Improved properties of high-moisture extruded meat analogs using ultrasound-treated Nannochloropsis gaditana and chickpea protein concentrate

This research studied ultrasound treatment for improving the quality of meat analogs made from Nannochloropsis gaditana and chickpea protein concentrate (CP) via high-moisture extrusion (HME). Ultrasound was applied at three intensities (105, 158, and 210 W/cm²) and four durations (5, 10, 20, 30 min) to treat N. gaditana cells. The ultrasound treatment at 158 W/cm² for 30 min was found to result in the optimal disruption for extrusion without adhesion of cellular debris or intracellular materials to the surface. Extrudates containing ultrasound-treated N. gaditana exhibited more continuous and elongated fibers with better textural properties compared with those with untreated N. gaditana. Specific mechanical energy (SME) was negatively correlated with fibrous structure. Among them, the extrudates with 30% ultrasound-treated N. gaditana (30%-U group) had the highest fibrous degree (2.13 N/N) and the lowest SME (37.70 kJ/kg). Structural analysis showed a higher β-sheet content in the ultrasound-treated samples, contributing to protein network stabilization via enhanced disulfide and hydrogen bonding. Additionally, protein digestibility increased from 68.77-78.32% in raw samples to 75.43-84.37% after the ultrasound treatment. Sensory evaluation results indicated that acceptability of the 30%-U group was closest to commercial meat analogs, although color and flavor remained to be improved. The ultrasound treatment of N. gaditana improved the structure and nutritional value of meat analogs prepared by N. gaditana and CP, which demonstrated its potential as an emerging technology for preparing sustainable microalgae-based protein products.