Innovative Soaking and Grinding Methods and Cooking Affect the Retention of Isoflavones, Antioxidant and Antiproliferative Properties in Soymilk Prepared from Black Soybean

• Published in: Journal of food science Vol. 81; no. 4; pp. H1016 - H1023
• Main Authors: Tan, Yingying, Chang, Sam K. C., Zhang, Yan
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01-04-2016; Wiley Subscription Services, Inc
• Subjects: Antineoplastic Agents, Phytogenic - analysis; Antineoplastic Agents, Phytogenic - pharmacology; Antineoplastic Agents, Phytogenic - therapeutic use; antioxidant capacity; Antioxidants; Antioxidants - analysis; Antioxidants - pharmacology; antiprostate cancer proliferation; Biphenyl Compounds - metabolism; black soybean; Cancer; Cell Line, Tumor; Cooking; Flavonoids - analysis; Flavonoids - pharmacology; Flavonoids - therapeutic use; Food Handling - methods; Glycine max - chemistry; Heating; Humans; Isoflavones; Isoflavones - analysis; Isoflavones - pharmacology; Isoflavones - therapeutic use; Male; Methods; phenolics; Phenols - analysis; Phenols - pharmacology; Phenols - therapeutic use; Picrates - metabolism; Plant Extracts - pharmacology; Plant Extracts - therapeutic use; Prostate; Prostate cancer; Prostatic Neoplasms - diet therapy; Prostatic Neoplasms - drug therapy; Raw; Soy Milk - chemistry; Soy products; Soya bean milk; Soybeans; soymilk processing; Water; black soybean; isoflavones; antioxidant capacity; antiprostate cancer proliferation; soymilk processing; phenolics
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/1750-3841.13266

This study's objective was to characterize the effect of traditional and 3 newly devised (soaking+grinding) methods combined with cooking on the content and composition of phenolic substances, antioxidant, and antiproliferative properties of soymilk prepared from black soybean. Phenolic substances and antioxidant profile were characterized and antiproliferation of prostate cancer DU145 cells was conducted using a cell culture assay. Results indicated Grinding Method 4 produced significantly (P < 0.05) higher total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC), and total isoflavone content in both raw and cooked black soymilk as compared to Method 1. Cooking soymilk reduced 23% to 38% of total phenolic substances. Raw black soymilk produced by Method 4 displayed the highest antioxidant capability, which was determined using ORAC, FRAP, and DPPH assays, and a higher antiprostate cell proliferation ability. Cooking only slightly reduced the potency to inhibit DU145 prostate cancer cells as IC50 value was increased from the average of about 4.0 mg/mL of raw soymilk extracts to 5.5 mg/mL of cooked soymilk extracts of all grinding methods. Overall, total isoflavone content was the only component that was negatively correlated with IC50 value (r = –0.93, P < 0.05) which indicates the ability to inhibit prostate cancer cell is associated with the increase in total isoflavone content, not with any other phenolic substances or antioxidant properties.
Practical Application
Soymilk is becoming popular to the consumers due to its potential health benefits that are derived from isoflavones and other phenolic substances. Black soybean has potential medicinal value. Soaking and grinding are the major steps in soymilk processing that can significantly affect the retention of the bioactive components. This study demonstrates that a newly devised grinding method could significantly improve isoflavone content, phenolic contents, antioxidant activities, and antiproliferative effects against DU 145 cells of the soymilk. These innovative methods could be utilized in the soymilk industry to promote potential health benefits to the consumers.