Optimization of anthocyanin extraction by different methods and its use in the production of a colorimetric H indicator

In this dissertation, the extraction of anthocyanins from the peels of damson and Japanese ornamental plums was optimized using traditional, ohmic heating assisted, and subcritical water extraction methods through the response surface methodology. The highest anthocyanin content in extracts was obtained using the ohmic heating method, with 689.27 mg/L for damson plum peels at 60°C and 90 V, and 498.95 mg/L for Japanese ornamental plum peels at 67°C and 94 V. The anthocyanin extract produced under optimal conditions in the ohmic heating assisted method was spray-dried at an inlet temperature of 140°C, an outlet temperature of 60°C, with 10% maltodextrin, 75% air feed rate, and 30% solution feed rate. For the production of nanofibers with colorimetric pH indicator properties, anthocyanin-rich powdered extract (1.0 g) was added to a PVA/chitosan/glycerol polymer solution (70/27/3% by weight). This solution was subjected to electrospinning under conditions of 22 kV, a flow rate of 1 mL/h, a 15 cm distance between the feeding and collecting chambers, an ambient temperature of 23.9°C, and 36.6% relative humidity. The integration of anthocyanins into the nanofibers and the quality of the produced nanofiber as a pH indicator were determined using SEM, XRD, FTIR, DSC, and TG/DTA analyses. The potential use of the nanofibers as colorimetric pH indicators in food packaging was evaluated with chicken (thigh) and fish (salmon fillet) samples. During the storage period for 12 days, microbial growth increased in the samples, reaching levels of 8.8×10⁵ and 2.3×10⁹ in chicken and fish samples, respectively, by the end of the sixth day of storage. In fish samples, the initial pH value (6.30) decreased to 5.28 by the end of storage, and total color change (ΔE*) was calculated as 51.27. In chicken samples, the initial pH value of 6.40 increased to 7.05 by the end of storage, and ΔE* was 45.71. This change was visually reflected as "a noticeable color difference" in nanofibers. The study demonstrated that anthocyanins from damson and Japanese ornamental plum peels can be efficiently extracted using the ohmic heating assisted method and integrated into nanofibers to serve as an effective colorimetric pH indicator, offering an innovative approach for monitoring food freshness and safety.