Make your packaging colorful and multifunctional: The molecular interaction and properties characterization of natural colorant-based films and their applications in food industry

Endocrine-disrupting effects of 24 colorants used in food contact materials: In vitro and in silico studies

Current research on endocrine-disrupting effects of colorants utilized in food contact materials (FCMs) ramains limited. This study investigated these effects through in vitro cell models and in silico toxicological models. A total of 24 synthetic colorants were collected from the Chinese market, including azo, anthraquinone, heterocyclic and fused-ring ketones, and phthalocyanines. Their endocrine-disrupting effects mediated by estrogen and androgen receptors were evaluated using an in vitro dual-luciferase reporter gene assay. Results showed no estrogenic or anti-estrogenic effects or androgenic activity in the colorants. However, three colorants, C.I. Pigment Red 177, C.I. Pigment Orange 71, and C.I. Pigment Blue 15, elicited anti-androgenic effects with 20 % relative inhibitory concentrations (RIC20) of 13.08, 40.52, and 33.27 μg/mL, respectively. In addition, in silico toxicological models predicted the endocrine-disrupting activity of the 24 colorants, showing predictive accuracy ranging from 35 % to 100 % consistency with in vitro experimental outcomes. Molecular docking revealed strong binding affinity and mechanisms of interaction between three colorants and the human androgen receptor. In summary, this study combined in vitro experiments and in silico toxicological models to investigate the endocrine-disrupting effects of organic colorants with different structural types, providing new insights perspective on health risks associated with their use in FCMs.

Real-Time Monitoring and Rapid Determination of Pork Freshness Using a Colorimetric Sensor Array Based on Porphyrin and pH Indicator Ligand Combination

This study presents the development of a colorimetric sensor array (CSA) that combines pH indicators with porphyrin solutions to create a sensitive and stable sensor for monitoring pork freshness. Four pH indicators─bromophenol blue, bromocresol green, bromocresol violet, and chlorophenol red─were chosen for their ability to detect volatile gases produced during pork spoilage. Color changes were quantified by extracting grayscale values, and various porphyrins, including TPPNi, TPPMnCl, and TPPCu, were screened for their interactions with the pH indicators. Principal component analysis was used to determine the optimal concentration of the porphyrin solution. The CSA was then constructed by combining the four pH indicators with the selected porphyrins, resulting in an average stability improvement of 21.94%, 23.59%, 28.84%, and 23.31%, respectively. The occurrence of coordination is verified by Fourier transform infrared (FTIR), and theoretical calculations are applied to explain the possible reasons for the increased stability. The CSA was tested on pork samples stored for different periods, and a partial least squares regression model was built using grayscale data to predict freshness. Furthermore, storage experiments were conducted to evaluate the CSA's stability over 3, 7, and 15 days, and the retention of color in CSA was 99.02%, 99.01%, and 98.84%, respectively. The models achieved 98.89% average accuracy (n = 30 samples) in predicting the freshness grades of pork samples from different batches and in assessing the stability of the CSA, demonstrating its potential as a reliable tool for rapid and accurate pork freshness discrimination.

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

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

From nature to nanotech: Harnessing the power of electrospun polysaccharide-based nanofibers as sustainable packaging

Today, the applications of natural polysaccharide-based nanofibers are growing in drug delivery and food industries. They also showed their capability as packaging due to biodegradability, mechanical strength, barrier properties, thermal stability, antioxidant, and antimicrobial features. Natural polysaccharides come from different sources, such as plants, microbes, and animals. Natural polysaccharide-based nanofibers can be considered sustainable packaging in contrast to plastic packaging due to their safety and biodegradability. Smart packaging is a new trend in packaging materials, and natural polysaccharides can be applied as smart packaging. They can work as an indicator that confirms food health in food packaging. Electrospinning is one of the most used methods for the fabrication of nanofibers, and it can also be used for the fabrication of natural polysaccharide nanofibers. This method can be scaled up and used to fabricate nanofibers on a large scale. This paper will review recent studies on natural polysaccharide-based nanofiber as packaging materials and their benefits. We also discuss the challenges and limitations of their scale-up and electrospinning process. Furthermore, we will discuss the future perspective of natural polysaccharide-based nanofiber as a new sustainable packaging.

Absorption, Steady-State Fluorescence and Solvent Effect Studies of Fluorescent Haloarchaeal Bacterioruberin

Fluorescence characterization of halophilic archaeal C50 carotenoid-bacterioruberin extracts was investigated using UV/Vis and steady-state fluorescence spectrophotometry in solvents with different polarity. Different extracts showed maximum absorption and fluorescence wavelengths between 369-536 nm and 540-569 nm. Stokes' shifts varied between 50-79 nm depending on the solvent. In particular, water extract showed significant Stokes' shifts with the increase in polarity index; however, fluorescence wavelength (band position) and shape were found to be independent of polarity. According to the obtained results, it is thought that bacterioruberin will be a new alternative material with increasing applications in optics, biosensor/chemosensor, biotechnology, analytical chemistry and nanotechnology due to its fluorescence properties.

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

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

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

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

A review on improving the sensitivity and color stability of naturally sourced pH-sensitive indicator films

Naturally sourced pH-sensitive indicator films are of interest for real-time monitoring of food freshness through color changes because of their safety. Therefore, natural pigments for indicator films are required. However, pigment stability is affected by environmental factors, which can in turn affect the sensitivity and color stability of the pH-sensitive indicator film. First, natural pigments (anthocyanin, betalain, curcumin, alizarin, and shikonin) commonly used in pH-sensitive indicator films are presented. Subsequently, the mechanisms behind the change in pigment color under different pH environments and their applications in monitoring food freshness are also described. Third, influence factors, such as the sources, types, and pH sensitivity of pigments, as well as environmental parameters (light, temperature, humidity, and oxygen) of sensitivity and color stability, are analyzed. Finally, methods for improving the pH-sensitive indicator film are explored, encapsulation of natural pigments, incorporation of a hydrophobic film-forming matrix or function material, and protective layer have been shown to enhance the color stability of indicator films, the addition of copigments or mental ions, blending of different natural pigments, and the utilization of electrospinning have been proved to increase the color sensitivity of indicator films. This review could provide theoretical support for the development of naturally sourced pH-sensitive indicator films with high stability and sensitivity and facilitate the development in the field of monitoring food freshness.

Smart food packaging: Recent advancement and trends

Food packaging plays an important role in protecting the safety and quality of food products and enables communication with consumers. With the improved consumers' awareness of safety and quality of food products, the changes in consumers' lifestyle, and the growing demand for transparency of food products along the supply chain, food packaging technologies have evolved from only providing the four fundamental functions (i.e., protection and preservation, containment, communication and marketing, and convenience) to possessing additional functions including active modification of the inside microenvironment (i.e., active packaging) and monitoring the safety and quality of products in real-time (i.e., intelligent packaging). A variety of active and intelligent packaging systems have been developed to better protect and monitor the quality and safety of food products during the past several decades. Recently, advanced versions of smart packaging technologies, such as smart active packaging and smart intelligent packaging technologies have also been developed to enhance the effectiveness of conventional smart packaging systems. Additionally, smart packaging systems that harvest the advantages of both active packaging and intelligent packaging have also been developed. In this chapter, a brief overview of smart packaging technologies was provided. Specific technologies being covered include conventional smart packaging technologies and advanced smart packaging technologies, such as smart active packaging, smart intelligent packaging and dual-function smart packaging.

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

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

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.

Coffee Silverskin Cellulose-Based Composite Film with Natural Pigments for Food Packaging: Physicochemical and Sensory Abilities

To promote a circular economy, the use of agricultural by-products as food packaging material has steadily increased. However, designing food packaging films that meet consumers' preferences and requirements is still a challenge. In this work, cellulose extracted from coffee silverskin (a by-product of coffee roasting) and chitosan were combined with different natural pigments (curcumin, phycocyanin, and lycopene) to generate a variety of composite films with different colors for food packaging. The physicochemical and sensory properties of the films were evaluated. The cellulose/chitosan film showed favorable mechanical properties and water sensitivity. Addition of natural pigments resulted in different film colors, and significantly affected the optical properties and improved the UV-barrier, swelling degree, and water vapor permeability (WVP), but there were also slight decreases in the mechanical properties. The various colored films can influence the perceived features and evoke different emotions from consumers, resulting in films receiving different attraction and liking scores. This work provides a comprehensive evaluation strategy for coffee silverskin cellulose-based composite films with incorporated pigments, and a new perspective on the consideration of the hedonic ratings of consumers regarding bio-based films when designing food packaging.

New Functional Foods with Cactus Components: Sustainable Perspectives and Future Trends

The growing interest in a healthy lifestyle has contributed to disseminating perspectives on more sustainable natural resource management. This review describes promising aspects of using cacti in the food industry, addressing sustainable, nutritional, and functional aspects of the plant's production. Our study provides an overview of the potential of cacti for the food industry to encourage the sustainable cultivation of underutilized cactus species and their commercial exploitation. The commercial production of cacti has advantages over other agricultural practices by mitigating damage to ecosystems and encouraging migration to sustainable agriculture. The application of cactus ingredients in food development has been broad, whether in producing breads, jellies, gums, dyes, probiotics, and postbiotic and paraprobiotic foods. However, in the field of probiotic foods, future research should focus on technologies applied in processing and researching interactions between probiotics and raw materials to determine the functionality and bioactivity of products.

The use of a novel smartphone testing platform for the development of colorimetric sensor receptors for food spoilage

This work presents a novel smartphone testing platform for the validation of colorimetric sensor receptors (CSRs) in the form of layers that enables reliable and straightforward determination of their color change in a closed system using a commercially available color sensor. The food-compatible model CSR used for the method development was made of black carrot extract and ethyl cellulose. The colorimetric responses were studied in detail for NH₃, dimethylamine (DMA), and trimethylamine (TMA) by analyzing changes in the value of the total color difference (ΔE) with the increasing logarithm of the mass concentration (log γ) of the analytes. The method was partially validated for the detection limit (LOD), the limit of quantification, sensitivity, and linear γ range. The fastest reaction times were obtained for the NH₃ analyte, while the calculated LOD values were quite similar (1.48 mg L^-1 for NH₃, 1.55 mg L^-1 for DMA, and 1.58 mg L^-1 for TMA). The applicability of CSRs was shown for different types of muscle food. Frozen (boneless and skinless) hake fillets were used for additional experimental work in which the color changes of the CSRs were correlated with the values of the total volatile basic nitrogen (TVB-N) and the total counts of aerobic and anaerobic microorganisms. The developed testing platform shows great promise for the development of CSRs that define the quality of a broad variety of muscle food.

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.

Development of edible films by incorporating nanocrystalline cellulose and anthocyanins into modified myofibrillar proteins

In this study, a myofibrillar protein (MP) system was used to investigate the film properties changes by adjusting the intensity of the interaction of proteins with other food components. The structure and rheological properties of several film-forming solutions were then determined. Furthermore, the structure of these composite films was examined using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The smooth and uniform surface acquired by scanning electron microscopy (SEM) substantiated the increased compatibility and continuity observed for films with greater food component interaction. In addition, the MP-based edible films with stronger food component interactions (the MP-Myr/ANT/NCC group) displayed superior mechanical (tensile strength: 6.68 MPa, elongation at break: 94.43%), water vapor barrier (10.01 × 10^-9 g m^-1 s^-1 Pa^-1), and ammonia sensitivity (total color difference: 17.00) capabilities compared to those of the other groups (the MP/ANT/NCC, MP-Lut/ANT/NCC, and MP-Que/ANT/NCC groups).

The physiochemical and photodynamic inactivation properties of corn starch/erythrosine B composite film and its application on pork preservation

This study explored the effect of erythrosine B (EB) as a photosensitizer in corn starch (CS) film and its physicochemical properties and photodynamic bacteriostatic ability against Staphylococcus aureus, Escherichia coli, and Salmonella both in vitro and inoculated on pork under the irradiation of D65 light-emitting diode (LED) (400-800 nm). The study revealed that the physiochemical properties of CS films: moisture content, water solubility, and water vapor transmission were improved with the addition of EB. In addition, the elasticity and the thermal stability of the film were enhanced. The results showed that the CS-EB films stimulated a maximum of 26.36 μg/mL hydrogen peroxide and 74.5 μg/g hydroxyl radical under irradiation. The CS composite films with a 5 % concentration of EB inhibited the bacterial growth by 4.7 Log CFU/mL in vitro after 30 min of illumination, and 2.4 Log CFU/mL on the pork samples under the same experimental condition. Moreover, the antibacterial ability was enhanced with the increase in EB concentration. Overall, the CS-EB composite films can inhibit the growth of bacteria through photodynamic inactivation and has the potential to become a new type of environmentally friendly packaging material.

Recent Advances in Bio-Based Smart Active Packaging Materials

The shortage of oil resources is currently a global problem. The use of renewable resources instead of non-renewable ones has become a hot topic of research in the eyes of scientists. In the food industry, there is a lot of interest in bio-based smart active packaging that meets the concept of sustainability and ensures safety. The packaging has antibacterial and antioxidant properties that extend the shelf life of food. Its ability to monitor the freshness of food in real time is also beneficial to consumers’ judgement of food safety. This paper summarises the main raw materials for the preparation of bio-based smart active packaging, including proteins, polysaccharides and composite materials. The current status of the preparation method of bio-based smart active packaging and its application in food preservation is summarised. The future development trend in the field of food packaging is foreseen, so as to provide a reference for the improvement of bio-based smart active packaging materials.