Edible pH sensor based on immobilized red cabbage anthocyanins into bacterial cellulose membrane for intelligent food packaging

An edible pH sensor has been developed based on anthocyanins of red cabbage (Brassica oleraceae var capitata L.) (ARC) immobilized on a bacterial cellulose (BC) membrane. The polivinyl alcohol (PVA) (1%) was added into the membrane to reduce swelling and water solubility. The edible pH sensor exhibited a various distinctive colors from red to purple, blue-gray, and then to yellow in the pH range (pH 1-14), with good linearity between pH 1-6, and pH 8-12, with a sensor response time of 4 min and reproducibility of <1% (RSD). The sensor showed obvious color turning as a pH response and excellent color stability after 17 and 22 days in room and chiller conditions, respectively. In application, the pH sensor was demonstrated by the detection of several beverage pH. Although as freshness sensor, milk freshness was monitored by a distinctive color turning from blue-gray to pinkish-gray after 8 h storage at room temperature. The edible pH sensor can distinguish fresh milk from spoilage, making it suitable to be used in an intelligent packaging system as a freshness sensor.