Identification of bioactive peptides in commercial Australian organic cheddar cheeses

This study examined two commercial Australian organic cheddar cheeses (A and B) for the presence of antimicrobial, antioxidant and antihypertensive activities. The antimicrobial activity of the peptides was determined by the growth inhibition of Escherichia coli, Bacillus cereus and Staphylococcus aureus. The bacteria were inhibited the greatest by the whole peptide extracts derived from organic cheddar cheese A. Overall, B. cereus was inhibited the most by fractionated peptides derived from organic cheddar cheese A between >5 kDa and <10 kDa (34.6%), followed by E. coli (28%), which was inhibited the most by fractionated peptides greater than 10 kDa derived from organic cheddar cheese A. Antioxidant activity was determined by the inhibition of the free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). Overall, both organic cheddar cheese peptide extracts had similar inhibition. No significant differences (p>0.05) were observed. Antihypertensive activity was determined by inhibition of the angiotensin I-converting enzyme. Overall, organic cheddar cheese B peptides less than 5 kDa had the lowest IC50 value (0.114 mg/mL), followed closely by the fraction containing peptides between 5 kDa and 10 kDa from organic cheddar cheese B (0.122 mg/mL). This study has shown that peptides derived from Australian organic cheddar cheeses potentially have antioxidant, antihypertensive and antioxidant properties.