Colorimetric indicator based on purple tomato anthocyanins and chitosan for application in intelligent packaging

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

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

Intelligent food packaging for smart sensing of food safety

In this contemporary era, with over 8 billion people worldwide, ensuring food safety has become more critical than ever. To address this concern, the introduction of intelligent packaging marks a significant breakthrough. Essentially, this innovation tackles the challenge of rapid deterioration in perishable foods, which is vital to the well-being of communities and food safety. Unlike traditional methods that primarily emphasize shelf-life extension, intelligent packaging goes further by incorporating advanced sensing technologies to detect signs of spoilage and contamination in real-time, such as changes in temperature, oxygen levels, carbon dioxide levels, humidity, and the presence of harmful microorganisms. The innovation can rely on various packaging materials like plastics, metals, papers, or biodegradable polymers, combined with sophisticated sensing techniques such as colorimetric sensors, time-temperature indicators, radio-frequency identification tags, electronic noses, or biosensors. Together, these elements form a dynamic and tailored packaging system. This system not only protects food from spoilage but also offers stakeholders immediate and adequate information about food quality. Moreover, the real-world application on seafood, meat, dairy, fruits, and vegetables demonstrates the feasibility of using intelligent packaging to significantly enhance the safety and shelf life of a wide variety of perishable goods. By adopting intelligent packaging for smart sensing solutions, both the food industry and consumers can significantly reduce health risks linked with contamination and reduce unnecessary food waste. This underscores the crucial role of intelligent packaging in modern food safety and distribution systems, showcasing an effective fusion of technology, safety, and sustainability efforts aimed at nourishing a rapidly growing global population.

Effects of crosslinking agents on properties of starch-based intelligent labels for food freshness detection

The impact of citric acid, carboxymethyl cellulose, carboxymethyl starch, sodium trimetaphosphate, or soybean protein on the crosslinking of starch-based films was examined. These crosslinking starch films were then used to create pH-sensitive food labels using a casting method. Blueberry anthocyanins were incorporated into these smart labels as a pH-sensitive colorimetric sensor. The mechanical properties, moisture resistance, and pH responsiveness of these smart labels were then examined. Crosslinking improved the mechanical properties and pH sensitivity of the labels. These different crosslinking agents also affected the hydrophobicity of the labels to varying degrees. Soybean protein was the only additive that led to labels that could sustain their structural integrity after immersion in water for 12 h. Because it increased the hydrophobicity of the labels, which decreased their water vapor permeability, moisture content, swelling index, and water solubility by 47 %, 29 %, 52 % and 10 %, respectively. The potential of using these labels to monitor the freshness of chicken breast was then examined. Only the films containing soybean protein exhibited good pH sensitivity, high structural stability, and low pigment leakage. This combination of beneficial attributes suggests that the composite films containing starch and soybean protein may be most suitable for monitoring meat freshness.

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.

Multifunctional alginate films blended with polyphenol-rich extract from unconventional edible sources: Bioactive properties, UV-light protection, and food freshness monitoring

The development of active and smart packaging from non-conventional food sources is an ecological trend to ensure safe food supply in the food chain. The study aimed to develop multifunctional films based on alginate blended with different concentrations of purple onion peel (POPE) and butterfly-pea flower extract (BFE). The addition of the extracts increased the opacity of the films by 80 %, indicating greater UV-light barrier ability. The tensile strength and elongation at break of the films increased by 70 % and 30 %, while water vapor permeability decreased by 15 %. The interaction between the extract and the alginate positively modified the structure of the films, increasing the melting temperature of the films (112-131 °C). Mixing both extracts in the matrix generated materials with antioxidant activity, antimicrobial capabilities, and sensitivity to freshness factors (gases, pH, and temperature) superior to films added with a single extract, suggesting better active and intelligent performances. The films protected the color of food products against the effects of UV-light, being strongly capable of colorimetrically checking the deterioration of protein-rich products. Therefore, alginate films blended with POPE and BFE have a promising potential for developing smart materials, preserving, and monitoring the food quality.

Pressurized liquid extraction of bioactive compounds from grape peel and application in pH-sensing carboxymethyl cellulose films: A promising material to monitor the freshness of pork and milk

This study produced pH-sensing carboxymethyl cellulose (CMC) films functionalized with bioactive compounds obtained by pressurized liquid extraction (PLE) of grape peel to monitor the freshness of pork and milk. A semi-continuous PLE was conducted using hydroethanolic solution (70:30, v/v) at a flow rate of 5 mL/min, 15 MPa, and 60 °C. The films were produced by the casting technique using CMC (2.5 %, w/v), glycerol (1 %, v/v), and functionalized with 10, 30, and 50 % (v/v) grape peel extract. From the results obtained, LC-MS/MS revealed that PLE extracted twenty-seven phenolic compounds. The main phenolic compounds were kaempferol-3-glucoside (367.23 ± 25.88 µg/mL), prunin (270.23 ± 3.62 µg/mL), p-coumaric acid (236.43 ± 26.02 µg/mL), and procyanidin B1 (117.17 ± 7.29 µg/mL). The CMC films presented suitable color and mechanical properties for food packaging applications. The addition of grape peel extract promoted the pH-sensing property, showing the sensitivity of anthocyanins to pH changes. The films functionalized with grape peel extract presented good release control of bioactive compounds, making them suitable for food packaging applications. When applied to monitor the freshness of pork and milk, the films exhibited remarkable color changes associated with the pH of the food during storage. In conclusion, PLE is a sustainable approach to obtaining bioactive compounds from the grape peel, which can be applied in the formulation of pH-sensing films as a promising sustainable material to monitor food freshness during storage.

Colorimetric Films Based on Polyvinyl Alcohol and Anthocyanins Extracted from Purple Tomato to Monitor the Freshness of Shrimp

Anthocyanin extracts from purple tomato (PTA) were incorporated with polyvinyl alcohol (PVA), resulting in a series of colorimetric PVA/PTA films with PTA concentrations of 0%, 1%, 3%, and 5% (based on PVA). The role of anthocyanin on color response, Fourier-transform infrared (FTIR), thickness, water content, mechanical properties, antioxidant activity, and water vapor permeability (WVP) through the films was examined. In addition, its application in smart packaging to assess the freshness of shrimp was studied. It was found that the tensile strength, contact angle and WVP of PVA/PTA films increases with the addition of more PTA, while the elongation at break and water content decreased. FTIR analysis showed that there are interactions between PTA and the PVA matrix. The addition of anthocyanins caused significant improvement in the antioxidant properties of PVA films. Furthermore, the total volatile alkaline nitrogen (TVB-N), total plate count (TPC), and pH value of shrimp were monitored after 4 days of refrigeration, and the color change of the indexes was recorded. The PVA/PTA films changed color from purple to yellow-green during the storage time of 0-4 days for shrimp. This suggests that the film could be used in smart packaging as a real-time freshness indicator for shrimp.

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

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

Novel ammonia-sensitive sodium alginate-based films containing Co-Imd microcrystals for smart packaging application

Currently, there is an urgent requirement for the fabrication of smart packaging materials that can be applied for the real-time visual monitoring of food freshness. In this research, cubic Co-MOF (Co-Imd) microcrystal with ammonia-sensitivity and antibacterial activity was manufactured and then anchored within sodium alginate (NaAlg) matrix to construct smart packaging materials. The structure, physical and functional performances of NaAlg-based films with different content of Co-Imd (0.5, 1.0 and 2.0 wt% on NaAlg basis) were then evaluated in detail. Results reveal that the incorporated Co-Imd fillers are equally anchored within the NaAlg matrix due to the generation of new hydrogen-bonding interaction, which make an obvious improvement in mechanical strength, toughness, oxygen/water barrier, and UV-blocking ability of the NaAlg film. Moreover, the constructed NaAlg/Co-Imd blend films show superior antibacterial capability, ammonia-sensitivity function as well as color stability. Ultimately, the NaAlg/Co-Imd blend films were successfully utilized for indicating the deterioration of shrimp based on noticeable color alteration, suggesting their tremendous prospects for utilization in smart active packaging. This work offers a facile and efficient method for fabricating novel ammonia-sensitive and long-term color-stable NaAlg-based film materials with improved mechanical strength, toughness, oxygen/water barrier, UV-blocking, and antibacterial performances for smart active packaging application.

An investigation of the morphological, thermal, mechanical, and barrier properties of an active packaging containing micro- and nano-sized ZnO particles

Biodegradable films are extremely important for food packaging applications since they minimize environmental effects. However, their application areas are limited due to insufficient characteristics required for particular applications. The objective of the present research was to improve the properties of sago-based biodegradable films embedded with nano- and micro-ZnO (zinc oxide). Nano and micro-ZnO were incorporated in the films at different percentages (1%, 3%, and 5%) in that the films were formed using the solvent casting method. The physicochemical, barrier, thermal, optical, morphology, and mechanical properties of sago-based films were investigated. Adding 5% of micro- and nano-ZnO significantly improved film thickness (0.162 and 0.150 mm, respectively) and WVP (4.40 and 5.64 (kg/s)/(m.Pa), respectively) while the optical properties and thermal stability exhibited superior performance. Micro-ZnO particles improved the mechanical properties of sago-based biodegradable films with the tensile strength reaching 6.173 MPa. Moreover, sago-based nano-ZnO films showed excellent UV-shielding performance and relatively good visible-light transmittance. This study suggested that sago biodegradable film incorporated with micro-ZnO could be an excellent alternative to petroleum-based plastic packaging.

Fabrication of green colorimetric smart packaging based on basil seed gum/chitosan/red cabbage anthocyanin for real-time monitoring of fish freshness

Novel green intelligent films based on basil seed gum (BSG)/chitosan containing red cabbage extract (RCA) (0, 2.5, 5, and 10, % (v/v)) as a colorimetric indicator for food freshness detection were fabricated by casting method. The physicochemical, barrier, mechanical, and antioxidant characteristics, as well as sensitivity to pH and ammonia gas of smart edible packaging films, were investigated. The interaction of anthocyanin extract as a natural dye with biopolymers in films characterized by FTIR spectroscopy and SEM images revealed their suitable compatibility. The film with maximum anthocyanin content (10% (v/v)) appeared robust color changes against various pH and ammonia gas levels. The color of indicator films when exposed to alkaline, neutral and acidic buffers are indicated with green, blue, and red colors, respectively. The DPPH radical scavenging activity of smart BSG/chitosan films improved from 23% to 90.32% with increasing RCA content from 2.5 to 10% (v/v). Generally, the incorporation of RCA in film structure enhanced their solubility, WVP, ΔE, turbidity, and flexibility, and reduced tensile strength. The observations successfully confirmed the efficacy of pH-sensitive indicator smart film based on BSG/chitosan for evaluation of fish spoilage during storage.

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

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

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.

Development and characterization of a novel biodegradable and antioxidant film based on marine seaweed sulfated polysaccharide

This research aims to produce an antioxidant and biodegradable polysaccharide film by using macroalgae agar and sulfated polysaccharide. Agar and sulfated polysaccharide (fucoidan) were extracted from Gracilaria corticata and Sargassum angustifolium macroalgae. Five treatments were conducted: (A) agar film (1%, W:V), (C) chitosan film (1%, W:V + 1% acetic acid), (AC) agar:chitosan composite (50:50, V:V), (ACF) AC film with fucoidan (0.5%, W:V), and (ACFA) ACF film with citric acid (30% of the dry weight of film) as a cross-linking agent. Then, 0.75% (V:V) of glycerol was added to all films. The physical, mechanical, antioxidant, color variations, microstructure (SEM), and Fourier transform infrared (FT-IR) spectroscopy were investigated. Based on the results, modifying the agar film with chitosan improved the mechanical strength, humidity, and solubility in the AC composite film (p < .05). Further, adding sulfated polysaccharide and citric acid cross-linking agent to the agar-chitosan composite led to a significant decrease in solubility, humidity, and permeability to water vapor in ACFA films (p < .05), indicating strong cross-linking and reduction in film pores based on the SEM pictures and FTIR results. However, the physical and mechanical properties of the agar-based film obtained from Gracilaria algae can be improved by adding chitosan and citric acid cross-linking agent, and the addition of fucoidan obtained from Sargassum algae has improved its antioxidant properties. This biodegradable film can be a good candidate for preserving perishable products.

Cross-linked CMC/Gelatin bio-nanocomposite films with organoclay, red cabbage anthocyanins and pistacia leaves extract as active intelligent food packaging: colorimetric pH indication, antimicrobial/antioxidant properties, and shrimp spoilage tests

Multifunctional food packaging films were produced from crosslinked carboxymethyl cellulose/gelatin (CMC/Ge) bio-nanocomposites incorporated with Ge-montmorillonite (OM) nanofiller, anthocyanins (ATH) from red cabbage as colorimetric pH-indicator, and pistacia leaves extract (PE) as active agent. The influence of additives on the structural, physical, and functional properties of the films was investigated. The results showed that ATH and PE caused color alteration and reduced transparency. However, they improved the UV light barrier ability by 98 %, with less impact from OM, despite its well-dispersed state in the matrix. Increasing PE content in the bio-nanocomposite films caused an increase in compactness and surface roughness, reduction in moisture content (15.10-12.33 %), swelling index (354.55-264.58 %), surface wettability (contact angle 80.1-92.49°), water vapor permeability (7.37-5.69 × 10¹⁰ g m^-1s^-1Pa^-1), and nano-indentation mechanical parameters, without affecting the thermal stability. ATH-included films demonstrated color pH-sensitivity with improved ATH color stability through the ATH-Al³⁺ chelates formation. PE-added films exhibited effective antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, reaching 93 % of inhibition, and antimicrobial properties with biocidal effects for PE-rich film. The shrimp spoilage test showed that the T-1.5PE film offered the strongest active intelligent response. The CMC/Ge-based bio-nanocomposite films endowed with antioxidant/antimicrobial properties and colorimetric pH-sensitivity have promising potential for food packaging application.

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.

Performance-enhanced regenerated cellulose film by adding grape seed extract

Eco-friendly packaging material with intelligent colorimetric performance has been a requirement for food safety and quality. This work focused on a food packaging material from regenerated cellulose films that added the grape seed extract (GSE) and polyethylene glycol 200 (PEG). FTIR and SEM techniques were employed to prove the compatibility of GSE with cellulose matrix. The composite film showed an enhanced elongation at break (16.61 %) and tensile strength (33.09 MPa). The addition of PEG and GSE also improved the water contact angle of regenerated-cellulose film from 53.8° to 83.8°. Moreover, the composite films exhibited UV-blocking properties while maintaining adequate transparency. The GSE induced the regenerated films with a macroscopic change in color under different pH conditions. Furthermore, the loading of GSE slowed down the decomposition of strawberries and delayed the self-biodegradation compared with the control for more than 3 days and 18 days. The present study showed a regenerated cellulose film with acceptable mechanical and hydrophilia properties, pH-responsiveness, anti-decomposition, and delayed biodegradation performances, indicating a potential color sensor in food packaging.

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.

Innovative processes in smart packaging. A systematic review

Smart packaging provides one possible solution that could reduce greenhouse gas emissions. In comparison with traditional packaging, which aims to extend the product's useful life and to facilitate transport and marketing, smart packaging allows increased efficiency, for example by ensuring authenticity and traceability from the product's origin, preventing fraud and theft, and improving security. Consequently, it may help to reduce pollution, food losses, and waste associated with the food supply chain. However, some questions must be answered to fully understand the advantages and limitations of its use. What are the most suitable smart packaging technologies for use in agro-industrial subsectors such as meat, dairy, fruits, and vegetables, bakery, and pastry? What are the opportunities from a perspective of life extension, process optimization, traceability, product quality, and safety? What are the future challenges? An up-to-date, systematic review was conducted of literature relevant to the application of indicator technologies, sensors, and data carriers in smart packaging, to answer these questions. © 2022 Society of Chemical Industry.

A novel pH-sensitive antibacterial bilayer film for intelligent packaging

Intelligent single-layer packaging is widely used in food monitoring and storage. However, most single-layer intelligent packaging has poor mechanical strength and water barrier properties. In this study, a bilayer intelligent detector film based on polyvinyl alcohol-chitosan (PVA-CS)/nano-ZnO/sodium alginate (SA) combined with anthocyanin extract (cyanidin chloride) was prepared using a layer-by-layer solution casting assembly technique. The effects of different levels of anthocyanin extracts on the physical and functional properties of the films, including microstructure, mechanical property, barrier property, pH sensitivity, and antibacterial property, were investigated. The results show that the bilayers exhibit excellent physical properties, lower water vapor permeability, better light transmission and UV-blocking properties, a broader pH sensitivity (ΔE > 10), and good antibacterial activity. In short, the bilayer films studied are superior to the single-layer films in terms of their packaging potential for products with low moisture content, offering new directions for active intelligent packaging and biodegradable materials for the food industry.

Graphical Abstract

Biopolymer-based functional films for packaging applications: A review

Food packaging is a coordinated system comprising food processing, protection from contamination and adulteration, transportation and storage, and distribution and consumption at optimal cost with a minimum environmental impact to the packed food commodity. Active packaging involves deliberate addition of the functional ingredients either in the film or the package headspace to preserve the food quality, improve safety and nutrition aspects, and enhance the shelf-life. In this review, recent advances in the fabrication of biopolymer-based films, their classification (biodegradable-, active-, and intelligent packaging films), advanced fabrication strategies (composite-, multilayer-, and emulsified films), and special functions induced by the biopolymers to the film matrix (mechanical-, water resistance and gas barrier-, and optical properties, and bioactive compounds reservoir) were briefly discussed. A summary of conclusions and future perspectives of biopolymer-based packaging films as advanced biomaterial in preserving the food quality, improving safety and nutrition aspects, and enhancing shelf-life of the products was proposed.

Active-intelligent and biodegradable sodium alginate films loaded with Clitoria ternatea anthocyanin-rich extract to preserve and monitor food freshness

The aim of this study was to develop and characterize sodium alginate films loaded with 10-40 % Clitoria ternatea extract (CTE) and apply to monitoring the quality of milk, pork and shrimp. Films loaded with CTE showed high light barrier capacity and improved tensile strength by 3.8 times over control films. The incorporation of CTE in alginate films improved the thermal stability of the materials due to intermolecular interactions and crosslinking of polymeric networks. The addition of 40 % of CTE generated films with antibacterial action against E. coli. The alginate films showed biodegradable characteristics in soil and beach sand in 15 days. The food simulant test revealed that the loaded films show good compatibility with aqueous and acidic foods due to the release of higher levels of polyphenols and anthocyanins. The films showed great colorimetric potential due to their ability to change color at different pH (pink-green), ammonia gas (blue-green) and sterilization process (blue-yellow). When the film loaded with 40 % CTE (F40) was applied to monitor the freshness of milk and meat products (shrimp and pork), its blue color changed to purple and green, respectively. Therefore, the F40 has great potential to be used as a biodegradable indicator of freshness.

Development of biomaterials based on plasticized polylactic acid and tea polyphenols for active-packaging application

Bioactive-packaging films based on polylactic acid (PLA), acetyl tributyl citrate (ATBC), and tea polyphenol (TP) were prepared by melt blending. Results of mechanical-property test revealed that adding ATBC and TP can significantly improve mechanical properties of PLA. The shift of CO to lower wavelengths in FTIR and the morphology of the films in SEM indicated physical or chemical interactions in the PLA/ATBC/TP films. The antioxidant, and antibacterial activities of the PLA/ATBC films increased dramatically (P<0.05) with increased TP amount. The antioxidant activity of the films with 1 % TP was equivalent to that of 300 mg/L l-ascorbic acid, whereas PLA/ATBC/TP films with 0.5 % and 1 % TP concentration were effective in inhibiting Staphylococcus aureus and Escherichia coli within almost 5 h (P<0.05). The PLA films changed from transparent to opaque and from yellow to red after combining with ATBC or TP, respectively. The overall migration of the films in 3 % acetic acid and 10 % ethanol did not exceed the overall migration limit. All these findings indicated potential of the PLA/ATBC/TP films in active-packaging application.

Preparation and Performance Characterization of a Composite Film Based on Corn Starch, κ-Carrageenan, and Ethanol Extract of Onion Skin

Using corn starch (CS) and κ-carrageenan(κC) as the raw material and active composite, respectively, films containing different concentrations of ethanol extract of onion skin were prepared. The effects of different concentrations of ethanol extract of onion skin (EEOS) on the physicochemical properties, as well as the antioxidant and antibacterial properties, of CS/κC films were also discussed. The addition of ethanol extract of onion skin inhibited the recrystallization of starch molecules in the composite films. It affected the microstructure of the composite films. The color of the composite films was deepened, the brightness was reduced, and the opacity was increased. Water vapor permeability increased, tensile strength decreased, and elongation at the break increased. The glass-transition temperature decreased. The clearance of DPPH radicals and ABTS cation radicals increased. Moreover, when the concentration of EEOS was 3%, the antioxidant effect of the films on oil was greatly improved and could effectively inhibit Staphylococcus aureus and Escherichia coli. The above results showed that adding ethanol extract of onion skin improved the physicochemical properties and biological activities of the CS/κC composite films, so CS/κC/EEOS composite films can be used as an active packaging material to extend food shelf-life. These results can provide a theoretical basis for the production and application of corn starch/κ-carrageenan/ethanol extract of onion skin composite films.

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.

Incorporation of gelatin and Fe2+ increases the pH-sensitivity of zein-anthocyanin complex films used for milk spoilage detection

In this study, blueberry anthocyanins, gelatin and Fe²⁺ were incorporated into zein matrix via electrospinning method to prepare colorimetric indicator films for monitoring milk freshness. Gelatin and Fe²⁺ were incorporated into the film to improve visual discrimination of indicator films' color changes in milk with different freshness degrees and in solution with pH 3-7. Results of SEM, FT-IR and XRD showed that there were intermolecular hydrogen bonds among components, which associated with the larger color difference of indicator films. UV-vis spectral analysis showed that blueberry anthocyanin solutions containing both gelatin and Fe²⁺ displayed the highest intensity absorption peaks. The optimal ability to distinguish the pH (3-7) of solutions was presented by the indicator film incorporating gelatin (1% (w/v)) and Fe²⁺ (0.07 mg/mL). Gelatin and Fe²⁺ increased the color-responsive sensitivity of the indicator film to pH. The film could be successfully used to detect the freshness of milk, whose color changes were visually perceivable: from purple black (fresh milk) to royal purple (spoiling milk) and then to violet red (spoiled milk). The color parameters (L*, a*, R, G and B) of the film revealed a high correlation with the pH/acidity of the milk during storage. The successful application of the indicator film embedding gelatin and Fe²⁺ for monitoring milk quality changes indicated that the addition of special substances could provide great potential for monitoring freshness and preparing intelligent packaging of food.

Innovative Food Packaging, Food Quality and Safety, and Consumer Perspectives

Packaging is an integral part of the food industry associated with food quality and safety including food shelf life, and communications from the marketing perspective. Traditional food packaging provides the protection of food from damage and storage of food products until being consumed. Packaging also presents branding and nutritional information and promotes marketing. Over the past decades, plastic films were employed as a barrier to keep food stuffs safe from heat, moisture, microorganisms, dust, and dirt particles. Recent advancements have incorporated additional functionalities in barrier films to enhance the shelf life of food, such as active packaging and intelligent packaging. In addition, consumer perception has influences on packaging materials and designs. The current trend of consumers pursuing environmental-friendly packaging is increased. With the progress of applied technologies in the food sector, sustainable packaging has been emerging in response to consumer preferences and environmental obligations. This paper reviews the importance of food packaging in relation to food quality and safety; the development and applications of advanced smart, active, and intelligent packaging systems, and the properties of an oxygen barrier. The advantages and disadvantages of these packaging are discussed. Consumer perceptions regarding environmental-friendly packaging that could be applied in the food industry are also discussed.

Recent advances in extraction, modification, and application of chitosan in packaging industry

Current environmental concerns fostered a strong interest in extracting polymers from renewable feedstocks. Chitosan, a second most abundant polysaccharide after cellulose, may prove to be a promising green material owing to its renewability, inherent biodegradablity, natural availability, non-toxicity, and ease of modification. This review is intended to comprehensively overview the recent developments on the isolation of chitosan from chitin, its modification and applications as a reinforcing candidate for food packaging materials, emphasizing the scientific underpinnings arising from its physicochemical properties, antimicrobial, antioxidant, and antifungal activities. We review various chitosan-reinforced composites reported in the literature and comprehensively present intriguing mechanical and other functional properties. We highlight the contribution of these mechanically robust and responsive materials to extend the shelf-life and maintain the qualities of a wide range of food commodities. Finally, we assess critical challenges and highlight future opportunities towards understanding the versatile applications of chitosan nanocomposites.

Recent advances in intelligent food packaging materials: Principles, preparation and applications

Traditionally, food packaging is used for improving food quality and providing consumers with descriptions of products. A new generation of intelligent ("smart") packaging materials is being developed to continuously monitor the properties of packaged foods and provide real-time information about their maturity, quality, and safety. In this paper, recent research in the development, properties, and applications of intelligent food packaging materials is summarized. Initially, we review the different sensing methods that can be used to detect alterations in food properties, such as those based on changes in time, temperature, humidity, oxygen levels, pH, chemical composition, or microbial contamination. The different approaches that can be used to design intelligent packaging materials are then highlighted, including films, bar codes, and labels. A number of applications of these packaging materials are then discussed to demonstrate their potential in the food industry. Finally, the challenges and future directions of food packaging are discussed.

Fabrication and characterization of an economical active packaging film based on chitosan incorporated with pomegranate peel

Antioxidant and antimicrobial chitosan (CS) films incorporated with different concentrations (0, 3, 6 and 9% w/w based on chitosan) of pomegranate peel powder (PPP) were prepared through a simple and low-cost process and characterized. The physicochemical property, antioxidant and antibacterial properties of the films were investigated. Results showed that incorporation with PPP increased the thickness, water solubility (WS), water vapor permeability (WVP), opacity and total phenolic content (TPC) of chitosan films, but decreased the moisture content (MC) and mechanical property. Fourier transform infrared (FTIR) spectroscopy indicated the formation of hydrogen bonds between chitosan and PPP. In addition, scanning electron microscopy (SEM) analysis presented that microstructural attributes of chitosan film changed by enriching with pomegranate peel. The films with concentrations of PPP at 6 and 9% presented great ultraviolet-visible light barrier properties. Moreover, the antioxidant ability of films with PPP was significantly increased compared to the chitosan film. The addition of PPP also promoted the antibacterial capacity of the control film. These results revealed that incorporation of PPP in chitosan film could fabricate an economical active film with antioxidant and antibacterial properties, and which had the potential for developing food-grade packaging material.

Natural and Synthetic Flavylium-Based Dyes: The Chemistry Behind the Color

Flavylium compounds are a well-known family of pigments because they are prevalent in the plant kingdom, contributing to colors over a wide range from shades of yellow-red to blue in fruits, flowers, leaves, and other plant parts. Flavylium compounds include a large variety of natural compound classes, namely, anthocyanins, 3-deoxyanthocyanidins, auronidins, and their respective aglycones as well as anthocyanin-derived pigments (e.g., pyranoanthocyanins, anthocyanin-flavan-3-ol dimers). During the past few decades, there has been increasing interest among chemists in synthesizing different flavylium compounds that mimic natural structures but with different substitution patterns that present a variety of spectroscopic characteristics in view of their applications in different industrial fields. This Review provides an overview of the chemistry of flavylium-based compounds, in particular, the synthetic and enzymatic approaches and mechanisms reported in the literature for obtaining different classes of pigments, their physical-chemical properties in relation to their pH-dependent equilibria network, and their chemical and enzymatic degradation. The development of flavylium-based systems is also described throughout this Review for emergent applications to explore some of the physical-chemical properties of the multistate of species generated by these compounds.

Multicolor PEGDA/LCNF Hydrogel in the Presence of Red Cabbage Anthocyanin Extract

Colorimetric indicator gels were developed by incorporating anthocyanin (AC) obtained from red cabbage into poly (ethylene glycol) diacrylate (PEGDA)-based hydrogel containing lignocellulose nanofiber (LCNF). The PEGDA-based hydrogel was prepared by mixing all of the mentioned components at the specific composition, and the hydrogels were cured under UV light (245 nm) for 1 min. The pH-response, UV absorption, swelling ratio, and mechanical properties of PEGDA/LCNF were determined. It was further found that PEGDA and LCNF mount play an important role in adjusting the mechanical properties of PEGDA/LCNF. In general, the presence of LCNF improved the mechanical properties and swelling ratio of PEGDA. The incorporation of red cabbage anthocyanin into the PEGDA/LCNF film showed multicolor response when specific pH buffers were introduced. Based on the multicolor response of PEGDA/LCNF/CA, this gel film indicator can be developed as a food freshness indicator that focuses on the detection of ammonia and amine compound.

Recent development on physical and biological properties of chitosan-based composite films with natural extracts: A review

Being credited with the most extensively studied polysaccharide polymer and promising candidate for versatile applications, chitosan has proved to be a standalone material with loads of diversified properties in various structural forms such as blends and composites. Considering the abundance of this biopolymer and its non-toxic nature, exploiting chitosan offers two-folded benefits – environment friendliness and fabrication as per the need. Alkaline deacetylation of chitin produces chitosan as a polymer that can be tuned to a great extent as per the requirement by altering the degree of deacetylation (DDA) and molecular weight (MW). This biopolymer has been widely investigated for potential application in the food and biomedical fields due to its antimicrobial and antibacterial properties. Chitosan based composite films incorporated with different natural extracts have shown significant enhancement in the physical and biological activities as reported by different studies. The current study reviews recent developments and investigations of chitosan based biocomposite films incorporated with different natural extracts emphasizing on the improvement of physical and biological properties and its applications.

Chitosan-poly(vinyl alcohol) intelligent films fortified with anthocyanins isolated from Clitoria ternatea and Carissa carandas for monitoring beverage freshness

Biodegradable chitosan-poly(vinyl alcohol) films containing natural anthocyanin-rich extracts were prepared using solvent casting method and employed as intelligent indicators for monitoring beverages freshness. The surface and cross-sectional scanning electron micrograph indicated a compact structure for the intelligent films, whereas the atomic force micrograph indicated a 16.22 and 20.31 nm increase in surface roughness for Clitoria ternatea and Carissa carandas extract incorporated films, respectively. Moreover, the test films demonstrated enhanced radical scavenging efficacy. The extracts and anthocyanin incorporated films presented excellent colorimetric changes at pH 2 to 8. In addition, the C. ternatea test films showed changes in color for juice stored at 25 °C after 72 h. Photo-degradability results indicated stability of test films stored in dark at 4 °C and 25 °C, whereas leaching study indicated the release of ≤2.0% anthocyanin after 24 h. The cytocompatibilty assay showed that the test and control films were biocompatible with a viability of >80% on HaCat cells. The results demonstrated that the incorporation of anthocyanins-rich extracts into chitosan-poly(vinyl alcohol) did not significantly interfere with the films properties (p > 0.05). The natural anthocyanin incorporated films demonstrated good pH sensing property that could be further explored for monitoring of beverages freshness.