Smart ink made from butterfly pea flower extract can change color when exposed to harmful substances or toxic liquids. Using smart ink helps detect early signs of food spoilage during storage and transportation, allowing consumers to receive early warnings and avoid consuming unsafe food.
Since 2021, a group of students including Le Cao Tri and Pham Ngoc Lan Vi from Saigon University of Technology began researching methods to test spoiled food in packaging as a substitute for litmus paper.
Through their study of scientific articles, Tri discovered that butterfly pea flower (Clitoria ternatea) can be extracted to produce a solution with higher pH sensitivity compared to many other plants such as purple cabbage and roses. The extract from butterfly pea flower can change color due to structural changes in a biological pigment called anthocyanin. This pigment alters when there are pH changes in food. “This is an indication that food is beginning to spoil,” Tri explained about the mechanism of anthocyanin. Based on this, the group developed a process to create ink from butterfly pea flowers.
The group tested the spoilage process of red tilapia using ink printed with images of three fish on the label, observing a color change from red to purple. (Video: NVCC)
The butterfly pea flowers were collected and then extracted using 70-degree alcohol to obtain the anthocyanin compound. The anthocyanin solution was then concentrated and evaporated with alcohol solvent at low temperatures in a vacuum environment. The concentrated extract was mixed with other raw materials to create a smart indicator ink. The ink was calibrated and fixed to a specific pH level.
According to Tri, the most crucial step is evaporating the alcohol solvent to concentrate the extract and increase the anthocyanin concentration, which helps determine the necessary amount for the ink to function effectively when reacting with volatile amine compounds.
The successfully created ink is printed on paper inside packaging or containers for perishable protein-rich foods like fresh, processed meat and fish, stored at cool or frozen temperatures. When the food spoils, it releases volatile amines, causing the pH of the storage environment inside the packaging to change. This, in turn, alters the color of the label from red to purple to green, indicating the degree of food spoilage. With the identification of ink color, users can consider whether to use the food.
Tri stated that all fresh foods produce volatile amines. These substances typically increase pH due to their alkaline nature, so the group relied on this factor to create smart ink for detection. “With sealed packaging, the product achieves over 98% accuracy when tested with red tilapia,” Tri mentioned.
The group hopes the product will help reduce the consumption of unsafe fresh food, aiding businesses and consumers in accurately and quickly controlling food quality.
The ink changes color from red to purple to green from left to right, reflecting the level of food spoilage corresponding to storage times of 0 – 8h – 12h. (Photo: NVCC).
According to Master’s degree holder Ta Le Quoc An, a lecturer at the Food Technology Department of Saigon University of Technology, there have been many domestic studies on packaging or inks that can detect food spoilage. However, the group is among the pioneers using butterfly pea flowers to create smart ink with high applicability. He believes that this technology is completely natural and safe for food and humans.
Mr. An indicated that anthocyanin is a compound that is easily degraded when exposed to strong light and high temperatures. Therefore, for application, foods need to be stored at low temperatures and in airtight conditions. “Current packaging technologies using aluminum films and vacuum sealing can address this issue, so our product can be effectively applied to refrigerated food types,” Mr. An stated.
