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Identifying key interactions to reduce astringency of novel food proteins
Closing date
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Supervisors
Prof. Guy Carpenter, guy.carpenter@kcl.ac.uk, Professor Guy Carpenter (PI) has been studying saliva and salivary glands for 25 years at King’s College London. , King’s College London
Dr. James Garnett, james.garnett@kcl.ac.uk, Dr. Garnett is a senior lecturer in Structural Bacteriology in the Centre for Host-Microbiome Interactions., King’s College London
Project Details

The development of new plant-based or synthetic sources of protein for human consumption is a major aim of the BBSRC as part of the Bioscience for sustainable agriculture theme.  To date, the need for high protein foods has been achieved by increased animal farming but the environmental impact of this is now being realised.  As a consequence, a recent development has been the formulating of synthetic proteins and the increased use of plant-derived proteins in the creation of structured foods. 

Improving the consumer liking of these new foods is essential to their acceptance and growth of this new industry, in which the UK is a leading player.  However, the development of novel food proteins has reached a bottleneck as many of these types of protein cause excessive oral astringency when consumed. 

Astringency is the dry, puckering sensation in the mouth often associated with tannins in tea and wine.  At low levels astringency can be a refreshing sensation that is enjoyed by the consumer but at higher levels, it is inhibitory to ingestion.  The mechanism of how tannins cause astringency is reasonably well understood.  Phenol rings within the catechins (which are the main polyphenols in tea and wine) stack onto proline-rings within salivary proteins such as Proline-rich proteins and mucins by hydrophobic-hydrophobic interactions.  This binding then causes a reduction in oral lubrication possibly by depleting the hydration layer around the salivary proteins and a loss of lubrication.  This loss of lubrication is perceived as dryness, even though the liquid is still in abundance. 

For protein-induced astringency, we only have limited data for whey protein, derived from milk, which is commonly used for muscle-building/ nutrition drinks.  Whey proteins are astringent by forming electrostatic interactions with salivary proteins although the evidence relates only to in vitro experiments and not completely understood. It is likely that electrostatic interactions are important in causing astringency as a number of chemicals can also cause the same sensation.  Alum, for example, is a hydrated aluminium sulphate salt which is widely known to cause astringency and does so by affecting the conformation of salivary proteins to affect their lubrication. 

As yet there are no known receptors for astringency and the perceived dryness is assumed to be detected by altered touch and proprioreceptor activation in the mouth. If we can understand the nature of the interactions between food proteins and salivary proteins it may be possible to screen potential new food proteins of likely astringency and develop methods ot modify the protein to reduce these interactions.  This is of particular importance to Motif as they will be screening large numbers of potential proteins for development as food proteins.

Thus the overall aim of this project is to identify the mechanism of oral astringency caused by food proteins.  To achieve this aim we will test the hypothesis that electrostatic interactions are the main interface between food proteins and salivary proteins.  To achieve this the objectives for the project are:

  1. To confirm electrostatic interactions between food proteins and salivary proteins
  2. Identify protein motifs that create charge interactions
  3. Examine the role of counter ions in disrupting astringency

To conduct this project the student will combine physiology with protein biochemistry and use structural biology to examine the nature of the interactions in detail.

References

Gardner A, So PW, Carpenter GH. 2020. Intraoral microbial metabolism and association with host taste perception. Journal of Dental Research. 99(6):739-745.

Harper RA, Petersen L, Saleh MM, Proctor GB, Carpenter GH, Gambogi R, Hider R, Jones SA. 2019. Targeting macrophages and their recruitment in the oral cavity using swellable (+) alpha tocopheryl phosphate nanostructures. Nanomedicine-Nanotechnology Biology and Medicine. 21

Ramos-Pineda AM, Carpenter GH, Garcia-Estevez I, Escribano-Bailon MT. 2020. Influence of chemical species on polyphenol-protein interactions related to wine astringency. Journal of Agricultural and Food Chemistry. 68(10):2948-2954

Powell J, Garnett JP, Mather MW, Cooles FAH, Nelson A, Verdon B, Scott J, Jiwa K, Ruchaud-Sparagano MH, Cummings SP et al. 2018. Excess mucin impairs subglottic epithelial host defense in mechanically ventilated patients. American Journal of Respiratory and Critical Care Medicine. 198(3):340-349.

Schruf E, Schroeder V, Le HQ, Schonberger T, Raedel D, Stewart EL, Fundel-Clemens K, Bluhmki T, Weigle S, Schuler M et al. 2020. Recapitulating idiopathic pulmonary fibrosis related alveolar epithelial dysfunction in a human ipsc-derived air-liquid interface model. Faseb Journal. 34(6):7825-7846.

Garnett JP, Kalsi KK, Sobotta M, Bearham J, Carr G, Powell J, Brodlie M, Ward C, Tarran R, Baines DL. 2016. Hyperglycaemia and pseudomonas aeruginosa acidify cystic fibrosis airway surface liquid by elevating epithelial monocarboxylate transporter 2 dependent lactate-h+ secretion. Scientific Reports. 6

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