Presence of Tripeptides VPP and IPP in Curd
Yes, curd contains the bioactive tripeptides Valine-Proline-Proline (VPP) and Isoleucine-Proline-Proline (IPP), which are formed during the fermentation process of milk products. 1, 2
Formation of Tripeptides in Curd
Curd, as a fermented milk product, undergoes bacterial fermentation that leads to the formation of these bioactive peptides:
- VPP and IPP are produced during milk fermentation through the proteolytic activity of lactic acid bacteria on milk proteins (caseins)
- These tripeptides are classified as ribosomally synthesized and post-translationally modified peptides (RiPPs) 3
- The fermentation process breaks down larger milk proteins into smaller peptide fragments, including these specific tripeptides
Biological Activity of VPP and IPP
These tripeptides have demonstrated several biological properties:
- ACE (Angiotensin-Converting Enzyme) inhibitory activity in vitro 1, 2
- Potential antihypertensive effects in animal models 1, 2
- Ability to induce nitric oxide (NO) production in endothelial cells 4
- Endothelium-dependent relaxation of isolated aortic rings 4
Concentration in Different Fermented Products
The concentration of these tripeptides can vary based on:
- The specific fermentation process used
- The bacterial strains involved in fermentation
- Duration of fermentation
- Processing methods (e.g., sun drying vs. freeze-drying) 5
Research has shown that different fermented milk products contain varying amounts of these peptides:
- In one study, the calculated intake of IPP was 0.4 mg/d and 0.2 mg/d in different fermented milk products, while the corresponding amounts for VPP were 0.6 mg/d and 0.3 mg/d 2
Clinical Relevance
Despite their presence in curd and other fermented milk products, the clinical significance of these tripeptides remains debated:
- While animal studies show potential antihypertensive effects 1, 2, human studies have shown mixed results
- Some research indicates that these peptides may be poorly absorbed and rapidly eliminated in humans 6
- One human study found that these peptides did not inhibit plasma or endothelial ACE in vivo at the doses tested 6
Practical Implications
For those interested in the potential health benefits of these tripeptides:
- Traditional fermented milk products like curd are natural sources of VPP and IPP
- The bioactivity of peptide fractions can be influenced by processing methods and salt content 5
- Commercial fermented milk products with standardized amounts of these peptides are available in some markets
In conclusion, while curd does contain the tripeptides VPP and IPP as a result of the fermentation process, their bioavailability and clinical effects in humans require further investigation to fully establish their health benefits.