30C-17 |
Characterization of isoflavones in membrane processed soy protein concentrate |
H. P. BATT and R. L. Thomas. Department of Packaging Science, Clemson University, B-212 Poole Agricultural Center, Clemson, SC 29634-0370 Isoflavones are asserted to be antioxidants, anti-carcinogenic, anti-osteoporotic, and phytoestrogenic. The chemical forms in which the isoflavones occur are important considerations because they influence absorption and thus bioactivity. Varying treatment conditions to prepare membrane processed soy protein concentrates (MSC) was thought to influence isoflavone content, distribution, and conjugation. Commonly, soy flour is packaged in polyethylene lined Kraft bags. Packaging materials were hypothesized to influence isoflavone stability. The goal of this study was to characterize the isoflavone content, distribution, and form in three differently prepared MSCs, and to analyze stability when packaged in low-density polyethylene (LDPE). Five percent (w/w) soy flour solutions were treated at: (1) 45-50°C for three hours without pectinase, (2) 45-50°C for three hours with pectinase (0.9% v/v), or (3) blanched at 80°C for three hours. Solutions were ultra- and dia-filtered to produce MSCs. Isoflavone contents were analyzed via HPLC. Two different batches of MSCs were stored for 6 and 11 months, each in LDPE. Isoflavone concentrations of each were tested at different intervals to detect any degradation. Total isoflavone concentrations (dry weight basis) of MSCs were 3.13 mg/g (no enzyme), 3.05 mg/g (pectinase), or 3.42 mg/g (blanching). These did not represent significant differences (P<0.05). These values reveal that membrane processing contributed to approximately 15%, 18%, or 8% decreases, respectively, in total isoflavone contents of MSCs compared to soy flour (3.70 mg/g). After prolonged storage, there were no significant decreases in total isoflavone contents of any of the MSC packaged in LDPE. It was concluded that the chemical form of the isoflavone did not influence total isoflavone concentration. With a recovery of at least 82% of the total isoflavones, membrane processing produced high quality soy protein concentrates with significant concentrations of isoflavones. Moreover, the results indicated that the isoflavones in MSCs were stable after prolonged storage in LDPE.
Session 30C, Food Chemistry: Proteins
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