Lemon Essential Oil-Enriched Alginate–Gelatin Coating Preserves Bioactive Quality in Strawberries: Extraction Protocol Effects and an Exploratory Modeling Approach

Strawberries (Fragaria × ananassa) deteriorate quickly during ambient storage. This study evaluated sodium alginate–gelatin coatings, with and without lemon essential oil (LEO), on strawberry quality over five days of storage, and how the extraction protocol used to assess quality affects the resulting values. Fruits were divided into uncoated control (K), edible film (F), and LEO-enriched film (FE) groups and extracted using three solvents and two homogenization methods. Weight loss, color, microbial counts, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, total phenolic content (TPC), and individual phenolics were assessed. The FE coating was the most effective: weight loss reached 18.94% versus 28.99% in the control, and yeast and mold counts reached 1.10 versus 5.33 log CFU/g; Escherichia coli was not detected, and FE retained color closer to initial values. DPPH and TPC losses were 8.2% and 3.7% under FE versus 33.5% and 14.7% in the control, but LEO itself gave DPPH and TPC signals while the coating matrix did not, so part of this antioxidant activity reflects the oil rather than protected fruit phenolics. Individual phenolics were nearly eliminated in uncoated fruit, whereas coated fruit lost 30% or less, with similar retention in F and FE. Extraction protocol strongly affected the measured values: Ultra-Turrax outperformed sonication, and water gave the highest DPPH and TPC values and water–ethanol the lowest. An exploratory support vector regression model, not validated on independent samples, reached R2 ≥ 0.85 for 8 of 14 phenolics.