Ultrasonic Extraction of Bioactive Compounds From Green Soybean Pods and Application in Green Soybean Milk Antioxidants Fortification

Abstract

Green soybean (Glycine max L.) pods (GSP) are agro-industrial waste from the production of frozen green soybean and milk. These pods contain natural antioxidants and various bioactive compounds that are still underutilized. Polyphenols and flavonoids in GSP were extracted by ultrasound techniques and used in antioxidant fortification of green soybean milk. The ultrasound extraction that yielded the highest total polyphenol content was 50% amplitude for 10 min, whereas maximum flavonoids content was obtained at 50% amplitude for 15 min. Radical scavenging activity assayed by 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH) and ferric reducing antioxidant power (FRAP) methods did not differ significantly (p>0.05) between the two conditions. Response surface methodology was applied to analyze an optimum ultrasonic-assisted extraction (UAE) condition of these variables. The highest desirability was found to be 50% amplitude with extraction time of 12.5 min. Fortification of the GSP extracts (1-3% v/v) in green soybean milk resulted in higher levels of bioactive compounds and antioxidant activity in a dose-dependent manner. Procyanidins were found to be the main polyphenols in dried GSP which were present at the concentration of 104.1 ± 2.1 mg/g dry sample, respectively. Addition of GSP extracts obtained by using an ultrasound technique to green soybean milk increased its bioactive compound content especially procyanidins as well as its antioxidant activity.