Antioxidant content

Fruits, vegetables, wine, tea and coffee contain  large amounts of reducing agents that protect their cell structure. The human body can only produce a limited number of antioxidants. Thus, its demands  are matched by consuming food. The amount of antioxidants in food can be measured using ESR.


(Belton et al. 2000)

Free radicals are highly reactive species that can alter proteins and DNA. To protect their biomolecular key points from radicals fruits and vegetables produce antioxidants. These react quickly with radicals inside the organism to prevent cellular damage.

The Antioxidant activity is a factor giving an idea of the health supporting effect. Antioxidant activity analysis starts with adding a known amount of stable radicals (e.g. TEMPOL) to the fruit or vegetable juice. The antioxidants will consume these radicals. The difference between its remaining and the initial concentration is proportional to the antioxidant activity.

Application example: polyphenolic activity in highbush blueberries

(Kroh et al. 2007)

Plants grow in accordance with their environment. Different plants may grow an infructescence that yields lush and healthy-looking fruit. Yet, their content of life-preserving substances may vary significantly depending on the location

Kroh et al. investigated this simple observation within one climatic region. Highbush blueberries (Vaccinium corymbosum L) were grown in different locations around Berlin. Plants grown on formerly used farmland were compared to others grown on forest soil. Two picking dates and different fertilization as well as ground covers were also tested.

Antioxidant activity analysis by ESR showed significant differences between different locations and times of harvest (see Fig. 1 & 3)


  • P. S. Belton, Ch. Chen, H.-R. Tang, L. H. Sutcliffe (2000) Journal of Agricultural and Food Chemistry 48, 5710 - 5714

  • L. W. Kroh, I. eichholz, S. Rohn, S. Huykens-Keil (2007) Journal of Applied Botany and Food Quality 81, 41 - 44

  • L. W. Kroh, B. Cämmerer (2006) European Food Research and Technology 223, 469 - 474