Enhancing Antioxidant and Storage Stability of Upcycled Fruit Bars Through NADES-Based Lavender Extract Addition

This study investigated the development of upcycled functional fruit bars based on dates or figs and grape pomace, enriched with a lavender extract obtained using a novel multicomponent natural deep eutectic solvent (NADES). Supplementation with the NADES-based lavender extract significantly increased the total polyphenol content and antioxidant capacity, while improving the retention of total polyphenols during storage by approximately 10.3% in date-based bars and 2.8% in fig-based bars. The NADES-based lavender extract also reduced the percentage of yeast- and mold-positive samples from 60% to 20% in date-based bars after 30 days of storage at 22 °C. After 28 days of storage, supplemented bars showed better preservation of key sensory attributes, including appearance, color, odor, sweetness, bitterness and aftertaste. The stabilizing effects were more pronounced in date-based than in fig-based formulations, highlighting the influence of the food matrix on functional ingredient performance. Overall, the results indicate that NADES-based lavender extract is a promising functional ingredient for improving the physicochemical, sensory, and microbiological stability of upcycled fruit bars, particularly in date-based formulations.