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Postharvest drying maintains phenolic, flavonoid and gallotannin content of some cultivated African leafy vegetables

Maseko, I., Mabhaudhi, T., Ncube, B., Tesfay, S., Araya, H.T., Fessehazion, M.K., Chimonyo, V.G.P., Ndhlala, A.R., Du Plooy, C.P.
Scientia horticulturae 2019 v.255 pp. 70-76
Amaranthus cruentus, Beta vulgaris, Corchorus olitorius, Vigna unguiculata, drought, flavonoids, green leafy vegetables, irrigation rates, leaves, ovens, phenolic compounds, shade, solar drying, water requirement, water stress
The study investigated the effect of three irrigation regimes (30%, 60% and 100% of crop water requirement (ETc) and three drying (sun, oven, shade) methods on phenolic, flavonoids and gallatannin content of leafy vegetables. Corchorus olitorius grown under full irrigation and subjected to sun drying (100% ETc x sun) had significantly higher total phenolic content followed by medium stress subjected to shade drying (60% ETc x shade). Water stressed plants then shade and sun dried retained better gallotannins content than other treatments. Amaranthus cruentus grown under drought and shade dried (30% ETc x shade) retained better total phenolic, flavonoid and gallotannin content. Drought stress and sun drying also performed better for A. cruentus (30% ETc x sun) in terms of all phenolic components measured. In Vigna unguiculata, total phenolic content was high in water-stressed plants subjected to sun drying (30% ETc x sun), results were similar to well-watered plants subjected to shade drying (100% ETc x shade). Furthermore, sun drying retained better flavonoid and gallotannin content than shade and oven drying. In Beta vulgaris, well irrigated plants and shade or oven dried (100% ETc x shade or oven) performed similar to stressed plants subjected to sun drying (30% ETc x sun) in phenolics. Shade dried leaves had better flavonoid while drought stress had better gallotannins content compared to other treatments in B. vulgaris. The three leaf vegetables can grow under drought stress then sun and shade dried without compromising their phenolic content.