Time-temperature Indicators Research Articles

Functional Polymers and Polymer–Dye Composites for Food Sensing

The sensitive, safe, and portable detection of food spoilage is becoming unprecedentedly important because it is closely related to the public health and economic development, particularly given the globalization of food supply chain. However, the existing approaches for food monitoring are still limited to meet these requirements. To address this challenge, much research has been done to develop an ideal food sensor that can indicate food quality in real-time in a sensitive and reliable way. So far, many sensors such as time-temperature indicators, smart trademarks, colorimetric tags, electronic noses, and electronic tongues, have been developed and even commercialized. In this feature article, the recent progress of food sensors based on functional polymers, including the molecular design of polymer structures, sensing mechanisms, and relevant processing techniques to fabricate a variety of food sensor devices is reviewed.

Time temperature indicator film based on alginate and red beetroot (Beta vulgaris L.) extract: in vitro characterization

Time temperature indicator film based on alginate and red beetroot (Beta vulgaris L.) extract: in vitro characterization

Enabling Medicine Reuse Using a Digital Time Temperature Humidity Sensor in an Internet of Pharmaceutical Things Concept.

Medicinal waste due to improper handling of unwanted medicines creates health and environmental risks. However, the re-dispensing of unused prescribed medicines from patients seems to be accepted by stakeholders when quality and safety requirements are met. Reusing dispensed medicines may help reduce waste, but a comprehensive validation method is not generally available. The design of a novel digital time temperature and humidity indicator based on an Internet of Pharmaceutical Things concept is proposed to facilitate the validation, and a prototype is presented using smart sensors with cloud connectivity acting as the key technology for verifying and enabling the reuse of returned medicines. Deficiency of existing technologies is evaluated based on the results of this development, and recommendations for future research are suggested.

Mechanochromic and Thermochromic Sensors Based on Graphene Infused Polymer Opals.

High quality opal‐like photonic crystals containing graphene are fabricated using evaporation‐driven self‐assembly of soft polymer colloids. A miniscule amount of pristine graphene within a colloidal crystal lattice results in the formation of colloidal crystals with a strong angle‐dependent structural color and a stop band that can be reversibly shifted across the visible spectrum. The crystals can be mechanically deformed or can reversibly change color as a function of their temperature, hence their sensitive mechanochromic and thermochromic response make them attractive candidates for a wide range of visual sensing applications. In particular, it is shown that the crystals are excellent candidates for visual strain sensors or integrated time‐temperature indicators which act over large temperature windows. Given the versatility of these crystals, this method represents a simple, inexpensive, and scalable approach to produce multifunctional graphene infused synthetic opals and opens up exciting applications for novel solution‐processable nanomaterial based photonics.

Immobilizing laccase on electrospun chitosan fiber to prepare time-temperature indicator for food quality monitoring

Laccase was immobilized on the electrospun chitosan/poly(vinyl alcohol) fiber (ceCPL) with specific area of 17.05 m2/g to reinforce the stability of enzymatic time–temperature indicator (TTI). The ceCPL exhibited a high relative activity within 4 °C–40 °C and the activation energy (Ea) of coloration with guaiacol approached 40.9 ± 2.8 kJ/mol for 80 μg/cm2 of ceCPL-immobilized laccase. In dynamic temperature response experiments of ceCPL using intermittent temperature changes between 4 °C and 25 °C, irreversible inactivation did not occur, indicating the desirable tolerance and sensitivity of ceCPL to temperature alterations. Approximately 1 or 38 days was required to reach the endpoint of coloration at 4 °C when 80 or 8 μg/cm2 of laccase were immobilized on ceCPL, respectively. The regression equation derived from kinetic model analysis was conducted and could be further utilized to design a suitable time–temperature indicator (TTI) to monitor food quality according to the color change of ceCPL coloration.

Betacyanin as Bioindicator Using Time-Temperature Integrator for Smart Packaging of Fresh Goat Milk.

Smart packaging is a packaging system with embedded sensor or indicator technology, which provides information on the quality of the product, especially perishable foods such as goat milk. One application of smart packaging is to use a time-temperature bioindicator. The purpose of this study was to determine the quality of fresh goat milk during storage at freezing temperatures (−20 ± 2°C) for 31 days and room temperature (25 ± 3°C) for 24 hours using a time-temperature indicator by utilizing a natural dye betacyanin. The method used was descriptive analysis, and the data obtained were processed using the correlation regression test. The samples were observed at freezing temperature every 24 hours and room temperature at 0, 1, 2, 3, 4, 5, 6, 8, 10, and 24 hours. The observation criteria consisted of changes in bioindicator color, milk pH, and total microbes. The results showed that color changes of the bioindicator film at room temperature were more noticeable than at freezing temperature. Based on changes in color of the bioindicator at room temperature, the sample was safe for consumption until the 5th hour with pH 6.51, and the biofilm color characteristics were L∗ = 82.49, a∗ = 21.46, and b∗ = −7.33, but the total number of microbes did not fulfil Indonesian National Standard at the 24th hour, i.e., 1.36 × 106 CFU/ml. At freezing temperatures, fresh goat milk was still safe for consumption until the 31st day with pH 6.51 and total microbe of 1.89 × 105 CFU/ml, and the biofilm color characteristics were L∗ = 80.52, a∗ = 24.15, and b∗ = −7.91. The results of this study concluded that the milk expiration limit based on the betacyanin indicator was 5 hours at room temperature and 31 days at freezing temperature.

A Self-Healing Nanofiber-Based Self-Responsive Time-Temperature Indicator for Securing a Cold-Supply Chain.

Perishable foods at undesired temperatures can generate foodborne illnesses that present significant societal costs. To certify refrigeration succession in a food-supply chain, a flexible, easy-to-interpret, damage-tolerant, and sensitive time-temperature indicator (TTI) that uses a self-healing nanofiber mat is devised. This mat is opaque when refrigerated due to nanofiber-induced light scattering, but becomes irreversibly transparent at room temperature through self-healing-induced interfibrillar fusion leading to the appearance of a warning sign. The mat monitors both freezer (-20 °C) and chiller (2 °C) successions and its timer is tunable over the 0.5-22.5 h range through control of the polymer composition and film thickness. The thin mat itself serves as both a temperature sensor and display; it does not require modularization, accurately measures localized or gradient heat, and functions even after crushing, cutting, and when weight-loaded in a manner that existing TTIs cannot. It also contains no drainable chemicals and is attachable to various shapes because it operates through an intrinsic physical response.

Application of Lipase Based Enzymatic Time Temperature Indicator (TTI) as Quality Marker for Frozen Chicken Meat

Application of Lipase Based Enzymatic Time Temperature Indicator (TTI) as Quality Marker for Frozen Chicken Meat

Development of a novel Maillard reaction-based time-temperature indicator for monitoring the fluorescent AGE content in reheated foods.

Dietary advanced glycation end products (AGEs) are formed via the Maillard reaction in foods, especially in reheated foods, and can cause chronic diseases. In this study, a series of Maillard reaction-based time–temperature indicators (TTIs: TTI-1, TTI-2, and TTI-3) were developed with lysine and xylose for monitoring the dynamic formation of fluorescent AGEs in reheated foods. The discoloration kinetics of Maillard reaction-based TTIs and the dynamics of fluorescent AGE formation were explored. Formulas were derived to illustrate the relationship of the color change in the TTIs with time and temperature. The activation energies (Ea values) for generating the TTIs were 96.17, 87.98, and 83.55 kJ mol−1, respectively. TTI-1 was the optimal indicator for instant soy milk powder because it showed the lowest activation energy difference in this study. The results show that this series of Maillard reaction-based TTIs can be used to monitor the AGE contents in various reheated foods.

Implementation of Time Temperature Indicators to Improve Temperature Monitoring and Support Dynamic Shelf Life in Meat Supply Chains

Based on the well-investigated OnVu™ TTI kinetics, models were developed to adjust the label to different food products and predict the discolouration process under dynamic temperature conditions. After the successful validation under laboratory conditions, the applicability of the time temperature indicator (TTI) as shelf life indicator was tested in a national poultry chain. The TTI accurately reflected the temperature fluctuations occurring under real chain conditions. Shelf life predictions based on the discolouration of the TTIs were in accordance with the microbial shelf life of the product. The models were integrated in an online software tool to check for the compliance of the cold chain and predict the remaining shelf life of the product. The implementation of TTI and the software result in a valuable tool to support the decision-making process in the cold chain. The application of flexible shelf life enables the reduction of food waste in the meat supply chain.

Development of immobilized laccase-based time temperature indicator by electrospinning zein fiber

Abstract To increase the stability of enzymatic time–temperature indicator (TTI), laccase was immobilized on the electrospun zein fiber (ceZL) with high specific surface area (11.579 m2/g). The ceZL exhibited a high relative activity within 4 °C – 40 °C and the activation energy (Ea) of coloration approached 26.28 kJ/moL for 80 μg/cm2 of ceZL-immobilized laccase. In dynamic temperature response experiments of ceZL using intermittent temperature changes between 4 °C and 25 °C, irreversible inactivation did not occur, indicating the desirable tolerance and sensitivity of ceZL to temperature alterations. Approximately 6 or 26 days was required to reach the endpoint of coloration at 4 °C when 25 or 8 μg/cm2 of laccase was immobilized on ceZL, respectively. The regression equation derived from kinetic analysis was conducted and could be further utilized to design a suitable TTI to monitor food quality according to the color change of TTI by using ceZL.

Development and Testing of Fast Responsive Bi-Enzyme Time - Temperature Indicator

In order to directly indicate the change of the quality of temperature sensitive products, such as food and medicine, during transportation and storage, the time-temperature indicator (TTI) was researched. It has cumulative effect on the time and temperature in the transport process and also can be used to monitor the environmental temperature changes. Based on the novel glucose oxidase and horseradish peroxidase double enzyme reaction system, a new time-temperature indicator was developed. The suitable storage conditions and the composition of double enzyme asof the TTI reaction system were studied. In conclusion, the time-temperature indicator with obvious color change is applied to the packaging of cold products during the transportation and storage process.

Development of smart TTI label based on kinetics diffusion of vegetable oils blends for cold supply chain monitoring

Time-temperature control is a critical issue in cold supply chain, so it is very important to be tracked. Time-temperature indicator (TTI) label is devices that visually show the cold-chain accumulated history, from both time and temperature fluctuation effects. Diffusion model of TTI’s indicator based on vegetable oils blend (VOB) has been investigated. The VOB indicators were made from canola oil (CA), soybean oil (SB), and olive oil (OV) that have blended with palm oil (PO). Nine formulas of indicator were designed in combination with the oils blendings i.e (A) PO:CA:SB, (B) PO:SB:OV, (C) PO:CA:OV and the combination of various ratio were (1) 50:40:10 %v/v, (2) 50:25:25 %v/v, and (3) 50:10:40 %v/v, then the blendings were added 0.25 %m/v red lake (C.I. 16255). The diffusion kinetics of this TTI indicators have tested on a waterproof photopaper material and storaged at 4, 18, 29, 37, and 40°C. The result present that the activation energy (Ea) values of indicators were about 28.925 – 40.646 kJmol−1. The B3 and C indicators have an Ea value which have matched with Ea value of a commercial diffusion-based TTI. Based on Arrhenius equation, the diffusion model (x, m) for B3, C1, C2, and C3, respectively were xB30.5=2t.e−4017(1/T)-4.4053, xC10.5=2t.e−4124.3(1/T)-4.0196, xC20.5=2t.e−4245.1(1/T)-3.7130, and xC30.5 = 2t.e−4888.9(1/T)-1.6641. Overall, the diffusion length of the indicators have significantly correlation with time-temperature changing and this diffusion model established can represented the diffusion behaviour of TTI’s indicators.

Kinetic Modeling Of A Bi-Enzyme Time-Temperature Indicator (TTI) Based on Different Parameters for Monitoring Food Product Quality

Time-temperature indicator has been widely applied in the food industry. And, the theoretical study shows that if the time-temperature indicator is applied to monitor food, the activation energy of TTI temperature-dependent must be consistent with the activation energy of food quality loss. In this study, kinetics of absorbance and color changes in bi-enzyme were investigated as a function of storage temperature. Absorbance value was used to evaluate the enzyme reaction process under different temperature. Color change was evaluated in terms of the total color difference (DE). The results indicated that the time - temperature dependence of Absorbance and DE values followed a zero-order model. The Arrhenius equation adequately described the temperature dependence of the reaction rate constants for both absorbance and color parameters, respectively, from which the activation energies and rate constant at different temperature were obtained. There were significant linear correlations between absorbance, color and time parameter.

New perspectives in active and intelligent food packaging

Packaging is an intermediary product between producers and consumers. The most important role of packaging is to ensure the highest quality and safety of packaged products and to extend their shelf life. Given that microbiological contamination is a problem for manufacturers and consumers due to the fact that it reduces the quality of packaged products and poses a health risk, this work describes solutions related to antimicrobial packaging. More attention is given to antioxidant packaging that releases synthetic or natural antioxidants to prevent food oxidation. The purpose of intelligent packaging is to monitor the quality of food products, as well as inform consumers and food producers of their quality. Therefore, many studies focus on developing time temperature indicators. The work also discusses radio frequency identification (RFID), whose application has a lot of advantages, such as identifiability, management of stored products, labor cost savings and ensuring the quality and safety of packaged products. PRACTICAL APPLICATIONS: The current trends related to food safety and the growing expectations of the consumers lead to changes in the approach to food packing. Active and intelligent packaging has been present on the global packaging market for years, and scientists all over the world are looking for novelties related to this kind of packaging. For these reasons, this work focuses on presenting new solutions in active and intelligent packaging.

Active intelligent packaging film based on ethylene vinyl acetate nanocomposite containing extracted anthocyanin, rosemary extract and ZnO/Fe-MMT nanoparticles

Abstract A new strategy to prevent food deterioration is the use of intelligent-active food packaging. Intelligent-active packaging is defined as a barrier film which prevents or delays the spoilage of food or reveals the deterioration process in food by different mechanisms. In this study, the intelligent-active property was imbedded into food packaging films made of ethylene-vinyl acetate copolymer an abundant, flexible, and non-toxic polymer blend by incorporation of different additives. Anthocyanin extracted from red cabbage was stabilized on montmorillonite and added to the film as a time-temperature indicator. Other materials such as ZnO nanoparticles, rosemary extract, and modified montmorillonite were used to achieve antimicrobial, antioxidant, and air barrier activity. The additives and prepared films were characterized by FTIR, XRD, FESEM, TGA, and mechanical analysis. The performance of the prepared films was investigated by antioxidant capacity test by DPPH, in vitro test, minimum bactericidal concentration (MBC), minimum inhibition concentration (MIC), antibacterial test and capacity of oxygen absorbance. Results showed that films which contain rosemary extract, ZnO, and modified montmorillonite exhibited remarkable antibacterial and antioxidant activity compared to pristine EVA film.

Research progress of packaging indicating materials for real-time monitoring of food quality

The rapid development of cold-chain transportation necessitates consumers to present high requirements on safety and freshness of fresh food in recent years. The quality and taste of fresh food can be monitored and controlled through the intelligent packaging technologies and new food packaging materials such as time-temperature indicators (TTIs), Radio Frequency Identification (RFID), biological composites and polymer nanocomposites. Based on different packaging materials, indicators and sensors are employed in food packaging for real-time detection of information about freshness, temperature, microbiological, and shelf life of products in the supply chain. Wide varieties of packaging materials are suitable for providing intelligent and smart properties for food packaging, such as oxygen scavenging capability, antimicrobial activity, and recording the thermal history. Due to the special properties of prepared materials, TTIs are used to point out the remaining shelf life of perishable products throughout the supply chain. Compared with others, they have the advantages of low cost, small size and convenient indication. Additionally, the TTIs can effectively solve food quality and safety problems caused by temperature fluctuation in supply chain. Since the irreversible color change of TTIs, the food safety situation would be shown intuitively. Currently, the TTIs were widely used in application of food packaging by providing safety information. However, the application is also accompanied with some deficiencies such as the accuracy of monitoring, migration of toxic substances, stability and expensive cost etc. This review will deeply discuss the preparation of various types of TTIs based on different package indicating materials with a particular emphasis on how to improve their accuracy and stability, control the migration of toxic substances and to develop new TTIs.

Time temperature indicators (TTIs) based on silver nanoparticles for monitoring of perishables products

This work presents the results of the production and characterization of silver nanoparticles (AgNPs) to applications in Time Temperature Indicators (TTIs). AgNPs were synthetized by chemical processes. The suspensions (AgNPs in water) were characterized for different temperatures (4°C and 22°C) and time (0 to 5h). The AgNPs were characterized by energy dispersive X-ray spectrometry (EDS), UV–vis spectrophotometry and dynamic light scattering (DLS). AgNPs with diameters between 40 to 160nm were produced. The UV-Vis spectra reveal a characteristic absorption peak of the Ag in 420nm. This suspension shows shifts in the emission wavelength when exposed to room temperature compared to when exposed to a temperature of 4°C for different periods of time. Δλ = 20nm in the absorption spectra were found. Size distribution showed that the nanoparticles size decreases from 164 ±8 nm to 44±3 nm in the period of time studied. Suspension with nanoparticles concentration of 1,26· 10-10 M were obtained. TTIs manufactured with nanomaterials base its operation on the variations of the characteristics of nanoparticles suspended due to absorbing heat.

Development and characterization of a new nonenzymatic colored time–temperature indicator

AbstractTime–temperature indicators (TTIs) are effective tool for monitoring food quality during processing and distribution. In this study, a new colored nonenzymatic browning (fructose and glycine)‐based TTI was developed. Twelve TTIs were made at four different substrate concentrations and three pH ranges 8.0–10.0. The mathematical models of each TTI were drawn up, which showed the relationships between the color change in terms of absorbance (420 nm), time and temperature. The activation energies (Ea), calculated from Arrhenius relationship ranged between 58.09 and 95.54 kJ mol−1 of all TTIs. Activation energies could be changed to match the Ea of food product, by modifying pH and the proportion of the fructose and glycine. A visual color change of TTI and a wide range of activation energy illustrated that this new chemical‐based TTI could be applied to show the time–temperature history of foodstuffs, and to indicate the food quality, which is associated with the undergoing of the time–temperature exposure.Practical applicationsThis work provides the development of a new smart temperature indicator based on nonenzymatic browning. The indicators are more useful for food quality monitoring from manufacturing till consumer consumption. However, the application of the TTI's can be extended to food processing, that is, sterilization, pasteurization, and drying process. Thus, the use of the TTIs can encourage food producers to scrutinize food processing and distribution to deliver good quality to consumers with guaranteed security.

Amylase based enzymatic time temperature indicator (TTI) as thermal abuse marker for frozen chicken meat

Amylase based enzymatic time temperature indicator (TTI) was prepared using starch as substrate and enzyme amylase to monitor thermal abuse history of frozen (−18±2°C) chicken meat during supply chain. TTI showed an irreversible distinct colour change from initial bluish black colour to intermediate light yellow colour to final irreversible white yellow during temperature abuse conditions at 15±1, 25±1 and 35±1°C except 5±1°C. At different temperature abuse conditions viz., 15±1°C, 25±1°C and 35±1°C, quantitative changes in various parameters of chicken meat were evaluated and correlated with distinct colour alterations of TTI. The values for FAA, TVBN and instrumental colour analysis were beyond the meat safety limit at 35±1°C but within the limit at 15±1°C and 25±1°C at final colour changes of TTI. However, pH and microbiological parameters values were within the meat safety limit at 15±1, 25±1 and 35±1°Cat final colour changes of TTI. The results showed significant correlation of meat quality parameters with colour changes in TTI at 35±1°C and non-significant correlation of meat quality parameters with colour changes in TTI at 15±1 and 25±1°C. So, changes in quality characteristics of frozen chicken meat are not adequately indicated by TTI after exposure to different temperature abuse conditions. Therefore, amylase based enzymatic TTI has lesser applicability for utilization of quality marking of frozen chicken meat at different temperature abuse conditions.