Antioxidant-containing food helps to fight against free radicals that are known to produce reactive oxygen species (ROS) which, in turn, cause adverse biochemical reactions in human body. The antioxidant molecules that are particularly effective in combating ROS are known as polyphenols (PPh). When a free radical or ROS is formed in a given system, the nearby PPh molecule donates its own electron (or hydrogen atom) to repair the damage. As a result, the PPh molecule suffers a loss and it itself turns into a free radical (polyphenol radical (PPh.)). However, being relatively stable, it (PPh.) does not cause any harm to others. Measurements and analyses of the PPh. can, therefore, provide a better understanding of the antioxidant potential of the food in question. In this preliminary study, we measured free radicals (PPh.) in selected food powders that are rich in antioxidants. They are Acai, Camu, Beetroot, Cacao and Coffee. For free radical measurements, an electron spin resonance (ESR) (also known as electron paramagnetic resonance (EPR)), spectrometer was used. The g-values (spectral splitting factors) of the radicals of all antioxidant containing foods were obtained within the range from 2.0044 to 2.00578.