EFFECT OF ULTRASONIC PROCESSING ON THE TECHNO-FUNCTIONAL PROPERTIES OF AQUAFABA

Aquafaba, the liquid obtained from cooking legumes, has gained attention in the food industry for its techno-functional properties, making it a promising alternative to animal-based ingredients, particularly in emulsions and foams. These properties are attributed to proteins, polysaccharides, and low-molecular-weight compounds extracted during cooking. This study evaluated the effect of ultrasonic treatment on foaming and emulsifying properties and on the availability of sulfhydryl groups in chickpea aquafaba. Aquafaba was prepared by cooking chickpeas at a ratio of 1:5 (w/v) under pressure for 20 min. Ultrasonic treatment was performed using a UIP1000hdT processor (Hielscher, Germany) at 20 kHz and 100% amplitude, with a 34 mm probe and 270 W power. Systems with recirculation (30–120 min) and without recirculation (5–15 min) were compared. In the recirculation system, temperature was kept at 18 °C (refrigerated bath), treated volume was 2.1 L with 0.3 L removed per time point, and energy ranged from 183 to 717 kWh. In the non-recirculation system, temperature was kept below 25 °C (ice bath), 0.5 L was treated per time, and energy ranged from 29 to 89 kWh. Treatments were performed in duplicate. Foaming capacity and foam stability were assessed using an Ultra-Turrax T25 (IKA, Germany). Foaming capacity was evaluated after 2 hours, and emulsion stability after 4 hours. Emulsifying activity index and emulsion stability were determined using 60 mL of aquafaba and 20 mL of soybean oil emulsified at 9,600 rpm for 1 minute. Free sulfhydryl (-SH) were quantified using Ellman’s reagent (A₄₁₂) and Beer–Lambert law. All analyses were conducted in triplicate, and statistical significance was determined using Tukey’s test (α = 0.05). Ultrasound significantly influenced the techno-functional properties of aquafaba. Foaming capacity increased with sonication time, reaching 230 ± 0.5% (recirculation, 120 min) and 236 ± 1.8% (non-recirculation, 15 min), with foam stability above 61 ± 1.8%. These improvements are attributed to partial protein unfolding induced by acoustic cavitation, which enhances flexibility and adsorption at the air–water interface. Conversely, prolonged sonication reduced emulsifying activity and stability after 10 min, likely due to protein fragmentation and a lower capacity to form cohesive interfacial films. Free sulfhydryl content decreased from 8.18 ± 0.12 (control) to 6.03 ± 0.06 mmol of -SH·g of dry sample (120 min), indicating oxidation and disulfide bridge formation, which may promote protein aggregation. Overall, ultrasound induced structural modifications that favored foam formation and stability but offered limited benefits for emulsion systems.