Active-intelligent film based on pectin from watermelon peel containing beetroot extract to monitor the freshness of packaged chilled beef

Blueberry anthocyanin based active intelligent wheat gluten protein films: Preparation, characterization, and applications for shrimp freshness monitoring

The aim of this study was to prepare active intelligent gluten protein films using wheat gluten protein (WG) and apple pectin (AP) as film-forming matrices, and blueberry anthocyanin extract (BAE) as a natural indicator. SEM and FT-IR analyses demonstrated the successful immobilization of BAE in the film matrix by hydrogen bonding interactions and its compatibility with WG and AP. The resultant WG-AP/BAE indicator films demonstrated notable antioxidant activity, color stability, barrier qualities, pH and ammonia response sensitivity, and mechanical properties. Among them, WG-AP/BAE5 exhibited the best mechanical properties (TS: 0.83 MPa and EB: 242.23%) as well as the lowest WVP (3.92 × 10-8 g.m/m2.Pa.s), and displayed high sensitivity to volatile ammonia. In addition, WG-AP/BAE5 showed a color shift from purplish red to green to yellowish green, demonstrating the monitoring of shrimp freshness in real time. Consequently, this study offers a firm scientific foundation for the development of active intelligent gluten protein films and their use in food freshness assessments.

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 amine-sensitive intelligent film with MIL-100(Fe) as function filler based on anthocyanins/pectin for monitoring chilled meat freshness

To enhance the amine-sensitivity of intelligent films for accurate monitoring of chilled meat freshness, different additions (0, 1, 2, 3 wt%) of MIL-100(Fe) were incorporated into the matrix composed of anthocyanins (ANs) and pectin (P). Results indicated that the tensile strength, thermal stability, barrier performance and absorption capacity of the films with MIL-100(Fe) were improved significantly (p < 0.05). Especially, the film with 2 % MIL-100(Fe) exhibited the best performance due to its compact structure and the highest crystallinity. Additionally, adsorption isotherms of the films with MIL-100(Fe) were fitted on the Langmuir and the Freundlich isotherm, and adsorption kinetics were fitted on the pseudo-second-order model and Elovich model, respectively (R2 > 0.96), suggesting a combined mechanism of chemisorption and intraparticle diffusion. Besides, when the films were exposed in ammonia environment, they changed color from purple to blue-violet, finally to green. Ultimately, film with 2 % MIL-100(Fe) was used to monitor the chilled meat freshness, as expected, similar color variation was observed at three stages of meat freshness (fresh, sub-fresh, and spoiled), which enabled the accurate differentiation of meat freshness. Thus, films with MIL-100(Fe) demonstrated the potential to be amine-sensitive intelligent packaging for monitoring chilled meat freshness in real time.

Monitor the freshness of shrimp by smart halochromic films based on gelatin/pectin loaded with pistachio peel anthocyanin nanoemulsion

This paper focuses on the combination of gelatin (Gel), pectin (Pec), and Pistachio peel anthocyanins (PSAs) to develop a halochromic film for food applications (shrimp). The results of spectroscopic properties showed that the film components had proper interaction and compatibility. Furthermore, the addition of PSAs and Pec improved the thermal stability of films. The addition of Pec and PSAs significantly improved the physical properties and mechanical resistance of the films. So that, the permeability to water vapor and oxygen reduced from 2.81 to 2.74 (g‧s-1‧Pa-1‧m-1) and 5.25 to 4.70 (meq/kgO2), respectively. In addition, the strength and flexibility of halochromic film reached 0.7 MPa and 56 % compared to Gel film (0.62 MPa, and 46.96 %). Most importantly, the color changes of the smart film from cherry/pink to yellow/brown, which were proportional to the color changes of the anthocyanin solution at different pHs, were able to monitor the shrimp freshness and spoilage at room (20 °C) and refrigerated (4 °C) temperature for 14 days.

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.

A Colorimetric Nanofiber Film Based on Ethyl Cellulose/Gelatin/Purple Sweet Potato Anthocyanins for Monitoring Pork Freshness

In this study, colorimetric indicator nanofiber films based on ethyl cellulose (EC)/gelatin (G) incorporating purple sweet potato anthocyanins (PSPAs) were designed via electrospinning technology for monitoring and maintaining the freshness of pork. The film presented good structural integrity and stability in a humid environment with water vapor permeability (WVP) of 6.07 ± 0.14 × 10-11 g·m-1s-1Pa-1 and water contact angle (WCA) of 81.62 ± 1.43°. When PSPAs were added into the nanofiber films, the antioxidant capacity was significantly improved (p < 0.05) with a DPPH radical scavenging rate of 68.61 ± 1.80%. The nanofiber films showed distinguishable color changes as pH changes and was highly sensitive to volatile ammonia than that of casting films. In the application test, the film color changed from light pink (fresh stage) to light brown (secondary freshness stage) and then to brownish green (spoilage stage), indicating that the nanofiber films can be used to detect the real-time freshness of pork during storage. Meanwhile, it could prolong the shelf life of pork by inhibiting the oxidation degree. Hence, these results suggested that the EC/G/PSPA film has promising future for monitoring freshness and extending shelf life of pork.

Fabrication of ammonia and acetic acid-responsive intelligent films based on grape skin anthocyanin via adjusting the pH of film-forming solution

pH-responsive intelligent films for food freshness monitoring have attracted great attentions recently. In this study, several intelligent films based on chitosan (CS), polyvinyl alcohol (PVA), and grape skin anthocyanin (GSA) were prepared, and the effect of film-forming solution pH on the properties of intelligent films was investigated. The results of SEM, FTIR, XRD and TGA displayed that the hydrogen bond between CS and GSA was strong at strong acidic conditions (2.0-2.5), and it weakened at weak acidic conditions (3.0-4.5). Meanwhile, the hydrogen bond between PVA and GSA was negligible under strong acidic conditions, and it appeared under weak acidic conditions. Consequently, the films fabricated under weak acidic conditions displayed lower water solubility, lower water vapor permeability, and higher elongation at break. The tensile strength of films increased firstly and subsequently decreased with pH increasing, reaching a maximum value of 31.44 MPa at pH 3.5. Additionally, the films prepared at pH 2.5 and 4.0 showed the best color responsiveness to ammonia and acetic acid, respectively. Overall, the intelligent films prepared under variant pH have the potential to realize the goal of monitoring the freshness of different types of food, thereby expanding the application subject of anthocyanins-based intelligent films.

Biodegradable cellulose/curcumin films with Janus structure for food packaging and freshness monitoring

The development of renewable, hydrophobic, and biodegradable intelligent packaging materials as an alternative to petroleum-based plastic products has become a new research focus in recent years, but remains a challenge. Herein, regenerated cellulose/curcumin composite films were fabricated by dispersing hydrophobic curcumin uniformly in a hydrophilic cellulose matrix using an aqueous alkali/urea solvent based on the pH-driven principle of curcumin. In addition, a unilateral hydrophobic modification was carried out using chemical vapor deposition of methyltrichlorosilane to obtain Janus structure. The composite films exhibited high transparency in the visible light spectrum, excellent antioxidation, thermal stability, mechanical strength, gas barrier properties, and antibacterial activity. Furthermore, the films demonstrated the capability to lower the overall levels of volatile basic nitrogen in stored fish. The color of the films shifted from a pale yellow to a reddish-brown over time during storage. The composite films can be completely degraded after approximately 98 days in soil with an average environmental temperature of 29 °C. This work provided a facile strategy to prepare biodegradable cellulose/curcumin films with Janus structure as packaging materials which could preserve the freshness of food products while offering visual monitor of their freshness in real-time.

Antioxidant Edible Films Based on Pear Juice and Pregelatinized Cassava Starch: Effect of the Carbohydrate Profile at Different Degrees of Pear Ripeness

Edible films based on fruit and vegetable purees combined with different food-grade biopolymeric binding agents (e.g., pectin, gelatin, starch, sodium alginate) are recognized as interesting packaging materials that benefit from the physical, mechanical, and barrier properties of biopolymers as well as the sensory and nutritional properties of purees. In the current contribution, edible antioxidant films based on pear juice and pregelatinized cassava starch were developed. In particular, the suitability of using pregelatinized cassava starch for the non-thermal production of these novel edible films was evaluated. In addition, the effects on the films' properties derived from the use of pear juice instead of the complete puree, from the content of juice used, and from the carbohydrate composition associated with the ripening of pears were all studied. The produced films were characterized in terms of their total polyphenol content, water sensitivity, and water barrier, optical, mechanical and antioxidant properties. Results showed that the use of pear juice leads to films with enhanced transparency compared with puree-based films, and that juice concentration and carbohydrate composition associated with the degree of fruit ripeness strongly govern the films' properties. Furthermore, the addition of pregelatinized cassava starch at room temperature discloses a significant and favorable impact on the cohesiveness, lightness, water resistance, and adhesiveness of the pear-juice-based films, which is mainly attributed to the effective interactions established between the starch macromolecules and the juice components.

Recent advances on natural colorants-based intelligent colorimetric food freshness indicators: fabrication, multifunctional applications and optimization strategies

With the increasing concerns of food safety and public health, tremendous efforts have been concentrated on the development of effective, reliable, nondestructive methods to evaluate the freshness level of different kinds of food. Natural colorants-based intelligent colorimetric indicators which are typically constructed with natural colorants and polymer matrices has been regarded as an innovative approach to notify the customers and retailers of the food quality during the storage and transportation procedure in real-time. This review briefly elucidates the mechanism of natural colorants used for intelligent colorimetric indicators and fabrication methodologies of natural colorants-based food freshness indicators. Subsequently, their multifunctional applications in intelligent food packaging systems like antioxidant packaging, antimicrobial packaging, biodegradable packaging, UV-blocking packaging and inkless packaging are well introduced. This paper also summarizes several optimizing strategies for the practical application of this advanced technology from different perspectives. Strategies like adopting a hydrophobic matrix, constructing double-layer film and encapsulation have been developed to improve the stability of the indicators. Co-pigmentation, metal ion complexation, pigment-mixing and using substrates with high surface area are proved to be effective to enhance the sensitivity of the indicators. Approaches include multi-index evaluation, machine learning and smartphone-assisted evaluation have been proven to improve the accuracy of the intelligent food freshness indicators. Finally, future research opportunities and challenges are proposed. Based on the fundamental understanding of natural colorants-based intelligent colorimetric food freshness indicators, and the latest research and findings from literature, this review article will help to develop better, lower cost and more reliable food freshness evaluation technique for modern food industry.

Development of a multifunctional food packaging for meat products by incorporating carboxylated cellulose nanocrystal and beetroot extract into sodium alginate films

Consumers' pursuit for safe meat products is challenging to develop smart food packaging with proper mechanical properties and multifunctional properties. Therefore, this work attempted to introduce carboxylated cellulose nanocrystal (C-CNC) and beetroot extract (BTE) into sodium alginate (SA) matrix films to enhance their mechanical properties and endow them with antioxidant properties and pH-responsive capacity. The rheological results showed the C-CNC and BTE were consistently dispersed in the SA matrix. The incorporation of C-CNC made the surface and cross-section of the films rough but still dense, thus significantly improving the mechanical properties of the films. The integration of BTE provided antioxidant properties and pH responsiveness without significantly changing the thermal stability of the film. The highest tensile strength (55.74 ± 4.52 MPa) and strongest antioxidant capacities were achieved for the SA-based film with BTE and 10 wt% C-CNC. Additionally, the films possessed higher UV-light barrier properties after incorporating BTE and C-CNC. More notably, the pH-responsive films discolored when TVB-N value exceeded 18.0 mg/100 g during storage of pork at 4 °C and 20 °C, respectively. Therefore, the SA-based film with enhanced mechanical and functional properties has a high potential for quality detection in smart food packaging applications.

Preparation, Characterization, and Application of pH-Response Color-Changeable Films Based on Pullulan, Cooked Amaranth (Amaranthus tricolor L.) Juice, and Bergamot Essential Oil

Pullulan-based smart packaging films were prepared by mixing cooked amaranth juice and bergamot essential oil. The impact of cooked amaranth juice and bergamot essential oil on the color-changeability, structural characterization, and barrier, antioxidant, mechanical and thermal properties of pullulan-based films was determined. Results showed the cooked amaranth juice contained pH-response color-changing betacyanins. The pullulan films containing cooked amaranth juice were color-changeable in pH 9-12 buffers and in ammonia vapor. The color-changeable property of betacyanins in cooked amaranth juice was unaffected by bergamot essential oils. The inner structure of pullulan films was greatly affected by cooked amaranth juice, forming big and ordered humps in film cross-sections. The crystallinity of pullulan films was improved by the combined addition of cooked amaranth juice and bergamot essential oil. Among the films, the pullulan film containing cooked amaranth juice and 6% bergamot essential oil showed the highest UV-vis light barrier property, antioxidant activity, and tensile strength; while the pullulan film containing cooked amaranth juice and 4% bergamot essential oil showed the highest oxygen barrier property and thermal stability. Moreover, the pullulan films containing cooked amaranth juice were able to monitor the freshness of shrimp by presenting color changes from reddish purple to dark red.

Betalains as promising natural colorants in smart/active food packaging

Betalains are water-soluble nitrogen pigments with beneficial effects, including antioxidant, antimicrobial, and pH-indicator properties. The development of packaging films incorporated with betalains has received increasing attention because of pH-responsive color-changing properties in the colorimetric indicators and smart packaging films. As such, intelligent and active packaging systems based on biodegradable polymers containing betalains have been recently developed as eco-friendly packaging to enhance the quality and safety of food products. Betalains could generally improve the functional properties of packaging films, such as higher water resistance, tensile strength, elongation at break, and antioxidant and antimicrobial activities. These effects are dependent on betalain composition (about its source and extraction), content, and the kind of biopolymer, film preparation method, food samples, and storage time. This review focused on betalains-rich films as pH- and ammonia-sensitive indicators and their applications as smart packaging to monitor the freshness of protein-rich foods such as shrimp, fish, chicken, and milk.

Highly biologically active and pH-sensitive collagen hydrolysate-chitosan film loaded with red cabbage extracts realizing dynamic visualization and preservation of shrimp freshness

Accurate and efficient detection of food freshness is of great significance to guarantee food safety. Herein, pH sensitive colorimetric films with considerable biological activities have been prepared by combining red cabbage anthocyanin extracts (RCE) with collagen hydrolysate-chitosan (CH-CS) matrix film. The formation mechanism of CH-CS-RCE films was discussed by SEM, FT-IR and XRD, which showed that RCE was successfully fixed in CH-CS film through hydrogen bonding and electrostatic interaction. The CH-CS-RCE films exhibited good mechanical properties, high barrier ability, excellent thermal stability, significant antioxidant and antimicrobial activity, and especially sensitive response to pH and ammonia. Fickian diffusion was the main mechanism for the release of RCE from CH-CS-RCE films and such release mechanism facilitated the maintenance of functional features of films. During the storage of shrimps at 4 °C, CH-CS-RCE2% showed a remarkable preservation effect on shrimps, and their shelf life was prolonged from 2 d to 5 d. Furthermore, CH-CS-RCE2% provided a dynamic visual color switching to detect the freshness of shrimp, realizing real-time monitoring of freshness. Color information (RGB) extracted via smartphone APP was used to enhance the accuracy and universality of freshness indication. Thus, this multifunctional film has great potential in food preservation and freshness monitoring.

Recent progress in pectin extraction, characterization, and pectin-based films for active food packaging applications: A review

Pectin is an abundant complex polysaccharide obtained from various plants. Safe, biodegradable, and edible pectin has been extensively utilized in the food industry as a gelling agent, thickener, and colloid stabilizer. Pectin can be extracted in a variety of ways, thus affecting its structure and properties. Pectin's excellent physicochemical properties make it suitable for many applications, including food packaging. Recently, pectin has been spotlighted as a promising biomaterial for manufacturing bio-based sustainable packaging films and coatings. Functional pectin-based composite films and coatings are useful for active food packaging applications. This review discusses pectin and its use in active food packaging applications. First, basic information and characteristics of pectin, such as the source, extraction method, and structural characteristics, were described. Then, various methods of pectin modification were discussed, and the following section briefly described pectin's physicochemical properties and applications in the food sector. Finally, the recent development of pectin-based food packaging films and coatings and their use in food packaging were comprehensively discussed.

Development and characterization of tapioca starch/pectin composite films incorporated with broccoli leaf polyphenols and the improvement of quality during the chilled mutton storage

This study aimed at the composition of active packaging film from tapioca starch/pectin (TSP) incorporated with broccoli leaf polyphenols (BLP) was prepared and applied to improve the qualities of the chilled mutton during storage. The results indicated the addition of BLP significantly improved the thickness, density, barrier ability, mechanical properties, water solubility and antioxidant activity of the composite films while inducing decreases in the brightness (p < 0.05), enhancing inter-molecular interactions of TSP + BLP composite films. The WVP, oxygen permeability and elongation at break of the composite film reached the minimum when BLP concentration was 3 % while exhibiting the highest tensile strength and the best performance. This composite film delayed microbial growth and minimized oxidative rancidity during chilled mutton storage, causing the improvement of its quality and extending its shelf life to 12 days. Therefore, TSP + BLP composite films possessed the promise to be applied as bioactive materials in food packaging sectors.

Active film preparation using pectin and polyphenols of watermelon peel and its applications for super-chilled storage of chilled mutton

We investigated the effect of active packaging films prepared by pectin (WMP) and polyphenols (WME) obtained from watermelon peel on the quality of chilled mutton during super-chilled storage. The addition of WME created new chemical and hydrogen bonds in film. Furthermore, an appropriate amount of WME (≤1.5%) was evenly distributed throughout the film matrix, improving barrier properties, mechanical properties, thermal stability, and light transmittance of the film. An assessment of the meat quality showed that the pH, L*, b*, thiobarbituric acid reactive substances (TBARs), total volatile basic nitrogen (TVB-N), and total bacterial count (TCA) of super-chilled + film group were significantly lower, whereas shear force and a* value were significantly higher (P < 0.05) than other groups. The WMP/WME film has dense microstructure and excellent mechanical properties after storage. Pectin and polyphenols obtained from watermelon peel have good potential as a novel packaging material for chilled mutton during super-chilled storage.

Recent progress in pectin extraction and their applications in developing films and coatings for sustainable food packaging: A review

Perishable foods like fruits and vegetables, meat, fish, and dairy products have short shelf-life that causes significant postharvest losses, which poses a major challenge for food supply chains. Biopolymers have been extensively studied as sustainable alternatives to synthetic plastics, and pectin is one such biopolymer that has been used for packaging and preservation of foods. Pectin is obtained from abundantly available low-cost sources such as agricultural or food processing wastes and by products. This review is a complete account of pectin extraction from agro-wastes, development of pectin-based composite films and coatings, their characterizations, and their applications in food packaging and preservation. Compared to conventional chemical extraction, supercritical water, ultrasound, and microwave assisted extractions are a few examples of modern and more efficient pectin extraction processes that generate almost no hazardous effluents, and thus, such extraction techniques are more environment friendly. Pectin-based films and coatings can be functionalized with natural active agents such as essential oils and other phytochemicals to improve their moisture barrier, antimicrobial and antioxidant properties. Application of pectin-based active films and coatings effectively improved shelf-life of fresh cut-fruits, vegetables, meat, fish, poultry, milk, and other food perishable products.

Developing strong and tough cellulose acetate/ZIF67 intelligent active films for shrimp freshness monitoring

There is a growing demand for the development of intelligent active packaging films to maintain and monitor the freshness of meat food. Herein, nano Co-based MOF (ZIF67) with ammonia-sensitive and antimicrobial functions was successfully synthesized and then integrated into cellulose acetate (CA) matrix to prepare intelligent active films. The impacts of ZIF67 incorporation on the structure, physical and functional characteristics of CA film were fully investigated. The results demonstrated that the ZIF67 nanofillers were evenly dispersed in CA matrix, resulting in remarkable improvement on tensile strength, toughness, thermal stability, UV barrier, hydrophobicity and water vapor barrier ability of CA film. Furthermore, the prepared CA/ZIF67 films exhibited superb antimicrobial and ammonia-sensitive functions. The CA/ZIF67 intelligent films turned their color from blue at beginning to brown during progressive spoilage of shrimp. These results revealed that the CA/ZIF67 films with excellent antimicrobial and ammonia-sensitive functions could be applied in intelligent active food packaging.

Development of active packaging with chitosan, guar gum and watermelon rind extract: Characterization, application and performance improvement mechanism

The objective of this study was to make a film matrix containing chitosan (CS) and guar gum (GG), and to improve the physicochemical properties of the film using watermelon rind extract (WRE) as a cross-linker and active substance for the preservation of fresh-cut bananas. The results of Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy showed that the WRE and CG matrix formed intermolecular hydrogen bond interactions, which made the structure of the resulting films more compact. With increasing amounts of WRE, the mechanical properties of the films were significantly increased, but the permeability of water vapor and oxygen was significantly decreased (p < 0.05). Notably, when the amount of extract reached 4 wt%, the DPPH radical scavenging activity of the composite film significantly increased to 83.24 %, and the antibacterial activity also reached its highest value. Fresh-cut bananas were stored at room temperature with polyethylene film, CG and CG-WRE. The CG with 4 wt% WRE effectively inhibited the changes in appearance, firmness, weight, color and total soluble solids content of fresh-cut bananas during storage. Therefore, CG-WRE as a novel active food packaging material, has good physicochemical properties and great potential to extend the shelf life of foods.

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

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

Colorimetric Sensor Based on Ag-Fe NTs for H2S Sensing

Meat waste is widely associated with spoilage caused by microbial growth and metabolism. Volatile compounds produced by microbial growth such as volatile sulfides could directly indicate the freshness of meat during distribution and storage. Herein, silver-iron nanotriangles (Ag-Fe NTs) for hydrogen sulfide (H₂S) detection were developed via one-pot facile reflux reactions. The Ag-Fe NTs were integrated into food packaging systems for the rapid, real-time, and nondestructive detection of the freshness of chilled broiler poultry. The principle of color development is that an increase in the volatile sulfide content leads to a change in the absorption wavelength caused by the etching of the Ag-Fe NTs, resulting in a color change (yellow to brown). The minimum H₂S concentrations detected by the naked eye and UV-vis spectrophotometer were 4 and 2 mg/m³, respectively. This label is economical and practical and can monitor the spoilage of chilled broiler meat products in real-time.

Novel Active Food Packaging Films Based on Gelatin-Sodium Alginate Containing Beetroot Peel Extract

Currently, the exploration of natural colorants from vegetal waste has gained particular attention. Furthermore, incorporation of these natural sources into biopolymers is an encouraging environmentally friendly approach to establishing active films with biological activities for food packaging. The present study developed bioactive antioxidant films based on gelatin-sodium alginate (NaAlg) incorporated with aqueous beetroot peel extract (BPE). Firstly, the effects of combining gelatin-NaAlg and BPE at 0.25, 0.5, and 1% on the mechanical, physical, antioxidant, and antibacterial properties of the films were analyzed. With increasing BPE, mechanico-physical properties and antioxidant and anti-foodborne pathogen capacities were enhanced. Likewise, when added to gelatin-NaAlg films, BPE remarkably increased the instrumental color properties. Moreover, during 14 days of storage at 4 °C, the impact of gelatin-NaAlg coating impregnated with BPE on microbial and chemical oxidation and on the sensory characteristics of beef meat samples was periodically assessed. Interestingly, by the end of the storage, BPE at 1% limited the microbial deterioration, enhanced the instrumental color, delayed chemical oxidation, and improved sensory traits. By practicing chemometrics tools (principal component analysis and heat maps), all data provided valuable information for categorizing all samples regarding microbiological and oxidative properties, sensory features, and instrumental color. Our findings revealed the ability of gelatin-NaAlg with BPE as an antioxidant to be employed as food packaging for meat preservation.

Encapsulation of Bioactive Compounds for Food and Agricultural Applications

This review presents an updated scenario of findings and evolutions of encapsulation of bioactive compounds for food and agricultural applications. Many polymers have been reported as encapsulated agents, such as sodium alginate, gum Arabic, chitosan, cellulose and carboxymethylcellulose, pectin, Shellac, xanthan gum, zein, pullulan, maltodextrin, whey protein, galactomannan, modified starch, polycaprolactone, and sodium caseinate. The main encapsulation methods investigated in the study include both physical and chemical ones, such as freeze-drying, spray-drying, extrusion, coacervation, complexation, and supercritical anti-solvent drying. Consequently, in the food area, bioactive peptides, vitamins, essential oils, caffeine, plant extracts, fatty acids, flavonoids, carotenoids, and terpenes are the main compounds encapsulated. In the agricultural area, essential oils, lipids, phytotoxins, medicines, vaccines, hemoglobin, and microbial metabolites are the main compounds encapsulated. Most scientific investigations have one or more objectives, such as to improve the stability of formulated systems, increase the release time, retain and protect active properties, reduce lipid oxidation, maintain organoleptic properties, and present bioactivities even in extreme thermal, radiation, and pH conditions. Considering the increasing worldwide interest for biomolecules in modern and sustainable agriculture, encapsulation can be efficient for the formulation of biofungicides, biopesticides, bioherbicides, and biofertilizers. With this review, it is inferred that the current scenario indicates evolutions in the production methods by increasing the scales and the techno-economic feasibilities. The Technology Readiness Level (TRL) for most of the encapsulation methods is going beyond TRL 6, in which the knowledge gathered allows for having a functional prototype or a representative model of the encapsulation technologies presented in this review.

Development and characterization of a novel active and intelligent film based on pectin and betacyanins from peel waste of pitaya (Hylocereus undatus)

In the present study, peel waste of pitaya (Hylocereus spp.) was used to develop a novel active and functional film. The film was developed with a combination of the white-fleshed pitaya peel pectin (WPPP) as a biopolymer and white-fleshed pitaya peel betacyanins (WPPB) as an active constituent, respectively. Furthermore, montmorillonite (MMT), a cheap and environmental-friendly silicate material, was introduced into film matrix as a filler to reduce the moisture sensitivity of the film. The effect of the incorporation of WPPB on the properties of WPPP/MMT films was investigated. The colorimetric response of WPPP/MMT/WPPB to pH and ammonia was examined, respectively. Moreover, WPPP/MMT/WPPB-2 was employed to monitor the freshness of shrimp. The color of the film changed from redness to reddish-brown, and further to brownness, echoing the shrimp turned from fresh to spoiled. Therefore, WPPP/MMT/WPPB-2 composite films showed promise for the applications in monitoring the freshness of shrimp.

Development of pH-responsive konjac glucomannan/pullulan films incorporated with acai berry extract to monitor fish freshness

In this work, konjac glucomannan (KGM)-based film reinforced with pullulan (PL) and acai berry extract (ABE) was developed by solvent casting method. The as-prepared films performed pH-sensitive properties, which can be potentially applied for fish freshness detection. Rheology, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) were used to characterize chemical structure and morphology of ABE-loaded KGM/PL (KP) films (KP-ABE). FT-IR spectrum indicated that hydrogen bond dominated the formation of KP-ABE films. Adding PL contributed to enhanced mechanical properties of KGM film with increased tensile strength (TS) from 21.25 to 50.27 MPa and elongation at break (EAB) from 10.64 to 19.19 %. Incorporating ABE upgraded flexibility, UV-shielding, thermostability, water barrier (decreased Water vapor permeability (WVP) from 2.07 to 1.67 g·mm/m²·day kPa), antioxidant, and antibacterial ability of KP films, but weakened TS. In addition, KP-ABE films can reflect fish freshness in real time through color variability. Therefore, KP-ABE films exhibited potential applications in intelligent food packaging materials.

Characterizations and antibacterial activities of passion fruit peel pectin/chitosan composite films incorporated Piper betle L. leaf extract for preservation of purple eggplants

The present study aimed to synthesize biodegradable films based on crosslinked passion fruit peel pectin/chitosan (P/CH) films incorporated with a bioactive extract from Piper betle L. leaf, and investigate their morphological, mechanical, water vapor permeability, optical, and antibacterial properties. The thickness and water vapor permeability of P/CH blend films were proportional to the increasing concentration of Piper betle extract (PB). The tensile strength of P/CH/PB films was significantly reduced at 42.89% compared to the P/CH films. The morphological characterization affirmed that resultant blend films showed a well-organized homogeneous structure with no cracks. Moreover, the antibacterial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, and Klebsiella pneumoniae increased with the increased concentration of PB in the obtained films. Our results demonstrated that P/CH/PB blend films could be potentially used for food packaging applications.

A novel colorimetric indicator film based on watermelon peel pectin and anthocyanins from purple cabbage for monitoring mutton freshness

Novel films based on watermelon peel pectin (WMP) incorporated with purple cabbage extract (PCE) were developed for monitoring the freshness of mutton. The FTIR result showed that WMP and PCE interacted through hydrogen bonds. Low PCE content (≤1.5%) could be well dispersed in the film matrix, resulting in an enhancement in light transmittance, mechanical properties, barrier properties, and thermal stability. Excessive addition of PCE destroyed the compact structure of the film and decreased the comprehensive properties. The antioxidant and antimicrobial activity of WMP/PCE films were proportional to the amount of incorporated PCE. Moreover, the color of the film deepened as the PCE content increased. The film had excellent color stability and pH response properties. The WMP/PCE1.5 film color varied from mauve to baby blue according to the quality of mutton (fresh to spoiled). Our results suggested that the WMP/PCE film might have great potential for monitoring the freshness of mutton.

Smart films fabricated from natural pigments for measurement of total volatile basic nitrogen (TVB-N) content of meat for freshness evaluation: A systematic review

Major databases were searched from January 2012 to August 2021 and 54 eligible studies were included in the meta-analysis to estimate the overall mean of total volatile basic nitrogen (TVB-N) in meat. The mean of TVB-N was 24.96 mg/100 g (95 % CI:23.10-26.82). The pooled estimate of naphthoquinone, curcumin, anthocyanins, alizarin and betalains were 25.98 mg/100 g (95 %CI:19.63-32.33), 30.03 mg/100 g (95 %CI: 24.15-35.91), 24.92 mg/100 g (95 %CI: 22.55-27.30), 23.37 mg/100 g (95 %CI:19.42-27.33) and 19.50 mg/100 g (95 %CI:17.87-21.12), respectively. Meanwhile, subgroups based on meat types showed that smart film was most used in aquatic products at 27.19 mg/100 g (95 %CI:24.97-29.42), followed by red meat at 19.69 mg/100 g (95 %CI:17.44-21.94). Furthermore, 4 °C was the most storage temperature used for testing the performance of smart films at 25.48 mg/100 g (95 %CI:23.05-27.90), followed by storage at 25 °C of 25.65 mg/100 g (95 %CI:22.17-29.13). Substantial heterogeneity was found across the eligible studies (I² = 99 %, p = 0.00). The results of the trim-and-fill method demonstrated publication bias was well controlled.

Meat 4.0: Principles and Applications of Industry 4.0 Technologies in the Meat Industry

Meat 4.0 refers to the application the fourth industrial revolution (Industry 4.0) technologies in the meat sector. Industry 4.0 components, such as robotics, Internet of Things, Big Data, augmented reality, cybersecurity, and blockchain, have recently transformed many industrial and manufacturing sectors, including agri-food sectors, such as the meat industry. The need for digitalised and automated solutions throughout the whole food supply chain has increased remarkably during the COVID-19 pandemic. This review will introduce the concept of Meat 4.0, highlight its main enablers, and provide an updated overview of recent developments and applications of Industry 4.0 innovations and advanced techniques in digital transformation and process automation of the meat industry. A particular focus will be put on the role of Meat 4.0 enablers in meat processing, preservation and analyses of quality, safety and authenticity. Our literature review shows that Industry 4.0 has significant potential to improve the way meat is processed, preserved, and analysed, reduce food waste and loss, develop safe meat products of high quality, and prevent meat fraud. Despite the current challenges, growing literature shows that the meat sector can be highly automated using smart technologies, such as robots and smart sensors based on spectroscopy and imaging technology.

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

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

Active edible films with plant extracts: a updated review of their types, preparations, reinforcing properties, and applications in muscle foods packaging and preservation

Currently, edible films have been increasingly explored to solve muscle food spoilage during storage, especially through the incorporation of plant extracts to develop edible packaging materials. Natural polymers matrices with plant extracts are befitting for fabricating edible films by casting methods. In the films system, the structure and physicochemical properties were strengthened via chemical interactions between active molecules in plant extracts and the reactive groups in the polymer chain. The antibacterial and antioxidant properties were dramatically reinforced through both physical and chemical actions of the plant extracts. Additionally, edible films imbedded with color-rich plant extracts could be considered as potential sensitive indicators to monitor the spoilage degree of muscle foods in response to change in gas or temperature. Furthermore, these films could increase sensory acceptability, improve quality and prolong the shelf life of muscle foods. In this article, the types, preparation methods and reinforcing properties of the edible films with plant extracts were discussed. Also, the applications of these films were summarized on quality maintenance and shelf-life extension and intelligent monitoring in muscle foods. Finally, a novel technology for film preparation achieving high-stability and sustained release of active compounds will become an underlying trend for application in muscle food packaging.