This study developed a film-shaped colorimetric polymer sensor read with a smartphone and tested it on 18 grape musts from French wineries against the flame atomic absorption results of a winery analytical laboratory. Reference results ranged from 0.41 to 6.08 ppm. The authors explain that winemakers monitor copper because it can cause reddish-brown “cupric crack” sediments, which are especially important in white wines.
Key numbers
- Copper in 18 grape musts by flame atomic absorption (reference method): 0.41 to 6.08 ppm; the highest value, 6.08 ppm, was a Provence sample (Table 1, p. 16060; abstract).
- Sensor-film results for the same musts, mean ± standard error of two replicates: 0.49 ± 0.03 to 5.85 ± 0.16 ppm; no significant difference between methods by Mann-Whitney test (Table 1 and Results, p. 16059 to 16060).
- Sensor limit of detection 0.08 ppm and limit of quantification 0.25 ppm (Results 3.4 and Conclusions, p. 16059 to 16060).
- The authors state that bentonite or gum arabic treatments used against cupric crack are not applicable above 1 mg/L copper (Introduction, p. 16055).
Methods (brief)
Musts collected in late summer 2021 were stabilized with sodium azide, frozen and analyzed by flame atomic absorption at a winery analysis laboratory. Sensor films containing a bicinchoninic acid-based monomer were dipped in the musts with an ascorbic acid buffer, photographed, and copper was estimated from the green color parameter against the reference calibration.
Evidence fitness
Supports copper occurrence in grape must at the winemaking stage and the comparison of a low-cost screening method with flame atomic absorption. It does not measure finished wine, which is the product consumed, and gives no intake or safety assessment.
Limitations
Eighteen musts from one analytical company’s clients are not a regional or national distribution. The sensor results were calibrated against the same reference data they were compared with. The authors suspect contamination during reference sample preparation for two samples, and units are reported as ppm without stating mass or volume basis.
Related evidence
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