Optimization and Modeling of Ultrasound- and Microwave-Assisted Extraction of Turmeric to Efficiently Recover Curcumin and Phenolic Antioxidants Followed by Food Enrichment to Enhance Health-Promoting Effects

Phenolic antioxidants and curcuminoids are biologically important molecules playing a crucial role in combating reactive species under oxidative stress conditions. In this study, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) processes for the extraction of phenolic antioxidants and curcumin from turmeric using an ethanol-water mixture were optimized and modeled with the face-centered composite design of the response surface methodology. Under optimal conditions, CUPRAC total antioxidant capacity (TAC), curcumin content (CC), DPPH free radical scavenging capacity, ABTS radical scavenging capacity, and total phenolic contents (TPC) of the extracts obtained using MAE, UAE, and automated soxhlet-assisted extraction were determined to distinguish the water ratio of the ethanolic solvent as the most important operational factor affecting TAC and CC responses. The highest TAC and CC yields were obtained at a 200 μm particle size, 100°C temperature, 30 min time, and 20% water in ethanol conditions for MAE. The highest TAC and CC yields were obtained at a 200 μm particle size, 48 min time, G = 600 W ultrasonic power, and 26% water in ethanol conditions for UAE. In addition, the red lentil (R.L.) soup was selected as a model food system and was enriched with extracts obtained by the UAE process. The effects of curcumin addition to a protein-rich food matrix, spontaneous protein-curcumin interaction, and the existence of olive oil as an oil/water emulsion delivery system in the prepared soup samples were investigated in association with simulated gastrointestinal digestion. The (R.L + water + 5% turmeric extract) sample was shown to have a higher TPC value than analogous mixtures after in vitro digestion. TPC values of enriched soup samples with olive oil were higher than those enriched without olive oil due to the potential ability of olive oil to provide solubility and stability of curcuminoids together with its potential as a phenolic source. The solubility, oil–water interfacial absorption, and stability of curcuminoids were important in the measured TAC response before and after simulated digestion. Curcumin addition to protein-rich foods may be recommended considering the health-promoting effects of functional foods. The proposed extraction processes show a potential to recover bioactive compounds with high efficiency through green chemistry to design new functional foods.