Optimization of Ultrasound-Assisted Protein Extraction from Khai-Nam (Wofflia globosa) Using Response Surface Methodology

Khai-Nam (Wolffia globosa), a water meal or duckweed, is an aquatic angiosperm commonly dwell in Thailand and neighboring ASEAN countries. With its potential to provide up to 40% (w/w) of protein, Khai-Nam emerges as a promising alternative source of plant-based protein. This research aims to investigate the optimal condition of protein extraction from Khai-Nam by ultrasound-assisted extraction (UAE) method by the response surface methodology (RSM) with analytical Box-Behnken design (BBD). The experiments exhibited that these three factors affected yield of protein extraction. The optimum conditions for extracting protein were a solid-liquid ratio of 0.1:10 g/mL, ultrasound amplitudes of 100% and extraction time of 30 min; after the experiments performed under these conditions, the maximum protein yield was found to be 39.65% w/w, which is similar to the predicted value. The major amino acids in the Khai-Nam protein concentrate (KNPC) were glutamate, aspartate and leucine. Moreover, the water and oil absorption capacity of the KNPC were 6.41 ± 1.89 g water/g protein and 5.68 ± 0.09 g oil/g protein, respectively. In contrast, the maximum foamability, foaming stability, emulsifying activity, and emulsion stability were 292 ± 28.85%, 88.49 ± 0.78%, 100 ± 0.00%, and 90.83 ± 1.18%, respectively. This study suggests that Khai-Nam protein extracted with ultrasound could be a hopeful and viable alternative protein source in food systems, thereby offering a practical solution to the enhancing demand for plant-based proteins.