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Abstract

The generation of angiotensin I-converting enzyme (ACE) inhibitory activity in soy protein isolate (SPI) was determined after sequential digestion with pepsin and pancreatin using batch or dynamic model digestion systems. During batch digestion, higher ACE inhibitory activity was measured after the first 40 and 60 minutes of pepsin digestion (E:S = 1:25, pH 2, 37°C) than after subsequent digestion with pancreatin (E:S = 1:25, pH 7.5, 37°C, 120 min). At the end of 180 minutes of batch digestion, IC5 0 values of 0.28 + 0.04, 0.30 + 0.02, and 0.36 ± 0.01 mg/mL were determined for unheated SPI, blanched (100°C, 10 min)-pasteurized (75°C, 15 s) SPI, and blanched (100°C, 10 min)-sterilized (121°C, 20 min) SPI, respectively. In general, similar trends were observed during dynamic model digestion. However, both the degree of hydrolysis and the ACE inhibitory activity were influenced in the dynamic system by controlling pH and transit time between stomach and duodenum reactors to simulate conditions in the upper gastrointestinal tract. During the first 30 minutes of dynamic model digestion, significantly (p