A halochromic indicator based on polylactic acid and anthocyanins for visual freshness monitoring of minced meat, chicken fillet, shrimp, and fish roe

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

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

Double layer packaging based on active black chickpea protein isolate electrospun nanofibers and intelligent salep film containing black chickpea peel anthocyanins for seafood products

In this study, a double-layer active and intelligent packaging system was developed based on two main natural macromolecules i.e. protein and carbohydrate with green perspective. Firstly, the salep-based films containing different concentrations (0-8 % w/w) of the inclusion complex of β-cyclodextrin/black chickpea anthocyanins (βCD/BCPA) were produced. The salep film containing 8 % of βCD/BCPA complex was specified as the optimized film sample based on its performance as a color indicator. The electrospinning of black chickpea protein isolate nanofibers (BCPI NFs) containing citral nanoliposomes (NLPs) was done on the optimized salep film. The cross-sectional field emission scanning electron microscopy approved the creation of double-layer structure of the developed film. The study of chemical and crystalline structure, as well as the thermal properties of the film exhibited the physical attachment of BCPI electrospun NFs on salep film. The effectiveness of the developed system was studied in detection of spoilage and increasing the shelf life of seafood products, including shrimp and fish fillet. The performance of the intelligent layer in detection of freshness/spoilage was acceptable for both seafood products. In addition, the active layer of the film controlled the changes of pH, total volatile basic nitrogen, oxidation, and microbial load in samples during storage time.

Bioactive chitosan films: Integrating antibacterial, antioxidant, and antifungal properties in food packaging

In this work, chitosan was combined with bio-vanillin (BV) and kaolin clay (KC) to create a novel antifungal and biodegradable food packaging film. The chitosan/KC/BV film exhibited an antioxidant capacity of 80 % as measured by DPPH assay, which was significantly higher than that of the chitosan film which has 55.6 %). The film also demonstrated strong antimicrobial activity with a reduction of 90 % in the growth of E. coli and S. aureus compared to the control. Additionally, the chitosan/KC/BV film showed a 75 % reduction in fungal growth compared to chitosan film. Furthermore, the water vapor permeability of the chitosan film was reduced as 5.38 with the addition of KC/BV. The degradation study revealed that the chitosan/KC film degraded by 88 % within 20 days under composting conditions. Additionally, fresh-cut apple slices were used to examine the effectiveness of chitosan/KC/BV film as a packaging material. The fruit's weight loss and browning index showed satisfactory food preservation. Our research suggests that the chitosan/KC/BV film has great potential for use in the food sector due to its strong antioxidant, antimicrobial, and biodegradable properties.

Xanthan gum ink based on Lycium ruthenicum anthocyanin as an indicator of color change for monitoring freshness of cold fresh meat

The continuous development of intelligent food packaging has led to an increased focus on using freshness-indicating inks, which could provide a high level of quality control and consumer experience. This study aimed to further promote the application of xanthan gum ink in food freshness indication by optimizing its performance in screen printing. A novel freshness-indicating ink was prepared using Lycium ruthenicum anthocyanin (LRA) as the core indicator, glucose as the pigment carrier, soybean oil as the linker, and xanthan gum (XG) as the thickener. Scanning electron microscopy (SEM) demonstrated that the ink was uniformly distributed on paper using screen printing. Rheological and particle size analyses revealed that the incorporation of XG significantly enhanced the interaction force between droplets in the ink system. Further tests on viscosity, fineness, and initial dryness indicated that XG, a natural microbial polysaccharide with excellent stability, could effectively improve the flowability of the ink. Specifically, at a 0.3 % XG content, the ink exhibited a unimodal particle size distribution with an average particle size of 851.02 nm and a zeta potential of -27 mV. This indicated the ink system was stable and uniform, with optimal rheological properties and printing suitability. Furthermore, the printed freshness indication labels exhibited a significant change in color as the freshness of the refrigerated meat changed. This study develops a natural and safe method for monitoring the freshness of refrigerated meat and provides an optimized idea for applying indicator inks.

Bacterial nanocellulose-based nanopaper activated by β-cyclodextrin/ Salvia officinalis essential oil complexes for shelf life extension of shrimp

Active bacterial nanocellulose (BNC) nanopapers containing Salvia officinalis essential oil (SEO) in free form and encapsulated with β-cyclodextrin (βCD) were prepared, and their effect on the shelf life extension of shrimp was investigated. The GC-MS analysis of the SEO indicated the presence of various active compounds such as Thujone (21.53 %), Ledol (12.51 %) and Eucalyptol (11.28 %) in the essential oil composition. The cytotoxicity of the SEO and SEO-βCD complexes in the L929 cell line was quite low. FTIR analysis revealed new interactions in the nanopapers containing SEO-βCD complexes. Microscopic images showed that SEO-βCD complexation improved the surface morphology of the BNC nanopapers, whereas free SEO had a negative effect. X-ray diffraction patterns of the nanopapers showed higher crystallinity of the SEO-βCD containing nanopapers than that of the SEO-incorporated nanopapers. Moreover, the addition of the SEO-βCD complex improved the thermal properties of the BNC nanopaper. Water contact angle analysis showed higher hydrophobicity of the samples containing free SEO than that of the other samples. Both SEO-βCD and free SEO increased the elongation at break and decreased the tensile strength of the nanopaper. The prepared active films showed a greater antimicrobial effect on L. monocytogenes than on E. coli. The results showed a higher antioxidant capacity of the free SEO-containing nanopapers (58-78 %). The desirable effects of the active nanopapers on shrimp preservation were demonstrated by the results obtained for the microbial load, pH, and volatile nitrogen content of the product. The results demonstrate the potential of the prepared BNC active nanopapers for use in active antioxidant/antimicrobial food packaging.

Sustainable production of cellulosic biopolymers for enhanced smart food packaging: An up-to-date review

Biodegradable and sustainable food packaging (FP) materials have gained immense global importance to reduce plastic pollution and environmental impact. Therefore, this review focused on the recent advances in biopolymers based on cellulose derivatives for FP applications. Cellulose, an abundant and renewable biopolymer, and its various derivatives, namely cellulose acetate, cellulose sulphate, nanocellulose, carboxymethyl cellulose, and methylcellulose, are explored as promising substitutes for conventional plastic in FP. These reviews focused on the production, modification processes, and properties of cellulose derivatives and highlighted their potential for their application in FP. Finally, we reviewed the effects of incorporating cellulose derivatives into film in various aspects of packaging properties, including barrier, mechanical, thermal, preservation aspects, antimicrobial, and antioxidant properties. Overall, the findings suggest that cellulose derivatives have the potential to replace conventional plastics in food packaging applications. This can contribute to reducing plastic pollution and lessening the environmental impact of food packaging materials. The review likely provides insights into the current state of research and development in this field and underscores the significance of sustainable food packaging solutions.

Natural colorant incorporated biopolymers-based pH-sensing films for indicating the food product quality and safety

The current synthetic plastic-based packaging creates environmental hazards that impact climate change. Hence, the topic of the current research in food packaging is biodegradable packaging and its development. In addition, new smart packaging solutions are being developed to monitor the quality of packaged foods, with dual functions as food preservation and quality indicators. In the creation of intelligent and active food packaging, many natural colorants have been employed effectively as pH indicators and active substances, respectively. This review provides an overview of biodegradable polymers and natural colorants that are being extensively studied for pH-indicating packaging. A comprehensive discussion has been provided on the current status of the development of intelligent packaging systems for food, different incorporation techniques, and technical challenges in the development of such green packaging. Finally, the food industry and environmental protection might be revolutionized by pH-sensing biodegradable packaging enabling real-time detection of food product quality and safety.

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.

Preparation and properties of polyvinyl alcohol/chitosan-based hydrogel with dual pH/NH3 sensor for naked-eye monitoring of seafood freshness

To address the issue of food spoilage causing health and economic loss, we developed a pH/NH3 dual sensitive hydrogel based on polyvinyl alcohol/chitosan (PVA/CS) containing chitosan-phenol red (CP). The CP was synthesized via Mannich reaction and immobilized it in PVA/CS hydrogel through freezing/thawing method to prepare the final PVA/CS/CP hydrogel. The synthesis of CP was confirmed by 1H NMR, FT-IR, XRD, UV-vis, and XPS. The characteristics of hydrogel were evaluated by FT-IR, XRD, SEM, mechanical properties, thermal stability, leaching, and color stability tests. The PVA/CS/CP hydrogel showed distinctly different color at various pH and NH3 vapor levels (yellow to purple). The hydrogel exhibited obvious color changes (ΔE = 46.95) in response to shrimp spoilage, stored at 4 °C. It showed positive and strong correlation between the ΔE values of the indicator hydrogel and total volatile basic nitrogen (TVB-N) as (R2 = 0.9573) and with pH as (R2 = 0.8686), respectively. These results clearly show that the PVA/CS/CP hydrogel could be applied for naked-eye real-time monitoring of seafood freshness in intelligent packaging.

Effect of polyethylene glycol on polysaccharides: From molecular modification, composite matrixes, synergetic properties to embeddable application in food fields

Polyethylene glycol (PEG) is a flexible, water-soluble, non-immunogenic, as well as biocompatible polymer, and it could synergize with polysaccharides for food applications. The molecular modification strategies, including covalent bond interactions (amino groups, carboxyl groups, aldehyde groups, tosylate groups, etc.), and non-covalent bond interactions (hydrogen bonding, electrostatic interactions, etc.) on PEG molecular chains are discussed. Its versatile structure, group modifiability, and amphiphilic block buildability could improve the functions of polysaccharides (e.g., chitosan, cellulose, starch, alginate, etc.) and adjust the properties of combined PEG/polysaccharides with outstanding chain tunability and matrix processability owing to plasticizing effects, compatibilizing effects, steric stabilizing effects and excluded volume effects by PEG, for achieving the diverse performance targets. The synergetic properties of PEG/polysaccharides with remarkable architecture were summarized, including mechanical properties, antibacterial activity, antioxidant performance, self-healing properties, carrier and delivery characteristics. The PEG/polysaccharides with excellent combined properties and embeddable merits illustrate potential applications including food packaging, food intelligent indication/detection, food 3D printing and nutraceutical food absorption. Additionally, prospects (like food innovation and preferable nutrient utilization) and key challenges (like structure-effectiveness-applicability relationship) for PEG/polysaccharides are proposed and addressed for food fields.

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.

Development of halochromic electrospun labels for non-invasive shelf life assessment of rainbow trout (Oncorhynchus mykiss): Incorporation of barberry anthocyanin extract in protein-based smart packaging

Using barberry (Berberis vulgaris L.) as a natural dye in combination with electrospinning technology represents a promising approach for the development of intelligent packaging systems. In this study, the influence of different concentrations of zein (16, 18, and 20%) and barberry anthocyanin-rich powder (BARP) (16, 18, and 20%) on the surface tension and rheological properties of the solution were evaluated. The most favorable nanofibers (NFs) were obtained from a solution containing 18% (w/w) zein under constant voltage. The surface morphology, size, and color-changing properties of electrospun NFs derived from zein polymers containing different concentrations of BARP (16, 18, and 20%) under various electrical fields (20, 22, and 24 kV) were evaluated. The Fourier-transform infrared spectroscopy analysis confirmed the interaction of BARP within the zein-based NFs. The results indicated that the concentration of BARP had a noticeable impact on the physicochemical properties of the NFs. Furthermore, efficacy of the appropriately fabricated halochromic label was evaluated for monitoring the packed rainbow trout fillet during refrigerated storage. On the 10th day, a noticeable visual color turned from pink to pale yellow was observed in response to pH variations. Additionally, the TVN value confirmed the effectiveness of halochromic electrospun labels for non-invasive assessment of fish fillet quality.

On-site colorimetric food spoilage monitoring with smartphone embedded machine learning

Real-time and on-site food spoilage monitoring is still a challenging issue to prevent food poisoning. At the onset of food spoilage, microbial and enzymatic activities lead to the formation of volatile amines. Monitoring of these amines with conventional methods requires sophisticated, costly, labor-intensive, and time consuming analysis. Here, anthocyanins rich red cabbage extract (ARCE) based colorimetric sensing system was developed with the incorporation of embedded machine learning in a smartphone application for real-time food spoilage monitoring. FG-UV-CD100 films were first fabricated by crosslinking ARCE-doped fish gelatin (FG) with carbon dots (CDs) under UV light. The color change of FG-UV-CD100 films with varying ammonia vapor concentrations was captured in different light sources with smartphones of various brands, and a comprehensive dataset was created to train machine learning (ML) classifiers to be robust and adaptable to ambient conditions, resulting in 98.8% classification accuracy. Meanwhile, the ML classifier was embedded into our Android application, SmartFood++, enabling analysis in about 0.1 s without internet access, unlike its counterpart using cloud operation via internet. The proposed system was also tested on a real fish sample with 99.6% accuracy, demonstrating that it has a great advantage as a potent tool for on-site real-time monitoring of food spoilage by non-specialized personnel.

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.

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.

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.

Preparation of chitosan/gelatin-based functional films integrated with carbon dots from banana peel for active packaging application

Carbon dots (CDs) were manufactured with banana peels using a hydrothermal method (200 °C for 6 h). The synthesized CDs were spherical particles with a size of 1-3 nm having carboxyl groups and amine groups on the surface. CDs have been impregnated into chitosan/gelatin films to synthesize multifunctional packaging films. The composite film showed a slight decrease in transparency but a significant increase in UV protection properties. The fabricated film displayed strong antioxidant efficacy showing >74 % DPPH and 99 % ABTS radical scavenging potential. The film also unveiled substantial antibacterial activity against the foodborne pathogenic bacteria, Listeria monocytogenes, fully eliminating the growth of these bacteria within 6 h of exposure. The chitosan/gelatin film containing CD was used for minced meat packaging, and the film delayed bacterial growth (< 1 Log CFU/g after 24 h) and maintained the meat color even after 24 h of storage at 20 °C. The CD-added chitosan/gelatin functional film has a high probability of application in active food packaging, especially for extending the shelf life of packaged meat and maintaining its aesthetic quality.

The potential of anthocyanin-loaded alginate hydrogel beads for intelligent packaging applications: Stability and sensitivity to volatile amines

pH indicators have emerged as promising tools for real-time monitoring of product freshness and quality in intelligent food packaging applications. However, ensuring the stability of these indicators is critical for practical use. This study aims to evaluate the stability of anthocyanins-loaded alginate hydrogel beads of varying sizes at different temperatures under accelerated light conditions and relative humidity (RH) levels of 53% and 97% during 21 days of storage. Moreover, their sensitivity to the principal spoilage volatiles of muscle food products such as ammonia (NH3), dimethylamine (DMA) and trimethylamine (TMA) was investigated. The half-life of cyanidin-3-glucoside in small hydrogel beads was roughly twice as long as that of the larger beads under accelerated light exposure at 4 °C and they were less likely to undergo noticeable color changes over time. Both sizes of hydrogel beads stored at 97% RH and 4 °C showed color stability over the 21-day period with minimal color variation (|ΔE| ≤ 3). The UV-vis spectra of the purple corn extract exhibited changes across pH 2 to 12, as evidenced by the visible color variations, ranging from pink to green. The limit of detection (LOD) for NH3 was 25 ppm for small beads and 15 ppm for large ones. Both types of beads exhibited similar LOD for DMA and TMA, around 48 ppm. This research showed that alginate hydrogel beads containing anthocyanins from purple corn are a viable option for developing intelligent packaging of muscle foods. Furthermore, the use of hydrogel beads of different sizes can be customized to specific muscle foods based on the primary spoilage compound generated during spoilage.

Cellulose/Salep-based intelligent aerogel with red grape anthocyanins: Preparation, characterization and application in beef packaging

The purpose of this study was to prepare a porous intelligent aerogel for food packaging applications, in particular for monitoring minced beef freshness, using cellulose extracted from grape stalk, Salep as a copolymer, and red grape anthocyanins as a pH-sensitive pigment. Aerogels based on cellulose 1% (w/v) and Salep 1% (w/v) at ratios of 1:3, 3:1, and 1:1 were prepared by lyophilization. Aerogel with high porosity, low density, and higher mean pore size was chosen for preparing intelligent colorimetric aerogel (ICA) with the addition of 0.44 mg/100 mL of anthocyanins. Based on the color parameters, the stability of ICA was satisfactory when exposed to both light and dark conditions, as well as when stored at either 4 or 25 °C. Additionally, X-ray diffraction and thermogravimetric analyses indicated that an amorphous aerogel was formed, with a thermal decomposition temperature of 320 °C. The color of the ICA changed from purple on the first and 3rd days of packaging to blue-gray on the 6th day. As the spoilage process continued, the color of the indicator became dark brown. Taken together, ICA showed a quick response to minced beef spoilage with the ability to differentiate between fresh and spoiled meat during storage at 4 °C.

Sumac (Rhus coriaria L.) anthocyanin loaded-pectin and chitosan nanofiber matrices for real-time monitoring of shrimp freshness

In this study, pectin (PC)/chitosan nanofiber (ChNF) films containing a novel anthocyanin from sumac extract were successfully developed for freshness monitoring and shelf-life extension of shrimp. The physical, barrier, morphological, color, and antibacterial properties of biodegradable films were evaluated. The addition of sumac anthocyanins to the films caused intramolecular interactions (such as hydrogen bonds) in the film structure, as confirmed by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) analysis, suggesting good compatibility of film ingredients. Also, intelligent films showed significant sensitivity to ammonia vapors and changed color from reddish to olive color at the first 5 min. Moreover, the results showed that PC/ChNF and PC/ChNF/sumac films have significant antibacterial activity against Gram-positive bacteria and Gram-negative bacteria. In addition to the good functional characteristics of the smart film, the resulting films showed acceptable physicomechanical properties. So, PC/ChNF/sumac smart film exhibited the strength = 60 MPa with the flexibility = 23.3 %. Likewise, water vapor barrier reduced from 2.5 (×10^-11 g. m/m². s. Pa) to 2.3 (×10^-11 g. m/m². s. Pa) after adding anthocyanin. The results of the application of intelligent film containing anthocyanins of sumac extract for shrimp freshness monitoring showed that the color of the intelligent film changed from reddish to greenish color after 48 h of storage, which shows the high potential of the produced film for monitoring the spoilage of seafood products.

Visual Colorimetric Detection of Edible Oil Freshness for Peroxides Based on Nanocellulose

Traditional methods for evaluating the edibility of lipids involve the use of organic reagents and complex operations, which limit their routine use. In this study, nanocellulose was prepared from bamboo, and a colorimetric reading strategy based on nanocellulose composite hydrogels was explored to monitor the freshness of edible oils. The hydrogels acted as carriers for peroxide dyes that changed color according to the freshness of the oil, and color information was digitized using UV-vis and RGB analysis. The sensitivity and accuracy of the hydrogel were verified using H₂O₂, which showed a linear relationship between absorbance and H₂O₂ content in the range of 0-0.5 and 0.5-11 mmol/kg with R² of 0.9769 and 0.9899, respectively, while the chromatic parameter showed an exponential relationship with R² of 0.9626. Surprisingly, the freshness of all seven edible oil samples was correctly identified by the hydrogel, with linear correlation coefficients greater than 0.95 in the UV-vis method and exponential correlation coefficients greater than 0.92 in the RGB method. Additionally, a peroxide value color card was established, with an accuracy rate of 91.67%. This functional hydrogel is expected to be used as a household-type oil freshness indicator to meet the needs of general consumers.

Recent advancements in natural colorants and their application as coloring in food and in intelligent food packaging

Colorants are widely employed in the food industry as an essential ingredient in many products since color is one of the most valued attributes by consumers. Furthermore, the utilization of colorants is currently being extended to the food packaging technologies. The objective of this review was to compile recent information about the main families of natural coloring compounds, and to describe their real implications in food coloring. In addition, their technological use in different food systems (namely, bakery products, beverages, meat and meat products, and dairy products) and their utilization in intelligent packaging to monitor the freshness of foodstuffs with the aim of extending food shelf life and improving food properties was discussed. The potential of using natural colorant in different food to improve their color has been demonstrated, although color stability is still a challenging task. More interestingly, the application of intelligent colorimetric indicators to exhibit color changes with variations in pH can enable real-time monitoring of food quality.

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

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

Application of bacterial nanocellulose decorated with zeolitic imidazolate framework (ZIF-L) as a platform for food freshness monitoring

Recently, the food freshness indicator (FFI) has garnered great interest from consumers and food producers. A novel FFI based on bacterial nanocellulose (BNC)/zeolitic imidazolate framework-L (ZIF-L) and grape anthocyanins was developed and characterized using field emission scanning electron microscopy, Fourier-transform infrared, X-ray diffraction, water contact angle, and BET techniques. The results confirmed that the BNC fibrils were decorated by in situ growth of ZIF-L, with a 3D flower-shaped structure and randomly multiple sharp-edged petals, and hydroxyl and oxygenated heterocycle aromatic ring functional groups on its surface. The reversibility, color stability performance, and moisture sorption of FFI were studied and its applicability in a two-layer arrangement as a visual freshness monitoring of shrimp and minced beef was evaluated. The FFI was able to distinguish (ΔE > 5) the fresh, medium fresh, and spoiled minced meat and shrimp visually during 10 and 4 days of storage at 4 °C, respectively. Also, monitoring of food chemical and microbiological parameters approved the correlation of food spoilage with the color parameters of FFI. These results confirmed the function of ZIF-L in the fabrication of highly pH-sensitive food intelligent packaging material.

Fabrication and characterization of a smart film based on cassava starch and pomegranate peel powder for monitoring lamb meat freshness

Nowadays, the development of pH-sensitive smart edible films using biopolymers and natural plant extracts (especially those rich in anthocyanins) has attracted much attention. Therefore, in this study, the intelligent edible film was produced and characterized using cassava starch and pomegranate peel powder (PPP) and the possibility of using production films to monitor the freshness of lamb meat. The smart films were prepared using different concentrations of PPP (2, 4, 6, and 8% w/w) and the solvent casting method. The results showed that the incorporation of PPP had a significant effect on the mechanical parameters of the starch films. With increasing the levels of PPP, the color of the films became darker and redder. Increasing the PPP levels also led to an increase in total phenol content (TPC) (from 0 to 13 mg GAE (gallic acid equivalent)/g) and antioxidant activity (from 0% to 70% DPPH (1,1-diphenyl-2-picryl hydrazyl) radical scavenging) of the produced films (p < .05). The intelligent film was used in the lamb meat packaging, and the color of the film changed from red to green during the storage period at 25°C. The amount of total volatile basic nitrogen (TVB-N) in the meat could be detected by color changes of the intelligent films. Finally, this study demonstrated that the film based on cassava starch and PPP could be used as an intelligent and pH-sensitive film to monitor the freshness of meat and meat products.

Shikonin Functionalized Packaging Film for Monitoring the Freshness of Shrimp

A shikonin embedded smart and active food packaging film was produced using a binary mixture of gelatin and cellulose nanofiber (CNF). Shikonin is an alcohol-soluble natural pigment extracted from Lithospermum erythrorhizon root. The fabricated film showed good pH-responsive color changes and volatile gas sensing properties. Moreover, the film exhibited excellent antioxidant and antibacterial activity against foodborne pathogens. The shikonin incorporated gelatin/CNF-based film showed excellent UV-light barrier properties (>95%) and high tensile strength (>80 MPa), which is useful for food packaging. The hydrodynamic properties of the film were also slightly changed in the presence of shikonin, but the thermal stability and water vapor permeability remained unaffected. Thus, the inclusion of shikonin in the gelatin/CNF-based film improves not only the physical properties but also the functional properties. The film’s color indicator properties also clearly show shrimp’s freshness and spoilage during storage for 48 h. The shikonin-based functional film is expected to be a promising tool for multi-purpose smart and active food packaging applications.

Polymeric Packaging Applications for Seafood Products: Packaging-Deterioration Relevance, Technology and Trends

Seafood is a highly economical product worldwide. Primary modes of deterioration include autolysis, oxidation of protein and lipids, formation of biogenic amines and melanosis, and microbial deterioration. These post-harvest losses can be properly handled if the appropriate packaging technology has been applied. Therefore, it is necessary for packaging deterioration relevance to be clearly understood. This review demonstrates recent polymeric packaging technology for seafood products. Relationship between packaging and quality deterioration, including microbial growth and chemical and biochemical reactions, are discussed. Recent technology and trends in the development of seafood packaging are demonstrated by recent research articles and patents. Development of functional polymers for active packaging is the largest area for seafood applications. Intelligent packaging, modified atmosphere packaging, thermal insulator cartons, as well as the method of removing a fishy aroma have been widely developed and patented to solve the specific and comprehensive quality issues in seafood products. Many active antioxidant and antimicrobial compounds have been found and successfully incorporated with polymers to preserve the quality and monitor the fish freshness. A thermal insulator has also been developed for seafood packaging to preserve its freshness and avoid deterioration by microbial growth and enzymatic activity. Moreover, the enhanced biodegradable tray is also innovative as a single or bulk fish container for marketing and distribution. Accordingly, this review shows emerging polymeric packaging technology for seafood products and the relevance between packaging and seafood qualities.

Poly-l-lactic acid (PLLA)/anthocyanin nanofiber color indicator film for headspace detection of low-level bacterial concentration

Since bacterial contamination is a significant threat to humans, early detection is essential to safeguard dietary safety and physical health. Here, a nanofiber color indicator film based on poly-l-lactic acid (PLLA) as the support and anthocyanin as the indicator material was prepared by electrostatic spinning. It was found that the PLLA/0.8CY nanofiber color indicator film was hydrophobic (the water contact angle of 102.4°) and contained uniform nanofibers with an average diameter of 750 nm. In addition, the film's humidity insensitivity, reusability, color stability, and ammonia sensitivity (the limits of detection 35.39 ppm) made the film environmentally friendly and more accurate and faster for bacterial detection. The film was able to sense 102 CFU/mL of gram-positive and negative bacteria after the model strain E. coli and L. monocytogene. Thus, the PLLA/0.8CY nanofiber color indicator film was able to perform headspace nondestructive detection of low-level bacterial contamination.

High- sensitivity bilayer nanofiber film based on polyvinyl alcohol/sodium alginate/polyvinylidene fluoride for pork spoilage visual monitoring and preservation

A colorimetric bilayer film for pork freshness detection and preservation was developed using electrospinning technique. The bilayer film consisted of a layer with polyvinyl alcohol - sodium alginate - alizarin as sensor layer and a layer with polyvinylidene fluoride - vanillin as antibacterial layer. The water contact angle of bilayer film was larger than the single colorimetric layer. The color sensitivity to the ammonia of the bilayer film was higher, with an ΔE value of 47.99. The film could display color shifts from yellow to purple with the naked eye is critical for checking pork freshness. In addition, the bilayer film exhibited sensitive antibacterial activity, with an inhibition zone against S. aureus (8.3 mm) and E. coli (14.7 mm), respectively. Finally, the bilayer film was applied to freshness monitoring of pork. The film displayed significant color changes and prolonged the pork shelf life by 24 h at 25 °C.

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

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