Time-temperature Indicators Research Articles

Autonomous Off-Equilibrium Morphing Pathways of a Supramolecular Shape-Memory Polymer.

The diverse morphing behaviors of living creatures arise from their unlimited pathways. In contrast, the equilibrium-driven morphing pathways of common synthetic shape-shifting materials are very limited. For a shape-memory polymer (SMP), its recovery from the temporary shape(s) to the permanent shape typically requires external stimulation and follows a single fixed route. Herein, a covalently crosslinked SMP is designed with ample ureidopyrimidinone (UPy) supramolecular moieties in the network. The UPy units endow the SMP with strong time-temperature dependency, which is explored as a mechanism for spatio-temporal programming of autonomous shape-shifting pathways. In particular, the use of digitally controlled photothermal heating provides versatility in control via an off-equilibrium mechanism. In addition, cooling/heating across its glass transition introduces a locking/unlocking mechanism for its temporal morphing. The benefits of these unique features are demonstrated by multi-shape-transformation, an "invisible"-color-based clock, a time-temperature indicator, and sequence-programmable 4D printing.

Anthocyanins from Agro-waste as Time-Temperature Indicator to Monitor Freshness of Fish Products

Fish products perish easily due to microbial contamination. Uncontrolled thawing will increase the rate of microbial activity at every 10°C increase in temperature. One of indicator that can detect food quality is the time-temperature indicator (TTI) with changes in pH. However, these indicators are generally made of synthetic chemicals which tend to pollute the environment. This study aimed to summarize various studies on anthocyanins from agro-waste as time-temperature indicator to monitor freshness of fish products. This research used systematic literature review (SLR) from various relevant research and resources. The SLR process includes practical screening, quality appraisal, synthesizing, and reviewing. Anthocyanins derived from agro-waste than can be developed into TTI are purple yam peel, black plums peel, blueberries peel, rambutan peel, sweet potato peel, dragon fruit peel. The TTI from agro-waste anthocyanins can be developed to monitor freshness of fish products.

Enzymatic Time-Temperature Indicator Prototype Developed by Immobilizing Laccase on Electrospun Fibers to Predict Lactic Acid Bacterial Growth in Milk during Storage.

Laccase was immobilized on a chitosan/polyvinyl alcohol/tetraethylorthosilicate electrospun film (ceCPTL) and colored with guaiacol to obtain a laccase time–temperature indicator (TTI) prototype. The activation energy (Ea) of coloration of the prototype was 50.89–33.62 kJ/mol when 8–25 μg/cm2 laccase was immobilized on ceCPTL, and that of lactic acid bacteria (LAB) growth in milk was 73.32 kJ/mol. The Ea of coloration of the TTI prototype onto which 8–10 μg/cm2 laccase was immobilized was in the required range for predicting LAB growth in milk. The coloration endpoint of the TTI prototype onto which 10 μg/cm2 (0.01 U) laccase was immobilized could respond to the LAB count reaching 106 colony-forming units (CFU)/mL in milk during a static temperature response test, and the prediction error was discovered to be low. In dynamic temperature response experiments with intermittent temperature changes between 4 and 25 °C, the coloration rate of the laccase TTI prototype was consistent with LAB growth. The results of this study indicate that the laccase TTI prototype can be applied as a visual monitoring indicator to assist in evaluating milk quality in cold chains.

Recent Developments in Seafood Packaging Technologies.

Seafood products are highly perishable, owing to their high water activity, close to neutral pH, and high content of unsaturated lipids and non-protein nitrogenous compounds. Thus, such products require immediate processing and/or packaging to retain their safety and quality. At the same time, consumers prefer fresh, minimally processed seafood products that maintain their initial quality properties. The present article aims to review the literature over the past decade on: (i) innovative, individual packaging technologies applied to extend the shelf life of fish and fishery products, (ii) the most common combinations of the above technologies applied as multiple hurdles to maximize the shelf life of seafood products, and (iii) the respective food packaging legislation. Packaging technologies covered include: Modified atmosphere packaging; vacuum packaging; vacuum skin packaging; active food packaging, including oxygen scavengers; carbon dioxide emitters; moisture regulators; antioxidant and antimicrobial packaging; intelligent packaging, including freshness indicators; time–temperature indicators and leakage indicators; retort pouch processing and edible films; coatings/biodegradable packaging, used individually or in combination for maximum preservation potential.

Gold–silver core-shell nanorods based time-temperature indicator for quality monitoring of pasteurized milk in the cold chain

A time-temperature indicator (TTI) based on gold-silver core-shell nanorods ([email protected] NRs) was developed to monitor the quality degradation of pasteurized milk in the cold chain. Changes of longitudinal plasmon peak wavelength, micro-morphology and colour of the [email protected] NRs TTI at 4 °C, 15 °C, 25 °C, and 35 °C were investigated, and kinetic characteristics and temperature dependence of the TTI were studied. Pasteurized milk was also stored at the same temperatures, and changes of titratable acidity (TA), pH values and total bacterial count (TBC) were determined and fitted to characterize the kinetic properties of each quality attributes at different storage temperatures. Besides, the Arrhenius equation was used to calculate the activation energy (Ea) values, among which the [email protected] NRs TTI, TA, pH and TBC showed Ea values of 70.36, 65.67, 127.87 and 52.33 kJ/mol, respectively. Results showed that the TTI and TA possessed more similar Ea values, suggesting that the TTI could predict the TA of pasteurized milk in the cold chain more accurately. Furthermore, a dynamic temperature test was performed to verify the applicability and reliability of the TTI. Temperature accumulation effects were calculated and effective temperatures (Teff) of the TTI and the pasteurized milk were determined as 287.4 K and 287.3 K, respectively, which indicated high sensitivity and good applicability of the TTI for quality monitoring of the real milk system, showing great application potentials for cold chain intelligent labels.

Effect of heating by solid-state microwave technology at fixed frequencies or by frequency sweep loops on heating profiles in model food samples

One of the parameters that has the most influence in the uniformity of microwave heat processing is frequency. Unlike the traditional magnetron microwave system, it is possible to control and set up the frequency with the newly developed solid-state microwave system. The aim of this study was an investigation of the effect of fixed frequencies and frequency sweep loops (in the range of 2400–2500 MHz) on the uniformity of heat processing in circular gellan gel model samples containing Maillard reactive agents in a solid-state microwave system. Therefore, the purpose was to compare the solid-state system at fixed frequencies in which the megaton generator also works. While the magneton generator runs at random frequencies within a certain range, solid-state systems are capable of conducting heat processing at fixed frequencies. This novel characteristic will be evaluated through the implementation of different trials at various fixed frequencies. Additionally, the effect of changing frequencies is evaluated through frequency sweep loops, where the frequency of the solid-state system is changed in a pre-determined pattern. The results obtained from the time-temperature indicator of the Maillard reaction and the temperature indicator of infrared thermography showed that the heat processing of samples with the frequency sweep loops, even without turntable rotation, can be more uniform in comparison to those with fixed frequencies and turntable rotation. Moreover, the frequency sweep loops not only improved the uniformity of temperature distribution of the heated sample, but also increased the average temperature of processed samples and, thus, microwave heating absorption.

Tamper-Proof Time-Temperature Indicator for Inspecting Ultracold Supply Chain.

In the precarious situation caused by the COVID-19 pandemic, the use of messenger ribonucleic acid (mRNA) vaccines is promising for prevention against the infection. However, this type of vaccine has not been effectively commercialized because it needs to be stored and transported at ultracold conditions. mRNA vaccines exposed to undesired temperatures may not show any visible changes but can deteriorate and cause negative effects. Consumers’ demand for vaccine authenticity requires logistics to develop a robust monitoring tool to ensure the integrity of ultracold supply chain from manufacturing until vaccination. Here, we report a time–temperature indicator (TTI) that can detect a relatively small change in temperature within subzero ranges, for example, from −70 to −60 °C, which cannot be achieved by current TTIs operating at room temperature. A dyed noneutectic ethylene glycol/water mixture that melts near the mRNA conservation temperature (−69 °C) diffuses into a white absorbent and leaves a colored trace. In addition, the heterogeneous ice particles in the noneutectic mobile phase can prevent absorption during short-term exposure to room temperature. Therefore, the proposed TTI will not record inevitable “meaningless” short-term exposure to room temperature during the cold supply chain but monitor the “meaningful” relatively long-term exposure above −60 °C. These findings help facilitate the safe distribution of the COVID-19 mRNA vaccines.

Progresses in Food Packaging, Food Quality, and Safety-Controlled-Release Antioxidant and/or Antimicrobial Packaging.

Food packaging is designed to protect foods, to provide required information about the food, and to make food handling convenient for distribution to consumers. Packaging has a crucial role in the process of food quality, safety, and shelf-life extension. Possible interactions between food and packaging are important in what is concerning food quality and safety. This review tries to offer a picture of the most important types of active packaging emphasizing the controlled/target release antimicrobial and/or antioxidant packaging including system design, different methods of polymer matrix modification, and processing. The testing methods for the appreciation of the performance of active food packaging, as well as mechanisms and kinetics implied in active compounds release, are summarized. During the last years, many fast advancements in packaging technology appeared, including intelligent or smart packaging (IOSP), (i.e., time–temperature indicators (TTIs), gas indicators, radiofrequency identification (RFID), and others). Legislation is also discussed.

Concentration Gradients in Material Sciences: Methods to Design and Biomedical Applications

AbstractConcentration gradients are at the basis of many natural phenomena and hold great importance in human and plant biology. This basic phenomenon has inspired many material scientists to confer novel and original properties to materials with numerous biomedical and pharmaceutical applications such as drug discovery, controlled release of drugs, tissue engineering, orthopedic implants and time–temperature indicators, amongst others. While the generation of gradients in solution is well described, their incorporation in solid materials remains challenging. This study reviews concepts and methods reported to generate gradients in respective solutions and (at the surface or in) solid materials like polymer scaffolds and matrices. This article also discusses how innovative materials possessing such gradients may be applied in biomedicine and pharmacy.

Analysis of color variation and development of a reaction tool for the development of timetemperature indicator based on Maillard reaction

Analysis of color variation and development of a reaction tool for the development of timetemperature indicator based on Maillard reaction

Applications of enzymatic time–temperature indicator (TTI) devices in quality monitoring and shelf-life estimation of food products during storage

The temperature abuse encountered by food products during storage due to deviations from the recommended storage conditions often leads to a considerable loss, especially for frozen and refrigerated foods. From a consumer perspective, the real history of time–temperature data is of interest so that the customer can get an idea about the remaining shelf-life. The time–temperature indicator or integrator (TTI), a small and inexpensive device, is attached to the packaging material and provides the time–temperature history of a food product during storage, thus estimating remaining shelf-life in a non-destructive manner. The enzymatic TTI is based on a thermo-sensitive reaction between enzyme and substrate. A suitable dye is mixed into this medium as an indicator, which changes its color depending on the variation in the pH of the reaction medium. In the recent past, several TTIs have been developed based on different enzymes, including lipase, amylase, phospholipase, urease, laccase, and others. The corresponding applied food matrices were fruits, vegetables, milk products, seafood, poultry, and meat products. Developing a new enzymatic TTI requires a systematic approach to correlate the response-TTI dependency. Such development needs a thorough understanding of the kinetics of food quality attributes and the activation energy. This review provides an overview of enzymatic TTI, theoretical considerations, and the systematic approach required to develop any enzymatic TTI. The integration of such information will simplify the design of novel enzymatic TTIs for a wide array of food products during frozen storage.

Prediction of fruit quality based on the RGB values of time-temperature indicator.

Time-temperature indicators (TTIs) are cost-efficient tools that may be used to predict food quality. In this paper, a diffusion TTI was used to predict fruit quality during storage. Both the color changing characters of TTI and the quality parameters, including weight loss, soluble solids content, vitamin C content, titratable acidity, and antioxidant capacity of three kinds of fruits (kiwifruit, strawberry, and mango), were investigated for storage temperatures (5, 10, 15, and 20°C). The relationships between the color changing properties and fruit quality parameters have been built based on the activation energy (Ea ). The results showed that the storage temperature and time had significant effects on the color changing of TTI and fruit quality. The RGB value of TTI decreased with time, and the higher the storage temperature, the faster the RGB value reduced. Also, the higher the storage temperature, the faster the fruit quality changed and the poorer they were. Furthermore, all of the differences of Ea between TTI color response and fruit quality change are less than 25kJ/mol, which indicates that the TTI can be used to predict these fruit quality. Finally, prediction models were built and validated based on the RGB values of TTI. It provides the possibility for low-cost quality monitoring and has more application potential in food quality predicting. PRACTICAL APPLICATION: By monitoring the color change of diffuse time-temperature indicator (TTI) and the quality change of fruit, the feasibility of TTI for fruit quality monitoring was determined and the quality prediction model was established. The diffusion TTI and fruit quality prediction model can realize the monitoring and predicting of fruit quality based on the TTI, which provides a basis for the combination of TTI Quick Response Code and fruit quality monitoring, with a view to achieving fruit quality status by scanning the Quick Response Code of TTI with mobile phones in the future. This method may provide a new solution to monitor the fruit quality during storage and distribution based on visualization technology that can simplify the methods of detecting fruit quality and achieve fast quality detection. It provides the possibility for low-cost quality monitoring and has more application potential in food quality predicting. Further studies on diffusion TTI are needed to develop its application in more field of food and make the diffusion TTI an intelligent mean for food quality monitoring and predicting.

Fabrication of a time-temperature indicator by inkjet printing of a spore-based bio-ink

Bio-indicators are nowadays being increasingly used by the food and drug industry to detect the changes in environmental conditions. In this study, a time-temperature indicator (TTI) is fabricated by using an office thermal inkjet printer to print a new custom-made bio-ink for detecting changes in color that occur with time and temperature variation. In lieu of the regular inks, the TTI uses solutions containing Geobacillus stearothermophilus (G. stearothermophilus) and Bacillus atrophaeus (B. atrophaeus) spores, tryptic soy broth, pH indicators, and a combination of polyvinyl alcohol and borax as the gelling agent, to be dispensed from the printer cartridge. Following the printing process, the samples thus obtained are coated with a protective film to avoid moisture loss. The effects of bio-ink gelatinization, pH, color intensity, and print resolution on bacterial printing are determined by varying the level of each parameter. The presence of the protective film on printed bacteria is found not only to lead to the growth and proliferation of bacteria but also to reveal color with sharper contrast. The indicator’s initial and final colors are modified by varying the pH levels of the solutions. Increasing color intensity (20%, 40%, 60%, 80%, and 100%) in the software settings is used to induce significant enhancements in the printed bacterial populations, thereby controlling the rate of color change. It is, moreover, observed that changes in print resolution do not have any significant effects on the populations of printed bacterial spores. In general, the TTI’s endpoint may be modified so as to suit various pharmaceutical and food applications.

Hydrosols of Titanium Dioxide Nanoparticles Containing Ti(IV) Peroxo Complexes: Modification, Optical Properties, Morphology, and Bleaching Kinetics

—This paper reports the development and characterization of new inexpensive and safe light–time–temperature indicators for products of the pharmaceutical and food industries. For this purpose, we have prepared and characterized stable sols of titanium dioxide nanoparticles modified with titanium(IV) peroxo complexes. Electronic absorption spectroscopy, dynamic light scattering, scanning probe microscopy, and experimental kinetic data demonstrate that, varying synthesis conditions and, hence, the stability of the Ti(IV) peroxo complexes, one can ensure that their bleaching is symbatic with the degradation of a particular labeled object after the expiry date, and/or in the case of the required temperature conditions being not fulfilled, and/or during storage in the light. The most important result of this study is that we have found correlations between modification conditions of titanium peroxide sols, their optical properties, the morphology of films produced from them, and their bleaching kinetics under illumination.

Smart monitoring of gas/temperature changes within food packaging based on natural colorants.

The development of smart packaging and innovation in common food packaging technology will greatly help to meet market needs, including consumer preference for "safe" foods, high-quality products and mitigate the negative environmental impacts of food packaging. In addition, consumers' tendency to use natural ingredients such as pigments and biopolymers has provided the basis for their application in the food industry, including smart food packaging. Hence, smart packaging in addition to protecting food products against environmental damage can also reveal a sign (colorimetric, chemical, electric, etc.) in real time in response to any changes in the packaging conditions and food quality. This comprehensive review emphasizes on the gas/temperature-sensitive smart films based on natural colorants and their key applications in the food packaging systems. Technological considerations associated with the natural colorant-responsive films, smart packaging, biopolymers, and importance of natural colorants versus synthetic dyes are investigated. In practice, the most common designed colorimetric indicators for monitoring gas and temperature changes and application of relevant smart films in real food models have also been discussed. Gas and time-temperature indicators provide a rapid, reliable, and online assessment and a visual indication of the food product quality level, usually through a color change, which is directly related to gas and temperature conditions during distribution and storage of relevant food products. However, future studies need to consider main points such as cost, consumers' acceptance, and confidence, regulatory aspects (i.e., labeling) and multifunctionality of smart packaging to be commercially sustainable.

Novel Color Change Film as a Time-Temperature Indicator Using Polydiacetylene/Silver Nanoparticles Embedded in Carboxymethyl Cellulose.

Time–temperature indicators (TTIs) can be important tools in product applications to monitor food quality losses, especially for fruits and vegetables. In this context, the effects of silver nanoparticles (AgNPs) and glycerol on the color change of polydiacetylene/AgNPs (PDA/AgNPs) embedded in carboxymethyl cellulose (CMC) film as time–temperature indicators (TTIs) were investigated. A CMC film prepared with 30 mg/L AgNPs and a 1:3 (v/v) PDA:AgNP ratio exhibited a faster color change than under other conditions. At 35 °C, the films with PDA/AgNPs changed color from purplish-blue to purple and purple to reddish-purple over time due to the higher thermal conductivity of AgNPs and larger PDA surface area exposed to specific temperatures. The total color difference (TCD) of PDA/AgNP-embedded CMC film directly changed with regard to time and temperature. However, adding glycerol to the system resulted in a symmetrical chemical structure, a factor that delayed the color change. Scanning electron micrographs showed AgNPs embedded in the CMC films. Transmission electron micrographs indicated a core-shell structure of PDA/AgNP vesicles in the CMC matrix. PDA/AgNP vesicles were confirmed by second derivative Fourier transform infrared spectroscopy, with a new peak at 1390–1150 cm−1. The kinetics of TTIs from PDA/AgNP-embedded CMC films yielded an activation energy of 58.70 kJ/mol.

Vaccine time–temperature indicators for present and future viral threats

Vaccine time–temperature indicators for present and future viral threats

A novel UHPLC method for determining the degree of coffee roasting by analysis of furans

The aim of this study was to develop a multi-analyte UHPLC method for furans and to apply it to commercial coffee samples as well as commercial roasting trials. Furans, as rising time–temperature indicators (TTIs), promised to be an alternative to unsatisfactory roasting temperature measurements. Consequently, a UHPLC–UV method for the determination of 5-hydroxymethyl-2-furfural (HMF), 5-hydroxymethyl-2-furoic acid (HMFA), 2-furfural (F), 5-methylfurfural (MF), 2-furyl methyl ketone (FMC), 2-furoic acid (FA), and for 3-caffeoylquinic acid (3-CQA) was developed and validated. Commercial roasted coffee beans contained 77.7–322 mg/kg HMF, 73.3–158 mg/kg HMFA, 109–200 mg/kg 2-F, 157–209 mg/kg MF, 12.3–32.8 mg/kg FMC, and 137–205 mg/kg FA. Roasting trial samples showed strong rising HMF contents (max.: Arabica: 769 mg/kg, Robusta: 364 mg/kg) followed by a distinct decline. Only MF and FA appeared as steady rising TTIs in the roasting process in Arabica and Robusta beans. 3-CQA fitted well as a decreasing TTI as expected.

Household storage of pharmaceutical products in Saudi Arabia; A call for utilising smart packaging solutions

BackgroundLimited information is known about the storage conditions of medicinal products post-dispensing in Saudi Arabia (SA). The particularly hot and humid climate in the region may lead to the loss of essential performance specifications. ObjectiveTo investigate the conditions in which medications are held after being dispensed, and up until administration by households in SA. In addition, storage practices adopted by households in the region, as well as their knowledge and awareness are explored. This study also discusses the opportunity of utilising Time-Temperature Indicators (TTIs) in the pharmaceutical industry in SA as a quality-assurance enhancement solution. MethodsA cross-sectional questionnaire targeted at households in SA was designed to explore storage practices, background knowledge and awareness of factors that can influence drug stability. Additionally, temperature and relative humidity mapping of 35 different rooms in various homes and cities in SA, as well as car interiors, was performed. ResultsMore than 1000 households have participated in this study from all regions of SA. Approximately, 95% have claimed to take part in storing medications at home. First-aid and supplemental purposes were two of the reasons 80.9% have claimed, while 43.2% claimed treatment for chronic conditions. Just over 35% claimed that not knowing how to dispose of medications, is the reason behind their storage. More than 35% of participants could not identify most suitable storage conditions, and >10% were unaware of the effect storage conditions may have on shelf-life. Many were found to store medication in inappropriate areas, liquid dosage forms for example were stored in freezers by more than 3%. Upon monitoring temperatures of all room types, 25ºC was exceeded throughout a 24-hour duration in bathrooms, kitchens and limited use rooms. Temperatures in parked car interiors exceeded 70ºC. ConclusionsA significant percentage of households in SA lacked knowledge and awareness of good storage practices. However, due to high temperatures observed in the region, increasing knowledge and awareness is not enough, as medicinal cabinets with basic temperature control (e.g. designated secure fridge) are needed. Additionally, the use of TTIs to provide consumers with accumulated thermal history may enhance quality-assurance of thermally sensitive products.

State/Phase Transitions, Ice Recrystallization, and Quality Changes in Frozen Foods Subjected to Temperature Fluctuations

Market demand for affordable frozen foods has grown due to changes in consumer lifestyle. The quality of frozen food must be maintained throughout production, storage, transport, and distribution. Recent developments in the science and technology of food freezing have led to improvements in the quality of frozen foods. Examples include the control of ice nucleation (by anti-freeze proteins and ice nucleation agents) and advances in freezing technologies (such as electric and magnetic freezing). Progress in the technology of frozen food distribution systems (such as use of time-temperature indicators) has enabled the delivery of high-quality, high-value, and safe frozen foods to consumers. However, unavoidable temperature fluctuations occur during the handling of frozen food. State and phase transitions in frozen food lead to ice recrystallization and quality changes, requiring optimized management strategies such as packaging-based and location-based approaches. Therefore, an understanding of ice recrystallization in frozen food, especially the physical and chemical properties of food matrices, is important. In this review, we evaluate the impact of temperature fluctuation and ice recrystallization on the quality of frozen food, based on characteristic thermal transitions.