Detection of Oenological Polyphenols via QCM-D Measurements

Abstract

Polyphenols are a family of compounds present in grapes, musts, and wines. Their dosage is associated with the grape ripening, correct must fermentation, and final wine properties. Owing to their anti-inflammatory properties, they are also relevant for health applications. To date, such compounds are detected mainly via standard chemical analysis, which is costly for constant monitoring and requires a specialized laboratory. Cheap and portable sensors would be desirable to reduce costs and speed up measurements. This paper illustrates the development of strategies for sensor surface chemical functionalization for polyphenol detection. We perform measurements by using a commercial quartz crystal microbalance with dissipation monitoring apparatus. Chemical functionalizations are based on proteins (bovine serum albumin and gelatin type A) or customized peptides derived from istatine-5 and murine salivary protein-5. Commercial oenological additives containing pure gallic tannins or proanthocyanidins, dissolved in water or commercial wine, are used for the analysis. Results indicate that selected functionalizations enable the detection of the two different tannin families, suggesting a relationship between the recorded signal and concentration. Gelatin A also demonstrates the ability to discriminate gallic tannins from proanthocyanidins. Outcomes are promising and pave the way for the exploitation of such devices for precision oenology.

Keywords: acoustic wave sensor; biosensor; functionalization; polyphenols; precision oenology; quartz crystal microbalance.

Figure 1

QCM-D functionalization strategies: (a) two-steps functionalization with proteins, (b) functionalization with peptides.

Figure 2

QCM traces of functionalization with (a) proteins, (b) peptides; in functionalization with proteins, 1: injection of the 12-MCA solution, 2: rinsing with EtOH/water, 3: rinsing with water, 4: injection of the protein solution (in this example, BSA), 5: rinsing with water; in functionalization with peptides, 1: injection of the peptide solution (in this example, MP-5), 2: rinsing with water.

Figure 3

Characterization of SAM: (a) Δf (F3), (b) ΔD (D3), and (c) molar areal mass calculated with the Sauerbrey model; the number of experiments for the statistical analysis is 39 for BSA, 32 for Gel-A, and 30 for Ist-5 and MP-5. Red crosses are values out of the interquartile range multiplied by 1.5.

Figure 4

Detection of polyphenols in watery solutions: Δf vs. sample concentration (see Table 1) in (a) BSA, (b) Gel-A, (c) Ist-5, (d) MP-5.

Figure 5

Detection of polyphenols in watery solutions containing TG: Δf vs. tannin concentration in (a) proteins, (b) peptides; Δf vs. pH in (c) proteins, (d) peptides.

Figure 6

Detection of polyphenols in winery solutions: Δf vs. sample nomenclature in (a) proteins, (b) peptides.

Figure 7

Detection of polyphenols in samples with gallic tannins added (samples G and H, Table 2): (a) as a function of measured polyphenols concentration, (b) as a function of measured pH.