This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Brazilian researchers have developed a biodegradable, starch-based sensor that changes color when moisture enters food packaging. With the addition of cobalt chloride, the sensor changes from blue to pink as moisture levels rise and back to blue as they fall.
Consumers and manufacturers could use it to monitor the quality and crispness of foods such as cookies with the naked eye or a cellphone camera, without complex equipment. The research was led by scientists at the São Carlos Institute of Chemistry at the University of São Paulo (IQSC-USP), and the results were published in June in the journal Food Chemistry. The researchers began testing with cream crackers, which are highly sensitive to moisture and quickly lose their crispness when stored under inappropriate conditions.
The results showed that the color change corresponded to an increase in moisture, which was strongly correlated with a loss of texture in the crackers. This indicates that the sensor reflects changes in storage conditions. In just a few seconds, the small, starch-based cylinder placed near the crackers changes color, shifting among shades of blue and pink.
When the cobalt chloride is dry, it turns blue. When it absorbs water vapor, it turns pink. This happens because hydration changes the chemical structure of cobalt chloride and, consequently, its color.
"What set this study apart was having a larger surface area for the sensor, making it highly sensitive and allowing us to observe different humidity conditions inside the packaging. If I place it in a very dry environment, it responds. Conversely, if I place it in a very humid environment, it also responds," explains Bianca Maniglia, a professor at IQSC-USP and the research adviser.
The researchers expect that the industry and consumers will eventually be able to use the technology to determine the crispness and moisture content of various products. The idea to use cobalt chloride to create the sensor came from a childhood memory. While developing the project, Maniglia recalled the "weather rooster," a kitchen ornament inspired by the "Rooster of Barcelos," one of Portugal's national symbols.
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