Using high-throughput instrumental measures we've been looking closely at tastant profiles and physical properties resulting from microbial fermentation in food.

The chemistry of flavour

Winvestigate the taste and aroma compounds of fermented foods that contribute to their flavour. We do this by measuring free amino acids, volatile compounds (by GC-MS), small metabolites (by NMR) and peptides that are products upon fermentation.

Amino acids and small peptides activate human taste receptors, and contribute to the distinct sensory properties that fermentation imparts on food organoleptic properties. They are important determinants of the sensory experience.

Measuring the activation of taste receptors

Small proteins and peptides are able to activate specific human taste receptors that correspond to bitter taste, savoury (umami) and creaminess (kokumi) mouthfeel. 

We measure the functional taste responseusing in vitro taste receptor cell-line assays. By correlating the biological receptor activation data with data from peptide analysis, we can build a profile of food tastiness for different microbes used for fermentation. 

The diagram above shows the taste receptor assay methodology.

Analysis of peptide contribution to taste

Peptide fingerprinting uses minimal sample preparation in combination with matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry to allow for a rapid means to differentiate fermented products based on a distinctive pattern of peptides and thus the chemical composition of different fermented products.  

We use a peptidomic approach to identify and characterise peptide sequences, and allow for further comparison of relative quantities of peptides of interestcontrasting peptide modifications between products and predict peptide functionality. 

Molecular modelling of peptide/receptor binding

Peptides typically exert their functional properties by binding to target proteins, such as receptors. Interactions of peptides with receptors can be modelled in silico to predict which peptides might bind. Using molecular docking software, virtual screening of large numbers of peptides can be done in a high throughput fashion. Examples of applications include identification of peptides that could enhance creamy mouthfeel (kokumi) through activating the calcium sensing receptor (CaSR).

Below, the images shows how molecular docking software allows us to pinpoint the position and visualise the binding of a peptide of interest within the binding pocket of the receptor.

Relationship between food structure and textural properties

Microstructure and rheology are important physicochemical properties of food, reflecting the texture of the products and influencing the mouthfeel perception. 

We characterise the microstructure of fermented products using a range of microscopic techniques such as Confocal Laser Scanning Microscopy and Cryo-Electron Scanning Microscopy. 

We measure the gelation profile and rheological properties during in situ fermentation and mechanical properties on the final fermented products. 

To assist the screening of a large number of microbes, micro-rheology device is used to compare the viscosity development.

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