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Content of bioactive compounds in baby-leaves as affected by season and growth stage at harvest

Nordmark, L., Gertsson, U., Olsson, K., Olsson, M. E.
Acta horticulturae 2014 no.1040 pp. 201-206
Diplotaxis tenuifolia, Valerianella locusta, ascorbic acid, bioactive properties, developmental stages, glucosinolates, harvest date, high performance liquid chromatography, plant-based diet, preharvest treatment, secondary metabolites, vitamin content
Among the health benefits of a plant-based diet are some of the secondary metabolites. In this investigation on rucola (Diplotaxis tenuifolia) and cornsalad (Valerianella locusta) in field production in the northern hemisphere, the influence of preharvest factors at different harvest times (time of the season) and growth stages (development stage) were studied. The contents of vitamin C and glucosinolates were analysed by HPLC (high-performance liquid chromatography). Rucola harvested in June and in September, at stage III (older plants) had 5-14% higher content of vitamin C as compared to stage I (young plants). Corn salad harvested at stage I had 54-57% higher content of vitamin C as compared to stage II at June harvest time, whereas at August harvest time the content of vitamin C was 9% lower at stage I as compared to stage II. In rucola the content of vitamin C was 30-50% lower at late harvest time as compared to early harvest time, though in corn salad this was found only for the harvest stage I. The ratio between ascorbic acid and total vitamin C was higher at June than at September harvest time in rucola. The content of total glucosinolates in rucola were 28% lower at stage III in comparison to stage I at late harvest time whereas the content of total glucosinolates was 50-69% lower at June harvest time than at September harvest time. In conclusion, the results show high variation in nutrient quality and content of the compounds, depending on harvest time and growth stages. It is therefore highly important to obtain and improve know-how on preharvest factors as optimizing harvest time and growth stage in relation to nutrient quality of baby-leaf. Furthermore this result also shows the importance of describing preharvest treatment as background in discussion on healthful compounds.