Title
Real time monitoring of meat freshness based on natural resources
Authors
EMINE ARMAN KANDIRMAZ, URŠKA KAVČIČ, ARIF OZCAN, GREGOR LAVRIČ and IGOR KARLOVITS

Received October 7, 2025
Published Volume 60 Issue 1-2 January-February
Keywords freshness indicator, nanocellulose, smart label, hydrogel, anthocyanin

Abstract
Food spoilage leads to both food waste and consumer health damage. Smart packaging systems inform the consumer about food spoilage and prevent food waste by consuming at the right time. Considering this and consumers’ increasing preference for natural packaging materials for food products, in this study, it was aimed to produce smart packaging elements using naturally sourced cellulose derivatives and black carrot anthocyanins. Two types of nanocelluloses, namely bacterial nanocellulose (BNC) and TEMPO-oxidized cellulose nanofibrils (CNF), were synthesized from natural resources using different production methods. Black carrot was used to extract anthocyanin, a pH-responsive pigment. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to examine the chemical structures of BNC, CNF, and anthocyanin. The total anthocyanin content (TAC) in the black carrot extract was determined by UV spectroscopy. Thus, it was concluded that the colored substance obtained from black carrots had the cyanine 3-O glucoside structure and its total anthocyanin content was 469±35 mg/100 g. Also, the color changes of anthocyanin in response to pH alterations were investigated.
Hydrogels were prepared based on BNC and CNF, separately, with Zn2+ used as crosslinker, and then these hydrogels were impregnated with the anthocyanin dye. Using ATR-FTIR, the chemical structure of the hydrogels loaded with anthocyanins was examined. Also, their swelling index was calculated and it was noted that BNC had a 15% higher swelling index. The morphology of the hydrogels was investigated using scanning electron microscopy (SEM). Then, printable hydrogel suspensions were prepared from BNC, CNF, and anthocyanins, to develop intelligent pH sensitive labels. These suspensions were used to print on paper using the screen-printing technique. An X-Rite spectrophotometer was used to analyze the color characteristics of the printed hydrogel suspensions in both basic and neutral settings. The cumulative release of anthocyanin from the CNF and BNC-based smart labels in ethyl alcohol was also examined in this work. It was determined that the anthocyanin released from BNC hydrogel was 3% higher than from CNF. The ability of these novel colorimetric freshness indicator labels to identify deterioration in minced beef was evaluated. It was observed that, with the change of ambient pH, the color changes of the printed labels can be detected both spectrally and visually. Thus, the color of the hydrogel ink on the labels changed from pink/purple to blue as the meat deteriorated, indicating the potential of these smart labels as spoilage indicators. According to the study's findings, these smart labels can serve as useful freshness labels for meat products, providing a useful application for materials derived from natural resources and advancing environmentally friendly packaging technology.