Development of a prototype of a colourimetric temperature indicator for monitoring food quality

Biopolymer-based solutions for enhanced safety and quality assurance: A review

The improper disposal of petroleum-based plastics has been associated with detrimental environmental consequences, such as the proliferation of microplastic pollution and increased emissions of greenhouse gases (GHGs). Consequently, biopolymers have emerged as a highly regarded alternative due to their environmental-friendly attributes and versatile range of applications. In response to consumer demands for safer food options, sustainable packaging, and escalating environmental concerns, the food sector is increasingly adopting biopolymers. Further, in the recent decade, the usage of active or functional biopolymers has evolved into smart biopolymers that can transmit real-time data to consumers. This review covers key topics such as antimicrobial and biodegradable packaging, edible coatings and films, incorporation of scavengers and bioactive substances that prolong the shelf life and guard against moisture and microbial contamination. The paper also discusses the development of edible cutlery as a sustainable substitute for plastic, the encapsulation of bioactive substances within biopolymers, 3-D food printing for regulated nutrition delivery and thickening and gelling agents that improve food texture and stability. It also discusses the integration of smart polymer functions, demonstrating their importance in guaranteeing food safety and quality, such as biosensing, pH and gas detection, antibacterial characteristics, and time-temperature monitoring. By shedding light on market trends, future scope, and potentialities, this review aims to elucidate the prospects of utilizing biopolymers to address sustainability and quality concerns within the food industry effectively.

Smart colorimetric indicator films prepared from chitosan and polyvinyl alcohol with high mechanical strength and hydrophobic properties for monitoring shrimp freshness

This work aimed to develop and characterize a colorimetric indicator films based on chitosan (CS), polyvinyl alcohol (PVA), and shikonin (SKN) from radix Lithospermi by casting method. The prepared films can serve as smart packaging for monitoring shrimp freshness which having excellent antimicrobial and antioxidant activity. The shikonin containing films have better hydrophobicity, barrier properties, and tensile strength. The release kinetics analysis shows that the loading amount causes a prolonged release of SKN from the prepared films. Increasing SKN in the CS/PVA film from 1 wt% to 2 wt% improved antibacterial effect for 24 h. Additionally, pH-sensitive color shifts from reddish (pH 2) to purple-bluish (pH 13) were visually seen in shikonin based solutions as well as films. The CS/PVA/SKN film detected shrimp deterioration at three temperatures (25, -20, and 4 °C) through color change. This study introduces a favorable approach for smart packaging in the food industry using multifunctional films.

Vendors' handling practices of edible long-horned grasshoppers (Ruspolia differens) products and implications on microbial safety

Edible grasshopper, Ruspolia ruspolia, has nutritional and cherished cultural and economic importance to people from diverse cultures, particularly in over 20 African countries. It is consumed at home or commercially traded as sautéed, deep-fried, or boiled products. However, there is limited information on the hygiene practices of the vendors and the implications on the microbial safety of the final product. This research aimed at assessing the food safety knowledge, handling practices and shelf life of edible long-horned grasshopper products among vendors and the microbial safety of ready-to-eat products sold in 12 different markets in Uganda. Samples of raw, deep-fried and boiled grasshoppers were randomly collected from 74 vendors (62% street and 38% market vendors) and subjected to microbial analysis. Over 85% of the vendors surveyed had no public health food handler's certificate and >95% had limited post-harvest handling knowledge. Total aerobic bacteria (7.30-10.49 Log10 cfu/g), Enterobacteriaceae (5.53-8.56 Log10 cfu/g), yeasts and molds (4.96-6.01 Log10 cfu/g) total counts were significantly high and above the acceptable Codex Alimentarius Commission and Food Safety Authority of Ireland (FSAI) limits for ready-to-eat food products. Eight key pathogenic bacteria responsible for foodborne diseases were detected and these isolates were characterized as Bacillus cereus, Hafnia alvei, Serratia marcescens, Staphylococcus aureus, S. xylosus, S. scuiri, S. haemolyticus, and Pseudomonas aeruginosa. Findings from this study highlight the urgent need to create local and national food safety policies for the edible grasshopper "nsenene" subsector to regulate and guide street and market vending along the value chain, to prevent the transmission of foodborne diseases to consumers.

Irreversible colorimetric bio-based curcumin bilayer membranes for smart food packaging temperature control applications

Research into innovative food safety technologies has led to the development of smart packaging with embedded chemical sensors that can monitor food quality throughout the supply chain. Thermochromic materials (TM), which are able to dynamically change colour in response to temperature fluctuations, have proven to be reliable indicators of food quality in certain environments. Natural colourants such as curcumin are becoming increasingly popular for smart packaging due to their low toxicity, environmental friendliness and ability to change colour. The innovation in this research lies in the production of a bio-based bilayer membrane specifically designed for irreversible temperature monitoring. Membrane A was prepared by dissolving cellulose acetate and curcumin in acetone at room temperature, with glycerol serving as a plasticiser. At the same time, membrane B was carefully formulated by dissolving cellulose acetate and triethanolamine in acetone, with sorbitol as plasticiser. The preparation of these different membranes revealed a remarkable event: a gradual and irreversible colour transition from an initial yellow to a brick-red hue after 24 hours of storage at 25 °C. The chemical structure and morphological analyses of the membranes were performed using several techniques, including FTIR, DSC and SEM. The membrane labels were adhered to aluminium cans and their colorimetric response was observed over a period of 10 days. Minimal colour variations were observed, confirming the reproducibility and stability of the curcumin-based membranes as temperature sensors.

A visual bi-layer indicator based on mulberry anthocyanins with high stability for monitoring Chinese mitten crab freshness

In this study, a bilayer film (BIF) was fabricated to improve the stability of an anthocyanin-based freshness indicator film. The sensor layer consists of gellan gum (GG) and mulberry anthocyanin (MAE) for freshness indication. The oxygen barrier layer was constructed from chitosan (CS), polyvinyl alcohol (PVA), sodium alginate (SA), and pullulan (Pu) to the protection of MAE from oxidation. The highest antioxidant activity of BIF was 91.28 %. BIF was used to monitor the Chinese mitten crab freshness. The total volatile basic nitrogen (TVB-N) level was increased to 31.23 mg/100 g on day 8, and the color of the indicator presented a visible change from pink to dark green. The acquired results revealed a good correlation between TVB-N, pH, and color change of the indicator. The research indicated that the BIF was applied for freshness monitoring of Chinese mitten crab and displayed significant color changes that would be effective in commercial environments.

pH-dependent color response of cellulose-based time-temperature indicators impregnated with red cabbage extract

Color-based time-temperature indicators (TTIs) can show the time and temperature changes of an environment with a visually recognizable color change. Made from natural dyes, these TTIs are simple, inexpensive and sustainable. In this study, cellulose-based TTI labels were prepared with red cabbage extract of pH2, pH7 and pH9 to determine how pH alter the response of the labels to time and temperature changes. This study also aimed to determine the relationship between color change and time at different temperatures. The color responses of the labels were followed spectrophotometrically by measuring the CIE Lab color coordinates and by giving the total color difference at 4 °C, 23 °C, 40 °C, 80 and 100 °C after increments of time. The best fitting linear or nonlinear regression models of the CIE Lab coordinates, total color difference and time data as a function of temperature were also determined. The labels prepared with red cabbage extract at different pH behaved differently. Opposite to expectations, the acidic, pink colored labels did not have the highest color stability. Our finding was, that the label prepared with the acidic red cabbage extract is the most suitable as time-temperature label for indicating long-term temperature storage and the label prepared with the neutral red cabbage extract is the most suitable as time-temperature label for indicating short-term storage by color change. According to the results the color changes of the labels are predictable with the fitted models with a correlation coefficient between 0.96 and 1.

Polysaccharide-Based Biodegradable Films: An Alternative in Food Packaging

Packaging can mitigate the physical, chemical, and microbiological phenomena that affects food products’ quality and acceptability. However, the use of conventional packaging from non-renewable fossil sources generates environmental damage caused by the accumulation of non-biodegradable waste. Biodegradable films emerge as alternative biomaterials which are ecologically sustainable and offer protection and increase food product shelf life. This review describes the role of biodegradable films as packaging material and their importance regarding food quality. The study emphasizes polysaccharide-based biodegradable films and their use in foods with different requirements and the advances and future challenges for developing intelligent biodegradable films. In addition, the study explores the importance of the selection of the type of polysaccharide and its combination with other polymers for the generation of biodegradable films with functional characteristics. It also discusses additives that cause interactions between components and improve the mechanical and barrier properties of biodegradable films. Finally, this compilation of scientific works shows that biodegradable films are an alternative to protecting perishable foods, and studying and understanding them helps bring them closer to replacing commercial synthetic packaging.

Colorimetric Indicators Based on Anthocyanin Polymer Composites: A Review

This review explores the colorimetric indicators based on anthocyanin polymer composites fabricated in the last decade, in order to provide a comprehensive overview of their morphological and compositional characteristics and their efficacy in their various application fields. Notably, the structural properties of the developed materials and the effect on their performance will be thoroughly and critically discussed in order to highlight their important role. Finally, yet importantly, the current challenges and the future perspectives of the use of anthocyanins as components of colorimetric indicator platforms will be highlighted, in order to stimulate the exploration of new anthocyanin sources and the in-depth investigation of all the possibilities that they can offer. This can pave the way for the development of high-end materials and the expansion of their use to new application fields.

A Review of Stimuli-Responsive Smart Materials for Wearable Technology in Healthcare: Retrospective, Perspective, and Prospective

In recent years thanks to the Internet of Things (IoT), the demand for the development of miniaturized and wearable sensors has skyrocketed. Among them, novel sensors for wearable medical devices are mostly needed. The aim of this review is to summarize the advancements in this field from current points of view, focusing on sensors embedded into textile fabrics. Indeed, they are portable, lightweight, and the best candidates for monitoring biometric parameters. The possibility of integrating chemical sensors into textiles has opened new markets in smart clothing. Many examples of these systems are represented by color-changing materials due to their capability of altering optical properties, including absorption, reflectance, and scattering, in response to different external stimuli (temperature, humidity, pH, or chemicals). With the goal of smart health monitoring, nanosized sol-gel precursors, bringing coupling agents into their chemical structure, were used to modify halochromic dyestuffs, both minimizing leaching from the treated surfaces and increasing photostability for the development of stimuli-responsive sensors. The literature about the sensing properties of functionalized halochromic azo dyestuffs applied to textile fabrics is reviewed to understand their potential for achieving remote monitoring of health parameters. Finally, challenges and future perspectives are discussed to envisage the developed strategies for the next generation of functionalized halochromic dyestuffs with biocompatible and real-time stimuli-responsive capabilities.

The Emergence of Edible and Food-Application Coatings for Food Packaging: A Review

Food packaging was not as important in the past as it is now, because the world has more people but fewer food resources. Food packaging will become more prevalent and go from being a nice-to-have to an essential feature of modern life. Food packaging has grown to be an important industry sector in today’s world of more people and more food. Food packaging innovation faces significant challenges in extending perishable food products’ shelf life and contributing to meeting daily nutrient requirements as people nowadays are searching for foods that offer additional health advantages. Modern food preservation techniques have two objectives: process viability and safe, environmentally friendly end products. Long-term storage techniques can include the use of edible coatings and films. This article gives a succinct overview of the supplies and procedures used to coat food products with conventional packaging films and coatings. The key findings summarizing the biodegradable packaging materials are emphasized for their ability to prolong the freshness and flavor of a wide range of food items; films and edible coatings are highlighted as viable alternatives to traditional packaging methods. We discuss the safety concerns and opportunities presented by applying edible films and coatings, allowing it to be used as quality indicators for time-sensitive foods.

Synthesis and Physicochemical Characterization of Polymer Film-Based Anthocyanin and Starch

Colorimetric indicators, used in food intelligent packaging, have enormous promise for monitoring and detecting food quality by analyzing and interpreting the quality data of packaged food. Hence, our study developed and characterized a biopolymer film based on starch and anthocyanin for prospective meat freshness monitoring applications. The developed film was morphologically characterized using different morphology instruments to identify the interaction between anthocyanin and starch. The color differences of the proposed film in response to different pH buffers have also been investigated. The combination of anthocyanin and starch produces a smooth and homogenous surface with an intermolecular hydrogen bond that increases the biopolymer's wavelength. The film indicated bright red at pH 2.0-6.0, bluish-grey at pH 7.0-11.0, and yellowish-green above 11.0 that the naked eye can see. The indicator film shows high sensitivity toward pH changes. The inclusion of anthocyanin increases the biopolymer film's thickness and crystalline condition with low humidity, water solubility, and swelling values. As a result, the polymer film can be employed in the food industry as an affordable and environmentally friendly indication of meat freshness.

Bio-nano-composites containing at least two components, chitosan and zein, for food packaging applications: A review of the nano-composites in comparison with the conventional counterparts

Both chitosan and zein are safe industrial biopolymers for the 21St century, respecting environmentally concerns. This review mainly is focused on preparations, properties and applications of a promising food packaging material, chitosan-zein nano-composite (NC). The properties and applications of the NCs were compared with their conventional counterparts. The structure of chitosan- zein composites was proposed. A procedure for preparations of conventional and nano zein-chitosan composites was proposed. The sizes of composites depend on molecular weight of chitosan and zein, the ratio of chitosan/zein, and pH of chitosan-zein solutions. The NCs had superior mechanical, antimicrobial, antioxidant, and barrier properties compared with the conventional ones. The properties of the composites were further improved by introduction of bioactive compounds, fillers or plasticizers. The composites have potential to employ as coatings/packaging materials to protect mushroom, meats, and fresh fruits and vegetables.

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.

Recent Advances in the Development of Smart and Active Biodegradable Packaging Materials

Interest in the development of smart and active biodegradable packaging materials is increasing as food manufacturers try to improve the sustainability and environmental impact of their products, while still maintaining their quality and safety. Active packaging materials contain components that enhance their functionality, such as antimicrobials, antioxidants, light blockers, or oxygen barriers. Smart packaging materials contain sensing components that provide an indication of changes in food attributes, such as alterations in their quality, maturity, or safety. For instance, a smart sensor may give a measurable color change in response to a deterioration in food quality. This article reviews recent advances in the development of active and smart biodegradable packaging materials in the food industry. Moreover, studies on the application of these packaging materials to monitor the freshness and safety of food products are reviewed, including dairy, meat, fish, fruit and vegetable products. Finally, the potential challenges associated with the application of these eco-friendly packaging materials in the food industry are discussed, as well as potential future directions.

Monitoring the infection process of Rhizopus stolonifer on strawberry fruit during storage using films based on chitosan/polyvinyl alcohol/polyvinylpyrrolidone and plant extracts

Different formulations based on nanoparticles of chitosan-plant extracts were evaluated to detect the infection process from the earliest stage of the fungus Rhizopus stolonifer on strawberry fruit during storage. Chitosan/polyvinyl alcohol (Ch/PVA) and chitosan/polyvinylpyrrolidone (Ch/PVP) films enriched with nanoparticles (NPs) of chitosan blended with plant extracts were prepared. They were placed inside a plastic package containing inoculated fruits and stored at 25 °C for 72 h. The thickness values of the films were in the range of 0.10 to 0.25 mm. All samples showed a maximum absorbance peak of about 300-320 nm; however, the Ch/PVP films enriched with NPs of chitosan and 10% of radish extract had an evident decrease in the optical absorbance as the fungal infection progressed. Additionally, as observed by scanning electron microscopy, the cross-section and surface morphology of films were not modified during storage, and the growth of R. stolonifer was evident after 48 h. Therefore, the Ch/PVP films enriched with chitosan NPs blended with 10% radish extract could be a reliable indicator of this fungus's growth.

Review on Polysaccharides Used in Coatings for Food Packaging Papers

Paper and board show many advantages as packaging materials, but the current technologies employed to obtain adequate barrier properties for food packaging use synthetic polymers coating and lamination with plastic or aluminium foils—treatments which have a negative impact on packaging sustainability, poor recyclability and lack of biodegradability. Recently, biopolymers have attracted increased attention as paper coatings, which can provide new combinations in composite formulas to meet the requirements of food packaging. The number of studies on biopolymers for developing barrier properties of packaging materials is increasing, but only a few of them are addressed to food packaging paper. Polysaccharides are viewed as the main candidates to substitute oil-based polymers in food paper coating, due to their film forming ability, good affinity for paper substrate, appropriate barrier to gases and aroma, and positive effect on mechanical strength. Additionally, these biopolymers are biodegradable, non-toxic and act as a matrix for incorporation additives with specific functionalities for coated paper (i.e., active-antimicrobial properties). This paper presents an overview on the availability and application of polysaccharides from vegetal and marine biomass in coatings for foods packaging paper. The extraction methods, chemical modification and combination routes of these biopolymers in coatings for paper packaging are discussed.

Applicability of Agro-Industrial By-Products in Intelligent Food Packaging

Nowadays, technological advancement is in continuous development in all areas, including food packaging, which tries to find a balance between consumer preferences, environmental safety, and issues related to food quality and control. The present paper concretely details the concepts of smart, active, and intelligent packaging and identifies commercially available examples used in the food packaging market place. Along with this purpose, several bioactive compounds are identified and described, which are compounds that can be recovered from the by-products of the food industry and can be integrated into smart food packaging supporting the “zero waste” activities. The biopolymers obtained from crustacean processing or compounds with good antioxidant or antimicrobial properties such as carotenoids extracted from agro-industrial processing are underexploited and inexpensive resources for this purpose. Along with the main agro-industrial by-products, more concrete examples of resources are presented, such as grape marc, banana peels, or mango seeds. The commercial and technological potential of smart packaging in the food industry is undeniable and most importantly, this paper highlights the possibility of integrating the by-products derived compounds to intelligent packaging elements (sensors, indicators, radio frequency identification).

Disposable Colorimetric Paper-Based Probe for the Detection of Amine-Containing Gases in Aquatic Sediments

Amine compounds are considered highly important in environmental pollution, industrial, and medicinal fields. The objective of this work was to develop a disposable, highly accurate, highly selective, and low-cost paper-based probe through the combination of color change of seven pH indicators for the detection of amine compounds in the gaseous state. The probe was designed with seven rings which were printed using the wax-printing technique and colored with different pH indicators. The colors of the probe were analyzed using red, green, and blue (RGB) values extracted from the images obtained with a homemade smartphone application. The chemometric tools, principal component analysis, and hierarchical cluster analysis methods were adapted to further classify amine gases. The colorimetric probe showed an excellent capability for detecting the amines with high accuracy, prompt response, and high selectivity. These dye arrays have been proven to detect ethanolamine (NH₂CH₂CH₂OH), dimethylamine ((CH₃)₂NH), and trimethylamine ((CH₃)₃N) gases at parts per million scale.

Study of chitosan with different degrees of acetylation as cardboard paper coating

The biodegradability of chitosan is significant for packaging systems. Another relevant property of chitosan is its degree of acetylation (DA), which affects other properties, such as crystallinity and hydrophobicity. The DA can be modulated by chitin deacetylation or even chitosan reacetylation. The novelty of this paper is the application of reacetylated chitosan as a coating for cardboard paper surfaces to improve the barrier and mechanical properties of the paper. Chitosan with 2% DA was reacetylated to yield chitosan with 48% DA. Both samples were applied as cardboard paper coating, and the coated materials were characterized. The paper-film system of chitosan with 2% DA had better water barrier and mechanical resistance. Heterogeneous deacetylation of chitin reduced the solubility of chitosan because molecular groups were distributed in blocks, increasing the hydrophobicity of the polymer.

Application of Chitin/Chitosan and Their Derivatives in the Papermaking Industry

Chitin/chitosan and their derivatives have become of great interest as functional materials in many fields within the papermaking industry. They have been employed in papermaking wet-end, paper surface coating, papermaking wastewater treatment, and other sections of the papermaking industry due to their structure and chemical properties. The purpose of this paper is to briefly discuss the application of chitin/chitosan and their derivatives in the papermaking industry. The development of their application in the papermaking area will be reviewed and summarized.

A pH-Sensing Film from Tamarind Seed Polysaccharide with Litmus Lichen Extract as an Indicator

A new pH-sensing film was developed by using tamarind seed polysaccharide (TSP) and natural dye extracted from litmus lichen (LLE). The addition of LLE from 0 to 2.5% decreased the tensile strength and elongation at break from 30.20 to 29.97 MPa and 69.73% to 60.13%, respectively, but increased the water vapor permeability from 0.399 × 10⁻⁹ to 0.434 × 10⁻⁹ g·s⁻¹·m⁻¹·Pa⁻¹. The UV–Vis spectra of the litmus lichen extract (LLE) in the pH range of 4–10 showed that the color clearly changed from orange to blue. The characterization results showed that TSP interacted with LLE through hydrogen bonds. The color of the film varied from orange (pH 4.0) to blue-violet (pH 10.0). The full cream milk spoilage test indicated that the film is suitable for application in full cream milk spoilage detection. The developed pH-sensing film could be used as a promising diagnostic tool for the detection of food spoilage.

Effect of blueberry agro-industrial waste addition to corn starch-based films for the production of a pH-indicator film

Intelligent packaging is an emerging area of food technology that can provide better preservation and be of further convenience for consumers. It is recommended that biodegradable materials be used to develop low-impact designs for better packaging, which could benefit the environment by simply expanding their use to new areas. In this work, corn starch, glycerol and blueberry powder (with and without prior fruit bleaching) were used to produce films by casting. Blueberry powder, a co-product from juice processing, which is rich in anthocyanins, was added in the films to evaluate its potential as a colorimetric indicator, due to the ability of anthocyanin to change color when placed in an acidic or basic environment. After the films were immersed in different buffer solutions, visual color changes were observed, where the films became reddish at acidic pH and bluish at basic pH. The ΔE* values were greater than 3, suggesting a visually perceptible change to the human eye. The samples with fruit bleaching (CB) were visually darker (lower luminance values), while the samples without bleaching (SB) had a lighter color and higher brightness, represented by larger L* values. These results indicate the potential of blueberry powder as a pH indicator for intelligent food packaging or even for sensing food deterioration.

Development of smart colourimetric starch-based indicator for liberated volatiles during durian ripeness

The mechanical, physical and barrier properties of colourimetric starch-based films (CSBFs) were developed by adding natural polymers (chitosan, citric acid, carboxymethylcellulose, and kraft fibre). Novel volatile compound indicator films were prepared from starch (as a film matrix with 30% w/w sorbitol) using the casting method and adding natural polymers, and pH-dye (methyl red and bromothymol blue as indicators). CSBFs mixed with 0.1% chitosan improved the mechanical and barrier properties with a significant decrease in water vapour transmission rate, water solubility, and oxygen transmission rate, as well as improved tensile strength. Trials using liberated fruit aromas verified that CSBFs resulted in visible colour changes in the presence of mixed sulphur and ethyl alcohol aromas. Colour change in terms of the total colour difference of CSBFs was related to mixed sulphur and ethyl alcohol levels, thereby enabling CSBFs could be used to monitor real-time ripeness of durian volatiles.