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. 2025 Aug 13;9(1):174.
doi: 10.1038/s41538-025-00451-6.

An in vitro study exploring the role of mucin in the protein-flavor binding mechanism

Cristina Barallat-Pérez  1 , Emma Khazzam  2 , Hans-Gerd Janssen  2   3 , Sara Martins  2   4 , Vincenzo Fogliano  2 , Teresa Oliviero  5
Affiliations

An in vitro study exploring the role of mucin in the protein-flavor binding mechanism

Cristina Barallat-Pérez et al. NPJ Sci Food. .

Abstract

In the mouth, food flavors interact with salivary proteins like mucin, which protects mucosal surfaces and influences the rate of aroma release. The role of mucin in the protein-flavor binding mechanism was evaluated in a model system in vitro using GC-MS. The number of binding sites (n) and binding constants (K) of commercial food protein isolates (PIs) and carbonyl compounds were calculated using Klotz plots. Results suggested a linear relationship between PIs and carbonyl compounds, where K increased with the flavor chain length, and n ranged from n = 0.021 to 7.194. Mucin addition to flavor-protein systems increased flavor binding up to fifteen times. At 0.01(w/v)% mucin, structural changes enhanced flavor binding. At higher mucin levels, further unfolding leads to aggregation, restricting access of the flavor molecules to the binding sites. These results confirmed the role of flavor structural characteristics and mucin on flavor binding, essential for optimal food design.

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Conflict of interest statement

Competing interests: H.-G.J. is employed by Unilever, a multinational consumer goods company. The other authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Klotz plots for binding of carbonyl compounds to commercial food protein isolates (PIs).
Whey (WPI) (A, B) soy (SPI) (C, D) and lupin (LPI) (E, F) protein isolates. Plots were calculated following Eq. (1). To optimize data visualization, scales are adjusted differently for the X-axis (1/[L], being L the free ligand concentration in the aqueous phase) and the Y-axis (1/v, being v the number of moles of ligand bound per mole of total protein). These adjustments are made based on their respective maximum responses.
Fig. 2
Fig. 2. Effect of mucin (M) (0.01(w/v)%) on the protein-flavor binding mechanism.
The influence of mucin was studied in A Protein-aldehyde-based aqueous model systems (PAB) and B Protein-ketone-based aqueous model systems (PKB) increasing in chain length from C6 to C10 The abbreviations “A_” and “K_” indicated the chemical class (aldehydes or ketones), followed by the chain length. Binding (%) was calculated following Eqs. (2) and (3). Results are expressed as the mean ± standard deviation. Letters denote significant differences (p  <  0.05). Treatments with the same letter are not significantly different.
Fig. 3
Fig. 3. Effect of mucin (M) 0.1(w/v)%, on the protein-flavor binding mechanism.
The abbreviation “K_” indicated the chemical class (ketones), increasing in chain length from C6 to C10. Binding (%) was calculated following Eq. (3). Results are expressed as the mean ± standard deviation. Letters denote significant differences (p < 0.05). Treatments with the same letter are not significantly different.
Fig. 4
Fig. 4. Mechanism of mucin interaction in flavored protein-based aqueous systems (FPBAS).
A Mucin–protein interaction mechanism in FPBAS at low mucin concentration (0.01(w/v)%). B Corresponding mechanism observed at medium to high mucin levels (0.1(w/v)%). Adapted from Brown et al. [52].
See this image and copyright information in PMC

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