Development of colorimetric films based on aronia anthocyanins for the detection of food spoilage

The market for intelligent freshness indicator packaging made of bio-based materials that is also environmentally friendly has grown significantly in recent times. In this study, Aronia (AR) anthocyanins were integrated into gellan gum (GG), starch (ST), and xanthan gum (XG) matrices, which can be applied in smart food packaging. To assess how matrices and AR anthocyanins interacted, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed. The aim is to exploit the principle of color change of the produced matrices when exposed to acidic and basic gases and use the matrices as a smart colorimetric pH indicator to monitor spoilage in chicken breast. GSX-AR3 film containing 35 mg of AR extract showed significant color changes in different buffer solutions. During the chicken freshness test, a substantial change in the color of the films was observed at seventh day of storage in refrigerator conditions at +4 °C. Experimental results demonstrated that these color changes were visually distinguishable and also correlated with the total volatile basic nitrogen (TVB-N) and total viable count (TVC) results. As a crucial freshness indicator, the films' sensitivity to ammonia was demonstrated by their obvious color shift from pinkish-red to yellowish-green when exposed to the gas. The proposed intelligent indicator can be used to detect the freshness of foods with high protein content. The biodegradable and pH sensitive film has the potential to be applied in smart food packaging.