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 technique and used in the antioxidant fortification of green soybean milk. The ultrasound extraction that yielded the highest total polyphenol content and antioxidant activities was 50% amplitude for 10 min. 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 an extraction time of 10.5 min. Under these conditions, the experimental total phenolic content, total flavonoid content, and antioxidant activity were well matched with the predicted values (R2 > 0.70). 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 crude extracts, which were present at a concentration of 0.72 ± 0.01 mg/100 g. The 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.
Highlights
Free radicals shorten the shelf-life of food products as well as increase oxidative stress within cells, a recognized pathologic pathway of several chronic diseases [1]
The objectives of the present work were (1) to optimize the ultrasonicassisted extraction (UAE) process with water as eco-friendly solvent to obtain Green soybean pods (GSP) extracts enriched in antioxidants in the classes of total content of phenolic and flavonoid; (2) to investigate the antioxidant capacity of green soybean milk supplemented with GSP extracts; and (3) to identify some specific antioxidants in the GSP extracts
Water was indicated to be an efficient solvent in the ultrasound-assisted extraction of green soybean pods
Summary
Free radicals shorten the shelf-life of food products as well as increase oxidative stress within cells, a recognized pathologic pathway of several chronic diseases [1]. During the past two decades, the utilization of either bioactive compounds or natural antioxidants in food products or by-products through both non-biological [2] or biological means [3,4,5,6] has gained considerable interests due to the participating roles of these compounds in absorption and neutralization of free radicals, thereby slowing down the autoxidation process. Legumes are an excellent source of bioactive compounds with antioxidant capacity such as flavonoids, anthocyanin, and other phenolic compounds. Many researchers try to use green soybean as an alternative supplement source of bioactive compounds in food products such as butter cake [10] and cookies [11]. Green soybean pods (GSP), a by-product of green soybean processing, potentially contain natural antioxidants, but research on the antioxidant capacity of these GSP is still limited
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