Cryolite results unexpected

- Summer 1994 "Update" Newsletter Article -

Cryolite results unexpected
by Gwynn Sawyer Ostrom,
Research Associate, Viticulture and Enology Research Center
From CATI Publication #940701
Copyright © 1994. All rights reserved.
The hypothesis that some classes of surfactants exacerbate or increase the amount of fluoride residue found in wines has lead to an experiment supported by the California Agricultural Technology Institute in 1993.

Surfactants are materials used to aid in the dispersing or wetting of chemical onto the target when spraying. Some surfactants have “sticky” properties, and their use in combination with Kryocide was suspected of causing elevated fluoride levels in wines, since the Kryocide would adhere to the target better and longer.

This year’s research examined fluoride levels in wines made from Zinfandel and French Colombard grapes treated with Kryocide/surfactant combinations. Two types of surfactant “classes” were examined: spreaders, which serve to disperse the insecticide better over the surface of the grapevine leaves and clusters; and sticker-spreaders, which, in addition to spreading action, have polymers which cause the insecticide to adhere better to the surfaces being treated. The rates and timings are listed in Table 1.

Fluorides were analyzed in wines by the accepted ion selective electrode method. Results of this experiment confirm that the application of Kryocide can greatly affect fluoride levels in red and white wines (Figure 1).

Consistent with research performed from 1990-1993, wines made from untreated grapes of both varieties (T4) had significantly lower amounts of fluoride than wines made from grapes treated with Kryocide only (no surfactant) (T3). Fluoride levels in untreated wines ranged from 0.15 to 0.23 ppm, whereas fluoride levels in wines made from grapes treated with Kryocide ranged from 0.44 to 0.58 ppm

It is interesting that, for both Zinfandel and French Colombard, one of the treatments and the untreated control were not statistically different. For French Colombard, T1 and the untreated control had nearly the same fluoride level (0.21 vs. 0.23 ppm); for Zinfandel, T2 and the untreated control had similar fluoride levels (o.10 vs. 0.15). T3, in which Kryocide but no surfactant was applied, had significantly higher fluoride levels than any other treatment.

Contrary to what was originally thought, lower levels of fluoride were found in treatments with Kryocide/surfactant combinations this year. It is beyond the scope of this experiment to speculate on what factors may be causing these results. Due to the unexpected outcome, additional research is warranted to confirm this year’s results and to elucidate the role of surfactants with Kryocide on fluoride levels in wines.

{ page top }

{ CATI , VERC , VERC - Current Projects , "Update" Newsletter - 1994 }