Starch sensor tracks moisture-linked loss of cracker crispness in packaging tests
Researchers at the University of São Paulo’s São Carlos Institute of Chemistry developed a porous starch-based sensor that shifts from blue to pink as humidity rises and reverses as it falls. In cream-cracker packaging tests, the color response tracked increased moisture associated with loss of texture. The current cobalt chloride formulation is toxic and cannot directly contact food, so further work is needed before commercial use.
The story
Brazilian researchers led by scientists at the São Carlos Institute of Chemistry at the University of São Paulo developed a biodegradable moisture sensor made from a starch-based cryogel containing cobalt chloride. The small porous sensor changes from blue when dry to pink after absorbing water vapor; the change reverses as humidity falls. According to the researchers, freezing and freeze-drying the starch gel preserves a porous structure that increases its interaction with the surrounding environment. The team tested the sensor near cream crackers, a product that is sensitive to moisture and can lose crispness under unsuitable storage conditions. In those tests, increasing moisture corresponded with the sensor’s color change and was strongly correlated with texture loss in the crackers. The device changed through blue and pink shades within seconds, allowing the response to be read by eye and potentially by a cellphone camera. The results were published in Food Chemistry in June 2026. The researchers describe the sensor as a possible way for manufacturers or consumers to monitor moisture and crispness in packaged foods, but they stress that it is not ready for direct food contact.
Why it matters
Moisture can alter the expected texture of dry packaged foods before the change is obvious from the outside of a package. A reversible visual indicator placed near, rather than in, the food could offer a direct sign that conditions inside a package have become more humid. The reported result is especially relevant because the signal tracked a quality characteristic—cracker texture—rather than humidity alone. However, the study does not establish that the sensor can determine food safety, shelf life, or the quality of foods other than those tested.
Evidence and context
The sensor combines two established material functions: a porous starch cryogel provides a large surface for interaction with the package environment, while cobalt chloride supplies the humidity-responsive color change. In the reported mechanism, dry cobalt chloride appears blue and shifts pink when hydrated because water changes its chemical structure. The study places this combination in food packaging and compares its response with cream-cracker texture under changing moisture conditions. The research group is also evaluating other indicator materials, including compounds derived from jabuticaba peel. Those natural pigments are described as pH-sensitive and are being considered for a separate system intended to monitor meat spoilage.
Limits and unknowns
The reported evidence comes from tests involving cream crackers, so performance with other foods, package formats, and real distribution conditions remains unresolved. The sensor’s key limitation is cobalt chloride: the researchers say it is toxic and therefore cannot touch food directly. They state that conventional packaging would need redesigning for commercial use and that further studies are needed. The source does not provide a food-safe replacement, a commercial packaging design, or evidence that the device has been tested at manufacturing scale.
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Research publication
The study, “Starch-based cryogels incorporating cobalt chloride as colorimetric moisture sensors for food packaging,” was published in Food Chemistry.
Starch sensor tracks moisture-linked loss of cracker crispness in packaging tests
A short visual explainer for readers who want the story in a different rhythm.
Highlights
- Blue to pink as humidity rises
- Color tracked cracker texture loss
- Porous starch reacts in seconds
- A potential early quality check
Transcript
Brazilian researchers made a tiny starch sensor that turns from blue to pink as package humidity rises.
In cream-cracker tests, that shifting color closely tracked the moisture linked to crackers losing their familiar crispness.
Its freeze-dried starch structure is full of pores, helping the indicator react within seconds to water vapor.
It still needs a food-safe formula, but the visible signal could make snack freshness easier to check.
Follow for practical science stories that show how small material breakthroughs may improve everyday products over time.