Optimization and kinetics modeling of okara isoflavones extraction using subcritical water. (15th October 2019)

• Record Type: Journal Article
• Authors: Nkurunziza, David; Pendleton, Phillip; Chun, Byung Soo
• Is Part Of: Food chemistry. Volume 295(2019)
• Page Start: 613
• Page End: 621
• Publication Date: 2019-10-15
• Subjects: Subcritical water -- Isoflavones -- Aglycones -- Glucosides -- Response surface methodology -- Kinetics modeling; Food -- Analysis -- Periodicals; Food -- Composition -- Periodicals; 664
• DOI: 10.1016/j.foodchem.2019.05.129
• Languages: English
• ISSNs: 0308-8146

Abstract

Highlights: Subcritical water extraction of isoflavones from okara byproducts was optimized. Conjugated isoflavones were less stable to hydrolysis as compared to aglycones. Prolonged extraction time enhanced maximum aglycone recovery up to 213.5 ± 8.7 min. Kinetic models for isoflavone degradation and conversion reactions were developed. Abstract: In this study, the soybean milk and tofu byproduct okara was subjected to subcritical water extraction with the intention of recovering isoflavones with minimal degradation. Response Surface Methodology (RSM) of the extraction variables indicated that optimized conditions would be T = 146.23 °C, P = 3.98 MPa, and α = 20 mg (solid)/mL (extractant). Mathematical models for the conversion and degradation of isoflavones were solved as a set of simultaneous equations leading to rate constants and time-dependent concentration profiles for each genistein- and daidzein-based compound. These kinetic analyses suggested that an optimum extraction time, under RSM-optimized conditions, would be 213.5 ± 8.7 min. The results of our study suggest that okara byproducts could be valorized efficiently, as a source of bioactive isoflavone aglycones, using subcritical water. The mathematical models and optimized extraction conditions that we established in this study could be employed, as process control-optimized variables, in the exploitation of okara, specifically in the isolation of genistein and daidzein.