Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2012
Publication Date: 3/14/2012
Citation: Avena Bustillos, R.D., Du, W., Woods, R.D., Olson, D.A., Breksa III, A.P., Mchugh, T.H. 2012. Ultraviolet-B light treatment increases antioxidant capacity of carrot products. Journal of the Science of Food and Agriculture. 92(11):2341-2348.
Interpretive Summary: The results of the present study show that exposing sliced carrots to a form of ultraviolet light known as UV-B, found in sunshine, can boost the antioxidant activity of the colorful veggie. A low, 14-second dose of UV-B light can boost fresh, sliced carrots’ antioxidant capacity by about 3.2-fold. The dose is energy efficient and does not significantly heat or dry the crunchy, colorful veggie.
Technical Abstract: Abiotic stresses such as cutting and ultraviolet (UV) light exposure of plant cells triggers an increased activity response by phenylalanine ammonia-lyase (PAL) and chalcone synthase resulting in increased synthesis of phenolic compounds, mainly anthocyanins and flavonoids. This study investigated the effect of UV-B exposure at different dose levels and various cutting styles on total soluble phenolic compounds (TSP), antioxidant capacity (AC) and PAL activity of whole and peeled carrots, carrot peels, sliced, shredded, and baby carrots. TSP and AC increased by UV-B exposure for all carrot products mostly at the lowest doses applied, and these parameters were higher for shredded than sliced or peeled whole control carrots as an indication of increased wounding stresses. Otherwise, control baby carrots showed the lowest TSP, AC and PAL values due to removal of skin layers containing cells with higher enzyme activity, and loss of TSP by the washing step during its processing. Considering energy efficiency, reduction of exposure time, heating and evaporation effects, the best treatment to achieve a 3.2-fold AC increase in sliced carrots is an UV-B dose of 132 mJ/cm2, UV-B peak intensity of 18.7 mW/cm2 and residence time of 14 s for each face of the slices.