Edible colorimetric label based on immobilized purple sweet potato anthocyanins onto edible film for packaged mushrooms freshness monitoring.

An edible colorimetric label has been developed to determine the freshness level of mushrooms, i.e. white oyster mushrooms ( Pleurotus ostreatus ). The edible indicator label has been fabricated based on purple sweet potato ( Ipomoea batatas L.) anthocyanins (PSPA) immobilized onto an edible film made of chitosan and cornstarch with added PVA. The freshness parameters of the mushrooms were pH, weight loss, texture, and sensory evaluation. The results showed that the colorimetric label was dark purple when the mushroom was fresh, and turn to light purple when the mushroom was still fresh, and finally green when the mushroom was no longer fresh. The color value (mean Red) of the label was measured using the ImageJ program, where its color value (mean Red) increased with decreasing freshness level of the mushrooms. The edible label can distinguish fresh mushrooms from spoilage, making it suitable to be used in a packaged mushroom as a freshness indicator.