Effect of Freeze-Drying Process on the Property of Angiotensin I-Converting Enzyme Inhibitory Peptides in Grey Oyster Mushrooms

Abstract

The effect of freeze-drying on the properties of angiotensin I-converting enzyme (ACE) peptide inhibitors in mushrooms was investigated. At least a two-fold higher amount of protein was extracted from freeze-dried compared to fresh fruiting bodies. Proteomic analysis showed freeze-drying has preserved a wide range of proteins in mushroom, including low abundance proteins which could be potential ACE inhibitors. The ACE inhibitory activity of proteins was not lost by freeze-drying. Therefore, freeze-drying could be applied for industrial-scale drying of mushroom fruiting bodies for the extraction of ACE inhibitory peptides from food for the production of functional foods and nutraceuticals.

Keywords:

• Bioactive peptides
• Edible mushroom
• Hypertension
• SDS-PAGE
• SELDI-TOF-MS

ACKNOWLEDGMENTS

The authors would like to thank the University of Malaya (Grant PPP: PS238/2008C, PS478/2010B, PV073-2011B) and the Ministry of Higher Education Malaysia (HIR-MOHE: F000002-21001) for financial support of this project. Expert advice from Dr. Deen Kuthubutheen, Adjunct Professor of Mushroom Research Centre, University of Malaya, is greatly appreciated.

Notes

*ND: ACE inhibitory activity was not detected at the concentration tested; i.e., 25 µg/ml.

Values (mean ± standard deviation, n = 3) with different superscript letters within a column are significantly different (p < 0.05).

^a Proteins with similar molecular mass were clustered during EDM analysis. The m/z value for each protein cluster is presented as mean ± standard deviation (n = 4).

^b Values with p < 0.01 indicate the protein peaks were statistically significant in the four samples.

^c Peak intensities are presented as mean ± standard deviation (n = 4).

ND: Peaks were not detected. Intensities of ND peaks were only estimated values for clustering purposes during EDM analysis. Thus, their intensities were not shown.