Phenolic-Enriched Extracts from Lulo (Solanum quitoense) Obtained by Flash Vacuum Expansion and Incorporated into Whey Protein Concentrate Hydrogels

Lulo (Solanum quitoense) is a tropical fruit recognized for its high content of phenolic compounds and associated functional properties. However, these compounds are susceptible to degradation during processing and storage, limiting their application as food ingredients. The present study evaluated the use of Flash Vacuum Expansion (FVE) to enhance the recovery of phenolic compounds from lulo and their subsequent incorporation into a whey protein concentrate (WPC) hydrogel. Extracts obtained from untreated fruits and FVE-treated fruits were characterized in terms of moisture content, titratable acidity, total phenolic content, and color. Subsequently, the FVE extract was incorporated into a WPC hydrogel prepared by an emulsion-heat gelation method. FVE significantly increased the total phenolic content from 4.99 ± 0.41 to 25.08 ± 0.86 mg GAE g⁻¹ dry basis, representing a fivefold increase compared with the untreated extract. In addition, the treatment modified the color characteristics of the extracts, shifting from yellow-green tones toward more orange-yellow hues, reflecting the color changes induced by FVE treatment. Following incorporation into the hydrogel, the phenolic content reached 10.33 ± 0.59 mg GAE g⁻¹ dry basis. The hydrogel exhibited an intermediate yellow coloration and showed a moisture content of 77.35 ± 0.76%, water activity of 0.97 ± 0.014, and a particle size of 6.72 ± 0.90 μm. These findings demonstrate that FVE is an effective strategy for enhancing the recovery of phenolic compounds from lulo, while WPC hydrogels enable the incorporation of phenolic-rich extracts and maintain the measured physicochemical characteristics of the hydrogel. The combination of FVE and WPC hydrogel technology represents a promising approach for developing phenolic-enriched food ingredients from tropical fruits.