Effect of ozonated water treatment on inorganic components of Saperavi vines from the Bolnisi region of Georgia

In the world of winemaking, the journey from a tiny grape seed to a bottle of red wine is a complex biological process governed by the soil beneath the vines and the air above them. Vines are living things that draw nutrients from the ground, absorbing both the essential minerals they need to grow and the unwanted heavy metals that can sometimes lurk in the earth. These invisible elements travel up the trunk, into the leaves, and finally into the fruit, shaping the chemistry of the final drink. For centuries, farmers have used chemical sprays to protect these delicate plants from pests and disease, but these methods carry risks for the environment and the consumer. In recent years, a cleaner alternative has emerged: ozone. This is a form of oxygen that acts as a powerful disinfectant, capable of killing harmful bacteria and fungi without leaving toxic residues. While scientists have long known that ozone can clean the surface of grapes, a critical question remained unanswered: does this treatment change the invisible mineral makeup of the vine itself, or the heavy metals that might end up in the wine?

A team of researchers in Georgia set out to answer this question by studying the Saperavi grape, a variety famous in the Bolnisi region. They wanted to see what happens when grapevines are sprayed with water infused with ozone instead of traditional pesticides. Over two growing seasons, the team treated one section of a vineyard with this ozonated water, seven times from spring to autumn, while leaving a neighboring section untreated. They then carefully collected samples at every stage of the plant's life: the soil, the trunk, the leaves, the grape skins, the seeds, and the juice, eventually analyzing the finished wine. Their goal was to trace the path of inorganic elements—things like potassium, calcium, and iron, as well as heavy metals like lead and copper—moving from the ground up through the plant and into the glass.

The investigation revealed a clear pattern in how the ozone treatment altered the vine's chemistry. In the soil where the ozone was applied, the treatment seemed to break down organic complexes, making nutrients like phosphorus and nitrogen more available to the plant. However, as the researchers followed the elements up the vine, they found a general trend of reduction. The total amount of inorganic components decreased as they moved from the soil into the bunches, then into the leaves, skins, and seeds, and finally into the juice and wine. This decline was not uniform across all elements. While the levels of beneficial minerals like potassium and magnesium shifted, the most significant change occurred with heavy metals. The ozone treatment appeared to convert soluble forms of metals like iron and copper into insoluble solids, which could then be filtered out. As a result, the grapes and the resulting wine from the treated vines contained noticeably lower levels of these heavy metals compared to the untreated control group. For instance, the concentration of copper in the wine from the ozone-treated vines dropped significantly, reducing the risk of the wine becoming cloudy or unstable later on.

Despite these chemical shifts, the researchers found that the quality of the wine remained untouched. The changes in mineral content did not alter the taste, color, or aroma of the Saperavi. The organoleptic properties—the sensory experience of drinking the wine—were preserved, proving that the treatment could clean the plant without stripping it of its character. The study also noted that the ozone treatment helped reduce the need for sulfites, a common preservative in winemaking, by killing off unwanted bacteria and viruses more effectively. The process worked by slightly stressing the plant's skin cells, which stimulated a natural response that helped the plant manage its internal chemistry, but not enough to harm the fruit.

The findings suggest that spraying vines with ozonated water offers a dual benefit: it acts as a powerful shield against disease while simultaneously cleaning the plant of unwanted heavy metals. The treatment does not stop the vine from absorbing the nutrients it needs to thrive, but it does seem to filter out the toxic elements that might otherwise migrate from the soil into the final product. By the time the grapes are pressed and fermented, the wine from the treated vines is chemically cleaner, with fewer heavy metals and a lower risk of spoilage, yet it retains the full, rich profile that defines the Saperavi variety. This approach provides a way for winemakers to protect their crops and improve the stability of their wine without relying on harsh chemicals, ensuring that the final product is as pure as it is flavorful.