sodium alginate (SA) to monitor meat freshness. The effect of different CNC additions on the microstructure, water barrier properties of the films, and BA release kinetics were comprehensively investigated. The results showed that with the increasement of CNC addition, the mechanical properties of SA/BA/CNC films were improved, the water contact angle significantly increased from 51.6° to 69°. Moreover, water solubility, vapor adsorption, and permeability significantly decreased, indicating enhanced water barrier properties. The release kinetic results showed that BA was released rapidly within 72 h and slowly thereafter, and its release process was described by Fick's model. Films with 7 % and 10 % CNC had lower BA diffusion coefficients. Their diffusions were formulated as linear regression equations (y = nx + a), where R2 was >0.80 and n was <0.50. Structural characterization showed that CNC immobilized BA mainly through hydrogen bonding, forming compact network microstructures with SA and BA. Meat freshness monitoring results showed that the film containing 7 % CNC showed visible color changes with increasing total volatile basic nitrogen and pH, along with low BA release, high water barrier and mechanical properties. Therefore, CNC has great potential for improving the physicochemical properties of indicator films, and the intelligent colorimetric indicator film could be applied to various food product.

Recent advancements in chitosan-based intelligent food freshness indicators: Categorization, advantages, and applications

With an increasing emphasis on food safety and public health, there is an ongoing effort to develop reliable, non-invasive methods to assess the freshness of diverse food products. Chitosan-based food freshness indicators, leveraging properties such as biocompatibility, biodegradability, non-toxicity, and high stability, offer an innovative approach for real-time monitoring of food quality during storage and transportation. This review introduces intelligent food freshness indicators, specifically those utilizing pH-sensitive dyes like anthocyanins, curcumin, alizarin, shikonin, and betacyanin. It highlights the benefits of chitosan-based intelligent food freshness indicators, emphasizing improvements in barrier and mechanical properties, antibacterial activity, and composite film solubility. The application of these indicators in the food industry is then explored, alongside a concise overview of chitosan's limitations. The paper concludes by discussing the challenges and potential areas for future research in the development of intelligent food freshness indicators using chitosan. Thus, chitosan-based smart food preservation indicators represent an innovative approach to providing real-time data for monitoring food quality, offering valuable insights to both customers and retailers, and playing a pivotal role in advancing the food industry.

Smart nano-inks based on natural food colorant for screen-printing of dynamic shelf life of shrimp

Intelligent packaging embedded with food freshness indicators can monitor food quality and be deployed for food safety and cutting food waste. The innovative nano-inks for dynamic shelf-life printing based on natural food colorant with application in real-time monitoring of shrimp freshness were prepared. Co-assembly of saffron petal anthocyanin (SPA) with hydrophobic curcumin (Cur) into chitin nano-scaffold (particle sizes around 26 ± 8 nm) could deliver hindering SPA leaching, confirmed by FT-IR, FE-SEM, AFM, and color stability test. The best response to pH-sensitivity was found in a ratio of (1:4) Cur/SPA (30% (v/w) in ChNFs that was correlated with the chemical and microbial changes of shrimp during shrimp freshness. However, smart screen-printed inks signified higher responsiveness to pH changes than FFI films. Therefore, smart-printed indicators introduced the excellent potential for a short response time, easy, cost-effective, eco-friendly, co-assembly, great color stabilities, and lifetime for nondestructively freshness monitoring foods and supplements.

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.

The application of film based on gelatin/hydroxymethyl cellulose and red beetroot betalain in smart food packaging

Edible films containing anthocyanin and betacyanin as indicators of freshness are promising systems for food smart packaging. This research aimed to develop a smart color film for food packaging using gelatin/hydroxypropylmethyl cellulose (HPMC) and red beet betalain. In this study, edible films with different ratios of gelatin to HPMC were prepared successfully, and the ratio of 3:1 was determined as optimal samples based on water vapor permeability (WVP) and mechanical properties. Betalain with different concentrations was then added to the optimal film, and the physical and mechanical properties of the resulting films were evaluated. Also, TVB-N test to assess their ability to detect beef meat and shrimp spoilage was studied. The addition of betalain improved the solubility, WVP, mechanical properties, and 2,2-diphenyl-l-picrylhydrazyl free radical scavenging activity of the film. As a final point, the incorporation of betalain into the gelatin/HPMC films can be used to indicate the freshness of food.

Unveiling the multifaceted world of anthocyanins: Biosynthesis pathway, natural sources, extraction methods, copigmentation, encapsulation techniques, and future food applications

Numerous datasets regarding anthocyanins have been noted elsewhere. These previous studies emphasized that all processes must be carried out meticulously from the source used to obtain anthocyanins to their inclusion in relevant applications. However, today, full standardization has not yet been achieved for these processes. For this, presenting the latest developments regarding anthocyanins under one roof would be a useful approach to guide the scientific literature. The current review was designed to serve the stated points. In this context, their biosynthesis pathway was elaborated. Superior potential of fruits and certain by-products in obtaining anthocyanins was revealed compared to their other counterparts. Health-promoting benefits of anthocyanins were detailed. Also, the situation of innovative techniques (ultrasound-assisted extraction, subcritical water extraction, pulse electrical field extraction, and so on) in the anthocyanin extraction was explained. The stability issues, which is one of the most important problems limiting the use of anthocyanins in applications were discussed. The role of copigmentation and various encapsulation techniques in solving these stability problems was summarized. This critical review is a map that provides detailed information about the processes from obtaining anthocyanins, which stand out with their functional properties, to their incorporation into various systems.

Biofilms from poly-vinyl alcohol/palmyra root sprout with Boswellia serrata, carbon dots and anthocyanin for sensing the freshness of sardine fish

One of the main issues that customers worldwide have is food adulteration. In commercial packages, freshness cannot always be determined visually. Here, we propose sensitive films for use in food packaging that could alter colour to indicate a change in freshness. Hybrid, multifunctional, and eco-friendly films were prepared from polyvinyl alcohol/palmyra root sprout (PVA/PRS), fused with soy protein isolate carbon dot (CD), Boswellia serrata (BS), and Clitoriaternatea anthocyanin (CTE). The films showed pH sensitivity, antioxidant, and UV barrier properties. By creating hydrogen bonds between PRS and the other fillers, adding these substances makes PVA less crystallized. These interactions were verified by infrared Fourier-transform analysis. When compared to PVA, PRS films had significantly lower moisture content and swelling ratios. The UV-blocking capabilities of the films were greatly improved by the addition of CD, BS, and CTE without compromising their mechanical, thermal, or water vapor barrier properties. The composite film PVA/PRS/CD/BS/CTE exhibited a maximum tensile strength value of 69.47 ± 1.49 MPa. The CT extract provides the film with superior antioxidant properties. The colorimetric films PVA/PRS/CTE and PVA/PRS/CD/BS/CTE showed distinct pH-responsive colour-change properties as well as good colour stability. The colorimetric films were used to test the freshness of sardine fish, and they revealed unique colour changes that indicated whether the fish sample was spoiled or not.

Potato oxidized hydroxypropyl starch/pectin-based indicator film with Clitoria ternatea anthocyanin and silver nanoparticles for monitoring chilled beef freshness

Potato oxidized hydroxypropyl starch (POHS)/pectin (P) functional and smart beef freshness indicator films were prepared using butterfly pea (Clitoria ternatea) anthocyanin (BA) and silver nanoparticles (AgNPs). BA exhibited significant pH-responsive color changes. BA and AgNPs were evenly distributed within a polymer matrix to create a compatible film with POHS/P. The films containing BA and AgNPs had good UV resistance and maintained strong mechanical strength, barrier properties, and color stability. The color of the indicator film changed from purple to green when exposed to ammonia, with the 1 % POHS/P/BA/AgNPs film showing the most sensitive response. The films also demonstrated strong antibacterial and antioxidant properties. The freshness of beef was monitored using 1 % POHS/P/BA/AgNPs films and was identified as sub-fresh and spoiled on days 4 and 7, respectively. The relationship between the color change of the indicator label and the freshness of chilled beef was established: purple for fresh meat, blue for less fresh meat, and green for spoiled meat. Thus, the new POHS/P/BA/AgNPs film can serve as a smart packaging material to indicate food freshness and extend shelf life. These results suggest that POHS/P/BA/AgNPs films have significant potential as an active and smart food packaging material.

Development of a Sensitive Colorimetric Indicator for Detecting Beef Spoilage in Smart Packaging

This study aimed to fabricate and characterize a novel colorimetric indicator designed to detect ammonia (NH3) and monitor meat freshness. The sensing platform was constructed using electrospun nanofibers made from polylactic acid (PLA), which were then impregnated with anthocyanins as a natural pH-sensitive dye, extracted from red cabbage. This research involved investigating the relationship between the various concentrations of anthocyanins and the colorimetric platform's efficiency when exposed to ammonia vapor. Scanning electron microscope (SEM) results were used to examine the morphology and structure of the nanofiber mats before and after the dip-coating process. The study also delved into the selectivity of the indicator when exposed to various volatile organic compounds (VOCs) and their stability under extreme humidity levels. Furthermore, the platform's sensitivity was evaluated as it encountered ammonia (NH3) in concentrations ranging from 1 to 100 ppm, with varying dye concentrations. The developed indicator demonstrated an exceptional detection limit of 1 ppm of MH3 within just 30 min, making it highly sensitive to subtle changes in gas concentration. The indicator proved effective in assessing meat freshness by detecting spoilage levels in beef over time. It reliably identified spoilage after 10 h and 7 days, corresponding to bacterial growth thresholds (107 CFU/mL), both at room temperature and in refrigerated environments, respectively. With its simple visual detection mechanism, the platform offered a straightforward and user-friendly solution for consumers and industry professionals alike to monitor packaged beef freshness, enhancing food safety and quality assurance.

Structure, chemical modification, and functional applications of mucilage from Mimosa pudica seeds - A review

Mimosa pudica (MP) is an ornamental plant due to seismonastic movements that close leaves and fall petioles in response to touch, wind, light, heat, cold, and vibration. The seeds of MP secrete smart, biocompatible, and non-toxic mucilage that has captivated researchers due to its widespread use in various fields such as pharmaceuticals and biotechnology. The mucilage is responsive to pH, salt solutions, and solvents and acts as a binder in tablet formulations for targeted drug delivery. The mucilage is chemically modifiable via acetylation, succinylation, and graft polymerization. Chemically modified MP mucilage appeared supersorbent for heavy metal ion uptake. Nanoparticles synthesized using mucilage as a reducing and capping agent displayed significant antimicrobial and wound-healing potential. Crosslinking of mucilage using citric acid as a crosslinking agent offers a sustained release of drugs. The present review is aimed to discuss extraction optimization, structure, modification, and the stimuli-responsive nature of mucilage. The review article will cover the potential of mucilage as emulsifying, suspending, bio-adhesive, gelling, and thickening agent. The role of mucilage as a capping and reducing agent for nanoparticles will also be discussed.

Electrospun fiber mats based on chitosan-carrageenan containing Malva sylvestris anthocyanins: Physic-mechanical, thermal, and barrier properties along with application as intelligent food packaging materials

This study aimed to encapsulate Malva sylvestris extract (MSE) into chitosan-carrageenan (CH-KC) fibers using the electrospinning technique and monitor the freshness of silver carp fillets during the refrigerated storage conditions for 8 days. The CH-KC + MSE 4 % fiber mats were red at pH values lower than 3, purple at pH 4-6, dark blue at pH 7, green at pH 8-10, and brown at pH 11-12. The tensile strength, elongation at break, water vapor permeability, oxygen transmission rate, moisture content, and water solubility of fabricated fiber mats were 7.71-11.02 MPa, 13.12 %-30.00 %, 7.35-20.01 × 10-4 g mm/m2 h Pa, 3.81-8.23 cm3/m2 h, 15.74 %-27.34 %, and 3.90 %-7.56 %, respectively. Regarding the potential application of a fabricated indicator for freshness monitoring of silver carp fillets, total viable count, psychrotrophic bacterial count, pH, and total volatile basic nitrogen reached 8.91 log CFU/g, 8.03 log CFU/g, 8.10, and 40.18 mg N/100 g at the end of the study, respectively. Meanwhile, the CH-KC + MSE 4 % fiber mat color changed from white to green. These findings suggest that CH-KC + MSE 4 % fiber mats can be further utilized in the food industry to control the freshness of refrigerated silver carp fillets.

Customized development of 3D printed anthocyanin-phycocyanin polychromatic oral film via chondroitin sulfate homeostasis: A platform based on starch and κ-carrageenan

The development of oral film with diverse colors and customized nutrition is in line with the innovation of emerging food. In this study, polychromatic system was formed by regulating the ratio of phycocyanin (PC) to blueberry anthocyanin (BA). Further, chondroitin sulfate (CS) was utilized to achieve color-enhanced and homeostatic effects on PC-BA, and κ-carrageenan (KC) - starch complex was exploited as printing ink to construct oral film system. The color-enhanced effect of CS is mainly related to the complexation of sulfate groups, and the film-forming substrates are combined mainly through hydrogen bonding. In addition, the proportion of KC modulated the gel structure of printing ink, and affected 3D printability and physical properties of oral film. OF II (1.5 % KC content) had a uniform and dense network structure, with the most stable color and the highest BA retention (70.33 %) after 8 d of light exposure. Importantly, OF II had an excellent slow-release effect, and BA release rate was as high as 92.52 %. The optimized components can form polychromatic oral film with controllable color and structure, and provide new insights for the creation of sensory personalized and nutritionally customized food.

Sustainable food packaging: Harnessing biowaste of Terminalia catappa L. for chitosan-based biodegradable active films for shrimp storage

Shrimp, a globally consumed perishable food, faces rapid deterioration during storage and marketing, causing nutritional and economic losses. With a rising environmental consciousness regarding conventional plastic packaging, consumers seek sustainable options. Utilizing natural waste resources for packaging films strengthens the food industry. In this context, we aim to create chitosan-based active films by incorporating Terminalia catappa L. leaves extract (TCE) to enhance barrier properties and extend shrimp shelf life under refrigeration. Incorporation of TCE improves mechanical, microstructural, UV, and moisture barrier properties of the chitosan film due to cross-linking interactions, resulting in robust, foldable packaging film. Active TCE film exhibits high antioxidant property due to polyphenols. These films also exhibited low wettability and showed hydrophobicity than neat CH films which is essential for meat packaging. These biodegradable films offer an eco-friendly end-of-life option when buried in soil. TCE-loaded films effectively control spoilage organisms, prevent biochemical spoilage, and maintain shrimp freshness compared to neat CH films during refrigerated condition. The active TCE film retains sensory attributes better than neat chitosan, aligning with consumer preference. The developed edible and active film from waste sources might offer sustainable, alternative packaging material with a lower carbon footprint than petroleum-based sources.

Smart labels based on polyvinyl alcohol incorporated with chitosan nanoparticles loaded with grape extract: Functionality, stability and food application

Anthocyanins (ACNs) are natural compounds with potential applications due to their colorimetric response to pH. Due to their sensitivity to various environmental factors, nanoencapsulation with biopolymers is a successful strategy for stabilizing ACNs. In this work ACNs were extracted from grape skins and encapsulated into chitosan (CS) nanoparticles by ionic gelation using sodium tripolyphosphate (TPP) as a cross-linking agent. CS nanoparticles loaded with ACNs had particle sizes between 291 and 324 nm and polydispersity index around 0.3. The encapsulation efficiency of ACNs was approximately 60 %; and encapsulated anthocyanins (ACN-NPs) exhibited color change properties under different pH conditions. pH-sensitive labels based on polyvinyl alcohol (PVA) were prepared by the casting method. The effect of incorporating ACN-NPs on the physical, structural, and pH-sensitive properties of PVA labels was evaluated, and its application as shrimp freshness indicator was studied. The nanoencapsulation protected ACNs against heat and light treatments, preserving the original purple color. When applying the label, visible changes from red to blue until reaching yellow were observed with the change in the quality of the shrimp at the refrigeration temperature. The results suggest that PVA labels containing ACNs encapsulated in C-NPs can be used as smart packaging labels in the food industry.

Active cellulose acetate/purple sweet potato anthocyanins@cyclodextrin metal-organic framework/eugenol colorimetric film for pork preservation

As a natural pH-sensing colorant, purple sweet potato anthocyanins (PSPAs) have demonstrated great potential in colorimetric film for freshness monitoring. However, the photothermal instability of PSPAs is still a challengeable issue. Herein, γ-cyclodextrin metal-organic framework (CD-MOF) loaded with PSPAs (PSPAs@CD-MOF, i.e., PM) and eugenol (EUG) were incorporated in cellulose acetate (CA) matrix for developing a smart active colorimetric film of CA/PM/EUG, where PM and EUG were hydrogen-bonded with CA. Attentions were focused on the photothermal colorimetric stability, colorimetric response, and antibacterial activity of the films. The presence of PM and EUG endowed the film outstanding UV-blocking performance and enhanced the barrier against water vapor and oxygen. Target film of CA/PM15/EUG10 had good photothermal colorimetric stability due to the protection of CD-MOF on PSPAs and the color changes with pH-stimuli were sensitive and reversible. In addition to antioxidant activity, CA/PM15/EUG10 had antibacterial activity against Escherichia coli and Staphylococcus aureus. The application trial results indicated that the CA/PM15/EUG10 was valid to indicate pork freshness and extended the shelf-life by 100 % at 25 °C, which has demonstrated a good perspective on smart active packaging for freshness monitoring and shelf-life extension.

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

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

Study on preservation and monitoring effect of sodium alginate-konjac glucomannan films loaded with tea polyphenols and Lycium ruthenicum anthocyanins

To investigate the efficacy of sodium alginate-konjac glucomannan (SA-KGM) films with anthocyanins (LRA) and tea polyphenols (TP) in meat, beef and grass carp were selected as representative meat products for preservation and freshness monitoring experiments at 4 °C. Concurrently, storage experiments of the films were conducted in this controlled environment. The results of the storage experiment showed that the films delayed meat spoilage by 2-4 days, nearly doubling the preservation time compared to the blank control. Additionally, the film exhibited significant capability to monitor the spoilage process of beef and grass carp. It was revealed by curve fitting analysis that there was a significant correlation between the color change of the film and the spoilage index of the meat. Throughout the storage experiment with the film, it was observed that moisture significantly influenced the microstructure and bonding situation of the films, thereby impacting their mechanical and barrier properties. However, the films were still able to maintain satisfactory physicochemical properties in general. The above findings were crucial in guiding the promotion of the film within the food preservation industry.

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.

Development and evaluation of Bauhinia Kockiana extract-incorporated sago starch intelligent film strips for real-time freshness monitoring of coconut milk

The aim of this work was to fabricate an intelligent film using sago starch incorporated with the natural source of anthocyanins from the Bauhinia Kockiana flower and use it to monitor the freshness of coconut milk. The films were developed using the casting method that included the addition of the different concentrations (0, 5, 10, 15 mg) of Bauhinia Kockiana extract (BKE) obtained using a solvent. The anthocyanin content of Bauhinia Kockiana was 262.17 ± 9.28 mg/100 g of fresh flowers. The spectral characteristics of BKE solutions, cross-section morphology, physiochemical, barrier, and mechanical properties, and the colour variations of films in different pH buffers were investigated. Films having the highest BKE concentration demonstrated the roughest structure and highest thickness (0.16 mm), moisture content (9.72 %), swelling index (435.83 %), water solubility (31.20 %), and elongation at break (262.32 %) compared to the other films. While monitoring the freshness of coconut milk for 16 h, BKE15 showed remarkable visible colour changes (from beige to dark brown), and the pH of coconut milk dropped from 6.21 to 4.56. Therefore, sago starch film incorporated with BKE has excellent potential to act as an intelligent pH film in monitoring the freshness of coconut milk.

Psyllium and okra mucilage as co-carrier wall materials for fenugreek oil encapsulation and its utilization as fat replacers in pan bread and biscuit production

This study aimed to investigate the potential use of okra and psyllium mucilage as co-carrier wall materials with whey protein and gum Arabic polymers for encapsulation of fenugreek oil to mask its undesirable flavor and promote their health benefits. Particle size, zeta potential, encapsulation efficiency, morphological properties and fatty acid profiles of crude and encapsulated oils were examined using zeta-sizer, SEM and GC-MS techniques. Crude and encapsulated fenugreek oils were added as functional ingredients during production of pan bread and biscuits. The quality characteristics (baking quality, color and organoleptic properties) of bread and biscuits as well as microbiological properties of bred samples were evaluated. Results showed that the forming microcapsules had sphere particles with the size of 5.05 and 31.64 μm for okra and pysillium mucilage, respectively and had smooth continuous surfaces with no holes or fractures. Fatty acids analysis showed that fenugreek oil is superior functional edible oil, rich in unsaturated fatty acids. The organoleptic properties of products were improved when fat replaced with encapsulated fenugreek oil with okra or psyllium mucilage. Likewise, encapsulated fenugreek oil showed antimicrobial activity in bread samples during storage period. On contrary, Bread and biscuits incorporated with crude fenugreek oil gained the lowest scores for all organoleptic parameters. Regarding these results, encapsulated fenugreek oil presents good fat alternatives in dough formulations with acceptable technological, sensory and antimicrobial properties. However, further investigations still needed regarding the biological activity of encapsulated fenugreek oil and its utilization as a food supplement in other food products.

Halochromic smart packaging film based on montmorillonite/polyvinyl alcohol-high amylose starch nanocomposite for monitoring chicken meat freshness

Polyvinyl alcohol (PVA) was blended with high amylose starch (HAS) at a ratio of 3:1, and reinforced with montmorillonite (MMT K10) at different concentrations (1, 2, 5, and 7 % w/w of polymers) and anthocyanins (ANT) to develop an active and smart packaging film. MMT addition enhanced the film's mechanical, barrier, thermal, and water resistance properties. Incorporating ANT extracted from roselle calyx into the optimal nanocomposite film (MMT/PVA-HAS II) increased the films' antioxidant, pH-response, and antibacterial properties. FTIR, XRD, and SEM confirmed the intermolecular interactions and even distribution of ANT and MMT in the film matrix. Release rate of ANT was dependent on type of simulant, with higher rate in aqueous solutions compared to alcoholic/fatty food simulants, and cytotoxicity evaluation proved safety of films for food packaging applications. Storage experiments confirmed the potential applicability of the novel halochromic smart film as a promising candidate for monitoring chicken spoilage under abusive storage conditions.

Carrageenan-based active and intelligent packaging films integrated with anthocyanin and TiO2-doped carbon dots derived from sweet potato peels

Carrageenan-based sustainable active and pH-dependent color-changing composite films were fabricated by blending anthocyanin extracted from sweet potato peel (SPA) with TiO2-doped carbon dots (Ti-CDs) prepared using the biowaste of SPA extraction. The SPA and Ti-CDs were compatible with the carrageenan matrix and were uniformly dispersed in the used polymer to form a homogeneous film with increased mechanical properties. The composite film added with SPA and 3 wt% Ti-CD showed 100 % UV protection, superb antioxidant (100 % DPPH and ABTS scavenging assay), and potent antibacterial activity (complete eradication of foodborne L.monocytogenes and E. coli strains after 3 h incubation). Additionally, the composite films showed distinguishable colorimetric responses to pH 7-12 buffers and volatile ammonia. The intelligent sensing ability of the composite film was assessed through shrimp freshness monitoring, and the film's hue shifted from pink (fresh shrimp) to yellow/brown (inedible shrimp) during storage. Shrimp packaging studies have shown that composite films retard the rate of food quality change during storage and are a good indicator of shrimp spoilage. Therefore, the designed film is expected to have high applicability as a chip, and quick on-site sensor that detects seafood quality in real-time, and a highly effective multifunctional film for better product quality preservation.

Structural homeostasis and controlled release for anthocyanin in oral film via sulfated polysaccharides complexation

Oral film is a novel functional carrier, which can provide a new pathway for the efficient absorption of anthocyanin. However, anthocyanin homeostasis in oral film is a prerequisite for achieving efficient absorption and utilization of anthocyanin. Herein, three sulfated polysaccharides, including chondroitin sulfate (CS), fucoidin (FU) and λ-carrageenan (λ-CG), were complexed with blueberry anthocyanin (BA) to prepare oral film formulations using hydroxypropyl methylcellulose (HPMC) as a film-forming matrix. The addition of three sulfated polysaccharides improved the stability of BA in content and color, which were associated with interactions between BA and polysaccharides. The BA retention rate of CS-BA/HPMC system increased 5.5-fold after 8 d of light-accelerated storage compared with the control group, showing the best homeostasis effect. CS and λ-CG enhanced the elongation at break and prolonged disintegration time of oral films. The addition of FU made the oral film denser and smoother, and had the highest BA release (75.72 %) in the simulated oral cavity system. In addition, the oral films of three sulfated polysaccharides complexed with BA showed superior antioxidant capacity. The present study provides new insights into the application of anthocyanin in film formulation carriers.

Biodegradable ion-conductive polyvinyl alcohol/okra polysaccharide composite films for fast-response respiratory monitoring sensors

Polyvinyl alcohol (PVA) and okra polysaccharide (OP) are biodegradable polymers with high hydrophilicity and good biocompatibility with potential for use as flexible humidity-sensitive materials. Herein, biodegradable flexible composite films (named POP films) were prepared from PVA, OP, and phytic acid using a solution-casting method based on. POP films exhibited excellent mechanical strength, flexibility, flame retardancy, water resistance, humidity response, and humidity-sensing characteristics. Notably, the POP humidity sensors exhibited a hysteresis value of 1.88 % relative humidity for the adsorption and desorption processes and good sensitivity over a wide humidity range of 35-95 %. In addition, the humidity sensor distinguished the frequency of nose breathing, and its response and recovery times were 0.9 and 1.98 s, respectively. The excellent performance of POP sensors in monitoring humidity and human respiratory rates demonstrates the sensor's potential for wearable smart devices.

Intelligent active films of sodium alginate and konjac glucomannan mixed by Lycium ruthenicum anthocyanins and tea polyphenols for milk preservation and freshness monitoring

To achieve real-time monitoring of food freshness, a pH-responsive film based on sodium alginate-konjac glucomannan loaded with Lycium ruthenicum anthocyanins (LRA) was prepared, with the addition of tea polyphenols (TP) to enhance the stability of LRA. The surface structure of the films was observed by AFM. The results of FTIR and molecular docking simulation showed that LRA and TP were bound to polysaccharide by hydrogen bonds. The mechanical properties, barrier properties, and antioxidant/antibacterial properties of the films were significantly improved and the films showed obvious color response to pH. Notably, the AFM images showed TP and LRA could lead to more severe damage to the bacterial structure. The results of molecular docking simulation suggested that TP and LRA could act on different components of the bacterial cell wall, indicating their synergistic mechanism in antimicrobial activity. Moreover, the stability of LRA was improved due to the interactions of TP and polysaccharides with LRA. The aggregates formed by TP and LRA were clearly observed by AFM. Finally, the film showed excellent preservation and freshness monitoring effect in milk. In conclusion, TP-LRA-SA-KGM intelligent film exhibited excellent performance and represented a promising novel food packaging material with potential applications.

Dual-function β-cyclodextrin/starch-based intelligent film with reversible responsiveness and sustained bacteriostat-releasing for food preservation and monitoring

The full combination of high sensitivity indication and long-lasting bacteriostatic function is an innovative need to meet the practicality of intelligent film packaging systems for food products. Hence, Blueberry anthocyanins (BA) copigmentated by ferulic acid (FA) was used as an indicator, and cinnamon essential oil (CO) encapsulated by β-cyclodextrin (β-CD) as a bacteriostat, potato starch (PS) as a film-forming substrate to prepared a dual-function starch-based intelligent active packaging film with pH indicator and antibacterial function. FA had the best copigmentation effect with a threefold increase in a value compared to other phenolic acids. The ΔE value increased from 3.24 to 5.13 at pH 2-8, and the change was still prominent in acid-base alternating test, indicating a high response sensitivity. Notably, the yellow gamut of indicating terminus increased its visibility to the naked eye. The release behavior of CO from film was in line with Fick's diffusion. Meanwhile, the release of CO delayed to about 90 h through β-cyclodextrin encapsulation, showing a high growth-inhibition rate in E. coli and S. aureus of almost 100 %. In this study, a dual-function film with indication and bacteriostasis was prepared and enhanced with both, expanding its wide application in intelligent packaging of fresh food.

Preparation and characterization of polyvinyl alcohol/sodium lignosulfonate/black rice anthocyanin extract agricultural film for monitoring soil pH

This study focuses on the formulation of polyvinyl alcohol (PVA)-based films with pH-sensitive properties and ultraviolet (UV) resistance by incorporating sodium lignosulfonate (LS) and varying concentrations of black rice anthocyanin extract (BRE) into PVA matrix. The films were characterized through Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), tensile test, water vapor permeability (WVP), and ultraviolet-visible (UV-vis) spectroscopy. The results indicated that BRE and LS effectively formed strong hydrogen bonds with PVA, leading to reduced film crystallinity, improved mechanical properties, and lowered WVP as the BRE content increased. The addition of LS and BRE improved the UV resistance of the films, and BRE imparted films with excellent pH-sensitive properties. Among the film variants, the PVA/LS/BRE film containing 1 wt% BRE exhibited excellent mechanical performance, boasting an elongation at a break of 360.66 % and a strength of 35.68 MPa. Additionally, soil pH visualization holds significant potential within agriculture. In this study, the PVA/LS/BRE film containing 2 wt% BRE exhibited minimum UV transparency (0.9 %) and displayed the most distinct color response across varying pH environments. Therefore, the PVA/LS/BRE film containing 2 wt% BRE excelled in both UV resistance and pH sensitivity, positioning it as the most suitable material for the development of agricultural films integrated with soil pH monitoring capabilities.

Development of basil seed mucilage (a heteropolysaccharide) - Polyvinyl alcohol biopolymers incorporating zinc oxide nanoparticles

The effect of zinc oxide nanoparticles (ZnONPs) on various properties of basil seed mucilage (a heteropolysaccharide)-polyvinyl alcohol (BSM-PVA) films was investigated. Increasing concentration of ZnONPs in BSM-PVA films reduced moisture content (from 24.73 to 17.09 %), water solubility (from 36.36 to 27.65 %), water vapor permeability (from 4.66 × 10-7 to 2.55 × 10-7 g·m/m2·Pa·h), oxygen permeability (from 2.96 to 2.13 cm3 μm/m2 d kPa), and elongation at break (from 40.34 to 29.44 %), and increased ultimate tensile strength (from 16.81 to 21.48 MPa). Color and light transmission were affected by ZnONPs concentrations. The lack of formation of new peaks, along with the displacement of peaks, indicated the formation of hydrogen bonds between ZnONPs and the film matrix. Dynamic mechanical-thermal analysis showed that storage modulus and glass transition temperature increased with the concentration of ZnONPs. Scanning electron microscopy images illustrated that the addition of ZnONPs improved film integrity. X-ray diffraction pattern showed that the crystal shape of nanoparticles was preserved in the film matrix. Films containing ZnONPs showed good antibacterial activity against Staphylococcus aureus (reductions ≥ 3 log CFU/cm2) and Escherichia coli (reductions ≥ 4 log CFU/cm2). Films containing ZnONPs also showed a suitable antifungal activity during the storage of wheat bread.

Active colorimetric bilayer polycaprolactone-eucalyptus oil@silk fibroin-bayberry anthocyanins (PCL-EO@SF-BAs) membrane with directional water transport (DWT) for food packaging

Currently, designing smart membranes with multifunctional effectiveness is crucial to food freshness monitoring and retention. Herein, an active colorimetric Janus bilayer membrane with directional water transport (DWT) performance is constructed by electrospinning, which comprises a hydrophilic layer of silk fibroin-bayberry anthocyanins (SF-BAs) and a hydrophobic layer of polycaprolactone-eucalyptus oil (PCL-EO). The entities of BAs and EO are well dispersed in the fiber matrix by hydrogen bonds and physical interactions, respectively. BAs endow the membrane colorimetric response and antioxidant activity, and EO contributes to the antibacterial activity while DWT performance is generated from the asymmetric wettability of the two layers. The bilayer membrane has an accumulative one-way transport index of 1077%, an overall moisture management capacity of 0.76 and a water evaporation rate of 0.48 g h-1. Moreover, the release of BAs and EO was predominantly controlled by Fickian diffusion. As a pH-sensing indicator, PCL-EO@SF-BAs is highly sensitive to external pH stimuli and the response is reversible. In addition to freshness monitoring, PCL-EO@SF-BAs can extend the shelf-life of pork beyond 100% at 4 °C. Also, it can extend the shelf life of shrimp by approximately 70% at 25 °C with the synergistic effect of antibacterial activity and the DWT performance.

Intelligent double-layer polymers based on carboxymethyl cellulose-cellulose nanocrystals film and poly(lactic acid)-Viola odorata petal anthocyanins nanofibers to monitor food freshness

The present study was conducted with the aim of fabricating smart bilayer polymers based on carboxymethyl cellulose-cellulose nanocrystals film and poly(lactic acid)-Viola odorata extract nanofibers (CMC-CNC and PLA-VOE) for freshness monitoring of Pacific white shrimps, minced lamb meat, chicken fillets, and rainbow trout fillets, during refrigerated storage conditions. The fabricated indicators based on CMC-PLA-VOE 5%, CMC-CNC 1%-PLA-VOE 5%, and CMC-CNC 3%-PLA-VOE 5% presented remarkable color changes in pH 1-12 buffer solutions, including red at pH 1-6, violet at pH 7-8, green at pH 9-10, and brown at pH 11-12. Significantly lower water vapor permeability and oxygen transmission rate of prepared polymers were found in comparison with the control groups (P < 0.05). Regarding the monitoring of food samples in real-time, the samples spoiled after 3 days, evidenced by total viable count, psychrotrophic bacterial count, total volatile basic nitrogen, and pH values of 7.17-7.54 log CFU/g, 5.68-6.23 log CFU/g, 25.14-28.12 mg N/100 g, and 7.10-7.66, respectively. Meanwhile, the noticeable color change of prepared indicators from white to violet (day 3) and finally dark violet (day 7) was observed, indicating a potential application in intelligent packaging for real-time control of the freshness of perishable food samples.

Anthocyanin-loaded bacterial cellulose nanofiber as a green sensor for monitoring the selective naked eye and visual detection of Al(III) Ions

The present study developed a green metallochromic sensor that detects aluminium (Al(III)) ions in solution and solid state using anthocyanin extract from purple onion peels embedded in bacterial cellulose nanofibers (BCNFs). The CIE Lab colour parameters demonstrated that Al(III) binding causes a sensible change in colour. A variety of metal ions including K+, Mn2+, Cu2+, Hg2+, Cr2+, Pb2+ and Ni2+ were used to challenge the sensor to determine its selectivity. The findings demonstrated that the suggested sensor showed excellent selectivity toward Al(III) ion. Al(III) is quantitatively detected by the sensing method with detection limits in the range between 30-200 and 20-300 ppm in solution and solid state, respectively, and through observation with naked eye. The fabricated green metallochromic sensor is promising to be a simple, cheap, mobile and easily operable for real-time and on-site detection of Al(III) ions in food matrices.

Recent Advances in Functional Cellulose-based Films with Antimicrobial and Antioxidant Properties for Food Packaging

The packaging of food plays a crucial role in food preservation worldwide. However, traditional packaging systems are passive layers with weak efficiency in protecting the food quality. Therefore, packaged foods are gradually spoiled due to the oxidation and growth of microorganisms. Additionally, most of the commercial packaging films are made of petroleum-based materials which raise environmental concerns. Accordingly, the development of eco-friendly natural-derived active packaging systems has increased the attention of scientists. Cellulose as the most abundant polysaccharide on earth with high biocompatibility, no toxicity, and high biodegradability has extensively been applied for the fabrication of packaging films. However, neat cellulose-based films lack antioxidant and antimicrobial activities. Therefore, neat cellulose-based films are passive films with weak food preservation performance. Active films have been developed by incorporating antioxidants and antimicrobial agents into the films. In this review, we have explored the latest research on the fabrication of antimicrobial/antioxidant cellulose-based active packaging films by incorporating natural extracts, natural polyphenols, nanoparticles, and microparticles into the cellulose-based film formulations. We categorized these types of packaging films into two main groups: (i) blend films which are obtained by mixing solutions of cellulose with other soluble antimicrobial/antioxidant agents such as natural extracts and polyphenols; and (ii) composite films which are fabricated by dispersing antimicrobial/antioxidant nano- or microfillers into the cellulose solution. The effect of these additives on the antioxidant and antimicrobial properties of the films has been explained. Additionally, the changes in the other properties of the films such as hydrophilicity, water evaporation rate, and mechanical properties have also been briefly addressed.

A comprehensive review of the spoilage of shrimp and advances in various indicators/sensors for shrimp spoilage monitoring

Shrimp is a popular internationally traded shellfish due to its unique taste, texture, and nutritional value. Shrimp is highly perishable because it has enough free amino acids, high moisture levels, non-nitrogenous compounds used for microbial growth, and melanosis. Shrimp spoilage after death is caused by various reasons, like autolysis (endogenous proteinases actions during shrimp storage), growth of spoilage microorganisms, ATP degradation, melanin formation, and lipid peroxidation. A microbial byproduct, total volatile basic nitrogen, is one of the major reasons for the generation of foul odors from shrimp spoilage. Shrimp freshness monitoring is crucial for market sellers and exporters. Traditional methods for estimating shrimp freshness are expensive and inaccessible to the general public. Sensors are rapid, sensitive, selective, and portable food toxins' detection tools, devoid of expensive instruments, skilled people, sample pretreatment, and a long detection time. This review addresses shrimp spoilage causes. The mechanisms of different stages of shrimp spoilage after death, like rigor mortis, dissolution of rigor mortis, autolysis, and microbial spoilage mechanisms, are discussed. This review highlights the last five years' advances in shrimp freshness detection sensors and indicators like colorimetric pH indicators, fluorescence sensors, electronic noses, and biosensors, their working principles, and their sensitivities. Commercially available indicators and sensors for shrimp spoilage monitoring are also discussed. A review highlighting the applications of the different sensors and indicators for monitoring shrimp freshness is unavailable to date. Challenges and future perspectives in this field are explained at the end.

Simultaneously realizing enhancement of sensitivity for freshness monitoring and multinomial properties of carrageenan/konjac glucomannan/blueberry anthocyanin-based intelligent film by diatomite

Here, highly sensitive blueberry anthocyanin (BBA)-induced intelligent indicating films were fabricated by incorporating a novel composite ingredient, diatomite (DA), into a matrix of konjac glucomannan (KGM), carrageenan (CAR) and BBA. We systematically investigated the effects of introducing DA and BBA on the structure, physical properties, colorimetric response, and practical application of the KGM/CAR film. Our findings revealed that the DA particles and BBA were well-distributed in the KGM/CAR matrix through hydrogen bonding interactions. This distribution significantly improved tensile strength, surface hydrophobicity, thermal stability, and barrier properties of the KGM/CAR film. Notably, the KGM/CAR-based intelligent film loaded with 6 % DA exhibited the most optimal properties. Furthermore, DA exhibited a hierarchical porous structure, enabling the KGM/CAR film to detect volatile amines with heightened sensitivity. When applied to monitor shrimp spoilage in transparent plastic packaging, the color of the composite film underwent remarkable changes from bright pink to bluish violet. These color changes correlated well with the total volatile basic nitrogen (TVB-N) and pH changes in the shrimp, as determined by standard laboratory procedures. Our work presents a promising approach to the development of high-performance and intelligent food packaging materials. These materials hold great potential for practical applications in the field of food packaging.

Exopolysaccharide riclin and anthocyanin-based composite colorimetric indicator film for food freshness monitoring

Food freshness monitoring is vital to ensure food safety. Recently, packaging materials incorporating pH-sensitive films have been employed to monitor the freshness of food products in real time. The film-forming matrix of the pH-sensitive film is essential to maintain the desired physicochemical functions of the packaging. Conventional film-forming matrices, such as polyvinyl alcohol (PVA), have drawbacks of low water resistance, poor mechanical properties, and weak antioxidant ability. In this study, we successfully synthesise PVA/riclin (P/R) biodegradable polymer films to overcome these limitations. The films feature riclin, an agrobacterium-derived exopolysaccharide. The uniformly dispersed riclin conferred outstanding antioxidant activity to the PVA film and significantly improved its tensile strength and barrier properties by forming hydrogen bonds. Purple sweet potato anthocyanin (PSPA) was used as a pH indicator. The intelligent film with added PSPA provided robust surveillance of volatile ammonia and changed its color within 30 s in the pH range of 2-12. This multifunctional colorimetric film also engendered discernible color changes when the quality of shrimp deteriorated, demonstrating its great potential as an intelligent packaging material to monitor food freshness.

Application of biodegradable colorimetric films based on purple tomatoes anthocyanins loaded chitosan and polyvinyl alcohol in pork meat

A series of biodegradable colorimetric films were prepared by using chitosan and polyvinyl alcohol as matrix, in which, the weight ratio of chitosan: Polyvinyl alcohol was 100: 0, 80: 20, 50: 50, 20: 80, or 0: 100, with addition of 10% (w/w, relative to chitosan) anthocyanins extracted from purple tomatoes (purple tomatoes anthocyanin) as pigment. The aim of this study was to observe the effect of weight ratio (chitosan: Polyvinyl alcohol) on the mechanical properties, contact angle, swelling rate, pH sensitivity, antioxidant properties of chitosan-polyvinyl alcohol/purple tomatoes anthocyanins films, and the antibacterial activity of films produced for pork packaging. In addition, the films as a smart colorimetric indicator for monitoring the freshness of pork was investigated. The results showed that as the ratio of chitosan to polyvinyl alcohol decreases, the elongation at break, hydrophilicity, and swelling rate of the films increased especially from 16.5% to 174.2% for elongation at break and 93.0° to 53.8° for water contact angle, however, the tensile strength decreased from 67.3 to 24.7 MPa. With decreasing of chitosan: Polyvinyl alcohol, the antibacterial activity on pork was decreased, and the antioxidant properties of films increased first then decreased. Fourier transform infrared spectroscopy indicated there were interactions among chitosan, polyvinyl alcohol, and purple tomatoes anthocyanins. The color response of films was depended on pH, as well as the immersion time. The longer immersion resulted in a more pronounced color change. The color changed from purplish red (pH 2-4) to green (pH 5-10) to yellow (pH 10-12). In monitoring the freshness of pork, the film showed a nice visual color change, indicating a potential application in smart packaging. These bio-based materials may be useful alternatives to synthetic plastics for food applications such as active and smart packaging, thereby improving the environmental friendliness and sustainability of the food supply.

New Polyvinyl Alcohol/Succinoglycan-Based Hydrogels for pH-Responsive Drug Delivery

We fabricated new hydrogels using polyvinyl alcohol (PVA) and succinoglycan (SG) directly isolated and obtained from Sinorhizobium meliloti Rm 1021 via the freeze-thaw method. Both the composition of the hydrogels and the freeze-thaw cycles were optimized to maximize the swelling ratio for the preparation of the PVA/SG hydrogels. During the optimization process, the morphology and conformational change in the hydrogel were analyzed by scanning electron microscopy, rheological measurements, and compressive tests. An optimized hydrogel with a maximum swelling ratio of 17.28 g/g was obtained when the composition of PVA to SG was 50:50 (PVA/SG 50/50) and the total number of freeze-thaw cycles was five. The PVA/SG 50/50 hydrogel had the largest pore with 51.24% porosity and the highest cross-over point (28.17%) between the storage modulus (G') and the loss modulus (G″). The PVA/SG 50/50 hydrogel showed improved thermal stability owing to its interaction with thermally stable SG chains. The improvement in the thermal stability was confirmed by thermogravimetric analysis and differential scanning calorimetry. In addition, the PVA/SG 50/50 hydrogel showed differential drug release according to the corresponding pH under acidic conditions of pH 1.2 and slightly basic conditions of pH 7.4. Furthermore, the cell viability test on the HEK-293 cell line for that hydrogel demonstrated that the PVA/SG 50/50 hydrogel was non-toxic and biocompatible. Therefore, this hydrogel could be a potential scaffold capable of pH-responsive drug delivery for chronic wound dressing applications.

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.

Interaction of preheated whey protein isolate with rose anthocyanin extracts in beverage model system: Influence on color stability, astringency and mechanism

Preheating proteins have the potential to improve anthocyanin stability. Our aim was to investigate the effect of preheated whey protein isolate (WPI) on the color stability and astringency of the beverage model system in the presence of rose anthocyanin extracts (RAEs), and to explore the mechanism of interaction between preheated WPI and RAEs. The secondary structure, particle size and transparency of WPI were obviously changed by preheating. WPI preheated at 100°C  (WPI100) could effectively improve the color stability of RAEs in the beverage model system. Importantly, the WPI100-RAEs in the beverage model system exhibited the smallest particle size and the weakest astringency effect. In addition, different preheated WPIs could interact with RAEs non-covalently, and the interaction forces are hydrogen bonding and van der Waals forces, among which WPI100 had the strongest binding ability to RAEs. These results will provide a new insight into the development of protein-anthocyanin beverages.

Preparation and characterization of a novel absorbent pad based on polyvinyl alcohol/gellan gum/citric acid with incorporated Perilla leaf oil nanoemulsion for chilled chicken packaging

A novel absorbent pad based on polyvinyl alcohol (PVA)/gellan gum/citric acid (CA) composite with incorporated Perilla leaf oil (PO) nanoemulsion was prepared and characterized. The esterification between PVA and CA and strong hydrogen bonds were detected. The PVA improved the tensile strength and elongation at break by 110% and 73%, respectively, whereas PO concentration ≤ 1.5 % (w/v) had little effect on the material properties. The CA and PO nanoemulsion loaded in the pads showed good antioxidant activity, and the pads with PO concentration ≥ 1.5 % (w/v) had effective antimicrobial activity against Escherichia coli and Staphylococcus aureus. The results of chilled chicken storage experiments indicated that the pad with 1.5% (w/v) PO nanoemulsion extended the shelf life of chicken to at least 9 days, demonstrating that the developed absorbent pads are potential materials for chilled chicken storage packing.

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.

Ixiolirion tataricum mucilage/chitosan based antioxidant films activated by free and nanoliposomal fennel essential oil

Ixiolirion tataricum mucilage (ITM) was characterized and applied in fabrication of ITM/chitosan (CH) blend films activated by Foeniculum vulgare essential oil (FEO) in free and nanoliposomal forms. Uniform smooth surface structure, viscoelastic solid-like behavior and Newtonian nature of ITM were confirmed by morphological and rheological analyses. The prepared FEO nanoliposomes (FEO-NLPs) showed desirable properties in terms of particle size (57.2 nm), polydispersity index (0.243), zeta-potential (-17.6 mV), and encapsulation efficiency (85.2 %). The enhancing effects of FEO-NLPs and the adverse effects of free FEO on the crystalline, morphological and structural properties of films were confirmed by XRD, FE-SEM and ATR-FTIR tests. FEO-NLPs loaded films had better mechanical, thermal, water and gas barrier and antioxidant properties than neat film. Analysis also indicated the high controlled release of FEO from the films containing the nanoliposomal form of FEO. The films containing free FEO showed higher antibacterial activity against E. coli and S. aureus in comparison with FEO-NLPs loaded ones. The results showed the potential of FEO-NLPs loaded ITM/CH films for antioxidant food packaging applications.