A research team from the Faculty of Horticulture is studying antioxidants in waste materials, particularly in woody plants. Plant waste can often contain higher amounts of selected antioxidants than common foods, and these substances can be used both in the food industry and in plant protection.
In their research, scientists have focused, for example, on grapevine wood, which contains the well-known antioxidant resveratrol. “Grapevine wood, specifically prunings, contains up to a thousand times more of this antioxidant than wine itself, and this material is regularly removed during vineyard maintenance. However, this antioxidant present in the wood can be extracted,” explained Ivo Soural from the Institute of Post-Harvest Technology of Horticultural Products at the Faculty of Horticulture, MENDELU. The team has also studied spruce knots as well as oak and black locust wood. “Wood knots are considered waste during wood processing. However, spruce knots are rich in lignans—again antioxidants—that can be used to enrich foods,” Soural added.
These compounds cannot be analyzed directly in wood biomass; they must first be transferred into a solution. Therefore, extracts are prepared from the wood and then analyzed. The measured values of individual or total antioxidants are subsequently recalculated to determine their concentration in the wood material. “Antioxidants often act as phytoalexins—substances that protect plants against attack. Our measurements partly confirm this: in slowly dried plant material, the amount of stilbenes increases over several months, whereas in material rapidly dried by lyophilization, these compounds are practically absent,” the scientist outlined.
Antioxidants therefore may not be useful only in the food industry but also in plant protection. “An interesting outcome is our patent for an antifungal spray based on a liquid extract from waste grapevine prunings. Extracts from grapevine wood help protect vines in vineyards against fungal pathogens causing powdery mildew and downy mildew,” said Soural.
Antioxidants can also be found in extracts from oak or black locust. “We can also look at commonly used cinnamon, which contains cinnamaldehyde. This compound gives cinnamon its characteristic aroma and flavor while also acting as an antioxidant. Ultimately, wood contains lignin—a structural polymer composed of various phenolic compounds that exhibit antioxidant properties,” Soural explained.
Although the use of wood extracts for food purposes may sound unusual, the opposite is true. “In general, it is possible in food production. It depends on the solvent used. If ethanol is used, there is usually no problem, but the use of methanol or another toxic solvent would be an issue. Of course, it also depends on dosage and quantity. Another aspect is legislation, as there is an effort to add something to food that is not traditionally considered food. However, if we stay with wood such as oak—commonly used for aging wine—there is no problem,” the scientist described.
Contact for further information:
Assoc. Prof. Ing. Ivo Soural, Ph.D.
+420 519 367 266
ivo.soural@mendelu.cz
Institute of Post-Harvest Technology of Horticultural Products, Faculty of Horticulture, MENDELU