# Hypersensitive quantification of major astringency markers in food and wine by substoichiometric quenching of silicon-rhodamine conjugates

## TL;DR

A new method using silicon-rhodamine conjugates can detect tannins in food and wine with high sensitivity and selectivity.

## Contribution

First evidence of tannin-induced quenching of silicon-rhodamine fluorophores for astringency marker quantification.

## Key findings

- Tannic acid detection limit was as low as 500 pM with a linear range of 5–100 nM.
- The assay showed high selectivity for tannic acid and catechin-3-gallate over other polyphenols.
- Validation in 18 red wine samples demonstrated strong linearity with methylcellulose precipitation.

## Abstract

Tannins are chemically diverse polyphenols in plant-derived products that not only show diverse biological activities but also play a crucial role in determining the sensory attributes of food and beverages. Therefore, their accurate and cost-effective quantification is essential.

Here, we identified a novel fluorescence quenching mechanism of different synthetic rhodamine fluorophores, with a high selectivity towards tannic acid (TA) and catechin-3-gallate (C3G) compared to a structurally diverse panel of tannins and polyphenols. Specific chemical conjugates of silicon-rhodamine with alkyl linkers attached to bulky apolar moieties had a limit of detection near 500 pM and a linear range spanning 5–100 nM for TA. We validated the assay on 18 distinct red wine samples, which showed high linearity (R2 = 0.92) with methylcellulose precipitation with no interference from anthocyanins. In conclusion, a novel assay was developed and validated that allows the sensitive and selective quantification of major astringency markers abundant in food and beverages.

•First evidence of quenching of silicon-rhodamines (SiR) by tannins•Tannins quench specific SiR conjugates with differential potency•Tannic acid had a detection limit of 500 pM and a linear range of 5–100 nM•Selectivity was evaluated on a diverse panel of phenolic compounds.•The assay was validated in diverse red wine samples

First evidence of quenching of silicon-rhodamines (SiR) by tannins

Tannins quench specific SiR conjugates with differential potency

Tannic acid had a detection limit of 500 pM and a linear range of 5–100 nM

Selectivity was evaluated on a diverse panel of phenolic compounds.

The assay was validated in diverse red wine samples