The quality of food, pharmaceuticals, and other sensitive products constantly changes based on temperature and time. Yet, in practice, it has long been difficult to accurately visualize or assess the quality at a glance. Time-Temperature Sensing Ink, developed by Hitachi Industrial Equipment Systems, is emerging as an entirely new solution that originated from applying ink development technologies cultivated through years of R&D in industrial printers.
Building on the unique feature of this ink—its irreversible color change in response to temperature history—this solution offers far more than a conventional quality visualization tool. It has the potential to deliver entirely new experiences to consumers, while also supporting the global expansion and branding of Japanese food products, whose popularity continues to grow rapidly overseas. For this feature, we spoke with Kohei Aida, who has led the planning and development of the Time-Temperature Sensing Ink within the Marking System Design Department of Hitachi Industrial Equipment Systems, and Koji Okada, who has been driving both development and proof-of-concept trials in collaboration with external partners and industry stakeholders.
Development Driven by a Clear Concept
Kohei Aida is leading the comprehensive development of this groundbreaking Time-Temperature Sensing Ink. Before his current position, Aida worked at a Hitachi, Ltd. research laboratory, where he began exploring this ink technology. Since then, he carried a strong desire to turn the concept into a commercial product and viable business. Today, he oversees business strategy and development management, playing a central role in driving the project forward and accelerating its path to market.
“Within our Marking System Design Department, our core products are industrial inkjet printers used to print information such as expiration dates on food items. The idea began with the simple question: Can we leverage this printing technology to create new forms of value?” Aida recalls.
In 2015, a customer approached the team with an idea: “If you could print an ink that changes color with temperature fluctuations using an inkjet printer, couldn't it be used for temperature management in pharmaceuticals?” This suggestion sparked the development of the Time-Temperature Sensing Ink.
“However, as we continued our research, our team made an important discovery: the quality of foods or pharmaceuticals does not depend simply on temperature, but rather on the combined effect of temperature and time. Existing thermochromic inks typically change color instantly when a certain temperature is reached, making them unsuitable for capturing the gradual quality changes that occur over extended periods. This prompted us, in 2016, to establish a new concept: an ink that slowly changes color in response to cumulative temperature exposure—the combined effect of temperature and time.”
Cumulative temperature is an index that represents the combined effect of both temperature and time. In an integrated manner, it indicates the total thermal exposure that a food product or pharmaceutical has experienced over a given period. The condition of foods—such as ripening or degradation—and the stability of pharmaceuticals are rarely determined by a single moment when a temperature threshold is exceeded. In most cases, they are influenced by the entire temperature history the product has undergone (Higher temperatures cause faster changes, and lower temperatures eventually lead to the same outcome if it's exposed long enough). For this reason, cumulative temperature serves as a critical indicator for assessing product quality.
Smart, Simple, and Cost-Efficient
So how did the team advance the development of this concept—an ink that slowly changes color based on cumulative temperature? Aida continues:
“We moved forward with the approach of combining existing technologies to accelerate development. For example, one of the hints came from thermal paper, such as the kind used for receipts. Thermal paper instantly produces color when heat triggers a chemical reaction. By intentionally slowing that reaction and incorporating special materials that gradually change color over several days, we were able to achieve the desired behavior. Because our concept was clear from the beginning, the core framework of the technology was already established by 2017—about one year after the project began.”
The ink slowly colors at low temperatures and faster as temperatures rise, making the entire temperature history visible at a glance. The color change is irreversible; once it shifts, it does not revert. The system provides strong reliability. But what about manageability and cost? Koji Okada, who oversees proof-of-concept trials and ink development to meet emerging needs, answers this question.
“Traditional temperature monitoring typically uses electronic temperature loggers. These devices are expensive, require a power source, and demand additional labor and cost for collection and disposal after use. In contrast, our ink captures temperature history through its color change and can be discarded as is after use. This makes it overwhelmingly more cost-effective. For example, you can apply the ink label to each individual item, such as a melon, and visualize quality at the unit level.”
The Time-Temperature Sensing Ink is cost-effective and maintenance-free, allowing for flexible application on everything from cargo-level monitoring to individual product-level use. Moreover, its value is amplified when offered as part of a complete solution: the ink itself, combined with a compact printer capable of producing the necessary labels. This integrated offering represents a major business advantage.
Time-Temperature Sensing Ink: “Visualizing Quality” and Transforming the Supply Chain
By irreversibly changing color based on cumulative temperature—the combined effect of temperature and time—the Time-Temperature Sensing Ink makes invisible temperature histories instantly recognizable. Although the project began with a clear concept and progressed smoothly on the technical side, the overall journey was far from straightforward.
“The major challenges emerged not in the technology development itself, but during the commercialization process,” recalls Kohei Aida, Senior Engineer in the Marking System Design Department at Hitachi Industrial Equipment Systems.
“We initially aimed to apply the ink to pharmaceuticals and began discussions with a pharmaceutical manufacturer in 2018. However, the COVID-19 pandemic hit soon after. Not only did communication become difficult, but pharmaceutical companies had to prioritize vaccine production and supply. While they recognized the potential of the ink and said ‘This would be useful to have,’ they simply no longer had the capacity to introduce additional value-added technologies at that time. In the midst of this situation, someone advised us: ‘Why not start by promoting the technology in the food industry, where adoption is easier? If it becomes standard there, we in the pharmaceutical industry will also be more inclined to adopt it.’ That advice became a major turning point, and around 2021, we significantly shifted our focus toward applications in the food sector.”
Delivering a New Food Experience
This shift broadened the target audience of the Time-Temperature Sensing Ink from the highly specialized pharmaceutical sector to the much wider world of food products and general consumers. Naturally, different audiences bring different needs. To clearly communicate the added value of the technology, Aida’s team developed a dedicated smartphone application.
“You can roughly assess the product’s quality by checking the ink color on the label, but the app allows you to obtain more quantitative information,” explains Koji Okada, who leads proof-of-concept testing for the Time-Temperature Sensing Ink. The labels affixed to the melons prepared in the development lab in Hitachi city, Ibaraki, feature a QR code placed next to the ink for visual checking.
“By scanning the QR code, you can identify which melon it is and which type of ink is being used. The app then analyzes the ink’s color concentration to calculate the current cumulative temperature and display predictions of the quality condition and of days until the optimum ripeness.”
“For example, if you scan the label of a melon stored at 5°C for five days, the app will display the average storage temperature and cumulative temperature, along with a prediction such as ‘If kept at 10°C, it will reach optimum ripeness in seven days.’ In contrast, a melon stored at 25°C for five days will show a much higher cumulative temperature, and the app will indicate ‘It is already at optimum ripeness.’ We hope this capability will visualize quality in a way that gives consumers an entirely new eating experience.”
Ripeness—which has traditionally been judged uniformly regardless of personal preference—can now be selected according to individual taste. For instance, a consumer who prefers firmer fruit could choose to eat it when the cumulative temperature reaches 80, while another who likes it softer would wait until it reaches 120. Consumers can choose products based on their exact preferences. During the app’s development, a group of about 30 researchers conducted repeated sensory evaluations to accumulate data correlating cumulative temperature with taste—forming the foundation of the app’s predictive capabilities.
Contributing to the Enhancement of the “Japan Brand”
Nearly a decade has passed since the early days of development, and the path toward Time-Temperature Sensing Ink’s commercialization is finally coming into view. So what lies ahead for this technology? According to Okada, who leads its practical implementation, one promising application is supporting the export of namazake, a type of unpasteurized sake highly prized among gourmets worldwide.
“One of our key focus areas is the export of Japanese sake,” Okada explains. “Namazake is extremely sensitive to heat, and its flavor profile easily changes, which has made long-distance distribution a challenge. By applying our label, we can visualize the ‘flavor impact’ of temperature exposure during transportation and local storage, ensuring that the product can be delivered in its best condition. We are currently conducting demonstration trials with a brewery in Akita Prefecture as part of a Ministry of Agriculture, Forestry, and Fisheries subsidy project, exporting to markets such as Singapore and Australia.”
Despite the growing global popularity of Japanese cuisine, the reality is that products are not always managed under ideal temperature conditions once they leave Japan. The team hopes that by using the Time-Temperature Sensing Ink to preserve product quality and uphold the value of the “Japan Brand,” they can help further expand the international reach of Japanese food products.
Creating New Value to Drive Supply Chain Evolution
Looking ahead to April 2026, Aida explains that the team plans to begin full-scale deployment of a comprehensive solution that integrates the Time-Temperature Sensing Ink with labels, label printers, and cloud services. But their ambitions reach far beyond simple quality control; they envision a model that enables far greater value creation.
“By collecting and analyzing data on when, where, and in what condition products are ultimately consumed, producers can apply these insights to areas such as varietal improvement and optimization of production and inventory planning. We believe this will also create value in business operations—for example, in selecting the most efficient distribution routes.”
“Achieving this vision requires more than the team’s efforts alone. By leveraging Hitachi’s strengths in digital technologies, we are advancing an integrated approach that combines IT, OT, and products—enhanced by the collective knowledge and experience built across the Hitachi Group and further accelerated by AI. This vision embodies the aspirations of Lumada 3.0* as outlined in Hitachi’s new management plan, Inspire2027—a commitment to creating new value for society. By integrating this technology with the systems of various companies, it becomes possible to drive digital transformation across entire supply chains.
Aida concluded the interview with a clear and resolute message: he aims to position the Time-Temperature Sensing Ink as a key enabler for realizing this overarching vision and to leverage it as a means of delivering meaningful value to society at large.
Kohei Aida
Senior Engineer
Infrastructure Systems Group, Marking Systems and Hoist Systems Division,
Marking System Design Dept.
Hitachi Industrial Equipment Systems Co.,Ltd.
Koji Okada
Infrastructure Systems Group, Marking Systems and Hoist Systems Division,
Marking System Design Dept.
Hitachi Industrial Equipment Systems Co.,Ltd.
